210 ^tag jforrnmw, (Siasajjs, mtir gtbufas. [x. 



able of a nature competent to decide whether such 

 deposits were formed simultaneously, or whether they 

 possess any given difference of antiquity. To return 

 to an example already given. All competent authorities 

 will probably assent to the proposition that physical 

 geology does not enable us in any way to reply to 

 this question Were the British Cretaceous rocks depo- 

 sited at the same time as those of India, or are they a 

 million of years younger or a million of years older ? 



Is palaeontology able to . succeed where physical 

 geology fails ? Standard writers on palaeontology, as 

 has been seen, assume that she can. They take it for 

 granted, that deposits containing similar organic remains 

 are synchronous- at. any rate in a broad sense; and 

 yet, those who will study the eleventh and twelfth 

 chapters of Sir Henry De la Beche's remarkable "Ke- 

 searches in. Theoretical Geology," published now nearly 

 thirty years ago, and will carry out the arguments 

 there most luminously stated, to their logical conse- 

 qences, may very easily convince themselves that 

 even absolute identity of organic contents is no proof 

 of the synchrony of deposits, while absolute diversity 

 is no proof of difference of date. Sir Henry De la 

 Beche goes even further, and adduces conclusive evidence 

 to show that the different parts of one and the same 

 stratum, having a similar composition throughout, con- 

 taining the same organic remains, and having similar 

 beds above and below it, may yet differ to any con- 

 ceivable extent in age. 



Edward Forbes was in the habit of asserting that 

 the similarity of the organic contents of distant forma- 

 tions was primd facie evidence, not of their similarity, 

 but of their difference of age ; and holding as he did 

 the doctrine of single specific centres, the conclusion 

 was as legitimate as any other; for the two districts 



