CHAPTER V.TIME, AND THE GEOLOGICAL EPOCHS.
The speculations of geology respecting the arrangement and position of the mineral masses of the earth are matters of direct observation, falling immediately under the cognizance of the senses, and whose verifications are both numerous and conclusive. But a question thereupon arises which is not so easily dealt with, namely, as to the periods of time that have elapsed during the various successive epochs or formations described. Looking at the current operations of the laws of nature, and supposing their uniformity in past ages, a scale of increment is laid down for the several deposits of which the earth’s crust is composed. An approximation is made as to the number of years required for each, and the result is, that the geological estimate embraces an inconceivably lengthened and bewildering series. The calculation proceeds not by hundreds, or thousands, but by millions of the terms of our numerical notation: and, as the fossiliferous strata alone are reckoned at about seven or eight miles in thickness, the time that has elapsed since the first appearance of life upon the planet, has also been made a matter of measurement. Accuracy as to any precise definite amount, is not, indeed, pretended; but no estimate, it is said, made upon purely geological data, falls short of vast enormous periods, which will only bear to be compared with the cycles of astronomical phenomena, and not with the brief fleeting days of man’s existence.
What account, then, is to be made of this reckoning according to the popular opinions respecting the origin of the world? Will it be accepted by the Christian, who confides in the Mosaic chronology of the work of creation? What is that chronology? Can the geological and the sacred be compared or reconciled with one another?
I. There is one important deduction to be established from these investigations which meets us at the threshold of the inquiry, namely, that geology clearly and distinctly shows there is abeginningto the course of creation as respects the crust of the earth and its organic forms of life. The stratified rocks all manifest succession in their order of deposition, and, therefore, also succession in time. Some are prior to and older in formation than others; and all of every class and quality, demonstrate principles of arrangement in conformity with law and design. We never, for example, get back to a period, however deep we go into the interior, in which we find the matter of the earth assuming, as it were, different modes of existence, or arranging itself according to affinities of which we have no experience. Over every material substance, the rocks of the oldest as of the newest formation, the same physical forces are seen to be operative. The granites, with all the molten amorphous masses of every age, are composed of ingredients brought together and aggregated in proportional quantities, and according to definite principles of attraction. But throughout the whole series and succession of deposits, we never come to a point at which matter has been formless, or free from the operation of law, endlessly quiescent, or when no controlling designing hand was rendering it plastic and obedient to its will.—As with the arrangements of matter, therefore, so likewise with its origin. We revert in both cases to a necessarily prior cause. And geology, vast and inconceivably great as may be its cycles, proclaims over all its past antecedents and depths of accumulation, thattime, not eternity, is indelibly recorded.
This truth is rendered still more apparent and intelligible, when we consider the various families of plants and animals of which the earth has been the theater. These organic structures at once speak to the mind of creative interference. No principle that we know of inherent in nature could, of itself, originate these forms. The first thing of life indicates an intelligent Creator. But epoch after epoch passes away, and along with them their living tribes generally perish. Succeeding races, of different characters and habits, are called into existence. The earth is again peopled—again to be swept of all its garniture—the land and ocean to change places—creatures of another mold, suited to both, againto be brought into existence. These phenomena all speak, not only of a beginning, of successive periods of time, but also of direct superintendence over the course of events from age to age.
It is the same with the formations themselves in which the organic things are imbedded. The course of creation progresses, but always under such breaks and renewals as clearly to manifest, that the same power which watches over the organic, is operative also in respect of the inorganic structures of the earth. Various are the genera and species of once animate forms, imbedded in the different strata beneath our feet; but equally various are the strata themselves; as a new race arises, so are there new forms of rocks produced along with them. And when we compare the two extremes of the fossiliferous strata, the silurian and the tertiary, or any of the intermediate—the old red sandstone and the oolites, the carboniferous and the chalk—we find that the rocks are just as various in quality, structure, and appearance, as are the animals which existed and perished during their respective epochs. The lines of demarkation are distinct. They may sometimes run into each other, so as to leave it doubtful where the one series ends and the other begins; but so it is with the organic remains themselves, a few of an antecedent epoch living into and invading the province of another, when the limit is reached, and the family altogether disappears. The same law holds in the great mineral masses of the earth’s crust. Rocks are of different families, even as plants and animals are; and over the entire surface of the globe, they display in their various suites such changes and diversities as demonstrate an interfering hand and a new creative energy. Indeed, there is, it may be avowed, a much greater diversity of type in the mineral groups themselves than in their organisms, the living genera and species of one formation differing, often, less from each other than do the rocky matrices in which their remains are imbedded.
II. But, in estimatingthe timethat elapsed during the formation of the various sedimentary strata, are geologists warranted in assuming such principles of calculation as have been adopted?—There are two aspects under which the subject may be approached—theone, as respects the formative process of rocks—the other, the probable duration of life in the different epochs, or rather, as connected with the formations which indicate the epochs.
1.Of the Formative Process.How long the earth existed before being brought into a habitable condition for either vegetable or animal bodies, geology has no means of determining. The primary crystalline beds are the oldest rocks of which we have any knowledge: we can penetrate at least to no antecedent matter, bearing the record of its own age, out of which these rocks were produced. We are warranted, therefore, in accounting for their origin, to remount at once to the initial creative act which called them into being, and the presumption is, that no great length of time was occupied in this arrangement. The Divine will commanded, every particle obeyed, and all took their places. The eruptive rocks are of comparatively sudden growth: they are not the result of a gradual deposition, but of igneous fusion in the interior of the earth, and elevated to the surface through the operation of forces of rapid activity. How long our planet was in thus assuming form, and the dry land appearing, we have no certain means of judging, except by looking to the end of its creation, and assuming that the “void” was not permitted indefinitely to continue. The occupancy of life at once exalts the work and illustrates its purpose.
The fossiliferous strata were formed in different circumstances and under different conditions, when the course of nature, if we may so speak, was fully established, and the train of events under the operation of physical law commenced its onward march. The oldest of the fossiliferous deposits is the Silurian. It likewise constitutes one of the greatest depth, as well as of extent, on the surface of the globe. The position, generally, of the silurian beds, is along the line of the great mountain-chains, except in Russia, where they spread over the interior, and thin out into smaller dimensions, and where, from the absence of the intrusive rocks, they are only semi-indurated. This system of rocks was, therefore, formed in circumstances the most favorable for rapid accumulation, amidst such primal operations of nature ashave never been repeated upon the same scale of magnitude. The first shaping-out, if we may so speak, of the earth’s surface, in the elevation of its mountain-ranges and corresponding depressions of the sea-bottom, bears all the marks of a single cotemporaneous act, not completed in a moment of time indeed, but continued through a period of unparalleled spasmodic agency. Every region shared in the convulsive movements, and the whole earth, in one and the same age, was begirt with mountains. These violent throes were accompanied everywhere with violent action upon the already consolidated masses. Disintegration would keep pace upon them with the rate of uprise. And as the bare jagged rocks unprotected with herbage, friable and just rending from the fire, were lifted suddenly above the waters, the waters in turn would dash violently upon their sides and broken serrated crests, and so become as rapidly filled again with all the waste and spoils of the period. The changes now going on, and the rate of increment of the land above sea-level, the occasional appearance and disappearance of an island, the slow but constant action of the waves upon the coast, and the detrital matter borne down by the rivers, can be no measure of the effects of forces and agencies such as were then in operation. The Mississippi, within a quarter of a century, it has been ascertained, brings down little more than a half of its former spoils. The organic remains, accordingly, which have survived the silurian period, belong chiefly to the molluscous classes, and thin filmy fucoid vegetables; the structures, in short, which were best calculated to live during the period in question, and to remain undestroyed throughout its agitations.
The old red sandstone series is likewise of vast extent, both in depth and superficial area. The scale of its mass corresponds with the scale of the forces which produced it—the magnificent operations amidst which it was accumulated. This was a period of great and frequent trappean eruption. Hence the conglomerate red offers a splendid specimen of rapid formation. This member of the devonian suite consists of large masses of gneiss, quartz, mica-slate, and hornblende rock, cemented in a paste of silicious sand, probably the debris of dissolved granite. The included portions bear all the marks of attrition, of violent tossing about ina troubled sea. Estimate the thickness of the whole deposit at its maximum of nearly ten thousand feet—consider what vast agencies were still at work, in tearing up and carrying off the spoils of the mountains—probably with but little pause or intermission in the violence of the action—and thus, not so much in the light of remote antecedents as of comparatively associated formations, will we be warranted in regarding these early courses in the work of creation. The fishes of the period all speak of its spasmodic character, mailed, plated, and completely inclosed in strong horny integuments; their heads, some of them, of entire uncovered bone, and their caudal fins propelling with the whole force of the vertebral column,—conditions of structure which give indications of the stormy seas whose waves they had to buffet, and of the conserving properties by which their forms and outlines have been transmitted to us so wonderfully entire.
The carboniferous class of rocks have all the marks of a very peculiar formation, constructed for a special purpose, and elaborated amidst an extraordinary state of things. Here we meet with vast accumulations of vegetable, calcareous, and metallic substances, for which we detect no anterior preparations. The coming on and the outgoing of the whole coal series are as distinct as they are surprising. To what are we to compare them? By what scale of time are we to adjust the terms of their growth? Proceeding upon the existing laws of nature, calculations have been made as to the rate of increase, for a year, of pure vegetable matter, over a given area. The Ganges, Nile, Amazon, Mississippi, La Plata, and the other mighty rivers of the earth, have been appealed to as to the quantities with which they are annually charged. The forests, with their load of every revolving season, have been weighed, when their decadence of leaves, fruits, branches, and all the gatherings from the flood and storm have been duly taken into account. The result is, according to this method of solving the problem, that about six hundred thousand years were occupied in the production of the whole coal series.—It must be admitted, in any attempt to reduce this number, that the violent forces of the antecedent periods cannot be admitted as data of circulation; throughout the whole of the carboniferous era, a state of repose seems to have universally prevailed. Butthen all the living productive powers of nature were just as violently in operation as the others were quiescent, and the result in the one case bears a proportion to the result in the other. If inorganic matter was rapidly collected by the action of violent causes, so under an extraordinary state of things, of climate, moisture, atmosphere, and other physical arrangements, organized bodies, vegetable and animal, would multiply as rapidly. A condition of nature that produced uniformity of vegetation over the entire surface of the globe, as the coal deposit everywhere manifests, and all of gigantic dimensions in every family of plants, is not merely to be denominatedtropical, and its results calculated by a scale of existing weights and measures. In many places of the earth, even now, several harvests are reaped within the year. Who can set bounds to their number, or guess the prodigious increase, when the whole earth was covered with a flora, not only of unrivaled exuberance, but of uniform distribution nearly on every part of its surface? But a test of indisputable value, for ascertaining the rate of increase in the sandstones and shales embraced within the coal-measures, occurs in the case of those fossil trees which are so frequently found in an upright position, or but little inclined to the plane of stratification. These are numerous in every coal-field, and are often traced through several layers or beds of rock. The fossil trees of Craigleith and Granton were about fifty feet in length, and lying at an angle of scarcely twenty degrees to the strata in which they were imbedded. Their passage through the solid rock, therefore, cannot be estimated at less than fifteen to twenty feet, that is, a mass of sandstone of corresponding depth must have been formed, during the comparatively short period that trees of lofty stature were able to resist the destroying action of the elements, to say nothing of the chances of currents, hurricanes, and other agents breaking them in pieces. Thisinstantia crucismay be extended to every sandstone bed of the formation, and thus serve to exercise a salutary restraint upon the mind in its imaginary conceptions of the enormous periods of time required for the accumulation of the whole series.
The carboniferous epoch was immediately succeeded by a period of great violence and of vast disturbance in the solid crust of the earth. Hence the broken inclined position of thecoal strata, and the injection of so much igneous matter, forming often ridges and hills of considerable elevation. The new red sandstone, the overlying deposits, would share in all the activity of the time. A celerity of increase, on a scale of more rapid accumulation than existing causes could produce, must consequently fall to be admitted to the rocks of this family: so much, indeed, was the plutonic agency then in force, that the rock-salt and gypseous beds are ascribed to its influence. From this period downward, the formations are all of more contracted dimensions, the basins narrowing in superficial area to the upper tertiaries, which partake of the character of local rather than of universal deposits; while the evidences here are innumerable that, until the globe settled into its present form, and assumed its present arrangement of seas, continents, and mountains, the land and water were continually changing places, the crust and framework subject to constant upheaval. The Cordilleras and Himalaya constituted, in those days, the bed of the ocean. What law of nature was not in violent activity ere they attained their sublime altitudes! How many rivers changed their courses! how many mountains were washed to their summits! how many hills melted like wax at the voice of their Creator, amidst convulsions which swept the earth so repeatedly of its living tribes, and bared as often the bosom of the great deep!
We have not, in this enumeration of the mineral strata of the earth’s crust, as yet spoken of any of the calcareous deposits. They are very numerous, some of them of prodigious thickness, and belong to the formations of every epoch. There is not one, but many, alternations of limestone connected with every such formation. Whence the source of all this material? The primary beds are not in sufficient mass to have furnished supplies for every succeeding age. The mountain limestone alone, of the middle secondary epoch, contains more calcareous matter than is to be found in the three antecedent periods. The lias, oolites, and chalks are likewise of vast thickness. The beds of the tertiary group are less considerable; but in the gypseous marls, and numerous alternating bands throughout the clays and sands of the formation, there is the clearest evidence that the stores of nature were still abundant. Nor are they yet exhausted. What suppliesin every river, sea, and ocean of the world! What countless myriads of living animals are now employed in elaborating the material! And when we again inquire, whence is it all? the answer is, that throughout all time, a wise and bountiful Providence has thereby provided the pabulum for its successive creations of organized bodies—the law of their nature is to pile up rocks—and in all the monuments of the past, we discern the style and architecture of the builders of the present. Look, then, to your still active, living, working chronometer. With what incredible swiftness do these minute creatures ply their labors! how many fathoms of coral reef will they rear in a season! When the hapless mariner returns, after a brief short interval, what hazards to run from structures which now for the first time appall him with their formidable barriers! Millions of years! Not even thousands are needed to construct islands, and to pillar the floor of the ocean, over vast expanded areas, with broad, massive, indurated rock.[13]
2.The probable duration of life in the different epochs.The geologist will tell us not to look at one but at the various families, of all kinds and of all habits, which his science has brought to light, and so many of whose remains he has disinterred from the earth. Every formation abounds with them. They flourished through every epoch. The epochs are many. The tribes which existed and perished in them are many. To allow time for the coming in and the going out, and the fulfillment of their various destinies, what an untold, incalculable amount of ages musthave elapsed! Now, give the millions of years supposed, and the wonder some may not hesitate to confess is, that there are so few, and not so many, of the former creatures of the earth which have re-appeared in our geological catalogues. The fossil regions of Great Britain, an epitome of the world, have been well explored, and the statement of fact stands nearly as follows:—Leaving out of consideration all the shelly and lime-building tribes, the numbers of the other families of animals hitherto found and described are, in the various groups of the silurian system, eight genera of only one order of fishes; in the devonian, of two orders, there are under forty genera, and not many more species of fishes, in the carboniferous, of three orders, there are about fifty genera, and a hundred species of fishes; in the permian and triassic, of three orders, there are twenty genera, and fifty species of fishes and reptiles; in the oolitic, of four orders, there are sixty genera, and two hundred and twenty species of fishes, reptiles, and mammals; in the wealden, there are, of three orders, twenty-five genera, and thirty-eight species of fishes and reptiles; in the cretaceous, of six orders, there are fifty genera, and eighty species of fishes, reptiles, and birds; in the tertiaries, of seven orders, the genera are about one hundred and fifty, and two hundred and twenty species of fishes, reptiles, birds, and mammals: thus making in all about four hundred genera, and seven hundred species of the larger families of living creatures during the whole currency of the geological epochs. The current epoch contains, exclusive of microscopic organisms, nearly two millions of species of vegetable and animal bodies existing on the terraqueous globe; and of which there are about eight thousand species of fish alone existing in our present seas.
When we take, instead of Great Britain, the whole explored geological field of the world, the result, so far as the argument is concerned, will be strengthened, not weakened. The formations of other lands are simply, with slight variations, a repetition of our own. The same genera of animals are everywhere prevalent. The specific types are likewise in many instances identical. The silurian organisms of Russia are so like those in our own island, that “no English geologist,” says Murchison, “acquainted with the organic contents of the Wenlock limestone, can view the CalymenaBlumenbachii, C. macrophthalma, C. variolaria, and other Trilobites associated with the Leptœna depressa, L. euglypha, Terebratula reticularis, and many corals most familiar to him, without at once recognizing in the upper strata the distinct representative of that British formation.” Various other fossiliferous identities are farther alluded to, when it is added—“In taking leave of Scandinavia, we must specially advert to the close relations which exist between its lower and upper silurian groups, and those of Great Britain and distant parts of the world. Of 133 silurian fossils which we brought back or noted on the spot, at least eighty-four are British, and from twenty-five to twenty-seven are North American species. In this comparison the identity of the upper silurian groups of the Baltic and Great Britain is, indeed, most surprising; for, among seventy-four Scandinavian species, upward of sixty are common to the strata of this age in both countries, and of these, fifteen to sixteen species are also found in the upper silurian rocks of America.” The devonian fossils are equally striking in their resemblances and extensive geographical distribution. Similar representatives are detected, and still more abundantly, in the carboniferous formation—universal specific types of the fauna of the epoch. One remarkable instance has been stated—upon the authority of M. L. Von Buch—that theLeptœna lata, so typical of the silurian rocks of Britain, is specifically the same with theLeptœna sarcinulata, which is no less prevalent in the Russian carboniferous strata, and continued even throughout its uppermost members. Our field of review, therefore, contains a fair proportion of the various fossils of the world, specific and generic. The formations lying before us throughout our base-line, give a true indication of the state and conditions of life during the several epochs, while in number and variety of individual forms they are above the average.
Need it then be urged, that no such incalculable cycles of ages would be required for the whole of this catalogue of animals fulfilling in their several epochs their allotted destiny upon the earth? Compared with the mass of inorganic matter in which they are entombed, their relics are literally as nothing. Only here and there, of certain classes, at remote intervals often, there is a fossil or its impression. And so entire and well-preserved arethese organisms, that we have reason to presume there has been no great obliteration, absorption, or utter waste of the races to which they belonged. On the contrary, as their distribution is so persistent in their respective formations throughout the globe,—the same genera and species being common to the four quarters of the world,—the presumption is, that specimens of nearly all the tribes that ever dwelt on the earth or swarmed in its waters have been handed down to us; and thus the number of the actual relics found becomes, as it were, a chronometer or measure of the ages during which they subsisted.
Look again at the demands of geology. Upward ofsixteen millions of years[14]are supposed to have elapsed since the creation of life upon the earth. The lowest of the rocks, in which that life has found its grave, have been reached. Their contents, upward, have been examined and catalogued. How many generations of animals must have subsisted within that period? How many individual skeletons must have been entombed and preserved, seeing that things of the filmiest texture, plants and animals, have been inclosed and handed down to us entire? Quadruple the ages of every one of the existing denizens of sea and land, and still, what countless millions of generations, succeeding each other, have lived and died during the eras that were to run? Geology presents us with her list, her whole lengthened organic roll, of scarcely four hundred generic, and less than eight hundred specific forms, gathered out of all the past cemeteries of the dead. The cemeteries themselves, of such vast walls and dimensions, may, according to the present mordant powers of the elements and the capacity of rivers for the transport of mud, have required the calculations usually assigned for their erection. But where, the question will ever recur, where is there anything like a corresponding amount of animal exuviæ apart from the calcareous supplies, to be found in the successive formations, conforming in any approximation to the existing powers and capacities of parturient nature? The fossil remains, inclosed from the beginning to the end of the inconceivable cycles of time, are the remains only of a few great families: their skeletons are admirably preserved,or their casts are minutely and accurately engraven on the rock; and do they not look as if they were theidentical individualswhich rose in the dawn and were buried in the setting of their own geological epoch!
If we go still farther into details, the results will be found startling enough. Let us select one of the periods, the old red sandstone, for illustrating our views. The period assigned for this formation embraces a term of about, we shall suppose, according to the geological distribution of time, a million or two of years. This formation consists of three great subdivisions, every one of which contains their distinct specific forms, and hence their separation into the lower, middle, and upper groups. This was pre-eminently the fish epoch—finners which roamed in undisturbed possession of every sea on the surface of the globe. Dropping into the waters, and speedily silted up in the sands, the skeletons were in the best of all possible circumstances for preservation; and accordingly, the specimens of the period constitute the wonder of the geologist, for their enameled freshness and perfect outline of figure. The productiveness of fish is prodigious, the cod-fish multiplying at the rate of three millions and a-half, mackerel at about half a million, and most of the other tribes at a corresponding high ratio. Count now how many generations, of every one of the species of the separate groups of the old red sandstone series, would exist and multiply during a period of so many hundred thousand years. The modern epoch and its breeders have scarcely reached their six thousand. When six times six have been added, and sixty times more have been added to these, they will still be a third short of the term allotted to the favored denizens of the olden time. And where, amidst the well-protected few that have yielded up their remains, are the traces of the myriads upon myriads that perished and were buried along with them? To the genus Homo, the head of creation, few think of the earth, as it now is, being the abode for periods reckoned by millions of years. Nay, within his as yet brief period, how many of his cotemporaries have already passed from the stage, extirpated, many of them, by his own direct agency? The dodo, and his fellow islander the solitaire, and other brevipennate birds,—probably, too, the elk and the urus,—certainly from this islandthe beaver, the wolf, and the bear, and just as certainly, at no distant day, the extinction of many other races will follow in the onward progress of civilization. But as now, so in all past ages, superior power, or a more dextrous instinct, have led to their extirpation. Their destiny was fulfilled, and the race perished. And as we are reasoning upon the known laws of nature, whence the geologist only seeks a footing for his vast cycles of time, so, we venture to affirm, is he bound to abide by the test of his own selection, and to read therein the terms of life granted to the families of earth. The modern epoch shows the outgoing of genera as well as of species within the limited compass of a few thousand years—gives reasonable indications of the probable extinction, speedily and at no distant period, of hundreds of others,—these families possessed, all of them, of as enduring structures, and of higher types of existence, than those of the older epochs,—and, therefore, upon every fair ground of analogy, are we justified in concluding that there can be no such diversity of ages, under one and the same system of nature, as that of hundreds of thousands of years to the living tribes of earth.
When such premises are made the grounds of such inferences, and, again, when the geologist reiterates the statement that these great periods of time correspond wonderfully with the gradual increase of animal life, and the successive creation and extinction of numberless orders of being, and with the incredible quantity of organic remains buried in the crust of the earth, we have just to remind him that betwixtgreatperiods of time, and thegradualincrease of animal life, there is no necessary connection. However long and indefinite the time connected with the rocky formations, certain it is that the successive organic tribes were created within a period that admits, and can admit, of no calculation whatever, not even of any analogical illustration from experience or the known laws of nature. The species, however numerous, of every epoch were called at once into being, not gradually but instantly, by the fiat of an all-creative act. Their multiplication and increase depended upon the law of their nature; but how long they were to be privileged to multiply, in one unvarying specific form, according to that law, is a point that comes legitimately within the range of experience and the calculations of existing life. Let notthings which differ, therefore, be mixed together. The organic and the inorganic types, in the act of formation, cannot be compared. And no argument can be adduced from the fact of the mere numbers of animal species, or of their individual increase, in support of the assumed length of any geological epoch. Species as well as individuals have perished, and gone out within the narrow limits of our own epoch, and yet have multiplied in progeny through countless myriads.
The same course of argument applies to every one of the formations, to some of them of vast thickness, even more conclusively, where we find the same species persistent throughout the group, and the same genus often extending over two or three entire formations, embracing periods of geological time of as many millions of years. Thus theLeptœna lataof the Silurian age lives on to the close of the Carboniferous; thetrilobite, earliest of living creatures, has its representatives still in our modern seas; the mail-cladholoptychiusexisted through the whole of the Devonian and Carboniferous eras; and equally remarkable is the fact that theOnchus Marchisoni, the oldest fish yet detected in the rocks of the earth, is a creature more allied to the existing genusSpinax(the dog-fish) than to any other family of relics inclosed in all the intermediate ascending series of deposits. Among the infusoria it is ascertained that there’ are two kinds of livingGallionellæidentical with the fossil species in the Richmond clays of Virginia; while again, in geological botany, we have all the types of the coal formation still flourishing with the sane gigantic forms in the continents and islands washed by the Pacific.
3.The superficial Accumulations.The argument of the geologists, for their indefinite periods of time, proceeds mainly upon the assumption that the present and the past operations of the laws of nature are nearly uniform; or, in other words, that the existing rate of increment of detrital and alluvial matter, in seas, deltas, and rivers, is to be taken as the standard throughout the various geological epochs. Tried by the test of the superficial accumulations, the subject is brought within a manageable compass, the definite is substituted for the indefinite, and the scale of accumulative power in the ancient will be in the ratio of itserosive and transporting agency in the modern epoch. The products of volcanoes also fall to be considered in estimating the effects of causes now in operation.
Thebowlder claycomes first and legitimately within the scope of this estimate; for, whatever theory of its formation be adopted, whether by the sudden submergence of a vast arctic continent and consequent upbreaking of the icy regions of the polar seas, by the sweep of a universal deluge, or a violent upheaval of the bed of the ocean, certain it is that the materials were brought together by rapid spasmodic action. This deposit covers the whole of Northern Europe, much of Asia, and extends over the vast continent of North America, as far as the 42° of latitude: it varies from a hundred to several hundred feet in depth: and thus, so far as quantity and extent of superficial area are concerned, the bowlder clay formation may be compared with any of the older rocky formations of the interior. But no geologist has ventured to speculate about an indefinite cycle of years, as the condition of the planet during the drift and accumulation of these rude and plastic materials.
Thesandsandgravelswhich succeed are likewise of great depth, spread over extensive valleys, and rise on the acclivities of hills five and six hundred feet above the level of the sea. This may be regarded, all of it, as the collect of the current epoch; and within the period of civilization and history and the arts, what sand-floods have been carried to every quarter of the globe, covering entire regions, devastating cities, and obliterating the very traces of man’s dominion over countries once subject to his use. Nor would fossils be wanting to complete the analogy, as thedunesalong the shores of every continent, and especially on the coast of the North Sea in Norway, Denmark, Holland and Belgium, only require consolidation in order to represent with living instead of extinct species, the fossiliferous deposits of anterior times; more particularly the Molasse and Nagelflue of the Swiss Alps. Near Tours, in France, there is a bed of oyster-shells which is twenty-seven miles long, with a corresponding breadth, and twenty feet thick. And in the United States there are beds far exceeding this: a stratum, nearly continuous, has been traced from the Eutaw Springs in South Carolina, to theChickasaw country—being six hundred miles in length by ten to a hundred miles in breadth.
When we descend from the land tothe seawe find equally extensive accumulations, spread over the bottom, or raised along the tide-level in the form of bars, shoals, and banks. The whole eastern coast of the United States[15]is bordered throughout by a line of sand-banks and islands, of various forms and outline, but very uniform in their mineral ingredients, being composed for the most part of a fine, white, and quartzose sand. On the coasts of the southern states, the Carolinas and Virginia, they form a chain of low islands, separated from the coast by a series of lagoons; while higher up, on the southern coasts of New England, they occur as submarine ridges, parallel to the coast, and separated from each other by wide channels. To the north, these arenaceous deposits are still more extensive, forming vast submarine plateaux, such as the St. George and Newfoundland banks. And at the bottom of all the bays and creeks of that much indented land, prodigioussiltingsare going forward, not under the form of narrow ridges, but as broad connected strata or flats; consisting seaward of very fine sand, and more inward of a coarse gravel, and in not a few instances ofcalcareous mud, where the deposit takes place in the vicinity of coral reefs. The same processes are in operation around every island and by the shores of every continent where tidal action favors the deposition of the materials—the result as now ascertained, not so much of rivers, as of oceanic currents. The depth of these sands it is impossible to determine; but thousands of feet may not reach their soundings. And as to organic remains, they are most favorably situated and composed for attracting and sustaining every kind of marine creature: it is upon the banks that border the coast of North America that the most extensive fisheries are carried on, because these are the abodes of those myriads of invertebral animals—the molluscs, annelides, and zoophytes, types of the older formations—which serve for the food of fishes, the ctenoids and cycloids of maritime enterprise. And thus, co-extensive with the littoral territories of the ocean, we have all the elements and ingredients of aformation,completing within the human epoch, that may almost rival the Old Red Sandstone itself.
Nor does the analogy terminate in the production, whether of one or many beds, of sand and gravel deposits. Simultaneously with these, there will be siltings and accumulations of various kinds of materials arranging themselves, at different depths, over the bottom of the ocean. The beds, too, will have their edges slid over each other, and where maintaining a degree of parallelism, the inclination of the more remote members of the suite will correspond with the increasing depth of the sea bottom. Then the imbedded remains will be as various as the different kinds, genera, and species of animals that frequent the different localities; nor will eruptive matter be always wanting to give diversity to the scene, indurating, dislocating, and disarranging the relative position of the deposits: Until we have formed,within our present seas, the whole complement of a geological formation—the calcareous, muddy, sandy, gravelly suites, cotemporaneous in origin and growth, with all their diversity of fossils, living and imbedded at the same period—some beds consisting entirely of microscopic or other marine bodies—some composed of vegetable and other mixed materials—some where the land and waters have mingled their spoils together—and all to be united and agglutinated into one great composite system by the dykes and eruptions of submarine volcanoes.
These processes are all now in active operation; and, without straining the argument, the clear undeniable inference is, that, as the amount of materials accumulated and arranged in the modern, so will be the ratio of increase in the more ancient periods of the earth’s history and revolutions. And hence thousands, not millions of years, would, upon such inductions, be the scale of reckoning as to time.
But to state the argument in this form is vastly to underrate the forces of nature in the primeval times. There are, on the contrary, the strongest reasons for believing that the two classes of phenomena can bear no proportion to each other, either as to the manner of or the periods occupied in their formation. The bulk of dry land, compared with water, was then, as all geological appearances testify, perhaps only a twentieth instead of a thirdpart, as now, of the supermarine area of the globe. How infinitely greater, therefore, would be the action of the waters over all the materials subject to their disintegrating power, whether upon the islands and continents already raised above their waves, or upon the immense submarine tracks of rock just lifting up their peaks and waiting to be elevated into air? Nor in alluding to volcanic products can we fail to perceive how immensely inferior are the modern to those of the palæozoic ages, when all the great mountain-ranges were bursting into position; the American continent, not as now with a few isolated eruptive centers, but rending all over, as the mighty Andes and Cordilleras were rising above the deep and assuming outline; and in every quarter of the globe the plutonic, erosive, and denuding agencies were upon a scale of corresponding magnitude. Leibnitz, in his “Protogæa,” has long ago anticipated these views, where, in the masterly sketch of his leading geological canons, he distinctly refers to the more intensive energy with which physical causes must have acted in primordial times; and considers that these disruptions of the earth’s crust, from the disturbances communicated to the incumbent waters, must have been attended with diluvial action on the largest scale. Themaximæ secutæ inundationes, thereby occasioned, had produced their natural effects, when the period of repose succeeded—thequiescentibus causis, atque aequilibratis, consistentior emergeret rerum status, as he so beautifully describes one out of many recurring stages of paroxysm and repose during the Course of Creation.
Whatever views may be adopted on this momentous question, I shall conclude by observing that it is not necessary, in support of the one here advocated, to assume that the secondary causes which have produced the geological phenomena referred to, were different in kind from those in operation at the present day. But it is asserted that such physical causes must have been immensely increased, in the degree and intensity of their action, by the very different condition of the planet, and the circumstances under which, in consequence, they began to operate. As to themillionade doctrine, if I may so term it, there are in every view the greatest difficulties in the way of its adoption,—errors of calculation somewhereto be corrected, inconsistencies to be reconciled, conditions of organic life gratuitously assumed and to be rectified. It matters not, indeed, whether we take the organic or the inorganic structures of the several periods as the gauge of their probable duration—the living tribes that existed throughout such periods, and whose relative ages we can approximate to—or the dead rock in which the remains are interred, and in the accumulation and arrangement of which so many extraordinary agencies have been demonstratively concerned. The laws of nature, in the one case, are nearly uniform; species as well as individuals have their limited terms of existence; and experience establishes the fact, that the living tribes of the modern epoch have, in several instances, become extinct within a comparatively short period of time. The operations of nature, in the other case, are subject to vast diversity, great and sudden changes, and apparently limited by no ascertained maximum of development. And thus combined, so far as our present state of knowledge extends, the inference is warrantable, that in the geological register the error may be one—ofmillionsof years’ reckoning!