Considerations on Volcanoes. 371 



occasioned by the friction of the crystalline particles on one 

 another, may have sometimes reduced the granite to a porphyry, 

 and so on." 



And thus having disposed of the crystalline rocks, we proceed 

 to the strata and their origin. Here we are in the same dilemma 

 as before, on the subject of abridgment. If we refer the readers 

 to the book, the author will receive the credit which he deserves 

 for a theory of strata, as of unstratified rocks, which is doubtless 

 his own discovery, deduced from his prior reasonings on volcanoes, 

 because he has not borrowed it from prior authors on the same 

 subjects, and arguing highly in favour of his ingenuity. Where- 

 as, if we attempt an analysis of it, we fear by using language of 

 that ordinary kind to which our ears have been so much accus- 

 tomed, it might lead to the supposition that there was really 

 no novelty in the views, either of this or the preceding chapter; 

 which would be an injustice, since the originality of the views 

 cannot be questioned, when the author announces " a few theore- 

 tical opinions naturally suggested by the phenomena he has been 

 investigating ;" as we just remarked. 



However, we must attempt it. Whenever a portion of the 

 globe was elevated by the intumescence of the crystalline rocks, 

 the waters raised by them must have possessed an abrasive force, 

 wearing away the surface and depositing the detritus at a lower 

 level. " But this is not all ; for by the absolute elevation of such 

 a mass, the radius of the globe is dilated at this point," and a 

 proportionate body of water flowing to the opposite extremity, to 

 restore the equilibrium, produces an " antipodal tide" and " oscil- 

 latory movements." And these waves will wear away the rocks 

 also: and thus denudations were produced; and thus great frag- 

 ments will have been left in the longitudinal valleys, while the 

 finer detritus would be carried further on. And as the finest 

 sedimental deposits subsided, bituminous, vegetable, animal, and 

 other substances would subside also, and concretionary attraction 

 would divide them into strata, and so on. 



" The water of the ocean has two sources," land springs and 

 rain ; which last, also, has two sources, the one in common eva- 

 poration, and the other in volcanic vapours. And these carried 

 into the ocean, originally, mineral matters ; while pressure, the 

 heat of the ocean, and all the other circumstances, discovered by 

 the author, which we cannot detail, will assist in accounting for 

 the consolidation of strata, and so forth. And the author is " of 

 opinion" that the primitive ocean, " locally supersaturated with 

 silex or carbonate of lime, was sufficient, with the aid of con- 

 solidation and pressure, to explain the formation of crystalline 

 rocks of these two characters. Mica was sedimental or crystal- 

 lized in such rocks as mica slate ; and asbestos, epidote, and 



