360 



THE GEOLOGIST. 



most eminent -winters on this subject have fallen into this mistake. 

 It almost appeal's as if they had forgotten that the expression vein 

 onlv disting-uishes the/or;/? of an occmTence, by no means its nafior; 

 and that paii:icnlar species of ores (native metals, sulpliides of 

 metals, oxides and hydrates) are found in veins with very varied 

 combinations, and under very diverse cu'cumstances. 



Another mistake of eai^ly geologists was that they were always 

 prone to consider geological events as caused by a Avholly peculiar 

 state of tilings belonging to an anterior world concluded with the 

 appearance of man. This doctiiiie was but too favoui^able to the 

 growth of the most unsound and gi^oundless hypotheses. Nothing 

 was at that time impossible in the eyes of geologists ; they had no 

 regard to the analogies of existing causes ; scarcely much indeed for 

 the essential laws of natui'e. It w^as chiefly Sii' Charles Lyell ^\llo 

 successfully combated this doctrme. He showed that the magni- 

 ficence of the result was extraordinaiily heightened by the per- 

 manency of the causation ; and that we had not necessarily to assume 

 new sets of causes, different from those now in action, m order to 

 account for the earth's sm'face as we now see it. According to this 

 geologist, existing causes acting thi'ough periods of unlimited dm'a- 

 tion are sufficient to explain all geological phenomena. But he and 

 his school have e\ddently caiTied this doctrine to an extreme, since 

 he insists that there exists no recogTiizable proofs of any progi'essive 

 development in the state of our earth, only a constant metamor- 

 phism ; while an immense mass of facts affords veiy strong evidence 

 of a progressive development of the eai'th, arising from its continued 

 gradual cooling. Of these, I shall here merely point to the very 

 remarkable differences in composition and structure that exists be- 

 tween the older and newer eruptive rocks, and to the succession of 

 the various types of organic life recognized by fossil remains. This 

 succession most undoubtedly leads, by its convergence, to a vanish- 

 ing point, when as yet there existed no organic life on the earth. 



The acceptance of the doctrine of a gradual development of the 

 earth by slow cooling is supported by many facts, and suffices to 

 explain the totality of geological phenomena and the general forma- 

 tion of the solid crust of the earth, although isolated cases of 

 obscurity still remain. 



