and that the atoms of this gas or vapour exerted (as they must have
done) an attraction towards each other, the result would be that they
would press immensely upon those parts towards the centre and cause
them to solidify. This act of solidification would produce such an
intense heat that the solid would be expanded and fused into a liquid,
this continuing until all the more condensible matters had become
liquid, the earth would assume its spheroidal form from its rotation,
be surrounded by an atmosphere of the least easily condensible
substance, nitrogen, together with all the oxygen not wanted to
combine with the metallic vapour and form earth. This globe with its
atmosphere continuing to roll through the cold regions of space, would
gradually lose the heat from its outer part by radiation. A film of
cooled and condensed earthy matter would begin to form on the surface
by crystallisation, and then would commence all those grand phenomena
which it is the province of the geologist to study and explain. This
crust consisted of the first-formed granite which (from inequality of
contraction in the bulk of the earth) was broken up into fragments
and perhaps partly re-dissolved again and again in some places, as it
chanced that these contractions were more or less irregular. The result
of this crushing and crumbling-up is seen in the coarser parts of the
gneiss, called "Grauwacke," which consist of angular fragments of
granite more or less imbedded in a cement of the same substance. This
could not have been produced by water, as the surface must have been
too hot for it to have existed on the earth in any other form than the
most highly rarefied steam combined with the atmosphere, and in all
probability partly condensed in the upper regions, forming a continuous
strata of clouds, or rather water, through which the sun could hardly
be seen or its light penetrate, and such a state of things exists at
this present time in the planet Jupiter. How beautifully does this
coincide with the Mosaic account, "The earth was without form and void,
and darkness was upon the face of the earth."
The surface of the earth at this time can be well understood by any
one who will take the pains to evaporate any saline solution in a
capsule till it is about to crystallise, and observe attentively the
pellicle of salt as it forms on the surface; first a partial film will
show itself in a few places, floating about and joining with others,
then when nearly the whole surface is coated, it will break up in some
places and sink into the liquid beneath, another pellicle will form and
join with the remains of the first, and as this thickens it will push
up ridges and inequalities of the surface from openings and fissures
in which little jets of steam and fluid will escape; these little
ridges are chains of mountains, the little jets of steam those volcanic
eruptions which were at that period so frequent; the surface of the
capsule is the surface of the earth, and the five minutes which the
observer has contemplated it, a million years.
The next effect of the cooling of the earth would be the gradual
condensation of the vapour of water with which it was surrounded; this
falling upon the earth formed seas and oceans, leaving only the higher
portions exposed above its level. The clearing-up of the dense dark
clouds for the first time let in to the earth's surface the glorious
and vivifying rays of the sun, and this great effect possibly accords
with the earliest record in the Bible of the acts of creation--"And God
said, let there be light, and there was light."
[Illustration: FIG. 9--STALAGMITE.]
[Illustration: FIG. 10.--TEREBRATULA.]
The earth being chiefly covered with water, and the air partly freed
from watery vapour, then commenced the great creation of organised
beings. The air, although to a certain extent, free from vapour, must
yet have contained an enormous amount of carbonic acid; this, being
less easily condensed than any of the matters which had gone through
that process, would still remain there as a gas, and the effect of this
superabundance would be to saturate all the water covering the earth
with it; this solution of carbonic acid, being capable of dissolving
lime, would (as it percolated and rushed in currents through the rocks
and inequalities of the surface) become converted into a solution of
percarbonate of lime, taking up a large quantity of this earth from
the broken-up granite, &c., then this carbonate of lime would be
deposited at the bottom of the water in one of two ways--either from
pressure, diminution of carbonic acid in the air, and heat of the
surface, it crystallised at the bottom in the form of marble (that
the water does thus become saturated with carbonic acid and take up
lime, is constantly shown by the stalagmites which form on the floors
of caverns, where the water thus loaded with percarbonate of lime,
evaporating, deposits gradually the carbonate in all sorts of fantastic
shapes, as in fig. 9), or the myriads of crinoidians and brachiopodous
molluscs (fig. 10) which were about this time created, absorbed it into
their systems and at their death deposited their shells, which are made
of this earth, at the bottom of the sea; these shells, accumulating
through ages into strata, became hardened and partly crystallised by
heat, thus forming the limestones, which were the first containing
carbonate of lime. That such a collection, from such causes, is quite
possible, will be presently shown in describing the chalk formation.
Ages of comparative quiet now appear to have succeeded the first great
contraction of the earth's crust, probably millions of years, during
which time the tides and currents of the ocean had to wash and wear
down all the thousands of projecting rocks or inequalities and dissolve
(as before described) all the lime, depositing the sand and clay in
those immense strata which form the "transition series;" this appears
to have taken place over nearly the whole world at that time, and ages
upon ages must have elapsed to form such deposits as the sandstone,
claystone, and limestone, in alternation, forming the "Llandilo,"
"Caradoc," and "Wenlock" strata, more than a mile in thickness; these
are by some geologists reckoned among the primary series (by some
called the "transition rocks"), and in England form the "Cambrian" and
"Silurian" systems.
[Illustration: FIG. 11--TRILOBITE.]
In these strata the remains of organised beings are first found,
consisting of zoophytes, crustacea (chiefly Trilobites, fig. 11),
nautili, crinoidii (stone lilies), and a few ganoid (plate-covered)
fishes; these lower forms of animal life in some parts abound in the
most prodigious numbers. There must, of course, have been vegetables
of some kind previously formed to constitute nourishment for these
animals, but scarcely any remains of such exist, except in a few
localities.
The Trilobites were amongst the first creatures inhabiting our globe,
and it is a curious fact to contemplate, that their eyes (fig. 12)
should have been preserved perfect; they present one of those
wonderful objects which carry one's thoughts backwards to the early
ages of the world, probably many millions of years, and yet it is
found by the peculiar structure of the eyes of these Trilobites that
they were placed at the bottom of the sea with perfect power to look
upwards at the light of the sun through the transparent waters. The
same hand and the same power had then Divine care and solicitude for
the well-being of His creatures, as great as He has for those of later
ages, and these first-formed beings exactly correspond with the account
of the creation of animals given in the book of Genesis, "And God said,
let the waters bring forth abundantly the moving creature that hath
life."
[Illustration: FIG. 12.--EYE OF TRILOBITE.]
At the end of the "transition period"--after ages of long-continued
disintegration of the rough surface of the earth, and its deposition in
strata--after thousands of generations of crustaceans, molluscs, and
zoophytes had lived and died, depositing their shells at the bottom
of the seas, so as to form strata of the carbonate of lime--a great
and terrific convulsion of nature put a stop to all this quiet and
systematic order of things; for through these long reaches of time,
the physical laws of nature had continued to exert their influence,
the bulk of the world had gone on radiating its heat into space, and,
as a necessary result, had gradually contracted in size. Now, this
radiation had doubtless been much retarded by the badly-conducting
surface of solid matter which had everywhere covered it, but, although
retarded, it could not be prevented, and although the crust of solid
matter may already have been several miles in thickness, yet this in
relation to the bulk of the earth would hold but the proportion of the
paper on the surface of a twelve-inch globe. As the fluid mass of the
earth continued to contract, there would of course be a great stress
or crushing-power exerted on the crust, both by its own gravity and
that of the air which surrounded it, and about this period it appears
to have given way over the greatest portion of the globe, producing
enormous rents and fractures, seen in every country in the faults
and dislocations of these primitive and transition strata, some of
which were driven up by the downward force of others, and left in a
perpendicular position, some overlapping each other, &c.; but the
greatest effect of this convulsion appears to have been produced by
the rocking or rolling surface of the sub-existing fluid world,
forming gigantic waves, which, by meeting in opposite directions and
thrusting upwards the strata to a great height, formed the mighty
mountain-chains of the now-existing earth, which raise their lofty
pinnacles above the clouds. Now, these mountains may at first thought
appear too ponderous and extensive to be thrown up in this way; but by
inspecting the engraved section of a part of the globe (fig. 13), it
will be seen how very insignificant a mountain is when compared with
the whole world. This section is through Asia from the Persian Gulf to
the Yellow Sea, and embraces the highest land on the whole face of the
earth, and is drawn on a scale in which the earth is represented by
a globe sixteen inches diameter. The rugged and peaked tops of these
mountains would be formed by the great fractured masses of the broken
strata being thrust upwards and there resting against each other;
but who can describe the chasms and hollows which must have resulted
when the great wave of melted earth had subsided to its level under
one of these huge mountain masses? or the dreadful abyss into which
at some future time it and the surrounding country may fall, if they
have not already been filled up by the sinking of the surrounding
strata. Some of these great waves, when thrust upwards, forced their
way right through the point of the mountain and came pouring down in
torrents of liquid earth (lava), deluging the surrounding country and
filling up the beds of the adjacent seas, casting out cinders and ores
of metals--as iron, which appears to have first made its appearance
at that time, mingling with the deposits and tinging them of a red
colour. These great volcanoes, upon the subsidence of the rock-waves,
still (more or less) retained their communication with the interior
fiery earth, and are now the greatest safeguards against such a general
crushing-up of the strata, for they act as safety-valves against any
unequal expansion of the interior (fig. 14). The greatest eruptions of
volcanoes or the most terrific earthquakes of modern times, are as the
most insignificant trifles compared with what must have taken place to
form the inequalities of surface found to exist.
[Illustration:
FIG. 13--SECTION OF 40 DEG. OF THE EARTH'S SURFACE, BEING
THE SOUTHERN PART OF ASIA, AND INCLUDING THE HIGHEST LAND IN THE
WORLD.
The outer uneven line represents the mountains and table-lands from the
sea's level, and the lower line shows the depth to which the crust of
the earth's surface has been examined--about five miles.
A to B.--Level of sea.
B to second C.--Hindustan.
C to D.--Thibet.
D to E.--Great Desert of Gobi.
F.--500 miles of Earth's radius.
C to C.--The Himalayas, in which occurs the highest mountain in the
world, Dhawalagiri, which is 28,174 feet high.]
[Illustration: FIG. 14.--BURNING MOUNTAIN.]
But the contraction of the interior mass of the earth still continues,
and the cavities left by the expulsion of volcanic matters, and the
pushing-up of the mountains, may not all have been compensated for by
the sinking-in of the strata, so it remains a matter of doubt whether
the crust of the earth is sufficiently strong to bear the pressure of
its own and the air's gravity, or whether at some future day another
contraction will break it up and destroy the whole existing order
of things. The shocks of earthquakes are strictly analogous to such
catastrophes, but on an immensely inferior scale.
[Illustration: FIG. 15.--LIMESTONE MADE UP OF ENCRINITE.]
[Illustration: FIG. 16.--LIMESTONE MADE UP OF CORALS
(Favosites polymorpha).]
The effects of the last great contraction having subsided the surface
of the earth assumed a new arrangement of its matter, and the order of
things which caused the deposition of the secondary strata commenced.
Sedimentary sandstones were deposited from the washings of the
surface by the waters which had not yet absorbed all the superfluous
carbonic acid of the air, but continued to do so, and as fast as
it became absorbed and saturated with the calcareous matter of the
soil, swarms of coral-polypi, which were then formed, began to build
their habitations in the warm waters of the ocean and rob them of
the carbonate of lime which they contained, leaving them capable of
absorbing more from the atmosphere. These little creatures formed
immense masses of coral, and together with the "Encrinites" (having
stony frameworks, figs. 15 and 16), were the chief artificers of that
age, and well did they show what perseverance was able to accomplish,
for through the thousands of years of quiet which now succeeded,
they must have filled up nearly all the existing oceans with their
structures, causing the water gradually to flow from its former beds
into other situations, and thus from time to time was changed the
position of both sea and land. The strata of mountain limestone which
now exist are the remains of what these little polypi then produced,
for there is scarcely a portion of this kind of rock, but shows
evidences of having been, once, coral, madrapore, or some analogous
structure (fig. 17). This mountain limestone sometimes occurs thousands
of feet thick, and extends over vast districts both in Europe and
America.
[Illustration: FIG. 17.--ENCRINITIC LIMESTONE.]
During this period, although there were no great disturbances, capable
of displacing the strata, yet there appears to have been frequent
small eruptions of volcanic matter through the crevices of the lower
strata, filling up all their cracks and vacuities, and in many cases
rising to the surface, overflowing with basalt, toadstone, and other
volcanic formations; in other cases rising in enormous quantities
through openings at the bottom of the seas, partly filling these up,
driving off the waters, and thus covering many of the coral formations
with coatings of sand to a great thickness, raising up others into
considerable elevations, and forming hills and fresh tracts of earth.
[Illustration: FIG. 18.--FOSSIL TREE FERNS.]
During this long period of comparative quiet most of the irregularities
on the surface of the earth became worn down, and extensive swamps were
produced by partial evaporation of the inland lakes. These swamps were
subject to occasional inroads of the sea, and at times formed shallow
lakes or lagoons; in these grew the most luxuriant vegetation, gigantic
pines, tree-ferns (fig. 18), equisetacæ, &c. These plants, nurtured by
a hot and moist climate, acquired a great luxuriance of growth, and
must have formed forests of such great density, that there is nothing
existing at the present time worthy to be compared with them, even in
the hottest climates. Such fertility appears to have been dependent
upon the conditions of the air and earth, the former containing more
carbonic acid (the food of vegetables) and the latter a greater amount
of warmth, than at present; these two circumstances, so favourable to
the growth of plants, were equally unfavourable to the existence of
air-breathing animals, to whom the carbonic acid would be fatal poison.
Thus, in the mighty hands of God, the air was undergoing a gradual
purification, to fit it for the animals He intended to create; the
polypi were extracting from the water all the carbonate of lime it
was absorbing from the air and earth, and fixing it in the soil, to
be of use in a hundred ways at some future time, while the vegetation
growing in abundance extracted it from the air, and fixed its carbon
in their leaves and substance generally; these vegetables, decaying
and falling upon the surface of the earth, accumulated there for ages,
and formed a carbonaceous matter which was afterwards changed by time
and pressure into coal. The same thing (on a very much smaller scale)
is taking place in the tropical forests of the present age; there the
surface-soil is quite black, and consists of nothing but decayed leaves
and wood for several feet in depth, but in the present time there are
hosts of insects, every one of which feeds upon this vegetable matter,
preventing to a great extent its accumulation, while in the former age
there was nothing to destroy it when once deposited on the ground; so
that the carbon of these forests of the secondary period, existing
through perhaps tens of thousands of years, extracted from the air a
sufficient quantity of vegetable carbonaceous matter to produce thick
seams of coal, even when compressed by the superincumbent strata.
These forests were subject from time to time to inroads of the sea
produced by the before-mentioned causes, and thus it is found that
the seams of coal are often buried by several hundred feet of sand,
clay, shale, &c., above which the same growth recommenced to form a
second strata of coal, and ages must have elapsed whilst each of the
numerous seams which interstratify the "coal measures" were forming.
This coal, preserved in the depths of the earth, now forms the greatest
treasure of the mine, and ironstone (from which iron is procured)
would be almost useless but for the occurrence of these two minerals
together with limestone (used as a flux) in the same locality, and
it is this fortunate circumstance which enables England to produce
such vast quantities of iron at such a cheap rate. The quantity of
coal consumed in the iron-smelting works and for fuel generally, is
beyond what could have been imagined a generation or two back, being
somewhere about 50,000,000 tons annually, the coal brought to London
alone in 1856 being 1,271,800 tons, yet there is such a plentiful
supply of this valuable fuel in Great Britain alone that, supposing the
annual consumption to rise to 70,000,000, it would serve (according
to computation) a thousand years. Who shall say from whence fuel
will then be obtained? probably from some other source provided by
the foreknowledge of God, as was shown in the formation of the coal
itself; for who could have imagined, a thousand years ago, when England
possessed such immense forests, and wood was the universal fuel, that
this very wood would become too scarce and valuable to be used, and
that a substitute would be dug out of the earth!
The coal-shales (thin layers of claystone found in the coal seams)
furnish beautiful specimens of ferns and other plants turned into coal
(fig. 19), or leaving their perfect impressions in the clay. The coal
formation occurred during the latter part of one of those long eras of
tranquillity which supervened upon the contraction and breaking-up of
the older strata; but the laws of nature are immutable, and these days
of comparative quiet again came to a close. The same phenomena before
described again occurred, and there is hardly a square mile of these
strata but shows evidences of the terrible convulsion which desolated
the earth. Some of the strata were raised, others depressed, and some
lost altogether, the cracks and flaws being filled with liquid lava or
basalt, which in many cases rose upwards through them and overflowed
the surface. Many of the cracks of this, the "carboniferous system,"
are filled with sulphuret of lead called "galena," the ore from which
all the lead of commerce is obtained; it is not well known how the
veins of this and similar substances got into these crevices, but it is
probable they were injected in a fluid state by some unequal pressure
on the liquid beneath, or deposited by electrical action.
[Illustration: FIG. 19.--FERN (Pecopteris ligata) FROM UPPER SHALE,
SCARBOROUGH.]
The great world of vegetation was thus destroyed, giving place to
new forms of animal and vegetable life. The temperature, all this
while sinking, had reached a degree somewhat resembling the hottest
regions of the earth at the present day. The waters had changed their
localities, new mountains and new continents had made their appearance,
and again did the ever-active waters begin to demolish and wear down
the asperities of the surface and deposit the results upon the strata
below in the form of the new red sandstone and magnesian limestone,
the former containing iron in great abundance, and the latter magnesia
(an earth not met with before), both of which substances were probably
ejected as volcanic products and afterwards combined with the carbonic
acid of the air.
[Illustration: FIG. 20.--LABYRINTHODON.]
[Illustration: FIG. 21.--IMPRESSIONS OF FEET IN NEW RED SANDSTONE.]
During the formation of these strata there appears to have been both
birds and quadrupeds of many kinds, together with a reptile much
resembling a frog, but of great size, being five or six feet long,
called the "Labyrinthodon" (fig. 20). The oxide of iron, or some other
agent appears to have prevented the fossilisation of the inhabitants of
these strata, for but few of their organic remains have been preserved;
but very curious evidences of their existence nevertheless remain,
in the impressions of their feet upon the ground they trod (fig. 21),
which appears to have been a moist clay or mud peculiarly adapted to
receive impressions, and which having been in many places covered over
with a stratum of fine sand, and then abandoned by the sea, the whole
have hardened into stone, and being now separated, the one contains
their footprints and the other perfect casts of them! Nor are these
foot-marks all that these sandstones have to tell us of their day;
for the ripples of the waves, and even the little pits made by drops
of rain as they fell, are in this most marvellous manner preserved,
forming objects of wonder and admiration for us mortals to contemplate,
and themes whereon the devout mind may pour out its tribute of praise
to their Great Author. How evident it is that the Creator designed
beforehand that we should search for these hidden evidences of His
handiwork, or for what purpose were they thus stored up and preserved?
"Seek, and ye shall find, knock, and it shall be opened unto you," are
the words of God, and they apply as fully to the material wonders of
His works as to the mysteries of His revealed Word.
As the strata below the new sandstone formation was called the
"Carboniferous" system, from its containing much carbon in the
form both of coal and carbonic acid, so this has been called the
"Saliferous" system, from the occurrence in many places of strata of
"rock-salt" or crystallised chloride of sodium, and (where the rain
finds its way down and dissolves it) of brine springs; these (in
England) exist chiefly in Cheshire and Warwickshire, but in Poland and
Hungary they exist on a much larger scale, the rock-salt being nearly
a thousand feet thick. It has been said that these strata of salt were
formed by the evaporation of salt lakes, but it is much more probable
that salt is one of the natural materials of the earth, and that both
salt lakes and oceans have become salt from dissolving out these strata
wherever they have come into contact. The next sediment deposited
over the new red sandstone is called the "Lias," a sort of limestone
mixed with clay of a blueish-grey colour, and upon this has is again
deposited the various strata known as the "Oolite" (Roe-stone) system,
from its appearance resembling the roe of a fish, it consists of small
rounded particles of limestone set in a cement of the same substance
worn down fine.
[Illustration: FIG. 22.--AMMONITE (Henlyi).]
[Illustration: FIG. 23.--PENTACRINITE.]
These strata furnish a great many organic remains, especially the
shells of the conchiferous mollusca and cephalopods, as Ammonites (fig.
22), Belemnites, Nautili, and Pentacrinites (fig. 23), of which a great
many varieties are found, also the remains of gigantic reptiles, as the
Ichthyosaurus (fig. 24), Plesiosaurus (fig. 25), and others. New forms
of animal existence seem to have been created in this period in great
abundance, and the waters of the earth once again became the theatre of
deposition for the shells and polypidomes of zoophytes and molluscs,
which swarmed them in myriads, and another great group of rocks began
to be formed, namely, the chalk or "Cretaceous" system, which form the
cliffs and downs of our south coasts, and strata of great extent in
nearly every part of the world; it differs from limestone only in not
being so hard, which is supposed to arise from its not having undergone
the changes caused by heat and pressure.