Physical Structure and older stratified Deposits of Devonshire. 701 



ther changeSj if supported by the evidence of fact or rational analogy. What 

 difficulty is there in believing that a marine formation should,, in one part of 

 the world, have gone forward so tranquilly as to allow all the ordinary opera- 

 tions of animal life ; while, in another part, the deposits of the ocean were in- 

 terrupted or modified by rude mechanical movements, incompatible with the 

 existence of organized beings? We see no difficulty whatsoever in the mi- 

 neral structure of what we now regard as the old red sandstone of Devon- 

 shire and Cornwall. The classification we adopt is derived from its own 

 appropriate evidence; and it at the same time removes the greatest difficulties 

 presented by the unexplained phenomena of our older formations ; gives a 

 natural sequence and meaning to their history ; and, we may add, gives a 

 symmetry to the disposition of the colours on our geological maps, which they 

 never had before. 



The strongest proofs are given in this and our previous paper, of the insuffi- 

 ciency of mineral character, taken alone, to determine the epoch of any doubtful 

 formation : and as the term gray-wacke has done much disservice to geology, 

 by inducing observers to merge, under one unmeaning name, deposits be- 

 longing to distinct periods in the history of the earth, we venture to hope that 

 the word may henceforth be discarded as a term of classification. Used for 

 the mere purpose of mineral description, we can of course make no similar 

 objections to it, 



4. Lastly, we may remark, that in all the descriptions, both of this and our 

 previous paper, we have, for obvious reasons, drawn our analogies from the 

 nearest formations of our own island. But we cannot forbear expressing our 

 belief, that the series of rocks of Devonshire and Cornwall, above described, 

 may serve to clear up some of the difficulties in the classification of the older 

 formations of the continent of Europe, where the old red sandstone has 

 seldom been found, at least in what has been hitherto regarded as the ordinary 

 British type. But now that the old red sandstone has been exhibited in such 

 a different form, on such a vast scale, and with its own series of organic 

 remains, we have little doubt that its true equivalents will be found distributed 

 through various parts of Europe. To obtain, as far as possible, satisfaction 

 on some of these points, is the first task we propose to ourselves during the 

 investigations of the approaching summer. 



Though the term old red sandstone, when designating great groups of 

 rocks like the Cornish killas and Devonian slates, should involve no error of 

 classification, still it would, mineralogically, be most inappropriate. We pur- 

 pose therefore, for the future, to designate these groups collectively by the 

 name Devonian system^ as involving no hypothesis, and being agreeable to 



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