424 NATURAL SCIENCE. a^.^^^t. 



cult, if not impossible, to suppose that they have ever changed places 

 with the great oceans. It is, that on ;dl the present continents 

 we find either the same or a closely parallel series of geological 

 formations, from the most ancient to the most recent. Not only do 

 we find Palaeozoic, Mesozoic, and Caniozoic rocks everywhere present, 

 but, in proportion as the continents are explored geologically, we find 

 a tolerably complete series of the chief formations. From Laurentian 

 to Carboniferous and Permian, from Trias to Cretaceous, and from 

 Eocene to Quaternary, the geological series appears to be fairly 

 represented not only in continents, but also to a considerable extent 

 in the large continental islands, such as Great Britain and New 

 Zealand. 



Now this is certainly not what we should expect if the present 

 continental areas had, at different epochs, risen out of the deep 

 oceans. In that case some would have commenced their geological 

 history at a later period than others, having either a late Palaeozoic 

 or some Mesozoic formation, or even an early Tertiary for their 

 lowest stratified rock. Others, which had become oceanic for the 

 first time at a later epoch, would exhibit an enormous gap in the 

 series, either several of the Mesozoic formations, for example, being 

 absent, or some considerable portion of both Palaeozoic and Mesozoic, 

 or Mesozoic and Tertiary. This would necessarily be the case, 

 because we cannot believe that so vast a change as the subsidence of 

 an entire continent till its site became a deep ocean, and its subse- 

 quent elevation till it again became dry land, could possibly be effected 

 in any less extended periods, if at all. 



Whenever such gaps, or smaller ones, now occur locally, they 

 are generally held to imply the existence of terrestrial conditions, as 

 in the case of China, which, according to Richthoven, has been con- 

 tinental since the Carboniferous epoch. In many cases there is 

 distinct evidence of such conditions in lacustrine or freshwater 

 deposits, dirt-beds, &c. But if a gap of such vast extent both in 

 space and time as that here referred to were caused by the 

 interchange of a continent and a deep ocean, the fact that it 

 was so produced would be clearly evidenced by an almost 

 uniform deposit either of organic or clayey ooze, similar to 

 those now everywhere forming over the oceanic area. Even if 

 we make the fullest allowance for denudation during eleva- 

 tion, sufficient indications of so widespread a formation should be 

 detected. Such a deposit would, in fact, have every chance of being 

 largely preserved, because, long before it rose to the level where it 

 would be subject to denudation by waves or currents, it would, almost 

 everywhere, be overlain by a series of shore deposits, and wherever 

 these latter were preserved on the land surface the oceanic formation 

 would necessarily be found under them. That no such enormous 

 deficiency in the geological series characterises any of the continents, 

 and that no widespread deposit of organic or clayey ooze at some 



