LECTURE FIFTH.

GEOLOGY IN ITS BEARINGS ON THE TWO THEOLOGIES.

PART I,

THE science of the geologist seems destined to exert a marked influence on that of the natural theologian. For not only does it greatly add to the materials on which the natural theologian founds his deductions, by adding to the organisms, plant and animal, of the present creation the extinct organisms of the creations of the past, with all their extraordinary display of adaptation and design; but it affords him, besides, materials peculiar to itself, in the history which it furnishes both of the appearance of these organisms in time, and of the wonderful order in which they were chronologically arranged. Not only-to borrow from Paley's illustration does it enable him to argue on the old grounds, from the contrivance exhibited in the watch found on the moor, that the watch could not have lain upon the moor forever; but it establishes further, on different and more direct evidence, that there was a time when absolutely the watch was not there; nay, further, so to speak, that there was a previous time in which no watches existed at all, but only water clocks; yet, further, that there was a time in which there were not even water clocks, but only sundials; and further, an earlier time still in which sundials were not, nor any measurers of time of any kind. And this is distinct ground from that urged by Paley. For, besides holding that each of these contrivances

must have had in turn an originator or contriver, it adds historic fact to philosophic inference. Geology takes up the master volume of the greatest of the natural theologians, and, after scanning its many apt instances of palpable design, drawn from the mechanism of existing plants and animals, authoritatively decides that not one of these plants. or animals had begun to be in the times of the Chalk; nay, that they all date their origin from a period posterior to that of the Eocene. And the fact is, of course, corroborative of the inference. "That well constructed edifice," says the natural theologian, "cannot be a mere lusus naturæ, or chance combination of stones and wood; it must have been erected by a builder." "Yes," remarks the geologist, "it was erected some time during the last nine years. I passed the way ten years ago, and saw only a blank space where it now stands." Nor does the established fact of an absolute beginning of organic being seem more pregnant with important consequences to the science of the natural theologian than the fact of the peculiar order in which they begin to be.

The importance of the now demonstrated fact, that all the living organisms which exist on earth had a beginning, and that a time was when they were not, will be best appreciated by those who know how much, and, it must be added, how unsuccessfully, writers on the evidences have labored to convict of an absurdity, on this special head, the atheistic assertors of an infinite series of beings. Even Robert Hall (in his famous Sermon on Modern Infidelity) could but play, when he attempted grappling with the subject, upon the words time and eternity, and strangely argue, that as each member of an infinite series must have begun in time, while the succession itself was eternal, it was palpably absurd to ask us to believe in a succession of beings that was thus infinitely earlier than

any of the beings themselves which composed the succession. And Bentley, more perversely ingenious still, could assert, that as each of the individuals in an infinite series must have consisted of many parts, that as each man in such a series, for instance, must have had ten fingers and ten toes, — it was palpably absurd to ask us to believe in an infinity which thus comprised many infinities, — ten infinities of fingers, for example, and ten infinities of toes. The infidels had the better in this part of the argument. It was surely easy enough to show against the great preacher, on the one hand, that time in such a question is but a mere word that means simply a certain limited or definite period which had a beginning, whereas eternity means an unlimited and undefinable period which had no beginning; that his seeming argument was no argument, but merely a sort of verbal play on this difference of signification in the words; - further, that man could conceive of an infinite series, whether extended in infinite space, or subsisting in infinite time, just as well as he could conceive of any other infinity, and in the same way; and that the only mode of disproving the possibility of such a series would be to show, what of course cannot be shown, that in conceiving of it in the progressive mode in which, according to Locke, man can alone conceive of the infinite or the eternal, there would be a point reached at which it would be impossible for him to go on adding millions on millions to the previous sum. The symbolic" ad infinitum" could be made as adequately representative in the case of an infinite series of men or animals in unlimited time, as of an infinite series of feet or inches in unlimited space, or of an infinite series of hours or minutes in the past eternity. And as for Bentley, on the other hand, he ought surely to have known that all infinities are not equal, seeing that Newton had expressly told him so in the second of his

four famous letters; but that, on the contrary, one infinity may be not only ten times greater than another infinity, but even infinitely greater than another infinity; and that so the conception of an infinity of men possessed of ten infinities of fingers and toes is in no respect an absurdity. Of the three infinities possible in space, the second is infinitely greater than the first, and the third infinitely greater than the second. A line infinitely produced is capable of being divided into that is, consists of-an infinity of given parts; a plane infinitely extended is capable of being divided into an infinity of infinitely divisible lines; and a cube, that is, a solid, infinitely expanded, is capable of being divided into an infinity of infinitely divisible planes. In fine, metaphysic theology furnishes no argument against the infinite series of the atheist. But geology does. Every plant and animal that now lives upon earth began to be during the great Tertiary period, and had no place among the plants and animals of the great Secondary division. We can trace several of our existing quadrupeds, such as the badger, the hare, the fox, the red deer, and the wild cat, up till the earlier times of the Pleistocene; and not a few of our existing shells, such as the great pecten, the edible oyster, the whelk, and the Pelican's-foot shell, up till the greatly earlier times of the Coraline Crag. But at certain definite lines in the deposits of the past, representative of certain points in the course of time, the existing mammals and molluscs cease to appear, and we find their places occupied by other mammals and molluscs. Even such of our British shells as seem to have enjoyed as species the longest term of life cannot be traced beyond the times of the Pliocene deposits. We detect their remains in a perfect state of keeping in almost every shell-bearing bed, till we reach the Red and Coraline Crags, where we find them for the last time; and,

on passing into older and deeper lying beds, we see their places taken by other shells, of species altogether distinct. The very common shell Purpura lapillus, for instance, is found in our raised beaches, in our Clyde beds, in our boulder clays and mammaliferous crags, and, finally, in the Red Crag, beyond which it fails to appear. And such also is the history of the common edible mussel and common periwinkle; whereas the common edible cockle, and common edible pecten (P. opercularis) occur not only in all these successive beds, but in the Coral Crag also. They are older by a whole deposit than their present contemporaries, the mussel and periwinkle; and these, in turn, seem of older standing than shells such as Murex erinaceus, that has not been traced beyond the times of the mammaliferous crag, or than shells such as Scrobicularia piperata, that has not been detected in more ancient deposits than raised sea beaches of the later periods, and the elevated bottoms of old estuaries and lagoons. We thus know, that in certain periods, nearer or more remote, all our existing molluscs began to exist, and that they had no existence during the previous periods; which were, however, richer in animals of the same great molluscan group than the present time. Our British group of recent marine shells. falls somewhat short of four hundred species;* whereas the group characteristic of the older Miocene deposits, largely developed in those districts of France which border on the Bay of Biscay, and more sparingly in the south of England, near Yarmouth, comprises more than six hundred species. Nearly an equal number of still older shells have been detected in a single deposit of the Paris

* Forbes and Hanley enumerate one hundred and sixty bivalves, and two hundred and thirty-two univalves,-in all three hundred and ninetytwo species, as the only known shell-bearing molluscs of the existing British seas.