CHAPTER XI.FOSSIL REMAINS—THE EXPLORATION.

Fig. 12.—Fossil Irish Deer (County Fermanagh). In the Museum of Trinity College, Dublin. From Haughton’s Manual of Geology

These Fossil Remains do not always occur in the same state of preservation. Sometimes we have the bone, or plant, or shell, in its natural condition; still retaining not only its own peculiar form and structure, but likewise the very same organic substance of which it was originally composed. Examples innumerable may be seen in the British Museum, or, indeed, in almost any Geological collection: the fine skeletons of ancient Irish Deer, whichare exhibited in the Museum of Trinity College, Dublin, and of which all the bones are in excellent preservation, must be familiar to many of our readers.

It happens, however, more frequently that the organic substance itself has disappeared, but has left an impression on the rock, that now bears witness to its former presence. Thus, for instance, when a shell has been dissolved and carried away by water percolating the rock, it has very often left after it, on the hard stone, a mould of its outer surface and a cast of its inner surface, with a cavity between corresponding to the thickness of the shell. In such cases we have the form, the size, and the superficial markings of the organic body, but we have no part of its original substance, and no traces of its internal structure. This form of fossilization, as Sir Charles Lyell has well put it, “may be easily understood if we examine the mud recently thrown out from a pond or canal in which there are shells. If the mud be argillaceous, it acquires consistency in drying, and on breaking open a portion of it, we find that each shell has left impressions of its external form. If we then remove the shell itself, we find within a solid nucleus of clay, having the form of the interior of the shell.”70In many cases the space first occupied by the shell is not left empty when the shell has been removed, but is filled up with some mineral substance, such as lime or flint. The mineral thus introduced becomes the exact counterpart of the organic body which has disappeared; and has been justly compared to a bronze statue, which exhibits the exterior form and lineaments, but not the internal organization nor the substance of the object it represents.

There is a third form more wonderful still, in which Fossil Remains are not uncommonly found. The original body has passed away as in the former case, and yet not only does itsoutward shaperemain, but even itsinternaltextureis perfectly preserved in the solid stone which has taken its place. This kind of change is exhibited most remarkably in the vegetable kingdom. Fossil trees of great size have been discovered of whichthe whole substance has been changed from wood to stone: yet with such exquisite skill has the change been effected that the minute cells and fibres, and the rings of annual growth, may still be clearly traced; nay, even those delicate spiral vessels which, from their extreme minuteness, can be discerned only by the aid of the microscope. Thus the tree remains complete in all its parts; but it is no longer a tree of wood; it is, so to speak, a tree of stone.

The mystery of this extraordinary transformation has not yet been fully cleared up by scientific men; but the general principle, at least, is sufficiently understood. It is thus briefly explained by Sir Charles Lyell: “If an organic substance is exposed in the open air to the action of the sun and rain, it will in time putrefy, or be dissolved into its component elements, consisting usually of oxygen, hydrogen, nitrogen, and carbon. These will readily be absorbed by the atmosphere or be washed away by rain, so that all vestiges of the dead animal or plant disappear. But if the same substances be submerged in water, they decompose more gradually; and if buried in the earth, still more slowly, as in the familiar example of wooden piles or other buried timber. Now, if as fast as each particle is set free by putrefaction in a fluid or gaseous state, a particle equally minute of carbonate of lime, flint, or other mineral is at hand and ready to be precipitated, we may imagine this inorganic matter to take the place just before left unoccupied by the organic molecule. In this manner a cast of the interior of certain vessels may first be taken, and afterward the more solid walls of the same may decay and suffer a like transmutation.”71This exposition, so simpleand luminous in itself, may, perhaps, be rendered still more intelligible to the general reader by an ingenious illustration of Mr. Jukes. “It is,” he says, “as if a house were gradually rebuilt, brick by brick, or stone by stone, a brick or a stone of a different kind having been substituted for each of the former ones, the shape and size of the house, the forms and arrangements of its rooms, passages, and closets, and even the number and shape of the bricks and stones, remaining unaltered.”72

This singular kind of petrifaction, by which not only the external form, but even the organic tissue itself, is converted into stone, has been illustrated, in a very interesting way, by Professor Göppert of Breslau. With a view to imitate as nearly as he could the process of Nature, “he steeped a variety of animal and vegetable substances in waters, some holding siliceous, others calcareous, others metallic matter in solution. He found that in the period of a few weeks, or even days, the organic bodies thus immersed were mineralized to a certain extent. Thus, for example, thin vertical slices of deal, taken from the Scotch fir, were immersed in a moderately strong solution of sulphate of iron. When they had been thoroughly soaked in the liquid for several days, they were dried and exposed to a red heat until the vegetable matter was burnt up and nothing remained but an oxide of iron, which was found to have taken the form of the deal so exactly that casts even of the dotted vessels peculiar to this family of plants were distinctly visible under the microscope.”73

If we have succeeded in making ourselves understood, the reader will now have a pretty accurate notion of whatis meant, in modern Geology, by Fossil Remains. They are the remains or impressions of plants and animals, buried in the earth by natural causes, and preserved to our time in any one of the three forms we have just described. Either the body itself remains, still retaining its own natural substance, together with its external form and its internal structure. Or secondly, the organic substance and the organic structure have both disappeared, but the outward form and the superficial markings have been left impressed on the solid rock. Or thirdly, the substance of the body has been converted into stone, but with such a delicate art, that it is in all respects, outwardly and inwardly, still the same body, with a new substance. We should observe, however, that these three different forms of fossilization, which we have successively described, are not always clearly distinct in actual fossil specimens, but are often curiously blended together according as the original organic substance has been more or less completely displaced, or the process of petrifaction has been more or less perfectly accomplished.

It will probably have occurred to the intelligent reader that we have already had some insight into the Fossil world, when investigating the origin of Organic Rocks. We have seen, for instance, that Coal is the representative to our age of swamps and forests which once covered the earth with vegetation; that Mountain Limestone is in great part formed from the skeletons of reef-building corals; that the White Chalk of Europe is almost entirely derived from the remains of marine shells. But it should be observed that these and such like rocks, while they afford us much valuable information about the ancient organic condition of our planet, are not, strictly speaking, Fossil Remains. For, not only does the substance of the organic bodies they represent exhibit an altered character, but the internal structure has been in great part effaced, and even the outward forms and superficial markings have disappeared. They contain, it is true,great multitudes of Fossils. In the Coal, for example, are found, as we have seen, trunks of trees, together with the impressions of plants and leaves: in the Chalk and Mountain Limestone, fragments of shells and corals are often discovered in a state of perfect preservation. But the bulk of these formations is made up not so much of Fossil Remains, as of that into which Fossil Remains have been converted. Coal, for instance, is something more than Fossil wood; Chalk, and Limestone, and Marble, are something more than Fossil shells and corals.

Fossil Remains properly so called present a very much more lively picture of the ancient inhabitants of our Globe. But it is a picture that can but faintly be conveyed to the mind by the way of mere verbal description. He who would appreciate aright the reality and the significance of Fossil Remains must gather his impressions from actual observation. Let him go, for instance, to the British Museum, and walk slowly through the long suite of noble galleries which are there exclusively devoted to this branch of science. He will feel as if transported into another world, the reality of which he could scarcely have believed if he had not seen it with his own eyes. Before him, and behind him, and on each side of him, as he moves along, are spread out in long array forms of beasts, and birds, and fish, and amphibious animals, such as he has never seen before, nor dreamt of in his wildest dreams. Yet much as he may wonder at these strange figures, he never for a moment doubts that they were once indued with life, and moved over the surface of the earth, or disported in the waters of the deep. Nay more, though the forms are new to him, he will be at no loss, however inexperienced in Natural History, to find many analogies between the creation in the midst of which he stands, and the creation with which he has been hitherto familiar. There are quadrupeds, and bipeds, and reptiles. Some of the animals were manifestly designed to walk ondry land, some to swim in the sea, and some to fly in the air. Some are armed with claws like the lion or the tiger, others have the paddles of a turtle, and others again have the fins of a fish. Here is an enormous beast that might almost pass for an elephant, though an experienced eye will not fail to detect an important difference; and there is an amphibious monster that suggests the idea of a crocodile; and again a little further on is an unsightly creature which unites the general characteristics of the diminutive sloth with the colossal proportions of the largest rhinoceros.

If left to mere conjecture, the visitor would perhaps suppose that these uncouth monsters had been brought together by some adventurous traveller from the remote regions of the world. But no: he will find on inquiry that the vast majority belong to species which for centuries have not been known to flourish on the Earth; and that many of the strangest forms before him have been dug up almost from beneath the very soil on which he stands,—from the quarries of Surrey, of Sussex, and of Kent, and from the deep cuttings on the many lines of railway that diverge from the great metropolis of London. The life they represent so vividly is, indeed, widely different from that which flourishes around us; but it is the life not so much of a far distant country as of a far distant age.

It must not be supposed, however, that such skeletons as those which first arrest the eye in the galleries of the British Museum—so colossal in their proportions and so complete in all their details—fairly exhibit the general character of Fossil Remains. Perfect skeletons of gigantic animals are rarely to be found. They are the exception and not the general rule,—the magnificent reward of long and toilsome exploration, or, it may be, the chance discovery that brings wealth to the humble home of some rustic laborer. Very different are the common every day discoveries of the working Geologist. Disjointed bones andskulls, scattered teeth, fragments of shells, the eggs of birds, the impressions of leaves,—these are the ordinary relics that Nature has stored up for our instruction in the various strata of the Earth’s Crust: and these likewise constitute by far the greater part of the treasures which are gathered together in our Geological Museums.

We will suppose, then, that the visitor has gratified his sense of wonder in gazing at the larger and more striking forms, few in number, that rise up prominently before him, and seem to stare at him in return from their hollow sockets: he must next turn his attention to the cases that stand against the walls, and to the cabinets that stretch along the galleries in distant perspective. Let him survey that multitude of bones of every shape and size, and those countless legions of shells, and then try to realize to his mind what a profusion and variety of animal life are here represented. And yet he must remember that this is but a single collection. There are thousands of others, public and private, scattered over England, France, Germany, Italy, and beyond the Atlantic, on the continent of America, and even in Australia; all of which have been furnished from a few isolated spots,—scarcely more than specks on the surface of the Globe,—where the interior of the Earth’s Crust has chanced to be laid open to the explorations of the Geologist.

Lastly, before he leaves this splendid gallery, let him take a passing glance at the Organic Remains of the vegetable world. There is no mistaking the forms here presented to his view. He will recognize at once the massive and lofty trunks of forest trees with their spreading branches; the tender foliage of the lesser plants; and, in particular, the graceful fern, which cannot fail to attract his eye by its unrivalled luxuriance. But if the forms are familiar, how strange is the substance, of this ancient vegetation! The forest tree has been turned into sandstone; many of the plants are of the hardest flint; and the rich green ofthe fern has given place to the jet black color of coal. Let him take a magnifying glass and scrutinize the internal structure of these mineralized remains; for the more closely they are examined the more wonderful do they appear. He can observe without difficulty their minute cells and fibres, the exact counterpart of those which may be seen in the plants that are now growing upon the earth; he may detect the little seed-vessels on the under surface of the coaly fern; nay, if he gets a polished transverse section of the sandstone tree, he may count the rings that mark its annual growth, and tell the age it attained in its primeval forest.

Fig. 13.—Fossil Wood, from the Carboniferous Limestone of Mayo, showing the rings of Annual Growth.

From the museum to the quarry—Fossil fish in the limestone rocks of Monte Bolca—In the quarries of Aix—In the chalk of Sussex—The ichthyosaurus or fish-like lizard—Gigantic dimensions of this ancient monster—Its predatory habits—The plesiosaurus—The megatherium or great wild beast—History of its discovery—The mylodon—Profusion of fossil shells—Petrified trees erect in the limestone rock of Portland—Fossil plants of the coal measures—The sigillaria—The fern—The calamite—The lepidodendron—Coal mine of Treuil—Fossil remains afford undeniable evidence of former animal and vegetable life—Their existence cannot be accounted for by the plastic power of nature—Nor can it reasonably be ascribed to a special act of creation.

Fromthe galleries of the Museum we must now descend into the subterranean recesses of the mine and the quarry. For it is not enough to be familiar with the appearance of Fossil Remains, as they are laid out for show by human hands: we must see them also as they lie embedded in the successive strata of the Earth’s Crust, which are the shelves of Nature’s cabinet. We shall begin with the celebrated quarries of Monte Bolca, in Northern Italy, not far from Verona. Here, in the hard limestone rock, fifty miles from the nearest sea, entire skeletons of many different species of fish are foundembedded in profuse abundance, and in a wonderful state of preservation. They lie parallel to the layers of the rock; and, though flattened by pressure, still retain their scales, bones, fins, nay, even their muscular tissue, undisturbedand unharmed. Their color is a deep brown, which forms a remarkable contrast with the creamy hue of the limestone in which they are enveloped. The quarries have been worked only by students of Natural History for the sake of Organic remains, and are, therefore, of very limited extent; yet so abundant are these fossil treasures that upward of a hundred different species have been discovered, and thousands of specimens have been dispersedover the cabinets of Europe. So closely are they sometimes packed together that many individuals are contained in a single block.

Fig. 14.—Platax Papilio.From the limestone of Monte Bolca.

Fig. 15.—Semiophorus Velicans.From the limestone of Monte Bolca.

From these facts Geologists have been led to conclude:—that the strata in question were deposited on the bed of an ancient sea in which these fishes swam; that the waters of the sea were suddenly rendered noxious, probably by the eruption of volcanic matter; that the fishes in consequence perished in large numbers, and were then almost immediately embedded in the calcareous deposits of which the strata are composed. These views receive no small confirmation from a very remarkable phenomenon to which we may be allowed, in passing, to call attention. In the year 1831 a volcanic island was suddenly thrown up in the Mediterranean between Sicily and the African coast; and the waters of the sea were at the same time observed to be charged with a red mud over a very wide area, while hundreds of dead fish were seen floating on the surface. Is it not pretty plain that when the mud subsided many of the fish were enveloped in the deposit, and thus preserved to future times? If so, then, we should have an exact modern parallel to the fossil fishes of Monte Bolca. But for the present it is our purpose rather to describe facts than to develop theories.74

Near the town of Aix, the ancient capital of Provence, in the south of France, is a group of strata, consisting chiefly of Conglomerate, Marl, Gypsum, and Limestone, which has earned for itself no small fame in the annals of Geology. Besides many curious relics of an extinct vegetation, these strata yield also an abundance of Fossil Insects, which emerge from the rocky bed in which they have slept for ages, with a surprising freshness and a life-like reality. But the quarries of Aix, like those of Monte Bolca, are chieflyfamous for their Fossil Fish. And in this case, too, as in the former, it would seem as if vast multitudes had suddenly perished together from some mysterious cause, and were then as suddenly entombed. They exhibit no mark of mechanical violence: and yet they are found, not unfrequently, crowded together as closely as they can fit, in every variety of position, on the same slab of limestone. A good example of such a block is represented in our woodcut.

Fig. 16.—Fossil Fish from Aix.

The White Chalk Rock of Sussex has been rendered classical to the students of Geology by the skilful and laborious researches of the late Doctor Mantell. Previous to his time the Fish of the Chalk were known only by their teeth and bones, which abounded in every quarry. But he succeeded in bringing to light many whole skeletons, and disengaging them without injury from their chalky envelopment. In many cases these Fossil Fish appear to have suffered little from compression: the body still retains its rounded form; and even the most delicate scales and fins are as little disturbed or distorted as if the original had been surroundedby soft Plaster of Paris while floating in the water. For many years Doctor Mantell devoted himself, with indefatigable zeal, to the gathering of these interesting remains; and his magnificent collection now adorns the Galleries of the British Museum. In the annexed illustration is figured a specimen belonging to one of the most abundant species. It is closely allied to the common perch; and is popularly called Johnny Dory by the quarrymen of Sussex, but is entitled Beryx Lewesiensis by the learned.75

Fig. 17.—Beryx Lewesiensis, from the Chalk, near Lewes.

From Fossil Fish we now turn to Fossil Reptiles. Many of our readers have, perhaps, heard or read something about an important group of rocks known by the name of the Lias. This formation is well developed in England, and has received much attention from Geologists. It stretches in a belt of varying width from Whitby on the coast of Yorkshire to Lyme Regis on the coast of Dorsetshire; passing in its course through the counties of Leicester, Warwick, Gloucester, and Somerset. It is composed chiefly of Limestone, Marl, and Clay; and is celebrated forthe number and size of its great Fossil Reptiles. Of these the most remarkable is the Ichthyosaurus or Fish-like Lizard.

This monster of the ancient seas combined, as its name denotes, the essential characters of a reptile with the form and habits of a fish. No such creature has been known to exist within historic times; nevertheless, all the various parts of its complicated structure have their analogies, more or less perfect, in the present creation. It had the head of a Lizard, the beak of a Porpoise, the teeth of a Crocodile, the back bone of a Fish, and the paddles of a Whale. In length it sometimes exceeded thirty feet; it had a short thick neck, an enormous stomach, a long and powerful tail. This last appendage, together with four great paddles or fins, constituted the chief organs of motion. But of all its parts the head was perhaps the most wonderful and characteristic. In the larger species the jaws were six feet long, and were armed with two rows of conical sharp-pointed teeth,—a hundred below, a hundred and ten above. The cavities in which the eyes were set measured often fourteen inches across, and the eyeballs themselves must have been larger than a man’s head.

Now what we want particularly to impress upon our readers is, that the remains of this singular aquatic reptile abound throughout the whole extent of the Lias Formation in England. Far down below the surface of the earth they are found embedded in the marls, and clays, and limestones of Dorsetshire, and Gloucester, and Warwick, and Leicester, and Yorkshire. Sometimes whole skeletons are found entire, with scarcely a single bone removed from the place it occupied during life; but more frequently the scattered fragments are found lying about in a state of confused disorder; skulls, and jaw-bones, and teeth, and paddles, and the joints of the vertebral column and of the tail. The neighborhood of Lyme Regis is a perfectcabinet of these curious treasures. In some of the specimens there exhumed, a singular circumstance has been observed, which is deserving of special notice. We should naturally have expected, from the prodigious power of this animal, from the expansion of his jaws and the immense size of his stomach, that he preyed upon the other fish and reptiles that had the misfortune to inhabit the waters in which he lived. And so indeed it was. For here enclosed within his vast ribs, in the place that once was his stomach, are still preserved the remains of his half-digested food; and amidst the débris we can distinguish the bones and scales of his victims. Nay, in some of the more colossal specimens of this ancient monster, we can distinctly recognize the remains of his own smaller brethren; which, though less frequent than the bones of fishes, are still sufficiently numerous to prove that, when he wanted to appease his hunger, he did not even spare the less powerful members of his own species.76

Fig. 18.—Ichthyosaurus Platyodon. Museum of Trinity College, Dublin. Found in the Lias of Lyme Regis, Dorsetshire.

Fig. 19.—Ichthyosaurus Communis. Museum of Trinity College, Dublin. Found in the Lias of Lyme Regis, Dorsetshire.

It is with facts like these, which are revealed by the Crust of the Earth all over the world, that Geologists are called upon to deal. When they meet with skeletons and bones such as we have been describing, buried deep in the hard rock, hundreds of feet beneath the green grass, and the waving corn, they cannot help but ask the question: Where did these creatures come from? When did they live? And by what revolutions were they embedded here, and lifted up from beneath the waters of the deep?

In the same formation are found the remains of another ancient reptile, called the Plesiosaurus, that is to say, nearly allied to the Lizard. Of this extraordinary monster Cuvier observed that its structure was the most singular and anomalous that, up to his time, had been discoveredamid the ruins of the ancient world. It is chiefly distinguished from the Ichthyosaurus, to which it has no small affinity, by the enormous length of its neck, which, in some species, resembles the body of a serpent. Dr. Buckland tells us that in the Plesiosaurus Dolichodeirus the neck is longer than the trunk; the one being five times, the other only four times, as long as the head. Our illustration, for which we are indebted to the kindness of Doctor Haughton, represents a fine specimen of Plesiosaurus Cramptonii, which was found in the Lias Beds of Kettleness, near Whitby, in Yorkshire, and which is now a prominent object in the Museum of the Royal Dublin Society.

The habits and character of the Plesiosaurus have been thus sketched out by Mr. Conybeare:—“That it was aquatic is evident, from the form of its paddles; that it was marine is almost equally so, from the remains with which it is universally associated; that it may have occasionally visited the shore, the resemblance of its extremities to those of the turtle may lead us to conjecture. Its motion, however, must have been very awkward on land; its long neck must have impeded its progress through the water; presenting a striking contrast to the organization which so admirably fits the Ichthyosaurus to cut through the waves. May it not therefore be concluded (since, in addition to these circumstances, its respiration must have required frequent access of air), that it swam upon or near the surface; arching back its long neck like the swan, and occasionally darting it down at the fish which happened to float within its reach. It may perhaps have lurked in shoal water along the coast concealed among the sea-weed, and raising its nostrils to a level with the surface from a considerable depth, may have found a secure retreat from the assaults of dangerous enemies; while the length and flexibility of its neck may have compensated for the want of strength in its jaws, and its incapacity for swift motion through the water, by the suddennessand agility of the attack which they enabled it to make on every animal fitted for its prey, which came within its reach.”77

Fig. 20.—Plesiosaurus Cramptonii. Museum of the Royal Dublin Society.

The Pampas of South America are not less famous in Geology for the remains of Gigantic quadrupeds, than the Lias of England for its colossal marine reptiles. These vast undulating plains, which present to the eye for nine hundred miles a waving sea of grass, consist chiefly of stratified beds of gravel and reddish mud; and it is in these beds that the remains of many unshapely but powerful terrestrial animals have been found embedded. So abundant are they, that it is said a line drawn in any direction through the country would cut through some skeleton or bones. Indeed, Mr. Darwin is of opinion that the whole area of the Pampas is one wide sepulchre of these extinct animals. It will be enough for our purpose to describe one in particular, which, from its prodigious bulk, has received the appropriate name of Megatherium, or the Great Wild Beast.

The Megatherium, like the Ichthyosaurus and the Plesiosaurus, had many affinities with the existing creation. In its head and shoulders it resembled the sloth which still browses on the green foliage of the trees in the dense forests of South America; while in its legs and feet it combined the characteristics of the Ant-Eater and the Armadillo. But it was eminently distinguished from these and all the other modern representatives of the family to which it belonged by its colossal proportions. It was often twelve feet long and eight feet high; its fore-feet were a yard in length and twelve inches in breadth, terminating in gigantic claws; its haunches were five feet wide, and its thigh bone was three times as big as that of the largest elephant. “His entire frame,” as Dr. Buckland has admirably observed and carefully demonstrated, “was an apparatus of colossal mechanism,adapted exactly to the work it had to do; strong and ponderous, in proportion as this work was heavy, and calculated to be the vehicle of life and enjoyment to a gigantic race of quadrupeds, which, though they have ceased to be counted among the living inhabitants of our planet, have, in their fossil bones, left behind them imperishable monuments of the consummate skill with which they were constructed,—each limb, and fragment of a limb, forming co-ordinate parts of a well adjusted and perfect whole; and through all their deviations from the form and proportions of the limbs of other quadrupeds, affording fresh proofs of the infinitely varied and inexhaustible contrivances of Creative Wisdom.”

“This Leviathan of the Pampas, as it has been justly called, became first known in Europe toward the close of the last century. In the year 1789 a skeleton was dug up, almost entire, about three miles southwest of Buenos Ayres, and was presented by the Marquis of Loreto to the Royal Museum at Madrid, where it still remains. Since that time other specimens, besides numerous fragments, have been discovered, chiefly through the zeal and energy of Sir Woodbine Parish; by the aid of which the form, structure, and consequently the habits of this clumsy and ponderous animal have been fully ascertained. The complete skeleton which forms so prominent an object of attraction in the British Museum, and which is represented in the woodcut on the adjoining page, is only a model; but it has been constructed with great care from the original bones, some of which are to be found in the wall-cases of the same room, and others in the Hunterian Museum of the Royal College of Surgeons.”78

Fig. 21.—The Megatherium. From the British Museum. Length 12 feet; Height 8 feet.

Closely allied to the Megatherium, but somewhat less colossal in its dimensions, is the Mylodon. Its remains are found associated with those of the Megatherium and other great animals of the same family, in the superficial gravels of South America. A splendid specimen, which measures eleven feet from the fore part of the skull to the end of the tail, was dug up, in the year 1841, a few miles north of Buenos Ayres. It is well figured in the adjoining woodcut, which we reproduce, by kind permission of the Author, from Dr. Haughton’s admirable Manual of Geology.

Fig. 22.—Mylodon Robustus, from Buenos Ayres.

Passing from the petrified fish, and the reptiles, and thequadrupeds, that thus come forth, as it were, from their graves to bring us tidings of an extinct creation, we must next turn our attention for a moment to Fossil Shells. These relics of the ancient world, which are scattered with profuse abundance through all the strata of the Earth’s Crust, may seem, indeed, of little value to the careless observer; but to the practised eye of science they are full of instruction. They have been aptly called the Medals of Creation; for, stamped upon their surface they bear the impress of the age to which they belong; and they constitute the largest, we may say, perhaps, the most valuable part of those unwritten records from which the Geologist seeks to gather the ancient history of our Globe.

As regards the prodigious abundance of Fossil Shells preserved in the Crust of the Earth, it is unnecessary for us here to speak. We have already seen that the great mass of many limestone formations is composed almost exclusively of such remains, broken up into minute fragments, and more or less altered by chemical agency; and besides, there are quarries within the reach of all, where they may collect at pleasure these interesting relics of the olden time. But there are one or two facts of peculiar significance connected with Fossil Shells, which it may be useful briefly to set down. In the first place, we would remind our readers that there is a marked and well-known difference between the shells of those animals that can live only in the sea, of those that inhabit rivers, and of those, finally, that frequent the brackish waters of estuaries. Now it has been made clear beyond all reasonable doubt, by the explorations of Geologists, that sea-shells abound in great numbers far away from the present line of coast, in the heart of vast continents. And they are found, not merely on the surface, but buried deep in the Crust of the Earth, and overlaid, in many cases, by numerous strata of solid rock, thousands of feet in thickness. It is also to be observedthat they occur at all heights above the level of the ocean; having been discovered at an elevation of eight thousand feet in the Pyrenees, ten thousand in the Alps, thirteen thousand in the Andes, and above eighteen thousand in the Himalaya.79Such are the phenomena which are constantly forcing themselves on the attention of the Geologist, and which involve a number of problems that he cannot help attempting to investigate and explain. He is instinctively impelled to ask himself, how can the shells of marine animals have come to exist so far away from the sea? how have they been buried in the Crust of the Earth? how have they been lifted up to the highest pinnacles of lofty mountains?

Our subterranean exploration would be incomplete if it did not illustrate the Vegetable as well as the Animal Life of the ancient world. Let the reader then descend in fancy into the celebrated quarries of Portland on the south coast of England, and he will see the fossilized remains of a long past vegetation exhibited in a very striking manner. In one, of these quarries a vertical section, extending from the surface downward to the depth of about thirty feet, presents the following succession of strata arranged in horizontal layers:—first, a light covering of vegetable soil, beneath which are thin beds of cream-colored limestone, forming a stratum of solid rock ten feet thick; then a bed of dark-brown loam, mixed with rounded fragments of stone, and varying in thickness from twelve to eighteen inches. This is known to the quarrymen by the name of Dirt-bed, and seems, in former ages, to have supported a luxuriant vegetation; for all around are scattered the petrified fragments of an ancient forest. The prostrate stems and shattered branches of great trees are met at every step; but what is most striking and peculiar is, that, in many cases, the petrified stumps are still standing erect, with their roots fixedin the thin stratum of loam, and their trunks stretching upward into the hard limestone rock. Immediately below the Dirt-bed is another thick stratum of limestone, and below this again is a stratum of the famous Portland stone, so highly prized for building purposes. As the quarries of Portland are worked chiefly for the sake of this building stone, little attention is paid to the Dirt-bed and its contents, which are commonly thrown aside by the quarrymen as rubbish.

Fig. 23.—Section of a Quarry in the Island of Portland. Total thickness about thirty feet.

Vegetable soil.

Fresh-water Limestone.

Clay.

Laminated fresh-water Limestone.

Dirt-bed with fossil trees and plants.

Fresh-water Limestone.

Bed of Clay.

Portland building-stone full of marine shells.

The scene of this petrified forest is thus described by Doctor Mantell:—“On one of my visits to the island the surface of a large area of the Dirt-bed was cleared preparatory to its removal, and the appearance presented was most striking. The floor of the quarry was literally strewn withfossil wood, and before me was a petrified forest, the trees and plants, like the inhabitants of the city in Arabian story, being converted into stone, yet still remaining in the places which they occupied when alive! Some of the trunks were surrounded by a conical mound of calcareous earth, which had, evidently, when in the state of mud, accumulated round the roots. The upright trunks were generally a few feet apart, and but three or four feet high; their summits were broken and splintered, as if they had been snapped or wrenched off by a hurricane at a short distance from the ground. Some were two feet in diameter, and the united fragments of one of the prostrate trunks indicated a total length of from thirty to forty feet; in many specimens portions of the branches remained attached to the stem.”80

The Coal Measures of Europe and America offer to the student of Geology a boundless field for the investigation of Fossil Plants and Trees. We have already had occasion to notice the Sigillaria. This ancient tree, remarkable for its beautiful sculptured stem, has no exact representative in the vegetable kingdom of the present day. But it abounds everywhere in the Coal Measures; and there seems little doubt that several great seams of Coal are composed almost entirely of its carbonized remains. Indeed the ancient soil, which commonly constitutes the floor on which the bed of Coal reposes, is often as thickly crowded with the branching roots of the Sigillaria, as the soil of a dense forest with the roots of the trees by which it is covered. The stem itself, when converted into Coal, generally assumes the form of long narrow slabs; having been flattened by pressure during the process of mineralization. Sometimes, however, it is found uncompressed and erect. In this case the interior of the trunk is usually observed to have been filled up with sand or clay: and thus the forest tree, still retaining its external shape and character, is transformedinto a cylindrical shell of carbonized bark without, and a solid cylinder of sandstone or shale within. An interesting example is exhibited in our illustration, Figure 11.

Every Coal mine, too, is adorned with the imprint of the graceful Fern, which constitutes one of the most attractive features in the Flora of the ancient world. Not unfrequently it assumes a tree-like character, as it often does even now in tropical countries; and then, indeed, it is an object of striking beauty, reaching to a height of forty or fifty feet, and expanding at the summit into an elegant canopy of foliage.

Fig. 24.—Calamites Nodosus. From the Coal Measures of Newcastle.

The Calamite is another plant in which the Coal abounds. Its true botanical character is not yet clearly ascertained; but it bears a general resemblance, except for its giganticdimensions, to the common Horse-tail of our swamps and marshy grounds. It is a reed-like, jointed stem, sometimes thirty feet in length, hollow within, and curiously jointed without.

Fig. 25.—Lepidodendron Sternbergii; a Fossil Tree, 39 feet high. From a Coal Mine near Newcastle.

Scarcely less conspicuous than the Sigillaria, the Fern, and the Calamite, is the Lepidodendron or Scaly Tree, one of the most curious and interesting among the plants of the Coal-bearing period. Like the Sigillaria and the Calamite, it has been, and still is, a puzzle to the student of Botany. But it needs not the eye of science to see that it is unmistakablya stately forest tree, shut up in the Crust of the Earth, encased in a solid framework of indurated Shale, or Sandstone, or Coal, as the case may be, and overlaid with massive strata of rock hundreds of feet in thickness. Such a specimen as that represented in our woodcut was laid bare some years ago in Yarrow Colliery, near Newcastle.

Fig. 26 Lepidodendron Elegans. Portion of Stem and branches; Coal Mine, Newcastle.

In the same neighborhood was found a portion of the stem and branches of another variety, Lepidodendron Elegans, which will enable the reader to form a more complete idea of the appearance presented by this ancient tree as it stood in its primeval forest.

An unusually favorable illustration of our present subject may be seen at the colliery of Treuil, in France, not far from the city of Lyons. The beds of Coal are overlaid bya kind of slaty sandstone, ten feet thick; and this sandstone is traversed by the vertical stems of enormous petrified plants, chiefly Calamites. Here, then, to all appearance, we have an ancient forest enveloped in sandstone. We must suppose that the forest was submerged while the trees were still erect; that in this condition it received the sedimentary deposits carried down by the current of some great river; and finally, that these deposits were, in the course of ages, compacted into sandstone by a process already explained. It would seem that after the sandstone had been partially, at least, consolidated, it was subjected to a sliding movement here and there, by which the continuity of the stems was broken; the upper part being pushed on one side, as shown in our Figure.

Fig. 27.—Section of a Coal sandstone at Treuil, near Lyons. Showing the erect position of Fossil Trees. (Alex. Brongniart.)

It is time we should bring to a close our survey, meagre and imperfect as it is, of Fossil Remains. Those whodesire to pursue the inquiry for themselves will easily find an opportunity of doing so. There are few, we should suppose, who may not, occasionally, have access to one or other of those splendid Museums of Geology, which have been set up in all the great towns of Europe. And the still more extensive cabinets of Nature’s Museum, spread out beneath our feet, are within the reach of all.

But even the scanty facts which have been set forth faithfully, we trust, though perhaps feebly, in these pages, are sufficient to satisfy all reasonable minds that the bones, the skeletons, the trunks and branches of trees, which have been exhumed from the Stratified Rocks are really the remains of Organic Life that once flourished on the earth, or in the waters of the ancient seas. Obvious, however, as this fact must appear to all who have fully realized the character and appearance of Fossil Remains, it has been often vigorously assailed and vehemently denounced. In the early days of Geology phenomena of this kind were ascribed, not uncommonly, to the “plastic power of Nature,” or to the influence of the stars. Such notions, however, meet with little support among modern writers. They were nothing more than wild fancies, without any foundation either in the evidence of facts or in the analogy of Nature. The “plastic power of Nature” was a phrase that sounded well, perhaps, in the ears of unreflecting people; but no one ever undertook to show that Nature really possesses that “plastic power” which was so readily imputed to her. No one ever undertook to show that it is the way of Nature to make the stems, and branches, and leaves of trees, without the previous process of vegetation; or to make bones and skeletons which have never been invested with the ordinary appendages of flesh and blood. Yet surely this is a theory that requires proof; for all our experience of the laws of Nature points directly to the opposite conclusion. And as for the influence of the stars, we may be content to adoptthe language of the celebrated painter Leonardo da Vinci:—“They tell us that these shells were formed in the hills by the influence of the stars; but I ask where in the hills are the stars now forming shells of distinct ages and species? and how can the stars explain the origin of gravel occurring at different heights and composed of pebbles rounded as if by the action of running water? or in what manner can such a cause account for the petrifaction in the same places of various leaves, sea-weeds, and marine crabs?”81

In modern times the form of objection has been somewhat changed. We are told by some writers that, when we seek to explain the existence of Fossil Remains by the action of natural laws, we seem to forget the Omnipotence of God. They urge upon us, with much solemnity, that He could have made bones, and shells, and skeletons, and petrified wood, though there had been no living animal to which these bones belonged, and no living tree that had been changed into stone. And if He made them, might He not disperse them up and down through His creation, on the lofty mountains, in the hidden valleys, and in the profound depths of the sea? and buried them in limestone rocks and in the soft clay? and arranged them in groups, or scattered them in wild confusion as He best pleased?

To this line of argument we must be content to reply, that we have no wish to limit the power of God. But we have learned from our daily experience that in the physical world He is pleased to employ the agency of secondary causes; and when we know that for many ages a certain effect has been uniformly produced by a certain cause, and not otherwise, then if we again see the effect, we infer the cause. When a traveller in the untrodden wilds of Western America, comes upon a forest of great trees, or a herd of unknown animals, surely he never thinks of supposingthat the wild beasts and the forest trees came directly from the hand of the Creator, in that state of maturity in which he beholds them. And why? for it might be argued that the power of God is unbounded, and he might have created them as they now are if He had so pleased. Is it not that the traveller is impelled, by an instinct of his nature, to interpret the works of God which he now sees for the first time, according to the analogy of those with which he has been long familiar? Now this is just the principle for which we are contending. According to all our experience of the works of God in the physical world, the living body comes first, and the skeleton afterward; the living tree comes first, and afterward the prostrate trunk and the splintered branches. Therefore when we meet with a skeleton, we conclude that it was once a living body; and when we find the petrified stems, and branches, and leaves of trees, we have no doubt that they are the remains of an ancient vegetation.

But, in truth, if any one, with all the facts of the case fully before his mind, were deliberately to adopt this theory, that Fossils, as we find them now, were created by God in the Crust of the Earth, we candidly confess we have no argument that we should think likely to shake his conviction; just as we should be utterly at a loss if he were to say that the Pyramids of Egypt, or the colossal sculptures of Nineveh, or the ruins of Baalbec, were created by God from the beginning. The evidence of human workmanship is certainly not more clear in the one case than is the evidence of animal and vegetable life in the other. We believe, however, that no such persons are to be found; that theories of this kind have their origin, not so much in false reasoning, as in imperfect knowledge of facts; and we have, therefore, judged it most expedient not to spend our time in a discussion of philosophical axioms, but to set forth the facts, and leave them to speak for themselves.

Significance of fossil remains—Science of Palæontology—Classification of existing animal life—Fossil remains are found to fit in with this classification—Succession of organic life—Time in Geology not measured by years and centuries—Successive periods marked by successive forms of life—The Geologist aims at arranging these periods in chronological order—Position of the various groups of strata not sufficient for this purpose—It is accomplished chiefly through the aid of fossil remains—Mode of proceeding practically explained—Chronological table.

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