THE IMPERFECTION

OF

THE GEOLOGICAL RECORD.

THE general who is for ever counter-marching and skilfully executing retrograde movements cannot always sustain the enthusiasm of his own troops, much less excite in his favour that of the civilian multitude. To many minds, the reliance placed on the imperfection of the geological record appears to be a rather damaging retreat in the strategy of science. They were just beginning to believe in geology as a wonderful revelation of the past history of the globe, when suddenly they are told that the fragments of that history which have been saved are merely tattered pages out of different chapters, giving no adequate notion of the enormous bulk and varied contents of the whole volume. Since, without the geological evidence of time's duration and of the countless changes in organic structures which that duration embraces, the theory of development could never have been imagined, it seems half ungrateful and

inconsistent in the author of the theory to turn round upon geological evidence and tax it with its extreme poverty and even delusive misleading appearances. But, in fact, Mr. Darwin in no way detracts from the value of geological evidence. The researches necessary to extend it are invested, to those who accept his theory, with tenfold interest. The deficiencies and interruptions in it which he has pointed out as necessarily occurring must sooner or later have become apparent. They were dangerous to science only as long as they were unobserved, or not sufficiently taken into account.

That the record is really imperfect is not a matter which admits of controversy. No one supposes that every species and variety that ever existed in past ages on the globe is represented at this very day by fossil specimens in prime enough condition to exhibit all the characteristics of the creature as it once lived. No one supposes that, if such specimens existed, all of them ever could or would be found by human beings. It is not in the nature of a fossil to present all the characteristics of the creature as it once lived. It cannot possibly do it; for the fossil is without life and motion. There is no respiration, no circulation of the blood going on. As a rule, only the hard parts of the creature, such as shell, scales, or bony skeleton, can be preserved. In most cases all these relies have been chemically altered. Nevertheless, in fossils from the very lowest strata, from the very earliest formations that yield any, we find certain analogies to creatures now living. We reason from these analogies without

any hesitation to the characteristics which the fossil creature will probably have presented in its living state. Our reasonings may often be erroneous, but the mere fact of our accepting the apparent analogies as a ground for reasoning at all, implies a belief in the uniformity of the conditions of animal existence between our own times and the most distant ages of the past. We argue as if generation had succeeded generation without interruption, not as if there had been new independent creations from time to time, since these would imply new conditions replacing the old, and make the argument from analogy between the items of the different creations of no value. For these independent creations, whether capricious or not in themselves, could only exhibit to our minds the symptoms of caprice. The mere fact of their being independent one of another would be so wanting in congruity with all the rest of our experience, that we should reasonably expect their minor details as well as the general plan to be wholly fantastic. In other words, the fossil memorials of life in past ages, imperfect as we confess and maintain them to be, still present so many general resemblances to one another and to living structures of the present day, that if they do not prove the continuity of life upon the globe, they cannot be held to prove anything at all; they should be regarded as a very elaborate practical joke played upon the human reason.

Palæontology is defined as the science which treats of fossil remains both animal and vegetable.' This principle of the continuity of life from age to age may

be considered as one of its definite acquisitions. There is no single point of geological time at which it can be said, 'at this epoch clearly all old species had passed away, all kinds of life had become new.' Not only is there no indication of such a break, but there is the strongest evidence against any such having ever occurred. In spite, however, of the completeness of the evidence required for proving this single conclusion, the general incompleteness and enormous deficiencies in some parts of the paleontological record can be established beyond dispute. We are in the position of a man who has kept the title-deeds to a large estate, while almost all the estate itself has been buried under the encroachments of the sea. Here and there some old landmarks may be discernible far out in the waters, showing the extent of what had once been meadow and woodland, farm and garden, but unable to show how these were distributed, or to exhibit any of their details.

Mr. Parfitt, in his paper on Fossil Sponge Spicules,' told the Devonshire Association last year (1870) that we have evidence more or less exact of sponges in a fossil state as far back in time as the Silurian system, mentioning specimens of Acanthospongia Siluriensis, Cliona antiqua, and Cliona prisca, and stating in regard to the two latter that the genus is still in our own seas. He then referred to large masses of a fossil in the Devonian rocks of Cornwall, believed by some to be sponges, and by others to be the remains of fish. That these are in reality fish-remains has, in fact, been shown

pretty conclusively1. From this point, however, up to the Great Oolite, Mr. Parfitt tells us that scarcely a vestige of the sponges is to be found, although since that time they have been very abundant. Between the Silurian and the Great Oolite the interval of time must have been enormous. It is occupied by a vast series of sedimentary rocks, embracing very varied mineral characteristics. From this series our museums have been, and are still being, supplied with vast heaps of fossil organic structures, including among numerous others, plants and corals and fish and reptiles. Through all that protracted period there is no reason to suppose, in regard to the outer rind of the globe, that the general conditions of earth, air, and water were other than they are now. All England may have been under water; delicate creatures may have wintered at the North Pole for the sake of its genial climate; and an infinity of other local and temporary differences may have prevailed, without making the habitable globe of those days essentially different from our own. The laws of chemistry and mechanics, the laws of heat and motion, must have been just the same as they are now. Then, as now, there must have been oceans and continents, winds and currents, forests growing, decaying, and being buried, sand and chalk being deposited in layers, molten minerals thrown up by volcanoes, ice forming at a

1 See Mr. Pengelly's paper on the subject in the Transactions of the Devonshire Association for 1868.