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Theexistence 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, onceflourished 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,aregifted 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 beenadmitted 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 softmaterials, 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 sameClass 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 lessimportant, 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 stratain 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 penetratein a vertical directionthrough 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 sogenerally 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 neverthelessnotdisproved; this circumstance, we contend, is a convincing argument that the alleged factsaretrue. 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 proceeddownwardinto the Crust of the Earth, each successive group ofstrata 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 waspeculiar 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 followedby 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 ofthe 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 willthin outand 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 notspread 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 thefact, which is obvious to any one who will examine it, as from ourtheory, 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 GeologicalChronology 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 werenotdeposited 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 ofB 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 fromthemhe 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 oftime 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.
TABLE OF STRATIFIED ROCKS,CHRONOLOGICALLY ARRANGED.
TABLE OF STRATIFIED ROCKS,CHRONOLOGICALLY ARRANGED.
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 theannual 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 simplyas namesemployed 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 differentlocalities 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.84Again, 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 theearlier 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
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.
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Withthis 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 escapedestruction, 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.”86Hence 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 singlespecies 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 inimmediate contactwere originally deposited inimmediate 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 scalewill 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 oforgans 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 avertebralor 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.