Among the innumerable hypotheses which human ingenuity has framed to
explain the phenomena which surround the globe, the two which have found
most ready acceptance have been termed respectively the CHEMICAL, and
the NEBULAR or mechanical hypothesis. By the first the solid crust is
supposed to have contained abundance of potassium, sodium, calcium,
magnesium, and other metallic elements. The percolating waters, coming
in contact with these substances, produce combinations resulting in the
conversion of the metals into their oxides--potash, soda, lime, and
magnesia--all of which enter largely into the composition of volcanic
rocks. The second hypothesis involves the idea of an original
incandescent mass of vapour, succeeded by a great and still existing
central fire.
This idea of a great central fire is a very ancient hypothesis: admitted
by Descartes, developed by Leibnitz, and advocated by Buffon, it is
supposed to account for many phenomena otherwise inexplicable; and it is
confirmed by a crowd of facts, and adopted, or at least not opposed, by
the leading authorities of the age. Dr. Buckland makes it the basis of
his Bridgewater treatise. Herschel, Hind, Murchison, Lyell, Phillips,
and other leading English astronomers and geologists give a cautious
adhesion to the doctrine. The following are some of the principal
arguments adduced in support of the hypothesis, for, in the nature of
the proofs it admits of, it can be no more.
When we descend into the interior of a mine, it is found that the
temperature rises in an appreciable manner, and that it increases with
the depth below the surface.
The high temperature of the waters in Artesian wells when these are very
deep, testifies to a great heat of the interior of the earth.
The thermal waters which issue from the earth--of which the temperature
sometimes rises to 100° Centigrade and upwards--as, for instance, the
Geysers of Iceland--furnish another proof in support of the hypothesis.
Modern volcanoes are said to be a visible demonstration of the existence
of central heat. The heated gases, the liquid lava, the flames which
escape from their craters, all tend to prove sufficiently that the
interior of the globe has a temperature prodigiously elevated as
compared with that at its surface.
The disengagement of gases and burning vapours through the accidental
fissures in the crust, which accompany earthquakes, still further tends
to establish the existence of a great heat in the interior of the globe.
We have already said that the temperature of the globe increases about
one degree for every sixty or seventy feet of depth beneath its surface.
The correctness of this observation has been verified in a great number
of instances--indeed, to the greatest depth to which man has penetrated,
and been able to make use of the thermometer. Now, as we know exactly
the length of the radius of the terrestrial sphere, it has been
calculated from this progression of temperature, supposing it to be
regular and uniform, that the centre of the globe ought to have at the
present time a mean temperature of 195,000° Centigrade. No matter could
preserve its solid state at this excessive temperature; it follows,
then, that the centre of the globe, and all parts near the centre, must
be in a permanent state of fluidity.
The works of Werner, of Hutton, of Leopold von Buch, of Humboldt, of
Cordier, W. Hopkins, Buckland, and some other English philosophers, have
reduced this hypothesis to a theory, on which has been based, to a
considerable extent, the whole science of modern geology; although,
properly speaking, and in the popular acceptation of the term, that
science only deals with the solid crust of the earth.
The nebular theory thus embraces the whole solar system, and, by
analogy, the universe. It assumes that the SUN was originally a mass of
incandescent matter, that vast body being brought into a state of
evolution by the action of laws to which the Creator, in His divine
wisdom, has subjected all matter. In consequence of its immense
expansion and attenuation, the exterior zone of vapour, expanding beyond
the sphere of attraction, is supposed to have been thrown off by
centrifugal force. This zone of vapour, which may be supposed at one
time to have resembled the rings of Saturn, would in time break up into
several masses, and these masses coalescing into globes, would (by the
greater power of attraction which they would assume as consolidated
bodies) revolve round the sun, and, from mechanical considerations,
would also revolve with a rotary motion on their own axes.
This doctrine is applied to all the planets, and assumes each to have
been in a state of incandescent vapour, with a central incandescent
nucleus. As the cooling went on, each of these bodies may be supposed to
have thrown off similar masses of vapour, which, by the operation of the
same laws, would assume the rotary state, and, as satellites, revolve
round the parent planet. Such, in brief, was the grand conception of
Laplace; and surely it detracts nothing from our notions of the
omnipotence of the Creator that it initiates the creation step by step,
and under the laws to which matter is subjected, rather than by the
direct fiat of the Almighty. The hypothesis assumes that as the vaporous
mass cooled by the radiation of heat into space, the particles of matter
would approximate and solidify.
That the figure of the earth is such as a very large mass of matter in a
state of fluidity would assume from a state of rotation, seems to be
admitted, thus corroborating the speculations of Leibnitz, that the
earth is to be looked on as a heated fluid globe, cooled, and still
cooling at the surface, by radiation of its superfluous heat into space.
Mr. W. Hopkins[7] has put forth some strong but simple reasons in
support of a different theory; although he does not attempt to solve the
problem, but leaves the reader to form his own conclusions. As far as we
have been able to follow his reasoning we gather from it that:--
[7] See _Phil. Transactions_, 1839-40-42; also, _Quarterly Journal of
the Geological Society_, vol. viii., p. 56.
If the earth were a fluid mass cooled by radiation, the cooled parts
would, by the laws of circulating fluids, descend towards the centre,
and be replaced on the surface by matter at a higher temperature.
The consolidation of such a mass would, therefore, be accompanied by a
struggle for superiority between pressure and temperature, both of which
would be at their maximum at the centre of the mass.
At the surface, it would be a question of rapidity of cooling, by
radiation, as compared with the internal condition--for comparing which
relations we are without data; but on the result of which depends
whether such a body would most rapidly solidify at the surface by
radiation, or at the centre by pressure.
The effect of the first would be solidification at the surface, followed
by condensation at the centre through pressure. There would thus be two
masses, a spherical fluid nucleus, and a spherical shell or envelope,
with a large zone of semi-fluid, pasty matter between, continually
changing its temperature as its outer or inner surface became converted
to the solid state.
If pressure, on the other hand, gained the victory, the centre would
solidify before the circulation of the heated matter had ceased; and the
solidifying process would proceed through a large portion of the globe,
and even approach the surface before that would become solid. In other
words, solidification would proceed from the centre until the
diminishing power of pressure was balanced by radiation, when the
gradual abstraction of heat would allow the particles to approximate and
become solid.
The terrestrial sphere may thus be a solid indurated mass at the centre,
with a solid stony crust at the surface, and a shifting viscous, but
daily-decreasing, mass between the two; a supposition which the
diminished and diminishing frequency and magnitude of volcanic and other
eruptive convulsions seem to render not improbable.
It is not to be supposed that amongst the various hypotheses of which
the cosmogony of the world has been the object, a literal acceptation of
the scriptural account finds no defenders among men of science. “Why,”
asks one of these writers,[8] after some scornful remarks upon the
geologists and their science--“why an omnipotent Creator should have
called into being a gaseous-granite nebulous world, only to have to cool
it down again, consisting as it does of an endless variety of
substances, should even have been supposed to be originally constituted
of the matter of granite alone, for nothing else was provided by the
theory, nobody can rationally explain. How the earth’s centre now could
be liquid fire with its surface solid and cold and its seas not boiling
caldrons, has never been attempted to be accounted for. How educated
gentlemen, engaged in scientific investigations, ever came to accept
such a monstrously stupid mass of absurdities as deductions of
‘science,’ and put them in comparison with the rational account of the
creation given by Moses, is more difficult to understand than even this
vague theory itself, which it is impossible to describe.
[8] “Fresh Springs of Truth.” R. Griffin and Co.
“Of the first creation of the chaotic world,” the same writer goes on to
say, “or the material elements, before they were shaped into their
present forms, we can scarce have the most vague conception. All our
experience relates to their existing conditions. But knowing somewhat of
the variety of the constituent elements and their distinct properties,
by which they manifest their existence to us, we cannot conceive of
their creation without presupposing a Divine wisdom, and--if I may say
so, with all reverence, and only to suit our human notions--a Divine
ingenuity,” and he follows for six days the operations as described by
Moses, with a running comment. When light is created, the conception of
the work becomes simpler to our minds. Its least manifestation would
suffice at once to dispel darkness, and yet how marvellous is the light!
In the second day’s work the firmament of heaven is opened; the expanse
of the air between the heavens and the earth, dividing the waters above
from the waters below, is the work recorded as performed. Not till the
third day commence the first geological operations. The waters of the
earth are gathered together into seas, and the dry land is made to
appear. It is now that we can imagine that the formation of the primary
strata commenced, while by some of the internal forces of matter the
earth was elevated and stood above the waters.
Immediately the dry land is raised above and separated from the waters
the fiat goes forth, “Let the earth _bring forth_ grass, and herb and
tree;” vegetable life begins to exist, and the world is first decorated
with its beauteous flora, with all its exquisite variety of forms and
brilliancy of colouring, with which not even Solomon in all his glory
can compare. In like manner, on the sixth day the earth is commanded to
bring forth land-animals--the living creature “after his kind,” cattle
and creeping thing, and beast of the earth, “after his kind;” and last
of all, but on the same day, man is created, and made the chief and
monarch of God’s other living creatures--for that is “man’s place in
Nature.” “Let us now see,” he continues, “how this history came to be
discredited by the opposition of a falsely so-called ‘science’ of
geology, that, while spared by our theologians, has since pulled itself
to pieces. The first step in the false inductions geology made arose
from the rash deduction, that the order in which the fossil remains of
organic being were found deposited in the various strata necessarily
determined the order of their creation; and the next error arose from
blindly rushing to rash conclusions, and hasty generalisation from a
very limited number of facts, and the most imperfect investigations.
There were also (and, indeed, are still) some wild dogmatisms as to the
time necessary to produce certain geologic formations; but the
absurdities of science culminated when it adopted from Laplace the
irrational and unintelligible theory of a _natural_ origin for the world
from a nebula of gaseous granite, intensely hot, and supposed to be
gradually cooled while gyrating senselessly in space.”
In this paper the writer does not attempt to deal with the various
phenomena of volcanoes, earthquakes, hot springs, and other matters
which are usually considered as proofs of great internal heat. Mr. Evan
Hopkins, C.E., F.G.S., is more precise if less eloquent. He shows that,
in tropical countries, plains of gravel may in a day be converted into
lagoons and marshes; that by the fall of an avalanche rivers have been
blocked up, which, bursting their banks, have covered many square miles
of fertile country with several feet of mud, sand, and gravel. “Two
thousand four hundred years ago,” he says, “Nineveh flourished in all
its grandeur, yet it is now buried in oblivion, and its site overwhelmed
with sand. Look at old Tyre, once the queen of cities and mistress of
the sea. She was in all her pride two thousand four hundred and forty
years ago. We now see but a bare rock in the sea, on which fishermen
spread their nets! A thousand years ago, according to Icelandic
histories, Greenland was a fertile land in the south, and supported a
large population. Iceland at that period was covered with forests of
birch and fir, and the inhabitants cultivated barley and other grain. We
may, therefore, conclude, with these facts before us, that there is no
necessity to assign myriads of ages to terrestrial changes, as assumed
by geologists, as they can be accounted for by means of alterations
effected during a few thousand years, for the surface of the earth is
ever changing.
“Grant geological speculators,” Mr. Hopkins continues, “a few millions
of centuries, with a command over the agencies of Nature to be brought
into operation when and how they please, and they think they can form a
world with every variety of rock and vegetation, and even transform a
worm into a man! Yet the wisest of our philosophers would be puzzled if
called upon to explain why fluids become spheres, as dew-drops; why
carbonate of lime acquires in solidifying from a liquid the figure of an
obtuse rhomboihedron, silica of a six-sided prism; and why oxygen and
hydrogen gases produce both _fire_ and _water_. And what do they gain,”
he proceeds to ask, “by carrying back the history of the world to these
myriads of centuries? Do they, by the extension of the period to
infinity, explain how the ‘_Original_’ materials were created? But,” he
adds, “geologists are by no means agreed in their assumed geological
periods! The so-called glacial period has been computed by some to be
equal to about eighty-three thousand years, and by others at even as
much as twelve hundred and eighty millions of years! Were we to ask for
a _demonstrative proof_ of any given deposit being more than four or
five thousand years old, they could not give it. Where is Babylon, the
glory of the kingdoms? Look at Thebes, and behold its colossal columns,
statues, temples, obelisks, and palaces desolated; and yet those great
cities flourished within the last three thousand years. Even Pompeii and
Herculaneum were all but lost to history! What,” he asks after these
brief allusions to the past--“what, as a matter of fact, have geologists
discovered, as regards the great terrestrial changes, more than was
known to Pythagoras and the ancient philosophers who taught, two
thousand three hundred and fifty years ago, ‘that the surface of the
earth was ever changing--solid land converted into sea, sea changed into
dry land, marine shells lying far distant from the deep, valleys
excavated by running water, and floods washing down hills into the
sea?’”
In reference to the argument of the vast antiquity of the earth, founded
on elevation of coasts at a given rate of upheaval, he adduces many
facts to show that upheavals of equal extent have occurred almost within
the memory of man. Two hundred and fifty years ago Sir Francis Drake,
with his fleet, sailed into Albemarle Sound through Roanoke Outlet,
which is now a sand-bank above the reach of the highest tides. Only
seventy years ago it was navigable by vessels drawing twelve feet of
water. The whole American coast, both on the Atlantic and Pacific, have
undergone great changes within the last hundred years. The coast of
South America has, in some places, been upheaved twenty feet in the last
century; in others, a few hundred miles distant, it has been depressed
to an equal extent. A transverse section from Rio Santa Cruz to the base
of the Cordilleras, and another in the Rio Negro, in Patagonia, showed
that the whole sedimentary series is of recent origin. Scattered over
the whole at various heights above the sea, from thirteen hundred feet
downwards, are found recent shells of _littoral_ species of the
neighbouring coast--denoting upheavals which might have been effected
during the last three thousand years.
Coming nearer home, he shows that in 1538 the whole coast of Pozzuoli,
near Naples, was raised twenty feet in a single night. Then, with regard
to more compact crystalline or semi-crystalline rocks, no reliable
opinion can be formed on mere inspection. Two blocks of marble may
appear precisely alike, though formed at different periods. A crystal of
carbonate of lime, formed in a few years, would be found quite perfect,
and as compact as a crystal formed during many centuries. Nothing can be
deduced from the process of petrifaction and crystallisation, unless
they enclose relics of a known period. At San Filippo, a solid mass of
limestone thirty feet thick has been formed in about twenty years. A
hard stratum of travertine a foot thick is obtained, from these thermal
springs, in the course of four months. Nor can geologists demonstrate
that the Amiens deposits, in which the flint-implements occur, are more
than three or four thousand years old.
The causes of these changes and mutations are referred by some persons
to floods, or to pre-Adamite convulsions, whereas the cause is in
constant operation; they are due to an invisible and subtle power which
pervades the air, the ocean, and the rocks below--in which all are
wrapped and permeated--which is universally present, namely,
magnetism--a power always in operation, always in a state of activity
and tension. It has an attractive power towards the surface of the
earth, as well as a directive action from pole to pole. “It is, indeed,”
he adds, emphatically, “the _terrestrial gravitation_. Magnetic needles
freely suspended show its meridional or directive polar force, and that
the force converges at two opposite parts, which are bounded by the
Antarctic and Arctic circles.”
This polar force, like a stream, is constantly moving from pole to pole;
and experiment proves that this movement is from the South Pole to the
North. “Hence the various terrestrial substances, solids and fluids,
through which this subtle and universal power permeates, are controlled,
propelled, and modified over the entire surface of our globe, commencing
at the south and dissolving at the north. Thus, all terrestrial matter
moves towards the Arctic region, and finally disappears by dissolution
and absorption, to be renewed again and again in the Antarctic Sea to
the end of time.”
In order to prove that the north polar basin is the receptacle of the
final dissolution of all terrestrial substances, Mr. Hopkins quotes the
Gulf Stream. Bottles, tropical plants, and wrecks cast into the sea in
the South Atlantic, are carried to Greenland in a comparatively short
time. The great _tidal_ waves commence at the fountain-head in the
Antarctic circle, impinge against the south coast of Tierra del Fuego,
New Zealand, and Tasmania, and are then propelled northward in a series
of undulations. The South Atlantic stream, after doubling the Cape of
Good Hope, moves towards the Guinea coast, bends towards the Caribbean
Sea, producing the trade winds; again leaves Florida as the Gulf Stream,
and washes the coasts of Greenland and Norway, and finally reaches the
north polar basin.
Again the great polar force shows itself in the arrangement of the
mineral structure below. In all the primary rocks in every quarter of
the globe where they have been examined, its action is recognised in
giving to the crystalline masses--granites and their laminated
elongations--a polar grain and vertical cleavage. “Had it been possible
to see our globe stripped of its sedimentary deposits and its oceanic
covering, we should see it like a gigantic melon, with a uniform grain
extending from pole to pole.” This structure appears to give polarity to
earthquakes--thermal waters and earthquakes--which are all traceable in
the direction of the polar grain or cleavage from north to south.
In England, for instance, thermal and saline springs are traceable from
Bath, through Cheltenham, to Dudley. In Central France, mineral springs
occur in lines, more or less, north and south. All the known
salt-springs in South America occur in meridional bands. Springs of
chloride of sodium in the Eastern Cordilleras stretch from Pinceima to
the Llanoes de Meta, a distance of 200 miles. The most productive
metalliferous deposits are found in meridional bands. The watery
volcanoes in South America are generally situated along the lines of the
meridional splits and the secondary eruptive pores on the transverse
fractures. The sudden ruptures arising locally from increasing tension
of the polar force, and the rapid expansion of the generated gases,
produce a vibratory jar in the rocky structure below, which being
propagated along the planes of the polar cleavage, gives rise to great
superficial oscillations, and thus causes earthquakes and subterranean
thunder for thousands of miles, from south to north.
In 1797, the district round the volcano of Tunguraqua in Quito, during
one of the great meridional shocks, experienced an undulating movement,
which lasted upwards of four minutes, and this was propagated to the
shores of the Caribbean Sea.
All these movements demonstrated, according to Mr. Hopkins, that the
land as well as the ocean moves from the south pole and north pole, and
that the magnetic power has a tendency to proceed from pole to pole in a
_spiral_ path from south-east to north-west, a movement which produces
an apparent change in the equinoxes, or the outer section of the plane
of the ecliptic with the equator, a phenomenon known to astronomers as
the precession of the equinoxes.
Such is a very brief summary of the arguments by which Mr. Evan Hopkins
maintains the literal correctness of the Mosaic account of the creation,
and attempts to show that all the facts discovered by geologists may
have occurred in the ages included in the Mosaic chronology.
That the mysterious power of terrestrial magnetism can perform all that
he claims for it, we can perhaps admit. But how does this explain the
succession of Silurian, Old Red Sandstone, Carboniferous and other
strata, up to the Tertiary deposits, with their fossils, each differing
in character from those of the preceding series? That these were
successive creations admits of no doubt, and while it is undeniable that
the fiat of the Creator could readily produce all these phenomena, it
may reasonably be asked if it is probable that all these myriads of
organic beings, whose remains serve as records of their existence, were
created only to be immediately destroyed.
Again, does not the author of the “Principles of Terrestrial Physics”
prove too much? He admits that 3,000 years ago the climate of England
was tropical: he does not deny that a subsequent period of intense cold
intervened, 2,550 years ago. He admits historical records, and 2,350
years ago Pythagoras constructed his cosmography of the world, which has
never been seriously impugned; and yet he has no suspicion that
countries so near to his own had changed their climates first from
tropical to glacial, and back again to a temperate zone. It is not
reasonable to believe this parable.
The school of philosophy generally considered to be the most advanced in
modern science has yet another view of cosmogony, of which we venture to
give a brief outline. Space is infinite, says the exponent of this
system,[9] for wherever in imagination we erect a boundary, we are
compelled to think of space as existing beyond it. The starry heavens
proclaim that it is not entirely void; but the question remains, are the
vast regions which surround the stars, and across which light is
propagated, absolutely empty? No. Modern science, while it rejects the
notion of the luminiferous particles of the old philosophy, has cogent
proofs of the existence of a luminiferous ether with definite mechanical
properties. It is infinitely more attenuated, but more solid than gas.
It resembles jelly rather than air, and if not co-extensive with space,
it extends as far as the most distant star the telescope reveals to us;
it is the vehicle of their light in fact; it takes up their molecular
tremors and conveys them with inconceivable rapidity to our organs of
vision. The splendour of the firmament at night is due to this
vibration. If this ether has a boundary, masses of ponderable matter may
exist beyond it, but they could emit no light. Dark suns may burn there,
metals may be heated to fusion in invisible furnaces, planets may be
molten amid intense darkness; for the loss of heat being simply the
abstraction of molecular motion by the ether, where this medium is
absent no cooling could take place.
[9] Professor Tyndall in _Fortnightly Review_.
This, however, does not concern us; as far as our knowledge of space
extends, we are to conceive of it as the holder of this luminiferous
ether, through which the fixed stars are interspersed at enormous
distances apart. Associated with our planet we have a group of dark
planetary masses revolving at various distances around it, each rotating
on its axis; and, connected with them, their moons. Was space furnished
at once, by the fiat of Omnipotence, with these burning orbs? The man of
science should give no answer to this question: but he has better
materials to guide him than anybody else, and can clearly show that the
present state of things _may_ be derivative. He can perhaps assign
reasons which render it probable that it _is derivative_. The law of
gravitation enunciated by Newton is, that every particle of matter in
the universe attracts every other particle with a force which diminishes
as the square of the distance increases. Under this law a stone falls to
the ground, and heat is produced by the shock; meteors plunge into the
atmosphere and become incandescent; showers of such doubtless fall
incessantly upon the sun, and were it stopped in its orbit, the earth
would rush towards the sun, developing heat in the collision (according
to the calculations of MM. Joule, Mayer, Helmholtz, and Thomson), equal
to the combustion of five thousand worlds of solid coal. In the
attraction of gravity, therefore, acting upon this luminous matter, we
have a source of heat more powerful than could be derived from any
terrestrial combustion.
To the above conception of space we must add that of its being in a
continual state of tremor. The sources of vibration are the ponderable
masses of the universe. Our own planet is an aggregate of solids,
liquids, and gases. On closer examination, these are found to be
composed of still more elementary parts: the water of our rivers is
formed by the union, in definite proportions, of two gases, oxygen and
hydrogen. So, likewise, our chalk hills are formed by a combination of
carbon, oxygen, and calcium; elements which in definite proportions form
chalk. The flint found within that chalk is compounded of oxygen and
silicon, and our ordinary clay is for the most part formed by a union
of silicon, oxygen, and aluminum. By far the greater part of the earthy
crust is thus compounded of a few elementary substances.
Such is Professor Tyndall’s view of the universe, rising incidentally
out of his theory of heat, his main object being to elucidate his theory
of heat and light.