OCR Text |
Show 270 IMPERFECTION OF THE (CHAP. IX. extensive as the land, we see them ~tudded with nlany I·S 1a n d s ,. b u t not one oceanic island I.S as yet kdn ow. nf ot o afford even a remnant of any palreo~olC or secon ~1 Y h-mation lienee we may perhaps Infer, that ~uring t e palreoz~ic and secondary periods, neither continents nor continental islands existed where ~ur oceans now extend; for had they existed there, palreozolC and secondary fornlations would in all probability have been accumulated fr01n sediment derived from their wear and tear;_ an~ would have been at least partially upheaved by the osci~lations of level, which we may fairly conclude must have Intervened _during these enormously long periods. lf then we rnay Infm: anything from these facts, we may Infer that where our oceans now extend, oceans have extended from the remot est period of which we have any record ; and on the other hand, that where continents now exist, large tr~cts ?f land have existed, subjected no _do~bt to g.reat osmllations of level since the earliest silunan penod. The coloured map 'appended to my volume on Cor~l Ree~s, led me to conclude that the great oceans are st~ll mainly area~ of subsidence, the great archipelagoes still areas ?f osmllations of level and the continents areas of elevation. But have we any' right to assume that things have thus remained from eternity? Our continents seem to have been formed by a preponderance, during many oscillations of level of the force of elevation ; but may not the areas of prep~nderant movement have changed in the lapse. of ages? At a pe:iod imn1easurably ~ntecedent to the silurian epoch, continents may have existed where oceans are now spread out; and clear and open oceans may have existed where our continents now stand. Nor should we be justified in assuming that if, for ins~ance, the b.ed of the Pacific Ocean were now converted Into a continent, we should there find formations older than the silurian strata, supposing such to have been forr;nerly deposit.ed; for it might well happen that strata wluch had subs1d~d some miles nearer to the centre of the earth, and whiCh had been pressed on by an enormous weight of superincu~bent water, might have undergone far more metamorphiC action than strata which have always remained nearer to On.AP. IX.] GEOLOGICAL RECORD. 271 the surfac~. The iJ?mense areas in some parts of the wo;ld, for Insta:l.Ce In South America, of bare metamorphiC rocks, which must have been heated under great pres~ure, have _always seemed to me to require some spe~Ial explanation; and we may perhaps believe that we see In these large areas, the many formations long anterior t~ !he silurian epoch in a completely metamorphosed condition. ?Jre ~everal difficul ~ies here discussed, namely our not findn~-~ In th~ successive formations infinitely numerous tr~nsitional hn~s between the 1nany species which now exist or have ex!sted _; the sudden manner in which whole gro?ps appear In our European formations ; the almost ent1~e absence, as at ~resent known, of fossiliferous formatwns beneath the Silurian strata, are all undoubtedly of the gravest nature. We see this in the plainest manner by the fact that all the most eminent palreontologists namely Cuvier, Owen, Agassiz, Barrande, Falconer, E: F~rbes, .&c., ~d all our greatest geologists, as Lyell, Murchi~ on, .Sedgww~, &c.,ha':"~ unanimou~ly, often vehemently, ma1nta1ne~ the Immutability of spemes. But I have rea· son to beheve that ?ne great authority, Sir Charles Lyell, fro~ further reflexion entertains grave doubts on this subJec~.. I feel how rash it is to differ from these great authorities, to whom, ·with others, we owe all our knowledge. Those who think the natural geological record in any degree perfect, and who do not attacli much weight to the fact.s and arguments of other kinds given in this volume, Will un~oubtedly at once reject my theory. For nly part, follo:v1ng out Lyell's metaphor, I look at the ~atural geological re~ord, as a history of the world imperh~ ctly kept, and Written in a changing dialect· of this Istory we possess the last volume alone relating only to two or three countries. Of this volu1n~, only here and there a short chapter has been preserved · and of each )age, only h~re and there a few lines. Each word of the : obly ch.anging language, in which the history is supposed 0 e Written, being more or less different in the inter- |