TIIEOKIES OF WKRNEK AND 1IUTTON. 317 



epoch, there came a greatly-improved conception, which 

 ascribed them to two agencies, acting alternately during 

 successive epochs. Hutton, perceiving that sedimentary 

 deposits were still being formed at the bottom of the sea 

 from the detritus carried down by rivers ; perceiving, fur 

 ther, that the strata of which the visible surface chiefly con 

 sists, bore marks of having been similarly formed out of 

 pre-existing land ; and inferring that these strata could 

 have become land only by upheaval after their deposit ; 

 concluded that throughout an indefinite past, there had 

 been periodic convulsions, by which continents were raised, 

 with intervening eras of repose, during which such continents 

 were worn down and transformed into new marine strata, 

 fated to be in their turns elevated above the surface of the 

 ocean. And finding that igneous action, to which sundry 

 earlier geologists had ascribed basaltic rocks, was in count 

 less places a source of disturbance, he taught that from it 

 resulted these periodic convulsions. In this theory we see : 

 first, that the previously-recognized agency of water was 

 conceived to act, not as by Werner, after a manner of 

 which we have no experience, but after a manner daily dis 

 played to us ; and second, that the igneous agency, before 

 considered only as a cause of special formations, was rec 

 ognized as a universal agency, but assumed to act in an 

 unproved way. Werner s sole process, Hutton developed 

 from the catastrophic and inexplicable into the uniform and 

 explicable ; while that antagonistic second process, of 

 which he first adequately estimated the importance, was 

 regarded by him as a catastrophic one, and was not assimi 

 lated to known processes not explained. We have here 

 to note, however, that the facts collected and provisionally 

 arranged in conformity with Werner s theory, served, 

 after a time, to establish Ilutton s more rational theory 

 in so far, at least, as aqueous formations, are concerned ; 

 while the doctrine of periodic subterranean convulsions. 



