THEOEIES OF WERNER AND IILTTON. 317 



epoch, there came a greatly-improved conception, which 

 ascribed them to t^yo agencies, acting alternately during 

 successive epochs. Hutton, j^erceiving 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 abov^e 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 inexj)licable 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 Button's more rational theory 

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

 cvhile the doctrine of periodic subterranean convulsions, 



