60 THE POOEXESS OF OUE [Chap. X. 



deposits ; and that not a cave or true lacustrine bed is 

 known belonging to the age of our secondary or 

 palaeozoic formations. 



But the imperfection in the geological record largely 

 results from another and more important cause than 

 any of the foregoing ; namely, from the several forma- 

 tions being separated from each other by wide intervals 

 of time. This doctrine has been emphatically admitted 

 by many geologists and palaeontologists, who, like E. 

 Forbes, entirely disbelieve in the change of species. 

 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 Xortk America, and in many other parts of the 

 world. The most skilful geologist, if his attention had 

 been confined exclusively 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 peculiar 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 could 

 nowhere be ascertained. The frequent and great 

 changes in the mineralogical composition of consecutive 

 formations, generally implying great changes in the 

 geography of the surrounding lands, whence the sedi- 

 ment was derived, accord with the belief of vast inter- 

 vals of time having elapsed between each formation. 



We can, I think, see why the geological formations 



