282 GEOLOGICAL CON rEMPORANEITY ix 



the best authorities that neither similarity of 

 mineral composition, nor of physical character, 

 nor even direct continuity of stratum, are absolute 

 proofs of the synchronism of even approximated 

 sedimentary strata : while, for distant deposits, 

 there seems to be no kind of physical evidence 

 attainable of a nature competent to decide 

 whether such deposits were formed simultan- 

 eously, or whether they possess any given differ- 

 ence 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 rejDly to 

 this question — Were the British Cretaceous rocks 

 deposited at the same time as those of India, or 

 are they a million of years younger or a million of 

 3^ears 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 " Researches 

 in Theoretical Geology," published now nearly 

 thirty j^ears ago, and will carry out the arguments 

 there most luminously stated, to their logical 

 consequences, may very easily convince them- 

 selves that even absolute identity of organic 



