Part 6

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.

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.

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.

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.

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.

The chalk is interstratifìed with lines of sand, and the lower part is almost entirely sandy, forming the gault and greensand deposits; these each contain organic remains, and must have been the original sand of the sea-bottom before the chalk was deposited on it. These seas must have been the residence of a vast number of reptiles, for the gault contains an enormous number of nodules of what appears to be stone, but which upon closer examination, prove to be coprolites, or portions of the excrement of those creatures partly fossilised, but still retaining phosphate of lime enough to render them valuable manure, and these--like the coal--after being buried in the earth for thousands of years, are now being brought into use. In these coprolites may be constantly seen the teeth and bones of fishes, together with portions of echini and crustaceans, which had passed through the intestines of these saurian reptiles. Fig. 26 is the shell of a small nautilus (_Nautilus inequalis_) thus found.

This chalk is of a white colour, very light and porous; under the higher powers of the microscope, it appears to be made up of organic forms, as "Foraminifera," and portions of various kinds of shells, crushed and broken into minute fragments (fig. 27). Dr. Carpenter, in his work on the microscope, says: "Many parts of it (the chalk) consist in a great measure of the minuter parts of the smaller kinds of Foraminifera, whose shells are imbedded in a mass of apparently amorphous particles, many of which nevertheless present indications of being the worn fragments of similar shells, or of larger calcareous organisms. In the chalk of some localities, Foraminifera constitute the principal part of the minute organisms which can be recognised with the microscope; in other instances the disintegrated prisms of Pinnæ, or other large shells of the like structure (as Inoceramus), constitute the great bulk." The fossil remains in the chalk are very numerous and are all of a marine character, the ammonites (fig. 28), belemnites, and other cephalopods, were very prevalent, as were the various Echinodermata, as the _Hemicidarus intermedia_ (fig. 29), together with numerous univalve and bivalve mollusca, various crustacea, fish and reptiles. There was some considerable wonderment a few years ago expressed at the skeletons of men being found in the chalk at Guadaloupe; but it has been ascertained that this chalk is a modern formation, being produced by the sea washing and disintegrating the adjacent coral reefs, and depositing a fine white sediment of broken coral on the shore which can hardly be distinguished from ancient chalk; the same process is taking place at the Bermudas and other islands of the West Indies.

In many places the chalk strata contain single lines of flints, running for miles parallel to the layers of chalk; these flints consist of almost pure silica, and it has been, matter of wonder how they got there, but on considering how slowly the deposition of chalk must have taken place, from the formation and death of millions of minute creatures, and that it was once the bottom of a deep sea, the disposition of the flints in lines would be accounted for, supposing them to have been formed on that sea-bottom, and the source from which they have been derived is doubtless the petrifaction of sponges, madrapores, &c., there formed. Dr. Carpenter (in the work before referred to) says: "It may be stated, as a fact beyond all question, that nodular flint and other analogous concretions (such as agates) may generally be considered as fossilised sponges or alcyonian zoophytes, since not only are their external forms and their superficial markings often highly characteristic of those organisms, but when sections of them are made sufficiently thin to be transparent, a spongy texture may be most distinctly recognised in their interior."

During the deposition of these secondary strata in the hollows of the surface, but little alteration of the relative situations of sea and land could have taken place, as the deposits for the most part lie conformably to the same hollows or "basins" (fig. 30 will illustrate this); but after the deposition of these strata, there appears to have been a very great disturbance, many chains of mountains were cast up (as the Apennines), carrying upwards with them these deposits; some of the strata were so displaced that they were left in a perpendicular position, as may be seen in several places at the south side of the Isle of Wight. These disturbances, however, did not amount to so general a convulsion as those before described, nor is it known whether all the effects produced on these strata took place at or near the same period of time; they nevertheless appear to have produced an almost total change in the situation of the land and sea, for the "downs" of chalk (on the southern coast of England, for example) were, before these changes, the beds of seas. This is the last of the great convulsions which the earth has undergone, for the tertiary strata which afterwards began to be deposited rest in the hollows or basins (chiefly in the chalk) then left; the alterations in and since these deposits appear to consist chiefly of the upheaval of certain localities, the depression of others, the evaporation of inland lakes, and the wear and tear of the land from these causes, which are still in continuous action (as from the washing down of cliffs by the sea, and the formation of mud deposits at the mouths of rivers), or the volcanic agencies which in some places (as in Ireland) have cast up basalt over the chalk.

The tertiary strata contain remains of most of the classes of animals now in existence, but yet differing greatly in species, and as the strata approach the surface those species become more and more general; the plants also approach more nearly to those of the present time, but still most parts of Europe possessed a climate almost tropical. The tertiary strata consist chiefly of marine and fresh water deposits in the form of sands and clays, as the "London clay," which extends under London, resting upon a basin of chalk. The last deposits, forming the superficial layer of earth, and the formation last deposited before the creation of man, are called the Diluvium and Alluvium, and contain numerous remains of mammalia, birds, reptiles, and fishes. One of the most extraordinary animals of this period was the Dinotherium, a sort of walrus, which is supposed to have been the largest of quadrupeds, if indeed it was one (fig. 31). The quadrupeds of this, the "Pliocene" formation, are thus described by Professor Owen in his "History of British Fossil Mammals."

"At the period indicated by these superficial stratified and unstratified deposits the Mastodon had probably disappeared from England, but gigantic elephants (fig. 32), nearly twice the bulk of the largest individuals that now exist in Ceylon and Africa, roamed here in herds, if one may judge from the abundance of their remains. Two horned rhinoceros, of at least two species, forced their way through the ancient forests or wallowed in the swamps. The lakes and rivers were tenanted by hippopotami, as bulky and with as formidable tusks as those of Africa. Three kinds of wild oxen, two of which were of colossal size and strength, and one of them maned and villous like the bonassus, found subsistence on the plains. Deer as gigantic, in proportion to existing species, were the contemporaries of the old _Uri_ and _Bisontes_, and may have disputed with them the pasturage of that ancient land. One of these extinct deer is well known as the Irish elk, by the enormous expanse of its broad-palmed antlers (fig. 33). Another herd proves more like those of the wapiti, but surpassed that great Canadian deer in bulk. A third extinct species more resembled the Indian _Hippelaphus_, and with these were associated the red-deer, the rein-deer, the roebuck, and the goat. A wild horse, a wild ass or quagga, and the wild boar, entered also into the series of British pliocene hoofed animals. The carnivora, organised to enjoy a life of rapine at the expense of the vegetable feeders, to restrain their undue increase and abridge the pangs of the maimed and sickly, were duly adjusted in size and ferocity to the fell task assigned them in the organic economy of the pre-adamite world. Besides a British tiger, of larger size and with proportionately longer paws than that of Bengal, there existed a stronger feline animal (Machairodus) of equal size, which from the great length and sharpness of its sabre-shaped canines, was probably the most ferocious and destructive of its peculiarly carnivorous family. Of the smaller felines, we recognise the remains of a leopard, a large lynx, and of a wild cat. Troops of hyenas, larger than the Crocuta of South Africa, which they most resembled, craunched the bones of the carcases relinquished by the nobler beasts of prey, and doubtless often themselves waged the war of destruction on the feebler quadrupeds.

"A savage bear, surpassing the _Ursus ferox_ of the Rocky Mountains, found its hiding-place, like the hyæna, in many of the existing limestone caverns of England. With the _Ursus spoelus_ was associated another bear, more like the common European species, but larger than the present individuals of the _Ursus Arctas_. Wolves and foxes, the badger, the otter, the foumart, and the stoat, complete the category of known pliocene carnivora of Britain."

In the time of these the last of the tertiary strata, there appear evidences of a degree of cold much greater than at present exists; this seems to be pretty well proved by the "boulder formation," or prevalence of erratic blocks of stone, the progress of which have been traced from their sources of origin to hundreds of miles distant, and there is no conceivable power which could have carried them but the floating fields of ice or glaciers; both of these sources are capable of this removal, for it is not uncommon to find large pieces of rock and layers of gravel floating on masses of ice. Glaciers are formed by the snow on the sides of mountains becoming hardened by being partially melted and again frozen, and at every melting the fluid tends to descend, when it again becomes frozen, always adding to the lower part and carrying away from the upper. In this way whole glaciers of many miles extent become unfixed, and as fresh snows are added to their upper parts, they descend slowly, entangling with them and tearing away the rocks in their vicinity. When they arrive at the sea and float forth, these rocks are borne with them.

But there are as yet no traces of man, not one small fragment of his skeleton, not one minute relic of his constructive powers, although the bones of man are as capable of preservation as those of any other animal, being the same in structure and composition; the remains of hundreds of fragile insects, seeds, leaves, and all sorts of organic structures, are found perfectly preserved (fig. 34). The only way, therefore, of accounting for the absence of any organic remains of man, is the assumption that he was not then created; and this is confirmed by the fact that in the very uppermost layers of the earth's surface his bones and the works of his hands are found in great abundance; it is therefore with good reason that we come to the conclusion, that he was the last creature formed by his Maker. That the creation of man was pre-intended by God, seems also almost proved by the numerous objects before created, capable of ministering to his use and happiness--capable of exercising his constructive and inquiring capabilities--suitable to his imagination and tastes, and his only, and which would serve no purpose of utility to the mere brutes. Of what use, to any creature but man, is coal--of what use the metals? Of what avail is it to any of the lower animals, that God has caused glass and other transparent substances to have the power of refracting the rays of light? but without which not one-half of our knowledge of His wondrous works would ever have been obtained, for it is upon this property alone that the powers of the telescope and microscope depend. Of what use to any but man are fire, artificial light, and galvanism? and yet all these were created long before man was.