830 ILLOGICAL GEOLOGY. 



rian age ; and some, only before known in Lower Siluriar 

 strata, not far above the most ancient fossiliferous beds 

 Now what do these facts prove ? Clearly, they prove that 

 species which in "Wales are separated by strata more than 

 twenty thousand feet deep, and therefore seem to belong 

 to periods far more remote from each other, were really 

 coexistent. They prove that the moUusks and orinoids 

 held characteristic of early Silurian strata, and supposed to 

 have become extinct long before the mollusks and crinoids 

 of the later Silurian strata came into existence, were really 

 flourishing at the same time with these last; and that these 

 last j^ossibly date back to as early a period as the first. 

 They prove that not only the mineral characters of sedi- 

 mentary formations, but also the collections of organic 

 forms they contain, depend, to a great extent, on local cir- 

 cumstances. They prove that the fossils met with in any 

 series of strata, cannot be taken as representing anything 

 Uke the whole Flora and Fauna of the period they belong 

 to. In brief, they throw great doubt upon numerous geo- 

 logical generalizations. 



Notwithstanding facts like these, and notwithstanding 

 his avowed opinion that the test of organic remains must be 

 used " under very much the same restrictions as the test of 

 mineral composition," Sir Charles Lyell, too, bases positive 

 conclusions on this test : even where the community of 

 fossils is slight and the distance great. Having decided 

 that in various places in Europe, middle Eocene strata are 

 distinguished by nummulites ; he infers, without any other 

 assigned evidence, that wherever nummulites are found — 

 in Morocco, Algeria, Egypt, in Persia, Scinde, Cutch, East- 

 ern Bengal, and the frontiers of China — the containing for- 

 mation is middle Eocene. And from this inference he 

 draws the following important corollary : — 



* When we have once arrived at the conviction that the 



