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Show 288 IMPERFECTION OF THE CHAP. IX. . rt t discoveries made every sufficient care, as the Impo an · rholly soft can be ear in Europe prove. No organism " . y d Sh 11 d bones will decay and disappear Preserve . e s an di t · when left on t h e b 0 tto m of the sea ' wher· e se1 1 mekn ' IS not accumu1 a tm. g. I believe we are ·c ontindu a •ty tt a Ing a most erroneous vi.e w, when we ta. citly a mi o1 ouhr - 1 th t ediment is being deposited over ncar y t e se ves a s · 1 · k t whole bed of the sea, at a rate . suffiment y quiC o embed and preserve fossil remams. Throughout. an enormously large proportion of .the oc~an, the bnght blue tint of the water bespea~s Its punty. The many cases on re Cord Of a formation c. onformably cov. eredd, after an enormous interval of time, by another ~n later formation, without the underlying bed having suffered in the interval any wear and tear, seem explicable only on the view of the bottom of ~~e sea not rarely lying for ages in an unaltered condition . . The remains which do become embedded, if in sand or. gravel, will when the beds are upraised generally be dissolved by the percolation of rain-wate:. I. suspect that but fe~ of the very many animals which hve on the beach ~e tween high and low watermark are preserve~. For Instance the several species of the Chthamahnre (a subfamil; of sessile cirri pedes) coat the rocks .all ov.er the ld in infinite numbers : they are all stnctly htto~al, wwoitrh the exception of a single Me di terranean sp em. e:s· ' which inhabits deep water and has been fo~nd fossil I: Sicily whereas not one other species has hitherto bee found ' in any tertiary formati. on: yet I· t .I·s now kncohwalnk that the genus Chthan1alus existed dunng the . period. The molluscan genus Chiton offers a partia1 1 y analogous case. · hich With respect to the terrestrial productiOns w .. ljved durino· the Secondary and Palreozoic periods,~ It I~l superfluouso to state that our evi· a ence f ro m 10SSI CHAP. IX. GEOLOGICAL RECORD. 289 remains is fragmentary in an extreme degree. For instance, not a land shell is known belonging to either of these vast periods, with one exception discovered by Sir C. Lyell in the carboniferous strata of North America. In regard to mammiferous remains, a single glance at the historical table published in the Supplement to Lyell's Manual, will bring home the truth, how accidental and rare is their preservation, far better than pages of detail. Nor is their rarity surprising, when we remember how large a proportion of the bones of tertiary man1mals have been discovered either in caves or in lacustrine deposits ; and that not a cave or true lacustrine bed is known belonging to the age of our secondary or palreozoic formations. But the imperfection in the geological record mainly results from another and more important cause than any of the foregoing ; namely, from the several formations being separated from each other by wide intervals of time. When we see the formations tabulated in written works, or when we follow them in nature, it is difficult to avoid believing that they are closely consecutive. But we know, for instance, from Sir R. Murchison's great work on Russia, what wide gaps there are in that country between the superimposed formations ; so it is in North America, and in many other parts of the world. The most skilful geologist, if his attention had been exclusively confined to these large territories, would never have suspected that during the periods which were blank and barren in his own country, great piles of sediment, charged with new and peculia:~;" forms of life, had elsewhere been accumulated. And if in each separate territory, hardly any idea can be formed of the length of time which has elapsed between the consecutive formations, we may infer that this ~ould nowhere be ascertained. The frequent 0 |
