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Title: Curiosities of Science, Past and Present

Author: John Timbs

Release date: March 17, 2015 [eBook #48516]

Language: English

Credits: Produced by Chris Curnow, Charlie Howard, and the Online
        Distributed Proofreading Team at http://www.pgdp.net (This
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*** START OF THE PROJECT GUTENBERG EBOOK CURIOSITIES OF SCIENCE, PAST AND PRESENT ***




Produced by Chris Curnow, Charlie Howard, and the Online
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file was produced from images generously made available
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    NEW WORK ON PAINTING.

    _Just ready, in small 8vo, with Frontispiece and Vignette_,

    PAINTING
    POPULARLY EXPLAINED;

    WITH
    The Practice of the Art,
    AND
    HISTORICAL NOTICES OF ITS PROGRESS.

    BY
    THOMAS J. GULLICK, PAINTER,
    AND
    JOHN TIMBS, F.S.A.


The plan of this work is thus sketched in the _Introduction_:

  “There have been in the history of Art, four grand styles of
  imitating Nature--Tempera, Encaustic, Fresco, and Oil. These,
  together with the minor modes of Painting, we propose arranging
  in something like chronological sequence; but our design being
  to offer an explanation of the Art derived from practical
  acquaintance, rather than attempt to give its history, we shall
  confine ourselves for the most part to so much only of the History
  of Painting as is necessary to elucidate the origin of the
  different practices which have obtained at different periods.”

  By this means, the Authors hope to produce a work which may be
  valuable to the Amateur, and interesting to the Connoisseur, the
  Artist, and the General Reader.


LONDON: KENT & CO. (LATE BOGUE), FLEET STREET.

[Illustration: MOUTH OF THE GREAT ROSSE TELESCOPE, AT PARSONSTOWN.

FROM A PHOTOGRAPH.]




    Things not generally Known
    Familiarly Explained.


    CURIOSITIES OF SCIENCE,

    Past and Present.

    A BOOK FOR OLD AND YOUNG.


    BY JOHN TIMBS, F.S.A.

    AUTHOR OF THINGS NOT GENERALLY KNOWN; AND EDITOR OF THE
    YEAR-BOOK OF FACTS.

    [Illustration: Model of the Safety-Lamp, made by Sir Humphry
       Davy’s own hands; in the possession of the Royal Society.]


    LONDON:
    KENT AND CO. (LATE BOGUE), FLEET STREET.
    MDCCCLVIII.




    _The Author reserves the right of authorising a Translation of
    this Work._


    LONDON:
    PRINTED BY LEVEY, ROBSON, AND FRANKLYN,
    Great New Street and Fetter Lane.




GENTLE READER,

The volume of “CURIOSITIES” which I here present to your notice is a
portion of the result of a long course of reading, observation, and
research, necessary for the compilation of thirty volumes of “Arcana
of Science” and “Year-Book of Facts,” published from 1828 to 1858.
Throughout this period--nearly half of the Psalmist’s “days of our
years”--I have been blessed with health and strength to produce these
volumes, year by year (with one exception), upon the appointed day; and
this with unbroken attention to periodical duties, frequently rendered
harassing or ungenial. Nevertheless, during these three decades I
have found my account in the increasing approbation of the reading
public, which has been so largely extended to the series of “THINGS
NOT GENERALLY KNOWN,” of which the present volume of “CURIOSITIES OF
SCIENCE” is an instalment. I need scarcely add, that in its progressive
preparation I have endeavoured to compare, weigh, and consider,
the contents, so as to combine the experience of the Past with the
advantages of the Present.

In these days of universal attainments, when Science becomes not
merely a luxury to the rich, but bread to the poor, and when the
very amusements as well as the conveniences of life have taken a
scientific colour, it is reasonable to hope that the present volume
may be acceptable to a large class of seekers after “things not
generally known.” For this purpose, I have aimed at soundness as well
as popularity; although, for myself, I can claim little beyond being
one of those industrious “ants of science” who garner facts, and by
selection and comparison adapt them for a wider circle of readers
than they were originally expected to reach. In each case, as far as
possible, these “CURIOSITIES” bear the mint-mark of authority; and in
the living list are prominent the names of Humboldt and Herschel, Airy
and Whewell, Faraday, Brewster, Owen, and Agassiz, Maury, Wheatstone,
and Hunt, from whose writings and researches the following pages are
frequently enriched.

The sciences here illustrated are, in the main, Astronomy and
Meteorology; Geology and Paleontology; Physical Geography; Sound,
Light, and Heat; Magnetism and Electricity,--the latter with special
attention to the great marvel of our times, the Electro-magnetic
Telegraph. I hope, at no very distant period, to extend the
“CURIOSITIES” to another volume, to include branches of Natural and
Experimental Science which are not here presented.

            I. T.
    _November 1858._




CONTENTS.


                                          PAGE
    INTRODUCTORY                          1-10

    PHYSICAL PHENOMENA                   11-26

    SOUND AND LIGHT                      27-53

    ASTRONOMY                           54-103

    GEOLOGY AND PALEONTOLOGY           104-145

    METEOROLOGICAL PHENOMENA           146-169

    PHYSICAL GEOGRAPHY OF THE SEA      170-192

    MAGNETISM AND ELECTRICITY          193-219

    THE ELECTRIC TELEGRAPH             220-228

    MISCELLANEA                        229-241




The Frontispiece.

THE GREAT ROSSE TELESCOPE.


The originator and architect of this magnificent instrument had long
been distinguished in scientific research as Lord Oxmantown; and
may be considered to have gracefully commemorated his succession to
the Earldom of Rosse, and his Presidency of the Royal Society, by
the completion of this marvellous work, with which his name will be
hereafter indissolubly associated.

The Great Reflecting Telescope at Birr Castle (of which the
Frontispiece represents a portion[1]) will be found fully described at
pp. 96-99 of the present volume of _Curiosities of Science_.

This matchless instrument has already disclosed “forms of stellar
arrangement indicating modes of dynamic action never before
contemplated in celestial mechanics.” “In these departments of
research,--the examination of the configurations of nebulæ, and the
resolution of nebulæ into stars (says the Rev. Dr. Scoresby),--the
six-feet speculum has had its grandest triumphs, and the noble
artificer and observer the highest rewards of his talents and
enterprise. Altogether, the quantity of work done during a period of
about seven years--including a winter when a noble philanthropy for
a starving population absorbed the keenest interests of science--has
been decidedly great; and the new knowledge acquired concerning the
handiwork of the great Creator amply satisfying of even sanguine
expectation.”




The Vignette.

SIR HUMPHRY DAVY’S OWN MODEL OF HIS SAFETY-LAMP.


Of the several contrivances which have been proposed for safely
lighting coal-mines subject to the visitation of fire-damp, or
carburetted hydrogen, the Safety-Lamp of Sir Humphry Davy is the only
one which has ever been judged safe, and been extensively employed. The
inventor first turned his attention to the subject in 1815, when Davy
began a minute chemical examination of fire-damp, and found that it
required an admixture of a large quantity of atmospheric air to render
it explosive. He then ascertained that explosions of inflammable gases
were incapable of being passed through long narrow metallic tubes, and
that this principle of security was still obtained by diminishing their
length and increasing their number. This fact led to trials upon sieves
made of wire-gauze; when Davy found that if a piece of wire-gauze was
held over the flame of a lamp, or of coal-gas, it prevented the flame
from passing; and he ascertained that a flame confined in a cylinder of
very fine wire-gauze did not explode even in a mixture of oxygen and
hydrogen, but that the gases burnt in it with great vivacity.

These experiments served as the basis of the Safety-Lamp. The apertures
in the gauze, Davy tells us in his work on the subject, should not
be more than 1/22d of an inch square. The lamp is screwed on to the
bottom of the wire-gauze cylinder. When it is lighted, and gradually
introduced into an atmosphere mixed with fire-damp, the size and length
of the flame are first increased. When the inflammable gas forms as
much as 1/12th of the volume of air, the cylinder becomes filled with a
feeble blue flame, within which the flame of the wick burns brightly,
and the light of the wick continues till the fire-damp increases to
1/6th or 1/5th; it is then lost in the flame of the fire-damp, which
now fills the cylinder with a pretty strong light; and when the foul
air constitutes one-third of the atmosphere it is no longer fit for
respiration,--and this ought to be a signal to the miner to leave that
part of the workings.

Sir Humphry Davy presented his first communication respecting his
discovery of the Safety-Lamp to the Royal Society in 1815. This was
followed by a series of papers remarkable for their simplicity and
clearness, crowned by that read on the 11th of January 1816, when the
principle of the Safety-Lamp was announced, and Sir Humphry presented
to the Society a model made by his own hands, which is to this day
preserved in the collection of the Royal Society at Burlington House.
From this interesting memorial the Vignette has been sketched.

There have been several modifications of the Safety-Lamp, and the merit
of the discovery has been claimed by others, among whom was Mr. George
Stephenson; but the question was set at rest forty-one years since by
an examination,--attested by Sir Joseph Banks, P.R.S., Mr. Brande, Mr.
Hatchett, and Dr. Wollaston,--and awarding the independent merit to
Davy.

A more substantial, though not a more honourable, testimony of approval
was given by the coal-owners, who subscribed 2500_l._ to purchase a
superb service of plate, which was suitably inscribed and presented to
Davy.[2]

Meanwhile the Report by the Parliamentary Committee “cannot admit that
the experiments (made with the Lamp) have any tendency to detract from
the character of Sir Humphry Davy, or to disparage the fair value
placed by himself upon his invention. The improvements are probably
those which longer life and additional facts would have induced him to
contemplate as desirable, and of which, had he not been the inventor,
he might have become the patron.”

The principle of the invention may be thus summed up. In the
Safety-Lamp, the mixture of the fire-damp and atmospheric air within
the cage of wire-gauze explodes upon coming in contact with the flame;
but the combustion cannot pass through the wire-gauze, and being there
imprisoned, cannot impart to the explosive atmosphere of the mine any
of its force. This effect has been erroneously attributed to a cooling
influence of the metal.

Professor Playfair has eloquently described the Safety-Lamp of Davy as
a present from philosophy to the arts; a discovery in no degree the
effect of accident or chance, but the result of patient and enlightened
research, and strongly exemplifying the great use of an immediate and
constant appeal to experiment. After characterising the invention as
the _shutting-up in a net of the most slender texture_ a most violent
and irresistible force, and a power that in its tremendous effects
seems to emulate the lightning and the earthquake, Professor Playfair
thus concludes: “When to this we add the beneficial consequences, and
the saving of the lives of men, and consider that the effects are to
remain as long as coal continues to be dug from the bowels of the
earth, it may be fairly said that there is hardly in the whole compass
of art or science a single invention of which one would rather wish
to be the author.... This,” says Professor Playfair, “is exactly such
a case as we should choose to place before Bacon, were he to revisit
the earth; in order to give him, in a small compass, an idea of the
advancement which philosophy has made since the time when he had
pointed out to her the route which she ought to pursue.”




CURIOSITIES OF SCIENCE.




Introductory.


SCIENCE OF THE ANCIENT WORLD.

In every province of human knowledge where we now possess a careful
and coherent interpretation of nature, men began by attempting in
bold flights to leap from obvious facts to the highest point of
generality--to some wide and simple principle which after-ages had to
reject. Thus, from the facts that all bodies are hot or cold, moist or
dry, they leapt at once to the doctrine that the world is constituted
of four elements--earth, air, fire, water; from the fact that the
heavenly bodies circle the sky in courses which occur again and again,
they at once asserted that they move in exact circles, with an exactly
uniform motion; from the fact that heavy bodies fall through the air
somewhat faster than light ones, it was assumed that all bodies fall
quickly or slowly exactly in proportion to their weight; from the fact
that the magnet attracts iron, and that this force of attraction is
capable of increase, it was inferred that a perfect magnet would have
an irresistible force of attraction, and that the magnetic pole of
the earth would draw the nails out of a ship’s bottom which came near
it; from the fact that some of the finest quartz crystals are found
among the snows of the Alps, it was inferred that the crystallisation
of gems is the result of intense and long-continued cold: and so on
in innumerable instances. Such anticipations as these constituted
the basis of almost all the science of the ancient world; for such
principles being so assumed, consequences were drawn from them with
great ingenuity, and systems of such deductions stood in the place of
science.--_Edinburgh Review_, No. 216.


SCIENCE AT OXFORD AND CAMBRIDGE.

The earliest science of a decidedly English school is due, for the most
part, to the University of Oxford, and specially to Merton College,--a
foundation of which Wood remarks, that there was no other for two
centuries, either in Oxford or Paris, which could at all come near it
in the cultivation of the sciences. But he goes on to say that large
chests full of the writers of this college were allowed to remain
untouched by their successors for fear of the magic which was supposed
to be contained in them. Nevertheless, it is not difficult to trace
the liberalising effect of scientific study upon the University in
general, and Merton College in particular; and it must be remembered
that to the cultivation of the mind at Oxford we owe almost all the
literary celebrity of the middle ages. In this period the University of
Cambridge appears to have acquired no scientific distinction. Taking
as a test the acquisition of celebrity on the continent, we find that
Bacon, Sacrobosco, Greathead, Estwood, &c. were all of Oxford. The
latter University had its morning of splendour while Cambridge was
comparatively unknown; it had also its noonday, illustrated by such men
as Briggs, Wren, Wallis, Halley, and Bradley.

The age of science at Cambridge may be said to have begun with Francis
Bacon; and but that we think much of the difference between him and
his celebrated namesake lies more in time and circumstances than in
talents or feelings, we would rather date from 1600 with the former
than from 1250 with the latter. Praise or blame on either side is out
of the question, seeing that the earlier foundation of Oxford, and its
superiority in pecuniary means, rendered all that took place highly
probable; and we are in a great measure indebted for the liberty of
writing our thoughts, to the cultivation of the liberalising sciences
at Oxford in the dark ages.

With regard to the University of Cambridge, for a long time there
hardly existed the materials of any proper instruction, even to the
extent of pointing out what books should be read by a student desirous
of cultivating astronomy.


PLATO’S SURVEY OF THE SCIENCES.

  Plato, like Francis Bacon, took a review of the sciences of his
  time: he enumerates arithmetic and plane geometry, treated as
  collections of abstract and permanent truths; solid geometry, which
  he “notes as deficient” in his time, although in fact he and his
  school were in possession of the doctrine of the “five regular
  solids;” astronomy, in which he demands a science which should
  be elevated above the mere knowledge of phenomena. The visible
  appearances of the heavens only suggest the problems with which
  true astronomy deals; as beautiful geometrical diagrams do not
  prove, but only suggest geometrical propositions. Finally, Plato
  notices the subject of harmonics, in which he requires a science
  which shall deal with truths more exact than the ear can establish,
  as in astronomy he requires truths more exact than the eye can
  assure us of.

  In a subsequent paper Plato speaks of _Dialectic_ as a still
  higher element of a philosophical education, fitted to lead men
  to the knowledge of real existences and of the supreme good. Here
  he describes dialectic by its objects and purpose. In other places
  dialectic is spoken of as a method or process of analysis; as in
  the _Phædrus_, where Socrates describes a good dialectician as one
  who can divide a subject according to its natural members, and not
  miss the joint, like a bad carver. Xenophon says that Socrates
  derived _dialectic_ from a term implying to _divide a subject into
  parts_, which Mr. Grote thinks unsatisfactory as an etymology, but
  which has indicated a practical connection in the Socratic school.
  The result seems to be that Plato did not establish any method of
  analysis of a subject as his dialectic; but he conceived that the
  analytical habits formed by the comprehensive study of the exact
  sciences, and sharpened by the practice of dialogue, would lead his
  students to the knowledge of first principles.--_Dr. Whewell._


FOLLY OF ATHEISM.

Morphology, in natural science, teaches us that the whole animal
and vegetable creation is formed upon certain fundamental types
and patterns, which can be traced under various modifications and
transformations through all the rich variety of things apparently of
most dissimilar build. But here and there a scientific person takes
it into his foolish head that there may be a set of moulds without
a moulder, a calculated gradation of forms without a calculator, an
ordered world without an ordering God. Now, this atheistical science
conveys about as much meaning as suicidal life: for science is possible
only where there are ideas, and ideas are only possible where there is
mind, and minds are the offspring of God; and atheism itself is not
merely ignorance and stupidity,--it is the purely nonsensical and the
unintelligible.--_Professor Blackie_; _Edinburgh Essays_, 1856.


THE ART OF OBSERVATION.

To observe properly in the very simplest of the physical sciences
requires a long and severe training. No one knows this so feelingly
as the great discoverer. Faraday once said, that he always doubts his
own observations. Mitscherlich on one occasion remarked to a man of
science that it takes fourteen years to discover and establish a single
new fact in chemistry. An enthusiastic student one day betook himself
to Baron Cuvier with the exhibition of a new organ--a muscle which he
supposed himself to have discovered in the body of some living creature
or other; but the experienced and sagacious naturalist kindly bade the
young man return to him with the same discovery in six months. The
Baron would not even listen to the student’s demonstration, nor examine
his dissection, till the eager and youthful discoverer had hung over
the object of inquiry for half a year; and yet that object was a mere
thing of the senses.--_North-British Review_, No. 18.


MUTUAL RELATIONS OF PHENOMENA.

In the observation of a phenomenon which at first sight appears to
be wholly isolated, how often may be concealed the germ of a great
discovery! Thus, when Galvani first stimulated the nervous fibre of
the frog by the accidental contact of two heterogeneous metals, his
contemporaries could never have anticipated that the action of the
voltaic pile would discover to us in the alkalies metals of a silver
lustre, so light as to swim on water, and eminently inflammable; or
that it would become a powerful instrument of chemical analysis, and at
the same time a thermoscope and a magnet. When Huyghens first observed,
in 1678, the phenomenon of the polarisation of light, exhibited in the
difference between two rays into which a pencil of light divides itself
in passing through a doubly refracting crystal, it could not have been
foreseen that a century and a half later the great philosopher Arago
would, by his discovery of _chromatic polarisation_, be led to discern,
by means of a small fragment of Iceland spar, whether solar light
emanates from a solid body or a gaseous covering; or whether comets
transmit light directly, or merely by reflection.--_Humboldt’s Cosmos_,
vol. i.


PRACTICAL RESULTS OF THEORETICAL SCIENCE.

What are the great wonders, the great sources of man’s material
strength, wealth, and comfort in modern times? The Railway, with its
mile-long trains of men and merchandise, moving with the velocity of
the wind, and darting over chasms a thousand feet wide; the Electric
Telegraph, along which man’s thoughts travel with the velocity of
light, and girdle the earth more quickly than Puck’s promise to his
master; the contrivance by which the Magnet, in the very middle of
a strip of iron, is still true to the distant pole, and remains a
faithful guide to the mariner; the Electrotype process, by which a
metallic model of any given object, unerringly exact, grows into
being like a flower. Now, all these wonders are the result of recent
and profound discoveries in theoretical science. The Locomotive
Steam-engine, and the Steam-engine in all its other wonderful and
invaluable applications, derives its efficacy from the discoveries, by
Watt and others, of the laws of steam. The Railway Bridge is not made
strong by mere accumulation of materials, but by the most exact and
careful scientific examination of the means of giving the requisite
strength to every part, as in the great example of Mr. Stephenson’s
Britannia Bridge over the Menai Strait. The Correction of the Magnetic
Needle in iron ships it would have been impossible for Mr. Airy to
secure without a complete theoretical knowledge of the laws of
Magnetism. The Electric Telegraph and the Electrotype process include
in their principles and mechanism the most complete and subtle results
of electrical and magnetical theory.--_Edinburgh Review_, No. 216.


PERPETUITY OF IMPROVEMENT.

In the progress of society all great and real improvements are
perpetuated: the same corn which, four thousand years ago, was raised
from an improved grass by an inventor worshiped for two thousand years
in the ancient world under the name of Ceres, still forms the principal
food of mankind; and the potato, perhaps the greatest benefit that the
old has derived from the new world, is spreading over Europe, and will
continue to nourish an extensive population when the name of the race
by whom it was first cultivated in South America is forgotten.--_Sir H.
Davy._


THE EARLIEST ENGLISH SCIENTIFIC TREATISE.

Geoffrey Chaucer, the poet, wrote a treatise on the Astrolabe for his
son, which is the earliest English treatise we have met with on any
scientific subject. It was not completed; and the apologies which
Chaucer makes to his own child for writing in English are curious;
while his inference that his son should therefore “pray God save the
king that is lord of this language,” is at least as loyal as logical.


PHILOSOPHERS’ FALSE ESTIMATES OF THEIR OWN LABOURS.

Galileo was confident that the most important part of his contributions
to the knowledge of the solar system was his Theory of the Tides--a
theory which all succeeding astronomers have rejected as utterly
baseless and untenable. Descartes probably placed far above his
beautiful explanation of the rainbow, his _à priori_ theory of the
existence of the vortices which caused the motion of the planets and
satellites. Newton perhaps considered as one of the best parts of his
optical researches his explanation of the natural colour of bodies,
which succeeding optical philosophers have had to reject; and he
certainly held very strongly the necessity of a material cause for
gravity, which his disciples have disregarded. Davy looked for his
greatest triumph in the application of his discoveries to prevent
the copper bottoms of ships from being corroded. And so in other
matters.--_Edinburgh Review_, No. 216.


RELICS OF GENIUS.

Professor George Wilson, in a lecture to the Scottish Society of
Arts, says: “The spectacle of these things ministers only to the
good impulses of humanity. Isaac Newton’s telescope at the Royal
Society of London; Otto Guericke’s air-pump in the Library at Berlin;
James Watt’s repaired Newcomen steam-engine in the Natural-Philosophy
class-room of the College at Glasgow; Fahrenheit’s thermometer in
the corresponding class-room of the University of Edinburgh; Sir H.
Davy’s great voltaic battery at the Royal Institution, London, and
his safety-lamp at the Royal Society; Joseph Black’s pneumatic trough
in Dr. Gregory’s possession; the first wire which Faraday made rotate
electro-magnetically, at St. Bartholomew’s Hospital; Dalton’s atomic
models at Manchester; and Kemp’s liquefied gases in the Industrial
Museum of Scotland,--are alike personal relics, historical monuments,
and objects of instruction, which grow more and more precious every
year, and of which we never can have too many.”


THE ROYAL SOCIETY: THE NATURAL AND SUPERNATURAL.

The Royal Society was formed with the avowed object of increasing
knowledge by direct experiment; and it is worthy of remark, that the
charter granted by Charles II. to this celebrated institution declares
that its object is the extension of natural knowledge, as opposed to
that which is supernatural.

Dr. Paris (_Life of Sir H. Davy_, vol. ii. p. 178) says: “The charter
of the Royal Society states that it was established for the improvement
of _natural_ science. This epithet _natural_ was originally intended to
imply a meaning, of which very few persons, I believe, are aware. At
the period of the establishment of the society, the arts of witchcraft
and divination were very extensively encouraged; and the word _natural_
was therefore introduced in contradistinction to _supernatural_.”


THE PHILOSOPHER BOYLE.

After the death of Bacon, one of the most distinguished Englishmen
was certainly Robert Boyle, who, if compared with his contemporaries,
may be said to rank immediately below Newton, though of course very
inferior to him as an original thinker. Boyle was the first who
instituted exact experiments into the relation between colour and heat;
and by this means not only ascertained some very important facts, but
laid a foundation for that union between optics and thermotics, which,
though not yet completed, now merely waits for some great philosopher
to strike out a generalisation large enough to cover both, and thus
fuse the two sciences into a single study. It is also to Boyle, more
than to any other Englishman, that we owe the science of hydrostatics
in the state in which we now possess it.[3] He is also the original
discoverer of that beautiful law, so fertile in valuable results,
according to which the elasticity of air varies as its density. And,
in the opinion of one of the most eminent modern naturalists, it was
Boyle who opened up those chemical inquiries which went on accumulating
until, a century later, they supplied the means by which Lavoisier and
his contemporaries fixed the real basis of chemistry, and enabled it
for the first time to take its proper stand among those sciences that
deal with the external world.--_Buckle’s History of Civilization_, vol.
i.


SIR ISAAC NEWTON’S ROOMS AND LABORATORY IN TRINITY COLLEGE, CAMBRIDGE.

Of the rooms occupied by Newton during his early residence at
Cambridge, it is now difficult to settle the locality. The chamber
allotted to him as Fellow, in 1667, was “the Spiritual Chamber,”
conjectured to have been the ground-room, next the chapel, but it is
not certain that he resided there. The rooms in which he lived from
1682 till he left Cambridge, are in the north-east corner of the great
court, on the first floor, on the right or north of the gateway or
principal entrance to the college. His laboratory, as Dr. Humphrey
Newton tell us, was “on the left end of the garden, near the east end
of the chapel; and his telescope (refracting) was five feet long, and
placed at the head of the stairs, going down into the garden.”[4] The
east side of Newton’s rooms has been altered within the last fifty
years: Professor Sedgwick, who came up to college in 1804, recollects a
wooden room, supported on an arcade, shown in Loggan’s view, in place
of which arcade is now a wooden wall and brick chimney.

  Dr. Humphrey Newton relates that in college Sir Isaac very rarely
  went to bed till two or three o’clock in the morning, sometimes
  not till five or six, especially at spring and fall of the leaf,
  when he used to employ about six weeks in his laboratory, the
  fire scarcely going out either night or day; he sitting up one
  night, and Humphrey another, till he had finished his chemical
  experiments. Dr. Newton describes the laboratory as “well furnished
  with chymical materials, as bodyes, receivers, heads, crucibles,
  &c., which was made very little use of, ye crucibles excepted,
  in which he fused his metals: he would sometimes, though very
  seldom, look into an old mouldy book, which lay in his laboratory;
  I think it was titled _Agricola de Metallis_, the transmuting of
  metals being his chief design, for which purpose antimony was a
  great ingredient.” “His brick furnaces, _pro re nata_, he made and
  altered himself without troubling a bricklayer.” “What observations
  he might make with his telescope, I know not, but several of his
  observations about comets and the planets may be found scattered
  here and there in a book intitled _The Elements of Astronomy_, by
  Dr. David Gregory.”[5]


NEWTON’S “APPLE-TREE.”

Curious and manifold as are the trees associated with the great names
of their planters, or those who have sojourned in their shade, the
Tree which, by the falling of its fruit, suggested to Newton the idea
of Gravity, is of paramount interest. It appears that, in the autumn
of 1665, Newton left his college at Cambridge for his paternal home
at Woolsthorpe. “When sitting alone in the garden,” says Sir David
Brewster, “and speculating on the power of gravity, it occurred to him,
that as the same power by which the apple fell to the ground was not
sensibly diminished at the greatest distance from the centre of the
earth to which we can reach, neither at the summits of the loftiest
spires, nor on the tops of the highest mountains, it might extend to
the moon and retain her in her orbit, in the same manner as it bends
into a curve a stone or a cannon-ball when projected in a straight line
from the surface of the earth.”--_Life of Newton_, vol. i. p. 26. Sir
David Brewster notes, that neither Pemberton nor Whiston, who received
from Newton himself his first ideas of gravity, records this story of
the falling apple. It was mentioned, however, to Voltaire by Catherine
Barton, Newton’s niece; and to Mr. Green by Martin Folkes, President
of the Royal Society. Sir David Brewster saw the reputed apple-tree in
1814, and brought away a portion of one of its roots. The tree was so
much decayed that it was cut down in 1820, and the wood of it carefully
preserved by Mr. Turnor, of Stoke Rocheford.

  De Morgan (in _Notes and Queries_, 2d series, No. 139, p. 169)
  questions whether the fruit was an apple, and maintains that the
  anecdote rests upon very slight authority; more especially as
  the idea had for many years been floating before the minds of
  physical inquirers; although Newton cleared away the confusions and
  difficulties which prevented very able men from proceeding beyond
  conjecture, and by this means established _universal_ gravitation.


NEWTON’S “PRINCIPIA.”

“It may be justly said,” observes Halley, “that so many and so valuable
philosophical truths as are herein discovered and put past dispute
were never yet owing to the capacity and industry of any one man.”
“The importance and generality of the discoveries,” says Laplace, “and
the immense number of original and profound views, which have been the
germ of the most brilliant theories of the philosophers of this (18th)
century, and all presented with much elegance, will ensure to the work
on the _Mathematical Principles of Natural Philosophy_ a preëminence
above all the other productions of human genius.”


DESCARTES’ LABOURS IN PHYSICS.

The most profound among the many eminent thinkers France has produced,
is Réné Descartes, of whom the least that can be said is, that he
effected a revolution more decisive than has ever been brought about
by any other single mind; that he was the first who successfully
applied algebra to geometry; that he pointed out the important law of
the sines; that in an age in which optical instruments were extremely
imperfect, he discovered the changes to which light is subjected in
the eye by the crystalline lens; that he directed attention to the
consequences resulting from the weight of the atmosphere; and that he
moreover detected the causes of the rainbow. At the same time, and
as if to combine the most varied forms of excellence, he is not only
allowed to be the first geometrician of the age, but by the clearness
and admirable precision of his style, he became one of the founders
of French prose. And, although he was constantly engaged in those
lofty inquiries into the nature of the human mind, which can never
be studied without wonder, he combined with them a long course of
laborious experiment upon the animal frame, which raised him to the
highest rank among the anatomists of his time. The great discovery
made by Harvey of the Circulation of the Blood was neglected by most
of his contemporaries; but it was at once recognised by Descartes, who
made it the basis of the physiological part of his work on man. He was
likewise the discoverer of the lacteals by Aselli, which, like every
great truth yet laid before the world, was at its first appearance,
not only disbelieved, but covered with ridicule.--_Buckle’s History of
Civilization_, vol. i.


CONIC SECTIONS.

If a cone or sugar-loaf be cut through in certain directions, we shall
obtain figures which are termed conic sections: thus, if we cut through
a sugar-loaf parallel to its base or bottom, the outline or edge of the
loaf where it is cut will be _a circle_. If the cut is made so as to
slant, and not be parallel to the base of the loaf, the outline is an
_ellipse_, provided the cut goes quite through the sides of the loaf
all round; but if it goes slanting, and parallel to the line of the
loaf’s side, the outline is a _parabola_, a conic section or curve,
which is distinguished by characteristic properties, every point of it
bearing a certain fixed relation to a certain point within it, as the
circle does to its centre.--_Dr. Paris’s Notes to Philosophy in Sport,
&c._


POWER OF COMPUTATION.

The higher class of mathematicians, at the end of the seventeenth
century, had become excellent computers, particularly in England,
of which Wallis, Newton, Halley, the Gregorys, and De Moivre, are
splendid examples. Before results of extreme exactness had become
quite familiar, there was a gratifying sense of power in bringing out
the new methods. Newton, in one of his letters to Oldenburg, says
that he was at one time too much attached to such things, and that
he should be ashamed to say to what number of figures he was in the
habit of carrying his results. The growth of power of computation on
the Continent did not, however, keep pace with that of the same in
England. In 1696, De Laguy, a well-known writer on algebra, and a
member of the Academy of Sciences, said that the most skilful computer
could not, in less than a month, find within a unit the cube root of
696536483318640035073641037.--_De Morgan._


“THE SCIENCE OF THE COSMOS.”

Humboldt, characterises this “uncommon but definite expression” as the
treating of “the assemblage of all things with which space is filled,
from the remotest nebulæ to the climatic distribution of those delicate
tissues of vegetable matter which spread a variegated covering over the
surface of our rocks.” The word _cosmos_, which primitively, in the
Homeric ages, indicated an idea of order and harmony, was subsequently
adopted in scientific language, where it was gradually applied to the
order observed in the movements of the heavenly bodies; to the whole
universe; and then finally to the world in which this harmony was
reflected to us.




Physical Phenomena.


ALL THE WORLD IN MOTION.

Humboldt, in his _Cosmos_,[6] gives the following beautiful
illustrative proofs of this phenomenon:

  If, for a moment, we imagine the acuteness of our senses
  preternaturally heightened to the extreme limits of telescopic
  vision, and bring together events separated by wide intervals of
  time, the apparent repose which reigns in space will suddenly
  vanish; countless stars will be seen moving in groups in various
  directions; nebulæ wandering, condensing, and dissolving like
  cosmical clouds; the milky way breaking up in parts, and its
  veil rent asunder. In every point of the celestial vault we
  shall recognise the dominion of progressive movement, as on the
  surface of the earth where vegetation is constantly putting forth
  its leaves and buds, and unfolding its blossoms. The celebrated
  Spanish botanist, Cavanilles, first conceived the possibility of
  “seeing grass grow,” by placing the horizontal micrometer wire
  of a telescope, with a high magnifying power, at one time on the
  point of a bamboo shoot, and at another on the rapidly unfolding
  flowering stem of an American aloe; precisely as the astronomer
  places the cross of wires on a culminating star. Throughout the
  whole life of physical nature--in the organic as in the sidereal
  world--existence, preservation, production, and development, are
  alike associated with motion as their essential condition.


THE AXIS OF ROTATION.

It is remarkable as a mechanical fact, that nothing is so permanent in
nature as the Axis of Rotation of any thing which is rapidly whirled.
We have examples of this in every-day practice. The first is the
motion of _a boy’s hoop_. What keeps the hoop from falling?--It is its
rotation, which is one of the most complicated subjects in mechanics.

Another thing pertinent to this question is, _the motion of a quoit_.
Every body who ever threw a quoit knows that to make it preserve its
position as it goes through the air, it is necessary to give it a
whirling motion. It will be seen that while whirling, it preserves its
plane, whatever the position of the plane may be, and however it may
be inclined to the direction in which the quoit travels. Now, this has
greater analogy with the motion of the earth than any thing else.

Another illustration is _the motion of a spinning top_. The greatest
mathematician of the last century, the celebrated Euler, has written
a whole book on the motion of a top, and his Latin treatise _De motu
Turbinis_ is one of the most remarkable books on mechanics. The motion
of a top is a matter of the greatest importance; it is applicable
to the elucidation of some of the greatest phenomena of nature. In
all these instances there is this wonderful tendency in rotation to
preserve the axis of rotation unaltered.--_Prof. Airy’s Lect. on
Astronomy._


THE EARTH’S ANNUAL MOTION.

In conformity with the Copernican view of our system, we must learn to
look upon the sun as the comparatively motionless centre about which
the earth performs an annual elliptic orbit of the dimensions and
excentricity, and with a velocity, regulated according to a certain
assigned law; the sun occupying one of the foci of the ellipse, and
from that station quietly disseminating on all sides its light and
heat; while the earth travelling round it, and presenting itself
differently to it at different times of the year and day, passes
through the varieties of day and night, summer and winter, which we
enjoy.--_Sir John Herschel’s Outlines of Astronomy._

Laplace has shown that the length of the day has not varied the
hundredth part of a second since the observations of Hipparchus, 2000
years ago.


STABILITY OF THE OCEAN.

In submitting this question to analysis, Laplace found that the
_equilibrium of the ocean is stable if its density is less than
the mean density of the earth_, and that its equilibrium cannot be
subverted unless these two densities are equal, or that of the earth
less than that of its waters. The experiments on the attraction of
Schehallien and Mont Cenis, and those made by Cavendish, Reich, and
Baily, with balls of lead, demonstrate that the mean density of the
earth is at least _five_ times that of water, and hence the stability
of the ocean is placed beyond a doubt. As the seas, therefore, have at
one time covered continents which are now raised above their level,
we must seek for some other cause of it than any want of stability in
the equilibrium of the ocean. How beautifully does this conclusion
illustrate the language of Scripture, “Hitherto shalt thou come, but no
further”! (_Job_ xxxviii. 11.)


COMPRESSION OF BODIES.

Sir John Leslie observes, that _air compressed_ into the fiftieth
part of its volume has its elasticity fifty times augmented: if it
continued to contract at that rate, it would, from its own incumbent
weight, acquire the density of water at the depth of thirty-four
miles. But water itself would have its density doubled at the depth
of ninety-three miles, and would attain the density of quicksilver at
the depth of 362 miles. In descending, therefore, towards the centre,
through nearly 4000 miles, the condensation of ordinary substances
would surpass the utmost powers of conception. Dr. Young says, that
steel would be compressed into one-fourth, and stone into one-eighth,
of its bulk at the earth’s centre.--_Mrs. Somerville._


THE WORLD IN A NUTSHELL.

From the many proofs of the non-contact of the atoms, even in the
most solid parts of bodies; from the very great space obviously
occupied by pores--the mass having often no more solidity than a heap
of empty boxes, of which the apparently solid parts may still be as
porous in a second degree and so on; and from the great readiness
with which light passes in all directions through dense bodies, like
glass, rock-crystal, diamond, &c., it has been argued that there is so
exceedingly little of really solid matter even in the densest mass,
that _the whole world_, if the atoms could be brought into absolute
contact, _might be compressed into a nutshell_. We have as yet no means
of determining exactly what relation this idea has to truth.--_Arnott._


THE WORLD OF ATOMS.

The infinite groups of atoms flying through all time and space, in
different directions and under different laws, have interchangeably
tried and exhibited every possible mode of rencounter: sometimes
repelled from each other by concussion; and sometimes adhering to each
other from their own jagged or pointed construction, or from the casual
interstices which two or more connected atoms must produce, and which
may be just adapted to those of other figures,--as globular, oval, or
square. Hence the origin of compound and visible bodies; hence the
origin of large masses of matter; hence, eventually, the origin of the
world.--_Dr. Good’s Book of Nature._

The great Epicurus speculated on “the plastic nature” of atoms, and
attributed to this _nature_ the power they possess of arranging
themselves into symmetric forms. Modern philosophers satisfy themselves
with attraction; and reasoning from analogy, imagine that each atom has
a polar system.--_Hunt’s Poetry of Science._


MINUTE ATOMS OF THE ELEMENTS: DIVISIBILITY OF MATTER.

So minute are the parts of the elementary bodies in their ultimate
state of division, in which condition they are usually termed _atoms_,
as to elude all our powers of inspection, even when aided by the most
powerful microscopes. Who can see the particles of gold in a solution
of that metal in _aqua regia_, or those of common salt when dissolved
in water? Dr. Thomas Thomson has estimated the bulk of an ultimate
particle or atom of lead as less than 1/888492000000000th of a cubic
inch, and concludes that its weight cannot exceed the 1/310000000000th
of a grain.

This curious calculation was made by Dr. Thomson, in order to show to
what degree Matter could be divided, and still be sensible to the eye.
He dissolved a grain of nitrate of lead in 500,000 grains of water,
and passed through the solution a current of sulphuretted hydrogen;
when the whole liquid became sensibly discoloured. Now, a grain of
water may be regarded as being almost equal to a drop of that liquid,
and a drop may be easily spread out so as to cover a square inch of
surface. But under an ordinary microscope the millionth of a square
inch may be distinguished by the eye. The water, therefore, could be
divided into 500,000,000,000 parts. But the lead in a grain of nitrate
of lead weighs 0·62 of a grain; an atom of lead, accordingly, cannot
weigh more than 1/810000000000th of a grain; while the atom of sulphur,
which in combination with the lead rendered it visible, could not
weigh more than 1/2015000000000, that is, the two-billionth part of a
grain.--_Professor Low_; _Jameson’s Journal_, No. 106.


WEIGHT OF AIR.

Air can be so rarefied that the contents of a cubic foot shall not
weigh the tenth part of a grain: if a quantity that would fill a space
the hundredth part of an inch in diameter be separated from the rest,
the air will still be found there, and we may reasonably conceive that
there may be several particles present, though the weight is less than
the seventeen-hundred-millionth of a grain.


DURATION OF THE PYRAMID.

The great reason of the duration of the pyramid above all other forms
is, that it is most fitted to resist the force of gravitation. Thus the
Pyramids of Egypt are the oldest monuments in the world.


INERTIA ILLUSTRATED.

Many things of common occurrence (says Professor Tyndall) are to be
explained by reference to the quality of inactivity. We will here state
a few of them.

When a railway train is moving, if it strike against any obstacle which
arrests its motion, the passengers are thrown forward in the direction
in which the train was proceeding. Such accidents often occur on a
small scale, in attaching carriages at railway stations. The reason is,
that the passengers share the motion of the train, and, as matter, they
tend to persist in motion. When the train is suddenly checked, this
tendency exhibits itself by the falling forward referred to. In like
manner, when a train previously at rest is suddenly set in motion, the
tendency of the passengers to remain at rest evinces itself by their
falling in a direction opposed to that in which the train moves.


THE LEANING TOWER OF PISA.[7]

Sir John Leslie used to attribute the stability of this tower to
the cohesion of the mortar it is built with being sufficient to
maintain it erect, in spite of its being out of the condition required
by physics--to wit, that “in order that a column shall stand, a
perpendicular let fall from the centre of gravity must fall within the
base.” Sir John describes the Tower of Pisa to be in violation of this
principle; but, according to later authorities, the perpendicular falls
within the base.


EARLY PRESENTIMENTS OF CENTRIFUGAL FORCES.

Jacobi, in his researches on the mathematical knowledge of the
Greeks, comments on “the profound consideration of nature evinced by
Anaxagoras, in whom we read with astonishment a passage asserting that
the moon, if the centrifugal force were intermitted, would fall to the
earth like a stone from a sling.” Anaxagoras likewise applied the same
theory of “falling where the force of rotation had been intermitted”
to all the material celestial bodies. In Aristotle and Simplicius may
also be traced the idea of “the non-falling of heavenly bodies when the
rotatory force predominates over the actual falling force, or downward
attraction;” and Simplicius mentions that “water in a phial is not
spilt when the movement of rotation is more rapid than the downward
movement of the water.” This is illustrated at the present day by
rapidly whirling a pail half-filled with water without spilling a drop.

Plato had a clearer idea than Aristotle of the _attractive force_
exercised by the earth’s centre on all heavy bodies removed from
it; for he was acquainted with the acceleration of falling bodies,
although he did not correctly understand the cause. John Philoponus,
the Alexandrian, probably in the sixth century, was the first who
ascribed the movement of the heavenly bodies to a primitive impulse,
connecting with this idea that of the fall of bodies, or the tendency
of all substances, whether heavy or light, to reach the ground. The
idea conceived by Copernicus, and more clearly expressed by Kepler,
who even applied it to the ebb and flow of the ocean, received in 1666
and 1674 a new impulse from Robert Hooke; and next Newton’s theory
of gravitation presented the grand means of converting the whole of
physical astronomy into a true _mechanism of the heavens_.

The law of gravitation knows no exception; it accounts accurately for
the most complex motions of the members of our own system; nay more,
the paths of double stars, far removed from all appreciable effects
of our portion of the universe, are in perfect accordance with its
theory.[8]


HEIGHT OF FALLS.

The fancy of the Greeks delighted itself in wild visions of the height
of falls. In Hesiod’s _Theogony_ it is said, speaking of the fall
of the Titans into Tartarus, “if a brazen anvil were to fall from
heaven nine days and nine nights long, it would reach the earth on the
tenth.” This descent of the anvil in 777,600 seconds of time gives an
equivalent in distance of 309,424 geographical miles (allowance being
made, according to Galle’s calculation, for the considerable diminution
in force of attraction at planetary distances); therefore 1½ times the
distance of the moon from the earth. But, according to the _Iliad_,
Hephæstus fell down to Lemnos in one day; “when but a little breath was
still in him.”--_Note to Humboldt’s Cosmos_, vol. iii.


RATE OF THE FALL OF BODIES.

A body falls in gravity precisely 16-1/16 feet in a second, and the
velocity increases according to the squares of the time, viz.:

    In ¼ (quarter of a second) a body falls           1 foot.
       ½ (half a second)                              4 feet.
       1 second                                      16  ”
       2 ditto                                       64  ”
       3 ditto                                      144  ”

The power of gravity at two miles distance from the earth is four times
less than at one mile; at three miles nine times less, and so on. It
goes on lessening, but is never destroyed.--_Notes in various Sciences._


VARIETIES OF SPEED.

A French scientific work states the ordinary rate to be:

                                                    per second.
    Of a man walking                                   4 feet.
    Of a good horse in harness                        12  ”
    Of a rein-deer in a sledge on the ice             26  ”
    Of an English race-horse                          43  ”
    Of a hare                                         88  ”
    Of a good sailing ship                            19  ”
    Of the wind                                       82  ”
    Of sound                                        1038  ”
    Of a 24-pounder cannon-ball                     1300  ”


LIFTING HEAVY PERSONS.

One of the most extraordinary pages in Sir David Brewster’s _Letters
on Natural Magic_ is the experiment in which a heavy man is raised
with the greatest facility when he is lifted up the instant that his
own lungs, and those of the persons who raise him, are inflated with
air. Thus the heaviest person in the party lies down upon two chairs,
his legs being supported by the one and his back by the other. Four
persons, one at each leg, and one at each shoulder, then try to raise
him--the person to be raised giving two signals, by clapping his hands.
At the first signal, he himself and the four lifters begin to draw a
long and full breath; and when the inhalation is completed, or the
lungs filled, the second signal is given for raising the person from
the chair. To his own surprise, and that of his bearers, he rises with
the greatest facility, as if he were no heavier than a feather. Sir
David Brewster states that he has seen this inexplicable experiment
performed more than once; and he appealed for testimony to Sir Walter
Scott, who had repeatedly seen the experiment, and performed the part
both of the load and of the bearer. It was first shown in England by
Major H., who saw it performed in a large party at Venice, under the
direction of an officer of the American navy.[9]

Sir David Brewster (in a letter to _Notes and Queries_, No. 143)
further remarks, that “the inhalation of the lifters the moment the
effort is made is doubtless essential, and for this reason: when we
make a great effort, either in pulling or lifting, we always fill the
chest with air previous to the effort; and when the inhalation is
completed, we close the _rima glottidis_ to keep the air in the lungs.
The chest being thus kept expanded, the pulling or lifting muscles have
received as it were a fulcrum round which their power is exerted; and
we can thus lift the greatest weight which the muscles are capable of
doing. When the chest collapses by the escape of the air, the lifters
lose their muscular power; reinhalation of air by the liftee can
certainly add nothing to the power of the lifters, or diminish his
own weight, which is only increased by the weight of the air which he
inhales.”


“FORCE CAN NEITHER BE CREATED NOR DESTROYED.”

Professor Faraday, in his able inquiry upon “the Conservation of
Force,” maintains that to admit that force may be destructible, or can
altogether disappear, would be to admit that matter could be uncreated;
for we know matter only by its forces. From his many illustrations we
select the following:

  The indestructibility of individual matter is a most important case
  of the Conservation of Chemical Force. A molecule has been endowed
  with powers which give rise in it to various qualities; and those
  never change, either in their nature or amount. A particle of
  oxygen is ever a particle of oxygen; nothing can in the least wear
  it. If it enters into combination, and disappears as oxygen; if it
  pass through a thousand combinations--animal, vegetable, mineral;
  if it lie hid for a thousand years, and then be evolved,--it is
  oxygen with the first qualities, neither more nor less. It has
  all its original force, and only that; the amount of force which
  it disengaged when hiding itself, has again to be employed in a
  reverse direction when it is set at liberty: and if, hereafter,
  we should decompose oxygen, and find it compounded of other
  particles, we should only increase the strength of the proof of the
  conservation of force; for we should have a right to say of these
  particles, long as they have been hidden, all that we could say of
  the oxygen itself.

In conclusion, he adds:

  Let us not admit the destruction or creation of force without clear
  and constant proof. Just as the chemist owes all the perfection
  of his science to his dependence on the certainty of gravitation
  applied by the balance, so may the physical philosopher expect to
  find the greatest security and the utmost aid in the principle
  of the conservation of force. All that we have that is good and
  safe--as the steam-engine, the electric telegraph, &c.--witness to
  that principle; it would require a perpetual motion, a fire without
  heat, heat without a source, action without reaction, cause without
  effect, or effect without cause, to displace it from its rank as a
  law of nature.


NOTHING LOST IN THE MATERIAL WORLD.

“It is remarkable,” says Kobell in his _Mineral Kingdom_, “how a change
of place, a circulation as it were, is appointed for the inanimate or
naturally immovable things upon the earth; and how new conditions,
new creations, are continually developing themselves in this way. I
will not enter here into the evaporation of water, for instance from
the widely-spreading ocean; how the clouds produced by this pass over
into foreign lands and then fall again to the earth as rain, and how
this wandering water is, partly at least, carried along new journeys,
returning after various voyages to its original home: the mere
mechanical phenomena, such as the transfer of seeds by the winds or by
birds, or the decomposition of the surface of the earth by the friction
of the elements, suffice to illustrate this.”


TIME AN ELEMENT OF FORCE.

Professor Faraday observes that Time is growing up daily into
importance as an element in the exercise of Force, which he thus
strikingly illustrates:

  The earth moves in its orbit of time; the crust of the earth moves
  in time; light moves in time; an electro-magnet requires time for
  its charge by an electric current: to inquire, therefore, whether
  power, acting either at sensible or insensible distances, always
  acts in _time_, is not to be metaphysical; if it acts in time and
  across space, it must act by physical lines of force; and our view
  of the nature of force may be affected to the extremest degree
  by the conclusions which experiment and observation on time may
  supply, being perhaps finally determinable only by them. To inquire
  after the possible time in which gravitating, magnetic, or electric
  force is exerted, is no more metaphysical than to mark the times
  of the hands of a clock in their progress; or that of the temple
  of Serapis, and its ascents and descents; or the periods of the
  occultation of Jupiter’s satellites; or that in which the light
  comes from them to the earth. Again, in some of the known cases of
  the action of time something happens while _the time_ is passing
  which did not happen before, and does not continue after; it is
  therefore not metaphysical to expect an effect in _every_ case, or
  to endeavour to discover its existence and determine its nature.


CALCULATION OF HEIGHTS AND DISTANCES.

By the assistance of a seconds watch the following interesting
calculations may be made:

  If a traveller, when on a precipice or on the top of a building,
  wish to ascertain the height, he should drop a stone, or any other
  substance sufficiently heavy not to be impeded by the resistance of
  the atmosphere; and the number of seconds which elapse before it
  reaches the bottom, carefully noted on a seconds watch, will give
  the height. For the stone will fall through the space of 16-1/8
  feet during the first second, and will increase in rapidity as the
  square of the time employed in the fall: if, therefore, 16-1/8 be
  multiplied by the number of seconds the stone has taken to fall,
  this product also multiplied by the same number of seconds will
  give the height. Suppose the stone takes five seconds to reach the
  bottom:

    16-1/8 × 5 = 80-5/8 × 5 = 403-1/8, height of the precipice.

  The Count Xavier de Maistre, in his _Expédition nocturne autour
  de ma Chambre_, anxious to ascertain the exact height of his room
  from the ground on which Turin is built, tells us he proceeded
  as follows: “My heart beat quickly, and I just counted three
  pulsations from the instant I dropped my slipper until I heard
  the sound as it fell in the street, which, according to the
  calculations made of the time taken by bodies in their accelerated
  fall, and of that employed by the sonorous undulations of the
  air to arrive from the street to my ear, gave the height of my
  apartment as 94 feet 3 inches 1 tenth (French measure), supposing
  that my heart, agitated as it was, beat 120 times in a minute.”

  A person travelling may ascertain his rate of walking by the aid
  of a slight string with a piece of lead at one end, and the use of
  a seconds watch; the string being knotted at distances of 44 feet,
  the 120th part of an English mile, and bearing the same proportion
  to a mile that half a minute bears to an hour. If the traveller,
  when going at his usual rate, drops the lead, and suffers the
  string to slip through his hand, the number of knots which pass in
  half a minute indicate the number of miles he walks in an hour.
  This contrivance is similar to a _log-line_ for ascertaining a
  ship’s rate at sea: the lead is enclosed in wood (whence the name
  _log_), that it may float, and the divisions, which are called
  _knots_, are measured for nautical miles. Thus, if ten knots are
  passed in half a minute, they show that the vessel is sailing at
  the rate of ten knots, or miles, an hour: a seconds watch would
  here be of great service, but the half-minute sand-glass is in
  general use.

  The rapidity of a river may be ascertained by throwing in a light
  floating substance, which, if not agitated by the wind, will move
  with the same celerity as the water: the distance it floats in a
  certain number of seconds will give the rapidity of the stream; and
  this indicates the height of its source, the nature of its bottom,
  &c.--See _Sir Howard Douglas on Bridges_. _Thomson’s Time and
  Time-keepers._


SAND IN THE HOUR-GLASS.

It is a noteworthy fact, that the flow of Sand in the Hour-glass is
perfectly equable, whatever may be the quantity in the glass; that is,
the sand runs no faster when the upper half of the glass is quite full
than when it is nearly empty. It would, however, be natural enough to
conclude, that when full of sand it would be more swiftly urged through
the aperture than when the glass was only a quarter full, and near the
close of the hour.

The fact of the even flow of sand may be proved by a very simple
experiment. Provide some silver sand, dry it over or before the fire,
and pass it through a tolerably fine sieve. Then take a tube, of any
length or diameter, closed at one end, in which make a small hole, say
the eighth of an inch; stop this with a peg, and fill up the tube with
the sifted sand. Hold the tube steadily, or fix it to a wall or frame
at any height from a table; remove the peg, and permit the sand to flow
in any measure for any given time, and note the quantity. Then let the
tube be emptied, and only half or a quarter filled with sand; measure
again for a like time, and the same quantity of sand will flow: even if
you press the sand in the tube with a ruler or stick, the flow of the
sand through the hole will not be increased.

The above is explained by the fact, that when the sand is poured into
the tube, it fills it with a succession of conical heaps; and that all
the weight which the bottom of the tube sustains is only that of the
heap which _first_ falls upon it, as the succeeding heaps do not press
downward, but only against the sides or walls of the tube.


FIGURE OF THE EARTH.

By means of a purely astronomical determination, based upon the action
which the earth exerts on the motion of the moon, or, in other words,
on the inequalities in lunar longitudes and latitudes, Laplace has
shown in one single result the mean Figure of the Earth.

  It is very remarkable that an astronomer, without leaving his
  observatory, may, merely by comparing his observations with
  mean analytical results, not only be enabled to determine with
  exactness the size and degree of ellipticity of the earth, but
  also its distance from the sun and moon; results that otherwise
  could only be arrived at by long and arduous expeditions to the
  most remote parts of both hemispheres. The moon may therefore, by
  the observation of its movements, render appreciable to the higher
  departments of astronomy the ellipticity of the earth, as it taught
  the early astronomers the rotundity of our earth by means of its
  eclipses.--_Laplace’s Expos. du Syst. du Monde._


HOW TO ASCERTAIN THE EARTH’S MAGNITUDE.

Sir John Herschel gives the following means of approximation. It
appears by observation that two points, each ten feet above the
surface, cease to be visible from each other over still water, and, in
average atmospheric circumstances, at a distance of about eight miles.
But 10 feet is the 528th part of a mile; so that half their distance,
or four miles, is to the height of each as 4 × 528, or 2112:1, and
therefore in the same proportion to four miles is the length of the
earth’s diameter. It must, therefore, be equal to 4 × 2112 = 8448, or
in round numbers, about 8000 miles, which is not very far from the
truth.

  The excess is, however, about 100 miles, or 1/80th part. As
  convenient numbers to remember, the reader may bear in mind, that
  in our latitude there are just as many thousands of feet in a
  degree of the meridian as there are days in the year (365); that,
  speaking loosely, a degree is about seventy British statute miles,
  and a second about 100 feet; that the equatorial circumference of
  the earth is a little less than 25,000 miles (24,899), and the
  ellipticity or polar flattening amounts to 1/300th part of the
  diameter.--_Outlines of Astronomy._


MASS AND DENSITY OF THE EARTH.

With regard to the determination of the Mass and Density of the Earth
by direct experiment, we have, in addition to the deviations of the
pendulum produced by mountain masses, the variation of the same
instruments when placed in a mine 1200 feet in depth. The most recent
experiments were conducted by Professor Airy, in the Harton coal-pit,
near South Shields:[10] the oscillations of the pendulum at the bottom
of the pit were compared with those of a clock above; the beats of the
clock were transferred below for comparison by an electrio wire; and it
was thus determined that a pendulum vibrating seconds at the mouth of
the pit would gain 2¼ seconds per day at its bottom. The final result
of the calculations depending on this experiment, which were published
in the _Philosophical Transactions_ of 1856, gives 6·565 for the mean
density of the earth. The celebrated Cavendish experiment, by means
of which the density of the earth was determined by observing the
attraction of leaden balls on each other, has been repeated in a manner
exhibiting an astonishing amount of skill and patience by the late Mr.
F. Baily.[11] The result of these experiments, combined with those
previously made, gives as a mean result 5·441 as the earth’s density,
when compared with water; thus confirming one of Newton’s astonishing
divinations, that the mean density of the earth would be found to be
between five and six times that of water.

  Humboldt is, however, of opinion that “we know only the mass of
  the whole earth and its mean density by comparing it with the
  open strata, which alone are accessible to us. In the interior of
  the earth, where all knowledge of its chemical and mineralogical
  character fails, we are limited to as pure conjecture as in the
  remotest bodies that revolve round the sun. We can determine
  nothing with certainty regarding the depth at which the geological
  strata must be supposed to be in a state of softening or of liquid
  fusion, of the condition of fluids when heated under an enormous
  pressure, or of the law of the increase of density from the upper
  surface to the centre of the earth.”--_Cosmos_, vol. i.

In M. Foucault’s beautiful experiment, by means of the vibration of
a long pendulum, consisting of a heavy mass of metal suspended by a
long wire from a strong fixed support, is demonstrated to the eye
the rotation of the earth. The Gyroscope of the same philosopher
is regarded not as a mere philosophical toy; but the principles of
dynamics, by means of which it is made to demonstrate the earth’s
rotation on its own axis, are explained with the greatest clearness.
Thus the ingenuity of M. Foucault, combined with a profound knowledge
of mechanics, has obtained proofs of one of the most interesting
problems of astronomy from an unsuspected source.


THE EARTH AND MAN COMPARED.

The Earth--speaking roundly--is 8000 miles in diameter; the atmosphere
is calculated to be fifty miles in altitude; the loftiest mountain peak
is estimated at five miles above the level of the sea, for this height
has never been visited by man; the deepest mine that he has formed is
1650 feet; and his own stature does not average six feet. Therefore, if
it were possible for him to construct a globe 800 feet--or twice the
height of St. Paul’s Cathedral--in diameter, and to place upon any one
point of its surface an atom of 1/4380th of an inch in diameter, and
1/720th of an inch in height, it would correctly denote the proportion
that man bears to the earth upon which he moves.

  When by measurements, in which the evidence of the method advances
  equally with the precision of the results, the volume of the earth
  is reduced to the millionth part of the volume of the sun; when
  the sun himself, transported to the region of the stars, takes
  up a very modest place among the thousands of millions of those
  bodies that the telescope has revealed to us; when the 38,000,000
  of leagues which separate the earth from the sun have become, by
  reason of their comparative smallness, a base totally insufficient
  for ascertaining the dimensions of the visible universe; when even
  the swiftness of the luminous rays (77,000 leagues per second)
  barely suffices for the common valuations of science; when, in
  short, by a chain of irresistible proofs, certain stars have
  retired to distances that light could not traverse in less than a
  million of years;--we feel as if annihilated by such immensities.
  In assigning to man and to the planet that he inhabits so small a
  position in the material world, astronomy seems really to have made
  progress only to humble us.--_Arago._


MEAN TEMPERATURE OF THE EARTH’S SURFACE.

Professor Dove has shown, by taking at all seasons the mean of the
temperature of points diametrically opposite to each other, that the
mean temperature _of the whole earth’s surface_ in June considerably
exceeds that in December. This result, which is at variance with the
greater proximity of the sun in December, is, however, due to a totally
different and very powerful cause,--the greater amount of land in
that hemisphere which has its summer solstice in June (_i. e._ the
northern); and the fact is so explained by him. The effect of land
under sunshine is to throw heat into the general atmosphere, and to
distribute it by the carrying power of the latter over the whole earth.
Water is much less effective in this respect, the heat penetrating its
depths and being there absorbed; so that the surface never acquires
a very elevated temperature, even under the equator.--_Sir John
Herschel’s Outlines._


TEMPERATURE OF THE EARTH STATIONARY.

Although, according to Bessel, 25,000 cubic miles of water flow in
every six hours from one quarter of the earth to another, and the
temperature is augmented by the ebb and flow of every tide, all
that we know with certainty is, that the _resultant effect_ of all
the thermal agencies to which the earth is exposed has undergone
no perceptible change within the historic period. We owe this fine
deduction to Arago. In order that the _date palm_ should ripen its
fruit, the mean temperature of the place must exceed 70 deg. Fahr.;
and, on the other hand, the _vine_ cannot be cultivated successfully
when the temperature is 72 deg. or upwards. Hence the mean temperature
of any place at which these two plants flourished and bore fruit must
lie between these narrow limits, _i. e._ could not differ from 71 deg.
Fahr. by more than a single degree. Now from the Bible we learn that
both plants were _simultaneously_ cultivated in the central valleys
of Palestine in the time of Moses; and its then temperature is thus
definitively determined. It is the same at the present time; so that
the mean temperature of this portion of the globe has not sensibly
altered in the course of thirty-three centuries.


THEORY OF CRYSTALLISATION.

Professor Plücker has ascertained that certain crystals, in particular
the cyanite, “point very well to the north by the magnetic power of the
earth only. It is a true compass-needle; and more than that, you may
obtain its declination.” Upon this Mr. Hunt remarks: “We must remember
that this crystal, the cyanite, is a compound of silica and alumina
only. This is the amount of experimental evidence which science has
afforded in explanation of the conditions under which nature pursues
her wondrous work of crystal formation. We see just sufficient of
the operation to be convinced that the luminous star which shines in
the brightness of heaven, and the cavern-secreted gem, are equally
the result of forces which are known to us in only a few of their
modifications.”--_Poetry of Science._

Gay Lussac first made the remark, that a crystal of potash-alum,
transferred to a solution of ammonia-alum, continued to increase
without its form being modified, and might thus be covered with
alternate layers of the two alums, preserving its regularity and proper
crystalline figure. M. Beudant afterwards observed that other bodies,
such as the sulphates of iron and copper, might present themselves
in crystals of the same form and angles, although the form was not a
simple one, like that of alum. But M. Mitscherlich first recognised
this correspondence in a sufficient number of cases to prove that it
was a general consequence of similarity of composition in different
bodies.--_Graham’s Elements of Chemistry._


IMMENSE CRYSTALS.

Crystals are found in the most microscopic character, and of an
exceedingly large size. A crystal of quartz at Milan is three feet and
a quarter long, and five feet and a half in circumference: its weight
is 870 pounds. Beryls have been found in New Hampshire measuring four
feet in length.--_Dana._


VISIBLE CRYSTALLISATION.

Professor Tyndall, in a lecture delivered by him at the Royal
Institution, London, on the properties of Ice, gave the following
interesting illustration of crystalline force. By perfectly cleaning a
piece of glass, and placing on it a film of a solution of chloride of
ammonium or sal ammoniac, the action of crystallisation was shown to
the whole audience. The glass slide was placed in a microscope, and the
electric light passing through it was concentrated on a white disc. The
image of the crystals, as they started into existence, and shot across
the disc in exquisite arborescent and symmetrical forms, excited the
admiration of every one. The lecturer explained that the heat, causing
the film of moisture to evaporate, brought the particles of salt
sufficiently near to exercise the crystalline force, the result being
the beautiful structure built up with such marvellous rapidity.


UNION OF MINERALOGY AND GEOMETRY.

It is a peculiar characteristic of minerals, that while plants and
animals differ in various regions of the earth, mineral matter of the
same character may be discovered in any part of the world,--at the
Equator or towards the Poles; at the summit of the loftiest mountains,
and in works far beneath the level of the sea. The granite of Australia
does not necessarily differ from that of the British islands; and ores
of the same metals (the proper geological conditions prevailing) may
be found of the same general character in all regions. Climate and
geographical position have no influence on the composition of mineral
substances.

This uniformity may, in some measure, have induced philosophers to
seek its extension to the forms of crystallography. About 1760 (says
Mr. Buckle, in his _History of Civilization_), Romé de Lisle set the
first example of studying crystals, according to a scheme so large as
to include all the varieties of their primary forms, and to account
for their irregularities and the apparent caprice with which they
were arranged. In this investigation he was guided by the fundamental
assumption, that what is called an irregularity is in truth perfectly
regular, and that the operations of nature are invariable. Haüy applied
this great idea to the almost innumerable forms in which minerals
crystallise. He thus achieved a complete union between mineralogy and
geometry; and, bringing the laws of space to bear on the molecular
arrangements of matter, he was able to penetrate into the intimate
structure of crystals. By this means he proved that the secondary
forms of all crystals are derived from their primary forms by a
regular process of decrement; and that when a substance is passing
from a liquid to a solid state, its particles cohere, according to a
scheme which provides for every possible change, since it includes
even those subsequent layers which alter the ordinary type of the
crystal, by disturbing its natural symmetry. To ascertain that such
violations of symmetry are susceptible of mathematical calculation,
was to make a vast addition to our knowledge; and, by proving that
even the most uncouth and singular forms are the natural results of
their antecedents, Haüy laid the foundation of what may be called the
pathology of the inorganic world. However paradoxical such a notion may
appear, it is certain that symmetry is to crystals what health is to
animals; so that an irregularity of shape in the first corresponds with
an appearance of disease in the second.--See _Hist. Civilization_, vol.
i.


REPRODUCTIVE CRYSTALLISATION.

The general belief that only organic beings have the power of
reproducing lost parts has been disproved by the experiments of Jordan
on crystals. An octohedral crystal of alum was fractured; it was then
replaced in a solution, and after a few days its injury was seen to be
repaired. The whole crystal had of course increased in size; but the
increase on the broken surface had been so much greater that a perfect
octohedral form was regained.--_G. H. Lewes._

This remarkable power possessed by crystals, in common with animals,
of repairing their own injuries had, however, been thus previously
referred to by Paget, in his _Pathology_, confirming the experiments
of Jordan on this curious subject: “The ability to repair the damages
sustained by injury ... is not an exclusive property of living beings;
for even crystals will repair themselves when, after pieces have been
broken from them, they are placed in the same conditions in which they
were first formed.”


GLASS BROKEN BY SAND.

In some glass-houses the workmen show glass which has been cooled in
the open air; on this they let fall leaden bullets without breaking the
glass. They afterwards desire you to let a few grains of sand fall upon
the glass, by which it is broken into a thousand pieces. The reason
of this is, that the lead does not scratch the surface of the glass;
whereas the sand, being sharp and angular, scratches it sufficiently to
produce the above effect.




Sound and Light.


SOUNDING SAND.

Mr. Hugh Miller, the geologist, when in the island of Eigg, in the
Hebrides, observed that a musical sound was produced when he walked
over the white dry sand of the beach. At each step the sand was driven
from his footprint, and the noise was simultaneous with the scattering
of the sand; the cause being either the accumulated vibrations of
the air when struck by the driven sand, or the accumulated sounds
occasioned by the mutual impact of the particles of sand against each
other. If a musket-ball passing through the air emits a whistling note,
each individual particle of sand must do the same, however faint be
the note which it yields; and the accumulation of these infinitesimal
vibrations must constitute an audible sound, varying with the number
and velocity of the moving particles. In like manner, if two plates of
silex or quartz, which are but crystals of sand, give out a musical
sound when mutually struck, the impact or collision of two minute
crystals or particles of sand must do the same, in however inferior a
degree; and the union of all these sounds, though singly imperceptible,
may constitute the musical notes of “the Mountain of the Bell” in
Arabia Petræa, or the lesser sounds of the trodden sea-beach of
Eigg.--_North-British Review_, No. 5.


INTENSITY OF SOUND IN RAREFIED AIR.

The experiences during ascents of the highest mountains are
contradictory. Saussure describes the sounds on the top of Mont Blanc
as remarkably weak: a pistol-shot made no more noise than an ordinary
Chinese cracker, and the popping of a bottle of champagne was scarcely
audible. Yet Martius, in the same situation, was able to distinguish
the voices of the guides at a distance of 1340 feet, and to hear the
tapping of a lead pencil upon a metallic surface at a distance of from
75 to 100 feet.

MM Wertheim and Breguet have propagated sound over the wire of an
electric telegraph at the rate of 11,454 feet per second.


DISTANCE AT WHICH THE HUMAN VOICE MAY BE HEARD.

Experience shows that the human voice, under favourable circumstances,
is capable of filling a larger space than was ever probably enclosed
within the walls of a single room. Lieutenant Foster, on Parry’s third
Arctic expedition, found that he could converse with a man across the
harbour of Port Bowen, a distance of 6696 feet, or about one mile and a
quarter. Dr. Young records that at Gibraltar the human voice has been
heard at a distance of ten miles. If sound be prevented from spreading
and losing itself in the air, either by a pipe or an extensive flat
surface, as a wall or still water, it may be conveyed to a great
distance. Biot heard a flute clearly through a tube of cast-iron (the
water-pipes of Paris) 3120 feet long: the lowest whisper was distinctly
heard; indeed, the only way not to be heard was not to speak at all.


THE ROAR OF NIAGARA.

The very nature of the sound of running water pronounces its origin
to be the bursting of bubbles: the impact of water against water is a
comparatively subordinate cause, and could never of itself occasion the
murmur of a brook; whereas, in streams which Dr. Tyndall has examined,
he, in all cases where a ripple was heard, discovered bubbles caused by
the broken column of water. Now, were Niagara continuous, and without
lateral vibration, it would be as silent as a cataract of ice. In all
probability, it has its “contracted sections,” after passing which
it is broken into detached masses, which, plunging successively upon
the air-bladders formed by their precursors, suddenly liberate their
contents, and thus create _the thunder of the waterfall_.


FIGURES PRODUCED BY SOUND.

Stretch a sheet of wet paper over the mouth of a glass tumbler which
has a footstalk, and glue or paste the paper at the edges. When the
paper is dry, strew dry sand thinly upon its surface. Place the tumbler
on a table, and hold immediately above it, and parallel to the paper,
a plate of glass, which you also strew with sand, having previously
rubbed the edges smooth with emery powder. Draw a violin-bow along any
part of the edges; and as the sand upon the glass is made to vibrate,
it will form various figures, which will be accurately imitated by the
sand upon the paper; or if a violin or flute be played within a few
inches of the paper, they will cause the sand upon its surface to form
regular lines and figures.


THE TUNING-FORK A FLUTE-PLAYER.

Take a common tuning-fork, and on one of its branches fasten with
sealing-wax a circular piece of card of the size of a small wafer, or
sufficient nearly to cover the aperture of a pipe, as the sliding of
the upper end of a flute with the mouth stopped: it may be tuned in
unison with the loaded tuning-fork by means of the movable stopper or
card, or the fork may be loaded till the unison is perfect. Then set
the fork in vibration by a blow on the unloaded branch, and hold the
card closely over the mouth of the pipe, as in the engraving, when a
note of surprising clearness and strength will be heard. Indeed a flute
may be made to “speak” perfectly well, by holding close to the opening
a vibrating tuning-fork, while the fingering proper to the note of the
fork is at the same time performed.


THEORY OF THE JEW’S HARP.

If you cause the tongue of this little instrument to vibrate, it will
produce a very low sound; but if you place it before a cavity (as the
mouth) containing a column of air, which vibrates much faster, but
in the proportion of any simple multiple, it will then produce other
higher sounds, dependent upon the reciprocation of that portion of
the air. Now the bulk of air in the mouth can be altered in its form,
size, and other circumstances, so as to produce by reciprocation many
different sounds; and these are the sounds belonging to the Jew’s Harp.

A proof of this fact has been given by Mr. Eulenstein, who fitted into
a long metallic tube a piston, which being moved, could be made to
lengthen or shorten the efficient column of air within at pleasure. A
Jew’s Harp was then so fixed that it could be made to vibrate before
the mouth of the tube, and it was found that the column of air produced
a series of sounds, according as it was lengthened or shortened; a
sound being produced whenever the length of the column was such that
its vibrations were a multiple of those of the Jew’s Harp.


SOLAR AND ARTIFICIAL LIGHT COMPARED.

The most intensely ignited solid (produced by the flame of Lieutenant
Drummond’s oxy-hydrogen lamp directed against a surface of chalk)
appears only as black spots on the disc of the sun, when held between
it and the eye; or in other words, Drummond’s light is to the light of
the sun’s disc as 1 to 146. Hence we are doubly struck by the felicity
with which Galileo, as early as 1612, by a series of conclusions on
the smallness of the distance from the sun at which the disc of Venus
was no longer visible to the naked eye, arrived at the result that
the blackest nucleus of the sun’s spots was more luminous than the
brightest portions of the full moon. (See “The Sun’s Light compared
with Terrestrial Lights,” in _Things not generally Known_, pp. 4, 5.)


SOURCE OF LIGHT.

Mr. Robert Hunt, in a lecture delivered by him at the Russell
Institution, “On the Physics of a Sunbeam,” mentions some experiments
by Lord Brougham on the sunbeam, in which, by placing the edge of a
sharp knife just within the limit of the light, the ray was inflected
from its previous direction, and coloured red; and when another knife
was placed on the opposite side, it was deflected, and the colour was
blue. These experiments (says Mr. Hunt) seem to confirm Sir Isaac
Newton’s theory, that light is a fluid emitted from the sun.


THE UNDULATORY SCALE OF LIGHT.

The white light of the sun is well known to be composed of several
coloured rays; or rather, according to the theory of undulations, when
the rate at which a ray vibrates is altered, a different sensation
is produced upon the optic nerve. The analytical examination of
this question shows that to produce a red colour the ray of light
must give 37,640 undulations in an inch, and 458,000,000,000,000 in
a second. Yellow light requires 44,000 undulations in an inch, and
535,000,000,000,000 in a second; whilst the effect of blue results from
51,110 undulations within an inch, and 622,000,000,000,000 of waves in
a second of time.--_Hunt’s Poetry of Science._


VISIBILITY OF OBJECTS.

In terrestrial objects, the form, no less than the modes of
illumination, determines the magnitude of the smallest angle of vision
for the naked eye. Adams very correctly observed that a long and
slender staff can be seen at a much greater distance than a square
whose sides are equal to the diameter of the staff. A stripe may be
distinguished at a greater distance than a spot, even when both are of
the same diameter.

The _minimum_ optical visual angle at which terrestrial objects can
be recognised by the naked eye has been gradually estimated lower and
lower, from the time when Robert Hooke fixed it exactly at a full
minute, and Tobias Meyer required 34″ to perceive a black speck on
white paper, to the period of Leuwenhoeck’s experiments with spiders’
threads, which are visible to ordinary sight at an angle of 4″·7. In
Hueck’s most accurate experiments on the problem of the movement of
the crystalline lens, white lines on a black ground were seen at an
angle of 1″·2; a spider’s thread at 0″·6; and a fine glistening wire at
scarcely 0″·2.

  Humboldt, when at Chillo, near Quito, where the crests of the
  volcano of Pichincha lay at a horizontal distance of 90,000 feet,
  was much struck by the circumstance that the Indians standing near
  distinguished the figure of Bonpland (then on an expedition to the
  volcano), as a white point moving on the black basaltic sides of
  the rock, sooner than Humboldt could discover him with a telescope.
  Bonpland was enveloped in a white cotton poncho: assuming the
  breadth across the shoulders to vary from three to five feet,
  according as the mantle clung to the figure or fluttered in the
  breeze, and judging from the known distance, the angle at which the
  moving object could be distinctly seen varied from 7″ to 12″. White
  objects on a black ground are, according to Hueck, distinguished at
  a greater distance than black objects on a white ground.

  Gauss’s heliotrope light has been seen with the naked eye reflected
  from the Brocken on Hobenhagen at a distance of about 227,000 feet,
  or more than 42 miles; being frequently visible at points in which
  the apparent breadth of a three-inch mirror was only 0″·43.


THE SMALLEST BRIGHT BODIES.

Ehrenberg has found from experiments on the dust of diamonds, that
a diamond superficies of 1/100th of a line in diameter presents a
much more vivid light to the naked eye than one of quicksilver of the
same diameter. On pressing small globules of quicksilver on a glass
micrometer, he easily obtained smaller globules of the 1/100th to the
1/2000th of a line in diameter. In the sunshine he could only discern
the reflection of light, and the existence of such globules as were
1/300th of a line in diameter, with the naked eye. Smaller ones did
not affect his eye; but he remarked that the actual bright part of the
globule did not amount to more than 1/900th of a line in diameter.
Spider threads of 1/2000th in diameter were still discernible from
their lustre. Ehrenberg concludes that there are in organic bodies
magnitudes capable of direct proof which are in diameter 1/100000 of a
line; and others, that can be indirectly proved, which may be less than
a six-millionth part of a Parisian line in diameter.


VELOCITY OF LIGHT.

It is scarcely possible so to strain the imagination as to conceive
the Velocity with which Light travels. “What mere assertion will make
any man believe,” asks Sir John Herschel, “that in one second of time,
in one beat of the pendulum of a clock, a ray of light travels over
192,000 miles; and would therefore perform the tour of the world in
about the same time that it requires to wink with our eyelids, and in
much less time than a swift runner occupies in taking a single stride?”
Were a cannon-ball shot directly towards the sun, and were it to
maintain its full speed, it would be twenty years in reaching it; and
yet light travels through this space in seven or eight minutes.

The result given in the _Annuaire_ for 1842 for the velocity of light
in a second is 77,000 leagues, which corresponds to 215,834 miles;
while that obtained at the Pulkowa Observatory is 189,746 miles.
William Richardson gives as the result of the passage of light from the
sun to the earth 8´ 19″·28, from which we obtain a velocity of 215,392
miles in a second.--_Memoirs of the Astronomical Society_, vol. iv.

In other words, light travels a distance equal to eight times the
circumference of the earth between two beats of a clock. This is a
prodigious velocity; but the measure of it is very certain.--_Professor
Airy._

The navigator who has measured the earth’s circuit by his hourly
progress, or the astronomer who has paced a degree of the meridian, can
alone form a clear idea of velocity, when we tell him that light moves
through a space equal to the circumference of the earth in _the eighth
part of a second_--in the twinkling of an eye.

  Could an observer, placed in the centre of the earth, see this
  moving light, as it describes the earth’s circumference, it would
  appear a luminous ring; that is, the impression of the light at the
  commencement of its journey would continue on the retina till the
  light had completed its circuit. Nay, since the impression of light
  continues longer than the _fourth_ part of a second, _two_ luminous
  rings would be seen, provided the light made _two_ rounds of the
  earth, and in paths not coincident.


APPARATUS FOR THE MEASUREMENT OF LIGHT.

Humboldt enumerates the following different methods adopted for the
Measurement of Light: a comparison of the shadows of artificial lights,
differing in numbers and distance; diaphragms; plane-glasses of
different thickness and colour; artificial stars formed by reflection
on glass spheres; the juxtaposition of two seven-feet telescopes,
separated by a distance which the observer could pass in about a
second; reflecting instruments in which two stars can be simultaneously
seen and compared, when the telescope has been so adjusted that the
star gives two images of like intensity; an apparatus having (in
front of the object-glass) a mirror and diaphragms, whose rotation
is measured on a ring; telescopes with divided object-glasses, on
either half of which the stellar light is received through a prism;
astrometers, in which a prism reflects the image of the moon or
Jupiter, and concentrates it through a lens at different distances into
a star more or less bright.--_Cosmos_, vol. iii.


HOW FIZEAU MEASURED THE VELOCITY OF LIGHT.

This distinguished physicist has submitted the Velocity of Light
to terrestrial measurement by means of an ingeniously constructed
apparatus, in which artificial light (resembling stellar light),
generated from oxygen and hydrogen, is made to pass back, by means of
a mirror, over a distance of 28,321 feet to the same point from which
it emanated. A disc, having 720 teeth, which made 12·6 rotations in a
second, alternately obscured the ray of light and allowed it to be seen
between the teeth on the margin. It was supposed, from the marking of
a counter, that the artificial light traversed 56,642 feet, or the
distance to and from the stations, in 1/1800th part of a second, whence
we obtain a velocity of 191,460 miles in a second.[12] This result
approximates most closely to Delambre’s (which was 189,173 miles), as
obtained from Jupiter’s satellites.

  The invention of the rotating mirror is due to Wheatstone, who made
  an experiment with it to determine the velocity of the propagation
  of the discharge of a Leyden battery. The most striking application
  of the idea was made by Fizeau and Foucault, in 1853, in carrying
  out a proposition made by Arago, soon after the invention of the
  mirror: we have here determined in a distance of twelve feet no
  less than the velocity with which light is propagated, which is
  known to be nearly 200,000 miles a second; the distance mentioned
  corresponds therefore to the 77-millionth part of a second. The
  object of these measurements was to compare the velocity of light
  in air with its velocity in water; which, when the length is
  greater, is not sufficiently transparent. The most complete optical
  and mechanical aids are here necessary: the mirror of Foucault
  made from 600 to 800 revolutions in a second, while that of Fizeau
  performed 1200 to 1500 in the same time.--_Prof. Helmholtz on the
  Methods of Measuring very small Portions of Time._


WHAT IS DONE BY POLARISATION OF LIGHT.

Malus, in 1808, was led by a casual observation of the light of the
setting sun, reflected from the windows of the Palais de Luxembourg,
at Paris, to investigate more thoroughly the phenomena of double
refraction, of ordinary and of chromatic polarisation, of interference
and of diffraction of light. Among his results may be reckoned the
means of distinguishing between direct and reflected light; the power
of penetrating, as it were, into the constitution of the body of
the sun and of its luminous envelopes; of measuring the pressure of
atmospheric strata, and even the smallest amount of water they contain;
of ascertaining the depths of the ocean and its rocks by means of
a tourmaline plate; and in accordance with Newton’s prediction, of
comparing the chemical composition of several substances with their
optical effects.

  Arago, in a letter to Humboldt, states that by the aid of his
  polariscope, he discovered, before 1820, that the light of all
  terrestrial objects in a state of incandescence, whether they be
  solid or liquid, is natural, so long as it emanates from the object
  in perpendicular rays. On the other hand, if such light emanate
  at an acute angle, it presents manifest proofs of polarisation.
  This led M. Arago to the remarkable conclusion, that light is not
  generated on the surface of bodies only, but that some portion is
  actually engendered within the substance itself, even in the case
  of platinum.

A ray of light which reaches our eyes after traversing many millions
of miles, from, the remotest regions of heaven, announces, as it were
of itself, in the polariscope, whether it is reflected or refracted,
whether it emanates from a solid or fluid or gaseous body; it announces
even the degree of its intensity.--_Humboldt’s Cosmos_, vols. i. and ii.


MINUTENESS OF LIGHT.

There is something wonderful, says Arago, in the experiments which have
led natural philosophers legitimately to talk of the different sides of
a ray of light; and to show that millions and millions of these rays
can simultaneously pass through the eye of a needle without interfering
with each other!


THE IMPORTANCE OF LIGHT.

Light affects the respiration of animals just as it affects the
respiration of plants. This is novel doctrine, but it is demonstrable.
In the day-time we expire more carbonic acid than during the night; a
fact known to physiologists, who explain it as the effect of sleep: but
the difference is mainly owing to the presence or absence of sunlight;
for sleep, as sleep, _increases_, instead of diminishing, the amount
of carbonic acid expired, and a man sleeping will expire more carbonic
acid than if he lies quietly awake under the same conditions of light
and temperature; so that if less is expired during the night than
during the day, the reason cannot be sleep, but the absence of light.
Now we understand why men are sickly and stunted who live in narrow
streets, alleys, and cellars, compared with those who, under similar
conditions of poverty and dirt, live in the sunlight.--_Blackwood’s
Edinburgh Magazine_, 1858.

  The influence of light on the colours of organised creation is well
  shown in the sea. Near the shores we find seaweeds of the most
  beautiful hues, particularly on the rocks which are left dry by
  the tides; and the rich tints of the actiniæ which inhabit shallow
  water must often have been observed. The fishes which swim near the
  surface are also distinguished by the variety of their colours,
  whereas those which live at greater depths are gray, brown, or
  black. It has been found that after a certain depth, where the
  quantity of light is so reduced that a mere twilight prevails, the
  inhabitants of the ocean become nearly colourless.--_Hunt’s Poetry
  of Science._


ACTION OF LIGHT ON MUSCULAR FIBRES.

That light is capable of acting on muscular fibres, independently
of the influence of the nerves, was mentioned by several of the old
anatomists, but repudiated by later authorities. M. Brown Séquard has,
however, proved to the Royal Society that some portions of muscular
fibre--the iris of the eye, for example--are affected by light
independently of any reflex action of the nerves, thereby confirming
former experiences. The effect is produced by the illuminating rays
only, the chemical and heat rays remaining neutral. And not least
remarkable is the fact, that the iris of an eel showed itself
susceptible of the excitement _sixteen days after the eyes were removed
from the creature’s head_. So far as is yet known, this muscle is the
only one on which light thus takes effect.--_Phil. Trans. 1857._


LIGHT NIGHTS.

It is not possible, as well-attested facts prove, perfectly to explain
the operations at work in the much-contested upper boundaries of
our atmosphere. The extraordinary lightness of whole nights in the
year 1831, during which small print might be read at midnight in
the latitudes of Italy and the north of Germany, is a fact directly
at variance with all that we know, according to the most recent and
acute researches on the crepuscular theory and the height of the
atmosphere.--_Biot._


PHOSPHORESCENCE OF PLANTS.

Mr. Hunt recounts these striking instances. The leaves of the _œnothera
macrocarpa_ are said to exhibit phosphoric light when the air is
highly charged with electricity. The agarics of the olive-grounds of
Montpelier too have been observed to be luminous at night; but they
are said to exhibit no light, even in darkness, _during the day_. The
subterranean passages of the coal-mines near Dresden are illuminated by
the phosphorescent light of the _rhizomorpha phosphoreus_, a peculiar
fungus. On the leaves of the Pindoba palm grows a species of agaric
which is exceedingly luminous at night; and many varieties of the
lichens, creeping along the roofs of caverns, lend to them an air of
enchantment by the soft and clear light which they diffuse. In a small
cave near Penryn, a luminous moss is abundant; it is also found in the
mines of Hesse. According to Heinzmann, the _rhizomorpha subterranea_
and _aidulæ_ are also phosphorescent.--See _Poetry of Science_.


PHOSPHORESCENCE OF THE SEA.

By microscopic examination of the myriads of minute insects which cause
this phenomenon, no other fact has been elicited than that they contain
a fluid which, when squeezed out, leaves a train of light upon the
surface of the water. The creatures appear almost invariably on the eve
of some change of weather, which would lead us to suppose that their
luminous phenomena must be connected with electrical excitation; and of
this Mr. C. Peach of Fowey has furnished the most satisfactory proofs
yet obtained.[13]


LIGHT FROM THE JUICE OF A PLANT.

In Brazil has been observed a plant, conjectured to be an Euphorbium,
very remarkable for the light which it yields when cut. It contains a
milky juice, which exudes as soon as the plant is wounded, and appears
luminous for several seconds.


LIGHT FROM FUNGUS.

Phosphorescent funguses have been found in Brazil by Mr. Gardner,
growing on the decaying leaves of a dwarf palm. They vary from one to
two inches across, and the whole plant gives out at night a bright
phosphorescent light, of a pale greenish hue, similar to that emitted
by fire-flies and phosphorescent marine animals. The light given out by
a few of these fungi in a dark room is sufficient to read by. A very
large phosphorescent species is occasionally found in the Swan River
colony.


LIGHT FROM BUTTONS.

Upon highly polished gilt buttons no figure whatever can be seen by the
most careful examination; yet, when they are made to reflect the light
of the sun or of a candle upon a piece of paper held close to them,
they give a beautiful geometrical figure, with ten rays issuing from
the centre, and terminating in a luminous rim.


COLOURS OF SCRATCHES.

An extremely fine scratch on a well-polished surface may be regarded as
having a concave, cylindrical, or at least a curved surface, capable of
reflecting light in all directions; this is evident, for it is visible
in all directions. Hence a single scratch or furrow in a surface may
produce colours by the interference of the rays reflected from its
opposite edges. Examine a spider’s thread in the sunshine, and it will
gleam with vivid colours. These may arise from a similar cause; or from
the thread itself, as spun by the animal, consisting of several threads
agglutinated together, and thus presenting, not a cylindrical, but a
furrowed surface.


MAGIC BUST.

Sir David Brewster has shown how the rigid features of a white bust
may be made to move and vary their expression, sometimes smiling and
sometimes frowning, by moving rapidly in front of the bust a bright
light, so as to make the lights and shadows take every possible
direction and various degrees of intensity; and if the bust be placed
before a concave mirror, its image may be made to do still more when it
is cast upon wreaths of smoke.


COLOURS HIT MOST FREQUENTLY DURING BATTLE.

It would appear from numerous observations that soldiers are hit
during battle according to the colour of their dress in the following
order: red is the most fatal colour; the least fatal, Austrian gray.
The proportions are, red, 12; rifle-green, 7; brown, 6; Austrian
bluish-gray, 5.--_Jameson’s Journal_, 1853.


TRANSMUTATION OF TOPAZ.

Yellow topazes may be converted into pink by heat; but it is a mistake
to suppose that in the process the yellow colour is changed into pink:
the fact is, that one of the pencils being yellow and the other pink,
the yellow is discharged by heat, thus leaving the pink unimpaired.


COLOURS AND TINTS.

M. Chevreul, the _Directeur des Gobelins_, has presented to the French
Academy a plan for a universal chromatic scale, and a methodical
classification of all imaginable colours. Mayer, a professor at
Göttingen, calculated that the different combinations of primitive
colours produced 819 different tints; but M. Chevreul established not
less than 14,424, all very distinct and easily recognised,--all of
course proceeding from the three primitive simple colours of the solar
spectrum, red, yellow, and blue. For example, he states that in the
violet there are twenty-eight colours, and in the dahlia forty-two.


OBJECTS REALLY OF NO COLOUR.

A body appears to be of the colour which it reflects; as we see it only
by reflected rays, it can but appear of the colour of those rays. Thus
grass is green because it absorbs all except the green rays. Flowers,
in the same manner, reflect the various colours of which they appear
to us: the rose, the red rays; the violet, the blue; the daffodil,
the yellow, &c. But these are not the permanent colours of the grass
and flowers; for wherever you see these colours, the objects must be
illuminated; and light, from whatever source it proceeds, is of the
same nature, composed of the various coloured rays which paint the
grass, the flowers, and every coloured object in nature. Objects in
the dark have no colour, or are black, which is the same thing. You
can never see objects without light. Light is composed of colours,
therefore there can be no light without colours; and though every
object is black or without colour in the dark, it becomes coloured as
soon as it becomes visible.


THE DIORAMA--WHY SO PERFECT AN ILLUSION.

Because when an object is viewed at so great a distance that the
optic axes of both eyes are sensibly parallel when directed towards
it, the perspective projections of it, seen by each eye separately,
are similar; and the appearance to the two eyes is precisely the same
as when the object is seen by one eye only. There is, in such case,
no difference between the visual appearance of an object in relief
and its perspective projection on a plane surface; hence pictorial
representations of distant objects, when those circumstances which
would prevent or disturb the illusion are carefully excluded, may be
rendered such perfect resemblances of the objects they are intended to
represent as to be mistaken for them. The Diorama is an instance of
this.--_Professor Wheatstone_; _Philosophical Transactions_, 1838.


CURIOUS OPTICAL EFFECTS AT THE CAPE.

Sir John Herschel, in his observatory at Feldhausen, at the base of
the Table Mountain, witnessed several curious optical effects, arising
from peculiar conditions of the atmosphere incident to the climate of
the Cape. In the hot season “the nights are for the most part superb;”
but occasionally, during the excessive heat and dryness of the sandy
plains, “the optical tranquillity of the air” is greatly disturbed.
In some cases, the images of the stars are violently dilated into
nebular balls or puffs of 15′ in diameter; on other occasions they
form “soft, round, quiet pellets of 3′ or 4′ diameter,” resembling
planetary nebulæ. In the cooler months the tranquillity of the image
and the sharpness of vision are such, that hardly any limit is set
to magnifying power but that which arises from the aberration of the
specula. On occasions like these, optical phenomena of extraordinary
splendour are produced by viewing a bright star through a diaphragm
of cardboard or zinc pierced in regular patterns of circular holes by
machinery: these phenomena surprise and delight every person that sees
them. When close double stars are viewed with the telescope, with a
diaphragm in the form of an equilateral triangle, the discs of the two
stars, which are exact circles, have a clearness and perfection almost
incredible.


THE TELESCOPE AND THE MICROSCOPE.

So singular is the position of the Telescope and the Microscope among
the great inventions of the age, that no other process but that which
they embody could make the slightest approximation to the secrets which
they disclose. The steam-engine might have been imperfectly replaced
by an air or an ether-engine; and a highly elastic fluid might have
been, and may yet be, found, which shall impel the “rapid car,” or
drag the merchant-ship over the globe. The electric telegraph, now so
perfect and unerring, might have spoken to us in the rude “language
of chimes;” or sound, in place of electricity, might have passed along
the metallic path, and appealed to the ear in place of the eye. For
the printing-press and the typographic art might have been found a
substitute, however poor, in the lithographic process; and knowledge
might have been widely diffused by the photographic printing powers
of the sun, or even artificial light. But without the telescope and
the microscope, the human eye would have struggled in vain to study
the worlds beyond our own, and the elaborate structures of the organic
and inorganic creation could never have been revealed.--_North-British
Review_, No. 50.


INVENTION OF THE MICROSCOPE.

The earliest magnifying lens of which we have any knowledge was one
rudely made of rock-crystal, which Mr. Layard found, among a number
of glass bowls, in the north-west palace of Nimroud; but no similar
lens has been found or described to induce us to believe that the
microscope, either single or compound, was invented and used as an
instrument previous to the commencement of the seventeenth century.
In the beginning of the first century, however, Seneca alludes to the
magnifying power of a glass globe filled with water; but as he only
states that it made small and indistinct letters appear larger and more
distinct, we cannot consider such a casual remark as the invention of
the single microscope, though it might have led the observer to try the
effect of smaller globes, and thus obtain magnifying powers sufficient
to discover phenomena otherwise invisible.

Lenses of glass were undoubtedly in existence at the time of Pliny;
but at that period, and for many centuries afterwards, they appear
to have been used only as burning or as reading glasses; and no
attempt seems to have been made to form them of so small a size as
to entitle them to be regarded even as the precursors of the single
microscope.--_North-British Review_, No. 50.

  The _rock-crystal lens_ found at Nineveh was examined by Sir
  David Brewster. It was not entirely circular in its aperture. Its
  general form was that of a plano-convex lens, the plane side having
  been formed of one of the original faces of the six-sided crystal
  quartz, as Sir David ascertained by its action on polarised light:
  this was badly polished and scratched. The convex face of the lens
  had not been ground in a dish-shaped tool, in the manner in which
  lenses are now formed, but was shaped on a lapidary’s wheel, or in
  some such manner. Hence it was unequally thick; but its extreme
  thickness was 2/10ths of an inch, its focal length being 4½ inches.
  It had twelve remains of cavities, which had originally contained
  liquids or condensed gases. Sir David has assigned reasons why this
  could not be looked upon as an ornament, but a true optical lens.
  In the same ruins were found some decomposed glass.


HOW TO MAKE THE FISH-EYE MICROSCOPE.

Very good microscopes may be made with the crystalline lenses of
fish, birds, and quadrupeds. As the lens of fishes is spherical or
spheroidal, it is absolutely necessary, previous to its use, to
determine its optical axis and the axis of vision of the eye from which
it is taken, and place the lens in such a manner that its axis is a
continuation of the axis of our own eye. In no other direction but this
is the albumen of which the lens consists symmetrically disposed in
laminæ of equal density round a given line, which is the axis of the
lens; and in no other direction does the gradation of density, by which
the spherical aberration is corrected, preserve a proper relation to
the axis of vision.

  When the lens of any small fish, such as a minnow, a par, or trout,
  has been taken out, along with the adhering vitreous humour, from
  the eye-ball by cutting the sclerotic coat with a pair of scissors,
  it should be placed upon a piece of fine silver-paper previously
  freed from its minute adhering fibres. The absorbent nature of
  the paper will assist in removing all the vitreous humour from
  the lens; and when this is carefully done, by rolling it about
  with another piece of silver-paper, there will still remain,
  round or near the equator of the lens, a black ridge, consisting
  of the processes by which it was suspended in the eye-ball. The
  black circle points out to us the true axis of the lens, which
  is perpendicular to a plane passing through it. When the small
  crystalline has been freed from all the adhering vitreous humour,
  the capsule which contains it will have a surface as fine as a
  pellicle of fluid. It is then to be dropped from the paper into a
  cavity formed by a brass rim, and its position changed till the
  black circle is parallel to the circular rim, in which case only
  the axis of the lens will be a continuation of the axis of the
  observer’s eye.--_Edin. Jour. Science_, vol. ii.


LEUWENHOECK’S MICROSCOPES.

Leuwenhoeck, the father of microscopical discovery, communicated to the
Royal Society, in 1673, a description of the structure of a bee and a
louse, seen by aid of his improved microscopes; and from this period
until his decease in 1723, he regularly transmitted to the society his
microscopical observations and discoveries, so that 375 of his papers
and letters are preserved in the society’s archives, extending over
fifty years. He further bequeathed to the Royal Society a cabinet of
twenty-six microscopes, which he had ground himself and set in silver,
mostly extracted by him from minerals; these microscopes were exhibited
to Peter the Great when he was at Delft in 1698. In acknowledging
the bequest, the council of the Royal Society, in 1724, presented
Leuwenhoeck’s daughter with a handsome silver bowl, bearing the arms of
the society.--_Weld’s History of the Royal Society_, vol. i.


DIAMOND LENSES FOR MICROSCOPES.

In recommending the employment of Diamond and other gems in the
construction of Microscopes, Sir David Brewster has been met with
the objection that they are too expensive for such a purpose; and,
says Sir David, “they certainly are for instruments intended merely
to instruct and amuse. But if we desire to make great discoveries,
to unfold secrets yet hid in the cells of plants and animals, we
must not grudge even a diamond to reveal them. If Mr. Cooper and Sir
James South have given a couple of thousand pounds a piece for a
refracting telescope, in order to study what have been miscalled ‘dots’
and ‘lumps’ of light on the sky; and if Lord Rosse has expended far
greater sums on a reflecting telescope for analysing what has been
called ‘sparks of mud and vapour’ encumbering the azure purity of the
heavens,--why should not other philosophers open their purse, if they
have one, and other noblemen sacrifice some of their household jewels,
to resolve the microscopic structures of our own real world, and
disclose secrets which the Almighty must have intended that we should
know?”--_Proceedings of the British Association_, 1857.


THE EYE AND THE BRAIN SEEN THROUGH A MICROSCOPE.

By a microscopic examination of the retina and optic nerve and
the brain, M. Bauer found them to consist of globules of 1/2800th
to 1/4000th an inch diameter, united by a transparent viscid and
coagulable gelatinous fluid.


MICROSCOPICAL EXAMINATION OF THE HAIR.

If a hair be drawn between the finger and thumb, from the end to
the root, it will be distinctly felt to give a greater resistance
and a different sensation to that which is experienced when drawn
the opposite way: in consequence, if the hair be rubbed between the
fingers, it will only move one way (travelling in the direction of a
line drawn from its termination to its origin from the head or body),
so that each extremity may thus be easily distinguished, even in the
dark, by the touch alone.

The mystery is resolved by the achromatic microscope. A hair viewed on
a dark ground as an _opaque_ object with a high power, not less than
that of a lens of one-thirtieth of an inch focus, and dully illuminated
by a _cup_, the hair is seen to be indented with teeth somewhat
resembling those of a coarse round rasp, but extremely irregular and
rugged: as these incline all in one direction, like those of a common
file, viz. from the origin of the hair towards its extremity, it
sufficiently explains the above singular property.

This is a singular proof of the acuteness of the sense of feeling, for
the said teeth may be felt much more easily than they can be seen. We
may thus understand why a razor will cut a hair in two much more easily
when drawn against its teeth than in the opposite direction.--_Dr.
Goring._


THE MICROSCOPE AND THE SEA.

What myriads has the microscope revealed to us of the rich luxuriance
of animal life in the ocean, and conveyed to our astonished senses
a consciousness of the universality of life! In the oceanic depths
every stratum of water is animated, and swarms with countless hosts of
small luminiferous animalcules, mammaria, crustacea, peridinea, and
circling nereides, which, when attracted to the surface by peculiar
meteorological conditions, convert every wave into a foaming band of
flashing light.


USE OF THE MICROSCOPE TO MINERALOGISTS.

M. Dufour has shown that an imponderable quantity of a substance
can be crystallised; and that the crystals so obtained are quite
characteristic of the substances, as of sugar, chloride of sodium,
arsenic, and mercury. This process may be extremely valuable to the
mineralogist and toxicologist when the substance for examination is too
small to be submitted to tests. By aid of the microscope, also, shells
are measured to the thousandth part of an inch.


FINE DOWN OF QUARTZ.

Sir David Brewster having broken in two a crystal of quartz of a smoky
colour, found both surfaces of the fracture absolutely black; and the
blackness appeared at first sight to be owing to a thin film of opaque
matter which had insinuated itself into the crevice. This opinion,
however, was untenable, as every part of the surface was black, and
the two halves of the crystals could not have stuck together had the
crevice extended across the whole section. Upon further examination Sir
David found that the surface was perfectly transparent by transmitted
light, and that the blackness of the surfaces arose from their being
entirely composed of _a fine down of quartz_, or of short and slender
filaments, whose diameter was so exceedingly small that they were
incapable of reflecting a single ray of the strongest light; and they
could not exceed the _one third of the millionth part of an inch_. This
curious specimen is in the cabinet of her grace the Duchess of Gordon.


MICROSCOPIC WRITING.

Professor Kelland has shown, in Paris, on a spot no larger than
the head of a small pin, by means of powerful microscopes, several
specimens of distinct and beautiful writing, one of them containing
the whole of the Lord’s Prayer written within this minute compass.
In reference to this, two remarkable facts in Layard’s latest work
on Nineveh show that the national records of Assyria were written on
square bricks, in characters so small as scarcely to be legible without
a microscope; in fact, a microscope, as we have just shown, was found
in the ruins of Nimroud.


HOW TO MAKE A MAGIC MIRROR.

Draw a figure with weak gum-water upon the surface of a convex mirror.
The thin film of gum thus deposited on the outline or details of the
figure will not be visible in dispersed daylight; but when made to
reflect the rays of the sun, or those of a divergent pencil, will
be beautifully displayed by the lines and tints occasioned by the
diffraction of light, or the interference of the rays passing through
the film with those which pass by it.


SIR DAVID BREWSTER’S KALEIDOSCOPE.

The idea of this instrument, constructed for the purpose of creating
and exhibiting a variety of beautiful and perfectly symmetrical forms,
first occurred to Sir David Brewster in 1814, when he was engaged in
experiments on the polarisation of light by successive reflections
between plates of glass. The reflectors were in some instances inclined
to each other; and he had occasion to remark the circular arrangement
of the images of a candle round a centre, or the multiplication of the
sectors formed by the extremities of the glass plates. In repeating
at a subsequent period the experiments of M. Biot on the action of
fluids upon light, Sir David Brewster placed the fluids in a trough,
formed by two plates of glass cemented together at an angle; and the
eye being necessarily placed at one end, some of the cement, which had
been pressed through between the plates, appeared to be arranged into a
regular figure. The remarkable symmetry which it presented led to Dr.
Brewster’s investigation of the cause of this phenomenon; and in so
doing he discovered the leading principles of the Kaleidoscope.

By the advice of his friends, Dr. Brewster took out a patent for his
invention; in the specification of which he describes the kaleidoscope
in two different forms. The instrument, however, having been shown
to several opticians in London, became known before he could avail
himself of his patent; and being simple in principle, it was at once
largely manufactured. It is calculated that not less than 200,000
kaleidoscopes were sold in three months in London and Paris; though out
of this number, Dr. Brewster says, not perhaps 1000 were constructed
upon scientific principles, or were capable of giving any thing like a
correct idea of the power of his kaleidoscope.


THE KALEIDOSCOPE THOUGHT TO BE ANTICIPATED.

In the seventh edition of a work on gardening and planting, published
in 1739, by Richard Bradley, F.R.S., late Professor of Botany in the
University of Cambridge, we find the following details of an invention,
“by which the best designers and draughtsmen may improve and help
their fancies. They must choose two pieces of looking-glass of equal
bigness, of the figure of a long square. These must be covered on
the back with paper or silk, to prevent rubbing off the silver. This
covering must be so put on that nothing of it appears about the edges
of the bright side. The glasses being thus prepared, must be laid face
to face, and hinged together so that they may be made to open and shut
at pleasure like the leaves of a book.” After showing how various
figures are to be looked at in these glasses under the same opening,
and how the same figure may be varied under the different openings, the
ingenious artist thus concludes: “If it should happen that the reader
has any number of plans for parterres or wildernesses by him, he may by
this method alter them at his pleasure, and produce such innumerable
varieties as it is not possible the most able designer could ever have
contrived.”


MAGIC OF PHOTOGRAPHY.

Professor Moser of Königsberg has discovered that all bodies, even
in the dark, throw out invisible rays; and that these bodies, when
placed at a small distance from polished surfaces of all kinds, depict
themselves upon such surfaces in forms which remain invisible till
they are developed by the human breath or by the vapours of mercury or
iodine. Even if the sun’s image is made to pass over a plate of glass,
the light tread of its rays will leave behind it an invisible track,
which the human breath will instantly reveal.

  Among the early attempts to take pictures by the rays of the sun
  was a very interesting and successful experiment made by Dr. Thomas
  Young. In 1802, when Mr. Wedgewood was “making profiles by the
  agency of light,” and Sir Humphry Davy was “copying on prepared
  paper the images of small objects produced by means of the solar
  microscope,” Dr. Young was taking photographs upon paper dipped in
  a solution of nitrate of silver, of the coloured rings observed
  by Newton; and his experiments clearly proved that the agent was
  not the luminous rays in the sun’s light, but the invisible or
  chemical rays beyond the violet. This experiment is described in
  the Bakerian Lecture, 1803.

  Niepce (says Mr. Hunt) pursued a physical investigation of the
  curious change, and found that all bodies were influenced by this
  principle radiated from the sun. Daguerre[14] produced effects from
  the solar pencil which no artist could approach; and Talbot and
  others extended the application. Herschel took up the inquiry; and
  he, with his usual power of inductive search and of philosophical
  deduction, presented the world with a class of discoveries which
  showed how vast a field of investigation was opening for the
  younger races of mankind.

  The first attempts in photography, which were made at the
  instigation of M. Arago, by order of the French Government, to
  copy the Egyptian tombs and temples and the remains of the Aztecs
  in Central America, were failures. Although the photographers
  employed succeeded to admiration, in Paris, in producing pictures
  in a few minutes, they found often that an exposure of an hour
  was insufficient under the bright and glowing illumination of a
  southern sky.


THE BEST SKY FOR PHOTOGRAPHY.

Contrary to all preconceived ideas, experience proves that the brighter
the sky that shines above the camera the more tardy the action within
it. Italy and Malta do their work slower than Paris. Under the
brilliant light of a Mexican sun, half an hour is required to produce
effects which in England would occupy but a minute. In the burning
atmosphere of India, though photographical the year round, the process
is comparatively slow and difficult to manage; while in the clear,
beautiful, and moreover cool, light of the higher Alps of Europe, it
has been proved that the production of a picture requires many more
minutes, even with the most sensitive preparations, than in the murky
atmosphere of London. Upon the whole, the temperate skies of this
country may be pronounced favourable to photographic action; a fact
for which the prevailing characteristic of our climate may partially
account, humidity being an indispensable condition for the working
state both of paper and chemicals.--_Quarterly Review_, No. 202.


PHOTOGRAPHIC EFFECTS OF LIGHTNING.

The following authenticated instances of this singular phenomenon have
been communicated to the Royal Society by Andrés Poey, Director of the
Observatory at Havana:

  Benjamin Franklin, in 1786, stated that about twenty years
  previous, a man who was standing opposite a tree that had just been
  struck by “a thunderbolt” had on his breast an exact representation
  of that tree.

  In the New-York _Journal of Commerce_, August 26th, 1853, it is
  related that “a little girl was standing at a window, before which
  was a young maple-tree; after a brilliant flash of lightning, a
  complete image of the tree was found imprinted on her body.”

  M. Raspail relates that, in 1855, a boy having climbed a tree for
  the purpose of robbing a bird’s nest, the tree was struck, and
  the boy thrown upon the ground; on his breast the image of the
  tree, with the bird and nest on one of its branches, appeared very
  plainly.

  M. Olioli, a learned Italian, brought before the Scientific
  Congress at Naples the following four instances: 1. In September
  1825, the foremast of a brigantine in the Bay of St. Arniro
  was struck by lightning, when a sailor sitting under the mast
  was struck dead, and on his back was found an impression of a
  horse-shoe, similar even in size to that fixed on the mast-head. 2.
  A sailor, standing in a similar position, was struck by lightning,
  and had on his left breast the impression of the number 4 4, with a
  dot between the two figures, just as they appeared at the extremity
  of one of the masts. 3. On the 9th October 1836, a young man was
  found struck by lightning; he had on a girdle, with some gold
  coins in it, which were imprinted on his skin in the order they
  were placed in the girdle,--a series of circles, with one point of
  contact, being plainly visible. 4. In 1847, Mme. Morosa, an Italian
  lady of Lugano, was sitting near a window during a thunderstorm,
  and perceived the commotion, but felt no injury; but a flower which
  happened to be in the path of the electric current was perfectly
  reproduced on one of her legs, and there remained permanently.

  M. Poey himself witnessed the following instance in Cuba. On July
  24th, 1852, a poplar-tree in a coffee-plantation was struck by
  lightning, and on one of the large dry leaves was found an exact
  representation of some pine-trees that lay 367 yards distant.

M. Poey considers these lightning impressions to have been produced
in the same manner as the electric images obtained by Moser, Riess,
Karster, Grove, Fox Talbot, and others, either by statical or dynamical
electricity of different intensities. The fact that impressions are
made through the garments is easily accounted for by their rough
texture not preventing the lightning passing through them with the
impression. To corroborate this view, M. Poey mentions an instance of
lightning passing down a chimney into a trunk, in which was found an
inch depth of soot, which must have passed through the wood itself.


PHOTOGRAPHIC SURVEYING.

During the summer of 1854, in the Baltic, the British steamers employed
in examining the enemy’s coasts and fortifications took photographic
views for reference and minute examination. With the steamer moving
at the rate of fifteen knots an hour, the most perfect definitions of
coasts and batteries were obtained. Outlines of the coasts, correct in
height and distance, have been faithfully transcribed; and all details
of the fortresses passed under this photographic review are accurately
recorded.

  It is curious to reflect that the aids to photographic development
  all date within the last half-century, and are but little older
  than photography itself. It was not until 1811 that the chemical
  substance called iodine, on which the foundations of all popular
  photography rest, was discovered at all; bromine, the only other
  substance equally sensitive, not till 1826. The invention of the
  electro process was about simultaneous with that of photography
  itself. Gutta-percha only just preceded the substance of which
  collodion is made; the ether and chloroform, which are used in
  some methods, that of collodion. We say nothing of the optical
  improvements previously contrived or adapted for the purpose of the
  photograph: the achromatic lenses, which correct the discrepancy
  between the visual and chemical foci; the double lenses, which
  increase the force of the action; the binocular lenses, which
  do the work of the stereoscope; nor of the innumerable other
  mechanical aids which have sprung up for its use.


THE STEREOSCOPE AND THE PHOTOGRAPH.

When once the availability of one great primitive agent is worked out,
it is easy to foresee how extensively it will assist in unravelling
other secrets in natural science. The simple principle of the
Stereoscope, for instance, might have been discovered a century ago,
for the reasoning which led to it was independent of all the properties
of light; but it could never have been illustrated, far less multiplied
as it now is, without Photography. A few diagrams, of sufficient
identity and difference to prove the truth of the principle, might
have been constructed by hand, for the gratification of a few sages;
but no artist, it is to be hoped, could have been found possessing
the requisite ability and stupidity to execute the two portraits, or
two groups, or two interiors, or two landscapes, identical in every
minutia of the most elaborate detail, and yet differing in point of
view by the inch between the two human eyes, by which the principle is
brought to the level of any capacity. Here, therefore, the accuracy and
insensibility of a machine could alone avail; and if in the order of
things the cheap popular toy which the stereoscope now represents was
necessary for the use of man, the photograph was first necessary for
the service of the stereoscope.--_Quarterly Review_, No. 202.


THE STEREOSCOPE SIMPLIFIED.

When we look at any round object, first with one eye, and then with
the other, we discover that with the right eye we see most of the
right-hand side of the object, and with the left eye most of the
left-hand side. These two images are combined, and we see an object
which we know to be round.

This is illustrated by the _Stereoscope_, which consists of two mirrors
placed each at an angle of 45 deg., or of two semi-lenses turned with
their curved sides towards each other. To view its phenomena two
pictures are obtained by the camera on photographic paper of any object
in two positions, corresponding with the conditions of viewing it with
the two eyes. By the mirrors on the lenses these dissimilar pictures
are combined within the eye, and the vision of an actually solid object
is produced from the pictures represented on a plane surface. Hence the
name of the instrument, which signifies _Solid I see_.--_Hunt’s Poetry
of Science._


PHOTO-GALVANIC ENGRAVING.

That which was the chief aid of Niepce in the humblest dawn of the
art, viz. to transform the photographic plate into a surface capable
of being printed, is in the above process done by the coöperation of
Electricity with Photography. This invention of M. Pretsch, of Vienna,
differs from all other attempts for the same purpose in not operating
upon the photographic tablet itself, and by discarding the usual means
of varnishes and bitings-in. The process is simply this: A glass tablet
is coated with gelatine diluted till it forms a jelly, and containing
bi-chromate of potash, nitrate of silver, and iodide of potassium. Upon
this, when dry, is placed face downwards a paper positive, through
which the light, being allowed to fall, leaves upon the gelatine a
representation of the print. It is then soaked in water; and while
the parts acted upon by the light are comparatively unaffected by the
fluid, the remainder of the jelly swells, and rising above the general
surface, gives a picture in relief, resembling an ordinary engraving
upon wood. Of this intaglio a cast is now taken in gutta-percha, to
which the electro process in copper being applied, a plate or matrix is
produced, bearing on it an exact repetition of the original positive
picture. All that now remains to be done is to repeat the electro
process; and the result is a copper-plate in the necessary relievo, of
which it has been said nature furnished the materials and science the
artist, the inferior workman being only needed to roll it through the
press.--_Quarterly Review_, No. 202.


SCIENCE OF THE SOAP-BUBBLE.

Few of the minor ingenuities of mankind have amused so many individuals
as the blowing of bubbles with soap-lather from the bowl of a
tobacco-pipe; yet how few who in childhood’s careless hours have thus
amused themselves, have in after-life become acquainted with the
beautiful phenomena of light which the soap-bubble will enable us to
illustrate!

Usually the bubble is formed within the bowl of a tobacco-pipe, and
so inflated by blowing through the stem. It is also produced by
introducing a capillary tube under the surface of soapy water, and so
raising a bubble, which may be inflated to any convenient size. It is
then guarded with a glass cover, to prevent its bursting by currents of
air, evaporation, and other causes.

When the bubble is first blown, its form is elliptical, into which it
is drawn by its gravity being resisted; but the instant it is detached
from the pipe, and allowed to float in air, it becomes a perfect
sphere, since the air within presses equally in all directions. There
is also a strong cohesive attraction in the particles of soap and
water, after having been forcibly distended; and as a sphere or globe
possesses less surface than any other figure of equal capacity, it is
of all forms the best adapted to the closest approximation of the
particles of soap and water, which is another reason why the bubble
is globular. The film of which the bubble consists is inconceivably
thin (not exceeding the two-millionth part of an inch); and by the
evaporation from its surface, the contraction and expansion of the air
within, and the tendency of the soap-lather to gravitate towards the
lower part of the bubble, and consequently to render the upper part
still thinner, it follows that the bubble lasts but a few seconds. If,
however, it were blown in a glass vessel, and the latter immediately
closed, it might remain for some time; Dr. Paris thus preserved a
bubble for a considerable period.

Dr. Hooke, by means of the coloured rings upon the soap-bubble, studied
the curious subject of the colours of thin plates, and its application
to explain the colours of natural bodies. Various phenomena were also
discovered by Newton, who thus did not disdain to make a soap-bubble
the object of his study. The colours which are reflected from the upper
surface of the bubble are caused by the decomposition of the light
which falls upon it; and the range of the phenomena is alike extensive
and beautiful.[15]

Newton (says Sir D. Brewster), having covered the soap-bubble with a
glass shade, saw its colours emerge in regular order, like so many
concentric rings encompassing the top of it. As the bubble grew thinner
by the continual subsidence of the water, the rings dilated slowly,
and overspread the whole of it, descending to the bottom, where they
vanished successively. When the colours had all emerged from the top,
there arose in the centre of the rings a small round black spot,
dilating it to more than half an inch in breadth till the bubble
burst. Upon examining the rings between the object-glasses, Newton
found that when they were only _eight_ or _nine_ in number, more than
_forty_ could be seen by viewing them through a prism; and even when
the plate of air seemed all over uniformly white, multitudes of rings
were disclosed by the prism. By means of these observations Newton was
enabled to form his _Scale of Colours_, of great value in all optical
researches.

Dr. Reade has thus produced a permanent soap-bubble:

  Put into a six-ounce phial two ounces of distilled water, and set
  the phial in a vessel of water boiling on the fire. The water in
  the phial will soon boil, and steam will issue from its mouth,
  expelling the whole of the atmospheric air from within. Then throw
  in a piece of soap about the size of a small pea, cork the phial,
  and at the same instant remove it and the vessel from the fire.
  Then press the cork farther into the neck of the phial, and cover
  it thickly with sealing-wax; and when the contents are cold, a
  perfect vacuum will be formed within the bottle,--much better,
  indeed, than can be produced by the best-constructed air-pump.

  To form a bubble, hold the bottle horizontally in both hands, and
  give it a sudden upward motion, which will throw the liquid into a
  wave, whose crest touching the upper interior surface of the phial,
  the tenacity of the liquid will cause a film to be retained all
  round the phial. Next place the phial on its bottom; when the film
  will form a section of the cylinder, being nearly but never quite
  horizontal. The film will be now colourless, since it reflects all
  the light which falls upon it. By remaining at rest for a minute or
  two, minute currents of lather will descend by their gravitating
  force down the inclined plane formed by the film, the upper part of
  which thus becomes drained to the necessary thinness; and this is
  the part to be observed.

Several concentric segments of coloured rings are produced; the
colours, beginning from the top, being as follows:

    _1st order_: Black, white, yellow, orange, red.
    _2d order_: Purple, blue, white, yellow, red.
    _3d order_: Purple, blue, green, yellowish-green, white, red.
    _4th order_: Purple, blue, green, white, red.
    _5th order_: Greenish-blue, very pale red.
    _6th order_: Greenish-blue, pink.
    _7th order_: Greenish-blue, pink.

As the segments advance they get broader, while the film becomes
thinner and thinner. The several orders disappear upwards as the film
becomes too thin to reflect their colours, until the first order alone
remains, occupying the whole surface of the film. Of this order the
red disappears first, then the orange, and lastly the yellow. The film
is now divided by a line into two nearly equal portions, one black and
the other white. This remains for some time; at length the film becomes
too thin to hold together, and then vanishes. The colours are not faint
and imperfect, but well defined, glowing with gorgeous hues, or melting
into tints so exquisite as to have no rival through the whole circle
of the arts. We quote these details from Mr. Tomlinson’s excellent
_Student’s Manual of Natural Philosophy_.

  We find the following anecdote related of Newton at the above
  period. When Sir Isaac changed his residence, and went to live in
  St. Martin’s Street, Leicester Square, his next-door neighbour was
  a widow lady, who was much puzzled by the little she observed of
  the habits of the philosopher. A Fellow of the Royal Society called
  upon her one day, when, among her domestic news, she mentioned that
  some one had come to reside in the adjoining house who, she felt
  certain, was a poor crazy gentleman, “because,” she continued,
  “he diverts himself in the oddest way imaginable. Every morning,
  when the sun shines so brightly that we are obliged to draw the
  window-blinds, he takes his seat on a little stool before a tub
  of soapsuds, and occupies himself for hours blowing soap-bubbles
  through a common clay-pipe, which bubbles he intently watches
  floating about till they burst. He is doubtless,” she added, “now
  at his favourite amusement, for it is a fine day; do come and look
  at him.” The gentleman smiled, and they went upstairs; when, after
  looking through the staircase-window into the adjoining court-yard,
  he turned and said: “My dear madam, the person whom you suppose
  to be a poor lunatic is no other than the great Sir Isaac Newton
  studying the refraction of light upon thin plates; a phenomenon
  which is beautifully exhibited on the surface of a common
  soap-bubble.”


LIGHT FROM QUARTZ.

Among natural phenomena (says Sir David Brewster) illustrative of the
colours of thin plates, we find none more remarkable than one exhibited
by the fracture of a large crystal of quartz of a smoky colour, and
about two and a quarter inches in diameter. The surface of fracture,
in place of being a face or cleavage, or irregularly conchoidal, as we
have sometimes seen it, was filamentous, like a surface of velvet, and
consisted of short fibres, so small as to be incapable of reflecting
light. Their size could not have been greater than the third of the
millionth part of an inch, or one-fourth of the thinnest part of the
soap-bubble when it exhibits the black spot where it bursts.


CAN THE CAT SEE IN THE DARK?

No, in all probability, says the reader; but the opposite popular
belief is supported by eminent naturalists.

  Buffon says: “The eyes of the cat shine in the dark somewhat like
  diamonds, which throw out during the night the light with which
  they were in a manner impregnated during the day.”

  Valmont de Bamare says: “The pupil of the cat is during the night
  still deeply imbued with the light of the day;” and again, “the
  eyes of the cat are during the night so imbued with light that they
  then appear very shining and luminous.”

  Spallanzani says: “The eyes of cats, polecats, and several other
  animals, shine in the dark like two small tapers;” and he adds that
  this light is phosphoric.

  Treviranus says: “The eyes of the cat _shine where no rays of
  light penetrate_; and the light must in many, if not in all, cases
  proceed from the eye itself.”

Now, that the eyes of the cat do shine in the dark is to a certain
extent true: but we have to inquire whether by _dark_ is meant the
entire absence of light; and it will be found that the solution of this
question will dispose of several assertions and theories which have for
centuries perplexed the subject.

Dr. Karl Ludwig Esser has published in Karsten’s Archives the results
of an experimental inquiry on the luminous appearance of the eyes of
the cat and other animals, carefully distinguishing such as evolve
light from those which only reflect it. Having brought a cat into a
half-darkened room, he observed from a certain direction that the cat’s
eyes, when _opposite the window_, sparkled brilliantly; but in other
positions the light suddenly vanished. On causing the cat to be held
so as to exhibit the light, and then gradually darkening the room, the
light disappeared by the time the room was made quite dark.

In another experiment, a cat was placed opposite the window in a
darkened room. A few rays were permitted to enter, and by adjusting the
light, one or both of the cat’s eyes were made to shine. In proportion
as the pupil was dilated, the eyes were brilliant. By suddenly
admitting a strong glare of light into the room, the pupil contracted;
and then suddenly darkening the room, the eye exhibited a small round
luminous point, which enlarged as the pupil dilated.

The eyes of the cat sparkle most when the animal is in a lurking
position, or in a state of irritation. Indeed, the eyes of all animals,
as well as of man, appear brighter when in rage than in a quiescent
state, which Collins has commemorated in his Ode on the Passions:

    “Next Anger rushed, his eyes on fire.”

This brilliancy is said to arise from an increased secretion of the
lachrymal fluid on the surface of the eye, by which the reflection of
the light is increased. Dr. Esser, in places absolutely dark, never
discovered the slightest trace of light in the eye of the cat; and he
has no doubt that in all cases where cats’ eyes have been seen to shine
in dark places, such as a cellar, light penetrated through some window
or aperture, and fell upon the eyes of the animal as it turned towards
the opening, while the observer was favourably situated to obtain a
view of the reflection.

To prove more clearly that this light does not depend upon the will of
the animal, nor upon its angry passions, experiments were made upon
the head of a dead cat. The sun’s rays were admitted through a small
aperture; and falling immediately upon the eyes, caused them to glow
with a beautiful green light more vivid even than in the case of a
living animal, on account of the increased dilatation of the pupil.
It was also remarked that black and fox-coloured cats gave a brighter
light than gray and white cats.

To ascertain the cause of this luminous appearance Dr. Esser dissected
the eyes of cats, and exposed them to a small regulated amount of light
after having removed different portions. The light was not diminished
by the removal of the cornea, but only changed in colour. The light
still continued after the iris was displaced; but on taking away the
crystalline lens it greatly diminished both in intensity and colour.
Dr. Esser then conjectured that the tapetum in the hinder part of the
eye must form a spot which caused the reflection of the incident
rays of light, and thus produce the shining; and this appeared more
probable as the light of the eye now seemed to emanate from a single
spot. Having taken away the vitreous humour, Dr. Esser observed that
the entire want of the pigment in the hinder part of the choroid coat,
where the optic nerve enters, formed a greenish, silver-coloured,
changeable oblong spot, which was not symmetrical, but surrounded the
optic nerve so that the greater part was above and only the smaller
part below it; wherefore the greater part lay beyond the axis of
vision. It is this spot, therefore, that produces the reflection of the
incident rays of light, and beyond all doubt, according to its tint,
contributes to the different colouring of the light.

It may be as well to explain that the interior of the eye is coated
with a black pigment, which has the same effect as the black colour
given to the inner surface of optical instruments: it absorbs any
rays of light that may be reflected within the eye, and prevents
them from being thrown again upon the retina so as to interfere with
the distinctness of the images formed upon it. The retina is very
transparent; and if the surface behind it, instead of being of a dark
colour, were capable of reflecting light, the luminous rays which had
already acted on the retina would be reflected back again through it,
and not only dazzle from excess of light, but also confuse and render
indistinct the images formed on the retina. Now in the case of the cat
this black pigment, or a portion of it, is wanting; and those parts of
the eye from which it is absent, having either a white or a metallic
lustre, are called the tapetum. The smallest portion of light entering
from it is reflected as by a concave mirror; and hence it is that the
eyes of animals provided with this structure are luminous in a very
faint light.

These experiments and observations show that the shining of the eyes
of the cat does not arise from a phosphoric light, but only from a
reflected light; that consequently it is not an effect of the will of
the animal, or of violent passions; that their shining does not appear
in absolute darkness; and that it cannot enable the animal to move
securely in the dark.

It has been proved by experiment that there exists a set of rays of
light of far higher refrangibility than those seen in the ordinary
Newtonian spectrum. Mr. Hunt considers it probable that these highly
refrangible rays, although under ordinary circumstances invisible
to the human eye, may be adapted to produce the necessary degree
of excitement upon which vision depends in the optic nerves of the
night-roaming animals. The bat, the owl, and the cat may see in the
gloom of the night by the aid of rays which are invisible to, or
inactive on, the eyes of man or those animals which require the light
of day for perfect vision.




Astronomy.


THE GREAT TRUTHS OF ASTRONOMY.

The difficulty of understanding these marvellous truths has been
glanced at by an old divine (see _Things not generally Known_, p.
1); but the rarity of their full comprehension by those unskilled in
mathematical science is more powerfully urged by Lord Brougham in these
cogent terms:

  Satisfying himself of the laws which regulate the mutual actions
  of the planetary bodies, the mathematician can convince himself of
  a truth yet more sublime than Newton’s discovery of gravitation,
  though flowing from it; and must yield his assent to the marvellous
  position, that all the irregularities occasioned in the system
  of the universe by the mutual attraction of its members are
  periodical, and subject to an eternal law, which prevents them from
  ever exceeding a stated amount, and secures through all time the
  balanced structure of a universe composed of bodies whose mighty
  bulk and prodigious swiftness of motion mock the utmost efforts
  of the human imagination. All these truths are to the skilful
  mathematician as thoroughly known, and their evidence is as clear,
  as the simplest proposition of arithmetic to common understandings.
  But how few are those who thus know and comprehend them! Of all
  the millions that thoroughly believe these truths, certainly not a
  thousand individuals are capable of following even any considerable
  portion of the demonstrations upon which they rest; and probably
  not a hundred now living have ever gone through the whole steps
  of these demonstrations.--_Dissertations on Subjects of Science
  connected with Natural Theology_, vol. ii.

Sir David Brewster thus impressively illustrates the same subject:

  Minds fitted and prepared for this species of inquiry are
  capable of appreciating the great variety of evidence by
  which the truths of the planetary system are established; but
  thousands of individuals, and many who are highly distinguished
  in other branches of knowledge, are incapable of understanding
  such researches, and view with a sceptical eye the great and
  irrefragable truths of astronomy.

  That the sun is stationary in the centre of our system; that
  the earth moves round the sun, and round its own axis; that
  the diameter of the earth is 8000 miles, and that of the sun
  _one hundred and ten times as great_; that the earth’s orbit is
  190,000,000 of miles in breadth; and that if this immense space
  were filled with light, it would appear only like a luminous point
  at the nearest fixed star,--are positions absolutely unintelligible
  and incredible to all who have not carefully studied the subject.
  To millions of our species, then, the great Book of Nature is
  absolutely sealed; though it is in the power of all to unfold its
  pages, and to peruse those glowing passages which proclaim the
  power and wisdom of its Author.


ASTRONOMY AND DATES ON MONUMENTS.

Astronomy is a useful aid in discovering the Dates of ancient
Monuments. Thus, on the ceiling of a portico among the ruins of
Tentyris are the twelve signs of the Zodiac, placed according to the
apparent motion of the sun. According to this Zodiac, the summer
solstice is in Leo; from which it is easy to compute, by the precession
of the equinoxes of 50″·1 annually, that the Zodiac of Tentyris must
have been made 4000 years ago.

Mrs. Somerville relates that she once witnessed the ascertainment of
the date of a Papyrus by means of astronomy. The manuscript was found
in Egypt, in a mummy-case; and its antiquity was determined by the
configuration of the heavens at the time of its construction. It proved
to be a horoscope of the time of Ptolemy.


“THE CRYSTAL VAULT OF HEAVEN.”

This poetic designation dates back as far as the early period of
Anaximenes; but the first clearly defined signification of the idea on
which the term is based occurs in Empedocles. This philosopher regarded
the heaven of the fixed stars as a solid mass, formed from the ether
which had been rendered crystalline by the action of fire.

In the Middle Ages, the fathers of the Church believed the firmament to
consist of from seven to ten glassy strata, incasing each other like
the different coatings of an onion. This supposition still keeps its
ground in some of the monasteries of southern Europe, where Humboldt
was greatly surprised to hear a venerable prelate express an opinion in
reference to the fall of aerolites at Aigle, that the bodies we called
meteoric stones with vitrified crusts were not portions of the fallen
stone itself, but simply fragments of the crystal vault shattered by it
in its fall.

Empedocles maintained that the fixed stars were riveted to the
crystal heavens; but that the planets were free and unconstrained.
It is difficult to conceive how, according to Plato in the _Timæus_,
the fixed stars, riveted as they are to solid spheres, could rotate
independently.

Among the ancient views, it may be mentioned that the equal distance
at which the stars remained, while the whole vault of heaven seemed to
move from east to west, had led to the idea of a firmament and a solid
crystal sphere, in which Anaximenes (who was probably not much later
than Pythagoras) had conjectured that the stars were riveted like nails.


MUSIC OF THE SPHERES.

The Pythagoreans, in applying their theory of numbers to the
geometrical consideration of the five regular bodies, to the musical
intervals of tone which determine a word and form different kinds
of sounds, extended it even to the system of the universe itself;
supposing that the moving, and, as it were, vibrating planets, exciting
sound-waves, must produce a _spheral music_, according to the harmonic
relations of their intervals of space. “This music,” they add, “would
be perceived by the human ear, if it was not rendered insensible by
extreme familiarity, as it is perpetual, and men are accustomed to it
from childhood.”

  The Pythagoreans affirm, in order to justify the reality of the
  tones produced by the revolution of the spheres, that hearing takes
  place only where there is an alternation of sound and silence. The
  inaudibility of the spheral music is also accounted for by its
  overpowering the senses. Aristotle himself calls the Pythagorean
  tone-myth pleasing and ingenious, but untrue.

Plato attempted to illustrate the tones of the universe in an
agreeable picture, by attributing to each of the planetary spheres a
syren, who, supported by the stern daughters of Necessity, the three
Fates, maintain the eternal revolution of the world’s axis. Mention
is constantly made of the harmony of the spheres, though generally
reproachfully, throughout the writings of Christian antiquity and the
Middle Ages, from Basil the Great to Thomas Aquinas and Petrus Alliacus.

At the close of the sixteenth century, Kepler revived these musical
ideas, and sought to trace out the analogies between the relations of
tone and the distances of the planets; and Tycho Brahe was of opinion
that the revolving conical bodies were capable of vibrating the
celestial air (what we now call “resisting medium”) so as to produce
tones. Yet Kepler, although he had talked of Venus and the Earth
sounding sharp in aphelion and flat in perihelion, and the highest tone
of Jupiter and that of Venus coinciding in flat accord, positively
declared there to be “no such things as sounds among the heavenly
bodies, nor is their motion so turbulent as to elicit noise from the
attrition of the celestial air.” (See _Things not generally Known_, p.
44.)


“MORE WORLDS THAN ONE.”

Although this opinion was maintained incidentally by various writers
both on astronomy[16] and natural religion, yet M. Fontenelle was the
first individual who wrote a treatise on the _Plurality of Worlds_,
which appeared in 1685, the year before the publication of Newton’s
_Principia_. Fontenelle’s work consists of five chapters: 1. The earth
is a planet which turns round its axis, and also round the sun. 2. The
moon is a habitable world. 3. Particulars concerning the world in the
moon, and that the other planets are also inhabited. 4. Particulars of
the worlds of Venus, Mercury, Mars, Jupiter, and Saturn. 5. The fixed
stars are as many suns, each of which illuminates a world. In a future
edition, 1719, Fontenelle added, 6. New thoughts which confirm those in
the preceding conversations, and the latest discoveries which have been
made in the heavens. The next work on the subject was the _Theory of
the Universe, or Conjectures concerning the Celestial Bodies and their
Inhabitants_, 1698, by Christian Huygens, the contemporary of Newton.

The doctrine is maintained by almost all the distinguished astronomers
and writers who have flourished since the true figure of the earth was
determined. Giordano Bruna of Nola, Kepler, and Tycho Brahe, believed
in it; and Cardinal Cusa and Bruno, before the discovery of binary
systems among the stars, believed also that the stars were inhabited.
Sir Isaac Newton likewise adopted the belief; and Dr. Bentley, Master
of Trinity College, Cambridge, in his eighth sermon on the Confutation
of Atheism from the origin and frame of the world, has ably maintained
the same doctrine. In our own day we may number among its supporters
the distinguished names of the Marquis de la Place, Sir William and
Sir John Herschel, Dr. Chalmers, Isaac Taylor, and M. Arago. Dr.
Chalmers maintains the doctrine in his _Astronomical Discourses_, which
one Alexander Maxwell (who did not believe in the grand truths of
astronomy) attempted to controvert, in 1820, in a chapter of a volume
entitled _Plurality of Worlds_.

Next appeared _Of a Plurality of Worlds_, attributed to the Rev. Dr.
Whewell, Master of Trinity College, Cambridge; urging the theological
not less than the scientific reasons for believing in the old tradition
of a single world, and maintaining that “the earth is really the
largest planetary body in the solar system,--its domestic hearth,
and the only world in the universe.” “I do not pretend,” says Dr.
Whewell, “to disprove the plurality of worlds; but I ask in vain for
any argument which makes the doctrine probable.” “It is too remote
from knowledge to be either proved or disproved.” Sir David Brewster
has replied to Dr. Whewell’s Essay, in _More Worlds than One, the
Creed of the Philosopher and the Hope of the Christian_, emphatically
maintaining that analogy strongly countenances the idea of all the
solar planets, if not all worlds in the universe, being peopled with
creatures not dissimilar in being and nature to the inhabitants
of the earth. This view is supported in _Scientific Certainties of
Planetary Life_, by T. C. Simon, who well treats one point of the
argument--that mere distance of the planets from the central sun
does not determine the condition as to light and heat, but that the
density of the ethereal medium enters largely into the calculation. Mr.
Simon’s general conclusion is, that “neither on account of deficient
or excessive heat, nor with regard to the density of the materials,
nor with regard to the force of gravity on the surface, is there the
slightest pretext for supposing that all the planets of our system
are not inhabited by intellectual creatures with animal bodies like
ourselves,--moral beings, who know and love their great Maker, and
who wait, like the rest of His creation, upon His providence and upon
His care.” One of the leading points of Dr. Whewell’s Essay is, that
we should not elevate the conjectures of analogy into the rank of
scientific certainties; and that “the force of all the presumptions
drawn from physical reasoning for the opinion of planets and stars
being either inhabited or uninhabited is so small, that the belief of
all thoughtful persons on this subject will be determined by moral,
metaphysical, and theological considerations.”


WORLDS TO COME--ABODES OF THE BLEST.

Sir David Brewster, in his eloquent advocacy of the doctrine of “more
worlds than one,” thus argues for their peopling:

  Man, in his future state of existence, is to consist, as at
  present, of a spiritual nature residing in a corporeal frame. He
  must live, therefore, upon a material planet, subject to all the
  laws of matter, and performing functions for which a material body
  is indispensable. We must consequently find for the race of Adam,
  if not races that may have preceded him, a material home upon which
  they may reside, or by which they may travel, by means unknown to
  us, to other localities in the universe. At the present hour, the
  inhabitants of the earth are nearly _a thousand millions_; and
  by whatever process we may compute the numbers that have existed
  before the present generation, and estimate those that are yet to
  inherit the earth, we shall obtain a population which the habitable
  parts of our globe could not possibly accommodate. If there is not
  room, then, on our earth for the millions of millions of beings who
  have lived and died upon its surface, and who may yet live and die
  during the period fixed for its occupation by man, we can scarcely
  doubt that their future abode must be on some of the primary or
  secondary planets of the solar system, whose inhabitants have
  ceased to exist like those on the earth, or upon planets in our own
  or in other systems which have been in a state of preparation, as
  our earth was, for the advent of intellectual life.


“GAUGING THE HEAVENS.”

Sir William Herschel, in 1785, conceived the happy idea of counting
the number of stars which passed at different heights and in various
directions over the field of view, of fifteen minutes in diameter,
of his twenty-feet reflecting telescope. The field of view each time
embraced only 1/833000th of the whole heavens; and it would therefore
require, according to Struve, eighty-three years to gauge the whole
sphere by a similar process.


VELOCITY OF THE SOLAR SYSTEM.

M. F. W. G. Struve gives as the splendid result of the united studies
of MM. Argelander, O. Struve, and Peters, grounded on observations
made at the three Russian observatories of Dorpat, Abo, and Pulkowa,
“that the velocity of the motion of the solar system in space is such
that the sun, with all the bodies which depend upon it, advances
annually towards the constellation Hercules[17] 1·623 times the radius
of the earth’s orbit, or 33,550,000 geographical miles. The possible
error of this last number amounts to 1,733,000 geographical miles, or
to a _seventh_ of the whole value. We may, then, wager 400,000 to 1
that the sun has a proper progressive motion, and 1 to 1 that it is
comprised between the limits of thirty-eight and twenty-nine millions
of geographical miles.”

  That is, taking 95,000,000 of English miles as the mean radius of
  the Earth’s orbit, we have 95 × 1·623 = 154·185 millions of miles;
  and consequently,

                                          English Miles.
    The velocity of the Solar System      154,185,000 in the year.
           ”         ”                        422,424 in a day.
           ”         ”                         17,601 in an hour.
           ”         ”                            293 in a minute.
           ”         ”                             57 in a second.

  The Sun and all his planets, primary and secondary, are therefore
  now in rapid motion round an invisible focus. To that now dark and
  mysterious centre, from which no ray, however feeble, shines, we
  may in another age point our telescopes, detecting perchance the
  great luminary which controls our system and bounds its path: into
  that vast orbit man, during the whole cycle of his race, may never
  be allowed to round.--_North-British Review_, No. 16.


NATURE OF THE SUN.

M. Arago has found, by experiments with the polariscope, that the light
of gaseous bodies is natural light when it issues from the burning
surface; although this circumstance does not prevent its subsequent
complete polarisation, if subjected to suitable reflections or
refractions. Hence we obtain _a most simple method of discovering
the nature of the sun_ at a distance of forty millions of leagues.
For if the light emanating from the margin of the sun, and radiating
from the solar substance _at an acute angle_, reach us without having
experienced any sensible reflections or refractions in its passage
to the earth, and if it offer traces of polarisation, the sun must
be _a solid or a liquid body_. But if, on the contrary, the light
emanating from the sun’s margin give no indications of polarisation,
the _incandescent_ portion of the sun must be _gaseous_. It is by means
of such a methodical sequence of observations that we may acquire
exact ideas regarding the physical constitution of the sun.--_Note to
Humboldt’s Cosmos_, vol. iii.


STRUCTURE OF THE LUMINOUS DISC OF THE SUN.

The extraordinary structure of the _fully luminous_ Disc of the Sun, as
seen through Sir James South’s great achromatic, in a drawing made by
Mr. Gwilt, resembles compressed curd, or white almond-soap, or a mass
of asbestos fibres, lying in a _quaquaversus_ direction, and compressed
into a solid mass. There can be no illusion in this phenomenon; it
is seen by every person with good vision, and on every part of the
sun’s luminous surface or envelope, which is thus shown to be not a
_flame_, but a soft solid or thick fluid, maintained in an incandescent
state by subjacent heat, capable of being disturbed by differences of
temperature, and broken up as we see it when the sun is covered with
spots or openings in the luminous matter.--_North-British Review_, No.
16.

  Copernicus named the sun the lantern of the world (_lucerna
  mundi_); and Theon of Smyrna called it the heart of the universe.
  The mass of the sun is, according to Encke’s calculation of
  Sabine’s pendulum formula, 359,551 times that of the earth, or
  355,499 times that of the earth and moon together; whence the
  density of the sun is only about ¼ (or more accurately 0·252) that
  of the earth. The volume of the sun is 600 times greater, and its
  mass, according to Galle, 738 times greater, than that of all the
  planets combined. It may assist the mind in conceiving a sensuous
  image of the magnitude of the sun, if we remember that if the solar
  sphere were entirely hollowed out, and the earth placed in its
  centre, there would still be room enough for the moon to describe
  its orbit, even if the radius of the latter were increased 160,000
  geographical miles. A railway-engine, moving at the rate of thirty
  miles an hour, would require 360 years to travel from the earth to
  the sun. The diameter of the sun is rather more than one hundred
  and eleven times the diameter of the earth. Therefore the volume or
  bulk of the sun must be nearly _one million four hundred thousand_
  times that of the earth. Lastly, if all the bodies composing the
  solar system were formed into one globe, it would be only about the
  five-hundredth part of the size of the sun.


GREAT SIZE OF THE SUN ON THE HORIZON EXPLAINED.

The dilated size (generally) of the Sun or Moon, when seen near the
horizon, beyond what they appear to have when high up in the sky, has
nothing to do with refraction. It is an illusion of the judgment,
arising from the terrestrial objects interposed, or placed in close
comparison with them. In that situation we view and judge of them
as we do of terrestrial objects--in detail, and with an acquired
attention to parts. Aloft we have no association to guide us, and their
insulation in the expanse of the sky leads us rather to undervalue
than to over-rate their apparent magnitudes. Actual measurement with
a proper instrument corrects our error, without, however, dispelling
our illusion. By this we learn that the sun, when just on the horizon,
subtends at our eyes almost exactly the same, and the moon a materially
_less_, angle than when seen at a greater altitude in the sky, owing to
its greater distance from us in the former situation as compared with
the latter.--_Sir John Herschel’s Outlines._


TRANSLATORY MOTION OF THE SUN.

This phenomenon is the progressive motion of the centre of gravity of
the whole solar system in universal space. Its velocity, according
to Bessel, is probably four millions of miles daily, in a _relative_
velocity to that of 61 Cygni of at least 3,336,000 miles, or more than
double the velocity of the revolution of the earth in her orbit round
the sun. This change of the entire solar system would remain unknown
to us, if the admirable exactness of our astronomical instruments of
measurement, and the advancement recently made in the art of observing,
did not cause our progress towards remote stars to be perceptible,
like an approximation to the objects of a distant shore in apparent
motion. The proper motion of the star 61 Cygni, for instance, is so
considerable, that it has amounted to a whole degree in the course of
700 years.--_Humboldt’s Cosmos_, vol. i.


THE SUN’S LIGHT COMPARED WITH TERRESTRIAL LIGHTS.

Mr. Ponton has by means of a simple monochromatic photometer
ascertained that a small surface, illuminated by mean solar light, is
444 times brighter than when it is illuminated by a moderator lamp, and
1560 times brighter than when it is illuminated by a wax-candle (short
six in the lb.)--the artificial light being in both instances placed at
two inches’ distance from the illuminated surface. And three electric
lights, each equal to 520 wax-candles, will render a small surface as
bright as when it is illuminated by mean sunshine.

It is thence inferred, that a stratum occupying the entire surface of
the sphere of which the earth’s distance from the sun is the radius,
and consisting of three layers of flame, each 1/1000th of an inch
in thickness, each possessing a brightness equal to that of such an
electric light, and all three embraced within a thickness of 1/40th of
an inch, would give an amount of illumination equal in quantity and
intensity to that of the sun at the distance of 95 millions of miles
from his centre.

And were such a stratum transferred to the surface of the sun, where it
would occupy 46,275 times less area, its thickness would be increased
to 94 feet, and it would embrace 138,825 layers of flame, equal in
brightness to the electric light; but the same effect might be produced
by a stratum about nine miles in thickness, embracing 72 millions of
layers, each having only a brightness equal to that of a wax-candle.[18]


ACTINIC POWER OF THE SUN.

Mr. J. J. Waterston, in 1857, made at Bombay some experiments on the
photographic power of the sun’s direct light, to obtain data in an
inquiry as to the possibility of measuring the diameter of the sun to
a very minute fraction of a second, by combining photography with the
principle of the electric telegraph; the first to measure the element
space, the latter the element time. The result is that about 1/20000th
of a second is sufficient exposure to the direct light of the sun to
obtain a distinct mark on a sensitive collodion plate, when developed
by the usual processes; and the duration of the sun’s full action on
any one point is about 1/9000th of a second.

M. Schatt, a young painter of Berlin, after 1500 experiments, succeeded
in establishing a scale of all the shades of black which the action of
the sun produces on photographic paper; so that by comparing the shade
obtained at any given moment on a certain paper with that indicated on
the scale, the exact force of the sun’s light may be determined.


HEATING POWER OF THE SUN.

All moving power has its origin in the rays of the sun. While
Stephenson’s iron tubular railway-bridge over the Menai Straits, 400
feet long, bends but half an inch under the heaviest pressure of a
train, it will bend up an inch and a half from its usual horizontal
line when the sun shines on it for some hours. The Bunker-Hill
monument, near Boston, U.S., is higher in the evening than in the
morning of a sunny day; the little sunbeams enter the pores of the
stone like so many wedges, lifting it up.

In winter, the Earth is nearer the Sun by about 1/30 than in summer;
but the rays strike the northern hemisphere more obliquely in winter
than the other half year.

M. Pouillet has estimated, with singular ingenuity, from a series of
observations made by himself, that the whole quantity of heat which the
Earth receives annually from the Sun is such as would be sufficient to
melt a stratum of ice covering the entire globe forty-six feet deep.

By the action of the sun’s rays upon the earth, vegetables, animals,
and man, are in their turn supported; the rays become likewise, as
it were, a store of heat, and “the sources of those great deposits
of dynamical efficiency which are laid up for human use in our coal
strata” (_Herschel_).

A remarkable instance of the power of the sun’s rays is recorded at
Stonehouse Point, Devon, in the year 1828. To lay the foundation of a
sea-wall the workmen had to descend in a diving-bell, which was fitted
with convex glasses in the upper part, by which, on several occasions
in clear weather, the sun’s rays were so concentrated as to burn the
labourers’ clothes when opposed to the focal point, and this when the
bell was twenty-five feet under the surface of the water!


CAUSE OF DARK COLOUR OF THE SKIN.

Darkness of complexion has been attributed to the sun’s power from the
age of Solomon to this day,--“Look not upon me, because I am black,
because the sun hath looked upon me:” and there cannot be a doubt
that, to a certain degree, the opinion is well founded. The invisible
rays in the solar beams, which change vegetable colour, and have been
employed with such remarkable effect in the daguerreotype, act upon
every substance on which they fall, producing mysterious and wonderful
changes in their molecular state, man not excepted.--_Mrs. Somerville._


EXTREME SOLAR HEAT.

The fluctuation in the sun’s direct heating power amounts to 1/15th,
which is too considerable a fraction of the whole intensity not
to aggravate in a serious degree the sufferings of those who are
exposed to it in thirsty deserts without shelter. The amount of these
sufferings, in the interior of Australia for instance, are of the
most frightful kind, and would seem far to exceed what have ever been
undergone by travellers in the northern deserts of Africa. Thus
Captain Sturt, in his account of his Australian exploration, says:
“The ground was almost a molten surface; and if a match accidentally
fell upon it, it immediately ignited.” Sir John Herschel has observed
the temperature of the surface soil in South Africa as high as 159°
Fahrenheit. An ordinary lucifer-match does not ignite when simply
pressed upon a smooth surface at 212°; but _in the act of withdrawing
it_ it takes fire, and the slightest friction upon such a surface of
course ignites it.


HOW DR. WOLLASTON COMPARED THE LIGHT OF THE SUN AND THE FIXED STARS.

In order to compare the Light of the Sun with that of a Star, Dr.
Wollaston took as an intermediate object of comparison the light of a
candle reflected from a bulb about a quarter of an inch in diameter,
filled with quicksilver; and seen by one eye through a lens of two
inches focus, at the same time that the star on the sun’s image,
_placed at a proper distance_, was viewed by the other eye through a
telescope. The mean of various trials seemed to show that the light
of Sirius is equal to that of the sun seen in a glass bulb 1/10th of
an inch in diameter, at the distance of 210 feet; or that they are in
the proportion of one to ten thousand millions: but as nearly one half
of this light is lost by reflection, the real proportion between the
light from Sirius and the sun is not greater than that of one to twenty
thousand millions.


“THE SUN DARKENED.”

Humboldt selects the following example from historical records as to
the occurrence of a sudden decrease in the light of the Sun:

  A.D. 33, the year of the Crucifixion. “Now from the sixth hour
  there was darkness over all the land till the ninth hour” (_St.
  Matthew_ xxvii. 45). According to _St. Luke_ (xxiii. 45), “the
  sun was darkened.” In order to explain and corroborate these
  narrations, Eusebius brings forward an eclipse of the sun in the
  202d Olympiad, which had been noticed by the chronicler Phlegon
  of Tralles (_Ideler_, _Handbuch der Mathem. Chronologie_, Bd. ii.
  p. 417). Wurn, however, has shown that the eclipse which occurred
  during this Olympiad, and was visible over the whole of Asia
  Minor, must have happened as early as the 24th of November 29 A.D.
  The day of the Crucifixion corresponded with the Jewish Passover
  (_Ideler_, Bd. i. pp. 515-520), on the 14th of the month Nisan, and
  the Passover was always celebrated at the time of the _full moon_.
  The sun cannot therefore have been darkened for three hours by the
  moon. The Jesuit Scheiner thinks the decrease in the light might be
  ascribed to the occurrence of large sun-spots.


THE SUN AND TERRESTRIAL MAGNETISM.

The important influence exerted by the Sun’s body, as a mass, upon
Terrestrial Magnetism, is confirmed by Sabine in the ingenious
observation, that the period at which the intensity of the magnetic
force is greatest, and the direction of the needle most near to the
vertical line, falls in both hemispheres between the months of October
and February; that is to say, precisely at the time when the earth is
nearest to the sun, and moves in its orbit with the greatest velocity.


IS THE HEAT OF THE SUN DECREASING?

The Heat of the Sun is dissipated and lost by radiation, and must
be progressively diminished unless its thermal energy be supplied.
According to the measurements of M. Pouillet, the quantity of heat
given out by the sun in a year is equal to that which would be produced
by the combustion of a stratum of coal seventeen miles in thickness;
and if the sun’s capacity for heat be assumed equal to that of water,
and the heat be supposed drawn uniformly from its entire mass, its
temperature would thereby undergo a diminution of 20·4° Fahr. annually.
On the other hand, there is a vast store of force in our system capable
of conversion into heat. If, as is indicated by the small density of
the sun, and by other circumstances, that body has not yet reached the
condition of incompressibility, we have in the future approximation of
its parts a fund of heat, probably quite large enough to supply the
wants of the human family to the end of its sojourn here. It has been
calculated that an amount of condensation which would diminish the
diameter of the sun by only the ten-thousandth part, would suffice to
restore the heat emitted in 2000 years.


UNIVERSAL SUN-DIAL.

Mr. Sharp, of Dublin, exhibited to the British Association in 1849 a
Dial, consisting of a cylinder set to the day of the month, and then
elevated to the latitude. A thin plane of metal, in the direction of
its axis, is then turned by a milled head below it till the shadow is
a minimum, when a dial on the top shows the hours by one hand, and the
minutes by another, to the precision of about three minutes.


LENGTH OF DAYS AT THE POLES.

During the summer, in the northern hemisphere, places near the North
Pole are in _continual sunlight_--the sun never sets to them; while
during that time places near the South Pole never see the sun. When it
is summer in the southern hemisphere, and the sun shines on the South
Pole without setting, the North Pole is entirely deprived of his light.
Indeed, at the Poles there is but _one day and one night_; for the sun
shines for six months together on one Pole, and the other six months on
the other Pole.


HOW THE DISTANCE OF THE SUN IS ASCERTAINED BY THE YARD-MEASURE.

Professor Airy, in his _Six Lectures on Astronomy_, gives a masterly
analysis of a problem of considerable intricacy, viz. the determination
of the parallax of the sun, and consequently of his distance, by
observations of the transit of Venus, the connecting link between
measures upon the earth’s surface and the dimensions of our system.
The further step of investigating the parallax, and consequently the
distance of the fixed stars (where that is practicable), is also
elucidated; and the author, with evident satisfaction, thus sums up the
several steps:

  By means of a yard-measure, a base-line in a survey was measured;
  from this, by the triangulations and computations of a survey,
  an arc of meridian on the earth was measured; from this, with
  proper observations with the zenith sector, the surveys being also
  repeated on different parts of the earth, the earth’s form and
  dimensions were ascertained; from these, and a previous independent
  knowledge of the proportions of the distances of the earth and
  other planets from the sun, with observations of the transit of
  Venus, the sun’s distance is determined; and from this, with
  observations leading to the parallax of the stars, the distance
  of the stars is determined. And _every step in the process can be
  distinctly referred to its basis, that is, the yard-measure_.


HOW THE TIDES ARE PRODUCED BY THE SUN AND MOON.

Each of these bodies excites, by its attraction upon the waters of the
sea, two gigantic waves, which flow in the same direction round the
world as the attracting bodies themselves apparently do. The two waves
of the moon, on account of her greater nearness, are about 3½ times as
large as those excited by the sun. One of these waves has its crest on
the quarter of the earth’s surface which is turned towards the moon;
the other is at the opposite side. Both these quarters possess the flow
of the tide, while the regions which lie between have the ebb. Although
in the open sea the height of the tide amounts to only about three
feet, and only in certain narrow channels, where the moving water is
squeezed together, rises to thirty feet, the might of the phenomenon
is nevertheless manifest from the calculation of Bessel, according to
which a quarter of the earth covered by the sea possesses during the
flow of the tide about 25,000 cubic miles of water more than during the
ebb; and that, therefore, such a mass of water must in 6¼ hours flow
from one quarter of the earth to the other.--_Professor Helmholtz._


SPOTS ON THE SUN.

Sir John Herschel describes these phenomena, when watched from day to
day, or even from hour to hour, as appearing to enlarge or contract,
to change their forms, and at length disappear altogether, or to break
out anew in parts of the surface where none were before. Occasionally
they break up or divide into two or more. The scale on which their
movements takes place is immense. A single second of angular measure,
as seen from the earth, corresponds on the sun’s disc to 461 miles; and
a circle of this diameter (containing therefore nearly 167,000 square
miles) is the least space which can be distinctly discerned on the sun
as a _visible area_. Spots have been observed, however, whose linear
diameter has been upwards of 45,000 miles; and even, if some records
are to be trusted, of very much greater extent. That such a spot should
close up in six weeks time (for they seldom last much longer), its
borders must approach at the rate of more than 1000 miles a-day.

The same astronomer saw at the Cape of Good Hope, on the 29th March
1837, a solar spot occupying an area of near _five square minutes_,
equal to 3,780,000,000 square miles. “The black centre of the spot of
May 25th, 1837 (not the tenth part of the preceding one), would have
allowed the globe of our earth to drop through it, leaving a thousand
miles clear of contact on all sides of that tremendous gulf.” For such
an amount of disturbance on the sun’s atmosphere, what reason can be
assigned?

The Rev. Mr. Dawes has invented a peculiar contrivance, by means of
which he has been enabled to scrutinise, under high magnifying power,
minute portions of the solar disc. He places a metallic screen, pierced
with a very small hole, in the focus of the telescope, where the image
of the sun is formed. A small portion only of the image is thus allowed
to pass through, so that it may be examined by the eye-piece without
inconveniencing the observer by heat or glare. By this arrangement,
Mr. Dawes has observed peculiarities in the constitution of the sun’s
surface which are discernible in no other way.

Before these observations, the dark spots seen on the sun’s surface
were supposed to be portions of the solid body of the sun, laid bare to
our view by those immense fluctuations in the luminous regions of its
atmosphere to which it appears to be subject. It now appears that these
dark portions are only an additional and inferior stratum of a very
feebly luminous or illuminated portion of the sun’s atmosphere. This
again in its turn Mr. Dawes has frequently seen pierced with a smaller
and usually much more rounded aperture, which would seem at last to
afford a view of the real solar surface of most intense blackness.

M. Schwabe, of Dessau, has discovered that the abundance or paucity
of spots displayed by the sun’s surface is subject to a law of
periodicity. This has been confirmed by M. Wolf, of Berne, who shows
that the period of these changes, from minimum to minimum, is 11 years
and 11-hundredths of a year, being exactly at the rate of nine periods
per century, the last year of each century being a year of minimum. It
is strongly corroborative of the correctness both of M. Wolf’s period
and also of the periodicity itself, that of all the instances of the
appearance of spots on the sun recorded in history, even before the
invention of the telescope, or of remarkable deficiencies in the sun’s
light, of which there are great numbers, only two are found to deviate
as much as two years from M. Wolf’s epochs. Sir William Herschel
observed that the presence or absence of spots had an influence on the
temperature of the seasons; his observations have been fully confirmed
by M. Wolf. And, from an examination of the chronicles of Zurich from
A.D. 1000 to A.D. 1800, he has come to the conclusion “that years rich
in solar spots are in general drier and more fruitful than those of an
opposite character; while the latter are wetter and more stormy than
the former.”

The most extraordinary fact, however, in connection with the spots on
the sun’s surface, is the singular coincidence of their periods with
those great disturbances in the magnetic system of the earth to which
the epithet of “magnetic storms” has been affixed.

  These disturbances, during which the magnetic needle is greatly
  and universally agitated (not in a particular limited locality,
  but at one and the same instant of time over whole continents, or
  even over the whole earth), are found, so far as observation has
  hitherto extended, to maintain a parallel, both in respect of their
  frequency of occurrence and intensity in successive years, with the
  abundance and magnitude of the spots in the same years, too close
  to be regarded as fortuitous. The coincidence of the epochs of
  maxima and minima in the two series of phenomena amounts, indeed,
  to identity; a fact evidently of most important significance, but
  which neither astronomical nor magnetic science is yet sufficiently
  advanced to interpret.--_Herschel’s Outlines._

The signification and connection of the above varying phenomena
(Humboldt maintains) can never be manifested in their entire importance
until an uninterrupted series of representations of the sun’s spots
can be obtained by the aid of mechanical clock-work and photographic
apparatus, as the result of prolonged observations during the many
months of serene weather enjoyed in a tropical climate.

  M. Schwabe has thus distinguished himself as an indefatigable
  observer of the sun’s spots, for his researches received the Royal
  Astronomical Society’s Medal in 1857. “For thirty years,” said
  the President at the presentation, “never has the sun exhibited
  his disc above the horizon of Dessau without being confronted
  by Schwabe’s imperturbable telescope; and that appears to have
  happened on an average about 300 days a-year. So, supposing that
  he had observed but once a-day, he has made 9000 observations,
  in the course of which he discovered about 4700 groups. This is,
  I believe, an instance of devoted persistence unsurpassed in
  the annals of astronomy. The energy of one man has revealed a
  phenomenon that had eluded the suspicion of astronomers for 200
  years.”


HAS THE MOON AN ATMOSPHERE?

The Moon possesses neither Sea nor Atmosphere of appreciable
extent. Still, as a negative, in such case, is relative only to
the capabilities of the instruments employed, the search for the
indications of a lunar atmosphere has been renewed with fresh
augmentation of telescopic power. Of such indications, the most
delicate, perhaps, are those afforded by the occultation of a planet
by the moon. The occultation of Jupiter, which took place on January
2, 1857, was observed with this reference, and is said to have
exhibited no _hesitation_, or change of form or brightness, such as
would be produced by the refraction or absorption of an atmosphere. As
respects the sea, if water existed on the moon’s surface, the sun’s
light reflected from it should be completely polarised at a certain
elongation of the moon from the sun; and no traces of such light have
been observed.

MM. Baer and Maedler conclude that the moon is not entirely without
an atmosphere, but, owing to the smallness of her mass, she is
incapacitated from holding an extensive covering of gas; and they add,
“it is possible that this weak envelope may sometimes, through local
causes, in some measure dim or condense itself.” But if any atmosphere
exists on our satellite, it must be, as Laplace says, more attenuated
than what is termed a vacuum in an air-pump.

Mr. Hopkins thinks that if there be any lunar atmosphere, it must
be very rare in comparison with the terrestrial atmosphere, and
inappreciable to the kind of observation by which it has been tested;
yet the absence of any refraction of the light of the stars during
occultation is a very refined test. Mr. Nasmyth observes that “the
sudden disappearance of the stars behind the moon, without any change
or diminution of her brilliancy, is one of the most beautiful phenomena
that can be witnessed.”

Sir John Herschel observes: The fact of the moon turning always the
same face towards the earth is, in all probability, the result of an
elongation of its figure in the direction of a line joining the centres
of both the bodies, acting conjointly with a non-coincidence of its
centre of gravity with its centre of symmetry.

If to this we add the supposition that the substance of the moon is
not homogeneous, and that some considerable preponderance of weight
is placed excentrically in it, it will be easily apprehended that the
portion of its surface nearer to that heavier portion of its solid
content, under all the circumstances of the moon’s rotation, will
permanently occupy the situation most remote from the earth.

  In what regards its assumption of a definite level, air obeys
  precisely the same hydrostatical laws as water. The lunar
  atmosphere would rest upon the lunar ocean, and form in its basin a
  lake of air, whose upper portions at an altitude such as we are now
  contemplating would be of excessive tenuity, especially should the
  provision of air be less abundant in proportion than our own. It by
  no means follows, then, from the absence of visible indications of
  water or air on this side of the moon, that the other is equally
  destitute of them, and equally unfitted for maintaining animal or
  vegetable life. Some slight approach to such a state of things
  actually obtains on the earth itself. Nearly all the land is
  collected in one of its hemispheres, and much the larger portion
  of the sea in the opposite. There is evidently an excess of heavy
  material vertically beneath the middle of the Pacific; while not
  very remote from the point of the globe diametrically opposite
  rises the great table-land of India and the Himalaya chain, on the
  summits of which the air has not more than a third of the density
  it has on the sea-level, and from which animated existence is for
  ever excluded.--_Herschel’s Outlines_, 5th edit.


LIGHT OF THE MOON.

The actual illumination of the lunar surface is not much superior to
that of weathered sandstone-rock in full sunshine. Sir John Herschel
has frequently compared the moon setting behind the gray perpendicular
façade of the Table Mountain at the Cape of Good Hope, illuminated
by the sun just risen from the opposite quarter of the horizon, when
it has been scarcely distinguishable in brightness from the rock in
contact with it. The sun and moon being nearly at equal altitudes, and
the atmosphere perfectly free from cloud or vapour, its effect is alike
on both luminaries.


HEAT OF MOONLIGHT.

M. Zantedeschi has proved, by a long series of experiments in the
Botanic Gardens at Venice, Florence, and Padua, that, contrary to the
general opinion, the diffused rays of moonlight have an influence
upon the organs of plants, as the Sensitive Plant and the _Desmodium
gyrans_. The influence was feeble compared with that of the sun; but
the action is left beyond further question.

Melloni has proved that the rays of the Moon give out a slight degree
of Heat (see _Things not generally Known_, p. 7); and Professor Piazzi
Smyth, from a point of the Peak of Teneriffe 8840 feet above the
sea-level, has found distinctly perceptible the heat radiated from the
moon, which has been so often sought for in vain in a lower region.


SCENERY OF THE MOON.

By means of the telescope, mountain-peaks are distinguished in the
ash-gray light of the larger spots and isolated brightly-shining points
of the moon, even when the disc is already more than half illuminated.
Lambert and Schroter have shown that the extremely variable intensity
of the ash-gray light of the moon depends upon the greater or less
degree of reflection of the sunlight which falls upon the earth,
according as it is reflected from continuous continental masses, full
of sandy deserts, grassy steppes, tropical forests, and barren rocky
ground, or from large ocean surfaces. Lambert made the remarkable
observation (14th of February 1774) of a change of the ash-coloured
moonlight into an olive-green colour bordering upon yellow. “The moon,
which then stood vertically over the Atlantic Ocean, received upon its
right side the green terrestrial light which is reflected towards her
when the sky is clear by the forest districts of South America.”

Plutarch says distinctly, in his remarkable work _On the Face in the
Moon_, that we may suppose the _spots_ to be partly deep chasms and
valleys, partly mountain-peaks, which cast long shadows, like Mount
Athos, whose shadow reaches Lemnos. The spots cover about two-fifths
of the whole disc. In a clear atmosphere, and under favourable
circumstances in the position of the moon, some of the spots are
visible to the naked eye; as the edge of the Apennines, the dark
elevated plain Grimaldus, the enclosed _Mare Crisium_, and Tycho,
crowded round with numerous mountain ridges and craters.

Professor Alexander remarks, that a map of the eastern hemisphere,
taken with the Bay of Bengal in the centre, would bear a striking
resemblance to the face of the moon presented to us. The dark portions
of the moon he considers to be continental elevations, as shown by
measuring the average height of mountains above the dark and the light
portions of the moon.

The surface of the moon can be as distinctly seen by a good telescope
magnifying 1000 times, as it would be if not more than 250 miles
distant.


LIFE IN THE MOON.

A circle of one second in diameter, as seen from the earth, on the
surface of the moon contains about a square mile. Telescopes,
therefore, must be greatly improved before we could expect to see signs
of inhabitants, as manifested by edifices or changes on the surface
of the soil. It should, however, be observed, that owing to the small
density of the materials of the moon, and the comparatively feeble
gravitation of bodies on her surface, muscular force would there go six
times as far in overcoming the weight of materials as on the earth.
Owing to the want of air, however, it seems impossible that any form
of life analogous to those on earth can subsist there. No appearance
indicating vegetation, or the slightest variation of surface which can
in our opinion fairly be ascribed to change of season, can any where be
discerned.--_Sir John Herschel’s Outlines._


THE MOON SEEN THROUGH LORD ROSSE’S TELESCOPE.

In 1846, the Rev. Dr. Scoresby had the gratification of observing
the Moon through the stupendous telescope constructed by Lord Rosse
at Parsonstown. It appeared like a globe of molten silver, and every
object to the extent of 100 yards was quite visible. Edifices,
therefore, of the size of York Minster, or even of the ruins of Whitby
Abbey, might be easily perceived, if they had existed. But there was
no appearance of any thing of that nature; neither was there any
indication of the existence of water, or of an atmosphere. There
were a great number of extinct volcanoes, several miles in breadth;
through one of them there was a line of continuance about 150 miles in
length, which ran in a straight direction, like a railway. The general
appearance, however, was like one vast ruin of nature; and many of the
pieces of rock driven out of the volcanoes appeared to lie at various
distances.


MOUNTAINS IN THE MOON.

By the aid of telescopes, we discern irregularities in the surface of
the moon which can be no other than mountains and valleys,--for this
plain reason, that we see the shadows cast by the former in the exact
proportion as to length which they ought to have when we take into
account the inclinations of the sun’s rays to that part of the moon’s
surface on which they stand. From micrometrical measurements of the
lengths of the shadows of the more conspicuous mountains, Messrs. Baer
and Maedler have given a list of heights for no less than 1095 lunar
mountains, among which occur all degrees of elevation up to 22,823
British feet, or about 1400 feet higher than Chimborazo in the Andes.

If Chimborazo were as high in proportion to the earth’s diameter as
a mountain in the moon known by the name of Newton is to the moon’s
diameter, its peak would be more than sixteen miles high.

Arago calls to mind, that with a 6000-fold magnifying power, which
nevertheless could not be applied to the moon with proportionate
results, the mountains upon the moon would appear to us just as Mont
Blanc does to the naked eye when seen from the Lake of Geneva.

We sometimes observe more than half the surface of the moon, the
eastern and northern edges being more visible at one time, and the
western or southern at another. By means of this libration we are
enabled to see the annular mountain Malapert (which occasionally
conceals the moon’s south pole), the arctic landscape round the crater
of Gioja, and the large gray plane near Endymion, which conceals in
superficial extent the _mare vaporum_.

Three-sevenths of the moon are entirely concealed from our observation;
and must always remain so, unless some new and unexpected disturbing
causes come into play.--_Humboldt._

  The first object to which Galileo directed his telescope was the
  mountainous parts of the moon, when he showed how their summits
  might be measured: he found in the moon some circular districts
  surrounded on all sides by mountains similar to the form of
  Bohemia. The measurements of the mountains were made by the method
  of the tangents of the solar ray. Galileo, as Helvetius did still
  later, measured the distance of the summit of the mountains from
  the boundary of the illuminated portion at the moment when the
  mountain summit was first struck by the solar ray. Humboldt found
  no observations of the lengths of the shadows of the mountains:
  the summits were “much higher than the mountains on our earth.”
  The comparison is remarkable, since, according to Riccioli,
  very exaggerated ideas of the height of our mountains were then
  entertained. Galileo like all other observers up to the close of
  the eighteenth century, believed in the existence of many seas and
  of a lunar atmosphere.


THE MOON AND THE WEATHER.

The only influence of the Moon on the Weather of which we have any
decisive evidence is the tendency to disappearance of clouds under the
full moon, which Sir John Herschel refers to its heat being much more
readily absorbed in traversing transparent media than direct solar
heat, and being extinguished in the upper regions of our atmosphere,
never reaches the surface of the atmosphere at all.


THE MOON’S ATTRACTION.

Mr. G. P. Bond of Cambridge, by some investigations to ascertain
whether the Attraction of the Moon has any effect upon the motion of
a pendulum, and consequently upon the rate of a clock, has found the
last to be changed to the amount of 9/1000 of a second daily. At
the equator the moon’s attraction changes the weight of a body only
1/7000000 of the whole; yet this force is sufficient to produce the
vast phenomena of the tides!

It is no slight evidence of the importance of analysis, that Laplace’s
perfect theory of tides has enabled us in our astronomical ephemerides
to predict the height of spring-tides at the periods of new and full
moon, and thus put the inhabitants of the sea on their guard against
the increased danger attending the lunar revolutions.


MEASURING THE EARTH BY THE MOON.

As the form of the Earth exerts a powerful influence on the motion
of other cosmical bodies, and especially on that of its neighbouring
satellite, a more perfect knowledge of the motion of the latter will
enable us reciprocally to draw an inference regarding the figure of
the earth. Thus, as Laplace ably remarks: “an astronomer, without
leaving his observatory, may, by a comparison of lunar theory with true
observations, not only be enabled to determine the form and size of
the earth, but also its distance from the sun and moon; results that
otherwise could only be arrived at by long and arduous expeditions
to the most remote parts of both hemispheres.” The compression which
may be inferred from lunar inequalities affords an advantage not
yielded by individual measurements of degrees or experiments with the
pendulum, since it gives a mean amount which is referable to the whole
planet.--_Humboldt’s Cosmos_, vol. i.

The distance of the moon from the earth is about 240,000 miles; and
if a railway-carriage were to travel at the rate of 1000 miles a-day,
it would be eight months in reaching the moon. But that is nothing
compared with the length of time it would occupy a locomotive to reach
the sun from the earth: if travelling at the rate of 1000 miles a-day,
it would require 260 years to reach it.


CAUSE OF ECLIPSES.

As the Moon is at a very moderate distance from us (astronomically
speaking), and is in fact our nearest neighbour, while the sun and
stars are in comparison immensely beyond it, it must of necessity
happen that at one time or other it must _pass over_, and _occult_ or
_eclipse_, every star or planet within its zone, and, as seen from
the _surface_ of the earth, even somewhat beyond it. Nor is the sun
itself exempt from being thus hidden whenever any part of the moon’s
disc, in this her tortuous course, comes to _overlap_ any part of the
space occupied in the heavens by that luminary. On these occasions
is exhibited the most striking and impressive of all the occasional
phenomena of astronomy, an _Eclipse of the Sun_, in which a greater or
less portion, or even in some conjunctures the whole of its disc, is
obscured, and, as it were, obliterated, by the superposition of that
of the moon, which appears upon it as a circularly-terminated black
spot, producing a temporary diminution of daylight, or even nocturnal
darkness, so that the stars appear as if at midnight.--_Sir John
Herschel’s Outlines._


VAST NUMBERS IN THE UNIVERSE.

The number of telescopic stars in the Milky Way uninterrupted by
any nebulæ is estimated at 18,000,000. To compare this number with
something analogous, Humboldt calls attention to the fact, that there
are not in the whole heavens more than about 8000 stars, between
the first and the sixth magnitudes, visible to the naked eye. The
barren astonishment excited by numbers and dimensions in space when
not considered with reference to applications engaging the mental
and perceptive powers of man, is awakened in both extremes of the
universe--in the celestial bodies as in the minutest animalcules. A
cubic inch of the polishing slate of Bilin contains, according to
Ehrenberg, 40,000 millions of the siliceous shells of Galionellæ.


FOR WHAT PURPOSE WERE THE STARS CREATED?

Surely not (says Sir John Herschel) to illuminate _our_ nights, which
an additional moon of the thousandth part of the size of our own
would do much better; nor to sparkle as a pageant void of meaning and
reality, and bewilder us among vain conjectures. Useful, it is true,
they are to man as points of exact and permanent reference; but he must
have studied astronomy to little purpose, who can suppose man to be the
only object of his Creator’s care, or who does not see in the vast and
wonderful apparatus around us provision for other races of animated
beings. The planets derive their light from the sun; but that cannot be
the case with the stars. These doubtless, then, are themselves suns;
and may perhaps, each in its sphere, be the presiding centre round
which other planets, or bodies of which we can form no conception from
any analogy offered by our own system, are circulating.[19]


NUMBER OF STARS.

Various estimates have been hazarded on the Number of Stars throughout
the whole heavens visible to us by the aid of our colossal telescopes.
Struve assumes for Herschel’s 20-feet reflector, that a magnifying
power of 180 would give 5,800,000 for the number of stars lying within
the zones extending 30° on either side of the equator, and 20,374,000
for the whole heavens. Sir William Herschel conjectured that 18,000,000
of stars in the Milky Way might be seen by his still more powerful
40-feet reflecting telescope.--_Humboldt’s Cosmos_, vol. iii.

The assumption that the extent of the starry firmament is literally
infinite has been made by Dr. Olbers the basis of a conclusion that the
celestial spaces are in some slight degree deficient in _transparency_;
so that all beyond a certain distance is and must remain for ever
unseen, the geometrical progression of the extinction of light far
outrunning the effect of any conceivable increase in the power of
our telescopes. Were it not so, it is argued that every part of the
celestial concave ought to shine with the brightness of the solar disc,
since no visual ray could be so directed as not, in some point or other
of its infinite length, to encounter such a disc.--_Edinburgh Review_,
Jan. 1848.


STARS THAT HAVE DISAPPEARED.

Notwithstanding the great accuracy of the catalogued positions of
telescopic fixed stars and of modern star-maps, the certainty of
conviction that a star in the heavens has actually disappeared since
a certain epoch can only be arrived at with great caution. Errors of
actual observation, of reduction, and of the press, often disfigure the
very best catalogues. The disappearance of a heavenly body from the
place in which it had been before distinctly seen, may be the result
of its own motion as much as of any such diminution of its photometric
process as would render the waves of light too weak to excite our
organs of sight. What we no longer see, is not necessarily annihilated.
The idea of destruction or combustion, as applied to disappearing
stars, belongs to the age of Tycho Brahe. Even Pliny makes it a
question. The apparent eternal cosmical alternation of existence and
destruction is not annihilation; it is merely the transition of matter
into new forms, into combinations which are subject to new processes.
Dark cosmical bodies may by a renewed process of light again become
luminous.--_Humboldt’s Cosmos_, vol. iii.


THE POLE-STAR FOUR THOUSAND YEARS AGO.

Sir John Herschel, in his _Outlines of Astronomy_, thus shows the
changes in the celestial pole in 4000 years:

  At the date of the erection of the Pyramid of Gizeh, which precedes
  the present epoch by nearly 4000 years, the longitudes of all the
  stars were less by 55° 45′ than at present. Calculating from
  this datum the place of the pole of the heavens among the stars,
  it will be found to fall near α Draconis; its distance from that
  star being 3° 44′ 25″. This being the most conspicuous star in
  the immediate neighbourhood, was therefore the Pole Star of that
  epoch. The latitude of Gizeh being just 30° north, and consequently
  the altitude of the North Pole there also 30°, it follows that
  the star in question must have had at its lowest culmination at
  Gizeh an altitude of 25° 15′ 35″. Now it is a remarkable fact,
  that of the nine pyramids still existing at Gizeh, six (including
  all the largest) have the narrow passages by which alone they can
  be entered (all which open out on the northern faces of their
  respective pyramids) inclined to the horizon downwards at angles
  the mean of which is 26° 47′. At the bottom of every one of these
  passages, therefore, the Pole Star must have been visible at its
  lower culmination; a circumstance which can hardly be supposed
  to have been unintentional, and was doubtless connected (perhaps
  superstitiously) with the astronomical observations of that star,
  of whose proximity to the pole at the epoch of the erection of
  these wonderful structures we are thus furnished with a monumental
  record of the most imperishable nature.


THE PLEIADES.

The Pleiades prove that, several thousand years ago even as now,
stars of the seventh magnitude were invisible to the naked eye of
average visual power. The group consists of seven stars, of which six
only, of the third, fourth, and fifth magnitudes, could be readily
distinguished. Of these Ovid says (_Fast._ iv. 170):

    “Quæ septem dici, sex tamen esse solent.”

Aratus states there were only six stars visible in the Pleiades.

One of the daughters of Atlas, Merope, the only one who was wedded to
a mortal, was said to have veiled herself for very shame and to have
disappeared. This is probably the star of the seventh magnitude, which
we call Celæne; for Hipparchus, in his commentary on Aratus, observes
that on clear moonless nights _seven stars_ may actually be seen.

The Pleiades were doubtless known to the rudest nations from the
earliest times; they are also called the _mariner’s stars_. The name is
from πλεῖν (_plein_), ‘to sail.’ The navigation of the Mediterranean
lasted from May to the beginning of November, from the early rising
to the early setting of the Pleiades. In how many beautiful effusions
of poetry and sentiment has “the Lost Pleiad” been deplored!--and, to
descend to more familiar illustration of this group, the “Seven Stars,”
the sailors’ favourites, and a frequent river-side public-house sign,
may be traced to the Pleiades.


CHANGE OF COLOUR IN THE STARS.

The scintillation or twinkling of the stars is accompanied by
variations of colour, which have been remarked from a very early age.
M. Arago states, upon the authority of M. Babinet, that the name of
Barakesch, given by the Arabians to Sirius, signifies _the star of
a thousand colours_; and Tycho Brahe, Kepler, and others, attest to
similar change of colour in twinkling. Even soon after the invention
of the telescope, Simon Marius remarked that by removing the eye-piece
of the telescope the images of the stars exhibited rapid fluctuations
of brightness and colour. In 1814 Nicholson applied to the telescope a
smart vibration, which caused the image of the star to be transformed
into a curved line of light returning into itself, and diversified by
several colours; each colour occupied about a third of the whole length
of the curve, and by applying ten vibrations in a second, the light of
Sirius in that time passed through thirty changes of colour. Hence the
stars in general shine only by a portion of their light, the effect of
twinkling being to diminish their brightness. This phenomenon M. Arago
explains by the principle of the interference of light.

Ptolemy is said to have noted Sirius as a _red_ star, though it is now
white. Sirius twinkles with red and blue light, and Ptolemy’s eyes,
like those of several other persons, may have been more sensitive to
the _red_ than to the _blue_ rays.--_Sir David Brewster’s More Worlds
than One_, p. 235.

Some of the double stars are of very different and dissimilar colours;
and to the revolving planetary bodies which apparently circulate around
them, a day lightened by a red light is succeeded by, not a night, but
a day equally brilliant, though illuminated only by a green light.


DISTANCE OF THE NEAREST FIXED STAR FROM THE EARTH.

Sir John Herschel wrote in 1833: “What is the distance of the nearest
fixed star? What is the scale on which our visible firmament is
constructed? And what proportion do its dimensions bear to those of our
own immediate system? To this, however, astronomy has hitherto proved
unable to supply an answer. All we know on this subject is negative.”
To these questions, however, an answer can now be given. Slight
changes of position of some of the stars, called parallax, have been
distinctly observed and measured; and among these stars No. 61 Cygni of
Flamstead’s catalogue has a parallax of 5″, and that of α Centauri has
a proper motion of 4″ per annum.

The same astronomer states that each second of parallax indicates a
distance of 20 billions of miles, or 3¼ years’ journey of light. Now
the light sent to us by the sun, as compared with that sent by Sirius
and α Centauri, is about 22 thousand millions to 1. “Hence, from the
parallax assigned above to that star, it is easy to conclude that
its intrinsic splendour, as compared with that of our sun at equal
distances, is 2·3247, that of the sun being unity. The light of Sirius
is four times that of α Centauri, and its parallax only 0·15″. This,
in effect, ascribes to it an intrinsic splendour equal to 96·63 times
that of α Centauri, and therefore 224·7 times that of our sun.”

This is justly regarded as one of the most brilliant triumphs of
astronomical science, for the delicacy of the investigation is
almost inconceivable; yet the reasoning is as unimpeachable as the
demonstration of a theorem of Euclid.


LIGHT OF A STAR SIXTEENFOLD THAT OF THE SUN.

The bright star in the constellation of the Lyre, termed Vega, is the
brightest in the northern hemisphere; and the combined researches of
Struve, father and son, have found that the distance of this star from
the earth is no less than 130 billions of miles! Light travelling
at the rate of 192 thousand miles in a second consequently occupies
twenty-one years in passing from this star to the earth. Now it has
been found, by comparing the light of Vega with the light of the
sun, that if the latter were removed to the distance of 130 billions
of miles, his apparent brightness would not amount to more than the
sixteenth part of the apparent brightness of Vega. We are therefore
warranted in concluding that the light of Vega is equal to that of
sixteen suns.


DIVERSITIES OF THE PLANETS.

In illustration of the great diversity of the physical peculiarities
and probable condition of the planets, Sir John Herschel describes
the intensity of solar radiation as nearly seven times greater on
Mercury than on the earth, and on Uranus 330 times less; the proportion
between the two extremes being that of upwards of 2000 to 1. Let any
one figure to himself, (adds Sir John,) the condition of our globe
were the sun to be septupled, to say nothing of the greater ratio; or
were it diminished to a seventh, or to a 300th of its actual power!
Again, the intensity of gravity, or its efficacy in counteracting
muscular power and repressing animal activity, on Jupiter is nearly
two-and-a-half times that on the earth; on Mars not more than one-half;
on the moon one-sixth; and on the smaller planets probably not more
than one-twentieth; giving a scale of which the extremes are in the
proportion of sixty to one. Lastly, the density of Saturn hardly
exceeds one-eighth of the mean density of the earth, so that it must
consist of materials not much heavier than cork.

  Jupiter is eleven times, Saturn ten times, Uranus five times, and
  Neptune nearly six times, the diameter of our earth.

  These four bodies revolve in space at such distances from the sun,
  that if it were possible to start thence for each in succession,
  and to travel at the railway speed of 33 miles per hour, the
  traveller would reach

    Jupiter in  1712 years
    Saturn      3113   ”
    Uranus      6226   ”
    Neptune     9685   ”

  If, therefore, a person had commenced his journey at the period of
  the Christian era, he would now have to travel nearly 1300 years
  before he would arrive at the planet Saturn; more than 4300 years
  before he would reach Uranus; and no less than 7800 years before he
  could reach the orbit of Neptune.

  Yet the light which comes to us from these remote confines of the
  solar system first issued from the sun, and is then reflected
  from the surface of the planet. When the telescope is turned
  towards Neptune, the observer’s eye sees the object by means of
  light that issued from the sun eight hours before, and which
  since then has passed nearly twice through that vast space which
  railway speed would require almost a century of centuries to
  accomplish.--_Bouvier’s Familiar Astronomy._


GRAND RESULTS OF THE DISCOVERY OF JUPITER’S SATELLITES.

This discovery, one of the first fruits of the invention of the
telescope, and of Galileo’s early and happy idea of directing its
newly-found powers to the examination of the heavens, forms one of
the most memorable epochs in the history of astronomy. The first
astronomical solution of the great problem of _the longitude_,
practically the most important for the interests of mankind which has
ever been brought under the dominion of strict scientific principles,
dates immediately from this discovery. The final and conclusive
establishment of the Copernican system of astronomy may also be
considered as referable to the discovery and study of this exquisite
miniature system, in which the laws of the planetary motions, as
ascertained by Kepler, and specially that which connects their periods
and distances, were specially traced, and found to be satisfactorily
maintained. And (as if to accumulate historical interest on this point)
it is to the observation of the eclipses of Jupiter’s satellites
that we owe the grand discovery of the aberration of light, and the
consequent determination of the enormous velocity of that wonderful
element--192,000 miles per second. Mr. Dawes, in 1849, first noticed
the existence of round, well-defined, bright spots on the belts of
Jupiter. They vary in situation and number, as many as ten having been
seen on one occasion. As the belts of Jupiter have been ascribed to the
existence of currents analogous to our trade-winds, causing the body of
Jupiter to be visible through his cloudy atmosphere, Sir John Herschel
conjectures that those bright spots may possibly be insulated masses
of clouds of local origin, similar to the cumuli which sometimes cap
ascending columns of vapour in our atmosphere.

It would require nearly 1300 globes of the size of our earth to make
one of the bulk of Jupiter. A railway-engine travelling at the rate of
thirty-three miles an hour would travel round the earth in a month,
but would require more than eleven months to perform a journey round
Jupiter.


WAS SATURN’S RING KNOWN TO THE ANCIENTS?

In Maurice’s _Indian Antiquities_ is an engraving of Sani, the Saturn
of the Hindoos, taken from an image in a very ancient pagoda, which
represents the deity encompassed by a _ring_ formed of two serpents.
Hence it is inferred that the ancients were acquainted with the
existence of the ring of Saturn.

Arago mentions the remarkable fact of the ring and fourth satellite of
Saturn having been seen by Sir W. Herschel with his smaller telescope
by the naked eye, without any eye-piece.

The first or innermost of Saturn’s satellites is nearer to the central
body than any other of the secondary planets. Its distance from the
centre of Saturn is 80,088 miles; from the surface of the planet
47,480 miles; and from the outmost edge of the ring only 4916 miles.
The traveller may form to himself an estimate of the smallness of
this amount by remembering the statement of the well-known navigator,
Captain Beechey, that he had in three years passed over 72,800 miles.

According to very recent observations, Saturn’s ring is divided into
_three_ separate rings, which, from the calculations of Mr. Bond, an
American astronomer, must be fluid. He is of opinion that the number
of rings is continually changing, and that their maximum number, in
the normal condition of the mass, does not exceed _twenty_. Mr. Bond
likewise maintains that the power which sustains the centre of gravity
of the _ring_ is not in the planet itself, but in its satellites; and
the satellites, though constantly disturbing the ring, actually sustain
it in the very act of perturbation. M. Otto Struve and Mr. Bond have
lately studied with the great Munich telescope, at the observatory of
Pulkowa, the _third_ ring of Saturn, which Mr. Lassell and Mr. Bond
discovered to be _fluid_. They saw distinctly the dark interval between
this fluid ring and the two old ones, and even measured its dimensions;
and they perceived at its inner margin an edge feebly illuminated,
which they thought might be the commencement of a fourth ring. These
astronomers are of opinion, that the fluid ring is not of very recent
formation, and that it is not subject to rapid change; and they have
come to the extraordinary conclusion, that the inner border of the ring
has, since the time of Huygens, been gradually approaching to the body
of Saturn, and that _we may expect, sooner or later, perhaps in some
dozen of years, to see the rings united with the body of the planet_.
But this theory is by other observers pronounced untenable.


TEMPERATURE OF THE PLANET MERCURY.

Mercury being so much nearer to the Sun than the Earth, he receives,
it is supposed, seven times more heat than the earth. Mrs. Somerville
says: “On Mercury, the mean heat arising from the intensity of the
sun’s rays must be above that of boiling quicksilver, and water would
boil even at the poles.” But he may be provided with an atmosphere
so constituted as to absorb or reflect a great portion of the
superabundant heat; so that his inhabitants (if he have any) may enjoy
a climate as temperate as any on our globe.


SPECULATIONS ON VESTA AND PALLAS.

The most remarkable peculiarities of these ultra-zodiacal planets,
according to Sir John Herschel, must lie in this condition of their
state: a man placed on one of them would spring with ease sixty feet
high, and sustain no greater shock in his descent than he does on the
earth from leaping a yard. On such planets, giants might exist; and
those enormous animals which on the earth require the buoyant power of
water to counteract their weight, might there be denizens of the land.
But of such speculations there is no end.


IS THE PLANET MARS INHABITED?

The opponents of the doctrine of the Plurality of Worlds allow that a
greater probability exists of Mars being inhabited than in the case of
any other planet. His diameter is 4100 miles; and his surface exhibits
spots of different hues,--the _seas_, according to Sir John Herschel,
being _green_, and the land _red_. “The variety in the spots,” says
this astronomer, “may arise from the planet not being destitute of
atmosphere and cloud; and what adds greatly to the probability of this,
is the appearance of brilliant white spots at its poles, which have
been conjectured, with some probability, to be snow, as they disappear
when they have been long exposed to the sun, and are greatest when
emerging from the long night of their polar winter, the snow-line then
extending to about six degrees from the pole.” “The length of the day,”
says Sir David Brewster, “is almost exactly twenty-four hours,--the
same as that of the earth. Continents and oceans and green savannahs
have been observed upon Mars, and the snow of his polar regions has
been seen to disappear with the heat of summer.” We actually see the
clouds floating in the atmosphere of Mars, and there is the appearance
of land and water on his disc. In a sketch of this planet, as seen in
the pure atmosphere of Calcutta by Mr. Grant, it appears, to use his
words, “actually as a little world,” and as the earth would appear at
a distance, with its seas and continents of different shades. As the
diameter of Mars is only about one half that of our earth, the weight
of bodies will be about one half what it would be if they were placed
upon our globe.


DISCOVERY OF THE PLANET NEPTUNE.

This noble discovery marked in a signal manner the maturity of
astronomical science. The proof, or at least the urgent presumption,
of the existence of such a planet, as a means of accounting (by its
attraction) for certain small irregularities observed in the motions
of Uranus, was afforded almost simultaneously by the independent
researches of two geometers, Mr. Adams of Cambridge, and M. Leverrier
of Paris, who were enabled _from theory alone_ to calculate whereabouts
it ought to appear in the heavens, _if visible_, the places thus
independently calculated agreeing surprisingly. _Within a single
degree_ of the place assigned by M. Leverrier’s calculations, and by
him communicated to Dr. Galle of the Royal Observatory at Berlin, it
was actually found by that astronomer on the very first night after
the receipt of that communication, on turning a telescope on the spot,
and comparing the stars in its immediate neighbourhood with those
previously laid down in one of the zodiacal charts. This remarkable
verification of an indication so extraordinary took place on the 23d of
September 1846.[20]--_Sir John Herschel’s Outlines._

Neptune revolves round the sun in about 172 years, at a mean distance
of thirty,--that of Uranus being nineteen, and that of the earth one:
and by its discovery the solar system has been extended _one thousand
millions of miles_ beyond its former limit.

Neptune is suspected to have a ring, but the suspicion has not been
confirmed. It has been demonstrated by the observations of Mr. Lassell,
M. Otto Struve, and Mr. Bond, to be attended by at least one satellite.

One of the most curious facts brought to light by the discovery of
Neptune, is the failure of Bode’s law to give an approximation to its
distance from the sun; a striking exemplification of the danger of
trusting to the universal applicability of an empirical law. After
standing the severe test which led to the discovery of the asteroids,
it seemed almost contrary to the laws of probability that the discovery
of another member of the planetary system should prove its failure as
an universal rule.


MAGNITUDE OF COMETS.

Although Comets have a smaller mass than any other cosmical
bodies--being, according to our present knowledge, probably not equal
to 1/5000th part of the earth’s mass--yet they occupy the largest
space, as their tails in several instances extend over many millions of
miles. The cone of luminous vapour which radiates from them has been
found in some cases (as in 1680 and 1811) equal to the length of the
earth’s distance from the sun, forming a line that intersects both the
orbits of Venus and Mercury. It is even probable that the vapour of
the tails of comets mingled with our atmosphere in the years 1819 and
1823.--_Humboldt’s Cosmos_, vol. i.


COMETS VISIBLE IN SUNSHINE--THE GREAT COMET OF 1843.

The phenomenon of the tail of a Comet being visible in bright Sunshine,
which is recorded of the comet of 1402, occurred again in the case of
the large comet of 1843, whose nucleus and tail were seen in North
America on February 28th (according to the testimony of J. G. Clarke,
of Portland, State of Maine), between one and three o’clock in the
afternoon. The distance of the very dense nucleus from the sun’s
light admitted of being measured with much exactness. The nucleus and
tail (a darker space intervening) appeared like a very pure white
cloud.--_American Journal of Science_, vol. xiv.

E. C. Otté, the translator of Bohn’s edition of Humboldt’s _Cosmos_,
at New Bedford, Massachusetts, U.S., Feb. 28th, 1843, distinctly saw
the above comet between one and two in the afternoon. The sky at the
time was intensely blue, and the sun shining with a dazzling brightness
unknown in European climates.

This very remarkable Comet, seen in England on the 17th of March
1843, had a nucleus with the appearance of a planetary disc, and the
brightness of a star of the first or second magnitude. It had a double
tail divided by a dark line. At the Cape of Good Hope it was seen in
full daylight, and in the immediate vicinity of the sea; but the most
remarkable fact in its history was its near approach to the sun, its
distance from his surface being only _one-fourteenth_ of his diameter.
The heat to which it was exposed, therefore, was much greater than that
which Sir Isaac Newton ascribed to the comet of 1680, namely 200 times
that of red-hot iron. Sir John Herschel has computed that it must have
been 24 times greater than that which was produced in the focus of
Parker’s burning lens, 32 inches in diameter, which melts crystals of
quartz and agate.[21]


THE MILKY WAY UNFATHOMABLE.

M. Struve of Pulkowa has compared Sir William Herschel’s opinion
on this subject, as maintained in 1785, with that to which he was
subsequently led; and arrives at the conclusion that, according to Sir
W. Herschel himself, the visible extent of the Milky Way increases with
the penetrating power of the telescopes employed; that it is impossible
to discover by his instruments the termination of the Milky Way (as an
independent cluster of stars); and that even his gigantic telescope of
forty feet focal length does not enable him to extend our knowledge
of the Milky Way, which is incapable of being sounded. Sir William
Herschel’s _Theory of the Milky Way_ was as follows: He considered
our solar system, and all the stars which we can see with the eye, as
placed within, and constituting a part of, the nebula of the Milky Way,
a congeries of many millions of stars, so that the projection of these
stars must form a luminous track on the concavity of the sky; and by
estimating or counting the number of stars in different directions, he
was able to form a rude judgment of the probable form of the nebula,
and of the probable position of the solar system within it.

This remarkable belt has maintained from the earliest ages the same
relative situation among the stars; and, when examined through powerful
telescopes, is found (wonderful to relate!) _to consist entirely of
stars scattered by millions_, like glittering dust, on the black ground
of the general heavens.


DISTANCES OF NEBULÆ.

These are truly astounding. Sir William Herschel estimated the distance
of the annular nebula between Beta and Gamma Lyræ to be from our system
950 times that of Sirius; and a globular cluster about 5½° south-east
of Beta Sir William computed to be one thousand three hundred billions
of miles from our system. Again, in Scutum Sobieski is one nebula in
the shape of a horseshoe; but which, when viewed with high magnifying
power, presents a different appearance. Sir William Herschel estimated
this nebula to be 900 times farther from us than Sirius. In some parts
of its vicinity he observed 588 stars in his telescope at one time;
and he counted 258,000 in a space 10° long and 2½° wide. There is a
globular cluster between the mouths of Pegasus and Equuleus, which
Sir William Herschel estimated to be 243 times farther from us than
Sirius. Caroline Herschel discovered in the right foot of Andromeda
a nebula of enormous dimensions, placed at an inconceivable distance
from us: it consists probably of myriads of solar systems, which, taken
together, are but a point in the universe. The nebula about 10° west of
the principal star in Triangulum is supposed by Sir William Herschel
to be 344 times the distance of Sirius from the earth, which would be
the immense sum of nearly seventeen thousand billions of miles from our
planet.


INFINITE SPACE.

After the straining mind has exhausted all its resources in attempting
to fathom the distance of the smallest telescopic star, or the faintest
nebula, it has reached only the visible confines of the sidereal
creation. The universe of stars is but an atom in the universe of
space; above it, and beneath it, and around it, there is still infinity.


ORIGIN OF OUR PLANETARY SYSTEM. THE NEBULAR HYPOTHESIS.[22]

The commencement of our Planetary System, including the sun, must,
according to Kant and Laplace, be regarded as an immense nebulous mass
filling the portion of space which is now occupied by our system far
beyond the limits of Neptune, our most distant planet. Even now we
perhaps see similar masses in the distant regions of the firmament, as
patches of nebulæ, and nebulous stars; within our system also, comets,
the zodiacal light, the corona of the sun during a total eclipse,
exhibit resemblances of a nebulous substance, which is so thin that the
light of the stars passes through it unenfeebled and unrefracted. If we
calculate the density of the mass of our planetary system, according
to the above assumption, for the time when it was a nebulous sphere
which reached to the path of the outmost planet, we should find that
it would require several cubic miles of such matter to weigh a single
grain.--_Professor Helmholtz._

A quarter of a century ago, Sir John Herschel expressed his opinion
that those nebulæ which were not resolved into individual stars by the
highest powers then used, might be hereafter completely resolved by a
further increase of optical power:

  In fact, this probability has almost been converted into a
  certainty by the magnificent reflecting telescope constructed by
  Lord Rosse, of 6 feet in aperture, which has resolved, or rendered
  resolvable, multitudes of nebulæ which had resisted all inferior
  powers. The sublimity of the spectacle afforded by that instrument
  of some of the larger globular and other clusters is declared by
  all who have witnessed it to be such as no words can express.[23]

  Although, therefore, nebulæ do exist, which even in this powerful
  telescope appear as nebulæ, without any sign of resolution, it may
  very reasonably be doubted whether there be really any essential
  physical distinction between nebulæ and clusters of stars, at least
  in the nature of the matter of which they consist; and whether the
  distinction between such nebulæ as are easily resolved, barely
  resolvable with excellent telescopes, and altogether irresolvable
  with the best, be any thing else than one of degree, arising merely
  from the excessive minuteness and multitude of the stars of which
  the latter, as compared with the former, consist.--_Outlines of
  Astronomy_, 5th edit. 1858.

It should be added, that Sir John Herschel considers the “nebular
hypothesis” and the above theory of sidereal aggregation to stand quite
independent of each other.


ORIGIN OF HEAT IN OUR SYSTEM.

Professor Helmholtz, assuming that at the commencement the density of
the nebulous matter was a vanishing quantity, as compared with the
present density of the sun and planets, calculates how much work has
been performed by the condensation; how much of this work still exists
in the form of mechanical force, as attraction of the planets towards
the sun, and as _vis viva_ of their motion; and finds by this how much
of the force has been converted into heat.

  The result of this calculation is, that only about the 45th part
  of the original mechanical force remains as such, and that the
  remainder, converted into heat, would be sufficient to raise a
  mass of water equal to the sun and planets taken together, not
  less than 28,000,000 of degrees of the centigrade scale. For the
  sake of comparison, Professor Helmholtz mentions that the highest
  temperature which we can produce by the oxy-hydrogen blowpipe,
  which is sufficient to vaporise even platina, and which but few
  bodies can endure, is estimated at about 2000 degrees. Of the
  action of a temperature of 28,000,000 of such degrees we can form
  no notion. If the mass of our entire system were of pure coal, by
  the combustion of the whole of it only the 350th part of the above
  quantity would be generated.

  The store of force at present possessed by our system is equivalent
  to immense quantities of heat. If our earth were by a sudden shock
  brought to rest in her orbit--which is not to be feared in the
  existing arrangement of our system--by such a shock a quantity of
  heat would be generated equal to that produced by the combustion of
  fourteen such earths of solid coal. Making the most unfavourable
  assumption as to its capacity for heat, that is, placing it equal
  to that of water, the mass of the earth would thereby be heated
  11,200°; it would therefore be quite fused, and for the most part
  reduced to vapour. If, then, the earth, after having been thus
  brought to rest, should fall into the sun, which of course would be
  the case, the quantity of heat developed by the shock would be 400
  times greater.


AN ASTRONOMER’S DREAM VERIFIED.

The most fertile region in astronomical discovery during the last
quarter of a century has been the planetary members of the solar
system. In 1833, Sir John Herschel enumerated ten planets as visible
from the earth, either by the unaided eye or by the telescope; the
number is now increased more than fivefold. With the exception of
Neptune, the discovery of new planets is confined to the class called
Asteroids. These all revolve in elliptic orbits between those of
Jupiter and Mars. Zitius of Wittemberg discovered an empirical law,
which seemed to govern the distances of the planets from the sun; but
there was a remarkable interruption in the law, according to which a
planet ought to have been placed between Mars and Jupiter. Professor
Bode of Berlin directed the attention of astronomers to the possibility
of such a planet existing; and in seven years’ observations from the
commencement of the present century, not one but four planets were
found, differing widely from one another in the elements of their
orbits, but agreeing very nearly at their mean distances from the sun
with that of the supposed planet. This curious coincidence of the mean
distances of these four asteroids with the planet according to Bode’s
law, as it is generally called, led to the conjecture that these four
planets were but fragments of the missing planet, blown to atoms by
some internal explosion, and that many more fragments might exist, and
be possibly discovered by diligent search.

Concerning this apparently wild hypothesis, Sir John Herschel offered
the following remarkable apology: “This may serve as a specimen of the
dreams in which astronomers, like other speculators, occasionally and
harmlessly indulge.”

The dream, wild as it appeared, has been realised now. Sir John, in the
fifth edition of his _Outlines of Astronomy_, published in 1858, tells
us:

  Whatever may be thought of such a speculation as a physical
  hypothesis, this conclusion has been verified to a considerable
  extent as a matter of fact by subsequent discovery, the result
  of a careful and minute examination and mapping down of the
  smaller stars in and near the zodiac, undertaken with that express
  object. Zodiacal charts of this kind, the product of the zeal and
  industry of many astronomers, have been constructed, in which
  every star down to the ninth, tenth, or even lower magnitudes, is
  inserted; and these stars being compared with the actual stars of
  the heavens, the intrusion of any stranger within their limits
  cannot fail to be noticed when the comparison is systematically
  conducted. The discovery of Astræa and Hebe by Professor Hencke,
  in 1845 and 1847, revived the flagging spirit of inquiry in this
  direction; with what success, the list of fifty-two asteroids,
  with their names and the dates of their discovery, will best show.
  The labours of our indefatigable countryman, Mr. Hind, have been
  rewarded by the discovery of no less than eight of them.


FIRE-BALLS AND SHOOTING STARS.

Humboldt relates, that a friend at Popayan, at an elevation of 5583
feet above the sea-level, at noon, when the sun was shining brightly
in a cloudless sky, saw his room lighted up by a fire-ball: he had his
back towards the window at the time, and on turning round, perceived
that great part of the path traversed by the fire-ball was still
illuminated by the brightest radiance. The Germans call these phenomena
_star-snuff_, from the vulgar notion that the lights in the firmament
undergo a process of snuffing, or cleaning. Other nations call it _a
shot or fall of stars_, and the English _star-shoot_. Certain tribes
of the Orinoco term the pearly drops of dew which cover the beautiful
leaves of the heliconia _star-spit_. In the Lithuanian mythology, the
nature and signification of falling stars are embodied under nobler and
more graceful symbols. The Parcæ, _Werpeja_, weave in heaven for the
new-born child its thread of fate, attaching each separate thread to
a star. When death approaches the person, the thread is rent, and the
star wanes and sinks to the earth.--_Jacob Grimm._


THEORY AND EXPERIENCE.

In the perpetual vicissitude of theoretical views, says the author of
_Giordano Bruno_, “most men see nothing in philosophy but a succession
of passing meteors; whilst even the grander forms in which she has
revealed herself share the fate of comets,--bodies that do not rank in
popular opinion amongst the external and permanent works of nature, but
are regarded as mere fugitive apparitions of igneous vapour.”


METEORITES FROM THE MOON.

The hypothesis of the selenic origin of meteoric stones depends upon
a number of conditions, the accidental coincidence of which could
alone convert a possible to an actual fact. The view of the original
existence of small planetary masses in space is simpler, and at
the same time more analogous with those entertained concerning the
formation of other portions of the solar system.

  Diogenes Laertius thought aerolites came from the sun; but Pliny
  derides this theory. The fall of aerolites in bright sunshine, and
  when the moon’s disc was invisible, probably led to the idea of
  sun-stones. Moreover Anaxagoras regarded the sun as “a molten fiery
  mass;” and Euripides, in Phaëton, terms the sun “a golden mass,”
  that is to say, a fire-coloured, brightly-shining matter, but not
  leading to the inference that aerolites are golden sun-stones.
  The Greek philosophers had four hypotheses as to their origin:
  telluric, from ascending exhalations; masses of stone raised by
  hurricanes; a solar origin; and lastly, an origin in the regions of
  space, as heavenly bodies which had long remained invisible: the
  last opinion entirely according with that of the present day.

  Chladni states that an Italian physicist, Paolo Maria Terzago,
  on the occasion of the fall of an aerolite at Milan, in 1660, by
  which a Franciscan monk was killed, was the first who surmised that
  aerolites were of selenic origin. Without any previous knowledge
  of this conjecture, Olbers was led, in 1795 (after the celebrated
  fall at Siena, June 16th, 1794), to investigate the amount of the
  initial tangential force that would be required to bring to the
  earth masses projected from the moon. Olbers, Brandes, and Chaldni
  thought that “the velocity of 16 to 32 miles, with which fire-balls
  and shooting-stars entered our atmosphere,” furnished a refutation
  to the view of their selenic origin. According to Olbers, it would
  require to reach the earth, setting aside the resistance of the
  air, an initial velocity of 8292 feet in the second; according to
  Laplace, 7862; to Biot, 8282; and to Poisson, 7595. Laplace states
  that this velocity is only five or six times as great as that of
  a cannon-ball; but Olbers has shown that “with such an initial
  velocity as 7500 or 8000 feet in a second, meteoric stones would
  arrive at the surface of our earth with a velocity of only 35,000
  feet.” But the measured velocity of meteoric stones averages
  upwards of 114,000 feet to a second; consequently the original
  velocity of projection from the moon must be almost 110,000 feet,
  and therefore 14 times greater than Laplace asserted. It must,
  however, be recollected, that the opinion then so prevalent, of the
  existence of active volcanoes in the moon, where air and water are
  absent, has since been abandoned.

  Laplace elsewhere states, that in all probability aerolites “come
  from the depths of space;” yet he in another passage inclines to
  the hypothesis of their lunar origin, always, however, assuming
  that the stones projected from the moon “become satellites of our
  earth, describing around it more or less eccentric orbits, and thus
  not reaching its atmosphere until several or even many revolutions
  have been accomplished.”

  In Syria there is a popular belief that aerolites chiefly fall
  on clear moonlight nights. The ancients (Pliny tells us) looked
  for their fall during lunar eclipses.--_Abridged from Humboldt’s
  Cosmos_, vol. i. (Bohn’s edition).

Dr. Laurence Smith, U.S., accepts the “lunar theory,” and considers
meteorites to be masses thrown off from the moon, the attractive power
of which is but one-sixth that of the earth; so that bodies thrown from
the surface of the moon experience but one sixth the retarding force
they would have when thrown from the earth’s surface.

  Look again (says Dr. Smith) at the constitution of the meteorite,
  made up principally of _pure_ iron. It came evidently from some
  place where there is little or no oxygen. Now the moon has no
  atmosphere, and no water on its surface. There is no oxygen there.
  Hurled from the moon, these bodies,--these masses of almost pure
  iron,--would flame in the sun like polished steel, and on reaching
  our atmosphere would burn in its oxygen until a black oxide cooled
  it; and this we find to be the case with all meteorites,--the
  black colour is only an external covering.

Sir Humphry Davy, from facts contained in his researches on flame,
in 1817, conceives that the light of meteors depends, not upon the
ignition of inflammable gases, but upon that of solid bodies; that such
is their velocity of motion, as to excite sufficient heat for their
ignition by the compression even of rare air; and that the phenomena of
falling stars may be explained by regarding them as small incombustible
bodies moving round the earth in very eccentric orbits, and becoming
ignited only when they pass with immense rapidity through the upper
regions of the atmosphere; whilst those meteors which throw down stony
bodies are, similarly circumstanced, combustible masses.

Masses of iron and nickel, having all the appearance of aerolites or
meteoric stones, have been discovered in Siberia, at a depth of ten
metres below the surface of the earth. From the fact, however, that no
meteoric stones are found in the secondary and tertiary formations, it
would seem to follow that the phenomena of falling stones did not take
place till the earth assumed its present conditions.


VAST SHOWER OF METEORS.

The most magnificent Shower of Meteors that has ever been known was
that which fell during the night of November 12th, 1833, commencing
at nine o’clock in the evening, and continuing till the morning sun
concealed the meteors from view. This shower extended from Canada to
the northern boundary of South America, and over a tract of nearly 3000
miles in width.


IMMENSE METEORITE.

Mrs. Somerville mentions a Meteorite which passed within twenty-five
miles of our planet, and was estimated to weigh 600,000 tons, and to
move with a velocity of twenty miles in a second. Only a small fragment
of this immense mass reached the earth. Four instances are recorded
of persons being killed by their fall. A block of stone fell at Ægos
Potamos, B.C. 465, as large as two millstones; another at Narni, in
921, projected like a rock four feet above the surface of the river,
in which it was seen to fall. The Emperor Jehangire had a sword forged
from a mass of meteoric iron, which fell in 1620 at Jahlinder in the
Punjab. Sixteen instances of the fall of stones in the British Isles
are well authenticated to have occurred since 1620, one of them in
London. It is very remarkable that no new chemical element has been
detected in any of the numerous meteorites which have been analysed.


NO FOSSIL METEORIC STONES.

It is (says Olbers) a remarkable but hitherto unregarded fact, that
while shells are found in secondary and tertiary formations, no Fossil
Meteoric Stones have as yet been discovered. May we conclude from this
circumstance, that previous to the present and last modification of the
earth’s surface no meteoric stones fell on it, though at the present
time it appears probable, from the researches of Schreibers, that 700
fall annually?[24]


THE END OF OUR SYSTEM.

While all the phenomena in the heavens indicate a law of progressive
creation, in which revolving matter is distributed into suns and
planets, there are indications in our own system that a period has been
assigned for its duration, which, sooner or later, it must reach. The
medium which fills universal space, whether it be a luminiferous ether,
or arise from the indefinite expansion of planetary atmospheres, must
retard the bodies which move in it, even were it 360,000 millions of
times more rare than atmospheric air; and, with its time of revolution
gradually shortening, the satellite must return to its planet, the
planet to its sun, and the sun to its primeval nebula. The fate of our
system, thus deduced from mechanical laws, must be the fate of all
others. Motion cannot be perpetuated in a resisting medium; and where
there exist disturbing forces, there must be primarily derangement,
and ultimately ruin. From the great central mass, heat may again be
summoned to exhale nebulous matter; chemical forces may again produce
motion, and motion may again generate systems; but, as in the recurring
catastrophes which have desolated our earth, the great First Cause must
preside at the dawn of each cosmical cycle; and, as in the animal races
which were successively reproduced, new celestial creations of a nobler
form of beauty and of a higher form of permanence may yet appear in
the sidereal universe. “Behold, I create new heavens and a new earth,
and the former shall not be remembered.” “The new heavens and the
new earth shall remain before me.” “Let us look, then, according to
this promise, for the new heavens and the new earth, wherein dwelleth
righteousness.”--_North-British Review_, No. 3.


BENEFITS OF GLASS TO MAN.

Cuvier eloquently says: “It could not be expected that those Phœnician
sailors who saw the sand of the shores of Bætica transformed by fire
into a transparent Glass, should have at once foreseen that this new
substance would prolong the pleasures of sight to the old; that it
would one day assist the astronomer in penetrating the depths of the
heavens, and in numbering the stars of the Milky Way; that it would
lay open to the naturalist a miniature world, as populous, as rich in
wonders as that which alone seemed to have been granted to his senses
and his contemplation: in fine, that the most simple and direct use
of it would enable the inhabitants of the coast of the Baltic Sea to
build palaces more magnificent than those of Tyre and Memphis, and to
cultivate, almost under the polar circle, the most delicious fruit of
the torrid zone.”


THE GALILEAN TELESCOPE.

Galileo appears to be justly entitled to the honour of having invented
that form of Telescope which still bears his name; while we must accord
to John Lippershey, the spectacle-maker of Middleburg, the honour of
having previously invented the astronomical telescope. The interest
excited at Venice by Galileo’s invention amounted almost to frenzy.
On ascending the tower of St. Mark, that he might use one of his
telescopes without molestation, Galileo was recognised by a crowd in
the street, who took possession of the wondrous tube, and detained the
impatient philosopher for several hours, till they had successively
witnessed its effects. These instruments were soon manufactured in
great numbers; but were purchased merely as philosophical toys, and
were carried by travellers into every corner of Europe.


WHAT GALILEO FIRST SAW WITH HIS TELESCOPE.

The moon displayed to him her mountain-ranges and her glens, her
continents and her highlands, now lying in darkness, now brilliant with
sunshine, and undergoing all those variations of light and shadow which
the surface of our own globe presents to the alpine traveller or to the
aeronaut. The four satellites of Jupiter illuminating their planet, and
suffering eclipses in his shadow, like our own moon; the spots on the
sun’s disc, proving his rotation round his axis in twenty-five days;
the crescent phases of Venus, and the triple form or the imperfectly
developed ring of Saturn,--were the other discoveries in the solar
system which rewarded the diligence of Galileo. In the starry heavens,
too, thousands of new worlds were discovered by his telescope; and the
Pleiades alone, which to the unassisted eye exhibit only _seven_ stars,
displayed to Galileo no fewer than _forty_.--_North-British Review_,
No. 3.

  The first telescope “the starry Galileo” constructed with a leaden
  tube a few inches long, with a spectacle-glass, one convex and one
  concave, at each of its extremities. It magnified three times.
  Telescopes were made in London in February 1610, a year after
  Galileo had completed his own (Rigaud, _On Harriot’s Papers_,
  1833). They were at first called _cylinders_. The telescopes which
  Galileo constructed, and others of which he made use for observing
  Jupiter’s satellites, the phases of Venus, and the solar spots,
  possessed the gradually-increasing powers of magnifying four,
  seven, and thirty-two linear diameters; but they never had a higher
  power.--Arago, in the _Annuaire_ for 1842.

  Clock-work is now applied to the equatorial telescope, so as to
  allow the observer to follow the course of any star, comet, or
  planet he may wish to observe continuously, without using his hands
  for the mechanical motion of the instrument.


ANTIQUITY OF TELESCOPES.

Long tubes were certainly employed by Arabian astronomers, and very
probably also by the Greeks and Romans; the exactness of their
observations being in some degree attributable to their causing the
object to be seen through diopters or slits. Abul Hassan speaks very
distinctly of tubes, to the extremities of which ocular and object
diopters were attached; and instruments so constructed were used in
the observatory founded by Hulagu at Meragha. If stars be more easily
discovered during twilight by means of tubes, and if a star be sooner
revealed to the naked eye through a tube than without it, the reason
lies, as Arago has truly observed, in the circumstance that the tube
conceals a great portion of the disturbing light diffused in the
atmospheric strata between the star and the eye applied to the tube.
In like manner, the tube prevents the lateral impression of the faint
light which the particles of air receive at night from all the other
stars in the firmament. The intensity of the image and the size of the
star are apparently augmented.--_Humboldt’s Cosmos_, vol. iii. p. 53.


NEWTON’S FIRST REFLECTING TELESCOPE.

The year 1668 may be regarded as the date of the invention of
Newton’s Reflecting Telescope. Five years previously, James Gregory
had described the manner of constructing a reflecting telescope with
two concave specula; but Newton perceived the disadvantages to be so
great, that, according to his statement, he “found it necessary, before
attempting any thing in the practice, to alter the design, and place
the eye-glass at the side of the tube rather than at the middle.” On
this improved principle Newton constructed his telescope, which was
examined by Charles II.; it was presented to the Royal Society near the
end of 1671, and is carefully preserved by that distinguished body,
with the inscription:

  “THE FIRST REFLECTING TELESCOPE; INVENTED BY SIR ISAAC NEWTON, AND
  MADE WITH HIS OWN HANDS.”

Sir David Brewster describes this telescope as consisting of a concave
metallic speculum, the radius of curvature of which was 12-2/3 or
13 inches, so that “it collected the sun’s rays at the distance of
6-1/3 inches.” The rays reflected by the speculum were received upon
a plane metallic speculum inclined 45° to the axis of the tube, so as
to reflect them to the side of the tube in which there was an aperture
to receive a small tube with a plano-convex eye-glass whose radius
was one-twelfth of an inch, by means of which the image formed by
the speculum was magnified 38 times. Such was the first reflecting
telescope applied to the heavens; but Sir David Brewster describes
this instrument as small and ill-made; and fifty years elapsed before
telescopes of the Newtonian form became useful in astronomy.


SIR WILLIAM HERSCHEL’S GREAT TELESCOPE AT SLOUGH.

The plan of this Telescope was intimated by Herschel, through Sir
Joseph Banks, to George III., who offered to defray the whole expense
of it; a noble act of liberality, which has never been imitated by
any other British sovereign. Towards the close of 1785, accordingly,
Herschel began to construct his reflecting telescope, _forty feet in
length_, and having a speculum _fully four feet in diameter_. The
thickness of the speculum, which was uniform in every part, was 3½
inches, and its weight nearly 2118 pounds; the metal being composed of
32 copper, and 10·7 of tin: it was the third speculum cast, the two
previous attempts having failed. The speculum, when not in use, was
preserved from damp by a tin cover, fitted upon a rim of close-grained
cloth. The tube of the telescope was 39 ft. 4 in. long, and its width 4
ft. 10 in.; it was made of iron, and was 3000 lbs. lighter than if it
had been made of wood. The observer was seated in a suspended movable
seat at the mouth of the tube, and viewed the image of the object with
a magnifying lens or eye-piece. The focus of the speculum, or place of
the image, was within four inches of the lower side of the mouth of the
tube, and came forward into the air, so that there was space for part
of the head above the eye, to prevent it from intercepting many of the
rays going from the object to the mirror. The eye-piece moved in a tube
carried by a slider directed to the centre of the speculum, and fixed
on an adjustible foundation at the mouth of the tube. It was completed
on the 27th August 1789; and _the very first moment_ it was directed to
the heavens, a new body was added to the solar system, namely, Saturn
and six of its satellites; and in less than a month after, the seventh
satellite of Saturn, “an object,” says Sir John Herschel, “of a far
higher order of difficulty.”--_Abridged from the North-British Review_,
No. 3.

  This magnificent instrument stood on the lawn in the rear of Sir
  William Herschel’s house at Slough; and some of our readers, like
  ourselves, may remember its extraordinary aspect when seen from
  the Bath coach-road, and the road to Windsor. The difficulty of
  managing so large an instrument--requiring as it did two assistants
  in addition to the observer himself and the person employed to note
  the time--prevented its being much used. Sir John Herschel, in a
  letter to Mr. Weld, states the entire cost of its construction,
  4000_l._, was defrayed by George III. In 1839, the woodwork of
  the telescope being decayed, Sir John Herschel had it cleared
  away; and piers were erected, on which the tube was placed, _that_
  being of iron, and so well preserved that, although not more than
  one-twentieth of an inch thick, when in the horizontal position
  it contained within all Sir John’s family; and next the two
  reflectors, the polishing apparatus, and portions of the machinery,
  to the amount of a great many tons. Sir John attributes this great
  strength and resistance to the internal structure of the tube, very
  similar to that patented under the name of corrugated iron-roping.
  Sir John Herschel also thinks that system of triangular arrangement
  of the woodwork was upon the principle to which “diagonal bracing”
  owes its strength.


THE EARL OF ROSSE’S GREAT REFLECTING TELESCOPE.

Sir David Brewster has remarked, that “the long interval of half
a century seems to be the period of hybernation during which the
telescopic mind rests from its labours in order to acquire strength for
some great achievement. Fifty years elapsed between the dwarf telescope
of Newton and the large instruments of Hadley; other fifty years rolled
on before Sir William Herschel constructed his magnificent telescope;
and fifty years more passed away before the Earl of Rosse produced
that colossal instrument which has already achieved such brilliant
discoveries.”[25]

In the improvement of the Reflecting Telescope, the first object
has always been to increase the magnifying power and light by the
construction of as large a mirror as possible; and to this point Lord
Rosse’s attention was directed as early as 1828, the field of operation
being at his lordship’s seat, Birr Castle at Parsonstown, about fifty
miles west of Dublin. For this high branch of scientific inquiry Lord
Rosse was well fitted by a rare combination of “talent to devise,
patience to bear disappointment, perseverance, profound mathematical
knowledge, mechanical skill, and uninterrupted leisure from other
pursuits;”[26] all these, however, would not have been sufficient, had
not a great command of money been added; the gigantic telescope we are
about to describe having cost certainly not less than twelve thousand
pounds.

  Lord Rosse ground and polished specula fifteen inches, two feet,
  and three feet in diameter before he commenced the colossal
  instrument. It is impossible here to detail the admirable
  contrivances and processes by which he prepared himself for this
  great work. He first ascertained the most useful combination of
  metals for specula, both in whiteness, porosity, and hardness,
  to be copper and tin. Of this compound the reflector was cast in
  pieces, which were fixed on a bed of zinc and copper,--a species
  of brass which expanded in the same degree by heat as the pieces
  of the speculum themselves. They were ground as one body to a true
  surface, and then polished by machinery moved by a steam-engine.
  The peculiarities of this mechanism were entirely Lord Rosse’s
  invention, and the result of close calculation and observation:
  they were chiefly, placing the speculum with the face upward,
  regulating the temperature by having it immersed in water, usually
  at 55° Fahr., and regulating the pressure and velocity. This was
  found to work a perfect spherical figure in large surfaces with
  a degree of precision unattainable by the hand; the polisher, by
  working above and upon the face of the speculum, being enabled
  to examine the operation as it proceeded without removing the
  speculum, which, when a ton weight, is no easy matter.

  The contrivance for doing this is very beautiful. The machine is
  placed in a room at the bottom of a high tower, in the successive
  floors of which trap-doors can be opened. A mast is elevated on the
  top of the tower, so that its summit is about ninety feet _above_
  the speculum. A dial-plate is attached to the top of the mast, and
  a small plane speculum and eye-piece, with proper adjustments,
  are so placed that the combination becomes a Newtonian telescope,
  and the dial-plate the object. The last and most important part
  of the process of working the speculum, is to give it a _true
  parabolic figure_, that is, such a figure that each portion of it
  should reflect the incident ray to the same focus. Lord Rosse’s
  operations for this purpose consist--1st, of a stroke of the first
  eccentric, which carries the polisher along _one-third_ of the
  diameter of the speculum; 2d, a transverse stroke twenty-one times
  slower, and equal to 0·27 of the same diameter, measured on the
  edge of the tank, or 1·7 beyond the centre of the polisher; 3d, a
  rotation of the speculum performed in the same time as thirty-seven
  of the first strokes; and 4th, a rotation of the polisher in the
  same direction about sixteen times slower. If these rules are
  attended to, the machine will give the true parabolic figure to the
  speculum, whether it be _six inches_ or _three feet in diameter_.
  In the three-feet speculum, the figure is so true with the whole
  aperture, that it is thrown out of focus by a motion of less
  than the _thirtieth of an inch_, “and even with a single lens of
  one-eighth of an inch focus, giving a power of 2592, the dots on a
  watch-dial are still in some degree defined.”

Thus was executed the three-feet speculum for the twenty-six-feet
telescope placed upon the lawn at Parsonstown, which, in 1840, showed
with powers up to 1000 and even 1600; and which resolved nebulæ into
stars, and destroyed that symmetry of form in globular nebulæ upon
which was founded the hypothesis of the gradual condensation of
nebulous matter into suns and planets.[27]

Scarcely was this instrument out of Lord Rosse’s hands, when he
resolved to attempt by the same processes to construct another
reflector, with a speculum _six feet_ in diameter and _fifty feet
long_! and this magnificent instrument was completed early in 1845.
The focal length of the speculum is fifty-four feet. It weighs four
tons, and, with its supports, is seven times as heavy as the four-feet
speculum of Sir William Herschel. The speculum is placed in one of
the sides of a cubical wooden box, about eight feet wide, and to the
opposite end of this box is fastened the tube, which is made of deal
staves an inch thick, hooped with iron clamp-rings, like a huge cask.
It carries at its upper end, and in the axis of the tube, a small oval
speculum, six inches in its lesser diameter.

The tube is about 50 feet long and 8 feet in diameter in the middle,
and furnished with diaphragms 6½ feet in aperture. The late Dean of Ely
walked through the tube with an umbrella up.

The telescope is established between two lofty castellated piers 60
feet high, and is raised to different altitudes by a strong chain-cable
attached to the top of the tube. This cable passes over a pulley on
a frame down to a windlass on the ground, which is wrought by two
assistants. To the frame are attached chain-guys fastened to the
counterweights; and the telescope is balanced by these counterweights
suspended by chains, which are fixed to the sides of the tube and pass
over large iron pulleys. The immense mass of matter weighs about twelve
tons.

On the eastern pier is a strong semicircle of cast-iron, with which the
telescope is connected by a racked bar, with friction-rollers attached
to the tube by wheelwork, so that by means of a handle near the
eye-piece, the observer can move the telescope along the bar on either
side of the meridian, to the distance of an hour for an equatorial star.

On the western pier are stairs and galleries. The observing gallery is
moved along a railway by means of wheels and a winch; and the mechanism
for raising the galleries to various altitudes is very ingenious.
Sometimes the galleries, filled with observers, are suspended midway
between the two piers, over a chasm sixty feet deep.

An excellent description of this immense Telescope at Birr Castle will
be found in Mr. Weld’s volume of _Vacation Rambles_.

Sir David Brewster thus eloquently sketches the powers of the telescope
at the close of his able description of the instrument, which we have
in part quoted from his _Life of Sir Isaac Newton_.

  We have, in the mornings, walked again and again, and ever with
  new delight, along its mystic tube, and at midnight, with its
  distinguished architect, pondered over the marvellous sights which
  it dis-closes,--the satellites and belts and rings of Saturn,--the
  old and new ring, which is advancing with its crest of waters to
  the body of the planet,--the rocks, and mountains, and valleys, and
  extinct volcanoes of the moon,--the crescent of Venus, with its
  mountainous outline,--the systems of double and triple stars,--the
  nebulæ and starry clusters of every variety of shape,--and those
  spiral nebular formations which baffle human comprehension, and
  constitute the greatest achievement in modern discovery.

The Astronomer Royal, Mr. Airy, alludes to the impression made by
the enormous light of the telescope,--partly by the modifications
produced in the appearance of nebulæ already figured, partly by the
great number of stars seen at a distance from the Milky Way, and
partly from the prodigious brilliancy of Saturn. The account given by
another astronomer of the appearance of Jupiter was that it resembled a
coach-lamp in the telescope; and this well expresses the blaze of light
which is seen in the instrument.

The Rev. Dr. Scoresby thus records the results of his visits:

  The range opened to us by the great telescope at Birr Castle is
  best, perhaps, apprehended by the now usual measurement--not of
  distances in miles, or millions of miles, or diameters of the
  earth’s orbit, but--of the progress of light in free space. The
  determination within, no doubt, a small proportion of error of
  the parallax of a considerable number of the fixed stars yields,
  according to Mr. Peters, a space betwixt us and the fixed stars of
  the smallest magnitude, the sixth, ordinarily visible to the naked
  eye, of 130 years in the flight of light. This information enables
  us, on the principles of _sounding the heavens_, suggested by Sir
  W. Herschel, with the photometrical researches on the stars of Dr.
  Wollaston and others, to carry the estimation of distances, and
  that by no means on vague assumption, to the limits of space opened
  out by the most effective telescopes. And from the guidance thus
  afforded us as to the comparative power of the six feet speculum
  in the penetration of space as already elucidated, we might fairly
  assume the fact, that if any other telescope now in use could
  follow the sun if removed to the remotest visible position, or
  till its light would require 10,000 years to reach us, the grand
  instrument at Parsonstown would follow it so far that from 20,000
  to 25,000 years would be spent in the transmission of its light to
  the earth. But in the cases of clusters of stars, and of nebulæ
  exhibiting a mere speck of misty luminosity, from the combined
  light of perhaps hundreds of thousands of suns, the _penetration_
  into space, compared with the results of ordinary vision, must
  be enormous; so that it would not be difficult to show the
  _probability_ that a million of years, in flight of light, would
  be requisite, in regard to the most distant, to trace the enormous
  interval.


GIGANTIC TELESCOPES PROPOSED.

Hooke is said to have proposed the use of Telescopes having a length of
upwards of 10,000 feet (or nearly two miles), in order to see animals
in the moon! an extravagant expectation which Auzout considered it
necessary to refute. The Capuchin monk Schyrle von Rheita, who was well
versed in optics, had already spoken of the speedy practicability of
constructing telescopes that should magnify 4000 times, by means of
which the lunar mountains might be accurately laid down.

Optical instruments of such enormous focal lengths remind us of the
Arabian contrivances of measurement: quadrants with a radius of about
190 feet, upon whose graduated limb the image of the sun was received
as in the gnomon, through a small round aperture. Such a quadrant was
erected at Samarcand, probably constructed after the model of the older
sextants of Alchokandi, which were about sixty feet in height.


LATE INVENTION OF OPTICAL INSTRUMENTS.

A writer in the _North-British Review_, No. 50, considers it strange
that a variety of facts which must have presented themselves to the
most careless observer should not have led to the earlier construction
of Optical Instruments. The ancients, doubtless, must have formed
metallic articles with concave surfaces, in which the observer could
not fail to see himself magnified; and if the radius of the concavity
exceeded twelve inches, twice the focal distance of his eye, he had in
his hands an extempore reflecting telescope of the Newtonian form, in
which the concave metal was the speculum, and his eye the eye-glass,
and which would magnify and bring near him the image of objects nearly
behind him. Through the spherical drops of water suspended before his
eye, an attentive observer might have seen magnified some minute body
placed accidentally in its anterior focus; and in the eyes of fishes
and quadrupeds which he used for his food, he might have seen, and
might have extracted, the beautiful lenses which they contain, and
which he could not fail to regard as the principal agents in the vision
of the animals to which they belonged. Curiosity might have prompted
him to look through these remarkable lenses or spheres; and had he
placed the lens of the smallest minnow, or that of the bird, the sheep,
or the ox, in or before a circular aperture, he would have produced a
microscope or microscopes of excellent quality and different magnifying
powers. No such observations seem, however, to have been made; and even
after the invention of glass, and its conversion into globular vessels,
through which, when filled with any fluid, objects are magnified, the
microscope remained undiscovered.


A TRIAD OF CONTEMPORARY ASTRONOMERS.

It is a remarkable fact in the history of astronomy (says Sir
David Brewster), that three of its most distinguished professors
were contemporaries. Galileo was the contemporary of Tycho during
thirty-seven years, and of Kepler during the fifty-nine years
of his life. Galileo was born seven years before Kepler, and
survived him nearly the same time. We have not learned that the
intellectual triumvirate of the age enjoyed any opportunity for mutual
congratulation. What a privilege would it have been to have contrasted
the aristocratic dignity of Tycho with the reckless ease of Kepler, and
the manly and impetuous mien of the Italian sage!--_Brewster’s Life of
Newton._


A PEASANT ASTRONOMER.

At about the same time that Goodricke discovered the variation of
the remarkable periodical star Algol, or β Persei, one Palitzch, a
farmer of Prolitz, near Dresden,--a peasant by station, an astronomer
by nature,--from his familiar acquaintance with the aspect of the
heavens, was led to notice, among so many thousand stars, Algol,
as distinguished from the rest by its variation, and ascertained
its period. The same Palitzch was also the first to re-discover
the predicted comet of Halley in 1759, which he saw nearly a month
before any of the astronomers, who, armed with their telescopes, were
anxiously watching its return. These anecdotes carry us back to the era
of the Chaldean shepherds.--_Sir John Herschel’s Outlines._


SHIRBURN-CASTLE OBSERVATORY.

Lord Macclesfield, the eminent mathematician, who was twelve years
President of the Royal Society, built at his seat, Shirburn Castle
in Oxfordshire, an Observatory, about 1739. It stood 100 yards south
from the castle-gate, and consisted of a bed-chamber, a room for the
transit, and the third for a mural quadrant. In the possession of
the Royal Astronomical Society is a curious print representing two
of Lord Macclesfield’s servants taking observations in the Shirburn
observatory; they are Thomas Phelps, aged 82, who, from being a
stable-boy to Lord-Chancellor Macclesfield, rose by his merit and
genius to be appointed observer. His companion is John Bartlett,
originally a shepherd, in which station he, by books and observation,
acquired such a knowledge in computation, and of the heavenly bodies,
as to induce Lord Macclesfield to appoint him assistant-observer in
his observatory. Phelps was the person who, on December 23d, 1743,
discovered the great comet, and made the first observation of it; an
account of which is entered in the _Philosophical Transactions_, but
not the name of the observer.


LACAILLE’S OBSERVATORY.

Lacaille, who made more observations than all his contemporaries put
together, and whose researches will have the highest value as long as
astronomy is cultivated, had an observatory at the Collège Mazarin,
part of which is now the Palace of the Institute, at Paris.

  For a long time it had been without observer or instruments;
  under Napoleon’s reign it was demolished. Lacaille never used
  to illuminate the wires of his instruments. The inner part of
  his observatory was painted black; he admitted only the faintest
  light, to enable him to see his pendulum and his paper: his left
  eye was devoted to the service of looking to the pendulum, whilst
  his right eye was kept shut. The latter was only employed to look
  to the telescope, and during the time of observation never opened
  but for this purpose. Thus the faintest light made him distinguish
  the wires, and he very seldom felt the necessity of illuminating
  them. Part of these blackened walls were visible long after the
  demolition of the observatory, which took place somewhat about
  1811.--_Professor Mohl._


NICETY REQUIRED IN ASTRONOMICAL CALCULATIONS.

In the _Edinburgh Review_, 1850, we find the following illustrations of
the enormous propagation of minute errors:

  The rod used in measuring a base-line is commonly about ten
  feet long; and the astronomer may be said truly to apply that
  very rod to mete the distance of the stars. An error in placing
  a fine dot which fixes the length of the rod, amounting to
  one-five-thousandth of an inch (the thickness of a single silken
  fibre), will amount to an error of 70 feet in the earth’s diameter,
  of 316 miles in the sun’s distance, and to 65,200,000 miles in
  that of the nearest fixed star. Secondly, as the astronomer in his
  observatory has nothing further to do with ascertaining lengths or
  distances, except by calculation, his whole skill and artifice are
  exhausted in the measurement of angles; for by these alone spaces
  inaccessible can be compared. Happily, a ray of light is straight:
  were it not so (in celestial spaces at least), there would be an
  end of our astronomy. Now an angle of a second (3600 to a degree)
  is a subtle thing. It has an apparent breadth utterly invisible to
  the unassisted eye, unless accompanied with so intense a splendour
  (_e. g._ in the case of a fixed star) as actually to raise by its
  effect on the nerve of sight a spurious image having a sensible
  breadth. A silkworm’s fibre, such as we have mentioned above,
  subtends an angle of a second at 3½ feet distance; a cricket-ball,
  2½ inches diameter, must be removed, in order to subtend a second,
  to 43,000 feet, or about 8 miles, where it would be utterly
  invisible to the sharpest sight aided even by a telescope of some
  power. Yet it is on the measure of one single second that the
  ascertainment of a sensible parallax in any fixed star depends;
  and an error of one-thousandth of that amount (a quantity still
  unmeasurable by the most perfect of our instruments) would place
  the star too far or too near by 200,000,000,000 miles; a space
  which light requires 118 days to travel.


CAN STARS BE SEEN BY DAYLIGHT?

Aristotle maintains that Stars may occasionally be seen in the
Daylight, from caverns and cisterns, as through tubes. Pliny alludes
to the same circumstance, and mentions that stars have been most
distinctly recognised during solar eclipses. Sir John Herschel has
heard it stated by a celebrated optician, that his attention was first
drawn to astronomy by the regular appearance, at a certain hour, for
several successive days, of a considerable star through the shaft of
a chimney. The chimney-sweepers who have been questioned upon this
subject agree tolerably well in stating that “they have never seen
stars by day, but that when observed at night through deep shafts,
the sky appeared quite near, and the stars larger.” Saussure states
that stars have been seen with the naked eye in broad daylight, on
the declivity of Mont Blanc, at an elevation of 12,757 feet, as he
was assured by several of the alpine guides. The observer must be
placed entirely in the shade, and have a thick and massive shade above
his head, else the stronger light of the air will disperse the faint
image of the stars; these conditions resembling those presented by the
cisterns of the ancients, and the chimneys above referred to. Humboldt,
however, questions the accuracy of these evidences, adding that in the
Cordilleras of Mexico, Quito, and Peru, at elevations of 15,000 or
16,000 feet above the sea-level, he never could distinguish stars by
daylight. Yet, under the ethereally pure sky of Cumana, in the plains
near the sea-shore, Humboldt has frequently been able, after observing
an eclipse of Jupiter’s satellites, to find the planet again with the
naked eye, and has most distinctly seen it when the sun’s disc was from
18° to 20° above the horizon.


LOST HEAT OF THE SUN.

By the nature of our atmosphere, we are protected from the influence
of the full flood of solar heat. The absorption of caloric by the air
has been calculated at about one-fifth of the whole in passing through
a column of 6000 feet, estimated near the earth’s surface. And we are
enabled, knowing the increasing rarity of the upper regions of our
gaseous envelope, in which the absorption is constantly diminishing,
to prove that _about one-third of the solar heat is lost_ by vertical
transmission through the whole extent of our atmosphere.--_J. D.
Forbes, F.R.S._; _Bakerian Lecture_, 1842.


THE LONDON MONUMENT USED AS AN OBSERVATORY.

Soon after the completion of the Monument on Fish Street Hill, by Wren,
in 1677, it was used by Hooke and other members of the Royal Society
for astronomical purposes, but abandoned on account of the vibrations
being too great for the nicety required in their observations. Hence
arose _the report that the Monument was unsafe_, which has been revived
in our time; “but,” says Elmes, “its scientific construction may bid
defiance to the attacks of all but earthquakes for centuries to come.”
This vibration in lofty columns is not uncommon. Captain Smythe, in his
_Cycle of Celestial Objects_, tells us, that when taking observations
on the summit of Pompey’s Pillar, near Alexandria, the mercury was
sensibly affected by tremor, although the pillar is a solid.




Geology and Paleontology.


IDENTITY OF ASTRONOMY AND GEOLOGY.

While the Astronomer is studying the form and condition and structure
of the planets, in so far as the eye and the telescope can aid him, the
Geologist is investigating the form and condition and structure of the
planet to which he belongs; and it is from the analogy of the earth’s
structure, as thus ascertained, that the astronomer is enabled to form
any rational conjecture respecting the nature and constitution of the
other planetary bodies. Astronomy and Geology, therefore, constitute
the same science--the science of material or inorganic nature.

When the astronomer first surveys the _concavity_ of the celestial
vault, he finds it studded with luminous bodies differing in magnitude
and lustre, some moving to the east and others to the west; while by
far the greater number seem fixed in space; and it is the business of
astronomers to assign to each of them its proper place and sphere, to
determine their true distance from the earth, and to arrange them in
systems throughout the regions of sidereal space.

In like manner, when the geologist surveys the _convexity_ of his
own globe, he finds its solid covering composed of rocks and beds of
all shapes and kinds, lying at every possible angle, occupying every
possible position, and all of them, generally speaking, at the same
distance from the earth’s centre. Every where we see what was deep
brought into visible relation with what was superficial--what is old
with what is new--what preceded life with what followed it.

Thus displayed on the surface of his globe, it becomes the business
of the geologist to ascertain how these rocks came into their present
places, to determine their different ages, and to fix the positions
which they originally occupied, and consequently their different
distances from the centre or the circumference of the earth. Raised
from their original bed, the geologist must study the internal forces
by which they were upheaved, and the agencies by which they were
indurated; and when he finds that strata of every kind, from the
primitive granite to the recent tertiary marine mud, have been thus
brought within his reach, and prepared for his analysis, he reads their
respective ages in the organic remains which they entomb; he studies
the manner in which they have perished, and he counts the cycles of
time and of life which they disclose.--_Abridged from the North-British
Review_, No. 9.


THE GEOLOGY OF ENGLAND

is more interesting than that of other countries, because our island
is in a great measure an epitome of the globe; and the observer who is
familiar with our strata, and the fossil remains which they include,
has not only prepared himself for similar inquiries in other countries,
but is already, as it were, by anticipation, acquainted with what he is
to find there.--_Transactions of the Geological Society._


PROBABLE ORIGIN OF THE ENGLISH CHANNEL.

The proposed construction of a submarine tunnel across the Straits
of Dover has led M. Boué, For. Mem. Geol. Soc., to point out the
probability that the English Channel has not been excavated by
water-action only; but owes its origin to one of the lines of
disturbance which have fissured this portion of the earth’s crust:
and taking this view of the case, the fissure probably still exists,
being merely filled with comparatively loose material, so as to prove
a serious obstacle to any attempt made to drive through it a submarine
tunnel.--_Proceedings of the Geological Society._


HOW BOULDERS ARE TRANSPORTED TO GREAT HEIGHTS.

Sir Roderick Murchison has shown that in Russia, when the Dwina is at
its maximum height, and penetrates into the chinks of its limestone
banks, when frozen and expanded it causes disruptions of the rock,
the entanglement of stony fragments in the ice. In remarkable spring
floods, the stream so expands that in bursting it throws up its icy
fragments to 15 or 20 feet above the stream; and the waters subsiding,
these lateral ice-heaps melt away, and leave upon the bank the
rifled and angular blocks as evidence of the highest ice-mark. In
Lapland, M. Böhtlingk assures us that he has found _large granitic
boulders weighing several tons actually entangled and suspended, like
birds’-nests, in the branches of pine-trees, at heights of 30 or 40
feet above the summer level of the stream_![28]


WHY SEA-SHELLS ARE FOUND AT GREAT HEIGHTS.

The action of subterranean forces in breaking through and elevating
strata of sedimentary rocks,--of which the coast of Chili, in
consequence of a great earthquake, furnishes an example,--leads to the
assumption that the pelagic shells found by MM. Bonpland and Humboldt
on the ridge of the Andes, at an elevation of more than 15,000 English
feet, may have been conveyed to so extraordinary a position, not by a
rising of the ocean, but by the agency of volcanic forces capable of
elevating into ridges the softened crust of the earth.


SAND OF THE SEA AND DESERT.

That sand is an assemblage of small stones may be seen with the eye
unarmed with art; yet how few are equally aware of the synonymous
nature of the sand of the sea and of the land! Quartz, in the form of
sand, covers almost entirely the bottom of the sea. It is spread over
the banks of rivers, and forms vast plains, even at a very considerable
elevation above the level of the sea, as the desert of Sahara in
Africa, of Kobi in Asia, and many others. This quartz is produced, at
least in part, from the disintegration of the primitive granite rocks.
The currents of water carry it along, and when it is in very small,
light, and rounded grains, even the wind transports it from one place
to another. The hills are thus made to move like waves, and a deluge of
sand frequently inundates the neighbouring countries:

    “So where o’er wide Numidian wastes extend,
    Sudden the impetuous hurricanes descend.”--_Addison’s Cato._

To illustrate the trite axiom, that nothing is lost, let us glance at
the most important use of sand:

  “Quartz in the form of sand,” observes Maltebrun, “furnishes, by
  fusion, one of the most useful substances we have, namely glass,
  which, being less hard than the crystals of quartz, can be made
  equally transparent, and is equally serviceable to our wants and
  to our pleasures. There it shines in walls of crystal in the
  palaces of the great, reflecting the charms of a hundred assembled
  beauties; there, in the hand of the philosopher, it discovers to us
  the worlds that revolve above us in the immensity of space, and the
  no less astonishing wonders that we tread beneath our feet.”


PEBBLES.

The various heights and situations at which Pebbles are found have
led to many erroneous conclusions as to the period of changes of the
earth’s surface. All the banks of rivers and lakes, and the shores of
the sea, are covered with pebbles, rounded by the waves which have
rolled them against each other, and which frequently seem to have
brought them from a distance. There are also similar masses of pebbles
found at very great elevations, to which the sea appears never to
have been able to reach. We find them in the Alps at Valorsina, more
than 6000 feet above the level of the sea; and on the mountain of Bon
Homme, which is more than 1000 feet higher. There are some places
little elevated above the level of the sea, which, like the famous
plain of Crau, in Provence, are entirely paved with pebbles; while in
Norway, near Quedlia, some mountains of considerable magnitude seem to
be completely formed of them, and in such a manner that the largest
pebbles occupy the summit, and their thickness and size diminish as you
approach the base. We may include in the number of these confused and
irregular heaps most of the depositions of matter brought by the river
or sea, and left on the banks, and perhaps even those immense beds of
sand which cover the centre of Asia and Africa. It is this circumstance
which renders so uncertain the distinction, which it is nevertheless
necessary to establish, between alluvial masses created before the
commencement of history, and those which we see still forming under our
own eyes.

A charming monograph, entitled “Thoughts on a Pebble,” full of playful
sentiment and graceful fancy, has been written by the amiable Dr.
Mantell, the geologist.


ELEVATION OF MOUNTAIN-CHAINS.

Professor Ansted, in his _Ancient World_, thus characterises this
phenomenon:

  These movements, described in a few words, were doubtless going
  on for many thousands and tens of thousands of revolutions of our
  planet. They were accompanied also by vast but slow changes of
  other kinds. The expansive force employed in lifting up, by mighty
  movements, the northern portion of the continent of Asia, found
  partial vent; and from partial subaqueous fissures there were
  poured out the tabular masses of basalt occurring in Central India;
  while an extensive area of depression in the Indian Ocean, marked
  by the coral islands of the Laccadives, the Maldives, the great
  Chagos bank, and some others, were in the course of depression by a
  counteracting movement.

Hitherto the processes of denudation and of elevation have been so
far balanced as to preserve a pretty steady proportion of sea and dry
land during geological ages; but if the internal temperature should
be so far reduced as to be no longer capable of generating forces of
expansion sufficient for this elevatory action, while the denuding
forces should continue to act with unabated energy, the inevitable
result would be, that every mountain-top would be in time brought low.
No earthly barrier could declare to the ocean that there its proud
waves should be stayed. Nothing would stop its ravages till all dry
land should be laid prostrate, to form the bed over which it would
continue to roll an uninterrupted sea.


THE CHALK FORMATION.

Mr. Horner, F.R.S., among other things in his researches in the Delta,
considers it extremely probable that every particle of Chalk in the
world has at some period been circulating in the system of a living
animal.


WEAR OF BUILDING-STONES.

Professor Henry, in an account of testing the marbles used in building
the Capitol at Washington, states that every flash of lightning
produces an appreciable amount of nitric acid, which, diffused in
rain-water, acts on the carbonate of lime; and from specimens subjected
to actual freezing, it was found that in ten thousand years one inch
would be worn from the blocks by the action of frost.

  In 1839, a report of the examination of Sandstones, Limestones,
  and Oolites of Britain was made to the Government, with a view to
  the selection of the best material for building the new Houses
  of Parliament. For this purpose, 103 quarries were described, 96
  buildings in England referred to, many chemical analyses of the
  stones were given, and a great number of experiments related,
  showing, among other points, the cohesive power of each stone,
  and the amount of disintegration apparent, when subjected to
  Brard’s process. The magnesian limestone, or dolomite of Bolsover
  Moor, was recommended, and finally adopted for the Houses; but
  the selection does not appear to have been so successful as might
  have been expected from the skill and labour of the investigation.
  It may be interesting to add, that the publication of the above
  Report (for which see _Year-Book of Facts_, 1840, pp. 78-80)
  occasioned Mr. John Mallcott to remark in the _Times_ journal,
  “that all stone made use of in the immediate neighbourhood of its
  own quarries is more likely to endure that atmosphere than if it
  be removed therefrom, though only thirty or forty miles:” and the
  lapse of comparatively few years has proved the soundness of this
  observation.[29]


PHENOMENA OF GLACIERS ILLUSTRATED.

Professor Tyndall, being desirous of investigating some of the
phenomena presented by the large masses of mountain-ice,--those frozen
rivers called Glaciers,--devised the plan of sending a destructive
agent into the midst of a mass of ice, so as to break down its
structure in the interior, in order to see if this method would reveal
any thing of its internal constitution. Taking advantage of the bright
weather of 1857, he concentrated a beam of sunlight by a condensing
lens, so as to form the focus of the sun’s rays in the midst of a mass
of ice. A portion of the ice was melted, but the surrounding parts
shone out as brilliant stars, produced by the reflection of the faces
of the crystalline structure. On examining these brilliant portions
with a lens, Professor Tyndall discovered that the structure of the ice
had been broken down in symmetrical forms of great beauty, presenting
minute stars, surrounded by six petals, forming a beautiful flower, the
plane being always parallel to the plane of congelation of the ice.
He then prepared a piece of ice, by making both its surfaces smooth
and parallel to each other. He concentrated in the centre of the ice
the rays of heat from the electric light; and then, placing the piece
of ice in the electric microscope, the disc revealed these beautiful
ice-flowers.

A mass of ice was crushed into fragments; the small fragments were then
placed in a cup of wood; a hollow wooden die, somewhat smaller than the
cup, was then pressed into the cup of ice-fragments by the pressure of
a hydraulic press, and the ice-fragments were immediately united into
a compact cup of nearly transparent ice. This pressure of fragments
of ice into a solid mass explains the formation of the glaciers and
their origin. They are composed of particles of ice or snow; as they
descend the sides of the mountain, the pressure of the snow becomes
sufficiently great to compress the mass into solid ice, until it
becomes so great as to form the beautiful blue ice of the glaciers.
This compression, however, will not form the solid mass unless the
temperature of the ice be near that of freezing water. To prove this,
the lecturer cooled a mass of ice, by wrapping it in a piece of tinfoil
and exposing it for some time to a bath of the ethereal solution of
solidified carbonic-acid gas, the coldest freezing mixture known. This
cooled mass of ice was crushed to fragments, and submitted to the same
pressure which the other fragments had been exposed to without cohering
in the slightest degree.--_Lecture at the Royal Institution_, 1858.


ANTIQUITY OF GLACIERS.

The importance of glacier agency in the past as well as the present
condition of the earth, is undoubtedly very great. One of our most
accomplished and ingenious geologists has, indeed, carried back the
existence of Glaciers to an epoch of dim antiquity, even in the
reckoning of that science whose chronology is counted in millions of
years. Professor Ramsay has shown ground for believing that in the
fragments of rock that go to make up the conglomerates of the Permian
strata, intermediate between the Old and the New Red Sandstone, there
is still preserved a record of the action of ice, either in glaciers
or floating icebergs, before those strata were consolidated.--_Saturday
Review_, No. 142.


FLOW OF THE MER DE GLACE.

Michel Devouasson of Chamouni fell into a crevasse on the Glacier
of Talefre, a feeder of the Mer de Glace, on the 29th of July 1836,
and after a severe struggle extricated himself, leaving his knapsack
below. The identical knapsack reappeared in July 1846, at a spot on
the surface of the glacier _four thousand three hundred_ feet from
the place where it was lost, as ascertained by Professor Forbes, who
himself collected the fragments; thus indicating the rate of flow of
the icy river in the intervening ten years.--_Quarterly Review_, No.
202.


THE ALLUVIAL LAND OF EGYPT: ANCIENT POTTERY.

Mr. L. Horner, in his recent researches near Cairo, with the view of
throwing light upon the geological history of the alluvial land of
Egypt, obtained from the lowest part of the boring of the sediment at
the colossal statue of Rameses, at a depth of thirty-nine feet, this
curious relic of the ancient world; the boring instrument bringing up
a fragment of pottery about an inch square and a quarter of an inch in
thickness--the two surfaces being of a brick-red colour, the interior
dark gray. According to Mr. Horner’s deductions, this fragment, having
been found at a depth of 39 feet (if there be no fallacy in his
reasoning), must be held to be a record of the existence of man 13,375
years before A.D. 1858, reckoning by the calculated rate of increase of
three inches and a half of alluvium in a century--11,517 years before
the Christian era, and 7625 before the beginning assigned by Lepsius
to the reign of Menos, the founder of Memphis. Moreover it proves in
his opinion, that man had already reached a state of civilisation, so
far at least as to be able to fashion clay into vessels, and to know
how to harden it by the action of strong heat. This calculation is
supported by the Chevalier Bunsen, who is of opinion that the first
epochs of the history of the human race demand at the least a period
of 20,000 years before our era as a fair starting-point in the earth’s
history.--_Proceedings of Royal Soc._, 1858.

  Upon this theory, a Correspondent, “An Old Indigo-Planter,” writes
  to the _Athenæum_, No. 1509, the following suggestive note: “Having
  lived many years on the banks of the Ganges, I have seen the stream
  encroach on a village, undermining the bank where it stood, and
  deposit, as a natural result, bricks, pottery, &c. in the bottom
  of the stream. On one occasion, I am certain that the depth of
  the stream where the bank was breaking was above 40 feet; yet in
  three years the current of the river drifted so much, that a fresh
  deposit of soil took place over the _débris_ of the village, and
  the earth was raised to a level with the old bank. Now had our
  traveller then obtained a bit of pottery from where it had lain for
  only three years, could he reasonably draw the inference that it
  had been made 13,000 years before?”


SUCCESSIVE CHANGES OF THE TEMPLE OF SERAPIS.

The Temple of Serapis at Puzzuoli, near Naples, is perhaps, of all
the structures raised by the hands of man, the one which affords most
instruction to a geologist. It has not only undergone a wonderful
succession of changes in past time, but is still undergoing changes
of condition. This edifice was exhumed in 1750 from the eastern shore
of the Bay of Baiæ, consisting partly of strata containing marine
shells with fragments of pottery and sculpture, and partly of volcanic
matter of sub-aerial origin. Various theories were proposed in the
last century to explain the perforations and attached animals observed
on the middle zone of the three erect marble columns until recently
standing; Goethe, among the rest, suggesting that a lagoon had once
existed in the vestibule of the temple, filled during a temporary
incursion of the sea with salt water, and that marine mollusca and
annelids flourished for years in this lagoon at twelve feet or more
above the sea-level.

This hypothesis was advanced at a time when almost any amount of
fluctuation in the level of the sea was thought more probable than
the slightest alteration in the level of the solid land. In 1807 the
architect Niccolini observed that the pavement of the temple was dry,
except when a violent south wind was blowing; whereas, on revisiting
the temple fifteen years later, he found the pavement covered by salt
water twice every day at high tide. From measurements made from 1822
to 1838, and thence to 1845, he inferred that the sea was gaining
annually upon the floor of the temple at the rate of about one-third
of an inch during the first period, and about three-fourths of an inch
during the second. Mr. Smith of Jordan Hill, from his visits in 1819
and 1845, found an average rise of about an inch annually, which was
in accordance with visits made by Mr. Babbage in 1828, and Professor
James Forbes in 1826 and 1843. In 1852 Signor Scaecchi, at the request
of Sir Charles Lyell, compared the depth of water on the pavement with
its level taken by him in 1839, and found that it had gained only 4½
inches in thirteen years, and was not so deep as when MM. Niccolini
and Smith measured it in 1845; from which he inferred that after 1845
the downward movement of the land had ceased, and before 1852 had been
converted into an upward movement.

Arago and others maintained that the surface on which the temple
stands has been depressed, has _remained under the sea, and has again
been elevated_. Russager, however, contends that there is nothing in
the vicinity of the temple, or in the temple itself, to justify this
bold hypothesis. Every thing leads to the belief that the temple has
remained unchanged in the position in which it was originally built;
but that the sea rose, surrounded it to a height of at least twelve
feet, and again retired; but the elevated position of the sea continued
sufficiently long to admit of the animals boring the pillars. This view
can even be proved historically; for Niccolini, in a memoir published
in 1840, gives the heights of the level of the sea in the Bay of
Naples for a period of 1900 years, and has with much acuteness proved
his assertions historically. The correctness of Russager’s opinion,
he states, can be demonstrated and reduced to figures by means of the
dates collected by Niccolini.--See _Jameson’s Journal_, No. 58.

At the present time the floor is always covered with sea-water. On the
whole, there is little doubt that the ground has sunk upwards of two
feet during the last half-century. This gradual subsidence confirms
in a remarkable manner Mr. Babbage’s conclusions--drawn from the
calcareous incrustations formed by the hot springs on the walls of the
building and from the ancient lines of the water-level at the base of
the three columns--that the original subsidence was not sudden, but
slow and by successive movements.

Sir Charles Lyell (who, in his _Principles of Geology_, has given a
detailed account of the several upfillings of the temple) considers
that when the mosaic pavement was re-constructed, the floor of the
building must have stood about twelve feet above the level of 1838 (or
about 11½ feet above the level of the sea), and that it had sunk about
nineteen feet below that level before it was elevated by the eruption
of Monte Nuovo.

We regret to add, that the columns of the temple are no longer in
the position in which they served so many years as a species of
self-registering hydrometer: the materials have been newly arranged,
and thus has been torn as it were from history a page which can never
be replaced.


THE GROTTO DEL CANE.

This “Dog Grotto” has been so much cited for its stratum of
carbonic-acid gas covering the floor, that all geological travellers
who visit Naples feel an interest in seeing the wonder.

This cavern was known to Pliny. It is continually exhaling from its
sides and floor volumes of steam mixed with carbonic-acid gas; but the
latter, from its greater specific gravity, accumulates at the bottom,
and flows over the step of the door. The upper part of the cave,
therefore, is free from the gas, while the floor is completely covered
by it. Addison, on his visit, made some interesting experiments. He
found that a pistol could not be fired at the bottom; and that on
laying a train of gunpowder and igniting it on the outside of the
cavern, the carbonic-acid gas “could not intercept the train of fire
when it once began flashing, nor hinder it from running to the very
end.” He found that a viper was nine minutes in dying on the first
trial, and ten minutes on the second; this increased vitality being,
in his opinion, attributable to the stock of air which it had inhaled
after the first trial. Dr. Daubeny found that phosphorus would continue
lighted at about two feet above the bottom; that a sulphur-match went
out in a few minutes above it, and a wax-taper at a still higher level.
The keeper of the cavern has a dog, upon which he shows the effects of
the gas, which, however, are quite as well, if not better, seen in a
torch, a lighted candle, or a pistol.

“Unfortunately,” says Professor Silliman, “like some other grottoes,
the enchantment of the ‘Dog Grotto’ disappears on a near view.” It is a
little hole dug artificially in the side of a hill facing Lake Agnano:
it is scarcely high enough for a person to stand upright in, and the
aperture is closed by a door. Into this narrow cell a poor little dog
is very unwillingly dragged and placed in a depression of the floor,
where he is soon narcotised by the carbonic acid. The earth is warm to
the hand, and the gas given out is very constant.


THE WATERS OF THE GLOBE GRADUALLY DECREASING.

This was maintained by M. Bory Saint Vincent, because the vast deserts
of sand, mixed up with the salt and remains of marine animals, of which
the surface of the globe is partly composed, were formerly inland seas,
which have insensibly become dry. The Caspian, the Dead Sea, the Lake
Baikal, &c. will become dry in their turn also, when their beds will
be sandy deserts. The inland seas, whether they have only one outlet,
as the Mediterranean, the Red Sea, the Baltic, &c., or whether they
have several, as the Gulf of Mexico, the seas of O’Kotsk, of Japan,
China, &c., will at some future time cease to communicate with the
great basins of the ocean; they will become inland seas, true Caspians,
and in due time will become likewise dry. On all sides the waters
of rivers are seen to carry forward in their course the soil of the
continent. Alluvial lands, deltas, banks of sand, form themselves near
the coasts, and in the directions of the currents; madreporic animals
lay the foundations of new lands; and while the straits become closed,
while the depths of the sea fill up, the level of the sea, which it
would seem natural should become higher, is sensibly lower. There is,
therefore, an actual diminution of liquid matter.


THE SALT LAKE OF UTAH.

Lieutenant Gunnison, who has surveyed the great basin of the Salt
Lake, states the water to be about one-third salt, which it yields
on boiling. Its density is considerably greater than that of the Red
Sea. One can hardly get the whole body below the surface: in a sitting
position the head and shoulders will remain above the water, such is
the strength of the brine; and on coming to the shore the body is
covered with an incrustation of salt in fine crystals. During summer
the lake throws on shore abundance of salt, while in winter it throws
up Glauber salt plentifully. “The reason of this,” says Lieutenant
Gunnison, “is left for the scientific to judge, and also what becomes
of the enormous amount of fresh water poured into it by three or four
large rivers,--Jordan, Bear, and Weber,--as there is no visible effect.”


FORCE OF RUNNING WATER.

It has been proved by experiment that the rapidity at the bottom
of a stream is every where less than in any other part of it, and
is greatest at the surface. Also, that in the middle of the stream
the particles at the top move swifter than those at the sides. This
slowness of the lowest and side currents is produced by friction; and
when the rapidity is sufficiently great, the soil composing the sides
and bottom gives way. If the water flows at the rate of three inches
per second, it will tear up fine clay; six inches per second, fine
sand; twelve inches per second, fine gravel; and three feet per second,
stones the size of an egg.--_Sir Charles Lyell._


THE ARTESIAN WELL OF GRENELLE AT PARIS.

M. Peligot has ascertained that the Water of the Artesian Well of
Grenelle contains not the least trace of air. Subterranean waters ought
therefore to be _aerated_ before being used as aliment. Accordingly, at
Grenelle, has been constructed a tower, from the top of which the water
descends in innumerable threads, so as to present as much surface as
possible to the air.

The boring of this Well by the Messrs. Mulot occupied seven years, one
month, twenty-six days, to the depth of 1794½ English feet, or 194½
feet below the depth at which M. Elie de Beaumont foretold that water
would be found. The sound, or borer, weighed 20,000 lb., and was treble
the height of that of the dome of the Hôpital des Invalides at Paris.
In May 1837, when the bore had reached 1246 feet 8 inches, the great
chisel and 262 feet of rods fell to the bottom; and although these
weighed five tons, M. Mulot tapped a screw on the head of the rods, and
thus, connecting another length to them, after fifteen months’ labour,
drew up the chisel. On another occasion, this chisel having been raised
with great force, sank at one stroke 85 feet 3 inches into the chalk!

  The depth of the Grenelle Well is nearly four times the height of
  Strasburg Cathedral; more than six times the height of the Hôpital
  des Invalides at Paris; more than four times the height of St.
  Peter’s at Rome; nearly four times and a half the height of St.
  Paul’s, and nine times the height of the Monument, London. Lastly,
  suppose all the above edifices to be piled one upon each other,
  from the base-line of the Well of Grenelle, and they would but
  reach within 11½ feet of its surface.

  MM. Elie de Beaumont and Arago never for a moment doubted the final
  success of the work; their confidence being based on analogy, and
  on a complete acquaintance with the geological structure of the
  Paris basin, which is identical with that of the London basin
  beneath the London clay.

  In the duchy of Luxembourg is a well the depth of which surpasses
  all others of the kind. It is upwards of 1000 feet more than that
  of Grenelle near Paris.


HOW THE GULF-STREAM REGULATES THE TEMPERATURE OF LONDON.

Great Britain is almost exactly under the same latitude as Labrador, a
region of ice and snow. Apparently, the chief cause of the remarkable
difference between the two climates arises from the action of the great
oceanic Gulf-Stream, whereby this country is kept constantly encircled
with waters warmed by a West-Indian sun.

  Were it not for this unceasing current from tropical seas, London,
  instead of its present moderate average winter temperature of
  6° above the freezing-point, might for many months annually be
  ice-bound by a settled cold of 10° to 30° below that point, and
  have its pleasant summer months replaced by a season so short
  as not to allow corn to ripen, or only an alpine vegetation to
  flourish.

  Nor are we without evidence afforded by animal life of a greater
  cold having prevailed in this country at a late geological period.
  One case in particular occurs within eighty miles of London, at the
  village of Chillesford, near Woodbridge, where, in a bed of clayey
  sand of an age but little (geologically speaking) anterior to the
  London gravel, Mr. Prestwich has found a group of fossil shells
  in greater part identical with species now living in the seas of
  Greenland and of similar latitudes, and which must evidently, from
  their perfect condition and natural position, have existed in the
  place where they are now met with.--_Lectures on the Geology of
  Clapham, &c. by Joseph Prestwich, A.R.S., F.G.S._


SOLVENT ACTION OF COMMON SALT AT HIGH TEMPERATURES.

Forchhammer, after a long series of experiments, has come to the
conclusion that Common Salt at high temperatures, such as prevailed at
earlier periods of the earth’s history, acted as a general solvent,
similarly to water at common temperatures. The amount of common salt
in the earth would suffice to cover its whole surface with a crust ten
feet in thickness.


FREEZING CAVERN IN RUSSIA.

This famous Cavern, at Ithetz Kaya-Zastchita, in the Steppes of the
Kirghis, is employed by the inhabitants as a cellar. It has the very
remarkable property of being so intensely cold during the hottest
summers as to be then filled with ice, which disappearing with cold
weather, is entirely gone in winter, when all the country is clad
in snow. The roof is hung with ever-dripping solid icicles, and the
floor may be called a stalagmite of ice and frozen earth. “If,” says
Sir R. Murchison, “as we were assured, _the cold is greatest when the
external air is hottest and driest_, that the fall of rain and a moist
atmosphere produce some diminution of the cold in the cave, and that
upon the setting-in of winter the ice disappears entirely,--then indeed
the problem is very curious.” The peasants assert that in winter they
could sleep in the cave without their sheepskins.


INTERIOR TEMPERATURE OF THE EARTH: CENTRAL HEAT.

By the observed temperature of mines, and that at the bottom of
artesian wells, it has been established that the rate at which such
temperature increases as we descend varies considerably in different
localities, where the depths are comparatively small; but where the
depths are great, we find a much nearer approximation to a common
rate of increase, which, as determined by the best observation in the
deepest mines, shafts, and artesian wells in Western Europe, is very
nearly 1° F. _for an increase in depth of fifty feet_.--_W. Hopkins,
M.A., F.R.S._

Humboldt states that, according to tolerably coincident experiments in
artesian wells, it has been shown that the heat increases on an average
about 1° for every 54·5 feet. If this increase can be reduced to
arithmetical relations, it will follow that a stratum of granite would
be in a state of fusion at a depth of nearly twenty-one geographical
miles, or between four and five times the elevation of the highest
summit of the Himalaya.

The following is the opinion of Professor Silliman:

  That the whole interior portion of the earth, or at least a great
  part of it, is an ocean of melted rock, agitated by violent winds,
  though I dare not affirm it, is still rendered highly probable by
  the phenomena of volcanoes. The facts connected with their eruption
  have been ascertained and placed beyond a doubt. How, then, are
  they to be accounted for? The theory prevalent some years since,
  that they are caused by the combustion of immense coal-beds, is
  puerile and now entirely abandoned. All the coal in the world could
  not afford fuel enough for one of the tremendous eruptions of
  Vesuvius.

This observed increase of temperature in descending beneath the earth’s
surface suggested the notion of a central incandescent nucleus still
remaining in a state of fluidity from its elevated temperature. Hence
the theory that the whole mass of the earth was formerly a molten
fluid mass, the exterior portion of which, to some unknown depth, has
assumed its present solidity by the radiation of heat into surrounding
space, and its consequent refrigeration.

The mathematical solution of this problem of Central Heat, assuming
such heat to exist, tells us that though the central portion of the
earth may consist of a mass of molten matter, the temperature of its
surface is not thereby increased by more than the small fraction of
a degree. Poisson has calculated that it would require _a thousand
millions of centuries_ to reduce this fraction to a degree by half its
present amount, supposing always the external conditions to remain
unaltered. In such cases, the superficial temperature of the earth may,
in fact, be considered to have approximated so near to its ultimate
limit that it can be subject to no further sensible change.


DISAPPEARANCE OF VOLCANIC ISLANDS.

Many of the Volcanic Islands thrown up above the sea-level soon
disappear, because the lavas and conglomerates of which they are formed
spread over flatter surfaces, through the weight of the incumbent
fluid; and the constant levelling process goes on below the sea by the
action of tides and currents. Such islands as have effectually resisted
this action are found to possess a solid framework of lava, supporting
or defending the loose fragmentary materials.

  Among the most celebrated of these phenomena in our times may be
  mentioned the Isle of Sabrina, which rose off the coast of St.
  Michael’s in 1811, attained a circumference of one mile and a
  height of 300 feet, and disappeared in less than eight months; in
  the following year there were eighty fathoms of water in its place.
  In July 1831 appeared Graham’s Island off the coast of Sicily,
  which attained a mile in circumference and 150 or 160 feet in
  height; its formation much resembled that of Sabrina.

The line of ancient subterranean fire which we trace on the
Mediterranean coasts has had a strange attestation in Graham’s Island,
which is also described as a volcano suddenly bursting forth in the mid
sea between Sicily and Africa; burning for several weeks, and throwing
up an isle, or crater-cone of scoriæ and ashes, which had scarcely been
named before it was again lost by subsidence beneath the sea, leaving
only a shoal-bank to attest this strange submarine breach in the
earth’s crust, which thus mingled fire and water in one common action.

Floating islands are not very rare: in 1827, one was seen twenty
leagues to the east of the Azores; it was three leagues in width, and
covered with volcanic products, sugar-canes, straw, and pieces of wood.


PERPETUAL FIRE.

Not far from the Deliktash, on the side of a mountain in Lycia, is the
Perpetual Fire described some forty years since by Captain Beaufort.
It was found by Lieutenant Spratt and Professor Forbes, thirty years
later, as brilliant as ever, and somewhat increased; for besides the
large flame in the corner of the ruins described by Beaufort, there
were small jets issuing from crevices in the side of the crater-like
cavity five or six feet deep. At the bottom was a shallow pool of
sulphureous and turbid water, regarded by the Turks as a sovereign
remedy for all skin complaints. The soot deposited from the flames was
held to be efficacious for sore eyelids, and valued as a dye for the
eyebrows. This phenomenon is described by Pliny as the flame of the
Lycian Chimera.


ARTESIAN FIRE-SPRINGS IN CHINA.

According to the statement of the missionary Imbert, the
Fire-Springs, “Ho-tsing” of the Chinese, which are sunk to obtain a
carburetted-hydrogen gas for salt-boiling, far exceed our artesian
springs in depth. These springs are very commonly more than 2000 feet
deep; and a spring of continued flow was found to be 3197 feet deep.
This natural gas has been used in the Chinese province Tse-tschuan for
several thousand years; and “portable gas” (in bamboo-canes) has for
ages been used in the city of Khiung-tscheu. More recently, in the
village of Fredonia, in the United States, such gas has been used both
for cooking and for illumination.


VOLCANIC ACTION THE GREAT AGENT OF GEOLOGICAL CHANGE.

  Mr. James Nasmyth observes, that “the floods of molten lava which
  volcanoes eject are nothing less than remaining portions of what
  was once the condition of the entire globe when in the igneous
  state of its early physical history,--no one knows how many years
  ago!

  “When we behold the glow and feel the heat of molten lava, how
  vastly does it add to the interest of the sight when we consider
  that the heat we feel and the light we see are the residue of the
  once universal condition of our entire globe, on whose _cooled
  surface_ we _now_ live and have our being! But so it is; for if
  there be one great fact which geological research has established
  beyond all doubt, it is that we reside on the cooled surface of
  what was once a molten globe, and that all the phenomena which
  geology has brought to light can be most satisfactorily traced
  to the successive changes incidental to its gradual cooling and
  contraction.

  “That the influx of the sea into the yet hot and molten interior of
  the globe may occasionally occur, and enhance and vary the violence
  of the phenomenon of volcanic action, there can be little doubt;
  but the action of water in such cases is only _secondary_. But for
  the pre-existing high temperature of the interior of the earth, the
  influx of water would produce no such discharges of molten lava as
  generally characterise volcanic eruptions. Molten lava is therefore
  a true vestige of the Natural History of the Creation.”


THE SNOW-CAPPED VOLCANO.

It is but rarely that the elastic forces at work within the interior of
our globe have succeeded in breaking through the spiral domes which,
resplendent in the brightness of eternal snow, crown the summits of the
Cordilleras; and even where these subterranean forces have opened a
permanent communication with the atmosphere, through circular craters
or long fissures, they rarely send forth currents of lava, but merely
eject ignited scoriæ, steam, sulphuretted hydrogen gas, and jets of
carbonic acid.--_Humboldt’s Cosmos_, vol. i.


TRAVELS OF VOLCANIC DUST.

On the 2d of September 1845, a quantity of Volcanic Dust fell in the
Orkney Islands, which was supposed to have originated in an eruption of
Hecla, in Iceland. It was subsequently ascertained that an eruption of
that volcano took place on the morning of the above day (September 2),
so as to leave no doubt of the accuracy of the conclusion. The dust had
thus travelled about 600 miles!


GREAT ERUPTIONS OF VESUVIUS.

In the great eruption of Vesuvius, in August 1779, which Sir William
Hamilton witnessed from his villa at Pausilippo in the bay of Naples,
the volcano sent up white sulphureous smoke resembling bales of cotton,
exceeding the height and size of the mountain itself at least four
times; and in the midst of this vast pile of smoke, stones, scoriæ,
and ashes were thrown up not less than 2000 feet. Next day a fountain
of fire shot up with such height and brilliancy that the smallest
objects could be clearly distinguished at any place within six miles
or more of Vesuvius. But on the following day a more stupendous column
of fire rose three times the height of Vesuvius (3700 feet), or more
than two miles high. Among the huge fragments of lava thrown out during
this eruption was a block 108 feet in circumference and 17 feet high,
another block 66 feet in circumference and 19 feet high, and another 16
feet high and 92 feet in circumference, besides thousands of smaller
fragments. Sir William Hamilton suggests that from a scene of the above
kind the ancient poets took their ideas of the giants waging war with
Jupiter.

The eruption of June 1794, which destroyed the greater part of the
town of Torre del Greco, was, however, the most violent that has been
recorded after the two great eruptions of 79 and 1631.


EARTH-WAVES.

The waves of an earthquake have been represented in their progress,
and their propagation, through rocks of different density and
elasticity; and the causes of the rapidity of propagation, and its
diminution by the refraction, reflection, and interference of the
oscillations have been mathematically investigated. Air, water, and
earth waves follow the same laws which are recognised by the theory of
motion, at all events in space; but the earth-waves are accompanied
in their destructive action by discharges of elastic vapours, and
of gases, and mixtures of pyroxene crystals, carbon, and infusorial
animalcules with silicious shields. The more terrific effects are,
however, when the earth-waves are accompanied by cleavage; and, as in
the earthquake of Riobamba, when fissures alternately opened and closed
again, so that men saved themselves by extending both arms, in order to
prevent their sinking.

As a remarkable example of the closing of a fissure, Humboldt mentions
that, during the celebrated earthquake in 1851, in the Neapolitan
province of Basilicata, a hen was found caught by both feet in the
street-pavement of Barile, near Melfi.

Mr. Hopkins has very correctly shown theoretically that the fissures
produced by earthquakes are very instructive as regards the formation
of veins and the phenomenon of dislocation, the more recent vein
displacing the older formation.


RUMBLINGS OF EARTHQUAKES.

When the great earthquake of Coseguina, in Nicaragua, took place,
January 23, 1835, the subterranean noise--the sonorous waves in the
earth--was heard at the same time on the island of Jamaica and on the
plateau of Bogota, 8740 feet above the sea, at a greater distance than
from Algiers to London. In the eruptions of the volcano on the island
of St. Vincent, April 30, 1812, at 2 A.M., a noise like the report of
cannons was heard, without any sensible concussion of the earth, over a
space of 160,000 geographical square miles. There have also been heard
subterranean thunderings for two years without earthquakes.


HOW TO MEASURE AN EARTHQUAKE-SHOCK.

A new instrument (the Seismometer) invented for this purpose by
M. Kreil, of Vienna, consists of a pendulum oscillating in every
direction, but unable to turn round on its point of suspension; and
bearing at its extremity a cylinder, which, by means of mechanism
within it, turns on its vertical axis once in twenty-four hours. Next
to the pendulum stands a rod bearing a narrow elastic arm, which
slightly presses the extremity of a lead-pencil against the surface
of the cylinder. As long as the pendulum is quiet, the pencil traces
an uninterrupted line on the surface of the cylinder; but as soon as
it oscillates, this line becomes interrupted and irregular, and these
irregularities indicate the time of the commencement of an earthquake,
together with its duration and intensity.[30]

Elastic fluids are doubtless the cause of the slight and perfectly
harmless trembling of the earth’s surface, which has often continued
for several days. The focus of this destructive agent, the seat of
the moving force, lies far below the earth’s surface; but we know as
little of the extent of this depth as we know of the chemical nature
of these vapours that are so highly compressed. At the edges of two
craters,--Vesuvius and the towering rock which projects beyond the
great abyss of Pichincha, near Quito,--Humboldt has felt periodic
and very regular shocks of earthquakes, on each occasion from twenty
to thirty seconds before the burning scoriæ or gases were erupted.
The intensity of the shocks was increased in proportion to the time
intervening between them, and consequently to the length of time in
which the vapours were accumulating. This simple fact, which has
been attested by the evidence of so many travellers, furnishes us
with a general solution of the phenomenon, in showing that active
volcanoes are to be considered as safety-valves for the immediate
neighbourhood. There are instances in which the earth has been shaken
for many successive days in the chain of the Andes, in South America.
In certain districts, the inhabitants take no more notice of the number
of earthquakes than we in Europe take of showers of rain; yet in such
a district Bonpland and Humboldt were compelled to dismount, from the
restiveness of their mules, because the earth shook in a forest for
fifteen to eighteen minutes _without intermission_.


EARTHQUAKES AND THE MOON.

From a careful discussion of several thousand earthquakes which have
been recorded between 1801 and 1850, and a comparison of the periods at
which they occurred with the position of the moon in relation to the
earth, M. Perry, of Dijon, infers that earthquakes may possibly be the
result of attraction exerted by that body on the supposed fluid centre
of our globe, somewhat similar to that which she exercises on the
waters of the ocean; and the Committee of the Institute of France have
reported favourably upon this theory.


THE GREAT EARTHQUAKE OF LISBON.

The eloquent Humboldt remarks, that the activity of an igneous
mountain, however terrific and picturesque the spectacle may be which
it presents to our contemplation, is always limited to a very small
space. It is far otherwise with earthquakes, which, although scarcely
perceptible to the eye, nevertheless simultaneously propagate their
waves to a distance of many thousand miles. The great earthquake which
destroyed the city of Lisbon, November 1st, 1755, was felt in the
Alps, on the coast of Sweden, into the Antilles, Antigua, Barbadoes,
and Martinique; in the great Canadian lakes, in Thuringia, in the
flat country of northern Germany, and in the small inland lakes on
the shores of the Baltic. Remote springs were interrupted in their
flow,--a phenomenon attending earthquakes which had been noticed among
the ancients by Demetrius the Callatian. The hot springs of Töplitz
dried up and returned, inundating every thing around, and having their
waters coloured with iron ochre. At Cadiz, the sea rose to an elevation
of sixty-four feet; while in the Antilles, where the tide usually
rises only from twenty-six to twenty-eight inches, it suddenly rose
about twenty feet, the water being of an inky blackness. It has been
computed that, on November 1st, 1755, a portion of the earth’s surface
four times greater than that of Europe was simultaneously shaken.[31]
As yet there is no manifestation of force known to us (says the
vivid denunciation of the philosopher), including even the murderous
invention of our own race, by which a greater number of people have
been killed in the short space of a few minutes: 60,000 were destroyed
in Sicily in 1693, from 30,000 to 40,000 in the earthquake of Riobamba
in 1797, and probably five times as many in Asia Minor and Syria under
Tiberius and Justinian the elder, about the years 19 and 526.


GEOLOGICAL AGE OF THE DIAMOND.

The discovery of Diamonds in Russia, far from the tropical zone, has
excited much interest among geologists. In the detritus on the banks
of the Adolfskoi, no fewer than forty diamonds have been found in the
gold alluvium, only twenty feet above the stratum in which the remains
of mammoths and rhinoceroses are found. Hence Humboldt has concluded
that the formation of gold-veins, and consequently of diamonds, is
comparatively of recent date, and scarcely anterior to the destruction
of the mammoths. Sir Roderick Murchison and M. Verneuil have been led
to the same result by different arguments.[32]


WHAT WAS ADAMANT?

Professor Tennant replies, that the Adamant described by Pliny was a
sapphire, as proved by its form, and by the fact that when struck on
an anvil by a hammer it would make an indentation in the metal. A true
diamond, under such circumstances, would fly into a thousand pieces.


WHAT IS COAL?

The whole evidence we possess as to the nature of Coal proves it to
have been originally a mass of vegetable matter. Its microscopical
characters point to its having been formed on the spot in which we
find it, to its being composed of vegetable tissues of various kinds,
separated and changed by maceration, pressure, and chemical action,
and to the introduction of its earthy matter, in a large number of
instances, in a state of solution or fine molecular subdivision. Dr.
Redfern, from whose communication to the British Association we quote,
knows nothing to countenance the supposition that our coal-beds are
mainly formed of coniferous wood, because the structures found in
mother-coal, or the charcoal layer, have not the character of the
glandular tissue of such wood, as has been asserted.

Geological research has shown that the immense forests from which our
coal is formed teemed with life. A frog as large as an ox existed in
the swamps, and the existence of insects proves that the higher order
of organic creation flourished at this epoch.

It has been calculated that the available coal-beds in Lancashire
amount in weight to the enormous sum of 8,400,000,000 tons. The total
annual consumption of this coal, it has been estimated, amounts to
3,400,120 tons; hence it is inferred that the coal-beds of Lancashire,
at the present rate of consumption, will last 2470 years. Making
similar calculations for the coal-fields of South Wales, the north of
England, and Scotland, it will readily be perceived how ridiculous were
the forebodings which lecturing geologists delighted to indulge in a
few years ago.


TORBANE-HILL COAL.

The coal of Torbane Hill, Scotland, is so highly inflammable, that it
has been disputed at law whether it be true coal, or only asphaltum,
or bitumen. Dr. Redfern describes it as laminated, splitting with
great ease horizontally, like many cannel coals, and like them it may
be lighted at a candle. In all parts of the bed stigmaria and other
fossil plants occur in greater numbers than in most other coals; their
distinct vascular tissue may be easily recognised by a common pocket
lens, and 65½ of the mass consists of carbon.

Dr. Redfern considers that all our coals may be arranged in a scale
having the Torbane-Hill coal at the top and anthracite at the bottom.
Anthracite is almost pure carbon; Torbane Hill contains less fixed
carbon than most other cannels: anthracite is very difficult to ignite,
and gives out scarcely any gas; Torbane-Hill burns like a candle, and
yields 3000 cubic feet of gas per ton, more than any other known coal,
its gas being also of greatly superior illuminating power to any other.
The only differences which the Torbane-Hill coal presents from others
are differences of degree, not of kind. It differs from other coals
in being the best gas-coal, and from other cannels in being the best
cannel.


HOW MALACHITE IS FORMED.

The rich copper-ore of the Ural, which occurs in veins or masses,
amid metamorphic strata associated with igneous rocks, and even in
the hollows between the eruptive rocks, is worked in shafts. At the
bottom of one of these, 280 feet deep, has been found an enormous
irregularly-shaped botryoidal mass of _Malachite_ (Greek _malache_,
mountain-green), sending off strings of green copper-ore. The upper
surface of it is about 18 feet long and 9 wide; and it was estimated
to contain 15,000 poods, or half a million pounds, of pure and compact
malachite. Sir Roderick Murchison is of opinion that this wonderful
subterraneous incrustation has been produced in the stalagmitic form,
during a series of ages, by copper solutions emanating from the
surrounding loose and sporous mass, and trickling through it to the
lowest cavity upon the subjacent solid rock. Malachite is brought
chiefly from one mine in Siberia; its value as raw material is nearly
one-fourth that of the same weight of pure silver, or in a manufactured
state three guineas per pound avoirdupois.[33]


LUMPS OF GOLD IN SIBERIA.

The gold mines south of Miask are chiefly remarkable for the large
lumps or _pepites_ of gold which are found around the Zavod of
Zarevo-Alexandroisk. Previous to 1841 were discovered here lumps of
native gold; in that year a lump of twenty-four pounds was met with;
and in 1843 a lump weighing about seventy-eight pounds English was
found, and is now deposited with others in the Museum of the Imperial
School of Mines at St. Petersburg.


SIR ISAAC NEWTON UPON BURNET’S THEORY OF THE EARTH.

In 1668, Dr. Thomas Burnet printed his _Theoria Telluris Sacra_,
“an eloquent physico-theological romance,” says Sir David Brewster,
“which was to a certain extent adopted even by Newton, Burnet’s
friend. Abandoning, as some of the fathers had done, the hexaëmeron,
or six days of Moses, as a physical reality, and having no knowledge
of geological phenomena, he gives loose reins to his imagination,
combining passages of Scripture with those of ancient authors, and
presumptuously describing the future catastrophes to which the earth is
to be exposed.” Previous to its publication, Burnet presented a copy
of his book to Newton, and requested his opinion of the theory which
it propounded. Newton took “exceptions to particular passages,” and
a correspondence ensued. In one of Newton’s letters he treats of the
formation of the earth, and the other planets, out of a general chaos
of the figure assumed by the earth,--of the length of the primitive
days,--of the formation of hills and seas, and of the creation of the
two ruling lights as the result of the clearing up of the atmosphere.
He considers the account of the creation in Genesis as adapted to the
judgment of the vulgar. “Had Moses,” he says, “described the processes
of creation as distinctly as they were in themselves, he would have
made the narrative tedious and confused amongst the vulgar, and become
a philosopher more than a prophet.” After referring to several “causes
of meteors, such as the breaking out of vapours from below, before
the earth was well hardened, the settling and shrinking of the whole
globe after the upper regions or surface began to be hard,” Newton
closes his letter with an apology for being tedious, which, he says,
“he has the more reason to do, as he has not set down any thing he has
well considered, or will undertake to defend.”--See the Letter in the
Appendix to _Sir D. Brewster’s Life of Newton_, vol. ii.

  The primitive condition of the earth, and its preparation for
  man, was a subject of general speculation at the close of the
  seventeenth century. Leibnitz, like his great rival (Newton),
  attempted to explain the formation of the earth, and of the
  different substances which composed it; and he had the advantage
  of possessing some knowledge of geological phenomena: the earth
  he regarded as having been originally a burning mass, whose
  temperature gradually diminished till the vapours were condensed
  into a universal ocean, which covered the highest mountains, and
  gradually flowed into vacuities and subterranean cavities produced
  by the consolidation of the earth’s crust. He regarded fossils
  as the real remains of plants and animals which had been buried
  in the strata; and, in speculating on the formation of mineral
  substances, he speaks of crystals as the geometry of inanimate
  nature.--_Brewster’s Life of Newton_, vol. ii. p. 100, note. (See
  also “The Age of the Globe,” in _Things not generally Known_, p.
  13.)


“THE FATHER OF ENGLISH GEOLOGY.”

In 1769 was born, the son of a yeoman of Oxfordshire, William
Smith. When a boy he delighted to wander in the fields, collecting
“pound-stones” (_Echinites_), “pundibs” (_Terebratulæ_), and other
stony curiosities; and receiving little education beyond what he taught
himself, he learned nothing of classics but the name. Grown to be a
man, he became a land-surveyor and civil engineer, and was much engaged
in constructing canals. While thus occupied, he observed that all the
rocky masses forming the substrata of the country were gently inclined
to the east and south-east,--that the red sandstones and marls above
the _coal-measures_ passed below the beds provincially termed lias-clay
and limestone--that these again passed underneath the sands, yellow
limestone, and clays that form the table-land of the Coteswold Hills;
while they in turn plunged beneath the great escarpment of chalk that
runs from the coast of Dorsetshire northward to the Yorkshire shores
of the German Ocean. He further observed that each formation of clay,
sand, or limestone, held to a very great extent its own peculiar suite
of fossils. The “snake-stones” (_Ammonites_) of the lias were different
in form and ornament from those of the inferior oolite; and the
shells of the latter, again, differed from those of the Oxford clay,
Cornbrash, and Kimmeridge clay. Pondering much on these things, he
came to the then unheard-of conclusion that each formation had been in
its turn a sea-bottom, in the sediments of which lived and died marine
animals now extinct, many specially distinctive of their own epochs in
time.

Here indeed was a discovery,--made, too, by a man utterly unknown to
the scientific world, and having no pretension to scientific lore.
“Strata Smith’s” find was unheeded for many a long year; but at length
the first geologists of the day learned from the land-surveyor that
superposition of strata is inseparably connected with the succession
of life in time. Hooke’s grand vision was at length realised, and it
was indeed possible “to build up a terrestrial chronology from rotten
shells” imbedded in the rocks. Meanwhile he had constructed the first
geological map of England, which has served as a basis for geological
maps of all other parts of the world. William Smith was now presented
by the Geological Society with the Wollaston Medal, and hailed as “the
Father of English Geology.” He died in 1840. Till the manner as well
as the fact of the first appearance of successive forms of life shall
be solved, it is not easy to surmise how any discovery can be made in
geology equal in value to that which we owe to the genius of William
Smith.--_Saturday Review_, No. 140.


DR. BUCKLAND’s GEOLOGICAL LABOURS.

Sir Henry De la Beche, in his Anniversary Address to the Geological
Society in 1848, on presenting the Wollaston Medal to Dr. Buckland,
felicitously observed:

  It may not be generally known that, while yet a child, at your
  native town, Axminster in Devonshire, ammonites, obtained by your
  father from the lime quarries in the neighbourhood, were presented
  to your attention. As a scholar at Winchester, the chalk, with its
  flints, was brought under your observation, and there it was that
  your collections in natural history first began. Removed to Oxford,
  as a scholar of Corpus Christi College, the future teacher of
  geology in that University was fortunate in meeting with congenial
  tastes in our colleague Mr. W. J. Broderip, then a student at Oriel
  College. It was during your walks together to Shotover Hill, when
  his knowledge of conchology was so valuable to you, enabling you
  to distinguish the shells of the Oxford oolite, that you laid the
  foundation for those field-lectures, forming part of your course
  of geology at Oxford, which no one is likely to forget who has
  been so fortunate at any time as to have attended them. The fruits
  of your walks with Mr. Broderip formed the nucleus of that great
  collection, more especially remarkable for the organic remains
  it contains, which, after the labours of forty years, you have
  presented to the Geological Museum at Oxford, in grave recollection
  of the aid which the endowments of that University, and the leisure
  of its vacations, had afforded you for extensive travelling during
  a residence at Oxford of nearly forty-five years.


DISCOVERIES OF M. AGASSIZ.[34]

This great paleontologist, in the course of his ichthyological
researches, was led to perceive that the arrangement by Cuvier
according to organs did not fulfil its purpose with regard to fossil
fishes, because in the lapse of ages the characteristics of their
structures were destroyed. He therefore adopted the only other
remaining plan, and studied the tissues, which, being less complex
than the organs, are oftener found intact. The result was the very
remarkable discovery, that the tegumentary membrane of fishes is so
intimately connected with their organisation, that if the whole of the
fish has perished except this membrane, it is practicable, by noting
its characteristics, to reconstruct the animal in its most essential
parts. Of the value of this principle of harmony, some idea may be
formed from the circumstance, that on it Agassiz has based the whole
of that celebrated classification of which he is the sole author, and
by which fossil ichthyology has for the first time assumed a precise
and definite shape. How essential its study is to the geologist appears
from the remark of Sir Roderick Murchison, that “fossil fishes have
every where proved the most exact chronometer of the age of rocks.”


SUCCESSION OF LIFE IN TIME.

In the Museum of Economic Geology, in Jermyn Street, may be seen ores,
metals, rocks, and whole suites of fossils stratigraphically arranged
in such a manner that, with an observant eye for form, all may easily
understand the more obvious scientific meanings of the Succession
of Life in Time, and its bearing on geological economies. It is
perhaps scarcely an exaggeration to say, that the greater number of
so-called educated persons are still ignorant of the meaning of this
great doctrine. They would be ashamed not to know that there are many
suns and material worlds besides our own; but the science, equally
grand and comprehensible, that aims at the discovery of the laws that
regulated the creation, extension, decadence, and utter extinction of
many successive species, genera, and whole orders of life, is ignored,
or, if intruded on the attention, is looked on as an uncertain and
dangerous dream,--and this in a country which was almost the nursery of
geology, and which for half a century has boasted the first Geological
Society in the world.--_Saturday Review_, No. 140.


PRIMITIVE DIVERSITY AND NUMBERS OF ANIMALS IN GEOLOGICAL TIMES.

Professor Agassiz considers that the very fact of certain stratified
rocks, even among the oldest formations, being almost entirely made
up of fragments of organised beings, should long ago have satisfied
the most sceptical that both _animal and vegetable life were as active
and profusely scattered upon the whole globe at all times, and during
all geological periods, as they are now_. No coral reef in the Pacific
contains a larger amount of organic _débris_ than some of the limestone
deposits of the tertiary, of the cretaceous, or of the oolitic, nay
even of the paleozoic period; and the whole vegetable carpet covering
the present surface of the globe, even if we were to consider only
the luxuriant vegetation of the tropics, leaving entirely out of
consideration the entire expanse of the ocean, as well as those tracts
of land where, under less favourable circumstances, the growth of
plants is more reduced,--would not form one single seam of workable
coal to be compared to the many thick beds contained in the rocks of
the carboniferous period alone.


ENGLAND IN THE EOCENE PERIOD.

Eocene is Sir Charles Lyell’s term for the lowest group of the Tertiary
system in which the dawn of recent life appears; and any one who wishes
to realise what was the aspect presented by this country during the
Eocene period, need only go to Sheerness. If, leaving that place behind
him, he walks down the Thames, keeping close to the edge of the water,
he will find whole bushels of pyritised pieces of twigs and fruits.
These fruits and twigs belong to plants nearly allied to the screw-pine
and custard-apple, and to various species of palms and spice-trees
which now flourish in the Eastern Archipelago. At the time they were
washed down from some neighbouring land, not only crocodilian reptiles,
but sharks and innumerable turtles, inhabited a sea or estuary which
now forms part of the London district; and huge boa-constrictors glided
amongst the trees which fringed the adjoining shores.

Countless as are the ages which intervened between the Eocene period
and the time when the little jawbones of Stonesfield were washed down
to the place where they were to await the day when science should bring
them again to light, not one mammalian genus which now lives upon our
plane has been discovered amongst Eocene strata. We have existing
families, but nothing more.--_Professor Owen._


FOOD OF THE IGUANODON.

Dr. Mantell, from the examination of the anterior part of the right
side of the lower jaw of an Iguanodon discovered in a quarry in Tilgate
Forest, Sussex, has detected an extraordinary deviation from all
known types of reptilian organisation, and which could not have been
predicated; namely, that this colossal reptile, which equalled in bulk
the gigantic Edentata of South America, and like them was destined to
obtain support from comminuted vegetable substances, was also furnished
with a large prehensile tongue and fleshy lips, to serve as instruments
for seizing and cropping the foliage and branches of trees; while
the arrangement of the teeth as in the ruminants, and their internal
structure, which resembles that of the molars of the sloth tribe in the
vascularity of the dentine, indicate adaptations for the same purpose.

Among the physiological phenomena revealed by paleontology, there
is not a more remarkable one than this modification of the type of
organisation peculiar to the class of reptiles to meet the conditions
required by the economy of a lizard placed under similar physical
relations; and destined to effect the same general purpose in the
scheme of nature as the colossal Edentata of former ages and the large
herbivorous mammalia of our own times.


THE PTERODACTYL--THE FLYING DRAGON.

The Tilgate beds of the Wealden series, just mentioned, have yielded
numerous fragments of the most remarkable reptilian fossils yet
discovered, and whose wonderful forms denote them to have thronged
the shallow seas and bays and lagoons of the period. In the grounds
of the Crystal Palace at Sydenham the reader will find restorations
of these animals sufficiently perfect to illustrate this reptilian
epoch. They include the _iguanodon_, an herbivorous lizard exceeding
in size the largest elephant, and accompanied by the equally gigantic
and carnivorous _megalosaurus_ (great saurian), and by the two yet more
curious reptiles, the _pylæosaurus_ (forest, or weald, saurian) and the
pterodactyl (from _pteron_, ‘wing,’ and _dactylus_, ‘a finger’), an
enormous bat-like creature, now running upon the ground like a bird;
its elevated body and long neck not covered with feathers, but with
skin, naked, or resplendent with glittering scales; its head like that
of a lizard or crocodile, and of a size almost preposterous compared
with that of the body, with its long fore extremities stretched out,
and connected by a membrane with the body and hind legs.

Suddenly this mailed creature rose in the air, and realised or even
surpassed in strangeness _the flying dragon of fable_: its fore-arms
and its elongated wing-finger furnished with claws; hand and fingers
extended, and the interspace filled up by a tough membrane; and its
head and neck stretched out like that of the heron in its flight. When
stationary, its wings were probably folded back like those of a bird;
though perhaps, by the claws attached to its fingers, it might suspend
itself from the branches of trees.


MAMMALIA IN SECONDARY ROCKS.

It was supposed till very lately that few if any Mammalia were to be
found below the Tertiary rocks, _i. e._ those above the chalk; and this
supposed fact was very comfortable to those who support the doctrine
of “progressive development,” and hold, with the notorious _Vestiges
of Creation_, that a fish by mere length of time became a reptile,
a lemur an ape, and finally an ape a man. But here, as in a hundred
other cases, facts, when duly investigated, are against their theory.
A mammal jaw had been already discovered by Mr. Brodie on the shore at
the back of Swanage Point, in Dorsetshire, when Mr. Beckles, F.G.S.,
traced the vein from which this jaw had been procured, and found it
to be a stratum about five inches thick, at the base of the Middle
Purbeck beds; and after removing many thousand tons of rock, and laying
bare an area of nearly 7000 square feet (the largest cutting ever made
for purely scientific purposes), he found reptiles (tortoises and
lizards) in hundreds; but the most important discovery was that of
the jaws of at least fourteen different species of mammalia. Some of
these were herbivorous, some carnivorous, connected with our modern
shrews, moles, hedgehogs, &c.; but all of them perfectly developed and
highly-organised quadrupeds. Ten years ago, no remains of quadrupeds
were believed to exist in the Secondary strata. “Even in 1854,” says
Sir Charles Lyell (in a supplement to the fifth edition of his _Manual
of Elementary Geology_), “only six species of mammals from rocks older
than the Tertiary were known in the whole world.” We now possess
evidence of the existence of fourteen species, belonging to eight or
nine genera, from the fresh-water strata of the Middle Purbeck Oolite.
It would be rash now to fix a limit in past time to the existence of
quadrupeds.--_The Rev. C. Kingsley._


FOSSIL HUMAN BONES.

In the paleontological collection in the British Museum is preserved
a considerable portion of a human skeleton imbedded in a slab of
rock, brought from Guadaloupe, and often referred to in opposition to
the statement that hitherto _no fossil human hones have been found_.
The presence of these bones, however, has been explained by the
circumstance of a battle and the massacre of a tribe of Galtibis by the
Caribs, which took place near the spot in which the bones were found
about 130 years ago; for as the bodies of the slain were interred on
the seashore, their skeletons may have been subsequently covered by
sand-drift, which has since consolidated into limestone.

It will be seen by reference to the _Philosophical Transactions_,
that on the reading of the paper upon this discovery to the Royal
Society, in 1814, Sir Joseph Banks, the president, considered the
“fossil” to be of very modern formation, and that probably, from the
contiguity of a volcano, the temperature of the water may have been
raised at some time, and dissolving carbonate of lime readily, may
have deposited about the skeleton in a comparatively short period hard
and solid stone. Every person may be convinced of the rapidity of the
formation and of the hardness of such stone by inspecting the inside of
tea-kettles in which hard water is boiled.

  Descriptions of petrifactions of human bodies appear to refer to
  the conversion of bodies into adipocere, and not into stone. All
  the supposed cases of petrifaction are probably of this nature.
  The change occurs only when the coffin becomes filled with water.
  The body, converted into adipocere, floats on the water. The
  supposed cases of changes of position in the grave, bursting open
  the coffin-lids, turning over, crossing of limbs, &c., formerly
  attributed to the coming to life of persons buried who were not
  dead, is now ascertained to be due to the same cause. The chemical
  change into adipocere, and the evolution of gases, produce these
  movements of dead bodies.--_Mr. Trail Green._


THE MOST ANCIENT FISHES.

Among the important results of Sir Roderick Murchison’s establishment
of the Silurian system is the following:

  That as the Lower Silurian group, often of vast dimensions, has
  never afforded the smallest vestige of a Fish, though it abounds
  in numerous species of the _marine_ classes,--corals, _crinoidea_,
  _mollusca_, and _crustacea_; and as in Scandinavia and Russia,
  where it is based on rocks void of fossils, its lowest stratum
  contains _fucoids_ only,--Sir R. Murchison has, after fifteen years
  of laborious research steadily directed to this point, arrived at
  the conclusion, that a very long period elapsed after life was
  breathed into the waters before the lowest order of vertebrata was
  created; the earliest fishes being those of the Upper Silurian
  rocks, which he was the first to discover, and which he described
  “as the most ancient beings of their class which have yet been
  brought to light.” Though the Lower Silurian rocks of various parts
  of the world have since been ransacked by multitudes of prying
  geologists, who have exhumed from them myriads of marine fossils,
  not a single ichthyolite has been found in any stratum of higher
  antiquity than the Upper Silurian group of Murchison.

The most remarkable of all fossil fishes yet discovered have been found
in the Old Red Sandstone cliffs at Dorpat, where the remains are so
gigantic (one bone measuring _two feet nine inches_ in length) that
they were at first supposed to belong to saurians.

Sir Roderick’s examination of Russia has, in short, proved that _the
ichthyolites and mollusks which, in Western Europe, are separately
peculiar to smaller detached basins, were here (in the British Isles)
cohabitants of many parts of the same great sea_.


EXTINCT CARNIVOROUS ANIMALS OF BRITAIN.

Professor Owen has thus forcibly illustrated the Carnivorous Animals
which preyed upon and restrained the undue multiplication of the
vegetable feeders. First we have the bear family, which is now
represented in this country only by the badger. We were once blest,
however, with many bears. One species seems to have been identical
with the existing brown bear of the European continent. Far larger
and more formidable was the gigantic cave-bear (_Ursus spelæus_),
which surpassed in size his grisly brother of North America. The
skull of the cave-bear differs very much in shape from that of its
small brown relative just alluded to; the forehead, in particular,
is much higher,--to be accounted for by an arrangement of air-cells
similar to those which we have already remarked in the elephant. The
cave-bear has left its remains in vast abundance in Germany. In our own
caves, the bones of hyænas are found in greater quantities. The marks
which the teeth of the hyæna make upon the bones which it gnaws are
quite unmistakable. Our English hyænas had the most undiscriminating
appetite, preying upon every creature, their own species amongst
others. Wolves, not distinguishable from those which now exist in
France and Germany, seem to have kept company with the hyænas; and the
_Felis spelæa_, a sort of lion, but larger than any which now exists,
ruled over all weaker brutes. Here, says Professor Owen, we have the
original British Lion. A species of _Machairodus_ has left its remains
at Kent’s Hole, near Torquay. In England we had also the beaver, which
still lingers on the Danube and the Rhone, and a larger species, which
has been called Trogontherium (gnawing beast), and a gigantic mole.


THE GREAT CAVE TIGER OR LION OF BRITAIN.

Remains of this remarkable animal of the drift or gravel period
of this country have been found at Brentford and elsewhere near
London. Speaking of this animal, Professor Owen observes, that “it
is commonly supposed that the Lion, the Tiger, and the Jaguar are
animals peculiarly adapted to a tropical climate. The genus Felis (to
which these animals belong) is, however, represented by specimens
in high northern latitudes, and in all the intermediate countries
to the equator.” The chief condition necessary for the presence of
such animals is an abundance of the vegetable-feeding animals. It
is thus that the Indian tiger has been known to follow the herds of
antelope and deer in the lofty mountains of the Himalaya to the verge
of perpetual snow, and far into Siberia. “It need not, therefore,”
continues Professor Owen, “excite surprise that indications should
have been discovered in the fossil relics of the ancient mammalian
population of Europe of a large feline animal, the contemporary of the
mammoth, of the tichorrhine rhinoceros, of the great gigantic cave-bear
and hyæna, and the slayer of the oxen, deer, and equine quadrupeds that
so abounded during the same epoch.” The dimensions of this extinct
animal equal those of the largest African lion or Bengal tiger; and
some bones have been found which seem to imply that it had even more
powerful limbs and larger paws.


THE MAMMOTHS OF THE BRITISH ISLES.

Dr. Buckland has shown that for long ages many species of carnivorous
animals now extinct inhabited the caves of the British islands. In low
tracts of Yorkshire, where tranquil lacustrine (lake-like) deposits
have occurred, bones (even those of the lion) have been found so
perfectly unbroken and unworn, in fine gravel (as at Market Weighton),
that few persons would be disposed to deny that such feline and other
animals once roamed over the British isles, as well as other European
countries. Why, then, is it improbable that large elephants, with a
peculiarly thick integument, a close coating of wool, and much long
shaggy hair, should have been the occupants of wide tracts of Northern
Europe and Asia? This coating, Dr. Fleming has well remarked, was
probably as impenetrable to rain and cold as that of the monster ox of
the polar circle. Such is the opinion of Sir Roderick Murchison, who
thus accounts for the disappearance of the mammoths from Britain:

  When we turn from the great Siberian continent, which, anterior
  to its elevation, was the chief abode of the mammoths, and look
  to the other parts of Europe, where their remains also occur, how
  remarkable is it that we find the number of these creatures to be
  justly proportionate to the magnitude of the ancient masses of land
  which the labours of geologists have defined! Take the British
  isles, for example, and let all their low, recently elevated
  districts be submerged; let, in short, England be viewed as the
  comparatively small island she was when the ancient estuary of the
  Thames, including the plains of Hyde Park, Chelsea, Hounslow, and
  Uxbridge, were under the water; when the Severn extended far into
  the heart of the kingdom, and large eastern tracts of the island
  were submerged,--and there will then remain but moderately-sized
  feeding-grounds for the great quadrupeds whose bones are found in
  the gravel of the adjacent rivers and estuaries.

This limited area of subsistence could necessarily only keep up a small
stock of such animals; and, just as we might expect, the remains of
British mammoths occur in very small numbers indeed, when compared with
those of the great charnel-houses of Siberia, into which their bones
had been carried down through countless ages from the largest mass of
surface which geological inquiries have yet shown to have been _dry
land_ during that epoch.

The remains of the mammoth, says Professor Owen, have been found in
all, or almost all, the counties of England. Off the coast of Norfolk
they are met with in vast abundance. The fishermen who go to catch
turbot between the mouth of the Thames and the Dutch coast constantly
get their nets entangled in the tusks of the mammoth. A collection
of tusks and other remains, obtained in this way, is to be seen at
Ramsgate. In North America, this gigantic extinct elephant must have
been very common; and a large portion of the ivory which supplies
the markets of Europe is derived from the vast mammoth graveyards of
Siberia.

The mammoth ranged at least as far north as 60°. There is no doubt
that, at the present day, many specimens of the musk-ox are annually
becoming imbedded in the mud and ice of the North-American rivers.

It is curious to observe, that the mammoth teeth which are met with
in caves generally belonged to young mammoths, who probably resorted
thither for shelter before increasing age and strength emboldened them
to wander far afield.


THE RHINOCEROS AND HIPPOPOTAMUS OF ENGLAND.

The mammoth was not the only giant that inhabited England in the
Pliocene or Upper Tertiary period. We had also here the _Rhinoceros
tichorrhinus_, or “strongly walled about the nose,” remains of which
have been discovered in enormous quantities in the brickfields about
London. Pallas describes an entire specimen of this creature, which was
found near Yakutsk, the coldest town on the globe. Another rhinoceros,
_leptorrhinus_ (fine nose), dwelt with the elephant of Southern Europe.
In Siberia has been discovered the Elaimotherium, forming a link
between the rhinoceros and the horse.

In the days of the mammoth, we had also in England a Hippopotamus,
rather larger than the species which now inhabits the Nile. Of our
British hippopotamus some remains were dug up by the workmen in
preparing the foundations of the New Junior United Service Club-house,
in Regent-street.


THE ELEPHANT AND TORTOISE.

The idea of an Elephant standing on the back of a Tortoise was often
laughed at as an absurdity, until Captain Cautley and Dr. Falconer
at length discovered in the hills of Asia the remains of a tortoise
in a fossil state of such a size that an elephant could easily have
performed the above feat.


COEXISTENCE OF MAN AND THE MASTODON.

Dr. C. F. Winslow has communicated to the Boston Society of Natural
History the discovery of the fragment of a human cranium 180 feet below
the surface of the Table Mountain, California. Now the mastodon’s
bones being found in the same deposits, points very clearly to the
probability of the appearance of the human race on the western
portions of North America at least before the extinction of those huge
creatures. Fragments of mastodon and _Elephas primigenius_ have been
taken ten and twenty feet below the surface in the above locality;
where this discovery of human and mastodon remains gives strength
to the possible truth of an old Indian tradition,--the contemporary
existence of the mammoth and aboriginals in this region of the globe.


HABITS OF THE MEGATHERIUM.

Much uncertainty has been felt about the habits of the Megatherium,
or Great Beast. It has been asked whether it burrowed or climbed, or
what it did; and difficulties have presented themselves on all sides of
the question. Some have thought that it lived in trees as much larger
than those which now exist as the Megatherium itself is larger than
the common sloth.[35] This, however, is now known to be a mistake.
It did not climb trees--it pulled them down; and in order to do this
the hinder parts of its skeleton were made enormously strong, and
its prehensile fore-legs formed so as to give it a tremendous power
over any thing which it grasped. Dr. Buckland suggested that animals
which got their living in this way had a very fair chance of having
their heads broken. While Professor Owen was still pondering over this
difficulty, the skull of a cognate animal, the Mylodon, came into
his hands. Great was his delight when he found that the mylodon not
only had his head broken, but broken in two different places, at two
different times; and moreover so broken that the injury could only have
been inflicted by some such agent as a fallen tree. The creature had
recovered from the first blow, but had evidently died of the second.
This tribe had, as it turns out, two skulls, an outer and an inner
one--given them, as it would appear, expressly with a view to the very
dangerous method in which they were intended to obtain their necessary
food.

The dentition of the megatherium is curious. The elephant gets teeth
as he wants them. Nature provided for the comfort of the megatherium
in another way. It did not get new teeth, but the old ones went on
for ever growing as long as the animal lived; so that as fast as one
grinding surface became useless, another supplied its place.


THE DINOTHERIUM, OR TERRIBLE BEAST.

The family of herbivorous Cetaceans are connected with the
Pachydermata of the land by one of the most wonderful of all the
extinct creatures with which geologists have made us acquainted.
This is the _Dinotherium_, or Terrible Beast. The remains of this
animal were found in Miocene sands at Eppelsheim, about forty miles
from Darmstadt. It must have been larger than the largest extinct or
living elephant. The most remarkable peculiarity of its structure is
the enormous tusks, curving downwards and terminating its lower jaw.
It appears to have lived in the water, where the immense weight of
these formidable appendages would not be so inconvenient as on land.
What these tusks were used for is a mystery; but perhaps they acted
as pickaxes in digging up trees and shrubs, or as harrows in raking
the bottom of the water. Dr. Buckland used to suggest that they were
perhaps employed as anchors, by means of which the monster might
fasten itself to the bank of a stream and enjoy a comfortable nap. The
extreme length of the _Dinotherium_ was about eighteen feet. Professor
Kemp, in his restoration of the animal, has given it a trunk like
that of the elephant, but not so long, and the general form of the
tapir.--_Professor Owen._


THE GLYPTODON.

There are few creatures which we should less have expected to find
represented in fossil history by a race of gigantic brethren than the
armadillo. The creature is so small, not only in size but in all its
works and ways, that we with difficulty associate it with the idea of
magnitude. Yet Sir Woodbine Parish has discovered evidences of enormous
animals of this family having once dwelt in South America. The huge
loricated (plated over) creature whose relics were first sent has
received the name of Glyptodon, from its sculptured teeth. Unlike the
small armadillos, it was unable to roll itself up into a ball; though
an enormous carnivore which lived in those days must have made it
sometimes wish it had the power to do so. When attacked, it must have
crouched down, and endeavoured to make its huge shell as good a defence
as possible.--_Professor Owen._


INMATES OF AN AUSTRALIAN CAVERN.

From the fossil-bone caverns in Wellington Valley, in 1830, were sent
to Professor Owen several bones which belonged, as it turned out, to
gigantic kangaroos, immensely larger than any existing species; to
a kind of wombat, to formidable dasyures, and several other genera.
It also appeared that the bones, which were those of herbivores, had
evidently belonged to young animals, while those of the carnivores
were full-sized; a fact which points to the relations between the two
families having been any thing but agreeable to the herbivores.


THE POUCH-LION OF AUSTRALIA.

The _Thylacoleo_ (Pouch-Lion) was a gigantic marsupial carnivore, whose
character and affinities Professor Owen has, with exquisite scientific
tact, made out from very small indications. This monster, which had
kangaroos with heads three feet long to feed on, must have been one of
the most extraordinary animals of the antique world.


THE CONEY OF SCRIPTURE.

Paleontologists have pointed out the curious fact that the Hyrax,
called ‘coney’ in our authorised version of the Bible, is really only
a diminutive and hornless rhinoceros. Remains have been found at
Eppelsheim which indicate an animal more like a gigantic Hyrax than
any of the existing rhinoceroses. To this the name of _Acerotherium_
(Hornless Beast) has been given.


A THREE-HOOFED HORSE.

Professor Owen describes the _Hipparion_, or Three-hoofed Horse, as the
first representative of a family so useful to mankind. This animal,
in addition to its true hoof, appears to have had two additional
elementary hoofs, analogous to those which we see in the ox. The object
of these no doubt was to enable the Hipparion to extricate his foot
with greater ease than he otherwise could when it sank through the
swampy ground on which he lived.


TWO MONSTER CARNIVORES OF FRANCE.

A huge carnivorous creature has been found in Miocene strata in
France, in which country it preyed upon the gazelle and antelope. It
must have been as large as a grisly bear, but in general appearance
and teeth more like a gigantic dog. Hence the name of _Amphicyon_
(Doubtful Dog) has been assigned to it. This animal must have derived
part of its support from vegetables. Not so the coeval monster which
has been called _Machairodus_ (Sabre-tooth). It must have been
somewhat akin to the tiger, and is by far the most formidable animal
which we have met with in our ascending progress through the extinct
mammalia.--_Professor Owen._


GEOLOGY OF THE SHEEP.

No unequivocal fossil remains of the sheep have yet been found in
the bone-caves, the drift, or the more tranquil stratified newer
Pliocene deposits, so associated with the fossil bones of oxen,
wild-boars, wolves, foxes, otters, &c., as to indicate the coevality
of the sheep with those species, or in such an altered state as to
indicate them to have been of equal antiquity. Professor Owen had his
attention particularly directed to this point in collecting evidence
for a history of British Fossil Mammalia. No fossil core-horns of the
sheep have yet been any where discovered; and so far as this negative
evidence goes, we may infer that the sheep is not geologically more
ancient than man; that it is not a native of Europe, but has been
introduced by the tribes who carried hither the germs of civilisation
in their migrations westward from Asia.


THE TRILOBITE.

Among the earliest races we have those remarkable forms, the
Trilobites, inhabiting the ancient ocean. These crustacea remotely
resemble the common wood-louse, and like that animal they had the power
of rolling themselves into a ball when attacked by an enemy. The eye of
the trilobite is a most remarkable organ; and in that of one species,
_Phacops caudatus_, not less than 250 lenses have been discovered. This
remarkable optical instrument indicates that these creatures lived
under similar conditions to those which surround the crustacea of the
present day.--_Hunt’s Poetry of Science._


PROFITABLE SCIENCE.

In that strip of reddish colour which runs along the cliffs of Suffolk,
and is called the Redcrag, immense quantities of cetacean remains have
been found. Four different kinds of whales, little inferior in size to
the whalebone whale, have left their bones in this vast charnel-house.
In 1840, a singularly perplexing fossil was brought to Professor Owen
from this Redcrag. No one could say what it was. He determined it to
be the tooth of a cetacean, a unique specimen. Now the remains of
cetaceans in the Suffolk crag have been discovered in such enormous
quantities, that many thousands a-year are made by converting them into
manure.


EXTINCT GIGANTIC BIRDS OF NEW ZEALAND.

In the islands of New Zealand have been found the bones of large
extinct wingless Birds, belonging to the Post Tertiary or Recent
system, which have been deposited by the action of rivers. The bird
is named _Moa_ by the natives, and _Dinornis_ by naturalists: some
of the bones have been found in two caves in the North Island, and
have been sold by the natives at an extraordinary price. The caves
occur in limestone rocks, and the bones are found beneath earth and
a soft deposit of carbonate of lime. The largest of the birds is
stated to have stood thirteen or fourteen feet, or twice the height
of the ostrich; and its egg large enough to fill the hat of a man as
a cup. Several statements have appeared of these birds being still
in existence, but there is every reason to believe the Moa to be
altogether extinct.

An extensive collection of remains of these great wingless birds has
been collected in New Zealand by Mr. Walter Mantell, and deposited in
the British Museum. Among these bones Professor Owen has discovered a
species which he regards as the most remarkable of the feathered class
for its prodigious strength and massive proportions, and which he names
_Dinornis elephantopus_, or elephant-footed, of which the Professor
has been able to construct an entire lower limb: the length of the
metatarsal bone is 9¼ inches, the breadth of the lower end being
5-1/3 inches. The extraordinary proportions of the metatarsus of this
wingless bird will, however, be still better understood by comparison
with the same bone in the ostrich, in which the metatarsus is 19 inches
in length, the breadth of its lower end being only 2½ inches. From
the materials accumulated by Mr. Mantell, the entire skeleton of the
_Dinornis elephantopus_ has been reconstructed; and now forms a worthy
companion of the Megatherium and Mastodon in the gallery of fossil
remains in the British Museum. This species of _Dinornis_ appears to
have been restricted to the Middle Island of New Zealand.[36]

Another specimen of the remains of the _Dinornis_ is preserved in the
Museum of the Royal College of Surgeons, in Lincoln’s-Inn Fields; and
the means by which the college obtained this valuable acquisition is
thus graphically narrated by Mr. Samuel Warren, F.R.S.:

  In the year 1839, Professor Owen was sitting alone in his study,
  when a shabbily-dressed man made his appearance, announcing that he
  had got a great curiosity, which he had brought from New Zealand,
  and wished to dispose of to him. It had the appearance of an old
  marrow-bone, about six inches in length, and rather more than
  two inches in thickness, _with both extremities broken off_; and
  Professor Owen considered that, to whatever animal it might have
  belonged, the fragment must have lain in the earth for centuries.
  At first he considered this same marrow-bone to have belonged to
  an ox, at all events to a quadruped; for the wall or rim of the
  bone was six times as thick as the bone of any bird, even of the
  ostrich. He compared it with the bones in the skeleton of an ox, a
  horse, a camel, a tapir, and every quadruped apparently possessing
  a bone of that size and configuration; but it corresponded with
  none. On this he very narrowly examined the surface of the bony
  rim, and at length became satisfied that this fragment must have
  belonged to _a bird_!--to one at least as large as an ostrich, but
  of a totally different species; and consequently one never before
  heard of, as an ostrich was by far the biggest bird known.

  From the difference in the _strength_ of the bone, the ostrich
  being unable to fly, so must have been unable this unknown bird;
  and so our anatomist came to the conclusion that this old shapeless
  bone indicated the former existence in New Zealand of some huge
  bird, at least as great as an ostrich, but of a far heavier and
  more sluggish kind. Professor Owen was confident of the validity
  of his conclusions, but would communicate that confidence to
  no one else; and notwithstanding attempts to dissuade him from
  committing his views to the public, he printed his deductions
  in the _Transactions of the Zoological Society for 1839_, where
  fortunately they remain on record as conclusive evidence of the
  fact of his having then made this guess, so to speak, in the dark.
  He caused the bone, however, to be engraved; and having sent a
  hundred copies of the engraving to New Zealand, in the hope of
  their being distributed and leading to interesting results, he
  patiently waited for three years,--viz. till the year 1842,--when
  he received intelligence from Dr. Buckland, at Oxford, that a
  great box, just arrived from New Zealand, consigned to himself,
  was on its way, unopened, to Professor Owen, who found it filled
  with bones, palpably of a bird, one of which bones was three feet
  in length, and much more than double the size of any bone in the
  ostrich!

  And out of the contents of this box the Professor was positively
  enabled to articulate almost the entire skeleton of a huge wingless
  bird between TEN and ELEVEN feet in height, its bony structure in
  strict conformity with the fragment in question; and that skeleton
  may at any time be seen at the Museum of the College of Surgeons,
  towering over, and nearly twice the height of, the skeleton of
  an ostrich; and at its feet lying the old bone from which alone
  consummate anatomical science had deduced such an astounding
  reality,--the existence of an enormous extinct creature of the bird
  kind, in an island where previously no bird had been known to exist
  larger than a pheasant or a common fowl!--_Lecture on the Moral and
  Intellectual Development of the present Age._[37]


“THE MAESTRICHT SAURIAN FOSSIL” A FRAUD.

In 1795, there was stated to have been discovered in the stone quarries
adjoining Maestricht the remains of the gigantic _Mosœsaurus_ (Saurian
of the Meuse), an aquatic reptile about twenty-five feet long, holding
an intermediate place between the Monitors and Iguanas. It appears
to have had webbed feet, and a tail of such construction as to have
served for a powerful oar, and enabled the animal to stem the waves of
the ocean, of which Cuvier supposed it to have been an inhabitant. It
is thus referred to by Dr. Mantell, in his _Medals of Creation_: “A
specimen, with the jaws and bones of the palate, now in the Museum at
Paris, has long been celebrated; and is still the most precious relic
of this extinct reptile hitherto discovered.” An admirable cast of this
specimen is preserved in the British Museum, in a case near the bones
of the Iguanodon. This is, however, useless, as Cuvier is proved to
have been imposed upon in the matter.

  M. Schlegel has reported to the French Academy of Sciences, that
  he has ascertained beyond all doubt that the famous fossil saurian
  of the quarries of Maestricht, described as a wonderful curiosity
  by Cuvier, is nothing more than an impudent fraud. Some bold
  impostor, it seems, in order to make money, placed a quantity of
  bones in the quarries in such a way as to give them the appearance
  of having been recently dug up, and then passed them off as
  specimens of antediluvian creation. Being successful in this, he
  went the length of arranging a number of bones so as to represent
  an entire skeleton; and had thus deceived the learned Cuvier. In
  extenuation of Cuvier’s credulity, it is stated that the bones were
  so skilfully coloured as to make them look of immense antiquity,
  and he was not allowed to touch them lest they should crumble to
  pieces. But when M. Schlegel subjected them to rude handling, he
  found that they were comparatively modern, and that they were
  placed one by the other without that profound knowledge of anatomy
  which was to have been expected from the man bold enough to execute
  such an audacious fraud.


“THE OLDEST PIECE OF WOOD UPON EARTH.”

The most remarkable vegetable relic which the Lower Old Red Sandstone
has given us is a small fragment of a coniferous tree of the Araucarian
family, which formed one of the chief ornaments of the late Hugh
Miller’s museum, and to which he used to point as the oldest piece
of wood upon earth. He found it in one of the ichthyolite beds of
Cromarty, and thus refers to it in his _Testimony of the Rocks_:

  On what perished land of the early paleozoic ages did this
  venerably antique tree cast root and flourish, when the extinct
  genera Pterichthys and Coccoeteus were enjoying life by millions
  in the surrounding seas, long ere the flora or fauna of the coal
  measures had begun to be?

  The same nodule which enclosed this lignite contained part of
  another fossil, the well-marked scales of _Diplacanthus striatus_,
  an ichthyolite restricted to the Lower Old Red Sandstone
  exclusively. If there be any value in paleontological evidence,
  this Cromarty lignite must have been deposited in a sea inhabited
  by the Coccoeteus and Diplacanthus. It is demonstrable that, while
  yet in a recent state, a Diplacanthus lay down and died beside it;
  and the evidence in the case is unequivocally this, that in the
  oldest portion of the oldest terrestrial flora yet known there
  occurs the fragment of a tree quite as high in the scale as the
  stately Norfolk-Island pine or the noble cedar of Lebanon.


NO FOSSIL ROSE.

Professor Agassiz, in a lecture upon the trees of America, states a
remarkable fact in regard to the family of the rose,--which includes
among its varieties not only many of the most beautiful flowers, but
also the richest fruits, as the apple, pear, peach, plum, apricot,
cherry, strawberry, raspberry, &c.,--namely, that _no fossil plants
belonging to this family have ever been discovered by geologists_! This
M. Agassiz regards as conclusive evidence that the introduction of this
family of plants upon the earth was coeval with, or subsequent to, the
creation of man, to whose comfort and happiness they seem especially
designed by a wise Providence to contribute.


CHANGES ON THE EARTH’S SURFACE.

In the Imperial Library at Paris is preserved a manuscript work by
an Arabian writer, Mohammed Karurini, who flourished in the seventh
century of the Hegira, or at the close of the thirteenth century of
our era. Herein we find several curious remarks on aerolites and
earthquakes, and the successive changes of position which the land and
sea have undergone. Of the latter class is the following beautiful
passage from the narrative of Khidz, an allegorical personage:

  I passed one day by a very ancient and wonderfully populous city,
  and asked one of its inhabitants how long it had been founded. “It
  is indeed a mighty city,” replied he; “we know not how long it
  has existed, and our ancestors were on this subject as ignorant
  as ourselves.” Five centuries afterwards, as I passed by the same
  place, I could not perceive the slightest vestige of the city. I
  demanded of a peasant who was gathering herbs upon its former site
  how long it had been destroyed. “In sooth, a strange question,”
  replied he; “the ground here has never been different from what you
  now behold it.” “Was there not of old,” said I, “a splendid city
  here?” “Never,” answered he, “so far as we have seen; and never
  did our fathers speak to us of any such.” On my return there five
  hundred years afterwards, _I found the sea in the same place_; and
  on its shores were a party of fishermen, of whom I inquired how
  long the land had been covered by the waters. “Is this a question,”
  say they, “for a man like you? This spot has always been what it is
  now.” I again returned five hundred years afterwards; the sea had
  disappeared: I inquired of a man who stood alone upon the spot how
  long this change had taken place, and he gave me the same answer as
  I had received before. Lastly, on coming back again after an equal
  lapse of time, I found there a flourishing city, more populous and
  more rich in beautiful buildings than the city I had seen the first
  time; and when I would fain have informed myself concerning its
  origin, the inhabitants answered me, “Its rise is lost in remote
  antiquity: we are ignorant how long it has existed, and our fathers
  were on this subject as ignorant as ourselves.”

This striking passage was quoted in the _Examiner_, in 1834. Surely in
this fragment of antiquity we trace the “geological changes” of modern
science.


GEOLOGICAL TIME.

Many ingenious calculations have been made to approximate the dates
of certain geological events; but these, it must be confessed, are
more amusing than instructive. For example, so many inches of silt are
yearly laid down in the delta of the Mississippi--how many centuries
will it have taken to accumulate a thickness of 30, 60, or 100 feet?
Again, the ledges of Niagara are wasting at the rate of so many feet
per century--how many years must the river have taken to cut its way
back from Queenstown to the present Falls? Again, lavas and melted
basalts cool, according to the size of the mass, at the rate of so many
degrees in a given time--how many millions of years must have elapsed,
supposing an original igneous condition of the earth, before its crust
had attained a state of solidity? or further, before its surface had
cooled down to the present mean temperature? For these and similar
computations, the student will at once perceive we want the necessary
uniformity of factor; and until we can bring elements of calculation as
exact as those of astronomy to bear on geological chronology, it will
be better to regard our “eras” and “epochs” and “systems” as so many
terms, indefinite in their duration, but sufficient for the magnitude
of the operations embraced within their limits.--_Advanced Textbook of
Geology, by David Page, F.G.S._

M. Rozet, in 1841, called attention to the fact, that the causes which
have produced irregularities in the structure of the globe have not yet
ceased to act, as is proved by earthquakes, volcanic eruptions, slow
and continuous movements of the crust of the earth in certain regions,
&c. We may, therefore, yet see repeated the great catastrophes which
the surface of the earth has undergone anteriorly to the historical
period.

At the meeting of the British Association in 1855, Mr. Hopkins excited
much controversy by his startling speculation--that 9000 years ago
the site on which London now stands was in the torrid zone; and that,
according to perpetual changes in progress, the whole of England would
in time arrive within the Arctic circle.


CURIOUS CAUSE OF CHANGE OF LEVEL.

Professor Hennessey, in 1857, _found the entire mass of rock and
hill on which the Armagh Observatory is erected to be slightly, but
to an astronomer quite perceptibly, tilted or canted, at one season
to the east, at another to the west_. This he at first attributed to
the varying power of the sun’s radiation to heat and expand the rock
throughout the year; but he subsequently had reason to attribute it
rather to the infiltration of water to the parts where the clay-slate
and limestone rocks met, the varying quantity of the water exerting
a powerful hydrostatic energy by which the position of the rock is
slightly varied.

Now Armagh and its observatory stand at the junction of the mountain
limestone with the clay-slate, having, as it were, one leg on the
former and the other on the latter; and both rocks probably reach
downwards 1000 or 2000 feet. When rain falls, the one will absorb
more water than the other; both will gain an increase of conductive
power; but the one which has absorbed most water will have the greatest
increase, and being thus the better conductor, will _draw a greater
portion of heat from the hot nucleus below to the surface_--will
become, in fact, temporarily hotter, and, as a consequence, _expand
more than the other_. In a word, _both rocks will expand at the wet
season; but the best conductor, or most absorbent rock, will expand
most, and seem to tilt the hill to one side; at the dry season it will
subside most, and the hill will seem to be tilted in the opposite
direction_.

The fact is curious, and not less so are the results deducible from
it. First, hills are higher at one season than another; a fact we
might have supposed, but never could have ascertained by measurement.
Secondly, they are highest, not, as we should have supposed, at the
hottest season, but at the wettest. Thirdly, it is from the _different
rates_ of expansion of different rocks that this has been discovered.
Fourthly, it is by converse with the _heavens_ that it has been made
known to us. A variation of probably half a second, or less, in the
right ascension of three or four stars, observed at different seasons,
no doubt revealed the fact to the sagacious astronomer of Armagh, and
even enabled him to divine its cause.

  Professor Hennessey observes in connection with this phenomenon,
  that a very small change of ellipticity would suffice to lay
  bare or submerge extensive tracts of the globe. If, for example,
  the mean ellipticity of the ocean increased from 1/300 to 1/299,
  the level of the sea would be raised at the equator by about 228
  feet, while under the parallel of 52° it would be depressed by
  196 feet. Shallow seas and banks in the latitudes of the British
  isles, and between them and the pole, would thus be converted into
  dry land, while low-lying plains and islands near the equator
  would be submerged. If similar phenomena occurred during early
  periods of geological history, they would manifestly influence the
  distribution of land and water during these periods; and with such
  a direction of the forces as that referred to, they would tend to
  increase the proportion of land in the polar and temperate regions
  of the earth, as compared with the equatorial regions during
  successive geological epochs. Such maps as those published by Sir
  Charles Lyell on the distribution of land and water in Europe
  during the Tertiary period, and those of M. Elie de Beaumont,
  contained in Beaudant’s _Geology_, would, if sufficiently extended,
  assist in verifying or disproving these views.


THE OUTLINES OF CONTINENTS NOT FIXED.

Continents (says M. Agassiz) are only a patchwork formed by the
emergence and subsidence of land. These processes are still going on
in various parts of the globe. Where the shores of the continent are
abrupt and high, the effect produced may be slight, as in Norway and
Sweden, where a gradual elevation is going on without much alteration
in their outlines. But if the continent of North America were to be
depressed 1000 feet, nothing would remain of it except a few islands,
and any elevation would add vast tracts to its shores.

The west of Asia, comprising Palestine and the country about Ararat and
the Caspian Sea, is below the level of the ocean, and a rent in the
mountain-chains by which it is surrounded would transform it into a
vast gulf.




Meteorological Phenomena.


THE ATMOSPHERE.

A philosopher of the East, with a richness of imagery truly oriental,
describes the Atmosphere as “a spherical shell which surrounds our
planet to a depth which is unknown to us, by reason of its growing
tenuity, as it is released from the pressure of its own superincumbent
mass. Its upper surface cannot be nearer to us than 50, and can
scarcely be more remote than 500, miles. It surrounds us on all sides,
yet we see it not; it presses on us with a load of fifteen pounds on
every square inch of surface of our bodies, or from seventy to one
hundred tons on us in all, yet we do not so much as feel its weight.
Softer than the softest down, more impalpable than the finest gossamer,
it leaves the cobweb undisturbed, and scarcely stirs the lightest
flower that feeds on the dew it supplies; yet it bears the fleets of
nations on its wings around the world, and crushes the most refractory
substances with its weight. When in motion, its force is sufficient to
level the most stately forests and stable buildings with the earth--to
raise the waters of the ocean into ridges like mountains, and dash the
strongest ships to pieces like toys. It warms and cools by turns the
earth and the living creatures that inhabit it. It draws up vapours
from the sea and land, retains them dissolved in itself or suspended
in cisterns of clouds, and throws them down again as rain or dew when
they are required. It bends the rays of the sun from their path to
give us the twilight of evening and of dawn; it disperses and refracts
their various tints to beautify the approach and the retreat of the orb
of day. But for the atmosphere sunshine would burst on us and fail us
at once, and at once remove us from midnight darkness to the blaze of
noon. We should have no twilight to soften and beautify the landscape;
no clouds to shade us from the searching heat; but the bald earth, as
it revolved on its axis, would turn its tanned and weakened front to
the full and unmitigated rays of the lord of day. It affords the gas
which vivifies and warms our frames, and receives into itself that
which has been polluted by use and is thrown off as noxious. It feeds
the flames of life exactly as it does that of the fire--it is in both
cases consumed and affords the food of consumption--in both cases it
becomes combined with charcoal, which requires it for combustion and is
removed by it when this is over.”


UNIVERSALITY OF THE ATMOSPHERE.

It is only the girdling, encircling air that flows above and around all
that makes the whole world kin. The carbonic acid with which to-day
our breathing fills the air, to-morrow makes its way round the world.
The date-trees that grow round the falls of the Nile will drink it in
by their leaves; the cedars of Lebanon will take of it to add to their
stature; the cocoa-nuts of Tahiti will grow rapidly upon it; and the
palms and bananas of Japan will change it into flowers. The oxygen we
are breathing was distilled for us some short time ago by the magnolias
of the Susquehanna; the great trees that skirt the Orinoco and the
Amazon, the giant rhododendrons of the Himalayas, contributed to it,
and the roses and myrtles of Cashmere, the cinnamon-tree of Ceylon, and
the forest, older than the Flood, buried deep in the heart of Africa,
far behind the Mountains of the Moon. The rain we see descending was
thawed for us out of the icebergs which have watched the polar star for
ages; and the lotus-lilies have soaked up from the Nile, and exhaled as
vapour, snows that rested on the summits of the Alps.--_North-British
Review._


THE HEIGHT OF THE ATMOSPHERE.

The differences existing between that which appertains to the air
of heaven (the realms of universal space) and that which belongs to
the strata of our terrestrial atmosphere are very striking. It is
not possible, as well-attested facts prove, perfectly to explain
the operations at work in the much-contested upper boundaries of
our atmosphere. The extraordinary lightness of whole nights in the
year 1831, during which small print might be read at midnight in
the latitudes of Italy and the north of Germany, is a fact directly
at variance with all we know according to the researches on the
crepuscular theory and the height of the atmosphere. The phenomena
of light depend upon conditions still less understood; and their
variability at twilight, as well as in the zodiacal light, excite our
astonishment. Yet the atmosphere which surrounds the earth is not
thicker in proportion to the bulk of our globe than the line of a
circle two inches in diameter when compared with the space which it
encloses, or the down on the skin of a peach in comparison with the
fruit inside.


COLOURS OF THE ATMOSPHERE.

Pure air is blue, because, according to Newton, the molecules of the
air have the thickness necessary to reflect blue rays. When the sky
is not perfectly pure, and the atmosphere is blended with perceptible
vapours, the diffused light is mixed with a large proportion of
white. As the moon is yellow, the blue of the air assumes somewhat
of a greenish tinge, or, in other words, becomes blended with
yellow.--_Letter from Arago to Humboldt_; _Cosmos_, vol. iii.


BEAUTY OF TWILIGHT.

This phenomenon is caused by the refraction of solar light enabling
it to diffuse itself gradually over our hemisphere, obscured by the
shades of night, long before the sun appears, even when that luminary
is eighteen degrees below our horizon. It is towards the poles that
this reflected splendour of the great luminary is longest visible,
often changing the whole of the night into a magic day, of which the
inhabitants of southern Europe can form no adequate conception.


HOW PASCAL WEIGHED THE ATMOSPHERE.

Pascal’s treatise on the weight of the whole mass of air forms the
basis of the modern science of Pneumatics. In order to prove that the
mass of air presses by its weight on all the bodies which it surrounds,
and also that it is elastic and compressible, he carried a balloon,
half-filled with air, to the top of the Puy de Dome, a mountain about
500 toises above Clermont, in Auvergne. It gradually inflated itself
as it ascended, and when it reached the summit it was quite full,
and swollen as if fresh air had been blown into it; or, what is the
same thing, it swelled in proportion as the weight of the column of
air which pressed upon it was diminished. When again brought down it
became more and more flaccid, and when it reached the bottom it resumed
its original condition. In the nine chapters of which the treatise
consists, Pascal shows that all the phenomena and effects hitherto
ascribed to the horror of a vacuum arise from the weight of the mass
of air; and after explaining the variable pressure of the atmosphere
in different localities and in its different states, and the rise of
water in pumps, he calculates that the whole mass of air round our
globe weighs 8,983,889,440,000,000,000 French pounds.--_North-British
Review_, No. 2.

It seems probable, from many indications, that the greatest height at
which visible clouds _ever exist_ does not exceed ten miles; at which
height the density of the air is about an eighth part of what it is at
the level of the sea.--_Sir John Herschel._


VARIATIONS OF CLIMATE.

History informs us that many of the countries of Europe which now
possess very mild winters, at one time experienced severe cold during
this season of the year. The Tiber, at Rome, was often frozen over, and
snow at one time lay for forty days in that city. The Euxine Sea was
frozen over every winter during the time of Ovid, and the rivers Rhine
and Rhone used to be frozen over so deep that the ice sustained loaded
wagons. The waters of the Tiber, Rhine, and Rhone, now flow freely
every winter; ice is unknown in Rome, and the waves of the Euxine dash
their wintry foam uncrystallised upon the rocks. Some have ascribed
these climate changes to agriculture--the cutting down of dense
forests, the exposing of the unturned soil to the summer’s sun, and the
draining of great marshes. We do not believe that such great changes
could be produced on the climate of any country by agriculture; and we
are certain that no such theory can account for the contrary change of
climate--from warm to cold winters--which history tells us has taken
place in other countries than those named. Greenland received its name
from the emerald herbage which once clothed its valleys and mountains;
and its east coast, which is now inaccessible on account of perpetual
ice heaped upon its shores, was in the eleventh century the seat of
flourishing Scandinavian colonies, all trace of which is now lost. Cold
Labrador was named Vinland by the Northmen, who visited it A.D. 1000,
and were charmed with its then mild climate. The cause of these changes
is an important inquiry.--_Scientific American._


AVERAGE CLIMATES.

When we consider the numerous and rapid changes which take place in
our climate, it is a remarkable fact, that _the mean temperature of
a place remains nearly the same_. The winter may be unusually cold,
or the summer unusually hot, while the mean temperature has varied
even less than a degree. A very warm summer is therefore likely to
be accompanied with a cold winter; and in general, if we have any
long period of cold weather, we may expect a similar period at a
higher temperature. In general, however, in the same locality the
relative distribution over summer and winter undergoes comparatively
small variations; therefore every point of the globe has an average
climate, though it is occasionally disturbed by different atmospheric
changes.--_North-British Review_, No. 49.


THE FINEST CLIMATE IN THE WORLD.

Humboldt regards the climate of the Caspian Sea as the most salubrious
in the world: here he found the most delicious fruits that he saw
during his travels; and such was the purity of the air, that polished
steel would not tarnish even by night exposure.


THE PUREST ATMOSPHERES.

The cloudless purity and transparency of the atmosphere, which last
for eight months at Santiago, in Chili, are so great, that Lieutenant
Gilliss, with the first telescope ever constructed in America, having
a diameter of seven inches, was clearly able to recognise the sixth
star in the trapezium of Orion. If we are to rely upon the statements
of the Rev. Mr. Stoddart, an American missionary, Oroomiah, in Persia,
seems to be, in so far as regards the transparency of the atmosphere,
the most suitable place in the world for an astronomical observatory.
Writing to Sir John Herschel from that country, he mentions that he
has been enabled to distinguish with the naked eye the satellites
of Jupiter, the crescent of Venus, the rings of Saturn, and the
constituent members of several double stars.


SEA-BREEZES AND LAND-BREEZES ILLUSTRATED.

When a fire is kindled on the hearth, we may, if we will observe the
motes floating in the room, see that those nearest the chimney are the
first to feel the draught and to obey it,--they are drawn into the
blaze. The circle of inflowing air is gradually enlarged, until it is
scarcely perceived in the remote parts of the room. Now the land is the
hearth, the rays of the sun the fire, and the sea, with its cool and
calm air, the room; and thus we have at our firesides the sea-breeze in
miniature.

When the sun goes down, the fire ceases; then the dry land commences
to give off its surplus heat by radiation, so that by nine or ten
o’clock it and the air above it are cooled below the sea temperature.
The atmosphere on the land thus becomes heavier than that on the
sea, and consequently there is a wind seaward, which we call the
land-breeze.--_Maury._


SUPERIOR SALUBRITY OF THE WEST.

All large cities and towns have their best districts in the West;[38]
which choice the French _savans_, Pelouze, Pouillet, Boussingault, and
Elie de Beaumont, attribute to the law of atmospheric pressure. “When,”
say they, “the barometric column rises, smoke and pernicious emanations
rapidly evaporate in space.” On the contrary, smoke and noxious vapours
remain in apartments, and on the surface of the soil. Now, of all
winds, that which causes the greatest ascension of the barometric
column is the east; and that which lowers it most is the west. When the
latter blows, it carries with it to the eastern parts of the town all
the deleterious gases from the west; and thus the inhabitants of the
east have to support their own smoke and miasma, and those brought by
western winds. When, on the contrary, the east wind blows, it purifies
the air by causing to ascend the pernicious emanations which it cannot
drive to the west. Consequently, the inhabitants of the west receive
pure air, from whatever part of the horizon it may arrive; and as the
west winds are most prevalent, they are the first to receive the air
pure, and as it arrives from the country.


FERTILISATION OF CLOUDS.

As the navigator cruises in the Pacific Ocean among the islands of
the trade-wind region, he sees gorgeous piles of cumuli, heaped up in
fleecy masses, not only capping the island hills, but often overhanging
the lowest islet of the tropics, and even standing above coral patches
and hidden reefs; “a cloud by day.” to serve as a beacon to the lonely
mariner out there at sea, and to warn him of shoals and dangers which
no lead nor seaman’s eye has ever seen or sounded. These clouds, under
favourable circumstances, may be seen gathering above the low coral
island, preparing it for vegetation and fruitfulness in a very striking
manner. As they are condensed into showers, one fancies that they are
a sponge of the most exquisite and delicately elaborated material, and
that he can see, as they “drop down their fatness,” the invisible but
bountiful hand aloft that is pressing and squeezing it out.--_Maury._


BAROMETRIC MEASUREMENT.

We must not place too implicit a dependence on Barometrical
Measurements. Ermann in Siberia, and Ross in the Antarctic Seas, have
demonstrated the existence of localities on the earth’s surface where
a permanent depression of the barometer prevails to the astonishing
extent of nearly an inch.


GIGANTIC BAROMETER.

In the Great Exhibition Building of 1851 was a colossal Barometer, the
tube and scale reaching from the floor of the gallery nearly to the top
of the building, and the rise and fall of the indicating fluid being
marked by feet instead of by tenths of inches. The column of mercury,
supported by the pressure of the atmosphere, communicated with a
perpendicular tube of smaller bore, which contained a coloured fluid
much lighter than mercury. When a diminution of atmospheric pressure
occurred, the mercury in the large tube descended, and by its fall
forced up the coloured fluid in the smaller tube; the fall of the one
being indicated in a magnified ratio by the rise in the other.


THE ATMOSPHERE COMPARED TO A STEAM-ENGINE.

In this comparison, by Lieut. Maury, the South Seas themselves, in all
their vast intertropical extent, are the boiler for the engine, and the
northern hemisphere is its condenser. The mechanical power exerted by
the air and the sun in lifting water from the earth, in transporting
it from one place to another, and in letting it down again, is
inconceivably great. The utilitarian who compares the water-power that
the Falls of Niagara would afford if applied to machinery is astonished
at the number of figures which are required to express its equivalent
in horse-power. Yet what is the horse-power of the Niagara, falling
a few steps, in comparison with the horse-power that is required to
lift up as high as the clouds and let down again all the water that is
discharged into the sea, not only by this river, but by all the other
rivers in the world? The calculation has been made by engineers; and
according to it, the force of making and lifting vapour from each area
of one acre that is included on the surface of the earth, is equal to
the power of thirty horses; and for the whole of the earth, it is 800
times greater than all the water-power in Europe.


HOW DOES THE RAIN-MAKING VAPOUR GET FROM THE SOUTHERN INTO THE NORTHERN
HEMISPHERE?

This comes with such regularity, that our rivers never go dry, and
our springs fail not, because of the exact _compensation_ of the
grand machine of _the atmosphere_. It is exquisitely and wonderfully
counterpoised. Late in the autumn of the north, throughout its
winter, and in early spring, the sun is pouring his rays with the
greatest intensity down upon the seas of the southern hemisphere; and
this powerful engine, which we are contemplating, is pumping up the
water there with the greatest activity; at the same time, the mean
temperature of the entire southern hemisphere is about 10° higher than
the northern. The heat which this heavy evaporation absorbs becomes
latent, and with the moisture is carried through the upper regions
of the atmosphere until it reaches our climates. Here the vapour is
formed into clouds, condensed and precipitated; the heat which held
their water in the state of vapour is set free, and becomes sensible
heat; and it is that which contributes so much to temper our winter
climate. It clouds up in winter, turns warm, and we say we are going
to have falling weather: that is because the process of condensation
has already commenced, though no rain or snow may have fallen. Thus we
feel this southern heat, that has been collected by the rays of the sun
by the sea, been bottled away by the winds in the clouds of a southern
summer, and set free in the process of condensation in our northern
winter.

Thus the South Seas should supply mainly the water for the engine just
described, while the northern hemisphere condenses it; we should,
therefore, have more rain in the northern hemisphere. The rivers tell
us that we have, at least on the land; for the great water-courses of
the globe, and half the fresh water in the world, are found on the
north side of the equator. This fact is strongly corroborative of this
hypothesis. To evaporate water enough annually from the ocean to cover
the earth, on the average, five feet deep with rain; to transport it
from one zone to another; and to precipitate it in the right places at
suitable times and in the proportions due,--is one of the offices of
the grand atmospherical machine. This water is evaporated principally
from the torrid zone. Supposing it all to come thence, we shall have
encircling the earth a belt of ocean 3000 miles in breadth, from which
this atmosphere evaporates a layer of water annually sixteen feet in
depth. And to hoist up as high as the clouds, and lower down again,
all the water, in a lake sixteen feet deep and 3000 miles broad and
24,000 long, is the yearly business of this invisible machinery. What a
powerful engine is the atmosphere! and how nicely adjusted must be all
the cogs and wheels and springs and _compensations_ of this exquisite
piece of machinery, that it never wears out nor breaks down, nor fails
to do its work at the right time and in the right way!--_Maury._


THE PHILOSOPHY OF RAIN.

To understand the philosophy of this beautiful and often sublime
phenomenon, a few facts derived from observation and a long train of
experiments must be remembered.

  1. Were the atmosphere every where at all times at a uniform
  temperature, we should never have rain, or hail, or snow. The water
  absorbed by it in evaporation from the sea and the earth’s surface
  would descend in an imperceptible vapour, or cease to be absorbed
  by the air when it was once fully saturated.

  2. The absorbing power of the atmosphere, and consequently its
  capability to retain humidity, is proportionally greater in warm
  than in cold air.

  3. The air near the surface of the earth is warmer than it is in
  the region of the clouds. The higher we ascend from the earth, the
  colder do we find the atmosphere. Hence the perpetual snow on very
  high mountains in the hottest climate.

Now when, from continued evaporation, the air is highly saturated
with vapour, though it be invisible and the sky cloudless, if its
temperature is suddenly reduced by cold currents descending from
above or rushing from a higher to a lower latitude, its capacity to
retain moisture is diminished, clouds are formed, and the result is
rain. Air condenses as it cools, and, like a sponge filled with water
and compressed, pours out the water which its diminished capacity
cannot hold. What but Omniscience could have devised such an admirable
arrangement for watering the earth?


INORDINATE RAINY CLIMATE.

The climate of the Khasia mountains, which lie north-east from
Calcutta, and are separated by the valley of the Burrampooter River
from the Himalaya range, is remarkable for the inordinate fall of
rain--the greatest, it is said, which has ever been recorded. Mr. Yule,
an English gentleman, established that in the single month of August
1841 there fell 264 inches of rain, or 22 feet, of which 12½ feet
fell in the space of five consecutive days. This astonishing fact is
confirmed by two other English travellers, who measured 30 inches of
rain in twenty-four hours, and during seven months above 500 inches.
This great rain-fall is attributed to the abruptness of the mountains
which face the Bay of Bengal, and the intervening flat swamps 200 miles
in extent. The district of the excessive rain is extremely limited; and
but a few degrees farther west, rain is said to be almost unknown, and
the winter falls of snow to seldom exceed two inches.


HOW DOES THE NORTH WIND DRIVE AWAY RAIN?

We may liken it to a wet sponge, and the decrease of temperature
to the hand that squeezes that sponge. Finally, reaching the cold
latitudes, all the moisture that a dew-point of zero, and even far
below, can extract, is wrung from it; and this air then commences “to
return according to his circuits” as dry atmosphere. And here we can
quote Scripture again: “The north wind driveth away rain.” This is a
meteorological fact of high authority and great importance in the study
of the circulation of the atmosphere.--_Maury._


SIZE OF RAIN-DROPS.

The Drops of Rain vary in their size, perhaps from the 25th to the ¼ of
an inch in diameter. In parting from the clouds, they precipitate their
descent till the increasing resistance opposed by the air becomes equal
to their weight, when they continue to fall with uniform velocity. This
velocity is, therefore, in a certain ratio to the diameter of the
drops; hence thunder and other showers in which the drops are large
pour down faster than a drizzling rain. A drop of the 25th part of an
inch, in falling through the air, would, when it had arrived at its
uniform velocity, only acquire a celerity of 11½ feet per second; while
one of ¼ of an inch would equal a velocity of 33½ feet.--_Leslie._


RAINLESS DISTRICTS.

In several parts of the world there is no rain at all. In the Old World
there are two districts of this kind: the desert of Sahara in Africa,
and in Asia part of Arabia, Syria, and Persia; the other district lies
between north latitude 30° and 50°, and between 75° and 118° of east
longitude, including Thibet, Gobiar Shama, and Mongolia. In the New
World the rainless districts are of much less magnitude, occupying two
narrow strips on the shores of Peru and Bolivia, and on the coast of
Mexico and Guatemala, with a small district between Trinidad and Panama
on the coast of Venezuela.


ALL THE RAIN IN THE WORLD.

The Pacific Ocean and the Indian Ocean may be considered as one sheet
of water covering an area quite equal in extent to one half of that
embraced by the whole surface of the earth; and the total annual fall
of rain on the earth’s surface is 186,240 cubic imperial miles. Not
less than three-fourths of the vapour which makes this rain comes from
this waste of waters; but, supposing that only half of this quantity,
that is 93,120 cubic miles of rain, falls upon this sea, and that that
much at least is taken up from it again as vapour, this would give
255 cubic miles as the quantity of water which is daily lifted up and
poured back again into this expanse. It is taken up at one place,
and rained down at another; and in this process, therefore, we have
agencies for multitudes of partial and conflicting currents, all, in
their set strength, apparently as uncertain as the winds.

The better to appreciate the operation of such agencies in producing
currents in the sea, imagine a district of 255 square miles to be set
apart in the midst of the Pacific Ocean as the scene of operations
for one day; then conceive a machine capable of pumping up in the
twenty-four hours all the water to the depth of one mile in this
district. The machine must not only pump up and bear off this immense
quantity of water, but it must discharge it again into the sea on the
same day, but at some other place.

All the great rivers of America, Europe, and Asia are lifted up by the
atmosphere, and flow in invisible streams back through the air to their
sources among the hills; and through channels so regular, certain, and
well defined, that the quantity thus conveyed one year with the other
is nearly the same: for that is the quantity which we see running down
to the ocean through these rivers; and the quantity discharged annually
by each river is, as far as we can judge, nearly a constant.--_Maury._


AN INCH OF RAIN ON THE ATLANTIC.

Lieutenant Maury thus computes the effect of a single Inch of Rain
falling upon the Atlantic Ocean. The Atlantic includes an area of
twenty-five millions of square miles. Suppose an inch of rain to fall
upon only one-fifth of this vast expanse. It would weigh, says our
author, three hundred and sixty thousand millions of tons: and the salt
which, as water, it held in solution in the sea, and which, when that
water was taken up as vapour, was left behind to disturb equilibrium,
weighed sixteen millions more of tons, or nearly twice as much as all
the ships in the world could carry at a cargo each. It might fall in
an hour, or it might fall in a day; but, occupy what time it might
in falling, this rain is calculated to exert so much force--which is
inconceivably great--in disturbing the equilibrium of the ocean. If
all the water discharged by the Mississippi river during the year were
taken up in one mighty measure, and cast into the ocean at one effort,
it would not make a greater disturbance in the equilibrium of the
sea than would the fall of rain supposed. And yet so gentle are the
operations of nature, that movements so vast are unperceived.


THE EQUATORIAL CLOUD-RING.

In crossing the Equatorial Doldrums, the voyager passes a ring of
clouds that encircles the earth, and is stretched around our planet
to regulate the quantity of precipitation in the rain-belt beneath
it; to preserve the due quantum of heat on the face of the earth; to
adjust the winds; and send out for distribution to the four corners
vapours in proper quantities, to make up to each river-basin, climate,
and season, its quota of sunshine, cloud, and moisture. Like the
balance-wheel of a well-constructed chronometer, this cloud-ring
affords the grand atmospherical machine the most exquisitely arranged
_self-compensation_. Nature herself has hung a thermometer under this
cloud-belt that is more perfect than any that man can construct, and
its indications are not to be mistaken.--_Maury._


“THE EQUATORIAL DOLDRUMS”

is another of these calm places. Besides being a region of calms and
baffling winds, it is a region noted for its rains and clouds, which
make it one of the most oppressive and disagreeable places at sea. The
emigrant ships from Europe for Australia have to cross it. They are
often baffled in it for two or three weeks; then the children and the
passengers who are of delicate health suffer most. It is a frightful
graveyard on the wayside to that golden land.


BEAUTY OF THE DEW-DROP.

The Dew-drop is familiar to every one from earliest infancy. Resting
in luminous beads on the down of leaves, or pendent from the finest
blades of grass, or threaded upon the floating lines of the gossamer,
its “orient pearl” varies in size from the diameter of a small pea to
the most minute atom that can be imagined to exist. Each of these, like
the rain-drops, has the properties of reflecting and refracting light;
hence, from so many minute prisms, the unfolded rays of the sun are
sent up to the eye in colours of brilliancy similar to those of the
rainbow. When the sunbeams traverse horizontally a very thickly-bedewed
grass-plot, these colours arrange themselves so as to form an iris,
or dew-bow; and if we select any one of these drops for observation,
and steadily regard it while we gradually change our position, we
shall find the prismatic colours follow each other in their regular
order.--_Wells._


FALL OF DEW IN ONE YEAR.

The annual average quantity of Dew deposited in this country is
estimated at a depth of about five inches, being about one-seventh
of the mean quantity of moisture supposed to be received from the
atmosphere all over Great Britain in the year; or about 22,161,337,355
tons, taking the ton at 252 imperial gallons.--_Wells._


GRADUATED SUPPLY OF DEW TO VEGETATION.

Each of the different grasses draws from the atmosphere during the
night a supply of dew to recruit its energies dependent upon its form
and peculiar radiating power. Every flower has a power of radiation
of its own, subject to changes during the day and night, and the
deposition of moisture on it is regulated by the peculiar law which
this radiating power obeys; and this power will be influenced by
the aspect which the flower presents to the sky, unfolding to the
contemplative mind the most beautiful example of creative wisdom.[39]


WARMTH OF SNOW IN ARCTIC LATITUDES.

The first warm Snows of August and September (says Dr. Kane), falling
on a thickly-bleached carpet of grasses, heaths, and willows, enshrine
the flowery growths which nestle round them in a non-conducting air
chamber; and as each successive snow increases the thickness of the
cover, we have, before the intense cold of winter sets in, a light
cellular bed covered by drift, seven, eight, or ten feet deep, in which
the plant retains its vitality. Dr. Kane has proved by experiments that
the conducting power of the snow is proportioned to its compression
by winds, rains, drifts, and congelation. The drifts that accumulate
during nine months of the year are dispersed in well-defined layers
of different density. We have first the warm cellular snows of fall,
which surround the plant; next the finely-impacted snow-dust of winter;
and above these the later humid deposits of spring. In the earlier
summer, in the inclined slopes that face the sun, as the upper snow is
melted and sinks upon the more compact layer below it is to a great
extent arrested, and runs off like rain from a slope of clay. The plant
reposes thus in its cellular bed, safe from the rush of waters, and
protected from the nightly frosts by the icy roof above it.


IMPURITY OF SNOW.

It is believed that in ascending mountains difficult breathing is
sooner felt upon snow than upon rock; and M. Boussingault, in his
account of the ascent of Chimborazo, attributes this to the sensible
deficiency of oxygen contained in the pores of the snow, which is
exhaled when it melts. The fact that the air absorbed by snow is
impure, was ascertained by De Saussure, and has been confirmed by
Boussingault’s experiments.--_Quarterly Review_, No. 202.


SNOW PHENOMENON.

Professor Dove of Berlin relates, in illustration of the formation of
clouds of Snow over plains situated at a distance from the cooling
summits of mountains, that on one occasion a large company had gathered
in a ballroom in Sweden. It was one of those icy starlight nights
which in that country are so aptly called “iron nights.” The weather
was clear and cold, and the ballroom was clear and warm; and the heat
was so great, that several ladies fainted. An officer present tried to
open a window; but it was frozen fast to the sill. As a last resort, he
broke a pane of glass; the cold air rushed in, and it _snowed in the
room_. A minute before all was clear; but the warm air of the room had
sustained an amount of moisture in a transparent condition which it was
not able to maintain when mixed with the colder air from without. The
vapour was first condensed, and then frozen.


ABSENCE OF SNOW IN SIBERIA.

There is in Siberia, M. Ermann informs us, an _entire district_ in
which during the winter the sky is constantly clear, and where a single
particle of snow never falls.--_Arago._


ACCURACY OF THE CHINESE AS OBSERVERS.

The beautiful forms of snow-crystals have long since attracted Chinese
observers; for from a remote period there has been met with in their
conversation and books an axiomatic expression, to the effect that
“snow-flakes are hexagonal,” showing the Chinese to be accurate
observers of nature.


PROTECTION AGAINST HAIL AND STORMS.

Arago relates, that when, in 1847, two small agricultural districts
of Bourgoyne had lost by Hail crops to the value of a million and a
half of francs, certain of the proprietors went to consult him on the
means of protecting them from like disasters. Resting on the hypothesis
of the electric origin of hail, Arago suggested the discharge of
the electricity of the clouds by means of balloons communicating by
a metallic wire with the soil. This project was not carried out;
but Arago persisted in believing in the effectiveness of the method
proposed.

  Arago, in his _Meteorological Essays_, inquires whether the firing
  of cannon can dissipate storms. He cites several cases in its
  favour, and others which seem to oppose it; but he concludes by
  recommending it to his successors. Whilst Arago was propounding
  these questions, a person not conversant with science, the poet
  Méry, was collecting facts supporting the view, which he has
  published in his _Paris Futur_. His attention was attracted to the
  firing of cannon to dissipate storms in 1828, whilst an assistant
  in the “Ecole de Tir” at Vincennes. Having observed that there was
  never any rain in the morning of the exercise of firing, he waited
  to examine military records, and found there, as he says, facts
  which justified the expressions of “Le soleil d’Austerlitz,” “Le
  soleil de juillet,” upon the morning of the Revolution of July;
  and he concluded by proposing to construct around Paris twelve
  towers of great height, which he calls “tours imbrifuges,” each
  carrying 100 cannons, which should be discharged into the air on
  the approach of a storm. About this time an incident occurred which
  in nowise confirmed the truth of M. Méry’s theory. The 14th of
  August was a fine day. On the 15th, the fête of the Empire, the
  sun shone out, the cannon thundered all day long, fireworks and
  illuminations were blazing from nine o’clock in the evening. Every
  thing conspired to verify the hypothesis of M. Méry, and chase
  away storms for a long time. But towards eleven in the evening
  a torrent of rain burst upon Paris, in spite of the pretended
  influence of the discharge of cannon, and gave an occasion for the
  mobile Gallic mind to turn its attention in other directions.


TERRIFIC HAILSTORM.

Jansen describes, from the log-book of the _Rhijin_, Captain Brandligt,
in the South-Indian Ocean (25° south latitude) a Hurricane, accompanied
by Hail, by which several of the crew were made blind, others had their
faces cut open, and those who were in the rigging had their clothes
torn off them. The master of the ship compared the sea “to a hilly
landscape in winter covered with snow.” Does it not appear as if the
“treasures of the hail” were opened, which were “reserved against the
time of trouble, against the day of battle and war”?


HOW WATERSPOUTS ARE FORMED IN THE JAVA SEA.

Among the small groups of islands in this sea, in the day and night
thunderstorms, the combat of the clouds appears to make them more
thirsty than ever. In tunnel form, when they can no longer quench their
thirst from the surrounding atmosphere, they descend near the surface
of the sea, and appear to lap the water directly up with their black
mouths. They are not always accompanied by strong winds; frequently
more than one is seen at a time, whereupon the clouds whence they
proceed disperse, and the ends of the Waterspouts bending over finally
causes them to break in the middle. They seldom last longer than five
minutes. As they are going away, the bulbous tube, which is as palpable
as that of a thermometer, becomes broader at the base; and little
clouds, like steam from the pipe of a locomotive, are continually
thrown off from the circumference of the spout, and gradually the water
is released, and the cloud whence the spout came again closes its mouth.


COLD IN HUDSON’S BAY.

Mr. R. M. Ballantyne, in his journal of six years’ residence in the
territories of the Hudson’s Bay Company, tells us, that for part of
October there is sometimes a little warm, or rather thawy, weather; but
after that, until the following April, the thermometer seldom rises
to the freezing point. In the depth of winter, the thermometer falls
from 30° to 40°, 45°, and even 49° _below zero_ of Fahrenheit. This
intense cold is not, however, so much felt as one might suppose; for
during its continuance the air is perfectly calm. Were the slightest
breath of wind to rise when the thermometer stands so low, no man could
show his face to it for a moment. Forty degrees below zero, and quite
calm, is infinitely preferable to fifteen below, or thereabout, with
a strong breeze of wind. Spirit of wine is, of course, the only thing
that can be used in the thermometer; as mercury, were it exposed to
such cold, would remain frozen nearly half the winter. Spirit never
froze in any cold ever experienced at York Factory, unless when very
much adulterated with water; and even then the spirit would remain
liquid in the centre of the mass. Quicksilver easily freezes in this
climate, and it has frequently been run into a bullet-mould, exposed to
the cold air till frozen, and in this state rammed down a gun-barrel,
and fired through a thick plank. The average cold may be set down at
about 15° or 16° below zero, or 48° of frost. The houses at the Bay are
built of wood, with double windows and doors. They are heated by large
iron stoves, fed with wood; yet so intense is the cold, that when a
stove has been in places red-hot, a basin of water in the room has been
frozen solid.


PURITY OF WENHAM-LAKE ICE.

Professor Faraday attributes the purity of Wenham-Lake Ice to its being
free from air-bubbles and from salts. The presence of the first makes
it extremely difficult to succeed in making a lens of English ice which
will concentrate the solar rays, and readily fire gunpowder; whereas
nothing is easier than to perform this singular feat of igniting
a combustible body by aid of a frozen mass if Wenham-Lake ice be
employed. The absence of salts conduces greatly to the permanence of
the ice; for where water is so frozen that the salts expelled are still
contained in air-cavities and cracks, or form thin films between the
layers of ice, these entangled salts cause the ice to melt at a lower
temperature than 32°, and the liquefied portions give rise to streams
and currents within the body of the ice which rapidly carry heat to the
interior. The mass then goes on thawing within as well as without, and
at temperatures below 32°; whereas pure, compact, Wenham-Lake ice can
only thaw at 32°, and only on the outside of the mass.--_Sir Charles
Lyell’s Second Visit to the United States._


ARCTIC TEMPERATURES.

Dr. Kane, in his Second Arctic Expedition, found the thermometers
beginning to show unexampled temperature: they ranged from 60° to 70°
below zero, and upon the taffrail of the brig 65°. The reduced mean of
the best spirit-standards gave 67° or 99° below the freezing point of
water. At these temperatures chloric ether became solid, and chloroform
exhibited a granular pellicle on its surface. Spirit of naphtha froze
at 54°, and the oil of turpentine was solid at 63° and 65°.


DR. RAE’S ARCTIC EXPLORATIONS.

The gold medal of the Royal Geographical Society was in 1852 most
rightfully awarded to this indefatigable Arctic explorer. His survey of
the inlet of Boothia, in 1848, was unique in its kind. In Repulse Bay
he maintained his party on deer, principally shot by himself; and spent
ten months of an Arctic winter in a hut of stones, with no other fuel
than a kind of hay of the _Andromeda tetragona_. Thus he preserved his
men to execute surveying journeys of 1000 miles in the spring. Later he
travelled 300 miles on snow-shoes. In a spring journey over the ice,
with a pound of fat daily for fuel, accompanied by two men only, and
trusting solely for shelter to snow-houses, which he taught his men to
build, he accomplished 1060 miles in thirty-nine days, or twenty-seven
miles per day, including stoppages,--a feat never equalled in Arctic
travelling. In the spring journey, and that which followed in the
summer in boats, 1700 miles were traversed in eighty days. Dr. Rae’s
greatest sufferings, he once remarked to Sir George Back, arose from
his being obliged to sleep upon his frozen mocassins in order to thaw
them for the morning’s use.


PHENOMENA OF THE ARCTIC CLIMATE.

Sir John Richardson, in his history of his Expedition to these regions,
describes the power of the sun in a cloudless sky to have been so
great, that he was glad to take shelter in the water while the crews
were engaged on the portages; and he has never felt the direct rays of
the sun so oppressive as on some occasions in the high latitudes. Sir
John observes:

  The rapid evaporation of both snow and ice in the winter and
  spring, long before the action of the sun has produced the
  slightest thaw or appearance of moisture, is evident by many
  facts of daily occurrence. Thus when a shirt, after being washed,
  is exposed in the open air to a temperature of from 40° to 50°
  below zero, it is instantly rigidly frozen, and may be broken if
  violently bent. If agitated when in this condition by a strong
  wind, it makes a rustling noise like theatrical thunder.

  In consequence of the extreme dryness of the atmosphere in winter,
  most articles of English manufacture brought to Rupert’s Land are
  shrivelled, bent, and broken. The handles of razors and knives,
  combs, ivory scales, &c., kept in the warm room, are changed in
  this way. The human body also becomes vividly electric from the
  dryness of the skin. One cold night I rose from my bed, and was
  going out to observe the thermometer, with no other clothing than
  my flannel night-dress, when on my hand approaching the iron latch
  of the door, a distinct spark was elicited. Friction of the skin at
  almost all times in winter produced the electric odour.

  Even at midwinter we had but three hours and a half of daylight.
  On December 20th I required a candle to write at the window at ten
  in the morning. The sun was absent ten days, and its place in the
  heavens at noon was denoted by rays of light shooting into the sky
  above the woods.

  The moon in the long nights was a most beautiful object, that
  satellite being constantly above the horizon for nearly a fortnight
  together. Venus also shone with a brilliancy which is never
  witnessed in a sky loaded with vapours; and, unless in snowy
  weather, our nights were always enlivened by the beams of the
  aurora.


INTENSE HEAT AND COLD OF THE DESERT.

Among crystalline bodies, rock-crystal, or silica, is the best
conductor of heat. This fact accounts for the steadiness of temperature
in one set district, and the extremes of Heat and Cold presented by
day and night on such sandy wastes as the Sahara. The sand, which is
for the most part silica, drinks-in the noon-day heat, and loses it by
night just as speedily.

The influence of the hot winds from the Sahara has been observed
in vessels traversing the Atlantic at a distance of upwards of
1100 geographical miles from the African shores, by the coating of
impalpable dust upon the sails.


TRANSPORTING POWER OF WINDS.

The greatest example of their power is the _sand-flood_ of Africa,
which, moving gradually eastward, has overwhelmed all the land capable
of tillage west of the Nile, unless sheltered by high mountains, and
threatens ultimately to obliterate the rich plain of Egypt.


EXHILARATION IN ASCENDING MOUNTAINS.

At all elevations of from 6000 to 11,000 feet, and not unfrequently
for even 2000 feet more, the pedestrian enjoys a pleasurable feeling,
imparted by the consciousness of existence, similar to that which is
described as so fascinating by those who have become familiar with the
desert-life of the East. The body seems lighter, the nervous power
greater, the appetite is increased; and fatigue, though felt for a
time, is removed by the shortest repose. Some travellers have described
the sensation by the impression that they do not actually press the
ground, but that the blade of a knife could be inserted between the
sole of the foot and the mountain top.--_Quarterly Review_, No. 202.


TO TELL THE APPROACH OF STORMS.

The proximity of Storms has been ascertained with accuracy by
various indications of the electrical state of the atmosphere. Thus
Professor Scott, of Sandhurst College, observed in Shetland that
drinking-glasses, placed in an inverted position upon a shelf in a
cupboard on the ground-floor of Belmont House, occasionally emitted
sounds as if they were tapped with a knife, or raised a little and
then let fall on the shelf. These sounds preceded wind; and when they
occurred, boats and vessels were immediately secured. The strength of
the sound is said to be proportioned to the tempest that follows.


REVOLVING STORMS.

By the conjoint labours of Mr. Redfield, Colonel Reid, and Mr.
Piddington, on the origin and nature of hurricanes, typhoons, or
revolving storms, the following important results have been obtained.
Their existence in moderate latitudes on both sides the equator; their
absence in the immediate neighbourhood of the equatorial regions; and
the fact, that while in the northern latitudes these storms revolve
in a direction contrary to the hands of a watch the face of which is
placed upwards, in the southern latitudes they rotate in the opposite
direction,--are shown to be so many additions to the long chain of
evidence by which the rotation of the earth as a physical fact is
demonstrated.


IMPETUS OF A STORM.

Captain Sir S. Brown estimates, from experiments made by him at the
extremity of the Brighton-Chain Pier in a heavy south-west gale, that
the waves impinge on a cylindrical surface one foot high and one foot
in diameter with a force equal to eighty pounds, to which must be added
that of the wind, which in a violent storm exerts a pressure of forty
pounds. He computed the collective impetus of the waves on the lower
part of a lighthouse proposed to be built on the Wolf Rock (exposed
to the most violent storms of the Atlantic), of the surf on the upper
part, and of the wind on the whole, to be equal to 100 tons.


HOW TO MAKE A STORM-GLASS.

This instrument consists of a glass tube, sealed at one end, and
furnished with a brass cap at the other end, through which the air
is admitted by a very small aperture. Nearly fill the tube with the
following solution: camphor, 2½ drams; nitrate of potash, 38 grains;
muriate of ammonia, 38 grains; water, 9 drams; rectified spirit,
9 drams. Dissolve with heat. At the ordinary temperature of the
atmosphere, plumose crystals are formed. On the approach of stormy
weather, these crystals appear compressed into a compact mass at the
bottom of the tube; while during fine weather they assume their plumose
character, and extend a considerable way up the glass. These results
depend upon the condition of the air, but they are not considered to
afford any reliable indication of approaching weather.


SPLENDOUR OF THE AURORA BOREALIS.

Humboldt thus beautifully describes this phenomenon:

  The intensity of this light is at times so great, that Lowenörn
  (on June 29, 1786) recognised its coruscation in bright sunshine.
  Motion renders the phenomenon more visible. Round the point in
  the vault of heaven which corresponds to the direction of the
  inclination of the needle the beams unite together to form the
  so-called corona, the crown of the Northern Light, which encircles
  the summit of the heavenly canopy with a milder radiance and
  unflickering emanations of light. It is only in rare instances that
  a perfect crown or circle is formed; but on its completion, the
  phenomenon has invariably reached its maximum, and the radiations
  become less frequent, shorter, and more colourless. The crown, and
  the luminous arches break up; and the whole vault of heaven becomes
  covered with irregularly scattered, broad, faint, almost ashy-gray,
  luminous, immovable patches, which in their turn disappear, leaving
  nothing but a trace of a dark smoke-like segment on the horizon.
  There often remains nothing of the whole spectacle but a white
  delicate cloud with feathery edges, or divided at equal distances
  into small roundish groups like cirro-cumuli.--_Cosmos_, vol. i.

Among many theories of this phenomenon is that of Lieutenant Hooper,
R.N., who has stated to the British Association that he believes “the
Aurora Borealis to be no more nor less than the moisture in some
shape (whether dew or vapour, liquid or frozen), illuminated by the
heavenly bodies, either directly, or reflecting their rays from the
frozen masses around the Pole, or even from the immediately proximate
snow-clad earth.”


VARIETIES OF LIGHTNING.

According to Arago’s investigations, the evolution of Lightning is of
three kinds: zigzag, and sharply defined at the edges; in sheets of
light, illuminating a whole cloud, which seems to open and reveal the
light within it; and in the form of fire-balls. The duration of the
first two kinds scarcely continues the thousandth part of a second; but
the globular lightning moves much more slowly, remaining visible for
several seconds.


WHAT IS SHEET-LIGHTNING?

This electric phenomenon is unaccompanied by thunder, or too distant to
be heard: when it appears, the whole sky, but particularly the horizon,
is suddenly illuminated with a flickering flash. Philosophers differ
much as to its cause. Matteucci supposes it to be produced either
during evaporation, or evolved (according to Pouillet’s theory) in the
process of vegetation; or generated by chemical action in the great
laboratory of nature, the earth, and accumulated in the lower strata of
the air in consequence of the ground being an imperfect conductor.

  Arago and Kamtz, however, consider sheet-lightning as _reflections
  of distant thunderstorms_. Saussure observed sheet-lightning in the
  direction of Geneva, from the Hospice du Grimsel, on the 10th and
  11th of July 1783; while at the same time a terrific thunderstorm
  raged at Geneva. Howard, from Tottenham, near London, on July 31,
  1813, saw sheet-lightning towards the south-east, while the sky was
  bespangled with stars, not a cloud floating in the air; at the same
  time a thunderstorm raged at Hastings, and in France from Calais
  to Dunkirk. Arago supports his opinion, that the phenomenon is
  _reflected lightning_, by the following illustration: In 1803, when
  observations were being made for determining the longitude, M. de
  Zach, on the Brocken, used a few ounces of gunpowder as a signal,
  the flash of which was visible from the Klenlenberg, sixty leagues
  off, although these mountains are invisible from each other.


PRODUCTION OF LIGHTNING BY RAIN.

A sudden gust of rain is almost sure to succeed a violent detonation
immediately overhead. Mr. Birt, the meteorologist, asks: Is this rain a
_cause_ or _consequence_ of the electric discharge? To this he replies:

  In the sudden agglomeration of many minute and feebly electrified
  globules into one rain-drop, the quantity of electricity is
  increased in a greater proportion than the surface over which
  (according to the laws of electric distribution) it is spread. By
  tension, therefore, it is increased, and may attain the point when
  it is capable of separating from the _drop_ to seek the surface of
  the _cloud_, or of the newly-formed descending body of rain, which,
  under such circumstances, may be regarded as a conducting medium.
  Arrived at this surface, the tension, for the same reason, becomes
  enormous, and a flash escapes. This theory Mr. Birt has confirmed
  by observation of rain in thunderstorms.


SERVICE OF LIGHTNING-CONDUCTORS.

Sir David Brewster relates a remarkable instance of a tree in
Clandeboye Park, in a thick mass of wood, and _not the tallest of the
group_, being struck by lightning, which passed down the trunk into
the ground, rending the tree asunder. This shows that an object may be
struck by lightning in a locality where there are numerous conducting
points more elevated than itself; and at the same time proves that
lightning cannot be diverted from its course by lofty isolated
conductors, but that the protection of buildings from this species
of meteor can only be effected by conductors stretching out in all
directions.

Professor Silliman states, that lightning-rods cannot be relied upon
unless they reach the earth where it is permanently wet; and that the
best security is afforded by carrying the rod, or some good metallic
conductor duly connected with it, to the water in the well, or to some
other water that never fails. The professor’s house, it seems, was
struck; but his lightning-rods were not more than two or three inches
in the ground, and were therefore virtually of no avail in protecting
the building.


ANCIENT LIGHTNING-CONDUCTOR.

Humboldt informs us, that “the most important ancient notice of the
relations between lightning and conducting metals is that of Ctesias,
in his _Indica_, cap. iv. p. 190. He possessed two iron swords,
presents from the king Artaxerxes Mnemon and from his mother Parasytis,
which, when planted in the earth, averted clouds, hail, and _strokes of
lightning_. He had himself seen the operation, for the king had twice
made the experiment before his eyes.”--_Cosmos_, vol. ii.


THE TEMPLE OF JERUSALEM PROTECTED FROM LIGHTNING.

We do not learn, either from the Bible or Josephus, that the Temple
at Jerusalem was ever struck by Lightning during an interval of more
than a thousand years, from the time of Solomon to the year 70;
although, from its situation, it was completely exposed to the violent
thunderstorms of Palestine.

By a fortuitous circumstance, the Temple was crowned with
lightning-conductors similar to those which we now employ, and which
we owe to Franklin’s discovery. The roof, constructed in what we call
the Italian manner, and covered with boards of cedar, having a thick
coating of gold, was garnished from end to end with long pointed and
gilt iron or steel lances, which, Josephus says, were intended to
prevent birds from roosting on the roof and soiling it. The walls
were overlaid throughout with wood, thickly gilt. Lastly, there
were in the courts of the Temple cisterns, into which the rain from
the roof was conducted by _metallic pipes_. We have here both the
lightning-rods and a means of conduction so abundant, that Lichtenberg
is quite right in saying that many of the present apparatuses are far
from offering in their construction so satisfactory a combination of
circumstances.--_Abridged from Arago’s Meteorological Essays._


HOW ST. PAUL’S CATHEDRAL IS PROTECTED FROM LIGHTNING.

In March 1769, the Dean and Chapter of St. Paul’s addressed a letter
to the Royal Society, requesting their opinion as to the best and most
effectual method of fixing electrical conductors on the cathedral. A
committee was formed for the purpose, and Benjamin Franklin was one of
the members; their report was made, and the conductors were fixed as
follows:

  The seven iron scrolls supporting the ball and cross are connected
  with other rods (used merely as conductors), which unite them
  with several large bars, descending obliquely to the stone-work
  of the lantern, and connected by an iron ring with four other
  iron bars to the lead covering of the great cupola, a distance
  of forty-eight feet; thence the communication is continued by
  the rain-water pipes to the lead-covered roof, and thence by lead
  water-pipes which pass into the earth; thus completing the entire
  communication from the cross to the ground, partly through iron,
  and partly through lead. On the clock-tower a bar of iron connects
  the pine-apple at the top with the iron staircase, and thence with
  the lead on the roof of the church. The bell-tower is similarly
  protected. By these means the metal used in the building is made
  available as conductors; the metal employed merely for that purpose
  being exceedingly small in quantity.--_Curiosities of London._


VARIOUS EFFECTS OF LIGHTNING.

Dr. Hibbert tells us that upon the western coast of Scotland and
Ireland, Lightning coöperates with the violence of the storm in
shattering solid rocks, and heaping them in piles of enormous
fragments, both on dry land and beneath the water.

Euler informs us, in his _Letters to a German Princess_, that he
corresponded with a Moravian priest named Divisch, who assured him
that he had averted during a whole summer every thunderstorm which
threatened his own habitation and the neighbourhood, by means of a
machine constructed upon the principles of electricity; that the
machinery sensibly attracted the clouds, and constrained them to
descend quietly in a distillation, without any but a very distant
thunderclap. Euler assures us that “the fact is undoubted, and
confirmed by irresistible proof.”

About the year 1811, in the village of Phillipsthal, in Eastern
Prussia, an attempt was made to split an immense stone into a multitude
of pieces by means of lightning. A bar of iron, in the form of a
conductor, was previously fixed to the stone; and the experiment was
attended with complete success; for during the very first thunderstorm
the lightning burst the stone without displacing it.

The celebrated Duhamel du Monceau says, that lightning, unaccompanied
by thunder, wind, or rain, has the property of breaking oat-stalks. The
farmers are acquainted with this effect, and say that the lightning
breaks down the oats. This is a well-received opinion with the farmers
in Devonshire.

Lightning has in some cases the property of reducing solid bodies to
ashes, or to pulverisation,--even the human body,--without there being
any signs of heat. The effects of lightning on paralysis are very
remarkable, in some cases curing, in others causing, that disease.

The returning stroke of lightning is well known to be due to the
restoration of the natural electric state, after it has been disturbed
by induction.


A THUNDERSTORM SEEN FROM A BALLOON.

Mr. John West, the American aeronaut, in his observations made during
his numerous ascents, describes a storm viewed from above the clouds
to have the appearance of ebullition. The bulging upper surface of the
cloud resembles a vast sea of boiling and upheaving snow; the noise
of the falling rain is like that of a waterfall over a precipice; the
thunder above the cloud is not loud, and the flashes of lightning
appear like streaks of intensely white fire on a surface of white
vapour. He thus describes a side view of a storm which he witnessed
June 3, 1852, in his balloon excursion from Portsmouth, Ohio:

  Although the sun was shining on me, the rain and small hail were
  rattling on the balloon. A rainbow, or prismatically-coloured arch
  or horse-shoe, was reflected against the sun; and as the point of
  observation changed laterally and perpendicularly, the perspective
  of this golden grotto changed its hues and forms. Above and behind
  this arch was going on the most terrific thunder; but no zigzag
  lightning was perceptible, only bright flashes, like explosions
  of “Roman candles” in fireworks. Occasionally there was a zigzag
  explosion in the cloud immediately below, the thunder sounding like
  a _feu-de-joie_ of a rifle-corps. Then an orange-coloured wave of
  light seemed to fall from the upper to the lower cloud; this was
  “still-lightning.” Meanwhile intense electrical action was going
  on _in the balloon_, such as expansion, tremulous tension, lifting
  papers ten feet out of the car below the balloon and then dropping
  them, &c. The close view of this Ohio storm was truly sublime; its
  rushing noise almost appalling.

Ascending from the earth with a balloon, in the rear of a storm, and
mounted up a thousand feet above it, the balloon will soon override the
storm, and may descend in advance of it. Mr. West has experienced this
several times.


REMARKABLE AERONAUTIC VOYAGE.

Mr. Sadler, the celebrated aeronaut, ascended on one occasion in a
balloon from Dublin, and was wafted across the Irish Channel; when,
on his approach to the Welsh coast, the balloon descended nearly to
the surface of the sea. By this time the sun was set, and the shades
of evening began to close in. He threw out nearly all his ballast,
and suddenly sprang upward to a great height; and by so doing brought
his horizon to _dip_ below the sun, producing the whole phenomenon
of a western sunrise. Subsequently descending in Wales, he of course
witnessed a second sunset on the same evening.--_Sir John Herschel’s
Outlines of Astronomy._




Physical Geography of the Sea.[40]


CLIMATES OF THE SEA.

The fauna and flora of the Sea are as much the creatures of Climate,
and are as dependent for their well-being upon temperature, as are the
fauna and flora of the dry land. Were it not so, we should find the
fish and the algæ, the marine insect and the coral, distributed equally
and alike in all parts of the ocean; the polar whale would delight in
the torrid zone; and the habitat of the pearl oyster would be also
under the iceberg, or in frigid waters colder than the melting ice.


THE CIRCULATION OF THE SEA.

The coral islands, reefs, and beds with which the Pacific Ocean is
studded and garnished, were built up of materials which a certain
kind of insect quarried from the sea-water. The currents of the sea
ministered to this little insect; they were its _hod-carriers_. When
fresh supplies of solid matter were wanted for the coral rock upon
which the foundations of the Polynesian Islands were laid, these
hod-carriers brought them in unfailing streams of sea-water, loaded
with food and building-materials for the coralline: the obedient
currents thread the widest and the deepest sea. Now we know that
its adaptations are suited to all the wants of every one of its
inhabitants,--to the wants of the coral insect as well as those of the
whale. Hence _we know_ that the sea has its system of circulation: for
it transports materials for the coral rock from one part of the world
to another; its currents receive them from rivers, and hand them over
to the little mason for the structure of the most stupendous works of
solid masonry that man has ever seen--the coral islands of the sea.


TEMPERATURE OF THE SEA.

Between the hottest hour of the day and the coldest hour of the night
there is frequently a change of four degrees in the Temperature of the
Sea. Taking one-fifth of the Atlantic Ocean for the scene of operation,
and the difference of four degrees to extend only ten feet below
the surface, the total and absolute change made in such a mass of
sea-water, by altering its temperature two degrees, is equivalent to a
change in its volume of 390,000,000 cubic feet.


TRANSPARENCY OF THE OCEAN.

Captain Glynn, U.S.N., has made some interesting observations, ranging
over 200° of latitude, in different oceans, in very high latitudes,
and near the equator. His apparatus was simple: a common white
dinner-plate, slung so as to lie in the water horizontally, and sunk
by an iron pot with a line. Numbering the fathoms at which the plate
was visible below the surface, Captain Glynn saw it on two occasions,
at the maximum, twenty-five fathoms (150 feet) deep; the water was
extraordinarily clear, and to lie in the boat and look down was like
looking down from the mast-head; and the objects were clearly defined
to a great depth.


THE BASIN OF THE ATLANTIC.

In its entire length, the basin of this sea is a long trough,
separating the Old World from the New, and extending probably from pole
to pole.

This ocean-furrow was scored into the solid crust of our planet by the
Almighty hand, that there the waters which “he called seas” might be
gathered together so as to “let the dry land appear,” and fit the earth
for the habitation of man.

From the top of Chimborazo to the bottom of the Atlantic, at the
deepest place yet recognised by the plummet in the North Atlantic, the
distance in a vertical line is nine miles.

Could the waters of the Atlantic be drawn off, so as to expose to
view this great sea-gash, which separates continents, and extends
from the Arctic to the Antarctic, it would present a scene the most
grand, rugged, and imposing. The very ribs of the solid earth, with
the foundations of the sea, would be brought to light; and we should
have presented to us at one view, in the empty cradle of the ocean,
“a thousand fearful wrecks,” with that dreadful array of dead men’s
skulls, great anchors, heaps of pearls and inestimable stones, which,
in the dreamer’s eye, lie scattered on the bottom of the sea, making it
hideous with sights of ugly death.


GALES OF THE ATLANTIC.

Lieutenant Maury has, in a series of charts of the North and South
Atlantic, exhibited, by means of colours, the prevalence of Gales
over the more stormy parts of the oceans for each month in the year.
One colour shows the region in which there is a gale every six days;
another colour every six to ten days; another every ten to fourteen
days: and there is a separate chart for each month and each ocean.


SOLITUDE AT SEA.

Between Humboldt’s Current of Peru and the great equatorial flow, there
is “a desolate region,” rarely visited by the whale, either sperm or
right. Formerly this part of the ocean was seldom whitened by the sails
of a ship, or enlivened by the presence of man. Neither the industrial
pursuits of the sea nor the highways of commerce called him into it.
Now and then a roving cruiser or an enterprising whalesman passed that
way; but to all else it was an unfrequented part of the ocean, and so
remained until the gold-fields of Australia and the guano islands of
Peru made it a thoroughfare. All vessels bound from Australia to South
America now pass through it; and in the journals of some of them it
is described as a region almost void of the signs of life in both sea
and air. In the South-Pacific Ocean especially, where there is such a
wide expanse of water, sea-birds often exhibit a companionship with a
vessel, and will follow and keep company with it through storm and calm
for weeks together. Even the albatross and Cape pigeon, that delight
in the stormy regions of Cape Horn and the inhospitable climates of
the Antarctic regions, not unfrequently accompany vessels into the
perpetual summer of the tropics. The sea-birds that join the ship as
she clears Australia will, it is said, follow her to this region, and
then disappear. Even the chirp of the stormy petrel ceases to be heard
here, and the sea itself is said to be singularly barren of “moving
creatures that have life.”


BOTTLES AND CURRENTS AT SEA.

Seafaring people often throw a bottle overboard, with a paper
stating the time and place at which it is done. In the absence of
other information as to Currents, that afforded by these mute little
navigators is of great value. They leave no track behind them, it is
true, and their routes cannot be ascertained; but knowing where they
are cast, and seeing where they are found, some idea may be formed as
to their course. Straight lines may at least be drawn, showing the
shortest distance from the beginning to the end of their voyage, with
the time elapsed. Admiral Beechey has prepared a chart, representing,
in this way, the tracks of more than 100 bottles. From this it appears
that the waters from every quarter of the Atlantic tend towards the
Gulf of Mexico and its stream. Bottles cast into the sea midway between
the Old and the New Worlds, near the coasts of Europe, Africa, and
America at the extreme north or farthest south, have been found either
in the West Indies, or the British Isles, or within the well-known
range of Gulf-Stream waters.


“THE HORSE LATITUDES”

are the belts of calms and light airs which border the polar edge of
the north-east trade-winds. They are so called from the circumstance
that vessels formerly bound from New England to the West Indies, with a
deck-load of horses, were often so delayed in this calm belt of Cancer,
that, from the want of water for their animals, they were compelled to
throw a portion of them overboard.


“WHITE WATER” AND LUMINOUS ANIMALS AT SEA.

Captain Kingman, of the American clipper-ship _Shooting Star_, in lat.
8° 46′ S., long. 105° 30′ E., describes a patch of _white water_,
about twenty-three miles in length, making the whole ocean appear like
a plain covered with snow. He filled a 60-gallon tub with the water,
and found it to contain small luminous particles seeming to be alive
with worms and insects, resembling a grand display of rockets and
serpents seen at a great distance in a dark night; some of the serpents
appearing to be six inches in length, and very luminous. On being taken
up, they emitted light until brought within a few feet of a lamp, when
nothing was visible; but by aid of a sextant’s magnifier they could
be plainly seen--a jelly-like substance, without colour. A specimen
two inches long was visible to the naked eye; it was about the size
of a large hair, and tapered at the ends. By bringing one end within
about one-fourth of an inch of a lighted lamp, the flame was attracted
towards it, and burned with a red light; the substance crisped in
burning, something like hair, or appeared of a red heat before being
consumed. In a glass of the water there were several small round
substances (say 1/16th of an inch in diameter) which had the power of
expanding and contracting; when expanded, the outer rim appeared like a
circular saw, the teeth turned inward.

The scene from the clipper’s deck was one of awful grandeur: the sea
having turned to phosphorus, and the heavens being hung in blackness,
and the stars going out, seemed to indicate that all nature was
preparing for that last grand conflagration which we are taught to
believe will annihilate this material world.


INVENTION OF THE LOG.

Long before the introduction of the Log, hour-glasses were used to
tell the distance in sailing. Columbus, Juan de la Cosa, Sebastian
Cabot, and Vasco de Gama, were not acquainted with the Log and its mode
of application; and they estimated the ship’s speed merely by the eye,
while they found the distance they had made by the running-down of the
sand in the _ampotellas_, or hour-glasses. The Log for the measurement
of the distance traversed is stated by writers on navigation not to
have been invented until the end of the sixteenth or the beginning of
the seventeenth century (see _Encyclopædia Britannica_, 7th edition,
1842). The precise date is not known; but it is certain that Pigafetta,
the companion of Magellan, speaks, in 1521, of the Log as a well-known
means of finding the course passed over. Navarete places the use of the
log-line in English ships in 1577.


LIFE OF THE SEA-DEEPS.

The ocean teems with life, we know. Of the four elements of the old
philosophers,--fire, earth, air, and water,--perhaps the sea most of
all abounds with living creatures. The space occupied on the surface
of our planet by the different families of animals and their remains
is inversely as the size of the individual; the smaller the animal,
generally speaking, the greater the space occupied by his remains.
Take the elephant and his remains, and a microscopic animal and his,
and compare them; the contrast as to space occupied is as striking as
that of the coral reef or island with the dimensions of the whale. The
graveyard that would hold the corallines, is larger than the graveyard
that would hold the elephants.


DEPTHS OF OCEAN AND AIR UNKNOWN.

At some few places under the tropics, no bottom has been found with
soundings of 26,000 feet, or more than four miles; whilst in the air,
if, according to Wollaston, we may assume that it has a limit from
which waves of sound may be reverberated, the phenomenon of twilight
would incline us to assume a height at least nine times as great. The
aerial ocean rests partly on the solid earth, whose mountain-chains and
elevated plateaus rise like green wooded shoals, and partly on the sea,
whose surface forms a moving base, on which rest the lower, denser, and
more saturated strata of air.--_Humboldt’s Cosmos_, vol. i.

The old Alexandrian mathematicians, on the testimony of Plutarch,
believed the depth of the sea to depend on the height of the mountains.
Mr. W. Darling has propounded to the British Association the theory,
that as the sea covers three times the area of the land, so it is
reasonable to suppose that the depth of the ocean, and that for a
large portion, is three times as great as the height of the highest
mountain. Recent soundings show depths in the sea much greater than any
elevations on the surface of the earth; for a line has been veered to
the extent of seven miles.--_Dr. Scoresby._


GREATEST ASCERTAINED DEPTH OF THE SEA.

In the dynamical theory of the tides, the ratio of the effects of the
sun and moon depends, not only on the masses, distances, and periodic
times of the two luminaries, but also on the Depth of the Sea; and
this, accordingly, may be computed when the other quantities are known.
In this manner Professor Haughton has deduced, from the solar and lunar
coefficients of the diurnal tide, a mean depth of 5·12 miles; a result
which accords in a remarkable manner with that inferred from the ratio
of the semi-diurnal co-efficients as obtained by Laplace from the
Brest observations. Professor Hennessey states, that from what is now
known regarding the depth of the ocean, the continents would appear as
plateaus elevated above the oceanic depressions to an amount which,
although small compared to the earth’s radius, would be considerable
when compared to its outswelling at the equator and its flattening
towards the poles; and the surface thus presented would be the true
surface of the earth.

The greatest depths at which the bottom of the sea has been reached
with the plummet are in the North-Atlantic Ocean; and the places where
it has been fathomed (by the United-States deep-sea sounding apparatus)
do not show it to be deeper than 25,000 feet = 4 miles, 1293 yards, 1
foot. The deepest place in this ocean is probably between the parallels
of 35° and 40° north latitude, and immediately to the southward of the
Grand Banks of Newfoundland.

  It appears that, with one exception, the bottom of the
  North-Atlantic Ocean, as far as examined, from the depth of about
  sixty fathoms to that of more than two miles (2000 fathoms), is
  literally nothing but a mass of microscopic shells. Not one of
  the animalcules from these shells has been found living in the
  surface-waters, nor in shallow water along the shore. Hence arises
  the question, Do they live on the bottom, at the immense depths
  where the shells are found; or are they borne by submarine currents
  from their real habitat?


RELATIVE LEVELS OF THE RED SEA AND MEDITERRANEAN.

The French engineers, at the beginning of the present century, came
to the conclusion that the Red Sea was about thirty feet above the
Mediterranean: but the observations of Mr. Robert Stephenson, the
English engineer, at Suez; of M. Negretti, the Austrian, at Tineh,
near the ancient Pelusium; and the levellings of Messrs. Talabat,
Bourdaloue, and their assistants between the two seas;--have proved
that the low-water mark of ordinary tides at Suez and Tineh is very
nearly on the same levels, the difference being that at Suez it is
rather more than one inch lower.--_Leonard Horner_; _Proceedings of the
Royal Society_, 1855.


THE DEPTH OF THE MEDITERRANEAN.

Soundings made in the Mediterranean suffice to indicate depths equal
to the average height of the mountains girding round this great basin;
and, if one particular experiment may be credited, reaching even to
15,000 feet--an equivalent to the elevation of the highest Alps. This
sounding was made about ninety miles east of Malta. Between Cyprus and
Egypt, 6000 feet of line had been let down without reaching the bottom.
Other deep soundings have been made in other places with similar
results. In the lines of sea between Egypt and the Archipelago, it is
stated that one sounding made by the _Tartarus_ between Alexandria
and Rhodes reached bottom at the depth of 9900 feet; another, between
Alexandria and Candia, gave a depth of 300 feet beyond this. These
single soundings, indeed, whether of ocean or sea, are always open to
the certainty that greater as well as lesser depths must exist, to
which no line has ever been sunk; a case coming under that general law
of probabilities so largely applicable in every part of physics. In the
Mediterranean especially, which has so many aspects of a sunken basin,
there may be abysses of depth here and there which no plummet is ever
destined to reach.--_Edinburgh Review._


COLOUR OF THE RED SEA.

M. Ehrenberg, while navigating the Red Sea, observed that the red
colour of its waters was owing to enormous quantities of a new animal,
which has received the name of _oscillatoria rubescens_, and which
seems to be the same with what Haller has described as a _purple
conferva_ swimming in water; yet Dr. Bonar, in his work entitled _The
Desert of Sinai_, records:

  Blue I have called the sea; yet not strictly so, save in the far
  distance. It is neither a _red_ nor a _blue_ sea, but emphatically
  green,--yes, green, of the most brilliant kind I ever saw. This is
  produced by the immense tracts of shallow water, with yellow sand
  beneath, which always gives this green to the sea, even in the
  absence of verdure on the shore or sea-weeds beneath. The _blue_ of
  the sky and the _yellow_ of the sands meeting and intermingling in
  the water, form the _green_ of the sea; the water being the medium
  in which the mixing or fusing of the colours takes place.


WHAT IS SEA-MILK?

The phenomena with this name and that of “Squid” are occasioned by the
presence of phosphorescent animalcules. They are especially produced
in the intertropical seas, and they appear to be chiefly abundant
in the Gulf of Guinea and in the Arabian Gulf. In the latter, the
phenomenon was known to the ancients more than a century before the
Christian era, as may be seen from a curious passage from the geography
of Agatharcides: “Along this country (the coast of Arabia) the sea
has a white aspect like a river: the cause of this phenomenon is a
subject of astonishment to us.” M. Quatrefages has discovered that the
_Noctilucæ_ which produce this phenomenon do not always give out clear
and brilliant sparks, but that under certain circumstances this light
is replaced by a steady clearness, which gives in these animalcules a
white colour. The waters in which they have been observed do not change
their place to any sensible degree.


THE BOTTOM OF THE SEA A BURIAL-PLACE.

Among the minute shells which have been fished up from the great
telegraphic plateau at the bottom of the sea between Newfoundland and
Ireland, the microscope has failed to detect a single particle of sand
or gravel; and the inference is, that there, if any where, the waters
of the sea are at rest. There is not motion enough there to abrade
these very delicate organisms, nor current enough to sweep them about
and mix them up with a grain of the finest sand, nor the smallest
particle of gravel from the loose beds of _débris_ that here and there
strew the bottom of the sea. The animalculæ probably do not live or die
there. They would have had no light there; and, if they lived there,
their frail textures would be subjected in their growth to a pressure
upon them of a column of water 12,000 feet high, equal to the weight of
400 atmospheres. They probably live and sport near the surface, where
they can feel the genial influence of both light and heat, and are
buried in the lichen caves below after death.

It is now suggested, that henceforward we should view the surface of
the sea as a nursery teeming with nascent organisms, and its depths as
the cemetery for families of living creatures that outnumber the sands
on the sea-shore for multitude.

Where there is a nursery, hard by there will be found also a
graveyard,--such is the condition of the animal world. But it never
occurred to us before to consider the surface of the sea as one
wide nursery, its every ripple as a cradle, and its bottom one vast
burial-place.--_Lieut. Maury._


WHY IS THE SEA SALT?

It has been replied, In order to preserve it in a state of purity;
which is, however, untenable, mainly from the fact that organic
impurities in a vast body of moving water, whether fresh or salt,
become rapidly lost, so as apparently to have called forth a special
agency to arrest the total organised matter in its final oscillation
between the organic and inorganic worlds. Thus countless hosts of
microscopic creatures swarm in most waters, their principal function
being, as Professor Owen surmises, to feed upon and thus restore to
the living chain the almost unorganised matter of various zones. These
creatures preying upon one another, and being preyed upon by others
in their turn, the circulation of organic matter is kept up. If we
do not adopt this view, we must at least look upon the Infusoria and
Foraminifera as scavenger agents to prevent an undue accumulation
of decaying matter; and thus the salt condition of the sea is not a
necessity.

Nor is the amount of saline matter in the sea sufficient to arrest
decomposition. That the sea is salt to render it of greater density,
and by lowering its freezing point to preserve it from congelation to
within a shorter distance of the poles, though admissible, scarcely
meets the entire solution of the question. The freezing point of
sea-water, for instance, is only 3½° F. lower than that of fresh water;
hence, with the present distribution of land and sea--and still less,
probably, with that which obtained in former geological epochs--no very
important effects would have resulted had the ocean been fresh instead
of salt.

Now Professor Chapman, of Toronto, suggests that the salt condition of
the sea is mainly intended to regulate evaporation, and to prevent an
undue excess of that phenomenon; saturated solutions evaporating more
slowly than weak ones, and these latter more slowly again than pure
water.

Here, then, we have a self-adjusting phenomenon and admirable
contrivance in the balance of forces. If from any temporary cause there
be an unusual amount of saline matter in the sea, evaporation goes on
the more and more slowly; and, on the other hand, if this proportion
be reduced by the addition of fresh water in undue excess, the
evaporating power is the more and more increased--thus aiding time, in
either instance, to restore the balance. The perfect system of oceanic
circulation may be ascribed, in a great degree at least, if not wholly,
to the effect produced by the salts of the sea upon the mobility and
circulation of its waters.

Now this is an office which the sea performs in the economy of the
universe by virtue of its saltness, and which it could not perform were
its waters altogether fresh. And thus philosophers have a clue placed
in their hands which will probably guide to one of the many hidden
reasons that are embraced in the true answer to the question, “_Why is
the sea salt?_”


HOW TO ASCERTAIN THE SALTNESS OF THE SEA.

Dry a towel in the sun, weigh it carefully, and note its weight. Then
dip it into sea-water, wring it sufficiently to prevent its dripping,
and weigh it again; the increase of the weight being that of the water
imbibed by the cloth. It should then be thoroughly dried, and once more
weighed; and the excess of this weight above the original weight of the
cloth shows the quantity of the salt retained by it; then, by comparing
the weight of this salt with that of the sea-water imbibed by the
cloth, we shall find what proportion of salt was contained in the water.


ALL THE SALT IN THE SEA.

The amount of common Salt in all the oceans is estimated by Schafhäutl
at 3,051,342 cubic geographical miles. This would be about five times
more than the mass of the Alps, and only one-third less than that of
the Himalaya. The sulphate of soda equals 633,644·36 cubic miles, or is
equal to the mass of the Alps; the chloride of magnesium, 441,811·80
cubic miles; the lime salts, 109,339·44 cubic miles. The above supposes
the mean depth to be but 300 metres, as estimated by Humboldt.
Admitting, with Laplace, that the mean depth is 1000 metres, which is
more probable, the mass of marine salt will be more than double the
mass of the Himalaya.--_Silliman’s Journal_, No. 16.

Taking the average depth of the ocean at two miles, and its average
saltness at 3½ per cent, it appears that there is salt enough in the
sea to cover to the thickness of one mile an area of 7,000,000 of
square miles. Admit a transfer of such a quantity of matter from an
average of half a mile above to one mile below the sea-level, and
astronomers will show by calculation that it would alter the length of
the day.

These 7,000,000 of cubic miles of crystal salt have not made the sea
any fuller.


PROPERTIES OF SEA-WATER.

The solid constituents of sea-water amount to about 3½ per cent of
its weight, or nearly half an ounce to the pound. Its saltness is
caused as follows: Rivers which are constantly flowing into the
ocean contain salts varying from 10 to 50, and even 100, grains per
gallon. They are chiefly common salt, sulphate and carbonate of lime,
magnesia,[41] soda, potash, and iron; and these are found to constitute
the distinguishing characteristics of sea-water. The water which
evaporates from the sea is nearly pure, containing but very minute
traces of salts. Falling as rain upon the land, it washes the soil,
percolates through the rocky layers, and becomes charged with saline
substances, which are borne seaward by the returning currents. The
ocean, therefore, is the great depository of every thing that water
can dissolve and carry down from the surface of the continents; and
as there is no channel for their escape, they consequently accumulate
(_Youmans’ Chemistry_). They would constantly accumulate, as this very
shrewd author remarks, were it not for the shells and insects of the
sea and other agents.


SCENERY AND LIFE OF THE ARCTIC REGIONS.

The late Dr. Scoresby, from personal observations made in the course of
twenty-one voyages to the Arctic Regions, thus describes these striking
characteristics:

  The coast scenes of Greenland are generally of an abrupt character,
  the mountains frequently rising in triangular profile; so much
  so, that it is sometimes not possible to effect their ascent. One
  of the most notable characteristics of the Arctic lands is the
  deception to which travellers are liable in regard to distances.
  The occasion of this is the quantity of light reflected from
  the snow, contrasted with the dark colour of the rocks. Several
  persons of considerable experience have been deceived in this way,
  imagining, for example, that they were close to the shore when in
  fact they were more than twenty miles off. The trees of these lands
  are not more than three inches above ground.

  Many of the icebergs are five miles in extent, and some are to be
  seen running along the shore measuring as much as thirteen miles.
  Dr. Scoresby has seen a cliff of ice supported on those floating
  masses 402 feet in height. There is no place in the world where
  animal life is to be found in greater profusion than in Greenland,
  Spitzbergen, Baffin’s Bay, and other portions of the Arctic
  regions. This is to be accounted for by the abundance and richness
  of the food supplied by the sea. The number of birds is especially
  remarkable. On one occasion, no less than a million of little hawks
  came in sight of Dr. Scoresby’s ship within a single hour.

  The various phenomena of the Greenland sea are very interesting.
  The different colours of the sea-water--olive or bottle-green,
  reddish-brown, and mustard--have, by the aid of the microscope,
  been found to be owing to animalculæ of these various colours:
  in a single drop of mustard-coloured water have been counted
  26,450 animals. Another remarkable characteristic of the Greenland
  sea-water is its warm temperature--one, two, and three degrees
  above the freezing-point even in the cold season. This Dr.
  Scoresby accounts for by supposing the flow in that direction of
  warm currents from the south. The polar fields of ice are to be
  found from eight or nine to thirty or forty feet in thickness. By
  fastening a hook twelve or twenty inches in these masses of ice, a
  ship could ride out in safety the heaviest gales.


ICEBERG OF THE POLAR SEAS.

The ice of this berg, although opaque and vascular, is true glacier
ice, having the fracture, lustre, and other external characters of
a nearly homogeneous growth. The iceberg is true ice, and is always
dreaded by ships. Indeed, though modified by climate, and especially by
the alternation of day and night, the polar glacier must be regarded as
strictly atmospheric in its increments, and not essentially differing
from the glacier of the Alps. The general appearance of a berg may be
compared to frosted silver; but when its fractures are very extensive,
the exposed faces have a very brilliant lustre. Nothing can be more
exquisite than a fresh, cleanly fractured berg surface: it reminds one
of the recent cleavage of sulphate of strontian--a resemblance more
striking from the slightly lazulitic tinge of each.--_U. S. Grinnel
Expedition in Search of Sir J. Franklin._


IMMENSITY OF POLAR ICE.

The quantity of solid matter that is drifted out of the Polar Seas
through one opening--Davis’s Straits--alone, and during a part of the
year only, covers to the depth of seven feet an area of 300,000 square
miles, and weighs not less than 18,000,000,000 tons. The quantity of
water required to float and drive out this solid matter is probably
many times greater than this. A quantity of water equal in weight to
these two masses has to go in. The basin to receive these inflowing
waters, _i. e._ the unexplored basin about the North Pole, includes an
area of 1,500,000 square miles; and as the outflowing ice and water are
at the surface, the return current must be submarine.

These two currents, therefore, it may be perceived, keep in motion
between the temperate and polar regions of the earth a volume of water,
in comparison with which the mighty Mississippi in its greatest floods
sinks down to a mere rill.--_Maury._


OPEN SEA AT THE POLE.

The following fact is striking: In 1662-3, Mr. Oldenburg, Secretary to
the Royal Society, was ordered to register a paper entitled “Several
Inquiries concerning Greenland, answered by Mr. Gray, who had visited
those parts.” The nineteenth query was, “How near any one hath been
known to approach the Pole. _Answer._ I once met upon the coast of
Greenland a Hollander, that swore he had been but half a degree from
the Pole, showing me his journal, which was also attested by his mate;
where _they had seen no ice or land, but all water_.” Boyle mentions
a similar account, which he received from an old Greenland master, on
April 5, 1765.


RIVER-WATER ON THE OCEAN.

Captain Sabine found discoloured water, supposed to be that of the
Amazon, 300 miles distant in the ocean from the embouchure of that
river. It was about 126 feet deep. Its specific gravity was = 1·0204,
and the specific gravity of the sea-water = 1·0262. This appears to
be the greatest distance from land at which river-water has been
detected on the surface of the ocean. It was estimated to be moving
at the rate of three miles an hour, and had been turned aside by an
ocean-current. “It is not a little curious to reflect,” says Sir Henry
de la Beche, “that the agitation and resistance of its particles should
be sufficient to keep finely comminuted solid matter mechanically
suspended, so that it would not be disposed freely to part with it
except at its junction with the sea-water over which it flows, and
where, from friction, it is sufficiently retarded.”


THE THAMES AND ITS SALT-WATER BED.

The Thames below Woolwich, in place of flowing upon a solid bottom,
really flows upon the liquid bottom formed by the water of the sea.
At the flow of the tide, the fresh water is raised, as it were, in a
single mass by the salt water which flows in, and which ascends the
bed of the river, while the fresh water continues to flow towards the
sea.--_Mr. Stevenson, in Jameson’s Journal._


FRESH SPRINGS IN THE MIDDLE OF THE OCEAN.

On the southern coast of the island of Cuba, at a few miles from land,
Springs of Fresh Water gush from the bed of the Ocean, probably under
the influence of hydrostatic pressure, and rise through the midst
of the salt water. They issue forth with such force that boats are
cautious in approaching this locality, which has an ill repute on
account of the high cross sea thus caused. Trading vessels sometimes
visit these springs to take in a supply of fresh water, which is thus
obtained in the open sea. The greater the depth from which the water is
taken, the fresher it is found to be.


“THE BLACK WATERS.”

In the upper portion of the basin of the Orinoco and its tributaries,
Nature has several times repeated the enigmatical phenomenon of the
so-called “Black Waters.” The Atabapo, whose banks are adorned with
Carolinias and arborescent Melastomas, is a river of a coffee-brown
colour. In the shade of the palm-groves this colour seems about to
pass into ink-black. When placed in transparent vessels, the water
appears of a golden yellow. The image of the Southern Constellation
is reflected with wonderful clearness in these black streams. When
their waters flow gently, they afford to the observer, when taking
astronomical observations with reflecting instruments, a most excellent
artificial horizon. These waters probably owe their peculiar colour to
a solution of carburetted hydrogen, to the luxuriance of the tropical
vegetation, and to the quantity of plants and herbs on the ground over
which they flow.--_Humboldt’s Aspects of Nature_, vol. i.


GREAT CATARACT IN INDIA.

Where the river Shirhawti, between Bombay and Cape Comorin, falls into
the Gulf of Arabia, it is about one-fourth of a mile in width, and in
the rainy season some thirty feet in depth. This immense body of water
rushes down a rocky slope 300 feet, at an angle of 45°, at the bottom
of which it makes a perpendicular plunge of 850 feet into a black and
dismal abyss, with a noise like the loudest thunder. The whole descent
is therefore 1150 feet, or several times that of Niagara; but the
volume of water in the latter is somewhat larger than in the former.


CAUSE OF WAVES.

The friction of the wind combines with the tide in agitating the
surface of the ocean, and, according to the theory of undulations,
each produces its effect independently of the other. Wind, however,
not only raises waves, but causes a transfer of superficial water
also. Attraction between the particles of air and water, as well
as the pressure of the atmosphere, brings its lower stratum into
adhesive contact with the surface of the sea. If the motion of the
wind be parallel to the surface, there will still be friction, but the
water will be smooth as a mirror; but if it be inclined, in however
small a degree, a ripple will appear. The friction raises a minute
wave, whose elevation protects the water beyond it from the wind,
which consequently impinges on the surface at a small angle: thus
each impulse, combining with the other, produces an undulation which
continually advances.--_Mrs. Somerville’s Physical Geography._


RATE AT WHICH WAVES TRAVEL.

Professor Bache states, as one of the effects of an earthquake at
Simoda, on the island of Niphon, in Japan, that the harbour was first
emptied of water, and then came in an enormous wave, which again
receded and left the harbour dry. This occurred several times. The
United-States self-acting tide-gauge at San Francisco, which records
the rise of the tide upon cylinders turned by clocks, showed that at
San Francisco, 4800 miles from the scene of the earthquake, the first
wave arrived twelve hours and sixteen minutes after it had receded from
the harbour of Simoda. It had travelled across the broad bosom of the
Pacific Ocean at the rate of six miles and a half a minute, and arrived
on the shores of California: the first wave being seven-tenths of a
foot in height, and lasting for about half an hour, followed by seven
lesser waves, at intervals of half an hour each.

The velocity with which a wave travels depends on the depth of the
ocean. The latest calculations for the Pacific Ocean give a depth of
from 14,000 to 18,000 fathoms. It is remarkable how the estimates of
the ocean’s depth have grown less. Laplace assumed it at ten miles,
Whewell at 3·5, while the above estimate brings it down to two miles.

Mr. Findlay states, that the dynamic force exerted by Sea-Waves is
greatest at the crest of the wave before it breaks; and its power in
raising itself is measured by various facts. At Wasburg, in Norway,
in 1820, it rose 400 feet; and on the coast of Cornwall, in 1843,
300 feet. The author shows that waves have sometimes raised a column
of water equivalent to a pressure of from three to five tons the
square foot. He also proves that the velocity of the waves depends
on their length, and that waves of from 300 to 400 feet in length
from crest to crest travel from twenty to twenty-seven and a half
miles an hour. Waves travel great distances, and are often raised by
distant hurricanes, having been felt simultaneously at St. Helena
and Ascension, though 600 miles apart; and it is probable that
ground-swells often originate at the Cape of Good Hope, 3000 miles
distant. Dr. Scoresby found the travelling rate of the Atlantic waves
to be 32·67 English statute miles per hour.

In the winter of 1856, a heavy ground-swell, brought on by five hours’
gale, scoured away in fourteen hours 3,900,000 tons of pebbles from
the coast near Dover; but in three days, without any shift of wind,
upwards of 3,000,000 tons were thrown back again. These figures are to
a certain extent conjectural; but the quantities have been derived from
careful measurement of the profile of the beach.


OCEAN-HIGHWAYS: HOW SEA-ROUTES HAVE BEEN SHORTENED.

When one looks seaward from the shore, and sees a ship disappear
in the horizon as she gains an offing on a voyage to India, or the
Antipodes perhaps, the common idea is that she is bound over a
trackless waste; and the chances of another ship sailing with the same
destination the next day, or the next week, coming up and speaking
with her on the “pathless ocean,” would to most minds seem slender
indeed. Yet the truth is, the winds and the currents are now becoming
so well understood, that the navigator, like the backwoodsman in the
wilderness, is enabled literally to “blaze his way” across the ocean;
not, indeed, upon trees, as in the wilderness, but upon the wings of
the wind. The results of scientific inquiry have so taught him how to
use these invisible couriers, that they, with the calm belts of the
air, serve as sign-boards to indicate to him the turnings and forks and
crossings by the way.

  Let a ship sail from New York to California, and the next week let
  a faster one follow; they will cross each other’s path many times,
  and are almost sure to see each other by the way, as in the voyage
  of two fine clipper-ships from New York to California. On the ninth
  day after the _Archer_ had sailed, the _Flying Cloud_ put to sea.
  Both ships were running against time, but without reference to
  each other. The _Archer_, with wind and current charts in hand,
  went blazing her way across the calms of Cancer, and along the
  new route down through the north-east trades to the equator; the
  _Cloud_ followed, crossing the equator upon the trail of Thomas of
  the _Archer_. Off Cape Horn she came up with him, spoke him, and
  handed him the latest New York dates. The _Flying Cloud_ finally
  ranged ahead, made her adieus, and disappeared among the clouds
  that lowered upon the western horizon, being destined to reach her
  port a week or more in advance of her Cape Horn consort. Though
  sighting no land from the time of their separation until they
  gained the offing of San Francisco,--some six or eight thousand
  miles off,--the tracks of the two vessels were so nearly the same,
  that being projected upon the chart, they appear almost as one.

  This is the great course of the ocean: it is 15,000 miles in
  length. Some of the most glorious trials of speed and of prowess
  that the world ever witnessed among ships that “walk the waters”
  have taken place over it. Here the modern clipper-ship--the noblest
  work that has ever come from the hands of man--has been sent,
  guided by the lights of science, to contend with the elements, to
  outstrip steam, and astonish the world.--_Maury._


ERROR UPON ERROR.

The great inducement to Mr. Babbage, some years since, to attempt
the construction of a machine by which astronomical tables could be
calculated and even printed by mechanical means, and with entire
accuracy, was the errors in the requisite tables. Nineteen such
errors, in point of fact, were discovered in an edition of Taylor’s
_Logarithms_ printed in 1796; some of which might have led to the
most dangerous results in calculating a ship’s place. These nineteen
errors (of which one only was an error of the press) were pointed out
in the _Nautical Almanac_ for 1832. In one of these _errata_, the seat
of the error was stated to be in cosine of 14° 18′ 3″. Subsequent
examination showed that there was an error of one second in this
correction, and accordingly, in the _Nautical Almanac_ of the next
year a new correction was necessary. But in making the new correction
of one second, a new error was committed of ten degrees, making it
still necessary, in some future edition of the _Nautical Almanac_,
to insert an _erratum_ in an _erratum_ of the _errata_ in Taylor’s
_Logarithms_.--_Edinburgh Review_, vol. 59.




Phenomena of Heat.


THE LENGTH OF THE DAY AND THE HEAT OF THE EARTH.

As we may judge of the uniformity of temperature from the unaltered
time of vibration of a pendulum, so we may also learn from the
unaltered rotatory velocity of the earth the amount of stability in the
mean temperature of our globe. This is the result of one of the most
brilliant applications of the knowledge we had long possessed of the
movement of the heavens to the thermic condition of our planet. The
rotatory velocity of the earth depends on its volume; and since, by the
gradual cooling of the mass by radiation, the axis of rotation would
become shorter, the rotatory velocity would necessarily increase, and
the length of the day diminish with a decrease of the temperature. From
the comparison of the secular inequalities in the motions of the moon
with the eclipses observed in former ages, it follows that, since the
time of Hipparchus,--that is, for full 2000 years,--the length of the
day has certainly not diminished by the hundredth part of a second. The
decrease of the mean heat of the globe during a period of 2000 years
has not therefore, taking the extremest limits, diminished as much as
1/306th of a degree of Fahrenheit.[42]--_Humboldt’s Cosmos_, vol. i.


NICE MEASUREMENT OF HEAT.

A delicate thermometer, placed on the ground, will be affected by the
passage of a single cloud across a clear sky; and if a succession of
clouds pass over, with intervals of clear sky between them, such an
instrument has been observed to fluctuate accordingly, rising with each
passing mass of vapour, and falling again when the radiation becomes
unrestrained.


EXPENDITURE OF HEAT BY THE SUN.

Sir John Herschel estimates the total Expenditure of Heat by the Sun in
a given time, by supposing a cylinder of ice 45 miles in diameter to be
continually darted into the sun _with the velocity of light_, and that
the water produced by its fusion were continually carried off: the heat
now given off constantly by radiation would then be wholly expended in
its liquefaction, on the one hand, so as to leave no radiant surplus;
while, on the other, the actual temperature at its surface would
undergo no diminution.

The great mystery, however, is to conceive how so enormous a
conflagration (if such it be) can be kept up. Every discovery in
chemical science here leaves us completely at a loss, or rather
seems to remove further the prospect of probable explanation. If
conjecture might be hazarded, we should look rather to the known
possibility of an indefinite generation of heat by friction, or to
its excitement by the electric discharge, than to any combustion of
ponderable fuel, whether solid or gaseous, for the origin of the solar
radiation.--_Outlines._[43]


DISTINCTIONS OF HEAT.

Among the curious laws of modern science are those which regulate the
transmission of radiant heat through transparent bodies. The heat of
our fires is intercepted and detained by screens of glass, and, being
so detained, warms them; while solar heat passes freely through and
produces no such effect. “The more recent researches of Delaroche,”
says Sir John Herschel, “however, have shown that this detention is
complete only when the temperature of the source of heat is low; but
that as the temperature gets higher a portion of the heat radiated
acquires a power of penetrating glass, and that the quantity which does
so bears continually a larger and larger proportion to the whole, as
the heat of the radiant body is more intense. This discovery is very
important, as it establishes a community of nature between solar and
terrestrial heat; while at the same time it leads us to regard the
actual temperature of the sun as far exceeding that of any earthly
flame.”


LATENT HEAT.

This extraordinary principle exists in all bodies, and may be pressed
out of them. The blacksmith hammers a nail until it becomes red hot,
and from it he lights the match with which he kindles the fire of his
forge. The iron has by this process become more dense, and percussion
will not again produce incandescence until the bar has been exposed in
fire to a red heat, when it absorbs heat, the particles are restored to
their former state, and we can again by hammering develop both heat and
light.--_R. Hunt, F.R.S._


HEAT AND EVAPORATION.

In a communication made to the French Academy, M. Daubrée calculates
that the Evaporation of the Water on the surface of the globe employs a
quantity of heat about equal to one-third of what is received from the
sun; or, in other words, equal to the melting of a bed of ice nearly
thirty-five feet in thickness if spread over the globe.


HEAT AND MECHANICAL POWER.

It has been found that Heat and Mechanical Power are mutually
convertible; and that the relation between them is definite, 772
foot-pounds of motive power being equivalent to a unit of heat, that
is, to the amount of heat requisite to raise a pound of water through
one degree of Fahrenheit.


HEAT OF MINES.

One cause of the great Heat of many of our deep Mines, which appears to
have been entirely lost sight of, is the chemical action going on upon
large masses of pyritic matter in their vicinity. The heat, which is so
oppressive in the United Mines in Cornwall that the miners work nearly
naked, and bathe in water at 80° to cool themselves, is without doubt
due to the decomposition of immense quantities of the sulphurets of
iron and copper known to be in this condition at a short distance from
these mineral works.--_R. Hunt, F.R.S._


VIBRATION OF HEATED METALS.

Mr. Arthur Trevelyan discovered accidentally that a bar of iron, when
heated and placed with one end on a solid block of lead, in cooling
vibrates considerably, and produces sounds similar to those of an
Æolian harp. The same effect is produced by bars of copper, zinc,
brass, and bell-metal, when heated and placed on blocks of lead, tin,
or pewter. The bars were four inches long, one inch and a half wide,
and three-eighths of an inch thick.

The conditions essential to these experiments are, That two different
metals must be employed--the one soft and possessed of moderate
conducting powers, viz. lead or tin, the other hard; and it matters not
whether soft metal be employed for the bar or block, provided the soft
metal be cold and the hard metal heated.

That the surface of the block shall be uneven, for when rendered quite
smooth the vibration does not take place; but the bar cannot be too
smooth.

That no matter be interposed, else it will prevent vibration, with
the exception of a burnish of gold leaf, the thickness of which cannot
amount to the two-hundred-thousandth part of an inch.--_Transactions of
the Royal Society of Edinburgh._


EXPANSION OF SPIRITS.

Spirits expand and become lighter by means of heat in a greater
proportion than water, wherefore they are heaviest in winter. A cubic
inch of brandy has been found by many experiments to weigh ten grains
more in winter than in summer, the difference being between four drams
thirty-two grains and four drams forty-two grains. Liquor-merchants
take advantage of this circumstance, and make their purchases in winter
rather than in summer, because they get in reality rather a larger
quantity in the same bulk, buying by measure.--_Notes in Various
Sciences._


HEAT PASSING THROUGH GLASS.

The following experiment is by Mr. Fox Talbot: Heat a poker bright-red
hot, and having opened a window, apply the poker quickly very near
to the outside of a pane, and the hand to the inside; a strong heat
will be felt at the instant, which will cease as soon as the poker
is withdrawn, and may be again renewed and made to cease as quickly
as before. Now it is well known, that if a piece of glass is so much
warmed as to convey the impression of heat to the hand, it will retain
some part of that heat for a minute or more; but in this experiment the
heat will vanish in a moment: it will not, therefore, be the heated
pane of glass that we shall feel, but heat which has come through the
glass in a free or radiant state.


HEAT FROM GAS-LIGHTING.

In the winter of 1835, Mr. W. H. White ascertained the temperature in
the City to be 3° higher than three miles south of London Bridge; and
_after the gas had been lighted in the City_ four or five hours the
temperature increased full 3°, thus making 6° difference in the three
miles.


HEAT BY FRICTION.

Friction as a source of Heat is well known: we rub our hands to
warm them, and we grease the axles of carriage-wheels to prevent
their setting fire to the wood. Count Rumford has established the
extraordinary fact, that an unlimited supply of heat may be derived
from friction by the same materials: he made great quantities of water
boil by causing a blunt borer to rub against a mass of metal immersed
in the water. Savages light their fires by rubbing two pieces of wood:
the _modus operandi_, as practised by the Kaffirs of South Africa, is
thus described by Captain Drayton:

  Two dry sticks, one being of hard and the other of soft wood, were
  the materials used. The soft stick was laid on the ground, and
  held firmly down by one Kaffir, whilst another employed himself
  in scooping out a little hole in the centre of it with the point
  of his assagy: into this little hollow the end of the hard wood
  was placed, and held vertically. These two men sat face to face,
  one taking the vertical stick between the palms of his hands, and
  making it twist about very quickly, while the other Kaffir held the
  lower stick firmly in its place; the friction caused by the end of
  one piece of wood revolving upon the other soon made the two pieces
  smoke. When the Kaffir who twisted became tired, the respective
  duties were exchanged. These operations having continued about a
  couple of minutes, sparks began to appear, and when they became
  numerous, were gathered into some dry grass, which was then swung
  round at arm’s length until a blaze was established; and a roaring
  fire was gladdening the hearts of the Kaffirs with the anticipation
  of a glorious feast in about ten minutes from the time that the
  operation was first commenced.


HEAT BY FRICTION FROM ICE.

When Sir Humphry Davy was studying medicine at Penzance, one of his
constant associates was Mr. Tom Harvey, a druggist in the above town.
They constantly experimented together; and one severe winter’s day,
after a discussion on the nature of heat, the young philosophers were
induced to go to Larigan river, where Davy succeeded in developing heat
by _rubbing two pieces of ice together_ so as to melt each other;[44]
an experiment which he repeated with much _éclat_ many years after,
in the zenith of his celebrity, at the Royal Institution. The pieces
of ice for this experiment are fastened to the ends of two sticks,
and rubbed together in air below the temperature of 32°: this Davy
readily accomplished on the day of severe cold at the Larigan river;
but when the experiment was repeated at the Royal Institution, it was
in the vacuum of an air-pump, when the temperature of the apparatus and
of the surrounding air was below 32°. It was remarked, that when the
surface of the rubbing pieces was rough, only half as much heat was
evolved as when it was smooth. When the pressure of the rubbing piece
was increased four times, the proportion of heat evolved was increased
sevenfold.


WARMING WITH ICE.

In common language, any thing is understood to be cooled or warmed when
the temperature thereof is made higher or lower, whatever may have been
the temperature when the change was commenced. Thus it is said that
melted iron is _cooled_ down to a sub-red heat, or mercury is cooled
from the freezing point to zero, or far below. By the same rule, solid
mercury, say 50° below zero, may, in any climate or temperature of the
atmosphere, be immediately warmed and melted by being imbedded in a
cake of ice.--_Scientific American._


REPULSION BY HEAT.

If water is poured upon an iron sieve, the wires of which are made
red-hot, it will not run through; but on cooling, it will pass through
rapidly. M. Boutigny, pursuing this curious inquiry, has proved
that the moisture upon the skin is sufficient to protect it from
disorganisation if the arm is plunged into baths of melted metal.
The resistance of the surfaces is so great that little elevation of
temperature is experienced. Professor Plücker has stated, that by
washing the arm with ether previously to plunging it into melted metal,
the sensation produced while in the molten mass is that of freezing
coldness.--_R. Hunt, F.R.S._


PROTECTION FROM INTENSE HEAT.

The singular power which the body possesses of resisting great heats,
and of breathing air of high temperatures, has at various times excited
popular wonder. In the last century some curious experiments were
made on this subject. Sir Joseph Banks, Dr. Solander, and Sir Charles
Blagden, entered a room in which the air had a temperature of 198°
Fahr., and remained ten minutes. Subsequently they entered the room
separately, when Dr. Solander found the heat 210°, and Sir Joseph
211°, whilst their bodies preserved their natural degree of heat.
Whenever they breathed upon a thermometer, it sank several degrees;
every inspiration gave coolness to their nostrils, and their breath
cooled their fingers when it reached them. Sir Charles Blagden entered
an apartment when the heat was 1° or 2° above 260°, and remained eight
minutes, mostly on the coolest spot, where the heat was above 240°.
Though very hot, Sir Charles felt no pain: during seven minutes his
breathing was good; but he then felt an oppression in his lungs, and
his pulse was 144, double its ordinary quickness. To prove the heat of
the room, eggs and a beefsteak were placed upon a tin frame near the
thermometer, when in twenty minutes the eggs were roasted hard, and in
forty-seven minutes the steak was dressed dry; and when the air was put
in motion by a pair of bellows upon another steak, part of it was well
done in thirteen minutes. It is remarkable, that in these experiments
the same person who experienced no inconvenience from air heated to
211°, could just bear rectified spirits of wine at 130°, cooling oil at
129°, cooling water at 123°, and cooling quicksilver at 117°.

Sir Francis Chantrey, the sculptor, however, exposed himself to a
temperature still higher than any yet mentioned, as described by Sir
David Brewster:

  The furnace which he employs for drying his moulds is about
  fourteen feet long, twelve feet high, and twelve feet broad. When
  it is raised to its highest temperature, with the doors closed,
  the thermometer stands at 350°, and the iron floor is red-hot. The
  workmen often enter it at a temperature of 340°, walking over the
  iron floor with wooden clogs, which are of course charred on the
  surface. On one occasion, Mr. Chantrey, accompanied by five or
  six of his friends, entered the furnace; and after remaining two
  minutes they brought out a thermometer which stood at 320°. Some
  of the party experienced sharp pains in the tips of their ears
  and in the septum of the nose, while others felt a pain in their
  eyes.--_Natural Magic_, 1833.

In some cases the clothing worn by the experimenters conducts away
the heat. Thus, in 1828, a Spaniard entered a heated oven, at the New
Tivoli, near Paris; he sang a song while a fowl was roasted by his
side, he then ate the fowl and drank a bottle of wine, and on coming
out his pulse beat 176°, and the thermometer was at 110° Reaumur. He
then stretched himself upon a plank in the oven surrounded by lighted
candles, when the mouth of the oven was closed; he remained there five
minutes, and on being taken out, all the candles were extinguished and
melted, and the Spaniard’s pulse beat 200°. Now much of the surprise
ceases when it is added that he wore wide woollen pantaloons, a loose
mantle of wool, and a great quilted cap; the several materials of this
clothing being bad conductors of heat.

In 1829 M. Chabert, the “Fire-King,” exhibited similar feats at the
Argyll Rooms in Regent Street. He first swallowed forty grains of
phosphorus, then two spoonfuls of oil at 330°, and next held his head
over the fumes of sulphuric acid. He had previously provided himself
with an antidote for the poison of the phosphorus. Dressed in a loose
woollen coat, he then entered a heated oven, and in five minutes cooked
two steaks; he then came out of the oven, when the thermometer stood at
380°. Upon another occasion, at White Conduit House, some of his feats
were detected.

The scientific secret is as follows: Muscular tissue is an extremely
bad conductor; and to this in a great measure the constancy of the
temperature of the human body in various zones is to be attributed. To
this fact also Sir Charles Blagden and Chantrey owed their safety in
exposing their bodies to a high temperature; from the almost impervious
character of the tissues of the body, the irritation produced was
confined to the surface.




Magnetism and Electricity.


MAGNETIC HYPOTHESES.

As an instance of the obstacles which erroneous hypotheses throw
in the way of scientific discovery, Professor Faraday adduces the
unsuccessful attempts that had been made in England to educe Magnetism
from Electricity until Oersted showed the simple way. Faraday relates,
that when he came to the Royal Institution as an assistant in the
laboratory, he saw Davy, Wollaston, and Young trying, by every way that
suggested itself to them, to produce magnetic effects from an electric
current; but having their minds diverted from the true course by their
existing hypotheses, it did not occur to them to try the effect of
holding a wire through which an electric current was passing over a
suspended magnetic needle. Had they done so, as Oersted afterwards did,
the immediate deflection of the needle would have proved the magnetic
property of an electric current. Faraday has shown that the magnetism
of a steel bar is caused by the accumulated action of all the particles
of which it is composed: this he proves by first magnetising a small
steel bar, and then breaking it successively into smaller and smaller
pieces, each one of which possesses a separate pole; and the same
operation may be continued until the particles become so small as not
to be distinguishable without a microscope.

We quote the above from a late Number of the _Philosophical Magazine_,
wherein also we find the following noble tribute to the genius and
public and private worth of Faraday:

  The public never can know and appreciate the national value of such
  a man as Faraday. He does not work to please the public, nor to win
  its guineas; and the said public, if asked its opinion as to the
  practical value of his researches, can see no possible practical
  issue there. The public does not know that we need prophets
  more than mechanics in science,--inspired men, who, by patient
  self-denial and the exercise of the high intellectual gifts of the
  Creator, bring us intelligence of His doings in Nature. To them
  their pursuits are good in themselves. Their chief reward is the
  delight of being admitted into communion with Nature, the pleasure
  of tracing out and proclaiming her laws, wholly forgetful whether
  those laws will ever augment our banker’s account or improve our
  knowledge of cookery. _Such men, though not honoured by the title
  of “practical,” are they which make practical men possible._
  They bring us the tamed forces of Nature, and leave it to others
  to contrive the machinery to which they may be yoked. If we are
  rightly informed, it was Faradaic electricity which shot the glad
  tidings of the fall of Sebastopol from Balaklava to Varna. Had
  this man converted his talent to commercial purposes, as so many
  do, we should not like to set a limit to his professional income.
  The quality of his services cannot be expressed by pounds; but
  that brave body, which for forty years has been the instrument
  of that great soul, is a fit object for a nation’s care, as the
  achievements of the man are, or will one day be, the object of a
  nation’s pride and gratitude.


THE CHINESE AND THE MAGNETIC NEEDLE.

More than a thousand years before our era, a people living in the
extremest eastern portions of Asia had magnetic carriages, on which the
movable arm of the figure of a man continually pointed to the south,
as a guide by which to find the way across the boundless grass-plains
of Tartary; nay, even in the third century of our era, therefore at
least 700 years before the use of the mariner’s compass in European
seas, Chinese vessels navigated the Indian Ocean under the direction of
Magnetic Needles pointing to the south.

  Now the Western nations, the Greeks and the Romans, knew that
  magnetism could be communicated to iron, and _that that metal_
  would retain it for a length of time. The great discovery of
  the terrestrial directive force depended, therefore, alone
  on this--that no one in the West had happened to observe an
  elongated fragment of magnetic iron-stone, or a magnetic iron rod,
  floating by the aid of a piece of wood in water, or suspended
  in the air by a thread, in such a position as to admit of free
  motion.--_Humboldt’s Cosmos_, vol. i.


KIRCHER’S “MAGNETISM.”

More than two centuries since, Athanasius Kircher published his strange
book on Magnetism, in which he anticipated the supposed virtue of
magnetic traction in the curative art, and advocated the magnetism
of the sun and moon, of the divining-rod, and showed his firm belief
in animal magnetism. “In speaking of the vegetable world,” says Mr.
Hunt, “and the remarkable processes by which the leaf, the flower,
and the fruit are produced, this sage brings forward the fact of the
diamagnetic (repelled by the magnet) character of the plant which was
in 1852 rediscovered; and he refers the motions of the sunflower, the
closing of the convolvulus, and the directions of the spiral formed
by the twining plants, to this particular influence.”[45] Nor were
Kircher’s anticipations random guesses, but the result of deductions
from experiment and observation; and the universality of magnetism is
now almost recognised by philosophers.


MINUTE MEASUREMENT OF TIME.

By observing the magnet in the highly-convenient and delicate manner
introduced by Gauss and Weber, which consists in attaching a mirror
to the magnet and determining the constant factor necessary to convert
the differences of oscillation into differences of time, Professor
Helmholtz has been able, with comparatively simple apparatus, to make
accurate determinations up to the 1/10000th part of a second.


POWER OF A MAGNET.

The Power of a Magnet is estimated by the weight its poles are able
to carry. Each pole singly is able to support a smaller weight than
when they both act together by means of a keeper, for which reason
horse-shoe magnets are superior to bar magnets of similar dimensions
and character. It has further been ascertained that small magnets have
a much greater relative force than large ones.

When magnetism is excited in a piece of steel in the ordinary mode, by
friction with a magnet, it would seem that its inductive power is able
to overcome the coercive power of the steel only to a certain depth
below the surface; hence we see why small pieces of steel, especially
if not very hard, are able to carry greater relative weights than large
magnets. Sir Isaac Newton wore in a ring a magnet weighing only 3
grains, which would lift 760 grains, _i. e._ 250 times its own weight.

Bar-magnets are seldom found capable of carrying more than their own
weight; but horse-shoe magnets of similar steel will bear considerably
more. Small ones of from half an ounce to 1 ounce in weight will carry
from 30 to 40 times their own weight; while such as weigh from 1 to 2
lbs. will rarely carry more than from 10 to 15 times their weight. The
writer found a 1 lb. horse-shoe magnet that he impregnated by means of
the feeder able to bear 26½ times its own weight; and Fischer, having
adopted the like mode of magnetising the steel, which he also carefully
heated, has made magnets of from 1 to 3 lbs. weight that would carry 30
times, and others of from 4 to 6 lbs. weight that would carry 20 times,
their own weight.--_Professor Peschel._


HOW ARTIFICIAL MAGNETS ARE MADE.

In 1750, Mr. Canton, F.R.S., “one of the most successful experimenters
in the golden age of electricity,”[46] communicated to the Royal
Society his “Method of making Artificial Magnets without the use
of natural ones.” This he effected by using a poker and tongs to
communicate magnetism to steel bars. He derived his first hint from
observing them one evening, as he was sitting by the fire, to be nearly
in the same direction with the earth as the dipping needle. He thence
concluded that they must, from their position and the frequent blows
they receive, have acquired some magnetic virtue, which on trial he
found to be the case; and therefore he employed them to impregnate his
bars, instead of having recourse to the natural loadstone. Upon the
reading of the above paper, Canton exhibited to the Royal Society his
experiments, for which the Copley Medal was awarded to him in 1751.

Canton had, as early as 1747, turned his attention, with complete
success, to the production of powerful artificial magnets, principally
in consequence of the expense of procuring those made by Dr. Gowan
Knight, who kept his process secret. Canton for several years abstained
from communicating his method even to his most intimate friends,
lest it might be injurious to Dr. Knight, who procured considerable
pecuniary advantages by touching needles for the mariner’s compass.

At length Dr. Knight’s method of making artificial magnets was
communicated to the world by Mr. Wilson, in a paper published in the
69th volume of the _Philosophical Transactions_. He provided himself
with a large quantity of clean iron-filings, which he put into a
capacious tub about half full of clear water; he then agitated the
tub to and fro for several hours, until the filings were reduced by
attrition to an almost impalpable powder. This powder was then dried,
and formed into paste by admixture with linseed-oil. The paste was then
moulded into convenient shapes, which were exposed to a moderate heat
until they had attained a sufficient degree of hardness.

  After allowing them to remain for some time in this state, Dr.
  Knight gave them their magnetic virtue in any direction he pleased,
  by placing them between the extreme ends of his large magazine of
  artificial magnets for a second or more, as he saw occasion. By
  this method the virtue they acquired was such, that when any one of
  these pieces was held between two of his best ten-guinea bars, with
  its poles purposely inverted, it immediately of itself turned about
  to recover its natural direction, which the force of those very
  powerful bars was not sufficient to counteract.

Dr. Knight’s powerful battery of magnets above mentioned is in the
possession of the Royal Society, having been presented by Dr. John
Fothergill in 1776.


POWER OF THE SUN’S RAYS IN INCREASING THE STRENGTH OF MAGNETS.

Professor Barlocci found that an armed natural loadstone, which would
carry 1½ Roman pounds, had its power nearly _doubled_ by twenty-four
hours’ exposure to the strong light of the sun. M. Zantedeschi found
that an artificial horse-shoe loadstone, which carried 13½ oz., carried
3½ more by three days’ exposure, and at last arrived to 31 oz. by
continuing it in the sun’s light. He found that while the strength
increased in oxidated magnets, it diminished in those which were not
oxidated, the diminution becoming insensible when the loadstone was
highly polished. He now concentrated the solar rays upon the loadstone
by means of a lens; and he found that, both in oxidated and polished
magnets, they _acquire_ strength when their _north_ pole is exposed
to the sun’s rays, and _lose_ strength when the _south_ pole is
exposed.--_Sir David Brewster._


COLOUR OF A BODY AND ITS MAGNETIC PROPERTIES.

Solar rays bleach dead vegetable matter with rapidity, while in living
parts of plants their action is frequently to strengthen the colour.
Their power is perhaps best seen on the sides of peaches, apples, &c.,
which, exposed to a midsummer’s sun, become highly coloured. In the
open winter of 1850, Mr. Adie, of Liverpool, found in a wallflower
plant proof of a like effect: in the dark months there was a slow
succession of one or two flowers, of uniform pale yellow hue; in March
streaks of a darker colour appeared on the flowers, and continued to
slowly increase till in April they were variegated brown and yellow,
of rich strong colours. On the supposition that these changes are
referable to magnetic properties, may hereafter be explained Mrs.
Somerville’s experiments on steel needles exposed to the sun’s rays
under envelopes of silk of various colours; the magnetisation of steel
needles has failed in the coloured rays of the spectrum, but Mr. Adie
considers that under dyed silk the effect will hinge on the chemical
change wrought in the silk and its dye by the solar rays.


THE ONION AND MAGNETISM.

A popular notion has long been current, more especially on the shores
of the Mediterranean, that if a magnetic rod be rubbed with an onion,
or brought in contact with the emanations of the plant, the directive
force will be diminished, while a compass thus treated will mislead the
steersman. It is difficult to conceive what could have given rise to so
singular a popular error.[47]--_Humboldt’s Cosmos_, vol. v.


DECLINATION OF THE NEEDLE--THE EARTH A MAGNET.

The Inclination or Dip of the Needle was first recorded by Robert
Norman, in a scarce book published in 1576 entitled _The New
Attractive; containing a short Discourse of the Magnet or Loadstone,
&c._

Columbus has not only the merit of being the first to discover _a
line without magnetic variation_, but also of having first excited a
taste for the study of terrestrial magnetism in Europe, by means of
his observations on the progressive increase of western declination in
receding from that line.

The first chart showing the variation of the compass,[48] or the
declination of the needle, based on the idea of employing curves drawn
through points of equal declination, is due to Halley, who is justly
entitled the father and founder of terrestrial magnetism. And it is
curious to find that in No. 195 of the _Philosophical Transactions_,
in 1683, Halley had previously expressed his belief that he has put it
past doubt that the globe of the earth is one great magnet, having four
magnetical poles or points of attraction, near each pole of the equator
two; and that in those parts of the world which lie near adjacent to
any one of those magnetical poles, the needle is chiefly governed
thereby, the nearest pole being always predominant over the more remote.

“To Halley” (says Sir John Herschel) “we owe the first appreciation
of the real complexity of the subject of magnetism. It is wonderful
indeed, and a striking proof of the penetration and sagacity of this
extraordinary man, that with his means of information he should
have been able to draw such conclusions, and to take so large and
comprehensive a view of the subject as he appears to have done.”

And, in our time, “the earth is a great magnet,” says Faraday: “its
power, according to Gauss, being equal to that which would be conferred
if every cubic yard of it contained six one-pound magnets; the sum of
the force is therefore equal to 8,464,000,000,000,000,000,000 such
magnets.”


THE AURORA BOREALIS.

Halley, upon his return from his voyage to verify his theory of the
variation of the compass, in 1700, hazarded the conjecture that the
Aurora Borealis is a magnetic phenomenon. And Faraday’s brilliant
discovery of the evolution of light by magnetism has raised Halley’s
hypothesis, enounced in 1714, to the rank of an experimental certainty.


EFFECT OF LIGHT ON THE MAGNET.

In 1854, Sir John Ross stated to the British Association, in proof of
the effect of every description of light on the magnet, that during
his last voyage in the _Felix_, when frozen in about one hundred miles
north of the magnetic pole, he concentrated the rays of the full moon
on the magnetic needle, when he found it was five degrees attracted by
it.


MAGNETO-ELECTRICITY.

In 1820, the Copley Medal was adjudicated to M. Oersted of Copenhagen,
“when,” says Dr. Whewell, “the philosopher announced that the
conducting-wire of a voltaic circuit acts upon a magnetic needle; and
thus recalled into activity that endeavour to connect magnetism with
electricity which, though apparently on many accounts so hopeful, had
hitherto been attended with no success. Oersted found that the needle
has a tendency to place itself at _right angles_ to the wire; a kind of
action altogether different from any which had been suspected.”


ELECTRO-MAGNETS OF THE HORSE-SHOE FORM

were discovered by Sturgeon in 1825. Of two Magnets made by a process
devised by M. Elias, and manufactured by M. Logemeur at Haerlem, one,
a single horse-shoe magnet weighing about 1 lb., lifts 28½ lbs.; the
other, a triple horse-shoe magnet of about 10 lbs. weight, is capable
of lifting about 150 lbs. Similar magnets are made by the same person
capable of supporting 5 cwt. In the process of making them, a helix of
copper and a galvanic battery are used. The smaller magnet has twice
the power expressed by Haecker’s formula for the best artificial steel
magnet.

Subsequently Henry and Ten Eyk, in America, constructed some
electro-magnets on a large scale. One horse-shoe magnet made by them,
weighing 60 lbs., would support more than 2000 lbs.

In September 1858, there were constructed for the Atlantic-telegraph
cable at Valentia two permanent magnets, from which the electric
induction is obtained: each is composed of 30 horse-shoe magnets, 2½
feet long and from 4 to 5 inches broad; the induction coils attached to
these each contain six miles of wire, and a shock from them, if passed
through the human body, would be sufficient to destroy life.


ROTATION-MAGNETISM.

The unexpected discovery of Rotation-Magnetism by Arago, in 1825,
has shown practically that every kind of matter is susceptible of
magnetism; and the recent investigations of Faraday on diamagnetic
substances have, under special conditions of meridian or equatorial
direction, and of solid, fluid, or gaseous inactive conditions of the
bodies, confirmed this important result.


INFLUENCE OF PENDULUMS ON EACH OTHER.

About a century since it became known, that when two clocks are in
action upon the same shelf, they will disturb each other: that the
pendulum of the one will stop that of the other; and that the pendulum
that was stopped will after a while resume its vibrations, and in its
turn stop that of the other clock. When two clocks are placed near
one another in cases very slightly fixed, or when they stand on the
boards of a floor, they will affect a little each other’s pendulum.
Mr. Ellicote observed that two clocks resting against the same rail,
which agreed to a second for several days, varied one minute thirty-six
seconds in twenty-four hours when separated. The slower, having a
longer pendulum, set the other in motion in 16-1/3 minutes, and stopped
itself in 36-2/3 minutes.


WEIGHT OF THE EARTH ASCERTAINED BY THE PENDULUM.

By a series of comparisons with Pendulums placed at the surface and
the interior of the Earth, the Astronomer-Royal has ascertained the
variation of gravity in descending to the bottom of a deep mine, as
the Harton coal-pit, near South Shields. By calculations from these
experiments, he has found the mean density of the earth to be 6·566,
the specific gravity of water being represented by unity. In other
words, it has been ascertained by these experiments that if the earth’s
mass possessed every where its average density, it would weigh, bulk
for bulk, 6·566 times as much as water. It is curious to note the
different values of the earth’s mean density which have been obtained
by different methods. The Schehallien experiment indicated a mean
density equal to about 4½; the Cavendish apparatus, repeated by Baily
and Reich, about 5½; and Professor Airy’s pendulum experiment furnishes
a value amounting to about 6½.

The immediate result of the computations of the Astronomer-Royal is:
supposing a clock adjusted to go true time at the top of the mine, it
would gain 2¼ seconds per day at the bottom. Or it may be stated thus:
that gravity is greater at the bottom of a mine than at the top by
1/19190th part.--_Letter to James Mather, Esq., South Shields._ See
also _Professor Airy’s Lecture_, 1854.


ORIGIN OF TERRESTRIAL MAGNETISM.

The earliest view of Terrestrial Magnetism supposed the existence
of a magnet at the earth’s centre. As this does not accord with the
observations on declination, inclination, and intensity, Tobias
Meyer gave this fictitious magnet an eccentric position, placing it
one-seventh part of the earth’s radius from the centre. Hansteen
imagined that there were two such magnets, different in position
and intensity. Ampère set aside these unsatisfactory hypotheses by
the view, derived from his discovery, that the earth itself is an
electro-magnet, magnetised by an electric current circulating about
it from east to west perpendicularly to the plane of the magnetic
meridian, to which the same currents give direction as well as
magnetise the ores of iron: the currents being thermo-electric
currents, excited by the action of the sun’s heat successively on the
different parts of the earth’s surface as it revolves towards the east.

William Gilbert,[49] who wrote an able work on magnetic and electric
forces in the year 1600, regarded terrestrial magnetism and electricity
as two emanations of a single fundamental source pervading all matter,
and he therefore treated of both at once. According to Gilbert’s idea,
the earth itself is a magnet; whilst he considered that the inflections
of the lines of equal declination and inclination depend upon the
distribution of mass, the configuration of continents, or the form and
extent of the deep intervening oceanic basins.

Till within the last eighty years, it appears to have been the received
opinion that the intensity of terrestrial magnetism was the same at
all parts of the earth’s surface. In the instructions drawn up by
the French Academy for the expedition under La Pérouse, the first
intimation is given of a contrary opinion. It is recommended that the
time of vibration of a dipping-needle should be observed at stations
widely remote, as a test of the equality or difference of the magnetic
intensity; suggesting also that such observations should particularly
be made at those parts of the earth where the dip was greatest and
where it was least. The experiments, whatever their results may have
been, which, in compliance with this recommendation, were made in the
expedition of La Pérouse, perished in its general catastrophe; but the
instructions survived.

In 1811, Hansteen took up the subject, and in 1819 published his
celebrated work, clearly demonstrating the fluctuations which this
element has undergone during the last two centuries; confirming in
great detail the position of Halley, that “the whole magnetic system is
in motion, that the moving force is very great as extending its effects
from pole to pole, and that its motion is not _per saltum_, but a
gradual and regular motion.”


THE NORTH AND SOUTH MAGNETIC POLES.

The knowledge of the geographical position of both Magnetic Poles is
due to the scientific energy of the same navigator, Sir James Ross.
His observations of the Northern Magnetic Pole were made during the
second expedition of his uncle, Sir John Ross (1829-1833); and of
the Southern during the Antarctic expedition under his own command
(1839-1843). The Northern Magnetic Pole, in 70° 5′ lat., 96° 43′ W.
long., is 5° of latitude farther from the ordinary pole of the earth
than the Southern Magnetic Pole, 75° 35′ lat., 154° 10′ E. long.;
whilst it is also situated farther west from Greenwich than the
Northern Magnetic Pole. The latter belongs to the great island of
Boothia Felix, which is situated very near the American continent,
and is a portion of the district which Captain Parry had previously
named North Somerset. It is not far distant from the western coast of
Boothia Felix, near the promontory of Adelaide, which extends into King
William’s Sound and Victoria Strait.

The Southern Magnetic Pole has been directly reached in the same manner
as the Northern Pole. On 17th February 1841, the _Erebus_ penetrated
as far as 76° 12′ S. lat., and 164° E. long. As the inclination was
here only 88° 40′, it was assumed that the Southern Magnetic Pole
was about 160 nautical miles distant. Many accurate observations of
declination, determining the intersection of the magnetic meridian,
render it very probable that the South Magnetic Pole is situated in the
interior of the great Antarctic region of South Victoria Land, west
of the Prince Albert mountains, which approach the South Pole and are
connected with the active volcano of Erebus, which is 12,400 feet in
height.--_Humboldt’s Cosmos_, vol. v.


MAGNETIC STORMS.

The mysterious course of the magnetic needle is equally affected by
time and space, by the sun’s course, and by changes of place on the
earth’s surface. Between the tropics the hour of the day may be known
by the direction of the needle as well as by the oscillations of the
barometer. It is affected instantly, but transiently, by the northern
light.

When the uniform horary motion of the needle is disturbed by a magnetic
storm, the perturbation manifests itself _simultaneously_, in the
strictest sense of the word, over hundreds and thousands of miles of
sea and land, or propagates itself by degrees in short intervals every
where over the earth’s surface.

Among numerous examples of perturbations occurring simultaneously and
extending over wide portions of the earth’s surface, one of the most
remarkable is that of September 25th, 1841, which was observed at
Toronto in Canada, at the Cape of Good Hope, at Prague, and partially
in Van Diemen’s Land. Sabine adds, “The English Sunday, on which it is
deemed sinful, after midnight on Saturday, to register an observation,
and to follow out the great phenomena of creation in their perfect
development, interrupted the observation in Van Diemen’s Land, where,
in consequence of the difference of the longitude, the magnetic storm
fell on Sunday.”

  It is but justice to add, that to the direct instrumentality of the
  British Association we are indebted for this system of observation,
  which would not have been possible without some such machinery
  for concerted action. It being known that the magnetic needle is
  subject to oscillations, the nature, the periods, and the laws
  of which were unascertained, under the direction of a committee
  of the Association _magnetic observatories_ were established in
  various places for investigating these strange disturbances. As
  might have been anticipated, regularly recurring perturbations were
  noted, depending on the hour of the day and the season of the year.
  Magnetic storms were observed to sweep simultaneously over the
  whole face of the earth, and these too have now been ascertained to
  follow certain periodic laws.

  But the most startling result of the combined magnetic observations
  is the discovery of marked perturbations recurring at intervals of
  ten years; a period which seemed to have no analogy to any thing
  in the universe, but which M. Schwabe has found to correspond
  with the variation of the spots on the sun, both attaining their
  maximum and minimum developments at the same time. Here, for the
  present, the discovery stops; but that which is now an unexplained
  coincidence may hereafter supply the key to the nature and source
  of Terrestrial Magnetism: or, as Dr. Lloyd observes, this system of
  magnetic observation has gone beyond our globe, and opened a new
  range for inquiry, by showing us that this wondrous agent has power
  in other parts of the solar system.


FAMILIAR GALVANIC EFFECTS.

By means of the galvanic agency a variety of surprising effects have
been produced. Gunpowder, cotton, and other inflammable substances have
been set on fire; charcoal has been made to burn with a brilliant white
flame; water has been decomposed into its elementary parts; metals
have been melted and set on fire; fragments of diamond, charcoal, and
plumbago have been dispersed as if evaporated; platina, the hardest
and the heaviest of the metals, has been melted as readily as wax in
the flame of a candle; the sapphire, quartz, magnesia, lime, and the
firmest compounds in nature, have been fused. Its effects on the animal
system are no less surprising.

The agency of galvanism explains why porter has a different and more
pleasant taste when drunk out of a pewter-pot than out of glass or
earthenware; why works of metal which are soldered together soon
tarnish in the place where the metals are joined; and why the copper
sheathing of ships, when fastened with iron nails, is soon corroded
about the place of contact. In all these cases a galvanic circle is
formed which produces the effects.


THE SIAMESE TWINS GALVANISED.

It will be recollected that the Siamese twins, brought to England in
the year 1829, were united by a jointed cartilaginous band. A silver
tea spoon being placed on the tongue of one of the twins and a disc of
zinc on the tongue of the other, the moment the two metals were brought
into contact both the boys exclaimed, “Sour, sour;” thus proving that
the galvanic influence passed from the one to the other through the
connecting band.


MINUTE AND VAST BATTERIES.

Dr. Wollaston made a simple apparatus out of a silver thimble, with its
top cut off. It was then partially flattened, and a small plate of zinc
being introduced into it, the apparatus was immersed in a weak solution
of sulphuric acid. With this minute battery, Dr. Wollaston was able to
fuse a wire of platinum 1/3000th of an inch in diameter--a degree of
tenuity to which no one had ever succeeded in drawing it.

Upon the same principle (that of introducing a plate of zinc between
two plates of other metals) Mr. Children constructed his immense
battery, the zinc plates of which measured six feet by two feet eight
inches; each plate of zinc being placed between two of copper, and each
triad of plates being enclosed in a separate cell. With this powerful
apparatus a wire of platinum, 1/10th of an inch in diameter and upwards
of five feet long, was raised to a red heat, visible even in the broad
glare of daylight.

The great battery at the Royal Institution, with which Sir Humphry Davy
discovered the composition of the fixed alkalies, was of immense power.
It consisted of 200 separate parts, each composed of ten double plates,
and each plate containing thirty-two square inches; the number of
double plates being 2000, and the whole surface 128,000 square inches.

Mr. Highton, C.E., has made a battery which exposes a surface of only
1/100th part of an inch: it consists of but one cell; it is less than
1/10000th part of a cubic inch, and yet it produces electricity more
than enough to overcome all the resistance in the inventor’s brother’s
patent Gold-leaf Telegraph, and works the same powerfully. It is, in
short, a battery which, although _it will go through the eye of a
needle_, will yet work a telegraph well. Mr. Highton had previously
constructed a battery in size less than 1/40th of a cubic inch: this
battery, he found, would for a month together ring a telegraph-bell ten
miles off.


ELECTRIC INCANDESCENCE OF CHARCOAL POINTS.

The most splendid phenomenon of this kind is the combustion of charcoal
points. Pointed pieces of the residuum obtained from gas retorts will
answer best, or Bunsen’s composition may be used for this purpose. Put
two such charcoal points in immediate contact with the wires of your
battery; bring the points together, and they will begin to burn with
a dazzling white light. The charcoal points of the large apparatus
belonging to the Royal Institution became incandescent at a distance of
1/30th of an inch; when the distance was gradually increased till they
were four inches asunder, they continued to burn with great intensity,
and a permanent stream of light played between them. Professor Bunsen
obtained a similar flame from a battery of four pairs of plates,
its carbon surface containing 29 feet. The heat of this flame is so
intense, that stout platinum wire, sapphire, quartz, talc, and lime
are reduced by it to the liquid form. It is worthy of remark, that no
combustion, properly so called, takes place in the charcoal itself,
which sustains only an extremely minute loss in its weight and becomes
rather denser at the points. The phenomenon is attended with a still
more vivid brightness if the charcoal points are placed in a vacuum,
or in any of those gases which are not supporters of combustion.
Instead of two charcoal points, one only need be used if the following
arrangement is adopted: lay the piece of charcoal on some quicksilver
that is connected with one pole of the battery, and complete the
circuit from the other pole by means of a strip of platinum. When
Professor Peschel used a piece of well-burnt coke in the manner just
described, he obtained a light which was almost intolerable to the eyes.


VOLTAIC ELECTRICITY.

On January 31, 1793, Volta announced to the Royal Society his discovery
of the development of electricity in metallic bodies. Galvani had given
the name of Animal Electricity to the power which caused spontaneous
convulsions in the limbs of frogs when the divided nerves were
connected by a metallic wire. Volta, however, saw the true cause of the
phenomena described by Galvani. Observing that the effects were far
greater when the connecting medium consisted of two different kinds
of metal, he inferred that the principle of excitation existed in the
metals, and not in the nerves of the animal; and he assumed that the
exciting fluid was ordinary electricity, produced by the contact of the
two metals; the convulsions of the frog consequently arose from the
electricity thus developed passing along its nerves and muscles.

In 1800 Volta invented what is now called the Voltaic Pile, or compound
Galvanic circle.

  The term Animal Electricity (says Dr. Whewell) has been superseded
  by others, of which _Galvanism_ is the most familiar; but I think
  that Volta’s office in this discovery is of a much higher and more
  philosophical kind than that of Galvani; and it would on this
  account be more fitting to employ the term _Voltaic Electricity_,
  which, indeed, is very commonly used, especially by our most
  recent and comprehensive writers. The _Voltaic pile_ was a more
  important step in the history of electricity than the Leyden jar
  had been--_Hist. Ind. Sciences_, vol. iii.

  No one who wishes to judge impartially of the scientific history
  of these times and of its leaders, will consider Galvani and
  Volta as equals, or deny the vast superiority of the latter over
  all his opponents or fellow-workers, more especially over those
  of the Bologna school. We shall scarcely again find in one man
  gifts so rich and so calculated for research as were combined
  in Volta. He possessed that “incomprehensible talent,” as Dove
  has called it, for separating the essential from the immaterial
  in complicated phenomena; that boldness of invention which must
  precede experiment, controlled by the most strict and cautious
  mode of manipulation; that unremitting attention which allows no
  circumstance to pass unnoticed; lastly, with so much acuteness,
  so much simplicity, so much grandeur of conception, combined with
  such depth of thought, he had a hand which was the hand of a
  workman.--_Jameson’s Journal_, No. 106.


THE VOLTAIC BATTERY AND THE GYMNOTUS.

“We boast of our Voltaic Batteries,” says Mr. Smee. “I should hardly
be believed if I were to say that I did not feel pride in having
constructed my own, especially when I consider the extensive operations
which it has conducted. But when I compare my battery with the battery
which nature has given to the electrical eel and the torpedo, how
insignificant are human operations compared with those of the Architect
of living beings! The stupendous electric eel in the Polytechnic
Institution, when he seeks to kill his prey, encloses him in a circle;
then, by volition, causes the voltaic force to be produced, and the
hapless creature is instantly killed. It would probably require ten
thousand of my artificial batteries to effect the same object, as
the creature is killed _instanter_ on receiving the shock. As much,
however, as my battery is inferior to that of the electric fish, so
is man superior to the same animal. Man is endowed with a power of
mind competent to appreciate the force of matter, and is thus enabled
to make the battery. The eel can but use the specific apparatus which
nature has bestowed upon it.”

Some observations upon the electric current around the gymnotus, and
notes of experiments with this and other electric fish, will be found
in _Things not generally Known_, p. 199.


VOLTAIC CURRENTS IN MINES.

Many years ago, Mr. R. W. Fox, from theory entertaining a belief
that a connection existed between voltaic action in the interior of
the earth and the arrangement of metalliferous veins, and also the
progressive increase of temperature in the strata as we descend from
the surface, endeavoured to verify the same from experiment in the mine
of Huel Jewel, in Cornwall. His apparatus consisted of small plates
of sheet-copper, which were fixed in contact with a plate in the veins
with copper nails, or else wedged closely against them with wooden
props stretched across the galleries. Between two of these plates,
at different stations, a communication was made by means of a copper
wire 1/20th of an inch in diameter, which included a galvanometer
in its circuit. In some instances 300 fathoms of copper wire were
employed. It was then found that the intensity of the voltaic current
was generally greater in proportion to the greater abundance of copper
ore in the veins, and in some degree to the depth of the stations.
Hence Mr. Fox’s discovery promised to be of practical utility to the
miner in discovering the relative quantity of ore in the veins, and the
directions in which it most abounds.

The result of extended experiments, mostly made by Mr. Robert Hunt,
has not, however, confirmed Mr. Fox’s views. It has been found that
the voltaic currents detected in the lodes are due to the chemical
decomposition going on there; and the more completely this process
of decomposition is established, the more powerful are the voltaic
currents. Meanwhile these have nothing whatever to do with the increase
of temperature with depth. Recent observations, made in the deep mines
of Cornwall under the direction of Mr. Fox, do not appear consistent
with the law of thermic increase as formerly established, the shallow
mines giving a higher ratio of increase than the deeper ones.


GERMS OF ELECTRIC KNOWLEDGE.

Two centuries and a half ago, Gilbert recognised that the property of
attracting light substances when rubbed, be their nature what it may,
is not peculiar to amber, which is a condensed earthy juice cast up by
the waves of the sea, and in which flying insects, ants, and worms lie
entombed as in eternal sepulchres. The force of attraction (Gilbert
continues) belongs to a whole class of very different substances, as
glass, sulphur, sealing-wax, and all resinous substances--rock crystal
and all precious stones, alum and rock-salt. Gilbert measured the
strength of the excited electricity by means of a small needle--not
made of iron--which moved freely on a pivot, and perfectly similar to
the apparatus used by Haüy and Brewster in testing the electricity
excited in minerals by heat and friction. “Friction,” says Gilbert
further, “is productive of a stronger effect in dry than in humid air;
and rubbing with silk cloths is most advantageous.”

Otto von Guerike, the inventor of the air-pump, was the first who
observed any thing more than mere phenomena of attraction. In his
experiments with a rubbed piece of sulphur he recognised the
phenomena of repulsion, which subsequently led to the establishment
of the laws of the sphere of action and of the distribution of
electricity. _He heard the first sound, and saw the first light, in
artificially-produced electricity._ In an experiment instituted by
Newton in 1675, the first traces of an electric charge in a rubbed
plate of glass were seen.


TEMPERATURE AND ELECTRICITY.

Professor Tyndall has shown that all variations of temperature, in
metals at least, excite electricity. When the wires of a galvanometer
are brought in contact with the two ends of a heated poker, the prompt
deflection of the galvanometer-needle indicates that a current of
electricity has been sent through the instrument. Even the two ends of
a spoon, one of which has been dipped in hot water, serve to develop an
electric current; and in cutting a hot beefsteak with a steel knife and
a silver fork there is an excitement of electricity. The mere heat of
the finger is sufficient to cause the deflection of the galvanometer;
and when ice is applied to the part that has been previously warmed,
the galvanometer-needle is deflected in the contrary direction. A small
instrument invented by Melloni is so extremely sensitive of the action
of heat, that electricity is excited when the hand is held six inches
from it.


VAST ARRANGEMENT OF ELECTRICITY.

Professor Faraday has shown that the Electricity which decomposes,
and that which is evolved in the decomposition of, a certain quantity
of matter, are alike. What an enormous quantity of electricity,
therefore, is required for the decomposition of a single grain of
water! It must be in quantity sufficient to sustain a platinum wire
1/104th of an inch in thickness red-hot in contact with the air
for three minutes and three-quarters. It would appear that 800,000
charges of a Leyden battery, charged by thirty turns of a very large
and powerful plate-machine in full action, are necessary to supply
electricity sufficient to decompose a single grain of water, or to
equal the quantity of electricity which is naturally associated with
the elements of that grain of water, endowing them with their mutual
chemical affinity. Now the above quantity of electricity, if passed at
once through the head of a rat or a cat, would kill it as by a flash of
lightning. The quantity is, indeed, equal to that which is developed
from a charged thunder-cloud.


DECOMPOSITION OF WATER BY ELECTRICITY.

Professor Andrews, by an ingenious arrangement, is enabled to show that
water is decomposed by the common machine; and by using an electrical
kite, he was able, in fine weather, to produce decomposition, although
so slowly that only 1/700000th of a grain of water was decomposed per
hour. Faraday has proved that the decomposition of one single grain of
water produces more electricity than is contained in the most powerful
flash of lightning.


ELECTRICITY IN BREWING.

Mr. Black, a practical writer upon Brewing, has found that by the
practice of imbedding the fermentation-vats in the earth, and
connecting them by means of metallic pipes, an electrical current
passes through the beer and causes it to turn sour. As a preventive,
he proposed to place the vats upon wooden blocks, or on any other
non-conductors, so that they may be insulated. It has likewise been
ascertained that several brewers who had brewed excellent ale on the
south side of the street, on removing to the north have failed to
produce good ale.


ELECTRIC PAPER.

Professor Schonbein has prepared paper, as transparent as glass and
impermeable to water, which develops a very energetic electric force.
By placing some sheets on each other, and simply rubbing them once or
twice with the hand, it becomes difficult to separate them. If this
experiment is performed in the dark, a great number of distinct flashes
may be perceived between the separated surfaces. The disc of the
electrophorus, placed on a sheet that has been rubbed, produces sparks
of some inches in length. A thin and very dry sheet of paper, placed
against the wall, will adhere strongly to it for several hours if the
hand be passed only once over it. If the same sheet be passed between
the thumb and fore-finger in the dark, a luminous band will be visible.
Hence with this paper may be made powerful and cheap electrical
machines.


DURATION OF THE ELECTRIC SPARK.

By means of Professor Wheatstone’s apparatus, the Duration
of the Electric Spark has been ascertained not to exceed the
twenty-five-thousandth part of a second. A cannon-ball, if illumined
in its flight by a flash of lightning, would, in consequence of the
momentary duration of the light, appear to be stationary, and even the
wings of an insect, that move ten thousand times in a second, would
seem at rest.


VELOCITY OF ELECTRIC LIGHT.

On comparing the velocities of solar, stellar, and terrestrial light,
which are all equally refracted in the prism, with the velocity of the
light of frictional electricity, we are disposed, in accordance with
Wheatstone’s ingeniously-conducted experiments, to regard the lowest
ratio in which the latter excels the former as 3:2. According to the
lowest results of Wheatstone’s apparatus, electric light traverses
288,000 miles in a second. If we reckon 189,938 miles for stellar
light, according to Struve, we obtain the difference of 95,776 miles as
the greater velocity of electricity in one second.

From the experiment described in Wheatstone’s paper (_Philosophical
Transactions_ for 1834), it would appear that the human eye is capable
of perceiving phenomena of light whose duration is limited to the
millionth part of a second.

In Professor Airy’s experiments with the electric telegraph to
determine the difference of longitude between Greenwich and Brussels,
the time spent by the electric current in passing from one observatory
to the other (270 miles) was found to be 0·109″ or rather more than
_the ninth part of a second_; and this determination rests on 2616
observations: a speed which would “girdle the globe” in ten seconds.


IDENTITY OF ELECTRIC AND MAGNETIC ATTRACTION.

This vague presentiment of the ancients has been verified in our own
times. “When electrum (amber),” says Pliny, “is animated by friction
and heat, it will attract bark and dry leaves precisely as the
loadstone attracts iron.” The same words may be found in the literature
of an Asiatic nation, and occur in a eulogium on the loadstone by the
Chinese physicist Knopho, in the fourth century: “The magnet attracts
iron as amber does the smallest grain of mustard-seed. It is like
a breath of wind, which mysteriously penetrates through both, and
communicates itself with the rapidity of an arrow.”

  Humboldt observed with astonishment on the woody banks of the
  Orinoco, in the sports of the natives, that the excitement of
  electricity by friction was known to these savage races. Children
  may be seen to rub the dry, flat, and shining seeds or husks of a
  trailing plant until they are able to attract threads of cotton
  and pieces of bamboo-cane. What a chasm divides the electric
  pastime of these naked copper-coloured Indians from the discovery
  of a metallic conductor discharging its electric shocks, or a
  pile formed of many chemically-decomposing substances, or a
  light-engendering magnetic apparatus! In such a chasm lie buried
  thousands of years, that compose the history of the intellectual
  development of mankind.--_Humboldt’s Cosmos_, vol. i.


THEORY OF THE ELECTRO-MAGNETIC ENGINE.

Several years ago a speculative American set the industrial world of
Europe in excitement by this proposition. The Magneto-Electric Machines
often made use of in the case of rheumatic disorders are well known. By
imparting a swift rotation to the magnet of such a machine, we obtain
powerful currents of electricity. If these be conducted through water,
the latter will be reduced to its two components, oxygen and hydrogen.
By the combustion of hydrogen water is again generated. If this
combustion takes place, not in atmospheric air, in which oxygen only
constitutes a fifth part, but in pure oxygen, and if a bit of chalk be
placed in the flame, the chalk will be raised to a white heat, and give
us the sun-like Drummond light: at the same time the flame develops a
considerable quantity of heat. Now the American inventor proposed to
utilise in this way the gases obtained from electrolytic decomposition;
and asserted that by the combustion a sufficient amount of heat was
generated to keep a small steam-engine in action, which again drove his
magneto-electric machine, decomposed the water, and thus continually
prepared its own fuel. This would certainly have been the most splendid
of all discoveries,--a perpetual motion which, besides the force that
kept it going, generated light like the sun, and warmed all around it.
The affair, however, failed, as was predicted by those acquainted with
the physical investigations which bear upon the subject.--_Professor
Helmholtz._


MAGNETIC CLOCK AND WATCH.

In the Museum of the Royal Society are two curiosities of the
seventeenth century which are objects of much interest in association
with the electric discoveries of our day. These are a Clock, described
by the Count Malagatti (who accompanied Cosmo III., Grand Duke of
Tuscany, to inspect the Museum in 1669) as more worthy of observation
than all the other objects in the cabinet. Its “movements are derived
from the vicinity of a loadstone, and it is so adjusted as to discover
the distance of countries at sea by the longitude.” The analogy
between this clock and the electric clock of the present day is very
remarkable. Of kindred interest is “Hook’s Magnetic Watch,” often
alluded to in the Royal Society’s Journal-book of 1669 as “going slower
or faster according to the greater or less distance of the loadstone,
and so moving regularly in any posture.”


WHEATSTONE’S ELECTRO-MAGNETIC CLOCK.

In this ingenious invention, the object of Professor Wheatstone was
to enable a simple clock to indicate exactly the same time in as many
different places, distant from each other, as may be required. A
standard clock in an observatory, for example, would thus keep in order
another clock in each apartment, and that too with such accuracy, that
_all of them, however numerous, will beat dead seconds audibly with as
great precision as the standard astronomical time-piece with which
they are connected_. But, besides this, the subordinate time-pieces
thus regulated require none of the mechanism for maintaining or
regulating the power. They consist simply of a face, with its second,
minute, and hour hands, and a train of wheels which communicate motion
from the action of the second-hand to that of the hour-hand, in the
same manner as an ordinary clock-train. Nor is this invention confined
to observatories and large establishments. The great horologe of St.
Paul’s might, by a suitable network of wires, or even by the existing
metallic pipes of the metropolis, be made to command and regulate all
the other steeple-clocks in the city, and even every clock within the
precincts of its metallic bounds. As railways and telegraphs extend
from London nearly to the remotest cities and villages, the sensation
of time may be transmitted along with the elements of language; and
the great cerebellum of the metropolis may thus constrain by its
sympathies, and regulate by its power, the whole nervous system of the
empire.


HOW TO MAKE A COMMON CLOCK ELECTRIC.

M. Kammerer of Belgium effects this by an addition to any clock
whereby it is brought into contact with the two poles of a galvanic
battery, the wires from which communicate with a drum moved by the
clockwork; and every fifteen seconds the current is changed, the
positive and the negative being transmitted alternately. A wire
is continued from the drum to the electric clock, the movement of
which, through the plate-glass dial, is seen to be two pairs of small
straight electro-magnets, each pair having their ends opposite to the
other pair, with about half an inch space between. Within this space
there hangs a vertical steel bar, suspended from a spindle at the
top. The rod has two slight projections on each side parallel to the
ends of the wire-coiled magnets. When the electric current comes on
the wire from the positive end of the battery (through the drum of
the regulator-clock) the positive magnets attract the bar to it, the
distance being perhaps the sixteenth of an inch. When, at the end of
fifteen seconds, the negative pole operates, repulsion takes effect,
and the bar moves to the opposite side. This oscillating bar gives
motion to a wheel which turns the minute and hour hands.

M. Kammerer states, that if the galvanic battery be attached to any
particular standard clock, any number of clocks, wherever placed, in a
city or kingdom, and communicating with this by a wire, will indicate
precisely the same time. Such is the precision, that the sounds
of three clocks thus beating simultaneously have been mistaken as
proceeding from one clock.


DR. FRANKLIN’S ELECTRICAL KITE.

Several philosophers had observed that lightning and electricity
possessed many common properties; and the light which accompanied
the explosion, the crackling noise made by the flame, and other
phenomena, made them suspect that lightning might be electricity in
a highly powerful state. But this connection was merely the subject
of conjecture until, in the year 1750, Dr. Franklin suggested an
experiment to determine the question. While he was waiting for the
building of a spire at Philadelphia, to which he intended to attach
his wire, the experiment was successfully made at Marly-la-Ville, in
France, in the year 1752; when lightning was actually drawn from the
clouds by means of a pointed wire, and it was proved to be really the
electric fluid.

  Almost every early electrical discovery of importance was made by
  Fellows of the Royal Society, and is to be found recorded in the
  _Philosophical Transactions_. In the forty-fifth volume occurs the
  first mention of Dr. Franklin’s name, and his theory of positive
  and negative electricity. In 1756 he was elected into the Society,
  “without any fee or other payment.” His previous communications
  to the _Transactions_, particularly the account of his electrical
  kite, had excited great interest. (_Weld’s History of the
  Royal Society._) It is thus described by him in a letter dated
  Philadelphia, October 1, 1752:

  “As frequent mention is made in the public papers from Europe
  of the success of the Marly-la-Ville experiment for drawing the
  electric fire from clouds by means of pointed rods of iron erected
  on high buildings, &c., it may be agreeable to the curious to be
  informed that the same experiment has succeeded in Philadelphia,
  though made in a different and more easy manner, which any one may
  try, as follows:

  Make a small cross of two light strips of cedar, the arms so
  long as to reach to the four corners of a large thin silk
  handkerchief when extended. Tie the comers of the handkerchief
  to the extremities of the cross; so you have the body of a kite,
  which, being properly accommodated with a tail, loop, and string,
  will rise in the air like a kite made of paper; but this, being of
  silk, is fitter to bear the wet and wind of a thunder-gust without
  tearing. To the top of the upright stick of the cross is to be
  fixed a very sharp-pointed wire, rising a foot or more above the
  wood. To the end of the twine, next the band, is to be tied a silk
  ribbon; and where the twine and silk join a key may be fastened.

  The kite is to be raised when a thunder-gust appears to be coming
  on, and the person who holds the string must stand within a door
  or window, or under some cover, so that the silk ribbon may not be
  wet; and care must be taken that the twine does not touch the frame
  of the door or window. As soon as any of the thunder-clouds come
  over the kite, the pointed wire will draw the electric fire from
  them; and the kite, with all the twine, will be electrified; and
  the loose filaments of the twine will stand out every way, and be
  attracted by an approaching finger.

  When the rain has wet the kite and twine, so that it can conduct
  the electric fire freely, you will find it stream out plentifully
  from the key on the approach of your knuckle. At this key the phial
  may be charged; and from electric fire thus obtained spirits may
  be kindled, and all the other electrical experiments be performed
  which are usually done by the help of a rubbed-glass globe or tube;
  and thus the sameness of the electric matter with that of lightning
  is completely demonstrated.”--_Philosophical Transactions._

Of all this great man’s (Franklin’s) scientific excellencies, the most
remarkable is the smallness, the simplicity, the apparent inadequacy
of the means which he employed in his experimental researches. His
discoveries were all made with hardly any apparatus at all; and if
at any time he had been led to employ instruments of a somewhat less
ordinary description, he never rested satisfied until he had, as it
were, afterwards translated the process by resolving the problem with
such simple machinery that you might say he had done it wholly unaided
by apparatus. The experiments by which the identity of lightning and
electricity was demonstrated were made with a sheet of brown paper, a
bit of twine or silk thread, and an iron key!--_Lord Brougham._[50]


FATAL EXPERIMENT WITH LIGHTNING.

These experiments are not without danger; and a flash of lightning has
been found to be a very unmanageable instrument. In 1753, M. Richman,
at St. Petersburg, was making an experiment of this kind by drawing
lightning into his room, when, incautiously bringing his head too near
the wire, he was struck dead by the flash, which issued from it like a
globe of blue fire, accompanied by a dreadful explosion.


FARADAY’S ELECTRICAL ILLUSTRATIONS.

The following are selected from the very able series of lectures
delivered by Professor Faraday at the Royal Institution:

  _The Two Electricities._--After having shown by various experiments
  the attractions and repulsions of light substances from excited
  glass and from an excited tube of gutta-percha, Professor Faraday
  proceeds to point out the difference in the character of the
  electricity produced by the friction of the two substances. The
  opposite characters of the electricity evolved by the friction
  of glass and of that excited by the friction of gutta-percha
  and shellac are exhibited by several experiments, in which the
  attraction of the positive and negative electricities to each other
  and the neutralisation of electrical action on the combination
  of the two forces are distinctly observable. Though adopting the
  terms “positive” and “negative” in distinguishing the electricity
  excited by glass from that excited by gutta-percha and resinous
  bodies, Professor Faraday is strongly opposed to the Franklinian
  theory from which these terms are derived. According to Franklin’s
  view of the nature of electrical excitement, it arises from the
  disturbance, by friction or other means, of the natural quantity
  of one electric fluid which is possessed by all bodies; an excited
  piece of glass having more than its natural share, which has
  been taken from the rubber, the latter being consequently in a
  minus or negative state. This theory Professor Faraday considers
  to be opposed to the distinct characteristic actions of the two
  forces; and, in his opinion, it is impossible to deprive any body
  of electricity, and reduce it to the minus state of Franklin’s
  hypothesis. Taking a Zamboni’s pile, he applies its two ends
  separately to an electrometer, to show that each end produces
  opposite kinds of electricity, and that the zero, or absence of
  electrical excitement, only exists in the centre of the pile. To
  prove how completely the two electricities neutralise each other,
  an excited rod of gutta-percha and the piece of flannel with which
  it has been rubbed are laid on the top of the electrometer without
  any sign of electricity whilst they are together; but when either
  is removed, the gold leaves diverge with positive and negative
  electricity alternately. The Professor dwells strongly on the
  peculiarity of the dual force of electricity, which, in respect
  of its duality, is unlike any other force in nature. He then
  contrasts its phenomena of instantaneous conduction with those of
  the somewhat analogous force of heat; and he illustrates by several
  striking experiments the peculiar property which static electricity
  possesses of being spread only over the surfaces of bodies. A metal
  ice-pail is placed on an insulated stand and electrified, and a
  metal ball suspended by a string is introduced, and touches the
  bottom and sides without having any electricity imparted to it,
  but on touching the outside it becomes strongly electrical. The
  experiment is repeated with a wooden tub with the same result;
  and Professor Faraday mentions the still more remarkable manner
  in which he has proved the surface distribution of electricity
  by having a small chamber constructed and covered with tinfoil,
  which can be insulated; and whilst torrents of electricity are
  being evolved from the external surface, he enters it with a
  galvanometer, and cannot perceive the slightest manifestation of
  electricity within.

  _The Two Threads._--A curious experiment is made with two kinds
  of thread used as the conducting force. From the electric machine
  on the table a silk thread is first carried to the indicator a
  yard or two off, and is shown to be a non-conductor when the glass
  tube is rubbed and applied to the machine (although the silk, when
  wetted, conducted); while a metallic thread of the same thickness,
  when treated in the same way, conducts the force so much as to
  vehemently agitate the gold leaves within the indicator.

  _Non-conducting Bodies._--The action that occurs in bodies which
  cannot conduct is the most important part of electrical science.
  The principle is illustrated by the attraction and repulsion of
  an electrified ball of gilt paper by a glass tube, between which
  and the ball a sheet of shellac is suspended. The nearer a ball of
  another description--an unelectrical insulated body--is brought
  to the Leyden jar when charged, the greater influence it is seen
  to possess over the gold leaf within the indicator, by induction,
  not by conduction. The questions, how electricities attract each
  other, what kind of electricity is drawn from the machine to the
  hand, how the hand was electric, are thus illustrated. To show the
  divers operations of this wonderful force, a tub (a bad conductor)
  is placed by the electric machine. When the latter is charged, a
  ball, having been electrified from it, is held in the tub, and
  rattles against its sides and bottom. On the application of the
  ball to the indicator, the gold leaf is shown not to move, whereas
  it is agitated manifestly when the same process is gone through
  with the exception that the ball is made to touch the outside only
  of the tub. Similar experiments with a ball in an ice-pail and
  a vessel of wire-gauze, into the latter of which is introduced a
  mouse, which is shown to receive no shock, and not to be frightened
  at all; while from the outside of the vessel electric sparks are
  rapidly produced. This latter demonstration proves that, as the
  mouse, so men and women, might be safe inside a building with
  proper conductors while lightning played about the exterior. The
  wire-gauze being turned inside out, the principle is shown to be
  irreversible in spite of the change--what has been the unelectrical
  inside of the vessel being now, when made the outside portion,
  capable of receiving and transmitting the power, while the original
  outside is now unelectrical.

  _Repulsion of Bodies._--A remarkable and playful experiment, by
  which the repulsion of bodies similarly electrified is illustrated,
  consists in placing a basket containing a heap of small pieces
  of paper on an insulated stand, and connecting it with the prime
  conductor of the electrical machine; when the pieces of paper
  rise rapidly after each other into the air, and descend on the
  lecture-table like a fall of snow. The effect is greatly increased
  when a metal disc is substituted for the basket.


ORIGIN OF THE LEYDEN JAR.

Muschenbroek and Linnæus had made various experiments of a strong kind
with water and wire. The former, as appears from a letter of his to
Réaumur, filled a small bottle with water, and having corked it up,
passed a wire through the cork into the bottle. Having rubbed the
vessel on the outside and suspended it to the electric machine, he was
surprised to find that on trying to pull the wire out he was subjected
to an awfully severe shock in his joints and his whole body, such as he
declared he would not suffer again for any experiment. Hence the Leyden
jar, which owes its name to the University of Leyden, with which, we
believe, Muschenbroek was connected.--_Faraday._


DANGER TO GUNPOWDER MAGAZINES.

By the illustration of a gas globule, which is ignited from a spark by
induction, Mr. Faraday has proved in a most interesting manner that the
corrugated-iron roofs of some gunpowder-magazines,--on the subject of
which he had often been consulted by the builders, with a view to the
greater safety of these manufactories,--are absolutely dangerous by the
laws of induction; as, by the return of induction, while a storm was
discharging itself a mile or two off, a secondary spark might ignite
the building.


ARTIFICIAL CRYSTALS AND MINERALS.--“THE CROSSE MITE.”

Among the experimenters on Electricity in our time who have largely
contributed to the “Curiosities of Science,” Andrew Crosse is entitled
to special notice. In his school-days he became greatly attached to the
study of electricity; and on settling on his paternal estate, Fyne
Court, on the Quantock Hills in Somersetshire, he there devoted himself
to chemistry, mineralogy, and electricity, pursuing his experiments
wholly independently of theories, and searching only for facts. In
Holwell Cavern, near his residence, he observed the sides and the roof
covered with Arragonite crystallisations, when his observations led
him to conclude that the crystallisations were the effects, at least
to some extent, of electricity. This induced him to make the attempt
to form artificial crystals by the same means, which he began in 1807.
He took some water from the cave, filled a tumbler, and exposed it to
the action of a voltaic battery excited by water alone, letting the
platinum-wires of the battery fall on opposite sides of the tumbler
from the opposite poles of the battery. After ten days’ constant
action, he produced crystals of carbonate of lime; and on repeating
the experiment in the dark, he produced them in six days. Thus Mr.
Crosse simulated in his laboratory one of the hitherto most mysterious
processes of nature.

He pursued this line of research for nearly thirty years at Fyne Court,
where his electrical-room and laboratory were on an enormous scale:
the apparatus had cost some thousands of pounds, and the house was
nearly full of furnaces. He carried an insulated wire above the tops
of the trees around his house to the length of a mile and a quarter,
afterwards shortened to 1800 feet. By this wire, which was brought
into connection with the apparatus in a chamber, he was enabled to see
continually the changes in the state of the atmosphere, and could use
the fluid so collected for a variety of purposes. In 1816, at a meeting
of country gentlemen, he prophesied that, “by means of electrical
agency, we shall be able to communicate our thoughts simultaneously
with the uttermost ends of the earth.” Still, though he foresaw
the powers of the medium, he did not make any experiments in that
direction, but confined himself to the endeavour to produce crystals
of various kinds. He ultimately obtained forty-one mineral crystals,
or minerals uncrystallised, in the form in which they are produced by
nature, including one sub-sulphate of copper--an entirely new mineral,
neither found in nature nor formed by art previously. His belief was
that even diamonds might be produced in this way.

Mr. Crosse worked alone in his retreat until 1836, when, attending
the meeting of the British Association at Bristol, he was induced to
explain his experiments, for which he was highly complimented by Dr.
Buckland, Dr. Dalton, Professor Sedgwick, and others.[51]

Shortly after Mr. Crosse’s return to Fyne Court, while pursuing his
experiments for forming crystals from a highly caustic solution out
of contact with atmospheric air, he was greatly surprised by the
appearance of an insect. Black flint, burnt to redness and reduced to
powder, was mixed with carbonate of potash, and exposed to a strong
heat for fifteen minutes; and the mixture was poured into a black-lead
crucible in an air furnace. It was reduced to powder while warm,
mixed with boiling water, kept boiling for some minutes, and then
hydrochloric acid was added to supersaturation. After being exposed
to voltaic action for twenty-six days, a perfect insect of the Acari
tribe made its appearance, and in the course of a few weeks about a
hundred more. The experiment was repeated in other chemical fluids
with the like results; and Mr. Weeks of Sandwich afterwards produced
the Acari inferrocyanerret of potassium. The Acarus of Mr. Crosse was
found to contribute a new species of that genus, nearly approaching
the Acari found in cheese and flour, or more nearly, Hermann’s _Acarus
dimidiatus_.

This discovery occasioned great excitement. The possibility was denied,
though Mr. Faraday is said to have stated in the same year that he had
seen similar appearances in his own electrical experiments. Mr. Crosse
was now accused of impiety and aiming at creation, to which attacks he
thus replied:

  As to the appearance of the acari under long-continued electrical
  action, I have never in thought, word, or deed given any one a
  right to suppose that I considered them as a creation, or even as a
  formation, from inorganic matter. To create is to form a something
  out of a nothing. To annihilate is to reduce that something to
  a nothing. Both of these, of course, can only be the attributes
  of the Almighty. In fact, I can assure you most sacredly that I
  have never dreamed of any theory sufficient to account for their
  appearance. I confess that I was not a little surprised, and am so
  still, and quite as much as I was when the acari made their first
  appearance. Again, I have never claimed any merit as attached to
  these experiments. It was a matter of chance; I was looking for
  silicious formations, and animal matter appeared instead.

These Acari, if removed from their birthplace, lived and propagated;
but uniformly died on the first recurrence of frost, and were entirely
destroyed if they fell back into the fluid whence they arose.

One of Mr. Crosse’s visitors thus describes the vast electrical room at
Fyne Court:

  Here was an immense number of jars and gallipots, containing fluids
  on which electricity was operating for the production of crystals.
  But you are startled in the midst of your observations by the smart
  crackling sound that attends the passage of the electrical spark;
  you hear also the rumbling of distant thunder. The rain is already
  plashing in great drops against the glass, and the sound of the
  passing sparks continues to startle your ear; you see at the window
  a huge brass conductor, with a discharging rod near it passing into
  the floor, and from the one knob to the other sparks are leaping
  with increasing rapidity and noise, every one of which would kill
  twenty men at one blow, if they were linked together hand in hand
  and the spark sent through the circle. From this conductor wires
  pass off without the window, and the electric fluid is conducted
  harmlessly away. Mr. Crosse approached the instrument as boldly as
  if the flowing stream of fire were a harmless spark. Armed with
  his insulated rod, he sent it into his batteries: having charged
  them, he showed how wire was melted, dissipated in a moment, by its
  passage; how metals--silver, gold, and tin--were inflamed and burnt
  like paper, only with most brilliant hues. He showed you a mimic
  aurora and a falling-star, and so proved to you the cause of those
  beautiful phenomena.

Mr. Crosse appears to have produced in all “about 200 varieties of
minerals, exactly resembling in all respects similar ones found in
nature.” He tried also a new plan of extracting gold from its ores
by an electrical process, which succeeded, but was too expensive
for common use. He was in the habit of saying that he could, like
Archimedes, move the world “if he were able to construct a battery at
once cheap, powerful, and durable.” His process of extracting metals
from their ores has been patented. Among his other useful applications
of electricity are the purifying by its means of brackish or sea-water,
and the improving bad wine and brandy. He agreed with Mr. Quekett
in thinking that it is by electrical action that silica and other
mineral substances are carried into and assimilated by plants. Negative
electricity Mr. Crosse found favourable to no plants except fungi;
and positive electricity he ascertained to be injurious to fungi, but
favourable to every thing else.

Mr. Crosse died in 1855. His widow has published a very interesting
volume of _Memorials_ of the ingenious experimenter, from which we
select the following:

  On one occasion Mr. Crosse kept a pair of soles under the electric
  action for three months; and at the end of that time they were
  sent to a friend, whose domestics knew nothing of the experiment.
  Before the cook dressed them, her master asked her whether she
  thought they were fresh, as he had some doubts. She replied that
  she was sure they were fresh; indeed, she said she could swear
  that they were alive yesterday! When served at table they appeared
  like ordinary fish; but when the family attempted to eat them,
  they were found to be perfectly tasteless--the electric action had
  taken away all the essential oil, leaving the fish unfit for food.
  However, the process is exceedingly useful for keeping fish, meat,
  &c. fresh and _good_ for ten days or a fortnight. I have never
  heard a satisfactory explanation of the cause of the antiseptic
  power communicated to water by the passage of the electric current.
  Whether ozone has not something to do with it, may be a question.
  The same effect is produced whichever two dissimilar metals are
  used.




The Electric Telegraph.


ANTICIPATIONS OF THE ELECTRIC TELEGRAPH.

The great secret of ubiquity, or at least of instantaneous
transmission, has ever exercised the ingenuity of mankind in various
romantic myths; and the discovery of certain properties of the
loadstone gave a new direction to these fancies.

The earliest anticipation of the Electric Telegraph of this purely
fabulous character forms the subject of one of the _Prolusiones
Academicæ_ of the learned Italian Jesuit Strada, first published at
Rome in the year 1617. Of this poem a free translation appeared in
1750. Strada’s fancy was this: “There is,” he supposes, “a species of
loadstone which possesses such virtue, that if two needles be touched
with it, and then balanced on separate pivots, and the one be turned in
a particular direction, the other will sympathetically move parallel
to it. He then directs each of these needles to be poised and mounted
parallel on a dial having the letters of the alphabet arranged round
it. Accordingly, if one person has one of the dials, and another the
other, by a little pre-arrangement as to details a correspondence can
be maintained between them at any distance by simply pointing the
needles to the letters of the required words. Strada, in his poetical
reverie, dreamt that some such sympathy might one day be found to hold
up the Magnesian Stone.”

Strada’s conceit seems to have made a profound impression on the
master-minds of the day. His poem is quoted in many works of the
seventeenth and eighteenth centuries; and Bishop Wilkins, in his book
on Cryptology, is strangely afraid lest his readers should mistake
Strada’s fancy for fact. Wilkins writes: “This invention is altogether
imaginary, having no foundation in any real experiment. You may see it
frequently confuted in those that treat concerning magnetical virtues.”

Again, Addison, in the 241st No. of the _Spectator_, 1712, describes
Strada’s “Chimerical correspondence,” and adds that, “if ever this
invention should be revived or put in practice,” he “would propose
that upon the lover’s dial-plate there should be written not only the
four-and-twenty letters, but several entire words which have always a
place in passionate epistles, as flames, darts, die, language, absence,
Cupid, heart, eyes, being, drown, and the like. This would very much
abridge the lover’s pains in this way of writing a letter, as it would
enable him to express the most useful and significant words with a
single touch of the needle.”

After Strada and his commentators comes Henry Van Etten, who shows how
“Claude, being at Paris, and John at Rome, might converse together, if
each had a needle touched by a stone of such virtue that as one moved
itself at Paris the other should be moved at Rome:” he adds, “it is
a fine invention, but I do not think there is a magnet in the world
which has such virtue; besides, it is inexpedient, for treasons would
be too frequent and too much protected. (_Recréations Mathématiques_:
see 5th edition, Paris, 1660, p. 158.) Sir Thomas Browne refers
to this “conceit” as “excellent, and, if the effect would follow,
somewhat divine;” but he tried the two needles touched with the same
loadstone, and placed in two circles of letters, “one friend keeping
one and another the other, and agreeing upon an hour when they will
communicate,” and found the tradition a failure that, “at what distance
of place soever, when one needle shall be removed unto any letter, the
other, by a wonderful sympathy, will move unto the same.” (See _Vulgar
Errors_, book ii. ch. iii.)

Glanvill’s _Vanity of Dogmatizing_, a work published in 1661, however,
contains the most remarkable allusion to the prevailing telegraphic
fancy. Glanvill was an enthusiast, and he clearly predicts the
discovery and general adoption of the electric telegraph. “To confer,”
he says, “at the distance of the Indies by sympathetic conveyance may
be as usual to future times as to us in a literary correspondence.” By
the word “sympathetic” he evidently intended to convey magnetic agency;
for he subsequently treats of “conference at a distance by impregnated
needles,” and describes the device substantially as it is given by Sir
Thomas Browne, adding, that though it did not then answer, “by some
other such way of magnetic efficiency it may hereafter with success be
attempted, when magical history shall be enlarged by riper inspection;
and ’tis not unlikely but that present discoveries might be improved
to the performance.” This may be said to close the most speculative or
mythical period in reference to the subject of electro-telegraphy.

Electricians now began to be sedulous in their experiments upon the
new force by friction, then the only known method of generating
electricity. In 1729, Stephen Gray, a pensioner of the Charter-house,
contrived a method of making electrical signals through a wire 765
feet long; yet this most important experiment did not excite much
attention. Next Dr. Watson, of the Royal Society, experimented on the
possibility of transmitting electricity through a large circuit from
the simple fact of Le Monnier’s account of his feeling the stroke
of the electrified fires through two of the basins of the Tuileries
(which occupy nearly an acre), by means of an iron chain lying upon
the ground and stretched round half their circumference. In 1745, Dr.
Watson, assisted by several members of the Royal Society, made a series
of experiments to ascertain how far electricity could be conveyed by
means of conductors. “They caused the shock to pass across the Thames
at Westminster Bridge, the circuit being completed by making use of the
river for one part of the chain of communication. One end of the wire
communicated with the coating of a charged phial, the other being held
by the observer, who in his other hand held an iron rod which he dipped
into the river. On the opposite side of the river stood a gentleman,
who likewise dipped an iron rod in the river with one hand, and in the
other held a wire the extremity of which might be brought into contact
with the wire of the phial. Upon making the discharge, the shock was
felt simultaneously by both the observers.” (_Priestley’s History of
Electricity._) Subsequently the same parties made experiments near
Shooter’s Hill, when the wires formed a circuit of four miles, and
conveyed the shock with equal facility,--“a distance which without
trial,” they observed, “was too great to be credited.”[52] These
experiments in 1747 established two great principles: 1, that the
electric current is transmissible along nearly two miles and a half of
iron wire; 2, that the electric current may be completed by burying the
poles in the earth at the above distance.

In the following year, 1748, Benjamin Franklin performed his celebrated
experiments on the banks of the Schuylkill, near Philadelphia; which
being interrupted by the hot weather, they were concluded by a picnic,
when spirits were fired by an electric spark sent through a wire in the
river, and a turkey was killed by the electric shock, and roasted by
the electric jack before a fire kindled by the electrified bottle.

In the year 1753, there appeared in the _Scots’ Magazine_, vol. xv.,
definite proposals for the construction of an electric telegraph,
requiring as many conducting wires as there are letters in the
alphabet; it was also proposed to converse by chimes, by substituting
bells for the balls. A similar system of telegraphing was next invented
by Joseph Bozolus, a Jesuit, at Rome; and next by the great Italian
electrician Tiberius Cavallo, in his treatise on Electricity.

In 1787, Arthur Young, when travelling in France, saw a model working
telegraph by M. Lomond: “You write two or three words on a paper,” says
Young; “he takes it with him into a room, and turns a machine enclosed
in a cylindrical case, at the top of which is an electrometer--a
small fine pith-ball; a wire connects with a similar cylinder and
electrometer in a distant apartment; and his wife, by remarking the
corresponding motions of the ball, writes down the words they indicate:
from which it appears that he has formed an alphabet of motions. As the
length of the wire makes no difference in the effect, a correspondence
might be carried on at any distance. Whatever the use may be, the
invention is beautiful.”

We now reach a new epoch in the scientific period--the discovery of the
Voltaic Pile. In 1794, according to _Voigt’s Magazine_, Reizen made
use of the electric spark for the telegraph; and in 1798 Dr. Salva
of Madrid constructed a similar telegraph, which the Prince of Peace
subsequently exhibited to the King of Spain with great success.

In 1809, Soemmering exhibited a telegraphic apparatus worked by
galvanism before the Academy of Sciences at Munich, in which the mode
of signalling consisted in the development of gas-bubbles from the
decomposition of water placed in a series of glass tubes, each of which
denoted a letter of the alphabet. In 1813, Mr. Sharpe, of Doe Hill near
Alfreton, devised a _voltaic_-electric telegraph, which he exhibited to
the Lords of the Admiralty, who spoke approvingly of it, but declined
to carry it into effect. In the following year, Soemmering exhibited a
_voltaic_-electric telegraph of his own construction, which, however,
was open to the objection of there being as many wires as signs or
letters of the alphabet.

The next invention is of much greater importance. Upon the suggestion
of Cavallo, already referred to, Francis Ronalds constructed a perfect
electric telegraph, employing frictional electricity notwithstanding
Volta’s discoveries had been known in England for sixteen years. This
telegraph was exhibited at Hammersmith in 1816:[53] it consisted of
a single insulated wire, the indication being by pith-balls in front
of a dial. When the wire was charged, the balls were divergent, but
collapsed when the wire was discharged; at the same time were employed
two clocks, with lettered discs for the signals. “If, as Paley asserts
(and Coleridge denies), ‘he alone discovers who proves,’ Ronalds is
entitled to the appellation of the first discoverer of an efficient
electric telegraph.” (_Saturday Review_, No. 147[54]) Nevertheless
the Government of the day refused to avail itself of this admirable
contrivance.

In 1819, Oersted made his great discovery of the deflection, by a
current of electricity, of a magnetic needle at right angles to such
current. Dr. Hamel of St. Petersburg states that Baron Schilling was
the first to apply Oersted’s discovery to telegraphy; Ampère had
previously suggested it, but his plan was very complicated, and Dr.
Hamel maintains that Schilling first realised the idea by actually
producing an electro-magnetic telegraph simpler in construction
than that which Ampère had _imagined_. In 1836, Professor Muncke of
Heidelberg, who had inspected Schilling’s telegraphic apparatus,
explained the same to William Fothergill Cooke, who in the following
year returned to England, and subsequently, with Professor Wheatstone,
laboured simultaneously for the introduction of the electro-magnetic
telegraph upon the English railways; the first patent for which was
taken out in the joint names of these two gentlemen.

In 1844, Professor Wheatstone, with one of his telegraphs, formed a
communication between King’s College and the lofty shot-tower on the
opposite bank of the Thames: the wire was laid along the parapets of
the terrace of Somerset House and Waterloo Bridge, and thence to the
top of the tower, about 150 feet high, where a telegraph was placed;
the wire then descended, and a plate of zinc attached to its extremity
was plunged into the mud of the river, whilst a similar plate attached
to the extremity at the north side was immersed in the water. The
circuit was thus completed by the entire breadth of the Thames, and the
telegraph acted as well as if the circuit were entirely metallic.

Shortly after this experiment, Professor Wheatstone and Mr. Cooke laid
down the first working electric telegraph on the Great Western Railway,
from Paddington to Slough.


ELECTRIC GIRDLE FOR THE EARTH.

One of our most profound electricians is reported to have exclaimed:
“Give me but an unlimited length of wire, with a small battery, and I
will girdle the universe with a sentence in forty minutes.” Yet this is
no vain boast; for so rapid is the transition of the electric current
along the line of the telegraph wire, that, supposing it were possible
to carry the wires eight times round the earth, the transit would
occupy but _one second of time_!


CONSUMPTION OF THE ELECTRIC TELEGRAPH.

It is singular to see how this telegraphic agency is measured by the
chemical consumption of zinc and acid. Mr. Jones (who has written a
work upon the Electric Telegraphs of America) estimates that to work
12,000 miles of telegraph about 3000 zinc cups are used to hold the
acid: these weigh about 9000 lbs., and they undergo decomposition by
the galvanic action in about six months, so that 18,000 lbs. of zinc
are consumed in a year. There are also about 3600 porcelain cups to
contain nitric acid; it requires 450 lbs. of acid to charge them once,
and the charge is renewed every fortnight, making about 12,000 lbs. of
nitric acid in a year.


TIME LOST IN ELECTRIC MESSAGES.

Although it may require an hour, or two or three hours, to transmit
a telegraphic message to a distant city, yet it is the mechanical
adjustment by the sender and receiver which really absorbs this time;
the actual transit is practically instantaneous, and so it would be
from here to the antipodes, so far as the current itself is concerned.


THE ELECTRIC TELEGRAPH IN ASTRONOMY AND THE DETERMINATION OF LONGITUDE.

The Electric Telegraph has become an instrument in the hands of the
astronomer for determining the difference of longitude between two
observatories. Thus in 1854 the difference of longitude between London
and Paris was determined within a limit of error which amounted barely
to a quarter of a second. The sudden disturbances of the magnetic
needle, when freely suspended, which seem to take place simultaneously
over whole continents, if not over the whole globe, from some
unexplained cause, are pointed out as means by which the differences of
longitude between the magnetic observatories may possibly be determined
with greater precision than by any yet known method.

So long ago as 1839 Professor Morse suggested some experiments for
the determination of Longitudes; and in June 1844 the difference of
longitude between Washington and Baltimore was determined by electric
means under his direction. Two persons were stationed at these two
towns, with clocks carefully adjusted to the respective spots; and
a telegraphic signal gave the means of comparing the two clocks
at a given instant. In 1847 the relative longitudes of New York,
Philadelphia, and Washington were determined by means of the electric
telegraph by Messrs. Keith, Walker, and Loomis.


NON-INTERFERENCE OF GALVANIC WAVES ON THE SAME WIRE.

One of the most remarkable facts in the economy of the telegraph is,
that the line, when connected with a battery in action, propagates
the hydro-galvanic waves in either direction without interference. As
several successive syllables of sound may set out in succession from
the same place, and be on their way at the same time, to a listener at
a distance, so also, where the telegraph-line is long enough, several
waves may be on their way from the signal station before the first one
reaches the receiving station; two persons at a distance may pronounce
several syllables at the same time, and each hear those emitted by the
other. So, on a telegraph-line of two or three thousand miles in length
in the air, and the same in the ground, two operators may at the same
instant commence a series of several dots and lines, and each receive
the other’s writings, though the waves have crossed each other on the
way.


EFFECT OF LIGHTNING UPON THE ELECTRIC TELEGRAPH.

In the storm of Sunday April 2, 1848, the lightning had a very
considerable effect on the wires of the electric telegraph,
particularly on the line of railway eastward from Manchester to
Normanton. Not only were the needles greatly deflected, and their power
of answering to the handles considerably weakened, but those at the
Normanton station were found to have had their poles reversed by some
action of the electric fluid in the atmosphere. The damage, however,
was soon repaired, and the needles again put in good working order.


ELECTRO-TELEGRAPHIC MESSAGE TO THE STARS.

The electric fluid travels at the mean rate of 20,000 miles in a
second under ordinary circumstances; therefore, if it were possible to
establish a telegraphic communication with the star 61 Cygni, it would
require ninety years to send a message there.

Professor Henderson and Mr. Maclear have fully confirmed the annual
parallax of α Centauri to amount to a second of arc, which gives about
twenty billions of miles as its distance from our system; a ray of
light would arrive from α Centauri to us in little more than three
years, and a telegraphic despatch would arrive there in thirty years.


THE ATLANTIC TELEGRAPH.

The telegraphic communication between England and the United States
is so grand a conception, that it would be impossible to detail its
scientific and mechanical relations within the limits of the present
work. All that we shall attempt, therefore, will be to glance at a few
of the leading operations.

In the experiments made before the Atlantic Telegraph was finally
decided on, 2000 miles of subterranean and submarine telegraphic wires,
ramifying through England and Ireland and under the waters of the
Irish Sea, were specially connected for the purpose; and through this
distance of 2000 miles 250 distinct signals were recorded and printed
in one minute.

First, as to the _Cable_. In the ordinary wires by the side of
a railway the electric current travels on with the speed of
lightning--uninterrupted by the speed of lightning; but when a wire
is encased in gutta-percha, or any similar covering, for submersion
in the sea, new forces come into play. The electric excitement of the
wire acts by induction, through the envelope, upon the particles of
water in contact with that envelope, and calls up an electric force
of an opposite kind. There are two forces, in fact, pulling against
each other through the gutta-percha as a neutral medium,--that is,
the electricity in the wire, and the opposite electricity in the film
of water immediately surrounding the cable; and to that extent the
power of the current in the enclosed wire is weakened. A submarine
cable, when in the water, is virtually _a lengthened-out Leyden jar_;
it transmits signals while being charged and discharged, instead of
merely allowing a stream to flow evenly along it: it is a _bottle_
for holding electricity rather than a _pipe_ for carrying it; and
this has to be filled for every time of using. The wire being carried
underground, or through the water, the speed becomes quite measurable,
say a thousand miles in a second, instead of two hundred thousand,
owing to the retardation by induced or retrograde currents. The energy
of the currents and the quality of the wire also affect the speed.
Until lately it was supposed that the wire acts only as a _conductor_
of electricity, and that a long wire must produce a weaker effect than
a short one, on account of the consequent attenuation of the electrical
influence; but it is now known that, the cable being a _reservoir_ as
well as a conductor, its electrical supply is increased in proportion
to its length.

The electro-magnetic current is employed, since it possesses a treble
velocity of transmission, and realises consequently _a threefold
working speed_ as compared with simple voltaic electricity. Mr. Wildman
Whitehouse has determined by his ingenious apparatus that the speed
of the voltaic current might be raised under special circumstances
to 1800 miles per second; but that of the induced current, or the
electro-magnetic, might be augmented to 6000 miles per second.

Next as to a _Quantity Battery_ employed in these investigations. To
effect a charge, and transmit a current through some thousand miles of
the Atlantic Cable, Mr. Whitehouse had a piece of apparatus prepared
consisting of twenty-five pairs of zinc and silver plates about the
20th part of a square inch large, and the pairs so arranged that
they would hold a drop of acidulated water or brine between them. On
charging this Lilliputian battery by dipping the plates in salt and
water, messages were sent from it through a thousand miles of cable
with the utmost ease; and not only so,--pair after pair was dropped
out from the series, the messages being still sent on with equal
facility, until at last only a single pair, charged by one single drop
of liquid, was used. Strange to say, with this single pair and single
drop distinct signals were effected through the thousand miles of the
cable! Each signal was registered at the end of the cable in less than
three seconds of time.

The entire length of wire, iron and copper, spun into the cable amounts
to 332,500 miles, a length sufficient to engirdle the earth thirteen
times. The cable weighs from 19 cwt. to a ton per mile, and will bear a
strain of 5 tons.

The _Perpetual Maintenance Battery_, for working the cable at the
bottom of the sea, consists of large plates of platinated silver and
amalgamated zinc, mounted in cells of gutta-percha. The zinc plates in
each cell rest upon a longitudinal bar at the bottom, and the silver
plates hang upon a similar bar at the top of the cell; so that there
is virtually but a single stretch of silver and a single stretch of
zinc in operation. Each of the ten cells contains 2000 square inches
of acting surface; and the combination is so powerful, that when the
broad strips of copper-plate which form the polar extensions are
brought into contact or separated, brilliant flashes are produced,
accompanied by a loud crackling sound. The points of large pliers
are made red-hot in five seconds when placed between them, and even
screws burn with vivid scintillation. The cost of maintaining this
magnificent ten-celled Titan battery at work does not exceed a shilling
per hour. The voltaic current generated in this battery is not,
however, the electric stream to be sent across the Atlantic, but is
only the primary power used to call up and stimulate the energy of a
more speedy traveller by a complicated apparatus of “Double Induction
Coils.” Nor is the transmission-current generated in the inner wire
of the double induction coil,--and which becomes weakened when it has
passed through 1800 or 1900 miles,--set to work to print or record the
signals transmitted. This weakened current merely opens and closes the
outlet of a fresh battery, which is to do the printing labour. This
relay-instrument (as it is called), which consists of a temporary and
permanent magnet, is so sensitive an apparatus, that it may be put in
action by a fragment of zinc and a sixpence pressed against the tongue.

The attempts to lay the cable in August 1857 failed through stretching
it so tightly that it snapped and went to the bottom, at a depth of
12,000 feet, forty times the height of St. Paul’s.

This great work was resumed in August 1858; and on the 5th the first
signals were received through _two thousand and fifty miles_ of the
Atlantic Cable. And it is worthy of remark, that just 111 years
previously, on the 5th of August 1747, Dr. Watson astonished the
scientific world by practically proving that the electric current could
be transmitted through a _wire hardly two miles and a half long_.[55]




Miscellanea.


HOW MARINE CHRONOMETERS ARE RATED AT THE ROYAL OBSERVATORY, GREENWICH.

The determination of the Longitude at Sea requires simply accurate
instruments for the measurement of the positions of the heavenly
bodies, and one or other of the two following,--either perfectly
correct watches--or chronometers, as they are now called--or perfectly
accurate tables of the lunar motions.

So early as 1696 a report was spread among the members of the Royal
Society that Sir Isaac Newton was occupied with the problem of finding
the longitude at sea; but the rumour having no foundation, he requested
Halley to acquaint the members “that he was not about it.”[56] (_Sir
David Brewster’s Life of Newton._)

In 1714 the legislature of Queen Anne passed an Act offering a reward
of 20,000_l._ for the discovery of the longitude, the problem being
then very inaccurately solved for want of good watches or lunar tables.
About the year 1749, the attention of the Royal Society was directed
to the improvements effected in the construction of watches by John
Harrison, who received for his inventions the Copley Medal. Thus
encouraged, Harrison continued his labours with unwearied diligence,
and produced in 1758 a timekeeper which was sent for trial on a voyage
to Jamaica. After 161 days the error of the instrument was only 1m
5s, and the maker received from the nation 5000_l._ The Commissioners
of the Board of Longitude subsequently required Harrison to construct
under their inspection chronometers of a similar nature, which were
subjected to trial in a voyage to Barbadoes, and performed with such
accuracy, that, after having fully explained the principle of their
construction to the commissioners, they awarded him 10,000_l._ more;
at the same time Euler of Berlin and the heirs of Mayer of Göttingen
received each 3000_l._ for their lunar tables.

  The account of the trial of Harrison’s watch is very interesting.
  In April 1766, by desire of the Commissioners of the Board, the
  Lords of the Admiralty delivered the watch into the custody of
  the Astronomer-Royal, the Rev. Dr. Nevil Maskelyne. It was then
  placed at the Royal Observatory at Greenwich, in a box having two
  different locks, fixed to the floor or wainscot, with a plate of
  glass in the lid of the box, so that it might be compared as often
  as convenient with the regulator and the variation set down. The
  form observed by Mr. Harrison in winding up the watch was exactly
  followed; and an officer of Greenwich Hospital attended every day,
  at a stated hour, to see the watch wound up, and its comparison
  with the regulator entered. A key to one of the locks was kept at
  the Hospital for the use of the officer, and the other remained
  at the Observatory for the use of the Astronomer-Royal or his
  assistant.

  The watch was then tried in various positions till the beginning
  of July; and from thence to the end of February following in a
  horizontal position with its face upwards.

  The variation of the watch was then noted down, and a register was
  kept of the barometer and thermometer; and the time of comparing
  the same with the regulator was regularly kept, and attested by
  the Astronomer-Royal or his assistant and such of the officers as
  witnessed the winding-up and comparison of the watch.

  Under these conditions Harrison’s watch was received by the
  Astronomer-Royal at the Admiralty on May 5, 1766, in the presence
  of Philip Stephens, Esq., Secretary of the Admiralty; Captain
  Baillie, of the Royal Hospital, Greenwich; and Mr. Kendal the
  watchmaker, who accompanied the Astronomer-Royal to Greenwich, and
  saw the watch started and locked up in the box provided for it. The
  watch was then compared with the transit clock daily, and wound up
  in the presence of the officer of Greenwich Hospital. From May 5 to
  May 17 the watch was kept in a horizontal position with its face
  upwards; from May 18 to July 6 it was tried--first inclined at an
  angle of 20° to the horizon, with the face upwards, and the hours
  12, 6, 3, and 9, highest successively; then in a vertical position,
  with the same hours highest in order; lastly, in a horizontal
  position with the face downwards. From July 16, 1766, to March 4,
  1767, it was always kept in a horizontal position with its face
  upwards, lying upon the same cushion, and in the same box in which
  Mr. Harrison had kept it in the voyage to Barbadoes.

  From the observed transits of the sun over the meridian, according
  to the time of the regulator of the Observatory, together with
  the attested comparisons of Mr. Harrison’s watch with the transit
  clock, the watch was found too fast on several days as follows:

                                h.  m.   s.
    1766. May 6      too fast   0   0  16·2
          May 17        ”       0   3  51·8
          July 6        ”       0  14  14·0
          Aug. 6        ”       0  23  58·4
          Sept. 17      ”       0  32  15·6
          Oct. 29       ”       0  42  20·9
          Dec. 10       ”       0  54  46·8
    1767. Jan. 21       ”       1   0  28·6
          March 4       ”       1  11  23·0

  From May 6, which was the day after the watch arrived at the Royal
  Observatory, to March 4, 1767, there were six periods of six weeks
  each in which the watch was tried in a horizontal position; when
  the gaining in these several periods was as follows:

    During the first 6 weeks it gained 13m 20s, answering to 3° 20′
    of longitude.

    In the 2d period of 6
      weeks (from Aug. 6 to        ”    8  17       ”        2   4
      Sept. 17)

    In the 3d period (from         ”   10   5       ”        2  31
      Sept. 17 to Oct. 29)

    In the 4th period (from        ”   12  26       ”        3   6
      Oct. 29 to Dec. 20)

    In the 5th period (from        ”    5  42       ”        1  25
      Dec. 20 to Jan. 21)

    In the 6th period (from        ”   10  54       ”        2  43
      Jan. 21 to Mar. 4)

It was thence concluded that Mr. Harrison’s watch could not be depended
upon to keep the longitude within a West-India voyage of six weeks, nor
to keep the longitude within half a degree for more than a fortnight;
and that it must be kept in a place where the temperature was always
some degrees above freezing.[57] (However, Harrison’s watch, which was
made by Mr. Kendal subsequently, succeeded so completely, that after it
had been round the world with Captain Cook, in the years 1772-1775, the
second 10,000_l._ was given to Harrison.)

In the Act of 12th Queen Anne, the comparison of chronometers was not
mentioned in reference to the Observatory duties; but after this time
they became a serious charge upon the Observatory, which, it must be
admitted, is by far the best place to try chronometers: the excellence
of the instruments, and the frequent observations of the heavenly
bodies over the meridian, will always render the rate of going of the
Observatory clock better known than can be expected of the clock in
most other places.

After Mr. Harrison’s watch was tried, some watches by Earnshaw, Mudge,
and others, were rated and examined by the Astronomer-Royal.

At the Royal Observatory, Greenwich, there are frequently above 100
chronometers being rated, and there have been as many as 170 at one
time. They are rated daily by two observers, the process being as
follows. At a certain time every day two assistants in charge repair
to the chronometer-room, where is a time-piece set to true time; one
winds up each with its own key, and the second follows after some
little time and verifies the fact that each is wound. One assistant
then looks at each watch in succession, counting the beats of the clock
whilst he compares the chronometer by the eye; and in the course of a
few seconds he calls out the second shown by the chronometer when the
clock is at a whole minute. This number is entered in a book by the
other assistant, and so on till all the chronometers are compared.
Then the assistants change places, the second comparing and the first
writing down. From these daily comparisons the daily rates are deduced,
by which the goodness of the watch is determined. The errors are of
two classes--that of general bad workmanship, and that of over or
under correction for temperature. In the room is an apparatus in which
the watch may be continually kept at temperatures exceeding 100° by
artificial heat; and outside the window of the room is an iron cage,
in which they are subjected to low temperatures. The very great care
taken with all chronometers sent to the Royal Observatory, as well as
the perfect impartiality of the examination which each receives, afford
encouragement to their manufacture, and are of the utmost importance to
the safety and perfection of navigation.

We have before us now the Report of the Astronomer-Royal on the Rates
of Chronometers in the year 1854, in which the following are the
successive weekly sums of the daily rates of the first there mentioned:

    Week ending              secs.

    Jan. 21, loss in the week 2·2
     ”   28         ”         4·0
    Feb.  4         ”         1·1
     ”   11         ”         5·0
     ”   18         ”         4·9
     ”   25         ”         5·5
    Mar.  4         ”         6·0
     ”   11         ”         6·0
     ”   18         ”         1·5
     ”   25         ”         4·5
    Apr.  1         ”         4·0
     ”    8         ”         1·5
     ”   15, gain in the week 0·4
    Apr. 22,        ”         2·6
     ”   29, loss in the week 1·4
    May   6         ”         2·1
     ”   13         ”         3·0
     ”   20         ”         5·1
     ”   27         ”         3·3
    June  3         ”         2·8
     ”   10         ”         1·8
     ”   17         ”         2·0
     ”   24         ”         3·0
    July  1         ”         2·5
     ”    8         ”         1·2

Till February 4 the watch was exposed to the external air outside a
north window; from February 5 to March 4 it was placed in the chamber
of a stove heated by gas to a moderate temperature; and from April
29 to May 20 it was placed in the chamber when heated to a high
temperature.

The advance in making chronometers since Harrison’s celebrated watch
was tried at the Royal Observatory, more than ninety years since, may
be judged by comparing its rates with those above.


GEOMETRY OF SHELLS.

There is a mechanical uniformity observable in the description of
shells of the same species which at once suggests the probability that
the generating figure of each increases, and that the spiral chamber of
each expands itself, according to some simple geometrical law common
to all. To the determination of this law the operculum lends itself,
in certain classes of shells, with remarkable facility. Continually
enlarged by the animal, as the construction of its shell advances so as
to fill up its mouth, the operculum measures the progressive widening
of the spiral chamber by the progressive stages of its growth.

       *       *       *       *       *

The animal, as he advances in the construction of his shell, increases
continually his operculum, so as to adjust it to his mouth. He
increases it, however, not by additions made at the same time all round
its margin, but by additions made only on one side of it at once. One
edge of the operculum thus remains unaltered as it is advanced into
each new position, and placed in a newly-formed section of the chamber
similar to the last but greater than it.

That the same edge which fitted a portion of the first less section
should be capable of adjustment so as to fit a portion of the next
similar but greater section, supposes a geometrical provision in the
curved form of the chamber of great complication and difficulty. But
God hath bestowed upon this humble architect the practical skill of
the learned geometrician; and he makes this provision with admirable
precision in that curvature of the logarithmic spiral which he gives to
the section of the shell. This curvature obtaining, he has only to turn
his operculum slightly round in its own place, as he advances it into
each newly-formed portion of his chamber, to adapt one margin of it to
a new and larger surface and a different curvature, leaving the space
to be filled up by increasing the operculum wholly on the outer margin.

       *       *       *       *       *

Why the Mollusks, who inhabit turbinated and discoid shells, should, in
the progressive increase of their spiral dwellings, affect the peculiar
law of the logarithmic spiral, is easily to be understood. Providence
has subjected the instinct which shapes out each to a rigid uniformity
of operation.--_Professor Mosely_: _Philos. Trans._ 1838.


HYDRAULIC THEORY OF SHELLS.

How beautifully is the wisdom of God developed in shaping out and
moulding shells! and especially in the particular value of the constant
angle which the spiral of each species of shell affects,--a value
connected by a necessary relation with the economy of the material
of each, and with its stability and the conditions of its buoyancy.
Thus the shell of the _Nautilus Pompilius_ has, hydrostatically, an
A-statical surface. If placed with any portion of its surface upon the
water, it will immediately turn over towards its smaller end, and rest
only on its mouth. Those conversant with the theory of floating bodies
will recognise in this an interesting property.--_Ibid._


SERVICES OF SEA-SHELLS AND ANIMALCULES.

Dr. Maury is disposed to regard these beings as having much to do in
maintaining the harmonies of creation, and the principles of the most
admirable compensation in the system of oceanic circulation. “We may
even regard them as regulators, to some extent, of climates in parts
of the earth far removed from their presence. There is something
suggestive both of the grand and the beautiful in the idea that while
the insects of the sea are building up their coral islands in the
perpetual summer of the tropics, they are also engaged in dispensing
warmth to distant parts of the earth, and in mitigating the severe cold
of the polar winter.”


DEPTH OF THE PRIMEVAL SEAS.

Professor Forbes, in a communication to the Royal Society, states that
not only the colour of the shells of existing mollusks ceases to be
strongly marked at considerable depths, but also that well-defined
patterns are, with very few and slight exceptions, presented only by
testacea inhabiting the littoral, circumlittoral, and median zones.
In the Mediterranean, only one in eighteen of the shells taken from
below 100 fathoms exhibit any markings of colour, and even the few
that do so are questionable inhabitants of those depths. Between 30
and 35 fathoms, the proportion of marked to plain shells is rather
less than one in three; and between the margin and two fathoms the
striped or mottled species exceed one-half of the total number. In our
own seas, Professor Forbes observes that testacea taken from below 100
fathoms, even when they are individuals of species vividly striped or
banded in shallower zones, are quite white or colourless. At between
60 and 80 fathoms, striping and banding are rarely presented by our
shells, especially in the northern provinces; from 50 fathoms, shallow
bands, colours, and patterns, are well marked. _The relation of these
arrangements of colour to the degree of light penetrating the different
zones of depth_ is a subject well worthy of minute inquiry.


NATURAL WATER-PURIFIERS.

Mr. Warrington kept for a whole year twelve gallons of water in a state
of admirably balanced purity by the following beautiful action:

  In the tank, or aquarium, were two gold fish, six water-snails, and
  two or three specimens of that elegant aquatic plant _Valisperia
  sporalis_, which, before the introduction of the water-snails, by
  its decayed leaves caused a growth of slimy mucus, and made the
  water turbid and likely to destroy both plants and fish. But under
  the improved arrangement the slime, as fast as it was engendered,
  was consumed by the water-snails, which reproduced it in the shape
  of young snails, which furnished a succulent food to the fish.
  Meanwhile the _Valisperia_ plants absorbed the carbonic acid
  exhaled by the respiration of their companions, fixing the carbon
  in their growing stems and luxuriant blossoms, and refreshing
  the oxygen (during sunshine in visible little streams) for the
  respiration of the snails and the fish. The spectacle of perfect
  equilibrium thus simply maintained between animal, vegetable, and
  inorganic activity, was strikingly beautiful; and such means might
  possibly hereafter be made available on a large scale for keeping
  tanked water sweet and clean.--_Quarterly Review_, 1850.


HOW TO IMITATE SEA-WATER.

The demand for Sea-water to supply the Marine Aquarium--now to be
seen in so many houses--induced Mr. Gosse to attempt the manufacture
of Sea-water, more especially as the constituents are well known. He
accordingly took Scheveitzer’s analysis of Sea-water for his guide. In
one thousand grains of sea-water taken off Brighton, it gave: water,
964·744; chloride of sodium, 27·059; chloride of magnesium, 3·666;
chloride of potassium, 9·755; bromide of magnesium, 0·29; sulphate of
magnesia, 2·295; sulphate of lime, 1·407; carbonate of lime, 0·033:
total, 999·998. Omitting the bromide of magnesium, the carbonate of
lime, and the sulphate of lime, as being very small quantities, the
component parts were reduced to common salt, 3½ oz.; Epsom salts, ¼
oz.; chloride of magnesium, 200 grains troy; chloride of potassium,
40 grains troy; and four quarts of water. Next day the mixture was
filtered through a sponge into a glass jar, the bottom covered with
shore-pebbles and fragments of stone and fronds of green sea-weed. A
coating of green spores was soon deposited on the sides of the glass,
and bubbles of oxygen were copiously thrown off every day under the
excitement of the sun’s light. In a week Mr. Gosse put in species of
_Actinia Bowerbankia_, _Cellularia_, _Serpula_, &c. with some red
sea-weeds; and the whole throve well.


VELOCITY OF IMPRESSIONS TRANSMITTED TO THE BRAIN.

Professor Helmholtz of Königsberg has, by the electro-magnetic
method,[58] ascertained that the intelligence of an impression
made upon the ends of the nerves in communication with the skin
is transmitted to the brain with a velocity of about 195 feet per
second. Arrived at the brain, about one-tenth of a second passes
before the will is able to give the command to the nerves that certain
muscles shall execute a certain motion, varying in persons and times.
Finally, about 1/100th of a second passes after the receipt of the
command before the muscle is in activity. In all, therefore, from the
excitation of the sensitive nerves till the moving of the muscle, 1¼
to 2/10ths of a second are consumed. Intelligence from the great toe
arrives about 1/30th of a second later than from the ear or the face.

Thus we see that the differences of time in the nervous impressions,
which we are accustomed to regard as simultaneous, lie near our
perception. We are taught by astronomy that, on account of the
time taken to propagate light, we now see what has occurred in the
fixed stars years ago; and that, owing to the time required for the
transmission of sound, we hear after we see is a matter of daily
experience. Happily the distances to be traversed by our sensuous
perceptions before they reach the brain are so short that we do
not observe their influence, and are therefore unprejudiced in our
practical interest. With an ordinary whale the case is perhaps more
dubious; for in all probability the animal does not feel a wound near
its tail until a second after it has been inflicted, and requires
another second to send the command to the tail to defend itself.


PHOTOGRAPHS ON THE RETINA.

The late Rev. Dr. Scoresby explained with much minuteness and skill
the varying phenomena which presented themselves to him after gazing
intently for some time on strongly-illuminated objects,--as the sun,
the moon, a red or orange or yellow wafer on a strongly-contrasted
ground, or a dark object seen in a bright field. The doctor explained,
upon removing the eyes from the object, the early appearance of the
picture or image which had been thus “photographed on the Retina,” with
the photochromatic changes which the picture underwent while it still
retained its general form and most strongly-marked features; also, how
these pictures, when they had almost faded away, could at pleasure, and
for a considerable time, be renewed by rapidly opening and shutting the
eyes.


DIRECT EXPLORATION OF THE INTERIOR OF THE EYE.

Dr. S. Wood of Cincinnati states, that by means of a small double
convex lens of short focus held near the eye,--that organ looking
through it at a candle twelve or fifteen feet distant,--there will be
perceived a large luminous disc, covered with dark and light spots and
dark streaks, which, after a momentary confusion, will settle down
into an unchanging picture, which picture is composed of the organs
or internal parts of the eye. The eye is thus enabled to view its own
internal organisation, to have a beautiful exhibition of the vessels of
the cornea, of the distribution of the lachrymas secretions in the act
of winking, and to see into the nature and cause of _muscæ volitantes_.


NATURE OF THE CANDLE-FLAME.

M. Volger has subjected this Flame to a new analysis.

  He finds that the so-called _flame-bud_, a globular blue flaminule,
  is first produced at the summit of the wick: this is the result
  of the combustion of carbonic oxide, hydrogen, and carbon, and is
  surrounded by a reddish-violet halo, the _veil_. The increased
  heat now gives rise to the actual flame, which shoots forth from
  the expanding bud, and is then surrounded at its inferior portion
  only by the latter. The interior consists of a dark gaseous cone,
  containing the immediate products of the decomposition of the fatty
  acids, and surrounded by another dark hollow cone, the _inner
  cap_. Here we already meet with carbon and hydrogen, which have
  resulted from the process of decomposition; and we distinguish
  this cone from the inner one by its yielding soot. The _external
  cap_ constitutes the most luminous portion of the flame, in which
  the hydrogen is consumed and the carbon rendered incandescent. The
  surrounding portion is but slightly luminous, deposits no soot,
  and in it the carbon and hydrogen are consumed.--_Liebig’s Annual
  Report._


HOW SOON A CORPSE DECAYS.

Mr. Lewis, of the General Board of Health, from his examination of the
contents of nearly 100 coffins in the vaults and catacombs of London
churches, concludes that the complete decomposition of a corpse, and
its resolution into its ultimate elements, takes place in a leaden
coffin with extreme slowness. In a wooden coffin the remains, with the
exception of the bones, vanish in from two to five years. This period
depends upon the quality of the wood, and the free access of air to
the coffins. But in leaden coffins, 50, 60, 80, and even 100 years
are required to accomplish this. “I have opened,” says Mr. Lewis, “a
coffin in which the corpse had been placed for nearly a century; and
the ammoniacal gas formed dense white fumes when brought in contact
with hydrochloric-acid gas, and was so powerful that the head could
not remain in it for more than a few seconds at a time.” To render the
human body perfectly inert after death, it should be placed in a light
wooden coffin, in a pervious soil, from five to eight feet deep.


MUSKET-BALLS FOUND IN IVORY.

The Ceylon sportsman, in shooting elephants, aims at a spot just above
the proboscis. If he fires a little too low, the ball passes into the
tusk-socket, causing great pain to the animal, but not endangering
its life; and it is immediately surrounded by osteo-dentine. It has
often been a matter of wonder how such bodies should become completely
imbedded in the substance of the tusk, sometimes without any visible
aperture; or how leaden bullets become lodged in the solid centre of a
very large tusk without having been flattened, as they are found by
the ivory-turner.

  The explanation is as follows: A musket-ball aimed at the head of
  an elephant may penetrate the thin bony socket and the thinner
  ivory parietes of the wide conical pulp-cavity occupying the
  inserted base of the tusk; if the projectile force be there spent,
  the ball will gravitate to the opposite and lower side of the
  pulp-cavity. The pulp becomes inflamed, irregular calcification
  ensues, and osteo-dentine is formed around the ball. The pulp
  then resumes its healthy state and functions, and coats the
  osteo-dentine enclosing the ball, together with the root of the
  conical cavity into which the mass projects, with layers of normal
  ivory. The hole formed by the ball is soon replaced, and filled
  up by osteo-dentine, and coated with cement. Meanwhile, by the
  continued progress of growth, the enclosed ball is pushed forward
  to the middle of the solid tusk; or if the elephant be young, the
  ball may be carried forward by growth and wear of the tusk until
  its base has become the apex, and become finally exposed and
  discharged by the continual abrasion to which the apex of the tusk
  is subjected.--_Professor Owen._


NATURE OF THE SUN.

To the article at pp. 59-60 should be added the result obtained by Dr.
Woods of Parsonstown, and communicated to the _Philosophical Magazine_
for July 1854. Dr. Woods, from photographic experiment, has no doubt
that the light from the centre of flame acts more energetically than
that from the edge on a surface capable of receiving its impression;
and that light from a luminous solid body acts equally powerfully from
its centre or its edges: wherefore Dr. Woods concludes that, as the
sun affects a sensitive plate similarly with flame, it is probable its
light-producing portion is of a similar nature.

  _Note to_ “IS THE HEAT OF THE SUN DECREASING?” _at page 65_.--Dr.
  Vaughan of Cincinnati has stated to the British Association:
  “From a comparison of the relative intensity of solar, lunar,
  and artificial light, as determined by Euler and Wollaston, it
  appears that the rays of the sun have an illuminating power
  equal to that of 14,000 candles at a distance of one foot, or
  of 3500,000000,000000,000000,000000 candles at a distance of
  95,000,000 miles. It follows that the amount of light which
  flows from the solar orb could be scarcely produced by the daily
  combustion of 200 globes of tallow, each equal to the earth in
  magnitude. A sphere of combustible matter much larger than the
  sun itself should be consumed every ten years in maintaining its
  wonderful brilliancy; and its atmosphere, if pure oxygen, would be
  expended before a few days in supporting so great a conflagration.
  An illumination on so vast a scale could be kept up only by the
  inexhaustible magazine of ether disseminated through space, and
  ever ready to manifest its luciferous properties on large spheres,
  whose attraction renders it sufficiently dense for the play of
  chemical affinity. Accordingly suns derive the power of shedding
  perpetual light, not from their chemical constitution, but from
  their immense mass and their superior attractive power.”


PLANETOIDS.

  +----------------+---------------+-----------+-----------+-----------+
  |                |               |           |           |    No.    |
  |                |               |           |           |discovered |
  |                |    Date of    |           | Place of  |  by each  |
  |      Name.     |  Discovery.   |Discoverer.| Discovery.|astronomer.|
  +----------------+---------------+-----------+-----------+-----------+
  |Mercury, Mars, }|     Known  }  |           |           |           |
  |Venus, Jupiter,}|    to the  }  |   ...     |    ...    |    --     |
  |Earth, Saturn, }|   ancients.}  |           |           |           |
  |   Uranus       |1781, March 13 |W. Herschel| Bath      |    --     |
  |   Neptune[59]  |1846, Sept. 23 |Galle      | Berlin    |    --     |
  | 1 Ceres        |1801, Jan. 1   |Piazzi     | Palermo   |     1     |
  | 2 Pallas       |1802, March 28 |Olbers     | Bremen    |     1     |
  | 3 Juno         |1804, Sept. 1  |Harding    | Lilienthal|     1     |
  | 4 Vesta        |1807, March 29 |Olbers     | Bremen    |     2     |
  | 5 Astræa       |1845, Dec. 8   |Encke      | Driesen   |     1     |
  | 6 Hebe         |1847, July 1   |Encke      | Driesen   |     2     |
  | 7 Iris         |1847, August 13|Hind       | London    |     1     |
  | 8 Flora        |1847, Oct. 18  |Hind       | London    |     2     |
  | 9 Metis        |1848, April 25 |Graham     | Markree   |     1     |
  |10 Hygeia       |1849, April 12 |Gasperis   | Naples    |     1     |
  |11 Parthenope   |1850, May 11   |Gasperis   | Naples    |     2     |
  |12 Victoria     |1850, Sept. 13 |Hind       | London    |     3     |
  |13 Egeria       |1850, Nov. 2   |Gasperis   | Naples    |     3     |
  |14 Irene        |1851, May 19   |Hind       | London    |     4     |
  |15 Eunomia      |1851, July 29  |Gasperis   | Naples    |     4     |
  |16 Psyche       |1852, March 17 |Gasperis   | Naples    |     5     |
  |17 Thetis       |1852, April 17 |Luther     | Bilk      |     1     |
  |18 Melpomene    |1852, June 24  |Hind       | London    |     5     |
  |19 Fortuna      |1852, August 22|Hind       | London    |     6     |
  |20 Massilia     |1852, Sept. 19 |Gasperis   | Naples    |     6     |
  |21 Lutetia      |1852, Nov. 15  |Goldschmidt| Paris     |     1     |
  |22 Calliope     |1852, Nov. 16  |Hind       | London    |     7     |
  |23 Thalia       |1852, Dec. 15  |Hind       | London    |     8     |
  |24 Themis       |1853, April 5  |Gasperis   | Naples    |     7     |
  |25 Phocea       |1853, April 6  |Chacornac  | Marseilles|     1     |
  |26 Proserpine   |1853, May 5    |Luther     | Bilk      |     2     |
  |27 Euterpe      |1853, Nov. 8   |Hind       | London    |     9     |
  |28 Bellona      |1854, March 1  |Luther     | Bilk      |     3     |
  |29 Amphitrite   |1854, March 1  |Marth      | London    |     1     |
  |30 Urania       |1854, July 22  |Hind       | London    |    10     |
  |31 Euphrosyne   |1854, Sept. 1  |Furguson   | Washington|     1     |
  |32 Pomona       |1854, Oct. 26  |Goldschmidt| Paris     |     2     |
  |33 Polyhymnia   |1854, Oct. 28  |Chacornac  | Paris     |     2     |
  |34 Circe        |1855, April 6  |Chacornac  | Paris     |     3     |
  |35 Leucothea    |1855, April 19 |Luther     | Bilk      |     4     |
  |36 Atalante     |1855, Oct. 5   |Goldschmidt| Paris     |     3     |
  |37 Fides        |1855, Oct. 5   |Luther     | Bilk      |     5     |
  |38 Leda         |1856, Jan. 12  |Chacornac  | Paris     |     4     |
  |39 Lætitia      |1856, Feb. 8   |Chacornac  | Paris     |     5     |
  |40 Harmonia     |1856, March 31 |Goldschmidt| Paris     |     4     |
  |41 Daphne       |1856, May 22   |Goldschmidt| Paris     |     5     |
  |42 Isis         |1856, May 23   |Pogson     | Oxford    |     1     |
  |43 Ariadne      |1857, April 15 |Pogson     | Oxford    |     2     |
  |44 Nysa         |1857, May 27   |Goldschmidt| Paris     |     6     |
  |45 Eugenia      |1857, June 28  |Goldschmidt| Paris     |     7     |
  |46 Hastia       |1857, August 16|Pogson     | Oxford    |     3     |
  |47 Aglaia       |1857, Sept. 15 |Luther     | Bilk      |     6     |
  |48 Doris        |1857, Sept. 19 |Goldschmidt| Paris     |     8     |
  |49 Pales        |1857, Sept. 19 |Goldschmidt| Paris     |     9     |
  |50 Virginia     |1857, Oct. 4   |Furguson   | Washington|     2     |
  |51 Nemausa      |1858, Jan. 22  |Laurent    | Nismes    |     1     |
  |52 Europa       |1858, Feb. 6   |Goldschmidt| Paris     |    10     |
  |53 Calypso      |1858, April 8  |Luther     | Bilk      |     7     |
  |54 Alexandra    |1858, Sept. 11 |Goldschmidt| Paris     |    11     |
  |55 (Not named)  |1858, Sept. 11 |Searle     | Albany    |     1     |
  +----------------+---------------+-----------+-----------+-----------+


THE COMET OF DONATI.

While this sheet was passing through the press, the attention of
astronomers, and of the public generally, was drawn to the fact of
the above Comet passing (on Oct. 18) within nine millions of miles of
the planet Venus, or less than 9/100ths of the earth’s distance from
the Sun. “And (says Mr. Hind, the astronomer), it is obvious that
if the comet had reached its least distance from the sun a few days
earlier than it has done, the planet might have passed through it;
and I am very far from thinking that close proximity to a comet of
this description would be unattended with danger. The inhabitants of
Venus will witness a cometary spectacle far superior to that which has
recently attracted so much attention here, inasmuch as the tail will
doubtless appear twice as long from that planet as from the earth, and
the nucleus proportionally more brilliant.”

This Comet was first discovered by Dr. G. B. Donati, astronomer at
the Museum of Florence, on the evening of the 2d of June, in right
ascension 141° 18′, and north declination 23° 47′, corresponding to
a position near the star Leonis. Previous to this date we had no
knowledge of its existence, and therefore it was not a predicted
comet; neither is it the one last observed in 1556. At the date of
discovery it was distant from the earth 228,000,000 of miles, and was
an excessively faint object in the largest telescopes.

The tail, from October 2 to 16, when the comet was most conspicuous,
appears to have maintained an average length of at least 40,000,000
miles, subtending an angle varying from 30° to 40°. The dark line or
space down the centre, frequently remarked in other great comets,
was a striking characteristic in that of Donati. The nucleus, though
small, was intensely brilliant in powerful instruments, and for some
time bore high magnifiers to much greater advantage than is usual with
these objects. In several respects this comet resembled the famous
ones of 1744, 1680, and 1811, particularly as regards the signs of
violent agitation going on in the vicinity of the nucleus, such as
the appearance of luminous jets, spiral offshoots, &c., which rapidly
emanated from the planetary point and as quickly lost themselves in the
general nebulosity of the head.

On the 5th Oct. the most casual observer had an opportunity of
satisfying himself as to the accuracy of the mathematical theory of
the motions of comets in the near approach of the nucleus of Donati’s
to Arcturus, the principal star in the constellation Bootes. The
circumstance of the appulse was very nearly as predicted by Mr. Hind.

The comet, according to the investigations by M. Loewy, of the
Observatory of Vienna, arrived at its least distance from the sun a few
minutes after eleven o’clock on the morning of the 30th of September;
its longitude, as seen from the sun at this time, being 36° 13′, and
its distance from him 55,000,000 miles. The longer diameter of its
orbit is 184 times that of the earth’s, or 35,100,000,000 miles;
yet this is considerably less than 1/1000th of the distance of the
nearest fixed star. As an illustration, let any one take a half-sheet
of note-paper, and marking a circle with a sixpence in one corner
of it, describe therein our solar system, drawing the orbits of the
earth and the inferior planets as small as he can by the aid of a
magnifying-glass. If the circumference of the sixpence stands for the
orbit of Neptune, then an oval filling the page will fairly represent
the orbit of Donati’s comet; and if the paper be laid upon the pavement
under the west door of St. Paul’s Cathedral, London, the length of that
edifice will inadequately represent the distance of the nearest fixed
star. The time of revolution resulting from Mr. Loewy’s calculations
is 2495 years, which is about 500 years less than that of the comet of
1811 during the period it was visible from the earth.

That the comet should take more than 2000 years to travel round the
above page of note-paper is explained by its great diminution of speed
as it recedes from the sun. At its perihelion it travelled at the rate
of 127,000 miles an hour, or more than twice as fast as the earth,
whose motion is about 1000 miles a minute. At its aphelion, however,
or its greatest distance from the sun, the comet is a very slow body,
sailing at the rate of 480 miles an hour, or only eight times the
speed of a railway express. At this pace, were it to travel onward in
a straight line, the lapse of a million of years would find it still
travelling half way between our sun and the nearest fixed star.

As this comet last visited us between 2000 and 2495 years since, we
know that its appearance was at an interesting period of the world’s
history. It might have terrified the Athenians into accepting the
bloody code of Draco. It might have announced the destruction of
Nineveh, or of Babylon, or the capture of Jerusalem by Nebuchadnezzar.
It might have been seen by the expedition which sailed round Africa
in the reign of Pharaoh Necho. It might have given interest to the
foundation of the Pythian games. Within the probable range of its
last visitation are comprehended the whole of the great events of the
history of Greece; and among the spectators of the comet may have been
the so-called sages of Greece and even the prophets of Holy Writ:
Thales might have attempted to calculate its return, and Jeremiah might
have tried to read its warning.--_Abridged from a Communication from
Mr. Hind to the Times, and from a Leader in that Journal._




FOOTNOTES:


[1] From a photograph, with figures, to show the relative size of the
tube aperture.

[2] Weld’s _History of the Royal Society_, vol. ii. p. 188.

[3] Dr. Whewell (_Bridgewater Treatise_, p. 266) well observes, that
Boyle and Pascal are to hydrostatics what Galileo is to mechanics, and
Copernicus, Kepler, and Newton are to astronomy.

[4] The Rev. Mr. Turnor recollects that Mr. Jones, the tutor,
mentioned, in one of his lectures on optics, that the reflecting
telescope belonging to Newton was then lodged in the observatory over
the gateway; and Mr. Turnor thinks that he once saw it, with a finder
affixed to it.

[5] The story of the dog “Diamond” having caused the burning of
certain papers is laid in London, and in Newton’s later years. In the
notes to Maude’s _Wenleysdale_, a person then living (1780) relates,
that Sir Isaac being called out of his study to a contiguous room, a
little dog, called Diamond, the constant but incurious attendant of
his master’s researches, happened to be left among the papers, and
by a fatality not to be retrieved, as it was in the latter part of
Sir Isaac’s days, threw down a lighted candle, which consumed the
almost finished labour of some years. Sir Isaac returning too late
but to behold the dreadful wreck, rebuked the author of it with an
exclamation (_ad sidera palmas_), “O Diamond! Diamond! thou little
knowest the mischief done!” without adding a single stripe. M. Biot
gives this fiction as a true story, which happened some years after
the publication of the _Principia_; and he characterises the accident
as having deprived the sciences forever of the fruit of so much of
Newton’s labours.--Brewster’s _Life_, vol. ii. p. 139, note. Dr. Newton
remarks, that Sir Isaac never had any communion with dogs or cats; and
Sir David Brewster adds, that the view which M. Biot has taken of the
idle story of the dog Diamond, charged with fire-raising among Newton’s
manuscripts, and of the influence of this accident upon the mind of
their author, is utterly incomprehensible. The fiction, however, was
turned to account in giving colour to M. Biot’s misrepresentation.

[6] Bohn’s edition.

[7] When at Pisa, many years since, Captain Basil Hall investigated
the origin and divergence of the tower from the perpendicular, and
established completely to his own satisfaction that it had been built
from top to bottom originally just as it now stands. His reasons for
thinking so were, that the line of the tower, on that side towards
which it leans, has not the same curvature as the line on the opposite,
or what may be called the upper side. If the tower had been built
upright, and then been made to incline over, the line of the wall on
that side towards which the inclination was given would be more or less
concave in that direction, owing to the nodding or “swagging over” of
the top, by the simple action of gravity acting on a very tall mass
of masonry, which is more or less elastic when placed in a sloping
position. But the contrary is the fact; for the line of wall on the
side towards which the tower leans is decidedly more convex than the
opposite side. Captain Hall had therefore no doubt whatever that the
architect, in rearing his successive courses of stones, gained or
stole a little at each layer, so as to render his work less and less
overhanging as he went up; and thus, without betraying what he was
about, really gained stability.--See _Patchwork_.

[8] Lord Bacon proposed that, in order to determine whether the gravity
of the earth arises from the gravity of its parts, a clock-pendulum
should be swung in a mine, as was recently done at Harton colliery by
the Astronomer-Royal.

When, in 1812, Ampère noted the phenomena of the pendulum, and showed
that its movement was produced only when the eye of the observer was
fixed on the instrument, and endeavoured to prove thereby that the
motion was due to a play of the muscles, some members of the French
Academy objected to the consideration of a subject connected to such an
extent with superstition.

[9] This curious fact was first recorded by Pepys, in his _Diary_,
under the date 31st of July 1665.

[10] The result of these experiments for ascertaining the variation
of the gravity at great depths, has proved beyond doubt that the
attraction of gravitation is increased at the depth of 1250 feet by
1/19000 part.

[11] See the account of Mr. Baily’s researches (with two illustrations)
in _Things not generally Known_, p. vii., and “Weight of the Earth,” p.
16.

[12] Fizeau gives his result in leagues, reckoning twenty-five to the
equatorial degree. He estimates the velocity of light at 70,000 such
leagues, or about 210,000 miles in the second.

[13] See _Things not generally Known_, p. 88.

[14] Some time before the first announcement of the discovery of
sun-painting, the following extract from Sir John Herschel’s _Treatise
on Light_, in the _Encyclopædia Metropolitana_, appeared in a popular
work entitled _Parlour Magic_: “Strain a piece of paper or linen upon
a wooden frame, and sponge it over with a solution of nitrate of
silver in water; place it behind a painting upon glass, or a stained
window-pane, and the light, traversing the painting or figures, will
produce a copy of it upon the prepared paper or linen; those parts in
which the rays were least intercepted being the shadows of the picture.”

[15] In his book on Colours, Mr. Doyle informs us that divers, if not
all, essential oils, as also spirits of wine, when shaken, “have a
good store of bubbles, which appear adorned with various and lively
colours.” He mentions also that bubbles of soap and turpentine exhibit
the same colours, which “vary according to the incidence of the sight
and the position of the eye;” and he had seen a glass-blower blow
bubbles of glass which burst, and displayed “the varying colours of the
rainbow, which were exceedingly vivid.”

[16] The original idea is even attributed to Copernicus. M. Blundevile,
in his _Treatise on Cosmography_, 1594, has the following passage,
perhaps the most distinct recognition of authority in our language:
“How prooue (prove) you that there is but one world? By the authoritie
of Aristotle, who saieth that if there were any other world out of
this, then the earth of that world would mooue (move) towards the
centre of this world,” &c.

Sir Isaac Newton, in a conversation with Conduitt, said he took “all
the planets to be composed of the same matter with the earth, viz.
earth, water, and stone, but variously concocted.”

[17] Sir William Herschel ascertained that our solar system is
advancing towards the constellation Hercules, or more accurately to a
point in space whose right ascension is 245° 52′ 30″, and north polar
distance 40° 22′; and that the quantity of this motion is such, that to
an astronomer placed in Sirius, our sun would appear to describe an arc
of little more than _a second_ every year.--_North-British Review_, No.
3.

[18] See M. Arago’s researches upon this interesting subject, in
_Things not generally Known_, p. 4.

[19] This eloquent advocacy of the doctrine of “More Worlds than One”
(referred to at p. 51) is from the author’s valuable _Outlines of
Astronomy_.

[20] Professor Challis, of the Cambridge Observatory, directing the
Northumberland telescope of that institution to the place assigned by
Mr. Adams’s calculations and its vicinity on the 4th and 12th of August
1846, saw the planet on both those days, and noted its place (among
those of other stars) for re-observation. He, however, postponed the
_comparison_ of the places observed, and not possessing Dr. Bremiker’s
chart (which would at once have indicated the presence of an unmapped
star), remained in ignorance of the planet’s existence as a visible
object till the announcement of such by Dr. Galle.

[21] For several interesting details of Comets, see “Destruction of the
World by a Comet,” in _Popular Errors Explained and Illustrated_, new
edit. pp. 165-168.

[22] The letters of Sir Isaac Newton to Dr. Bentley, containing
suggestions for the Boyle Lectures, possess a peculiar interest in the
present day. “They show” (says Sir David Brewster) “that the _nebular
hypothesis_, the dull and dangerous heresy of the age, is incompatible
with the established laws of the material universe, and that an
omnipotent arm was required to give the planets their positions and
motions in space, and a presiding intelligence to assign to them the
different functions they had to perform.”--_Life of Newton_, vol. ii.

[23] The constitution of the nebulæ in the constellation of Orion has
been resolved by this instrument; and by its aid the stars of which it
is composed burst upon the sight of man for the first time.

[24] Several specimens of Meteoric Iron are to be seen in the
Mineralogical Collection in the British Museum.

[25] _Life of Sir Isaac Newton_, vol. i. p. 62.

[26] _Description of the Monster Telescope_, by Thomas Woods, M.D. 4th
edit. 1851.

[27] This instrument also discovered a multitude of new objects in the
moon; as a mountainous tract near Ptolemy, every ridge of which is
dotted with extremely minute craters, and two black parallel stripes in
the bottom of Aristarchus. Dr. Robinson, in his address to the British
Association in 1843, stated that in this telescope a building the size
of the Court-house at Cork would be easily visible on the lunar surface.

[28] Mr. Hopkins supports his Glacial Theory by regarding the _Waves
of Translation_, investigated by Mr. Scott Russell, as furnishing
a sufficient moving power for the transportation of large rounded
boulders, and the formation of drifted gravel. When these waves of
translation are produced by the sudden elevation of the surface of
the sea, the whole mass of water from the surface to the bottom of
the ocean moves onward, and becomes a mechanical agent of enormous
power. Following up this view, Mr. Hopkins has shown that “elevations
of continental masses of only 50 feet each, and from beneath an ocean
having a depth of between 300 and 400 feet, would cause the most
powerful divergent waves, which could transport large boulders to great
distances.”

[29] It is scarcely too much to say, that from the collection of
specimens of building-stones made upon this occasion, and first
deposited in a house in Craig’s Court, Charing Cross, originated,
upon the suggestion of Sir Henry Delabeche, the magnificent Museum of
Practical Geology in Jermyn Street; one of the most eminently practical
institutions of this scientific age.

[30] Mr. R. Mallet, F.R.S., and his son Dr. Mallet, have constructed a
seismographic map of the world, with seismic bands in their position
and relative intensity; and small black discs to denote volcanoes,
femaroles, and soltataras, and shades indicating the areas of
subsidence.

[31] It has been computed that the shock of this earthquake pervaded
an area of 700,000 miles, or the twelfth part of the circumference of
the globe. This dreadful shock lasted only five minutes; and nearly
the whole of the population being within the churches (on the feast of
All Saints), no less than 30,000 persons perished by the fall of these
edifices.--See _Daubeny on Volcanoes_; _Translator’s note, Humboldt’s
Cosmos_.

[32] Mr. Murray mentions, on the authority of the Rev. Dr. Robinson,
of the Observatory at Armagh, that a rough diamond with a red tint,
and valued by Mr. Rundell at twenty guineas, was found in Ireland,
many years since, in the bed of a brook flowing through the county of
Fermanagh.

[33] The use of malachite in ornamental work is very extensive in
Russia. Thus, to the Great Exhibition of 1851 were sent a pair of
folding-doors veneered with malachite, 13 feet high, valued at
6000_l._; malachite cases and pedestals from 1500_l._ to 3000_l._
a-piece, malachite tables 400_l._, and chairs 150_l._ each.

[34] Longfellow has written some pleasing lines on “The Fiftieth
Birthday of M. Agassiz. May 28, 1857,” appended to “The Courtship of
Miles Standish,” 1858.

[35] The _sloth_ only deserves its name when it is obliged to attempt
to proceed along the ground; when it has any thing which it can lay
hold of it is agile enough.

[36] Dr. A. Thomson has communicated to _Jameson’s Journal_, No. 112,
a Description of the Caves in the North Island, with some general
observations on this genus of birds. He concludes them to have been
indolent, dull, and stupid; to have lived chiefly on vegetable food in
mountain fastnesses and secluded caverns.

In the picture-gallery at Drayton Manor, the seat of Sir Robert Peel,
hangs a portrait of Professor Owen, and in his hand is depicted the
tibia of a Moa.

[37] According to the law of correlation, so much insisted on by
Cuvier, a superior character implies the existence of its inferiors,
and that too in definite proportions and constant connections; so
that we need only the assurance of one character, to be able to
reconstruct the whole animal. The triumph of this system is seen in
the reconstruction of extinct animals, as in the above case of the
Dinornis, accomplished by Professor Owen.

[38] Not only at London, but at Paris, Vienna, Berlin, Turin. St.
Petersburg, and almost every other capital in Europe; at Liege, Caen,
Montpellier, Toulouse, and several other large towns,--wherever,
in fact, there are not great local obstacles,--the tendency of the
wealthier inhabitants to group themselves to the west is as strongly
marked as in the British metropolis. At Pompeii, and other ancient
towns, the same thing maybe noticed; and where the local configuration
of the town necessitates an increase in a different direction, the
moment the obstacle ceases houses spread towards the west.

[39] By far the most complete set of experiments on the Radiation
of Heat from the Earth’s Surface at Night which have been published
since Dr. Wells’s Memoir _On Dew_, are those of Mr. Glaisher, F.R.S.,
_Philos. Trans._ for 1847.

[40] The author is largely indebted for the illustrations in this new
field of research to Lieutenant Maury’s valuable work, _The Physical
Geography of the Sea_. Sixth edition. Harper, New York; Low, Son, and
Co., London.

[41] It is the chloride of magnesia which gives that damp sticky
feeling to the clothes of sailors that are washed or wetted with salt
water.

[42] This fraction rests on the assumption that the dilatation of the
substances of which the earth is composed is equal to that of glass,
that is to say, 1/18000 for 1°. Regarding this hypothesis, see Arago,
in the _Annuaire_ for 1834, pp. 177-190.

[43] Electricity, traversing excessively rarefied air or vapours,
gives out light, and doubtless also heat. May not a continual current
of electric matter be constantly circulating in the sun’s immediate
neighbourhood, or traversing the planetary spaces, and exerting in the
upper regions of its atmosphere those phenomena of which, on however
diminutive a scale, we have yet an unequivocal manifestation in our
Aurora Borealis?

[44] Could we by mechanical pressure force water into a solid state, an
immense quantity of heat would be set free.

[45] See Mr. Hunt’s popular work, _The Poetry of Science; or, Studies
of Physical Phenomena of Nature_. Third edition, revised and enlarged.
Bohn, 1854.

[46] Canton was the first who in England verified Dr. Franklin’s idea
of the similarity of lightning and the electric fluid, July 1752.

[47] This is mentioned in _Procli Diadochi Paraphrasis Ptolem._, 1635.
(Delambre, _Hist. de l’Astronomie ancienne_.)

[48] The first Variation-Compass was constructed, before 1525, by an
ingenious apothecary of Seville, Felisse Guillen. So earnest were
the endeavours to learn more exactly the direction of the curves of
magnetic declination, that in 1585 Juan Jayme sailed with Francisco
Gali from Manilla to Acapulco, for the sole purpose of trying in the
Pacific a declination instrument which he had invented.--_Humboldt._

[49] Gilbert was surgeon to Queen Elizabeth and James I., and died
in 1603. Whewell justly assigns him an important place among the
“practical reformers of the physical sciences.” He adopted the
Copernican doctrine, which Lord Bacon’s inferior aptitude for physical
research led him to reject.

[50] This illustration, it will be seen, does not literally correspond
with the details which precede it.

[51] Mr. Crosse gave to the meeting a general invitation to Fyne Court;
one of the first to accept which was Sir Richard Phillips, who, on
his return to Brighton, described in a very attractive manner, at the
Sussex Institution, Mr. Crosse’s experiments and apparatus; a report of
which being communicated to the _Brighton Herald_, was quoted in the
_Literary Gazette_, and thence copied generally into the newspapers of
the day.

[52] These experiments were performed at the expense of the Royal
Society, and cost 10_l._ 5_s._ 6_d._ In the Paper detailing the
experiments, printed in the 45th volume of the _Philosophical
Transactions_, occurs the first mention of Dr. Franklin’s name, and of
his theory of positive and negative electricity.--_Weld’s Hist. Royal
Soc._ vol. i. p. 467.

[53] In this year Andrew Crosse said: “I prophesy that by means of
the electric agency we shall be enabled to communicate our thoughts
instantaneously with the uttermost parts of the earth.”

[54] To which paper the writer is indebted for many of these details.

[55] These illustrations have been in the main selected and abridged
from papers in the _Companion to the Almanac_, 1858, and the _Penny
Cyclopædia_, 2d supp.

[56] Newton was, however, much pestered with inquirers; and a
Correspondent of the _Gentleman’s Magazine_, in 1784, relates that he
once had a transient view of a Ms. in Pope’s handwriting, in which
he read a verified anecdote relating to the above period. Sir Isaac
being often interrupted by ignorant pretenders to the discovery of
the longitude, ordered his porter to inquire of every stranger who
desired admission whether he came about the longitude, and to exclude
such as answered in the affirmative. Two lines in Pope’s Ms., as the
Correspondent recollects, ran thus:

    “‘Is it about the longitude you come?’
    The porter asks: ‘Sir Isaac’s not at home.’”

[57] In trying the merits of Harrison’s chronometers, Dr. Maskelyne
acquired that knowledge of the wants of nautical astronomy which
afterwards led to the formation of the Nautical Almanac.

[58] A slight electric shock is given to a man at a certain portion of
the skin; and he is directed the moment he feels the stroke to make a
certain motion, as quickly as he possibly can, with the hands or with
the teeth, by which the time-measuring current is interrupted.

[59] Through the calculations of M. Le Verrier.




GENERAL INDEX


  Abodes of the Blest, 58.

  Acarus of Crosse and Weeks, 218.

  Accuracy of Chinese Observers, 159.

  Adamant, What was it?, 123.

  Aeronautic Voyage, Remarkable, 169.

  Agassiz, Discoveries of, 127.

  Air, Weight of, 14.

  All the World in Motion, 11.

  Alluvial Land of Egypt, 110.

  Ancient World, Science of the, 1.

  Animals in Geological Times, 128.

  Anticipations of the Electric Telegraph, 220-224.

  Arago on Protection from Storms, 159.

  Arctic Climate, Phenomena of, 162.

  Arctic Explorations, Rae’s, 162.

  Arctic Regions, Scenery and Life of, 180.

  Arctic Temperature, 161.

  Armagh Observatory Level, Change of, 144.

  Artesian Fire-Springs, 118.

  Artesian Well of Grenelle, 114.

  Astronomer, Peasant, 101.

  Astronomer’s Dream verified, 88.

  Astronomers, Triad of Contemporary, 100.

  Astronomical Observations, Nicety of, 102.

  Astronomy and Dates on Monuments, 55.

  Astronomy and Geology, Identity of, 104.

  Astronomy, Great Truths of, 54.

  Atheism, Folly of, 3.

  Atlantic, Basin of the, 171.

  Atlantic, Gales of the, 171.

  Atlantic Telegraph, the, 226-228.

  Atmosphere, Colours of the, 147.

  Atmosphere compared to a Steam-engine, 152.

  Atmosphere, Height of, 147.

  Atmosphere, the, 146.

  Atmosphere, the purest, 150.

  Atmosphere, Universality of the, 147.

  Atmosphere weighed by Pascal, 148.

  Atoms of Elementary Bodies, 13.

  Atoms, the World of, 13.

  Aurora Borealis, Halley’s hypothesis of, 198.

  Aurora Borealis, Splendour of the, 165.

  Australian Cavern, Inmates of, 137.

  Australian Pouch-Lion, 137.

  Axis of Rotation, the, 11.


  Barometer, Gigantic, 151.

  Barometric Measurement, 151.

  Batteries, Minute and Vast, 204.

  Birds, Gigantic, of New Zealand, Extinct, 139.

  “Black Waters, the,” 182.

  Bodies, Bright, the Smallest, 31.

  Bodies, Compression of, 12.

  Bodies, Fall of, 16.

  Bottles and Currents at Sea, 172.

  Boulders, How transported to Great Heights, 105.

  Boyle on Colours, 49.

  Boyle, Researches of, 6.

  Brain, Impressions transmitted to, 235.

  Buckland, Dr., his Geological Labours, 127.

  Building-Stone, Wear of, 108.

  Burnet’s Theory of the Earth, 125.

  Bust, Magic, 36.


  Candle-flame, Nature of, 237.

  Canton’s Artificial Magnets, 196.

  Carnivora of Britain, Extinct, 132.

  Carnivores, Monster, of France, 138.

  Cataract, Great, in India, 183.

  Cat, Can it see in the Dark?, 51.

  Caves of New Zealand and its Gigantic Birds, 140.

  Cave Tiger or Lion of Britain, 133.

  Central Heat, Theory of, 116.

  Chabert, “the Fire King,” 192.

  Chalk Formation, the, 108.

  Changes on the Earth’s Surface, 142.

  Chantrey, Heat-Experiments by, 192.

  Children’s powerful Battery, 204.

  Chinese, the, and the Magnetic Needle, 194.

  Chronometers, Marine, How rated at Greenwich Observatory, 229.

  Climate, finest in the World, 149.

  Climate, Variations of, 148.

  Climates, Average, 149.

  Clock, How to make Electric, 212.

  Cloud-ring, the Equatorial, 156.

  Clouds, Fertilisation of, 151.

  Coal, Torbane-Hill, 123.

  Coal, What is it?, 123.

  Cold in Hudson’s Bay, 160.

  Colour of a Body, and its Magnetic Properties, 197.

  Colours and Tints, Chevreul on, 37.

  Colours most frequently hit in Battle, 36.

  Comet, the, of Donati, 240, 241.

  Comet, Great, of 1843, 84.

  Comets, Magnitude of, 84.

  Comets visible in Sunshine, 84.

  Computation, Power of, 10.

  Coney of Scripture, 137.

  Conic Sections, 10.

  Continent Outlines not fixed, 145.

  Corpse, How soon it decays, 237.

  “Cosmos, Science of the,” 10.

  Crosse, Andrew, his Artificial Crystals and Minerals, 216-219.

  Crosse Mite, the, 218.

  Crystallisation, Reproductive, 26.

  Crystallisation, Theory of, 24.

  Crystallisation, Visible, 25.

  Crystals, Immense, 24.

  “Crystal Vault of Heaven,” 55.


  Davy, Sir Humphry, obtains Heat from Ice, 190.

  Davy’s great Battery at the Royal Institution, 204.

  Day, Length of, and Heat of the Earth, 186.

  Day’s Length at the Poles, 65.

  Declination of the Needle, 197.

  Descartes’ Labours in Physics, 9.

  Desert, Intense Heat and Cold of the, 163.

  Dew-drop, Beauty of the, 157.

  Dew-fall in one year, 157.

  Dew graduated to supply Vegetation, 157.

  Diamond, Geological Age of, 122.

  Diamond Lenses for Microscopes, 40.

  “Diamond,” Newton’s Dog, 8.

  Dinornis elephantopus, the, 139, 140.

  Dinotherium, or Terrible Beast, the, 136.

  Diorama, Illusion of the, 37.


  Earth and Man compared, 22.

  Earth, Figure of the, 21.

  Earth, Mass and Density of, 21.

  Earth’s Annual Motion, 12.

  Earth’s Magnitude, to ascertain, 21.

  Earth’s Surface, Mean Temperature of, 23.

  Earth’s Temperature, Interior, 116.

  Earth’s Temperature Stationary, 23.

  Earth, the, a Magnet, 197.

  Earthquake, the Great Lisbon, 121.

  Earthquakes and the Moon, 121.

  Earthquakes, Rumblings of, 120.

  Earthquake-Shock, How to measure, 120.

  Earth-Waves, 119.

  Eclipses, Cause of, 74.

  Egypt, Alluvial Land of, 110.

  Electric Girdle for the Earth, 224.

  Electric Incandescence of Charcoal Points, 204.

  Electric Knowledge, Germs of, 207.

  Electric Light, Velocity of, 209.

  Electric Messages, Time lost in, 225.

  Electric Paper, 209.

  Electric Spark, Duration of, 209.

  Electric Telegraph, Anticipations of the, 220-224.

  Electric Telegraph, Consumption of, 224.

  Electric Telegraph in Astronomy and Longitude, 225.

  Electric Telegraph and Lightning, 226.

  Electric and Magnetic Attraction, Identity of, 210.

  Electrical Kite, Franklin’s, 213.

  Electricity and Temperature, 208.

  Electricity in Brewing, 209.

  Electricity, Vast Arrangement of, 208.

  Electricity, Water decomposed by, 208.

  Electricities, the Two, 214.

  Electro-magnetic Clock, Wheatstone’s, 211.

  Electro-magnetic Engine, Theory of, 210.

  Electro-magnets, Horse-shoe, 199.

  Electro-telegraphic Message to the Stars, 226.

  Elephant and Tortoise of India, 135.

  End of our System, 92.

  England in the Eocene Period, 129.

  English Channel, Probable Origin of, 105.

  Eocene Period, the, 129.

  Equatorial Cloud-ring, 156.

  “Equatorial Doldrums,” 156.

  Error upon Error, 185.

  Exhilaration in ascending Mountains, 163.

  Eye and Brain seen through a Microscope, 41.

  Eye, interior, Exploration of, 236.


  Fall of Bodies, Rate of, 16.

  Falls, Height of, 16.

  Faraday, Genius and Character of, 193.

  Faraday’s Electrical Illustrations, 214.

  “Father of English Geology, the,” 126.

  Fertilisation of Clouds, 151.

  Fire, Perpetual, 117.

  Fire-balls and Shooting Stars, 89.

  Fire-Springs, Artesian, 118.

  Fishes, the most Ancient, 132.

  Flying Dragon, the, 130.

  Force neither created nor destroyed, 18.

  Force of Running Water, 114.

  Fossil Human Bones, 131.

  Fossil Meteoric Stones, none, 92.

  Fossil Rose, none, 142.

  Foucault’s Pendulum Experiments, 22.

  Franklin’s Electrical Kite, 213.

  Freezing Cavern in Russia, 115.

  Fresh Water in Mid-Ocean, 182.


  Galilean Telescope, the, 93.

  Galileo, What he first saw with the Telescope, 93.

  Galvani and Volta, 205.

  Galvanic Effects, Familiar, 203.

  Galvanic Waves on the same Wire, Non-interference of, 225.

  “Gauging the Heavens,” 58.

  Genius, Relics of, 5.

  Geology and Astronomy, Identity of, 104.

  Geology of England, 105.

  Geological Time, 143.

  George III., His patronage of Herschel, 95.

  Gilbert on Magnetic and Electric forces, 201.

  Glacial Theory, by Hopkins, 105.

  Glaciers, Antiquity of, 109.

  Glaciers, Phenomena of, Illustrated, 108.

  Glass, Benefits of, to Man, 92.

  Glass broken by Sand, 26.

  Glyptodon, the, 137.

  Gold, Lumps of, in Siberia, 124.

  Greenwich Observatory, Chronometers rated at, 229-232.

  Grotto del Cane, the, 112.

  Gulf-Stream and the Temperature of London, 115.

  Gunpowder-Magazines, Danger to, 216.

  Gymnotus and the Voltaic Battery, 206.

  Gyroscope, Foucault’s, 22.


  Hail and Storms, Protection against, 159.

  Hail-storm, Terrific, 160.

  Hair, Microscopical Examination of, 41.

  Harrison’s Prize Chronometers, 229-232.

  Heat and Evaporation, 188.

  Heat and Mechanical Power, 188.

  Heat by Friction, 189.

  Heat, Distinctions of, 187.

  Heat, Expenditure of, by the Sun, 186.

  Heat from Gas-lighting, 189.

  Heat from Wood and Ice, 190.

  Heat, Intense, Protection from, 191, 192.

  Heat, Latent, 187.

  Heat of Mines, 188.

  Heat, Nice Measurement of, 186.

  Heat, Origin of, in our System, 87.

  Heat passing through Glass, 189.

  Heat, Repulsion by, 191.

  Heated Metals, Vibration of, 188.

  Heavy Persons, Lifting, 17.

  Heights and Distances, to Calculate, 19.

  Herschel’s Telescopes at Slough, 95.

  Highton’s Minute Battery, 204.

  Hippopotamus of Britain, 135.

  “Horse Latitudes, the,” 173.

  Horse, Three-hoofed, 138.

  Hour-glass, Sand in the, 20.


  Ice, Heat from, 190.

  Ice, Warming with, 190.

  Icebergs of the Polar Seas, 180.

  Iguanodon, Food of the, 129.

  Improvement, Perpetuity of, 5.

  Inertia Illustrated, 14.


  Jerusalem, Temple of, How protected from Lightning, 167.

  Jew’s Harp, Theory of the, 29.

  Jupiter’s Satellites, Discovery of, 80.


  Kaleidoscope, Sir David Brewster’s, 43.

  Kaleidoscope, the, thought to be anticipated, 43.

  Kircher’s “Magnetism,” 194.


  Leaning Tower, Stability of, 15.

  Level, Curious Change of, 144.

  Leyden Jar, Origin of the, 216.

  Lifting Heavy Persons, 17.

  Light, Action of, on Muscular Fibres, 34.

  Light, Apparatus for Measuring, 32.

  Light from Buttons, 36.

  Light, Effect of, on the Magnet, 198.

  Light from Fungus, 36.

  Light from the Juice of a Plant, 35.

  Light, Importance of, 34.

  Light, Minuteness of, 34.

  Light Nights, 35.

  Light, Polarisation of, 33.

  Light, Solar and Artificial Compared, 29.

  Light, Source of, 29.

  Light, Undulatory Scale of, 30.

  Light, Velocity of, 31.

  Light, Velocity of, Measured by Fizeau, 32.

  Light from Quartz, 51.

  Lightning-Conductor, Ancient, 167.

  Lightning-Conductors, Service of, 166.

  Lightning Experiment, Fatal, 214.

  Lightning, Photographic Effects of, 45.

  Lightning produced by Rain, 166.

  Lightning, Sheet, What is it?, 165.

  Lightning, Varieties of, 165.

  Lightning, Various Effects of, 168.

  Log, Invention of the, 173.

  London Monument used as an Observatory, 103.


  “Maestricht Saurian Fossil,” the, 141.

  Magnet, Power of a, 195.

  Magnets, Artificial, How made, 195.

  Magnetic Clock and Watch, 211.

  Magnetic Electricity discovered, 199.

  Magnetic Hypotheses, 193.

  Magnetic Needle and the Chinese, 194.

  Magnetic Poles, North and South, 201.

  Magnetic Storms, 202.

  “Magnetism,” Kircher’s, 194.

  Malachite, How formed, 124.

  Mammalia in Secondary Rocks, 130.

  Mammoth of the British Isles, 133.

  Mammoth, Remains of the, 134.

  Mars, the Planet, Is it inhabited?, 82.

  Mastodon coexistent with Man, 135.

  Matter, Divisibility of, 14.

  Maury’s Physical Geography of the Sea, 170.

  Mediterranean, Depth of, 176.

  Megatherium, Habits of the, 135.

  Mercury, the Planet, Temperature of, 82.

  Mer de Glace, Flow of the, 110.

  Meteoric Stones, no Fossil, 92.

  Meteorites, Immense, 91.

  Meteorites from the Moon, 89.

  Meteors, Vast Shower of, 91.

  Microscope, the Eye, Brain, and Hair seen by, 41.

  Microscope, Fish-eye, How to make, 40.

  Microscope, Invention of the, 39.

  Microscope for Mineralogists, 42.

  Microscope and the Sea, 42.

  Microscopes, Diamond Lenses for, 40.

  Microscopes, Leuwenhoeck’s, 40.

  Microscopic Writing, 42.

  Milky Way, the, Unfathomable, 85.

  Mineralogy and Geometry, Union of, 25.

  Mirror, Magic, How to make, 43.

  Moon’s Attraction, the, 73.

  Moon, Has it an Atmosphere?, 69.

  Moon, Life in the, 71.

  Moon, Light of the, 70.

  Moon, Mountains in, 72.

  Moon, Measuring the Earth by, 74.

  Moon seen through the Rosse Telescope, 72.

  Moon, Scenery of, 71.

  Moon and Weather, the, 73.

  Moonlight, Heat of, 70.

  “More Worlds than One,” 56, 57.

  Mountain-chains, Elevation of, 107.

  Music of the Spheres, 55.

  Musket-balls found in Ivory, 237.


  Natural and Supernatural, the, 6.

  Nautical Almanac, Errors in, 185.

  Nebulæ, Distances of, 85.

  Nebular Hypothesis, the, 86.

  Neptune, the Planet, Discovery of, 83.

  Newton, Sir Isaac, his “Apple-tree,” 8.

  Newton upon Burnet’s Theory of the Earth, 125.

  Newton’s Dog “Diamond,” 8.

  Newton’s first Reflecting Telescope, 94.

  Newton’s “Principia,” 9.

  Newton’s Rooms at Cambridge, 7.

  Newton’s Scale of Colours, 49.

  Newton’s Soap-bubble Experiments, 49, 50.

  New Zealand, Extinct Birds of, 139.

  Niagara, the Roar of, 28.

  Nineveh, Rock-crystal Lens found at, 39.

  Non-conducting Bodies, 215.

  Nothing Lost in the Material World, 18.


  Objects really of no Colour, 37.

  Objects, Visibility of, 30.

  Observation, the Art of, 3.

  Observatory, Lacaille’s, 101.

  Observatory, the London Monument, 103.

  Observatory, Shirburn Castle, 101.

  Ocean and Air, Depths of unknown, 174.

  Ocean Highways, 184.

  Ocean, Stability of the, 12.

  Ocean, Transparency of the, 171.

  “Oldest piece of Wood upon the Earth,” 142.

  Optical Effects, Curious, at the Cape, 38.

  Optical Instruments, Late Invention of, 100.

  Oxford and Cambridge, Science at, 1.


  Pascal, How he weighed the Atmosphere, 148.

  Pebbles, on, 106.

  Pendulum Experiments, 16-22.

  Pendulum, the Earth weighed by, 200.

  Pendulums, Influence of on each other, 200.

  Perpetual Fire, 117.

  Petrifaction of Human Bodies, 131.

  Phenomena, Mutual Relations of, 4.

  Philosophers’ False Estimates, 5.

  Phosphorescence of Plants, 35.

  Phosphorescence of the Sea, 35.

  Photo-galvanic Engraving, 47.

  Photograph and Stereoscope, 47.

  Photographic effects of Lightning, 45.

  Photographic Surveying, 46.

  Photographs on the Retina, 236.

  Photography, Best Sky for, 45.

  Photography, Magic of, 44.

  Pisa, Leaning Tower of, 15.

  Planetary System, Origin of our, 86.

  Planets, Diversities of, 79.

  Planetoids, List of the, and their Discoverers, 239.

  Plato’s Survey of the Sciences, 2.

  Pleiades, the, 77.

  Plurality of Worlds, 57.

  Polar Ice, Immensity of, 181.

  Polar Iceberg, 180.

  Polarisation of Light, 33.

  Pole, Open Sea at the, 181.

  Pole-Star of 4000 years ago, 76.

  Profitable Science, 139.

  Pterodactyl, the, 130.

  Pyramid, Duration of the, 14.


  Quartz, Down of, 42.


  Rain, All in the World, 155.

  Rain, an Inch on the Atlantic, 156.

  Rain-Drops, Size of, 154.

  Rain, How the North Wind drives it away, 154.

  Rain, Philosophy of, 153.

  Rainless Districts, 155.

  Rain-making Vapour, from South to North, 152.

  Rainy Climate, Inordinate, 154.

  Red Sea and Mediterranean Levels, 175.

  Red Sea, Colour of, 176.

  Repulsion of Bodies, 216.

  Rhinoceros of Britain, 135.

  River-water on the Ocean, 181.

  Rose, no Fossil, 142.

  Rosse, the Earl of, his “Telescope,” 96-99.

  Rotation-Magnetism discovered, 199.

  Rotation, the Axis of, 11.


  St. Paul’s Cathedral, how protected from Lightning, 167.

  Salt, All in the Sea, 179.

  Salt Lake of Utah, 113.

  Salt, Solvent Action of, 115.

  Saltness of the Sea, How to tell, 179.

  Sand in the Hour-glass, 20.

  Sand of the Sea and Desert, 106.

  Saturn’s Ring, Was it known to the Ancients?, 81.

  Schwabe, on Sun-Spots, 68.

  Science at Oxford and Cambridge, 1.

  Science of the Ancient World, 1.

  Science, Theoretical, Practical Results of, 4.

  Sciences, Plato’s Survey of, 2.

  Scientific Treatise, the Earliest English, 5.

  Scoresby, Dr., on the Rosse Telescope, 99.

  Scratches, Colours of, 36.

  Sea, Bottles and Currents at, 172.

  Sea, Bottom of, a burial-place, 177.

  Sea, Circulation of the, 170.

  Sea, Climates of the, 170.

  Sea, Deep, Life of the, 174.

  Sea, Greatest ascertained Depth of, 175.

  Sea, Solitude at, 172.

  Sea, Temperature of the, 170.

  Sea, Why is it Salt?, 177.

  Seas, Primeval, Depth of, 234.

  Sea-breezes and Land-breezes illustrated, 150.

  Sea-milk, What is it?, 176.

  Sea-routes, How shortened, 184.

  Sea-shells and Animalcules, Services of, 234.

  Sea-shells, Why found at Great Heights, 106.

  Sea-water, to imitate, 235.

  Sea-water, Properties of, 179.

  Serapis, Temple of, Successive Changes in, 111.

  Sheep, Geology of the, 138.

  Shells, Geometry of, 232.

  Shells, Hydraulic Theory of, 233.

  Siamese Twins, the, galvanised, 203.

  Skin, Dark Colour of the, 63.

  Smith, William, the Geologist, 126.

  Snow, Absence of in Siberia, 159.

  Snow, Impurity of, 158.

  Snow Phenomenon, 158.

  Snow, Warmth of, in Arctic Latitudes, 158.

  Snow-capped Volcano, the, 119.

  Snow-crystals observed by the Chinese, 159.

  Soap-bubble, Science of the, 48.

  Solar Heat, Extreme, 63.

  Solar System, Velocity of, 59.

  Sound, Figures produced by, 28.

  Sound in rarefied Air, 27.

  Sounding Sand, 27.

  Space, Infinite, 86.

  Speed, Varieties of, 17.

  Spheres, Music of the, 55.

  Spots on the Sun, 67.

  Star, Fixed, the nearest, 78.

  Stars’ Colour, Change in, 77.

  Star’s Light sixteen times that of the Sun, 79.

  Stars, Number of, 75.

  Stars seen by Daylight, 102.

  Stars that have disappeared, 76.

  Stars, Why created, 75.

  Stereoscope and Photograph, 47.

  Stereoscope simplified, 47.

  Storm, Impetus of, 164.

  Storms, Revolving, 164.

  Storms, to tell the Approach of, 163.

  Storm-glass, How to make, 164.

  Succession of life in Time, 128.

  Sun, Actinic Power of, 62.

  Sun and Fixed Stars’ Light compared, 64.

  Sun and Terrestrial Magnetism, 64.

  “Sun Darkened,” 64.

  Sun, Great Size of, on Horizon, 61.

  Sun, Heating Power of, 62.

  Sun, Lost Heat of, 103.

  Sun, Luminous Disc of, 60.

  Sun, Nature of the, 59, 238.

  Sun, Spots on, 67.

  Sun, Translatory Motion of, 61.

  Sun’s Distance by the Yard Measure, 66.

  Sun’s Heat, Is it decreasing?, 65.

  Sun’s Rays increasing the Strength of Magnets, 196.

  Sun’s Light and Terrestrial Lights, 61.

  Sun-dial, Universal, 65.


  Telegraph, the Atlantic, 226.

  Telegraph, the Electric, 220.

  Telescope and Microscope, the, 38.

  Telescope, Galileo’s, 93.

  Telescope, Herschel’s, 95.

  Telescope, Newton’s first Reflecting, 94.

  Telescopes, Antiquity of, 94.

  Telescopes, Gigantic, proposed, 99.

  Telescopes, the Earl of Rosse’s, 96.

  Temperature and Electricity, 208.

  Terrestrial Magnetism, Origin of, 200.

  Thames, the, and its Salt-water Bed, 182.

  Threads, the two Electric, 215.

  Thunderstorm seen from a Balloon, 169.

  Tides, How produced by Sun and Moon, 66.

  Time an Element of Force, 19.

  Time, Minute Measurement of, 194.

  Topaz, Transmutation of, 37.

  Trilobite, the, 138.

  Tuning-fork a Flute-player, 28.

  Twilight, Beauty of, 148.


  Universe, Vast Numbers in, 75.

  Utah, Salt Lake of, 113.


  Velocity of the Solar System, 59.

  Vesta and Pallas, Speculations on, 82.

  Vesuvius, Great Eruptions of, 119.

  Vibration of Heated Metals, 188.

  Visibility of Objects, 30.

  Voice, Human, Audibility of, 27.

  Volcanic Action and Geological Change, 118.

  Volcanic Dust, Travels of, 119.

  Volcanic Islands, Disappearance of, 117.

  Voltaic Battery and the Gymnotus, 206.

  Voltaic Currents in Mines, 206.

  Voltaic Electricity discovered, 205.


  Watches, Harrison’s Prize, 229.

  Water decomposed by Electricity, 208.

  Water, Running, Force of, 114.

  Waters of the Globe gradually decreasing, 113.

  Water-Purifiers, Natural, 234.

  Waterspouts, How formed in the Java Sea, 160.

  Waves, Cause of, 183.

  Waves, Force of, 184.

  Waves, Rate of Travelling, 183.

  Wenham-Lake Ice, Purity of, 161.

  West, Superior Salubrity of, 150.

  “White Water,” and Luminous Animals at Sea, 173.

  Winds, Transporting Power of, 163.

  Wollaston’s Minute Battery, 204.

  World, All the, in Motion, 11.

  World, the, in a Nutshell, 13.

  Worlds, More than One, 56.

  Worlds to come, 58.


LONDON: ROBSON, LEVEY, AND FRANKLYN, GREAT NEW STREET AND PETTER LANE,
E.C.




Transcriber’s Notes


Punctuation, hyphenation, and spelling were made consistent when a
predominant preference was found in this book; otherwise they were not
changed.

Simple typographical errors were corrected; occasional unbalanced
quotation marks retained.

Ambiguous hyphens at the ends of lines were retained.

Some numbers in equations include a hyphen to separate the fractional
and integer parts. These are not minus signs, which, like other
arithmetic operators, are surrounded by spaces.

The original book apparently used a smaller font for multiple reasons,
but as those reasons were not always clear to the Transcriber, smaller
text is indented by 2 spaces in the Plain Text version of this eBook,
and is displayed smaller in other versions.

Footnotes, originally at the bottoms of pages, have been collected and
repositioned just before the Index.

Page 59: “95 × 1·623 = 154·185” was misprinted as “95 + 1·623 =
154·185” and has been corrected here.

The Table of Contents does not list the “Phenomena of Heat” chapter,
which begins on page 185; nor the Index, which begins on page 242.

Page 95: “adjustible” was printed that way.

Page 151: Missing closing quotation mark added after “rapidly evaporate
in space.” It may belong elsewhere.

Page 221: Missing closing quotation mark not added for phrase beginning
“it is a fine invention”.









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