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Show 37 DARWINISM CHAP. . , 300 paces lona by 60 paces broa.d, many of found m a p,tce 0 ·t· . . . a . enormous quanti Ies. the pecte. ex1 ~111 o 1. 11 belonrr to the Upper Miocene formaThe Pikermi fo S1ls. h do 't of Upper Eocene aae ha . ally nc eposi l\1 twn, b_ut an. eq~ S h-vVe tern France at Quercy, where H • heen d1 covered m out of no les than forty-two Filhol has determined the p{esenceEqually remarkable are the Pecies of bea t of prey a onel.. f ·1 1· n North Am rica . . . . f mamma Ian os 1 vanous dis_covenes o 1 k b ttoms now forming what arc c pecially ;,'~. ~~a~ci~" ~f 'ba~ota and Nebraska, belonging to called _the <t • . Here are found an enormous a em_blao·c the 1IO~enc penod. ·f t skeletons, of herbivora and carmvorn, of remams, oft~n per e~ those from the localitie already a Yaried and mtercstmg as l th 1' ti'nct ·mel far ex- . E . . but a toae er c t ' ' ' · referred to m mopde > •• t f~l)ecies of the larger animal::., d. a · number an vane Yo . . cee m:;,, m . . f f North America. Very m1t 1<U ' the whole eX1Sti~~ s~~~~ ~merica anll in An. tralia, l~allin_g phenomena, occulr I~ that the earth at the pre ent tnnc 1. us to the cone uswn · 1 d that at ach . h 1 . cr ·ds the laraer amma ' an ' impoven ec as 1 oar . t' o e at all events it contain d uccessive period of Tertmry • :m 'h' ' · h~bit it Tlw . t . nnmb r of species t an now m . . . a far ~rea ei b dance of the remain which we find :·cry. r~chness. and s:r~~1 to convince u::. how imperfect <UHl m hmited area ' k 1 d e of the earth £anna at • 1 t be our now e g ' fragmentary rot . since we cannot believe that all or any one pa t epoch> . · h b. 1 eli tri ·t ,,·ere . ·1 ll of the animals whiCh m a. 1tec any . :~:~I~b:d' in a, single lake, or overwhelmed by the flood of a. ingle river. . h 1 't ur ar , t'X But the spots where such nc c epo 1 0 . . ' .. ·,t dina} few and far between "·hen compared "tth the 7:1·.' ~~:a ~£ ~ontinent-'ll land, and we have efvery .rea oni etcoi_e1 c~~~~·~ fibers o cunou th·tt 1· 11 p·t t aae as now, nu . . . .. ,. . l c' ·ll thoe ·' ommoner and more a b un d an t p. c1e ,.IYIIW~ 1 ,u e or o ' , . . · cr ri of am mal form,... a ,·ery impe~·fcct Idea, of th~ ex.tn~nthe imperfection of onr ret more Important, as S OWl " . . h ,; \'t' l"\ ] knowledcr ' is the enormous laps:) ox tlm~ b~t\\ een t c , . .', formati·o ne s m· w h'IC h " , 0 find orcrani " r mam many ahnmb nce, e< · , v . . t that in many cases we find our el es. almo. t m Cl. nlel woo rvlad all the species and mo t of t h e g nera of the hw 1er o anim~l . having undergone a complete chaug;e. xnr THE GEOLOGICAL EVIDENCES O.F EVOLUTION 371} Cau.ses of the Impe1jection of the Geological Record. These facts are quite in accordance with the conclusions of geologists as to the necessary imperfection of the geological record, since it requires the concurrence of a number of favourable conditions to preserve any adequate representation of the life of a given epoch. In the first place, tho animals to be preserved must not die a natural death by disease, or olcl age, or by being the prey of other animals, hut must bo destroyed by some accident which shall lead to their 1 cin:i embedded in the soil. They must be either carried away hy floods, sink into bogs or; quicksands, or be enveloped in the mud or ashes of a volcanic eruption; ancl when thus cmbc<lcled they mn t remain undisturbed amid all the future changes of the earth's surface. But the chances against this are enormous, because denudation is always going on, and the rocks we now find at the earth's surface arc only a small fragment of those whicb were originally laid down. The alternations of marine and freshwater deposits, and the frequent unconformability of strata with those which overlie them, tell us plainly of repeated elevations and depres ions of the surface, and of denudation on an enormous scale. Almost every mountain range, with its peaks, ridge , and valleys, is but the remnant of some vast plateau eaten away by sub-aerial agencies; every range of sea-cliffs tell us of long slopes of Janel d stroyetl by the waves; while almost all the older rocks which now form the surface of the earth have been once covered \vith newer deposits which have long since disappeared. Nowhere are the evidences of this denudation more apparent than in North and South America, where granitic or metamorphic rocks cover an area hardly less than that of all Europe. The same rocks are largely developed in Central Africa and Eastem Asia ; while, be. ides those portions that appear exposed on the surface, areas of unknown extent are buried under strata which rest on them uncomformably, and could not, therefore, constitute the original capping under which the whole of these rocks must once have been deeply buried; because granite can only be formed, and metamorphism can only go on, deep down in the ernst of the earth. 'Vhat an over- |
