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SECTION V.

SUCCESSIVE SERIES OF ORGANIC REMAINS IN THE

DIFFERENT FORMATIONS.

THE next argument in support of the great antiquity of the earth, is the successive series of animal and vegetable remains peculiar to each of the fossiliferous strata. For it is supposed, that not only in each of the leading formations, but in many cases in each subordinate bed of such formations, peculiar kinds of organized beings have flourished for an epoch, and then disappeared, to be succeeded by a fresh creation of animal and vegetable existences. Now, it cannot be denied that such a gradation of fossil remains does exist, though extended discovery is daily making innovations on the various theories of their classification, and the deductions too hastily drawn from isolated facts. Yet we shall assume, that, generally speaking, each formation is characterized by peculiar fossils.

In considering this subject, we must leave out of view the original creation of organized

beings, as a matter utterly beyond our comprehension, and consequently without the field of our reasoning. But, looking on nature as it exists, we see no power or tendency in her works to produce organized existences from inorganic matter, neither have we any facts to shew that new species can be propagated and continued from existing organic life. On the contrary, a definite law of nature confines the production of new beings to a parent of the same species. It cannot be urged that time is necessary for the development of this phenomenon: did the law or tendency exist, it would most assuredly operate continually. Seeing, then, that there are no facts or analogies in nature to support the idea of a successive creation of species, it is unphilosophical to extend such an assumption to the past period of the earth's history.* That many species of plants and animals which once existed may have become extinct, however, is a circumstance which readily admits of illustration. Thus, partial extirpations of animals are taking place in every country as the numbers of mankind increase, and changes are brought about on the surface of the soil. The wolf, the beaver, and some kinds of deer, have entirely disappeared from Britain within the last few centuries; and the dodo is a well known example of a bird extirpated from

* Note IV.

the earth within the records of history. No doubt, many animals have thus been removed from their localities by the various changes which have taken place on the surface of the globe, and may have been either partially or totally extirpated in the revolutions which have changed the ocean into land, and levelled continents into the ocean.

Of the whole number of fossil animals yet discovered, amounting to about six thousand six hundred, the greater proportion are marine-consisting of coral zoophytes, molluscous animals, and fishes. From the sedimentary strata hitherto examined being almost exclusively marine and fluviatile, this was a circumstance which might readily have been anticipated. In the primary or lowermost series of sedimentary rocks, no organic traces can be found. It is only in the greywacke and older sandstones that they begin to make their appearance; and they do so at a distinct and definite point, evidently shewing a period of commencement of organized existence on the earth.*

* "In the grey wacke of the Cambrian mountains, there occur organic remains in the upper and middle portions, but none in the lower, though similar in all other respects. The same is the case in North and South Wales. I may state generally, as the result of my own observations on the older strata of this island, that there is a line in the descending series where organic remains seem entirely to disappear, and that this is by no means co-ordinate with mineral changes, nor produced by igneous action.” Professor SedgEWICK, in Geological Transactions.

In the first fossiliferous strata, the animal remains are of rare occurrence, and confined to a few species, consisting of crustaceous animals and fish, supposed to be the inhabitants of deep seas. In the succeeding strata, or mountain limestone, these animals disappear and are succeeded by encrinital polypi, coral zoophytes, and shell mollusca. The coal measures deposited in the hollows of the elevated limestone contain few animals, and those chiefly fluviatile, but abound in plants and large trees. Then we have the new red sandstone partially lying over the coal measures, containing very few traces of organized beings, but come again to the lias and oolitic beds, which are full of shells and animals, that have had their localities in shallow seas near the shores of continents. Over these is superimposed the chalk, a marine deposit, also containing marine shells and crustacea, and a series of tertiary strata, both fresh water and marine, terminates the whole.

Now, although each of these formations, generally speaking, contains a certain amount of distinctive species, yet there are some tribes of animals which range throughout the whole. Thus, various species of coral zoophytes are found in all the strata; terebratulæ, also, are common through the whole; ammonites extend throughout all the strata, except the tertiary; spirifers and productæ extend through all the series to the oolite; while belemnites only

appear in the lias, oolite, and chalk; and the echinæ in the chalk alone. In short, these fossil animals appear to have strictly conformed in their habits to recent species. They had certain localities which they frequented as being suited to their organization; some inhabited deep seas; some littoral situations, and others the shallow estuaries of rivers. And, when certain changes of the sea, affecting its depth, temperature, and other circumstances, occurred, the races either changed their localities, or became extirpated. Thus, when the deep and ancient bed of the greywacke system was elevated and formed a shallower sea, the inhabitants of the locality found it no longer a fit abode for them; but this revolution prepared a suitable bed for the encrinites and mollusks of the succeeding limestone deposit. This bed, too, after a certain period, suffered an elevation, and became a shallow estuary for the reception of drifted vegetables. In an adjoining bed of the ocean, certain currents were accumulating the debris of a neighbouring region, charged with numerous shell animals, and rivers flowed into these beds, where saurian reptiles formed appropriate habitats. But the question will be asked, were the species of the respective beds co-existent ? The proposition has more of analogy to support it than the alternative of separate and distinct creations. If we find a low and marshy plain, where only reeds and mosses have hitherto grown, by some means