CHAPTER IX.

STRATIFIED ROCKS OF ORGANIC ORIGIN--ILLUSTRATIONS FROM VEGETABLE LIFE.

_Origin of coal--Evident traces of plants and trees in coal-mines--Coal made up of the same elements as wood--Beds of coal found resting upon clay in which are preserved the roots of trees--Insensible transition from wood to coal--Forest-covered swamps--Accumulations of drift-wood in lakes and estuaries--Peat bogs--Beds of Lignite--Seams of pure coal with half-carbonized trees, some lying prostrate, some standing erect--Summary of the argument hitherto pursued--Objection to this argument from the Omnipotence of God--Answer to the objection._

As animals, by organic action, extract lime from the waters of the ocean they inhabit, which, being converted in the first instance into minute shells, or stony skeletons, afterward passes into a compact and solid rock, so in like manner do plants and trees extract carbon from the atmosphere in which they vegetate, and convert it into coal. No reasonable doubt can now be entertained that coal derives its existence, almost entirely, from the woody tissue of sunken swamps and forests. Though the nature of the process by which this transformation takes place, is yet but imperfectly understood, and is, indeed, at the present moment a subject of much discussion and controversy, nevertheless the _fact_ that the change _has_ taken place is fully accepted by all as an established truth, and is supported by an accumulation of evidence which it is not easy to resist.

The first circumstance to which we shall call attention, is the wonderful profusion of vegetable life that is always associated with coal. Every one who has descended at any time into a coal mine, or who has examined the specimens usually exhibited in a well-furnished museum, must have been struck by the countless forms of trees and plants, which still remain vividly impressed on this black and unsightly mineral. Dr. Buckland has described this phenomenon with much vigor and beauty in his celebrated Bridgewater Treatise: “The finest example I have ever witnessed is that of the coal mines of Bohemia just mentioned. The most elaborate imitations of living foliage upon the painted ceilings of Italian palaces, bear no comparison with the beauteous profusion of extinct vegetable forms with which the galleries of these instructive coal mines are overhung. The roof is covered as with a canopy of gorgeous tapestry, enriched with festoons of most graceful foliage, flung in wild irregular profusion over every portion of its surface. The effect is heightened by the contrast of the coal-black color of these vegetables with the light ground-work of the rock to which they are attached. The spectator feels himself transported, as if by enchantment, into the forests of another world; he beholds trees of forms and characters now unknown upon the surface of the earth, presented to his senses almost in the beauty and vigor of their primeval life; their scaly stems and bending branches, with their delicate apparatus of foliage, are all spread forth before him, little impaired by the lapse of countless ages, and bearing faithful records of extinct systems of vegetation, which began and terminated in times of which these relics are the infallible historians.”

The next important fact that points to the vegetable origin of Coal is, that wood and Coal are both composed of the same ultimate elements--carbon, hydrogen, and oxygen. This analogy is the more remarkable when we are told that no other rock except Coal exhibits anything approaching to this composition. It is true that the elements just enumerated do not exist in the same proportions in wood and in Coal. But the difference, when rightly understood, rather tends to confirm our theory that the one is derived from the other. There is more Carbon in Coal than in wood; while there is less oxygen and less hydrogen. To explain how this may have come to pass during the process of transition, we must call in the assistance of the chemist. It appears from the researches of Liebig that, when vegetable matter is buried in the earth, exposed to moisture, and partially or entirely excluded from the air, the process of decomposition sets in, and that under this process carbonic acid gas and carburetted hydrogen gas are slowly evolved. At the same time a portion of the oxygen when set free would naturally enter into a new combination with a portion of the hydrogen, and form water. The result of these several changes would necessarily be, that the accumulation of vegetable matter buried in the earth would part, in course of time, with no small share of its carbon, its hydrogen, and its oxygen, but not with all in the same proportions: for the new combinations would use up more of the oxygen than of the hydrogen, and more of the hydrogen than of the carbon.[58] In other words, if the process should have gone on for a sufficient lapse of ages, these elements would no longer exist together in the proportions which are necessary to constitute wood, but would rather exist in the proportions which are found to constitute coal.[59]

This explanation is confirmed by a fact with which our readers are no doubt familiar. According to the explanation, carbonic acid and carburetted hydrogen are evolved during the process by which coal is produced from wood. We should therefore expect to find these gases closely associated with Coal. If they are _not_ so associated, their absence is a serious objection against our theory; but if they _are_ so associated, their presence is a strong evidence in its favor. Now on this point, as every one knows, practical miners bear testimony that the fact corresponds exactly with our theory. They tell us that reservoirs of Choke-damp, which is carbonic acid, and of Fire-damp, which is carburetted hydrogen, are found very commonly pent up in the crevices and cavities of coal beds, and are the cause, when tapped, of many of the accidents which take place. They even assure us that some beds of coal are so saturated with gas that, when cut into, it may be heard oozing from every pore of the rock, and the coal is called _singing coal_ by the colliers.[60]

To sum up, then, what we have said on this point: it appears, first, that the same constituent elements are found in wood and Coal; secondly, though they do not exist in the same proportions in the two substances, the difference is fully accounted for by the changes which we should naturally expect to take place when large accumulations of vegetable matter are buried in the earth; thirdly, in the hypothesis of these changes, carbonic acid and carburetted hydrogen would certainly be developed; and in point of fact, these gases are found intimately associated with Coal all over the world.

There is another remarkable fact which fits in most admirably with our theory. Coal is found at the present day in the Crust of the Earth, disposed in thin seams or beds, and each bed is almost uniformly found to rest upon a stratum of fine clay, sometimes several feet in thickness. This is just what our theory would lead us to expect. If coal is produced from plants and trees, these plants and trees must have grown upon some suitable soil; and, therefore, in this hypothesis we should expect, ordinarily speaking at least, to find a bed of clay beneath every bed of coal. But this is not all. When we examine more closely the stratum on which the coal reposes, we find the roots and stems of trees mingled with the clay in the greatest profusion. In the Welsh coal field, in a depth of twelve thousand feet, there are from fifty to a hundred beds of coal, each lying on a stratum of clay abounding in these remains.[61]

We now come to an argument of a practical kind which appeals to common sense and common experience. Let us suppose that a person wholly unacquainted with the art of manufacturing paper, were to enter a paper-mill when the workmen are away, and the process of manufacture for a time suspended. At first sight he would probably find it difficult to persuade himself, that the piles of clean white paper, which attract his notice at one end of the building, are produced from the heaps of filthy rags which he sees accumulated at the other. But if he be a sagacious observer, he will soon find evidence to convince him that this is really the case. For he will perceive, upon close examination, that the self-same material is exhibited in every intermediate state of progress from one extreme to the other. First, there is the great chest with its numerous compartments, in which the rags are seen carefully sorted, according to their various degrees of quality and texture. Next comes the fulling-mill, where they are washed and bleached. Then the revolving cylinder, furnished on the exterior surface with sharp blades or cutters; and the vat in which it moves is filled with the rags, which now assume the form of a thin liquid pulp. Advancing still further he will see this pulp evenly spread out upon a wire-gauze frame, and now at last it is beginning to exhibit some likeness to the form and substance of paper. Further on it is seen pressed and dried; and last of all cut into sheets and laid aside in lofty piles.

Now it seems to us that we are placed in somewhat of the same position, as regards the manufacture of Coal. We cannot observe the process actually going on; for though, in this process, the work is never suspended, the workmen never at rest, yet extending as it does over a space of many centuries, it is too slow to be sensible; and besides it is conducted in great part beneath the surface of the Earth. Nevertheless, we can trace the progress of change through each intermediate stage of the transition, from one extreme to the other,--from the primeval swamps and forests through the numerous varieties of the Peat and Lignite to the richest beds of pure Coal.

First, then, we have the great forest-covered swamps, like those which now occupy the valley and delta of the Mississippi. They are composed in many cases of pure vegetable matter without any intermixture of earthy sediment. A dense growth of reeds, and shrubs, and herbage of every kind, covers the whole surface of the land, mixed up with the decaying leaves and prostrate trunks of forest-trees. Sir Charles Lyell mentions a very remarkable fact observed in the swamps of Louisiana. During an unusually hot season, when any part of a swamp is dried up, if the surface be set on fire, a pit is burned into the ground many feet deep, in fact, as far down as the fire can descend without meeting water; and it is then found that scarcely any residuum or earthy matter is left.[62]

Vegetable strata of this kind are produced, not only upon dry land by the growth and decay of forests, but also beneath the waters of lakes and estuaries, by the accumulation of Drift-timber borne along in the current of swollen rivers. The Mackenzie River, which drains a great part of Northwestern America, affords many admirable illustrations. Flowing as it does from south to north, it is subject to annual inundations when the snows begin to melt in the higher parts of its course, while the channel lower down, situated in colder latitudes, is still blocked up with ice. At this season then it overflows its banks, and sweeping through vast forests, carries away thousands of uprooted trees in its impetuous torrent.

“As the trees,” says Dr. Richardson, “retain their roots, which are often loaded with earth and stones, they readily sink, especially when water-soaked; and accumulating in the eddies, form shoals, which ultimately augment into islands. A thicket of small willows covers the new-formed island as soon as it appears above water, and their fibrous roots serve to bind the whole firmly together. Sections of these islands are annually made by the river; and it is interesting to study the diversities of appearances they present according to their different ages. The trunks of the trees gradually decay until they are converted into a blackish-brown substance resembling peat, but still retaining more or less of the fibrous structure of the wood; and layers of this often alternate with layers of clay and sand, the whole being penetrated, to a depth of four or five yards or more, by the long fibrous roots of the willows. A deposition of this kind, with the aid of a little infiltration of bituminous matter, would produce an excellent imitation of Coal, with vegetable impressions of the willow roots.

“It was in the rivers only that we could observe sections of these deposits; but the same operation goes on, on a much more magnificent scale, in the lakes. A shoal of many miles in extent is formed on the south side of Athabasca Lake by the Drift-timber and vegetable débris brought down by the Elk River; and the Slave Lake itself must in process of time be filled up by the matters daily conveyed into it from Slave River. Vast quantities of Drift-timber are buried under the sand at the mouth of the river, and enormous piles of it are accumulated on the shores of every part of the lake.”

Not unfrequently it happens that these strata of vegetable matter, with the roots and trunks of trees, their branches, fruits, and leaves, more or less perfectly preserved, are covered over by subsequent deposits. Such accumulations, we are assured by Doctor Mantell, have been found deep in the soil on the coast of England, in places that are still subject to periodical inundations. “The trees are chiefly of the oak, hazel, fir, birch, yew, willow, and ash; in short, almost every kind that is indigenous to this island occasionally occurs. The trunks and branches are dyed throughout of a deep ebony color by iron; and the wood is firm and heavy, and occasionally fit for domestic use; in Yorkshire and elsewhere, timber of this kind is sometimes employed in the construction of houses.”[63] Here, then, is the first stage of the conversion of wood into Coal,--a stratum more or less compacted together of vegetable matter, spread out sometimes over the surface of the dry land, sometimes on the floor of lakes and estuaries, and often buried beneath an accumulation of subsequent deposits.

The next stage in the process of transformation may be represented by those Peat Bogs which constitute one of the most remarkable physical characteristics of Ireland, covering as they do an area equal to one-tenth of the whole island. In these the vegetable matter is more closely condensed, but the structure of the plants from which the Peat is derived is still preserved, and may be distinctly recognized by the naked eye. Nay, we have still the prostrate trunks of trees lying around on every side as they fell to the ground in their ancient forests. The researches recently pursued upon this subject have brought to light a fact which is very much to our present purpose; for it seems to prove our thesis by direct evidence. “In Limerick, in the district of Maine, one of the States of North America, there are Peat Bogs of considerable extent, in which a substance exactly similar to _cannel coal_ is found at the depth of three or four feet from the surface amidst the remains of rotten logs of wood and _beaver sticks_: the peat is twenty feet thick, and rests upon white sand. This coal was discovered on digging a ditch to drain a portion of the bog, for the purpose of obtaining peat for manure. The substance is a true bituminous coal, containing more bitumen than is found in any other variety. Polished sections of the compact masses exhibit the peculiar structure of coniferous trees, and prove that the coal was derived from a species allied to the American Fir.”[64] A similar phenomenon was observed by Doctor Dieffenbach in the Chathain Islands. In the same bed of peat he was able distinctly to trace a gradual transition from pure vegetable matter to a mineral substantially identical with common coal.[65]

But though Peat may thus, as it should seem, pass directly into pure Coal, there are many cases in which it first assumes a more imperfect form, known under the name of Lignite. This substance is described as of a brownish color, “soft and mellow in consistence when freshly quarried, but becoming brittle by exposure, the fracture following the direction of the fibre of the wood.”[66] It clearly occupies an intermediate position between Peat and Coal. Like the former, it still exhibits the stems and woody fibre of the plants from which it is derived, very little altered in their structure; while on the other hand it is already beginning to acquire some of the consistency and density of Coal; to which also it approaches much more closely in its chemical composition. It should be remembered, moreover, that Lignite does not designate a substance of a fixed, invariable character. On the contrary, under the one general name are comprised a definite number of varieties, leading from one extreme to the other by a series of almost insensible gradations; the extreme variety on one side being scarcely distinguishable from Peat, while the extreme variety on the other is practically identical with ordinary Coal. It can hardly be doubted, therefore, that Coal must have the same origin as Lignite, while it is at least equally certain that Lignite has been derived from Peat; and we have already seen what overwhelming evidence may be adduced to show that the origin of Peat is to be sought for in the sunken swamps and forests of a long past age.

Lastly, when we come to examine the texture of Coal itself, we find much to confirm the conclusion at which we have thus arrived. In beds of pure Coal the remains of many species of plants have been detected, and sometimes in such abundance as to constitute visibly the bulk of the Coal. Even large trees are sometimes found standing erect in the Coal fields, with their bark actually converted into this mineral. The annexed Figure represents a portion of the stem, together with the roots of a tall forest tree, Sigillaria, discovered not long ago in a Coal mine at Saint Helens, near Liverpool. The stem, which was nine feet high, was found erect in the seam of Coal, while the roots, ten in number, stretched away into the vegetable soil beneath.

Not less than thirty such trees, some of them four or five feet in diameter, and all incrusted with Coal, were laid bare a short time since, in a Colliery near Newcastle, within an area of fifty yards square. “In 1830,” writes Sir Charles Lyell, “a slanting trunk was exposed in Craigleith quarry, near Edinburgh, the total length of which exceeded sixty feet. Its diameter at the top was about seven inches, and near the base, it measured five feet in its greater, and two feet in its lesser, width. The bark was converted into a thin coating of the purest and finest Coal.” Again, “in South Staffordshire, a seam of Coal was laid bare in the year 1844, in what is called an open work at Parkfield Colliery, near Wolverhampton. In the space of about a quarter of an acre, the stumps of no less than seventy-three trees, with their roots attached, appeared, some of them more than eight feet in circumference. The trunks, broken off close to the root, were lying prostrate in every direction, often crossing each other. One of them measured fifteen, another thirty feet in length, and others less. They were invariably flattened to the thickness of one or two inches, and converted into Coal. Their roots formed part of a stratum of Coal ten inches thick, which rested on a layer of clay two inches thick, below which was a second forest resting on a two-foot seam of Coal. Five feet below this again was a third forest, with large stumps of Lepidodendra, Calamites, and other trees.”[67]

* * * * *

We have now brought to a close a very important line of argument in the Science of Geology. We have pointed out that, in the strata which compose the Crust of the Earth, there are rocks of various kinds, distinguished from one another as well by the nature of the materials which compose them, as by the manner in which these materials are arranged together; and we have shown that rocks presenting the same general appearances, and composed of exactly the same materials, are being produced in the present age upon the Surface of the Earth, through the agency of natural causes. Moreover, we have closely examined, in certain cases, the nature of the process by which the formation of these rocks is accomplished at the present day; and we have seen how difficult it is, when the facts of the case are once clearly before us, to resist the conclusion that the rocks which we now find buried in the Earth, were produced in some former age, by the same causes which are still at work. We shall next proceed to inquire how far this conclusion is confirmed by the independent evidence of Fossil Remains.

But before entering on a new line of argument, it is fit we should take notice of an objection which has sometimes been urged against the reasoning we have hitherto pursued, and which has done much to create and to keep alive a prejudice unfavorable to the Science of Geology. Religious writers have not unfrequently insinuated, and sometimes have plainly asserted, that, in ascribing the present structure of the Earth’s Crust to the operation of natural causes, Geologists would seem to make no account of God’s Omnipotence. A moment’s reflection will convince the reader that this charge is utterly unphilosophical. Is it not plain that the more fully we appreciate and acknowledge the wonderful works of Nature, the more deeply must we become impressed with the power and wisdom of Him who is the Author and Ruler of Nature? To say that secondary causes exist, and to point out the monuments that bear witness to their operation in long passed ages, is not to deny, but rather to affirm the existence of a Great First Cause, upon whom they all depend for their existence, their preservation, and their guidance.

We are everywhere reminded by abundant evidence, that it has pleased the Great Creator to employ the agency of His creatures in the fashioning and the adorning of this material universe. He does not create at once, as He well might do, the great oak of the forest; but He allows the seed to sink into the earth, where it is watered by the gentle dews of Heaven, and fructified by the genial warmth of the sun; soon it puts forth a tender germ; the germ, in time, imbibing the elements of its support from the air and the earth, becomes a sappling, and the sappling a tree, which spreads its huge branches on every side, and serves for many purposes of ornament and of use. Or let us take the case of the honeycomb, that most curious and ingenious work, at once the palace and the storehouse of a vast and busy community. It is not produced in a moment by a simple act of creation. God has not made it Himself, but He has taught the bee to make it. In like manner He has provided for the little birds, not by building their nests, but by infusing into their nature that mysterious instinct which prompts them to build, and guides them in their work.

Geologists, therefore, when they undertake to explain the existence of Stratified Rocks, not by the immediate action of the Creator, but by the intervention of natural causes, are not on that account to be accused of impiety. They do not disparage, but rather magnify His glory, when they expatiate upon the endless variety of agents which, according to their theory, He has employed in the structure of the material world. If the honeycomb, as a work of contrivance and design, excites the wonder and admiration of the philosopher, what must we think of the contrivance and design exhibited by Him who has made, not the honeycomb only, but the bee that builds the honeycomb? And so, too, we get novel and unexpected views of God’s Omnipotence, when, through the science of Geology, we come to understand the vast and harmonious series of secondary causes by which he has brought the Crust of the Earth into its present form and shape. The impress of His hand is stamped upon His works; and all that is wonderful and attractive in Nature is but the token of His power and the shadow of His beauty. And so our national poet has sung:

“Thou art, O GOD, the life and light Of all this wondrous world we see; Its glow by day, its smile by night, Are but reflections caught from Thee. Where’er we turn, Thy glories shine, And all things fair and bright are Thine.”

_CHAPTER X._

FOSSIL REMAINS--THE MUSEUM.

_Recapitulation--Scope of our argument--Theory of stratified rocks the framework of geological science--The theory brings geology into contact with revelation--the line of reasoning hitherto pursued confirmed by the testimony of fossil remains--Meaning of the word fossil--Inexhaustible abundance of fossils--Various states of preservation--Petrifaction--Experiments of Professor Göppert--Organic rocks afford some insight into the fossil world--The reality and significance of fossil remains must be learned from observation--The British Museum--Colossal skeletons--Bones and shells of animals--Fossil plants and trees._

Reader, you are beginning to suspect us. ‘How long do we propose to detain people?’ For anything that appears we may be designing to write on to the twentieth century. ‘And _whither_ are we going?’ Toward what object? which is as urgent a quære as, _how far_? Perhaps we may be leading you into treason. You feel symptoms of doubt and restiveness; and like Hamlet with his father’s ghost, “you will follow us no further unless we explain what it is that we are in quest of.”

These words of Thomas De Quincey to his readers, in the middle of one of his discursive essays, which, interesting as they certainly are in all their parts, yet sometimes beget a feeling of weariness from the uncomfortable apprehension that they will not come to an end, are, perhaps, scarcely less appropriate in our own case. It may be that our readers have been left too long in the uneasy state of suspense and hope deferred. They came to our pages to look for a practical solution of the question, Is Geology at variance with the Bible? And what avails it, they may ask, to discourse to them of the Gulf Stream, and Rivers, and Glaciers, and Alluvial Plains, and Coral Rocks, and Coal Mines? With painful steps they have been toiling after us through tedious disquisitions, straining their eyes to see the end, but the end is not yet in sight. Well, then, if they will rest for a few minutes by the way, we will pause, too, and tell them what we are about, and try to bring out more clearly the object at which we are aiming.

Our design from the beginning was to consider the points of contact between Geology and Revelation; to examine the relations that exist between these two departments of knowledge,--one resting upon reason and observation, the other given to us from Heaven; and to inquire how far it may be possible to adopt the conclusions of the former, while we adhere, at the same time, with unswerving fidelity, to the unchangeable truths of the latter. With this end in view, we proceeded at once to sketch out the more prominent features of Geological theory; not the particular theory of one writer, or of one school, but that more general theory which is adopted by all writers, and prevails in every school. This theory, we were all well aware, is in many points widely at variance with the common notions of sensible and even well-informed men who have not devoted much attention to the study of Physical Science. And it occurred to us that, possibly, many of our readers might be disposed to cut the controversy short by rejecting, in a summary way, the whole system of Geology, and treating it as an empty shadow or an idle dream. This, we were convinced, would be a mistaken and mischievous course. Geology is not a house of cards that it may be blown down by a breath. It is a hypothesis, a theory, if you will; but no one can in fairness deny that behind this theory there are facts,--unexpected, startling, significant facts; that these facts, when considered in their relation to one another, when illustrated by the present phenomena of Nature, and skilfully grouped together, as they have been by able men, disclose certain general truths, and suggest certain arguments, which do seem to point in the direction of those conclusions at which Geologists have arrived.

It follows that he who would investigate fairly the claims of Geology, must first learn to appreciate the significance of these facts, and to estimate the value of these arguments. And this is precisely what we have been trying to do. We are not writing a treatise on Geology. Certainly not: it would be presumptuous in us, with our scanty knowledge, to attempt it. Besides, Geology has it own professors, and its lecture-halls, and its manuals. Neither do we mean to assume the character of the advocates or champions of Geology. It does not ask our services; in its cause are enrolled no small proportion of the most illustrious names which for the last fifty years have adorned the annals of Physical Science. Nor do we want even to enforce upon our readers that more general theory of Geology which we are endeavoring to explain and illustrate. Our purpose is merely to collect from various sources, and to string together, the evidence that may be adduced in its favor; that so, when we come hereafter to consider this theory in its relation with the History of the Bible, we may not incur the risk of discomfiture by denying that which has been proved by facts, but rather approach the subject with such knowledge as may help us to discover the real harmony that we know to exist between the truths inscribed on the works of God, and those which are recorded in His Written Word.

In the accomplishment of this task we have devoted ourselves chiefly to the study of the Aqueous or Stratified Rocks. According to Geologists, these rocks, such as we find them now, were not the immediate work of creation, but were slowly produced in the long lapse of ages, and laid out one above another, by a vast and complex machinery of secondary causes. The elements of which they are composed were gathered together from many and various sources; from the ocean, from the air, from other pre-existing rocks; and, for aught we know, may have had a long and eventful history before they came to assume their present structure and arrangement. Thus, for example, the Conglomerates, and Sandstones, with which we are so familiar, are made up of broken fragments derived from earlier rocks, and then transported to distant sites by the mountain torrents, or the stately rivers of vast continents, or the silent currents of the sea; the Limestone with which we build our houses is the work of living animals that once swarmed in countless myriads beneath the waters of the ocean; and the Coal which supplies the motive power to our manufactories, our railways, our ships of war and commerce, is but the modern representative of ancient swamps and forests, which, having been buried in the earth, and there, by the action of chemical laws, endowed with new properties, were laid by for the future use of man in the great storehouse of Nature.

This mode of accounting for the origin and formation of Stratified Rocks constitutes in a manner the framework that supports and binds together the whole system of Geology. If it be once fairly established, Geology is entitled to take high rank as a Physical Science. If on the contrary it should prove to be without foundation, then Geology is no longer a science, but a dream. Moreover, it is this theory of stratification which, from the first, has brought Geology into contact with Revelation. For Geologists have been led to infer the extreme Antiquity of the Earth, from the immense thickness of the Stratified Rocks on the one hand, and, on the other, the very slow and gradual process by which each stratum in the series has been, in its turn, spread out and consolidated. Those likewise who claim for the Human Race a greater Antiquity than the Bible allows, seek for their proofs in the supposed origin and antiquity of those superficial deposits, in which the remains of Man or of his works are sometimes found entombed.

It is not to be wondered at, therefore, that the theory of Stratified Rocks should engage the largest share of our attention when we undertake to discuss the relation in which Geology stands to Revealed Religion. For the present we say nothing about the conclusions that flow from this theory, or the errors to which it has led when hastily or ignorantly applied: we are only investigating the evidence by which it is supported. In our former chapters we have drawn out at some length the line of reasoning which is derived from the character of the Aqueous Rocks themselves when considered in the light of Nature’s present operations. We have shown that Stratified Rocks of many different kinds, just such as those which compose the Crust of the Earth, have been produced by natural causes within historic times; and we have explained some of the more simple and intelligible parts of that complex machinery, which, even now, is busily at work gathering, sorting, distributing, piling up together, and consolidating the materials of new strata all over the world. These considerations, as we took occasion to point out, beget a strong presumption in favor of Geological theory. Here we have Nature at work, actually bringing into existence a stratum of rock before our eyes. And there, in the Crust of the Earth, we find another stratum of precisely the same kind already finished. What can be more reasonable than to ascribe the one to the action of the same causes which we see at work upon the other? And thus, by extending the area of our observations from one class of Aqueous Rocks to another, the idea gradually grows upon us that these rocks have been spread out, stratum upon stratum, during many successive ages, by the agency of secondary causes similar to those which are still in operation; and that each stratum, in its turn, as it first came into existence, was for a time the uppermost of the series.

In support of this conclusion we are now about to bring forward a new and independent argument founded on the testimony of Fossil Remains. An eminent writer has summed up in a few words the value and importance of Fossil Remains in reference to Geological theory. “At present,” he says, “shells, fishes, and other animals are buried in the mud or silt of lakes and estuaries; rivers also carry down the carcases of land animals, the trunks of trees, and other vegetable drift; and earthquakes submerge plains and islands, with all their vegetable and animal inhabitants. These remains become enveloped in the layers of mud and sand and gravel formed by the waters, and in process of time are petrified, that is, are converted into stony matter like the shells and bones found in the oldest strata. Now, as at present, so in all former time must the remains of plants and animals have been similarly preserved; and, as one tribe of plant is peculiar to the dry plain, another to the swampy morass; as one family belongs to a temperate, another to a tropical region, so, from the character of the embedded plants, we are enabled to arrive at some knowledge of the conditions under which they flourished. In the same manner with animals: each tribe has its locality assigned it by peculiarities of food, climate, and the like; each family has its own peculiar structure for running, flying, swimming, plant-eating, or flesh-eating, as the case may be; and by comparing Fossil Remains with existing races, we are enabled to determine many of the past conditions of the world with considerable certainty.”[68]

On this branch of our subject we do not mean to offer much in the way of argument strictly so called. We shall content ourselves with a simple statement of facts, and leave them to produce their own impression. It will be necessary at the outset to explain some technical matters, that what we have to say hereafter may be the better understood: and if in this we are somewhat dry and tiresome, we will try to make amends by the curious and interesting story of Nature’s long buried works, which we hope in the sequel to unfold.

* * * * *

When the word _Fossil_ was first introduced into the English language, it was employed to designate, as the etymology suggests, whatever is _dug out of the earth_.[69] But it is now generally used in a much more restricted sense, being applied only to the remains of plants and animals embedded in the Crust of the Earth and there preserved by natural causes. When we speak of remains, we must be understood to include even those seemingly transient impressions, such as foot-prints in the sand, which having been made permanent by accidental circumstances, and thus engraved, as it were, on the archives of Nature, now bear witness to the former existence of organic life.

Now in every part of the world where the Stratified Rocks have been laid open to view, remains of this kind are found scattered on all sides in the most profuse abundance. In Europe, in America, in Australia, in the frozen wastes of Siberia, in the countless islands scattered over the waters of the Pacific, there is scarcely a single formation, from the lowest in the series to the highest, that, when it is fairly explored, does not yield up vast stores of shells, together with bones and teeth, nay, sometimes whole skeletons of animals; also fragments of wood, impressions of leaves, and other organic substances.

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, which are 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.”[70] In 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 its _outward shape_ remain, but even its _internal texture_ is 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 which _the 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.”[71] This exposition, so simple and 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 what is 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 on dry 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 and skulls, 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 of the 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.

_CHAPTER XI._

FOSSIL REMAINS--THE EXPLORATION.

_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._

From the 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 found embedded 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, undisturbed and 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 dispersed over the cabinets of Europe. So closely are they sometimes packed together that many individuals are contained in a single block.

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 chiefly famous 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.

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 surrounded by 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]

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 for the 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 perfect cabinet 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]

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 discovered amid 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 suddenness and agility of the attack which they enabled it to make on every animal fitted for its prey, which came within its reach.”[77]

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]

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.

Passing from the petrified fish, and the reptiles, and the quadrupeds, 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 observed that 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.[79] Such 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 fixed in 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.

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 with fossil 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 transformed into 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.

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 gigantic dimensions, 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.

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 unmistakably a 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.

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 by a 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.

It is time we should bring to a close our survey, meagre and imperfect as it is, of Fossil Remains. Those who desire 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 adopt the 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 supposing that 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.

_CHAPTER XII._

GEOLOGICAL CHRONOLOGY--PRINCIPLES OF THE SYSTEM EXPLAINED AND DEVELOPED.

_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._

The existence of Fossil Remains is, then, a fact. Go where you will through the civilized world, and every chief town has its Museum, into which they have been gathered by the zeal and industry of man; descend where you can into the Crust of the Earth,--the quarry, the mine, the railway cutting,--and there, notwithstanding the plunder which has been going on for two centuries or more, you will find that the inexhaustible cabinets of Nature are still teeming with these remains of ancient life.

When we are brought, for the first time, face to face with these countless relics of a former world, we are impressed with a sense of wonder and bewilderment. That the skeletons before us, though now dry and withered, were once animated with the breath of life; that the trees now lying shattered and prostrate, and shorn of their branches, once flourished on the earth, we cannot for a moment hesitate to believe. But beyond this one fact, all is darkness and mystery. These gaunt skeletons, these uncouth monsters, these petrified forests, are silent, lifeless, as the rocks within whose stony bosoms they have lain so long entombed. Had they speech and memory, they could tell us much, no doubt, of that ancient world in which they bore a part, of its continents, and seas, and rivers, and mountains; of the various tribes of animals and plants by which it was peopled; of their habits and domestic economy; how they lived, how they died, and how they were buried in those graves from which, after the lapse of we know not how many ages, they now come forth into the light of day. As it is, however, we can but gaze and wonder. We have nothing here but the relics of death and destruction: there is no feeling, no memory, no voice, in these dry bones; no living tenant in these hollow skulls, to recount to us the history of former times.

So thinks and reasons the ordinary observer. But far different is the language of the Geologist. These dry and withered bones, he tells us, _are_ gifted with memory and speech; and, though the language they speak may seem at first unfamiliar and obscure, it is not, on that account, beyond our comprehension. Like the birds, reptiles, fish, and other symbols, inscribed on the obelisks of ancient Egypt, these bones and shells stored up in the Crust of the Earth, have a hidden meaning which it is the business of Science to search out and explain. They are Nature’s hieroglyphics, which she has impressed upon her works to carry down to remote ages the memory of the revolutions through which our Globe has passed; and when we come to understand them aright, they do unfold to us the story of that ancient world to which they belonged.

The interpretation of Fossil Remains is, then, an important department of Geology. Of late years it has been admitted to the rank of a special science, under the name of Palæontology, which means, as the word denotes--παλαιῶν ὄντων λόγος--the science which is concerned about the organic remains of ancient life. The honor of having been the first to place this science on a solid basis, in fact we may say the honor of having brought it into existence, is justly accorded to the distinguished Cuvier, whose name shed a lustre upon France during the early years of the present century. It is therefore still in its infancy; but it has already rewarded the zeal of its students by many wonderful and unexpected revelations. We purpose in the first place to examine the principles on which it is founded, and then to take a rapid glance at the conclusions to which it has led.

At the outset it is worthy of notice that the very existence of Fossil Remains, buried deep in the Crust of the Earth, forcibly confirms the Geological theory of Stratified Rocks. These rocks, as the reader will remember, are said to have been slowly spread out, one above another, during the lapse of many ages, by the operation of natural causes; and we have seen how this doctrine is supported by arguments founded on an examination of the rocks themselves,--of the materials that compose them, and of the way in which these materials are piled together. Now let us observe how clearly the testimony of Fossil Remains seems to point in the same direction.

First, the bones and shells which we now find in such profusion, far down beneath the superficial covering of the Earth, must have belonged to animals which, when living, flourished on what was then the surface. Yet now they are buried in the bosom of the hard rock, and covered over with beds of solid limestone, and sandstone, and conglomerate, hundreds and thousands of feet in thickness. How can we explain this fact, unless we suppose that these animals, when they perished, were embedded in some soft materials, which afterward became consolidated, and above which, in the course of ages, more and more matter was deposited, until at length that lofty pile of strata was produced, beneath which the remains are now found buried?

Again, it is part of our theory that the formation of Stratified Rocks took place, for the most part, under water. The Organic Remains, therefore, which we should naturally expect to find preserved in the strata of the earth, would be those of aquatic animals; or, if the remains of land animals were to be looked for, it should be of those chiefly which live near the banks of rivers and estuaries, and which, after death, might have been carried down by the current and buried in the silt and mud with which almost all rivers are charged at certain seasons of the year. We know as a fact that such animals are buried at the present day in the Deltas of the Ganges and the Mississippi; and it would be reasonable to suppose that the same should have occurred in former ages. Now here again the evidence of Fossil Remains exactly fits in with our theory. For the vast bulk of them are manifestly the remains of animals that lived in water: and the terrestrial animals, comparatively few, whose bones are preserved in the Crust of the Earth, are such as frequent the banks of great rivers or the marshy swamps of estuaries.

Thus much we may learn even from a cursory glance at Fossil Remains. But these curious monuments of ancient times have a deeper meaning, which cannot be unfolded without a more minute and laborious investigation. Our readers are aware that all the animals at present existing on the face of the Earth have been scientifically grouped together, according to certain well-marked characteristics, into various Kingdoms, Classes, Genera, and Species. Thus, for example, the horse and the dog are two different Species, belonging to the same Class of Mammalia; the eagle and the sparrow are two different Species of the same Class called Birds. Then again the Class of Mammalia and the Class of Birds both belong to the one common Kingdom of Vertebrata; because, though different in many other respects, they agree in this, that all the members of both Classes have a vertebral or spinal column, to which the other parts of the internal skeleton are attached.

Now when Cuvier began to examine closely the Organic Remains of former times, to which his attention was called by the bones dug up in the gypsum quarries of Montmartre, near Paris, about the close of the last century, he brought with him to the task a very large acquaintance with the various forms of life that, in the present age, prevail throughout the world. And he was greatly struck with the marked difference between those living animals with which he had been long familiar, and those with which he now became acquainted for the first time. The more he extended his researches, the more manifest did this difference appear; until at last it became quite clear that the great bulk of the animals whose remains are preserved in the Crust of the Earth, have no representatives now living on its surface. Nevertheless, he observed that, though the Species no longer exists, it often happens that we have still other Species of the same Genus; or if the Genus, too, be extinct, we have other Genera of the same Class. Here, then, is the first great truth at which Cuvier arrived, and which has been since confirmed by extensive observations:--that the animals which formerly dwelt on this Earth of ours, were, for the most part, widely different from those by which it is now inhabited: and yet there is a well-defined likeness between them; that both have been created on a plan so strictly uniform, that the one and the other naturally find their place in the same system of classification.

As the science of Palæontology progressed, and new facts were day by day accumulated, another truth, not less important, was gradually but certainly developed. In the distribution of Fossil Remains through the various strata of the Earth, there is a certain order observed, a certain regular law of succession, which cannot have been the mere result of chance, and which it is the business of science to unravel and explain. The facts are these. If we follow a particular set of strata _in a horizontal direction_, we find that the same fossils continue to prevail over hundreds of square miles, nay, often over a space as large as Europe, though beyond certain limits this uniformity of Fossil Remains will gradually be observed to disappear. But when we penetrate _in a vertical direction_ through the strata, the forms of animal and vegetable life that we meet with are constantly changing. After a few hundred yards at the most, we find ourselves in the midst of a group of fossils, altogether different from those which we have passed in the beds above: and so on, as we proceed downward, _each particular set of strata is found to have an assemblage of fossils peculiar to itself_.[82]

There can be no reasonable doubt as to the truth of these facts. They have been established and confirmed by the positive testimony of a whole host of Geologists, whose researches have extended to all parts of the globe. And we have besides a kind of negative evidence on the subject which is scarcely less convincing than the positive. Nothing is more easy than to refute a universal proposition if it is false. If it is not a fact that each group of strata, as we proceed downward, exhibits a collection of Fossils peculiar to itself, the assertion may be at once disproved by pointing out two or three different groups with the same Fossils. There are thousands of practical Geologists at work all over the world, eager for fame; and any one of them would make his name illustrious if he could overturn a theory so generally received. Now, when a statement of facts can be easily disproved if untrue; and when, at the same time, there is a large number of men whose interest it would be to disprove the statement if possible; and when it is nevertheless _not_ disproved; this circumstance, we contend, is a convincing argument that the alleged facts _are_ true. And such precisely is the case before us. We therefore think it would be unreasonable not to accept the facts.

Let us next examine what is their significance. Each group of strata, be it remembered, represents to us the animal life that flourished on the Earth during the period in which that particular group was in progress of formation. It is, as it were, a cabinet in which are preserved for our instruction certain relics or memorials of that age in the world’s history. Of course it is not a perfect collection; but only a collection of those remains that chanced to escape destruction, and by some natural embalming process to be saved from dissolution. When we learn, then, that there is a marked uniformity in the assemblage of Fossils that are spread over a large horizontal area, in any group of strata, we conclude that, when that group was in course of formation, there was a certain uniformity in the animal life that extended over the corresponding area of the globe; just as, at the present day, the same species of animals are found to flourish over a great part of Europe, or America. And if this uniformity of Fossil Remains does not extend horizontally to an indefinite distance, this is precisely what we should have expected from the analogy of the existing creation: for, when we examine the present distribution of animal life over the earth, we find a marked diversity to exist between countries that are removed from one another; as, for instance, between Europe and Australia.

In the next place, we are told that, as we proceed _downward_ into the Crust of the Earth, each successive group of strata has an assemblage of Fossils clearly distinct in character from those of the group above and of the group below. The conclusion to which this fact points is obvious enough. If, in the former case, we inferred that the animal life of any one period, considered in itself, was the same over extensive areas, in this case we must infer that the animal life of each successive period was _peculiar to that particular age_; being altogether distinct in its character from the animal life of the period that went before and of the period that followed. It would appear, therefore, as Sir Charles Lyell puts it, “that from the remotest period there has been ever a coming in of new organic forms, and an extinction of those which pre-existed on the earth; some species having endured for a longer, others for a shorter time; while none have ever reappeared after once dying out.”[83]

Now, from these principles, Geologists have been gradually led to build up a system of Geological Chronology; in other words, to determine the order of time in which the numerous groups of strata that make up the Crust of the Earth have been formed, and thus to fix the age of each group in reference to the rest. This Chronology is not reckoned by the common measures of time which are used in history, but rather by the successive periods during which each group of rocks was in its turn slowly deposited on the existing surface of the globe. For example, the Coal-measures that so abound in the North of England are very much older than the bluish clay of which London is built. But if we ask what is the difference between the age of the one and of the other, the answer is given not in days and years and centuries, but in the number of different Formations that intervened between the two. We are told that the Coal-measures belong to the Carboniferous Formation; that this Formation was followed by the Permian, and that again in succession by the Triassic, the Jurassic, and the Cretaceous; and that, upon this last was spread out the Eocene, to which the London clay belongs. Indeed, as regards the precise length of any given period, Geologists can offer nothing but the wildest conjectures. Some form their estimates in thousands of years; others in millions. And the wisest amongst them fairly confess they have no sufficient data to make an accurate computation. Nevertheless, they are all agreed in this, that the ages of which the memory is preserved in history, that is to say, the last six thousand years, are but a small part of one Geological period. Compared to the voluminous chronicles laid up in the Crust of the Earth, the records inscribed by human hands constitute but an insignificant fraction of the world’s history. Our readers will be glad to learn something of the way in which this startling system of Geological Chronology is constructed and developed.

At first sight, perhaps, it might be imagined that the order of time in which the various strata were deposited, can be easily learned from the relative position in which they lie. Since each stratum, when first produced, was spread out on the existing surface of the globe, it is clear that the one which lies uppermost in the series must be the newest, then that which lies next below, and so on till we reach the lowest of the pile, which must be the oldest of all. Nothing could be more satisfactory than this reasoning, if each stratum was spread out over the whole Earth, and if, after having been once deposited, it was never afterward removed. We might then regard each stratum as a volume in the Natural History of the Globe, which, when it was finished, was laid down upon that which contained the chronicles of the preceding age; and thus the position of every stratum would be in itself a sufficient evidence of the age to which it belonged.

But such is not the case. Nowhere does the Crust of the Earth exhibit a complete series of the Stratified Rocks laid out one above another. In any given section we can find but a few only of the long series of groups that are familiar to Geologists. And if we follow them on, in a horizontal direction, we shall invariably find that some of the strata will _thin out_ and disappear, while new strata will gradually be developed between two groups that were before in immediate contact. Let it be observed, in passing, that this fact fits in most perfectly with the theory we have been all along defending. The Stratified Rocks were deposited under water; therefore, the strata of any given period were not _spread out over the whole Globe_, but at most over those parts only which, for the time, were submerged. With the next period came a change in the boundaries of land and water; and the formation of strata ceased in some localities and began in others: and so on from epoch to epoch. Thus the areas over which the process has been going on, have been, in every age, of limited extent, and have been ever shifting from place to place over the surface of the earth. Moreover, there is the opposite process of Denudation. Many of the strata deposited in the depths of the ocean must have been afterward swept away by the breakers, as they slowly emerged from the waters; or at a later time, reduced to their original elements, and carried back to the sea, by the action of rivers, rain, and frost. It should seem, therefore, as well from the _fact_, which is obvious to any one who will examine it, as from our _theory_, which harmonizes so completely with the fact, that the strata which we meet with in any given section of the Earth’s Crust present to us but a very broken and imperfect series of monuments. They are, as it were, but odd volumes of a long series, and though they lie in juxtaposition, they may belong, nevertheless, to Geological epochs widely removed from each other.

Hence, in order to construct a complete system of Geological Chronology it is necessary to collect together these odd volumes, as they may be called, of the Great Geological Calendar, and to assign to each one its proper place in the series. This difficult and complicated task is accomplished chiefly by the aid of Fossil Remains. We have already shown that the Fossil Remains which are found embedded in each group of strata, represent the organic life of the period during which that group of strata was in progress of formation. Moreover, we have seen that each period was marked by the existence of an animal and vegetable creation peculiar to itself. If, therefore, we find that the Fossils of two different districts exhibit the same general character, we may conclude that the beds in which they are preserved were deposited about the same age, and consequently belong to the same Geological Period. Whereas, on the other hand, if, within certain limits, we discover two groups of strata, each of which has a collection of Fossils totally different from the other, it is a proof that these two groups were _not_ deposited in the same age, and must, consequently, be referred to different Epochs of the Geological Calendar. Let us now see in what manner the practical Geologist proceeds to apply these general principles.

He takes first some one country, say England, and in that country he selects some one particular district to begin with. Here he examines a number of different sections, and makes himself familiar with all the strata of the neighborhood, and with the order in which they lie. Let us suppose that he finds three different groups spread out one above another, and let us call these groups A, B, and C; A being the lowest, B immediately above A, and C above B. The chronological order of these strata will be, therefore, A, B, C. He will study next the Fossil Remains which he finds embedded in each group. For convenience we may designate the Fossils of A by the letter a, those of B by b, and those of C by c. Now, according to the principles above explained, these three collections of Fossils will be specifically distinct from one another, each collection being characteristic of one particular set of strata. Our Geologist next goes into a neighboring district, and there examines a number of sections as before. Let us suppose that he encounters again the groups A and B. He may, perhaps, have been able to trace the beds from one district to the other, by observations made upon his line of route: or it may be that the nature of the country has rendered such observations impossible; or the observations may have been so imperfect that from _them_ he could arrive at no certain conclusion regarding the identity of the strata. But, at all events, if the new district yield an abundant supply of Fossils, he cannot long be at a loss. He will recognize the group A by the Fossils a, and the group B by the Fossils b. An important fact, however, soon attracts his attention. Group C has entirely disappeared, and is not to be found in this district; while between A and B there is a new group of rocks that he has not seen before, with a collection of Fossils different from a, b, and c. We will call this new group X, and its Fossils x. It is clear that the formation of X must have intervened between the formation of A and B; and the chronological order now stands A, X, B, C. In like manner another district may disclose a fourth group of strata, say Y, intervening between B and C. The chronological order will then stand A, X, B, Y, C. And thus the Geologist pursues his explorations until he has gone through the whole country, and arranged the principal groups of strata according to the order of time in which they were deposited.

In this way the whole of England has been minutely explored during the last half century. The task was first undertaken by William Smith, who is justly called the Father of English Geology. After multiplied researches, extending over a space of many years, during which he travelled the whole country on foot, this eminent man published in 1815 his Geological Map of England and Wales with part of Scotland; a work which is described by Sir Charles Lyell as “a lasting monument of original talent and extraordinary perseverance.” Hundreds followed in the same course, exploring every day new districts, and, by the new facts which they brought to light, supplying what was wanting in the work of Smith, correcting what was faulty, and confirming what was true; until at length, in our day, it may be said that the Stratified Rocks of England are almost as well known and as completely mapped out as are its counties and its towns, its rivers, lakes, and mountains.

Meanwhile, Geologists were not idle in other parts of the world. Germany, France, Italy, even many districts of America and Australia, have been diligently explored according to the same principles as England. And by a comparison of the observations made, the Chronological order of strata over a considerable part of the Earth, but more particularly of Europe, has been now pretty fairly ascertained. This order we have attempted to set forth in an intelligible and sensible form by means of the table here annexed.

In the Woodcut are represented the strata hitherto examined by Geologists, laid out one above another, according to the order of time in which they are supposed to have been produced. The whole series is divided into a number of Formations, the names of which are given in the first column, together with an approximate estimate of their thickness, in feet. These Formations are distinguished from each other in the drawing by a difference of shading. Each of them, according to Geological theory, is believed to have come into existence by the accumulation of solid matter at the bottom of the sea; and the Period of time occupied in its production is usually designated by the same name as the Formation itself. Thus we read of the Carboniferous Formation and the Carboniferous Period: by the former phrase is meant certain groups of strata contemporaneously deposited over various parts of the Earth’s surface; and by the latter, the Period of time during which these groups of strata were spread out. In like manner, when we hear of the Carboniferous Fauna and Flora, we are to understand the animal and vegetable life that flourished during the Carboniferous Period. And again, when Geologists talk of the Cretaceous sea, and tell us that it rolled over a great part of what is now called Europe, they mean to speak of that sea on the bottom of which the Cretaceous rocks were deposited.

Most of the Formations comprise various groups of strata; and these groups are made up of different varieties of rocks, which are again divided into layers or beds of varying thickness. Even in these beds themselves we can often distinguish an indefinite number of laminæ or plates, scarcely thicker than a sheet of paper, which correspond to the periodical depositions of matter by which the rock was originally formed. These numerous subdivisions may be conveniently illustrated from the Carboniferous Formation. It is divided into two leading groups of strata; the Mountain Limestone below, the Coal Measures above. The upper group is the larger as well as the more important. It attains a maximum thickness in South Wales of 12,000 feet; and consists of numerous strata of Sandstone and Shale, with thin seams of Coal occasionally interposed. In one remarkable instance a hundred distinct layers of Coal, varying in thickness from six inches to ten feet, have been counted in one Coal-field, each resting on a bed of Shale, called in mining phraseology the Underclay. This Shale itself naturally divides into an indefinite number of thin plates, just like the stratum of mud accumulated by the annual inundations of the river Nile, and constituting the present soil of Egypt.

We have not attempted to represent in our Woodcut these various divisions and subdivisions of Stratified Rocks. But the names of some important and well-known groups we have had engraved, to impress more vividly on the mind the place to which they are to be referred in the Geological Calendar. Thus the reader may see at a glance the respective ages of the Coal and the Chalk; of the Lias, in which are preserved the remains of extinct gigantic reptiles, and the Glacial Drift, in which the elephant, the rhinoceros, and the hippopotamus are found entombed; of the Mountain Limestone, which is often nothing else than vast beds of Coral uplifted from beneath the waters of the ocean, and the Oolite, which includes the Portland quarries, where the petrified stems of ancient forest trees are found standing erect in the solid rock.

As the series of Stratified Rocks is divided by Geologists into a certain number or systems or Formations, so these are again grouped into still larger classes, called Primary, Secondary, and Tertiary; that is to say, first, second, and third, in the order of formation. These larger classes correspond to the Great Epochs or Ages of Geological time, each comprising within itself many distinct Periods. The Primary rocks are also called Palæozoic--παλαιὁν, ancient, and ξῶον, an organic being--because they contain the oldest forms of organic life: in like manner the term Mesozoic--μεσον, middle, and ξῶον--is applied to the Secondary strata, inasmuch as they contain the middle or intermediate forms of organic life: and the name Kainozoic--χαινὁν, new, and ξῶον--is given to the Tertiary, which contain the newest forms of organic life.

The term Post-Tertiary has recently been adopted to designate those superficial deposits which are subsequent to the Tertiary Age. They are divided into two groups; the Recent, which corresponds with the period of history, and the Post-Pliocene which precedes it. Some writers seem to think that these deposits, being so very insignificant and so very modern when compared with the long series of Stratified Rocks, are not truly Geological. But this, we should say, is a mistaken view of the question. It seems to us that even the minute layer of mud that is deposited every day at the mouth of the Ganges or the Mississippi, is linked on to the long chain of events which have brought the Crust of the Earth into its present condition; and, therefore, truly belongs to the science of Geology, and is deserving of its proper place in Geological classification.

We may here observe that the names of the great Geological Epochs are descriptive names; that is to say, the obvious meaning of the words corresponds to the character of the strata they are used to represent. Primary, Secondary, Tertiary, mean First, Second, and Third, in the order of formation: Palæozoic, Mesozoic, and Kainozoic, signify that the strata so called are characterized by Ancient, Middle, and Modern, forms of organic life. But it is very often quite otherwise with the names of the several Formations: and this is a point of no small importance to the student of Geology. These names must be regarded simply _as names_ employed to designate the strata formed in each successive period, and not exactly to describe their character. They generally had their origin in some accidental circumstance, or were derived from some particular locality; and afterward, being perpetuated, gradually came to receive a much more extended application than that which the words themselves would seem to suggest. Thus, for instance, the Cretaceous Formation is so called from the remarkable stratum of white chalk (creta) which was deposited during that period over a great part of Europe; but it would be a mistake to suppose that the whole Formation is made up of chalk. On the contrary, in different localities it is composed of very different materials; near Dresden, for example, it is a gray quartzose sandstone, and in many parts of the Alps it is hard compact limestone.[84] Again, the Devonian Formation derives its name from Devonshire, where the rocks of the Devonian period were first minutely examined; but we must not therefore infer that this Formation is peculiar to the county of Devon; it is to be found in many other parts of England, also in Ireland, and on the continent of Europe. So, too, another Formation has received the name of Carboniferous, which literally means Coal-bearing (carbo fero) because of the beds of Coal which are sometimes associated with its strata; yet this Formation is often found quite destitute of Coal over a very extensive area.

In looking over our Table of strata the reader must have noticed that the successive spaces in the Woodcut are not proportioned to the actual thickness of the successive Formations for which they stand. The Secondary and Tertiary Rocks taken together are scarcely one-third as thick, in reality, as the Primary; yet they occupy an equal space in the engraving: and, more remarkable still, the Cretaceous system is allowed double the space of the Laurentian, though less than half as thick. This circumstance calls for a passing word of explanation. In the early annals of a country there is generally a great scarcity of authentic records; and, from a simple dearth of facts, the history of a whole century is compressed, not unfrequently, into a few pages: whereas, in later times, when documentary evidence begins to accumulate, the historians will often spread out the events of two or three years over several chapters. Something of the same kind takes place in Geology. The Fossil Remains, from which, as from authentic documents, the Geologist chiefly derives his information regarding the history of the Earth’s Crust, are scanty in the earlier Formations, and abundant in the more recent. And thus it happens that the older Geological Periods, notwithstanding the vast thickness of the rocks by which they are represented, do not occupy a very prominent position in the annals of Geology, and are compressed into a comparatively insignificant space in its Tables. Nevertheless, the immense depth of the earliest Stratified Rocks must be taken into account in any attempt to estimate the comparative duration of the several Geological Periods. We have, therefore, set down, under the name of each Formation, an approximate estimate of its actual thickness, taken chiefly from the works of Doctor Haughton and Sir Charles Lyell.

Before bringing this chapter to an end we would observe that the system of classification we have here endeavored to explain does not pretend to be final and complete. It is, on the contrary, little more than a temporary expedient to render intelligible the results at which Geologists have hitherto arrived; and is liable to manifold modifications in proportion as their acquaintance with the records they have undertaken to interpret becomes more extensive and more minute. All that they now contend for is this: that the successive Formations represent successive Periods of time, which followed one another in the order here set forth, and during which the Earth was peopled with certain species of Plants and Animals, for the most part peculiar to their respective eras.[85]

_CHAPTER XIII._

GEOLOGICAL CHRONOLOGY--REMARKS ON THE SUCCESSION OF ORGANIC LIFE.

_Summary of the history of stratified rocks--Striking characteristics of certain formations--Human remains found only in superficial deposits--Gradual transition from the organic life of one period to that of the next--Evidence in favor of this opinion--Advance from lower to higher types of organic life as we ascend from the older to the more recent formations--Economic value of geological chronology--Illustration--Search for coal--The practical man at fault--The geologist comes to his aid, and saves him from useless expense._

With this sketch of Geological Chronology before us, we can now more fully realize to our minds the story we are told about the formation of the Earth’s Crust. In the earliest age to which Geologists can trace back the history of the Aqueous Rocks--for they do not profess to trace it back to the beginning--this Globe of ours was, as it is now, partly covered with water, and partly dry land. The formation of stratified rocks went on in that age, as it is still going on, chiefly over those areas that were under water--not indeed throughout the entire extent of such areas, but over certain portions of them to which mineral matter happened to be carried by the action of natural causes. And the Earth was peopled then as now, though with animals and plants very different from those by which we are surrounded at the present day. Some of these happened to escape destruction, and to be embedded in the deposits of that far distant age, and have thus been preserved even to our time. And these strata with their Fossils are the same that we now group together under the title of the Laurentian Formation: which being the oldest group of stratified rocks we can recognize in the depths of the Earth’s Crust, occupies the lowest position in our table of Chronology. Ages rolled on; and the Crust of the Earth was moved from within by some giant force, the bed of the ocean was lifted up in one place, islands and continents were submerged in another, and so the outlines of land and water were changed. With this change the old forms of life passed away; a new creation came in; and the Laurentian period gave place to the Cambrian. But the order of nature was still the same as before. The deposition of stratified rocks still continued, though the areas of deposition were, in many cases, shifted from one locality to another. And the organic life that flourished in the Cambrian times left its memorials behind it buried in the Cambrian rocks. Then that age, too, came to an end, and gave place in its turn to the Silurian: and this was, again, followed by the Devonian. Thus one period succeeded to another in the order set forth in our table; and every part of the globe was, in the course of ages, more than once submerged, and covered with the deposits of more than one age, and enriched with the Organic Remains of more than one creation.

As we advance upward in the series of Formations we soon perceive that the Fossil Remains, which, in the earlier groups were scanty enough, become profusely abundant, until even the unpractised eye cannot fail to mark the peculiar character of each successive period;--the exuberant vegetation of the Carboniferous, with its luxuriant herbage and its tangled forests, its huge pines, its tall tree-ferns, and its stately araucarias: the enormous creeping monsters of the Jurassic, the ichthyosaurs, the megalosaurs, the iguanodons, which filled its seas, or crowded its plains, or haunted its rivers; and higher up in the scale, the colossal quadrupeds of the Miocene and the Pliocene, the mammoths, the mastodons, the megatheriums, which begin to approximate more closely to the organic types of our own age. But amidst these various forms of life, the eye looks in vain for any relic of human kind. No bone of man, no trace of human intelligence, is to be found in any bed of rock that belongs to the Primary, Secondary, or Tertiary Formations. It is only when we have passed all these, and come to the latest formation of the whole series, nay, it is only in the uppermost beds of this Formation, that we meet, for the first time, with human bones, and the works of human art.

Thus it appears pretty plain, even from the testimony of Geology, that man was the last work of the creation; and that, if the world is old, the human race is comparatively young. These broken and imperfect records, which have been so curiously preserved in the Crust of the Earth, carry us back to an antiquity which may not be measured by years and centuries, and then set before us, as in a palpable form, how the tender herbage appeared, and the fruit-tree yielding fruit according to its kind; and how the Earth was afterward peopled with great creeping things, and winged fowl, and the cattle, and the beasts of the field; and then, at length, they disclose to us how, last of all, man appeared, to whom all these things seem to tend, and who was to have dominion over the fish of the sea, and the fowl of the air, and every living thing that moveth upon the earth. We do not mean to dwell just now upon this view of the history of creation so clearly displayed in the records of Geology. But we shall return to it hereafter when we come in the sequel to consider how admirably the genuine truths of this science fit in with the inspired narrative of Moses.

It may here, very naturally, be asked, if the records of Geology give us any information as to the manner in which each period of animal and vegetable life was brought to an end? Did the old organic forms gradually die out, and the new gradually come in to take their places? or were the one suddenly extinguished and the others as suddenly produced? This question has been a subject of controversy among Geologists themselves; and therefore it is somewhat outside our scope, since we propose to exhibit only that more general outline of Geological theory which is accepted by all. Nevertheless, as it is a question that must needs occur to the mind of every reader, it seems to call for a few words of explanation as we pass along. In the early days of Geology, it was commonly held that each great period was brought to an end by a sudden and violent convulsion of Nature. The Crust of the Earth was burst open in many places all at once; the bottom of the ocean was upheaved with a tremendous shock; the waters, driven from their accustomed bed, rushed with furious impetuosity over islands and continents; and the whole existing creation perished in a universal deluge. Then succeeded an interval of chaotic confusion, and when at length the waters subsided, and dry land again appeared, a new age in the history of the Globe was ushered in, and the Earth was again peopled by a new creation.

But this old theory has gradually given way as the Stratified Rocks have been more and more fully examined, and at the present day it is almost universally abandoned. Geologists have observed that the same species of Fossil Remains which prevail in the upper beds of one Formation, are met with also in the lower beds of the next, though in less numbers and mixed up with new species; and that, as we ascend higher and higher into the later Formation, the old species gradually become more and more scarce, while the new gradually become more and more numerous; until at length the characteristic forms of one age have disappeared altogether, and those of the succeeding age have attained their full development.

For this important fact, which was brought to light within the last half century, we are mainly indebted to the unwearied researches and great ability of Sir Charles Lyell. Speaking of the Formations of the Tertiary Epoch, to which, as is well known, he has principally devoted himself, this distinguished writer thus sums up the result of his long investigation:--“In passing from the older to the newer members of the Tertiary system we meet with many chasms, but none which separate entirely, by a broad line of demarkation, one state of the organic world from another. There are no signs of an abrupt termination of one fauna and flora, and the starting into life of new and wholly distinct forms. Although we are far from being able to demonstrate geologically an insensible transition from the Eocene to the Miocene, or even from the latter to the recent fauna, yet the more we enlarge and perfect our general survey, the more nearly do we approximate to such a continuous series, and the more gradually are we conducted from times when many of the genera and nearly all the species were extinct, to those in which scarcely a single species flourished which we do not know to exist at present.”[86] Hence he concludes, and his conclusion is now the common doctrine of Geologists, that the extinction and creation of species has been “the result of a slow and gradual change in the organic world.”[87]

It was long argued against this view, that we often meet, especially in the Primary and Secondary Formations, two groups of strata in immediate contact, in which there is a perfectly sudden transition from one set of Fossil Remains to another altogether different. Each group contains a countless variety of species, and yet there is not a single species common to the two. Does it not appear that in such a case the organic life of one period was suddenly destroyed, and that of the next as suddenly introduced? Not so; there is one link wanting in the argument. It must be shown that these two strata which are now in _immediate contact_ were originally deposited in _immediate succession_. But this it is impossible to prove: nay, it must needs be very often false. We have before observed that the areas of deposition were limited in every age, and were ever shifting from one locality to another. Therefore it must have been a frequent occurrence that, after one bed of rock was formed, the process of deposition ceased altogether in that locality, and did not begin again for many ages. Thus a long lapse of time often intervened between the deposition of two strata, which were laid out one immediately above the other. Furthermore, we have also seen that whole groups of strata may in any age be swept away by Denudation; and then the rocks which are next deposited in that locality, will be in immediate contact with strata indefinitely more ancient than themselves. From these considerations it is plain that two groups of strata which are now found in juxtaposition, may have been deposited in two Geological ages widely remote from each other. And consequently a sudden transition from the Organic Life of one group to the Organic Life of the other affords no proof of a sudden transition from the Organic Life of one Geological Period to the Organic Life of that which next succeeded. We may observe, however, that the recent researches, which have contributed so much to fill up the interstices of the Geological Calendar, have conduced in no small degree to fill up likewise some of the more remarkable gaps or chasms in the succession of Organic Life. It is, therefore, not unreasonable to suppose that, as our knowledge of the Earth’s Crust becomes more and more minute, the sudden breaks in the continuity of the scale will be still further diminished and the successive stages of gradual transition will be made more clearly apparent.

This subject has been very happily illustrated by Sir Charles Lyell:--“To make still more clear the supposed working of this machinery [for the deposition of Stratified Rocks and the preservation of Organic Remains], I shall compare it to a somewhat analogous case that might be imagined to occur in the history of human affairs. Let the mortality of the population of a large country represent the successive extinction of species, and the birth of new individuals, the introduction of new species. While these fluctuations are gradually taking place everywhere, suppose commissioners to be appointed to visit each province of the country in succession, taking an exact account of the number, names, and individual peculiarities of all the inhabitants, and leaving in each district a register containing a record of this information. If, after the completion of one census, another is immediately made on the same plan, and then another, there will, at last, be a series of statistical documents in each province. When these belonging to any one province are arranged in chronological order, the contents of such as stand next to each other will differ according to the length of time between the taking of each census. If, for example, there are sixty provinces, and all the registers are made in a single year, and renewed annually, the number of births and deaths will be so small in proportion to the whole of the inhabitants, during the interval between the compiling of two consecutive documents, that the individuals described in such documents will be nearly identical; whereas, if the survey of each of the sixty provinces occupies all the commissioners for a whole year, so that they are unable to revisit the same place until the expiration of sixty years, there will then be an almost entire discordance between the persons enumerated in two consecutive registers in the same province.

“But I must remind the reader that the case above proposed has no pretentions to be regarded as an exact parallel to the Geological phenomena which I desire to illustrate; for the commissioners are supposed to visit the different provinces in rotation; whereas the commemorating processes by which organic remains become fossilized, although they are always shifting from one area to the other, are yet very irregular in their movements. They may abandon and revisit many spaces again and again, before they once approach another district; and besides this source of irregularity, it may often happen that, while the depositing process is suspended, Denudation may take place, which may be compared to the occasional destruction by fire or other causes of some of the statistical documents before mentioned. It is evident that where such accidents occur, the want of continuity in the series may become indefinitely great, and that the monuments which follow next in succession will by no means be equi-distant from each other in point of time.

“If this train of reasoning be admitted, the occasional distinctness of the fossil remains, in formations immediately in contact, would be a necessary consequence of the existing laws of sedimentary deposition and subterranean movement, accompanied by a constant mortality and renovation or species.”[88]

There is another and a very striking fact in the succession of ancient organic life, which claims from us a moment’s notice. As we proceed upward through the series of Stratified Rocks, from the oldest to the newest, we find a gradual advance in the types of animal organization therein preserved, from the humbler and more simple forms of structure to those of a higher and more perfect character. That form of organization is regarded among Zoologists as the more perfect in which there is “a greater number of organs specially devoted to particular functions.” Now all the forms of animal life with which we are acquainted, may be reduced to two great divisions, the Vertebrate and the Invertebrate,--the former having a _vertebral_ or spinal column, the latter having none: and it is agreed in conformity with the notion set forth above, that the Vertebrate animals as a class exhibit a more perfect organization than the Invertebrate. Again, among the Vertebrate themselves there is a gradation; the Reptiles are ranked higher than the Fish, the Birds higher than the Reptiles, and the Mammalia higher again than the Birds.

All this we learn from Zoologists, who have pursued their investigations without any reference whatever to the science of Geology. It is, therefore, not a little remarkable that we should discover this very order and gradation of animal life in the successive groups of Stratified Rocks. All the Remains hitherto discovered in the earliest Geological Formations belong to Invertebrate animals, while the Vertebrate, which appear for the first time in the latter part of the Silurian Period, are, from that age on, more and more fully developed down to the present day, and now constitute, if not the most numerous, at least the most important part of the animal creation. Moreover, it is to be observed that the Vertebrate animals do not all make their appearance at once, but come in successively according to the same scale of organic perfection,--the Fish appearing first, then the Reptiles, then the Birds, and lastly the Mammalia. Even among the Mammalia a well-defined order of progressive succession has been observed, which finally culminates in the appearance of Man, the last created and the most perfect of animals.

This remarkable succession of animal life in the history of the Earth’s Crust will be more readily understood by means of the annexed Table. The remains of Invertebrate animals have been traced as far back as the Lower Laurentian Rocks. The Vertebrate first become manifest in the Ludlow beds of the Upper Silurian; where they are represented by the bones of Fish, the lowest class belonging to the Province of Vertebrates. Next in order come the Reptiles: the oldest known Reptile having been found in the Coal Measures of Saarbrück between Strasburg and Treves. The skeletons of Birds are rare in the Stratified Rocks. It is supposed that their powers of flight have in all ages secured them, to great a extent, from being carried away by floods, like other land animals, and buried in the sedimentary deposits of rivers and estuaries. Nevertheless their presence in the ancient world is frequently attested by their footsteps, impressed originally on the sandy beach, and still preserved now that the soft sand has been converted into solid rock. Such traces have been discovered in great abundance on the New Red Sandstone of the Connecticut River in America; and afford the earliest evidence we possess in the records of Geology regarding the existence of the feathered tribe. This group of strata belongs to the lower Trias. In the higher beds of the same Formation we meet with the first relic of ancient Mammals. It was found near Stuttgardt, in 1847, and belongs to the more imperfect form of Mammalian life, the Non-Placental. Similar remains have been since discovered in the Upper Trias of Somersetshire. The Placental, or more perfect form of animal life in the same class, first appears in the Eocene Formation: and the bones of Man, the highest of the Placental, are found for the first time in the upper deposits of the Post-Tertiary Age.

Let it be remembered that we are here but stating the facts which have been hitherto brought to light by the researches of Geologists. It may be, it is indeed most probable, that new discoveries will lead to numerous modifications in our Table. There is no reason to suppose that Geologists have yet exhumed the earliest remains of Vertebrates or Invertebrates preserved in the Crust of the Earth: that Fish may not hereafter be traced back beyond the Silurian, or Reptiles beyond the Carboniferous Period: that Birds may not be found among the Primary Rocks, and Placentals among the Secondary. But in a science which depends mainly upon observation, it is better to register the facts we have than to speculate idly about those we have not. And, having registered them, we cannot fail to be struck with the succession of animal life on the Earth, to which they seem to point. It is certainly deserving of notice that, as far as the Organic Remains hitherto discovered may be taken as a guide, Invertebrates and Vertebrates, Fish, Reptiles, Birds, and Mammals, Non-Placentals and Placentals, follow one another in the ascending series of Geological Formations exactly in the same order as they follow one another in the ascending scale of Zoological Classification.

* * * * *

And so Geologists go on ever searching out new phenomena, and grouping them together into classes, until from particular facts they lead us to general truths. Then starting with these general truths as the groundwork of their science, they proceed to sketch out the Natural History of our Globe from the remotest ages of the past down to the present time. They first study the stratified deposits of each succeeding age, and analyze the Fossil Remains embedded therein; afterward they make their inferences, and they compile their history. They describe the forms, the character, the habits, of the plants and animals that flourished of old in this world of ours; they tell us where the deep sea rolled its waves in each succeeding age, and where the dry land appeared; they point out the Deltas of its ancient rivers, they measure the breadth of its Estuaries, they trace the course of its Glaciers, they mark the outlines of its Mountain chains. But with these and such like speculations we are not here concerned. Many of them are open to controversy, and not a few are at this moment warmly disputed among Geologists themselves: besides, whether true or false, they do not in any way affect the relations between Geology and Revealed Religion. We shall be quite content, and it is all that our present scope demands, if we have made intelligible the general theory of Geological Chronology, and the kind of evidence on which it rests.

Before taking leave of this subject, however, we will venture to offer what seems to us an interesting illustration of the principles we have been explaining in the last two chapters;--one that will help to confirm the conclusions for which we have been contending, and that will also bring home to many minds the practical advantage to be derived from a thorough knowledge and just application of Geological science. Perhaps, too, it may help to revive the flagging attention of our readers; for the subject of our illustration is _Coal, and the way to find it_. In this age of manufactories and steam-engines,--when the atmosphere of great towns is heavy with smoke, and the quiet solitude of the country is so rudely disturbed by the shrieking of the railway-whistle and the snorting of the sooty locomotive,--this black, dirty mineral has acquired a value and importance, which may succeed in rousing even the practical money-making man to pay some heed to the lessons of science.

Coal might have been produced in any Geological Period; and in point of fact, beds of coal have been discovered in many different Formations. But in England, and in Western Europe generally, it has been found by long experience that the Coal-beds of the Carboniferous Formation are more abundant, and of better quality, than those of any other. Indeed the beds of Coal that occur in other Formations are so thin, and of such inferior quality, that they cannot be worked with profit. It is therefore of the highest importance in the search for Coal, before going to the enormous expense of sinking deep shafts, to discover whether or no the rocks in which the search is to be made belong to the Carboniferous Period. In this matter the more _practical man_ is often seriously at fault. Coal-bearing strata generally consist pretty largely of dark-colored clay, black shales, and similar deposits. This is a fact which, as it strikes the eye, is perfectly familiar to all who are engaged in the working of Coal mines. Hence it happens, not unfrequently, that the practical man, when he meets with strata of this kind, is apt at once to infer that Coal is near at hand. The Geologist, on the contrary, knows well that such strata are not peculiar to the Carboniferous rocks, but are often found in other Formations in which there is no Coal at all, or at least no Coal that will repay the expense of working; and therefore he will pronounce it most rash to undertake costly works on the strength of these appearances. He has learned, however, that there are certain species of animals and plants which are found in the Carboniferous rocks and in them alone; he will search for these in the strata which it is proposed to explore, and by their presence or their absence he will know whether the strata in question belong to the Carboniferous Formation or not.

Again, it will often happen that, in the midst of an extensive region well known to abound in Coal, the rocks which appear at the surface in one particular locality, are not wholly devoid of Coal, but exhibit no resemblance either in mineral character or in Fossil Remains to the Coal-bearing strata. A question then arises of the highest practical importance. May it be that the Coal-bearing strata are spread out beneath this uppermost bed of rocks? and is it worth the expense to sink a shaft through the one in the hope of reaching the other? The practical miner has no very clear or certain principles to help him in the solution of this problem; and thus it has often happened that thousands upon thousands of pounds have been expended in sinking shafts to look for Coal, where, as it afterward proved, there was not the slightest chance of finding it. Now, though Geology cannot tell if we shall succeed in finding Coal beneath these rocks, it _can_ tell if there is a _good chance_ of succeeding. It can tell whether there is a reasonable hope, by penetrating into the Crust of the Earth at this particular spot, of reaching the Carboniferous Formation; and if we can reach the Carboniferous Formation in the midst of a Coal district, it is very likely we shall meet with beds of Coal.

His first object will be to ascertain what is the Formation to which the superficial rocks belong. If it be a Formation earlier in date than the Carboniferous,--the Silurian, for instance, or the Devonian,--he knows that it would be simply waste of money to look for Coal beneath them; because the Carboniferous rocks cannot possibly be found underneath the rocks of an earlier age. And so the Geologist can tell beforehand what the mere practical man would find out only when he had spent his money. If, on the other hand, the rocks which appear at the surface belong to a period later than the Carboniferous, the Geologist will not always conclude that it is expedient to sink a shaft in search of Coal. For though the Carboniferous rocks may, in this case, be underneath, they may be so far down in the Crust of the Earth that we should have no chance of ever reaching them. Suppose, for example, that the strata which appear at the surface belong to the Cretaceous Formation. He knows from his Chronological table that the Carboniferous age is separated from the Cretaceous by three intermediate Periods,--the Permian, the Triassic, the Jurassic. Therefore, when he finds the Cretaceous rocks at the surface in any locality, it is quite possible, though of course not certain, that before the Carboniferous Formation could be reached it would be necessary to bore through thousands of feet of Jurassic, Triassic, and Permian rocks. And even then there would be no certainty of meeting with the Coal-bearing strata. Perhaps they were never deposited over this area of the earth’s surface; or, if deposited, perhaps they were subsequently swept away by Denudation. Hence our Geologist would reasonably conclude that, the probable expense of the search being so enormous, and the chance of success so remote, it would be much wiser not to make the attempt.