Composition, and Analogies of Rocks, 41 



shown to have been sometimes exerted throughout the felspar of 

 granite veins. 



But admitting that micaceous schist was deposited, like the 

 secondary micaceous sandstones, from water, and consolidated 

 by the same means, it presents characters which cannot be 

 explained by this process. If its flexibility has not been the 

 consequence of heat, which I have elsewhere attempted to 

 prove that it has, the peculiarities of its crystalline texture 

 and occasional contents cannot be explained, without admitting 

 that it has been exposed to a heat sufficiently intense and suf- 

 ciently durable, to permit these minerals to be formed in the 

 same manner as they are in granite and in the volcanic rocks. 

 The condition and existence of garnet, hornblende, tourmalin, 

 staurotide, and other minerals, are inexplicable by any mode of 

 watery deposition, and still less by any subsequent crystallization 

 from water. 



I need take no notice of diallage rock, or of the more ancient 

 red sandstone ; as the same processes of reasoning apply to them 

 as to those rocks to which they are analogous ; but hornblende 

 schist requires a particular consideration. This is an extremely 

 fusible compound, and its peculiar crystalline texture proves that 

 it could not have been deposited from water ; in which, indeed, 

 its earths are insoluble, and from which they could not thus have 

 been precipitated. It is, besides, precisely analogous to many 

 greenstones of the trap family ; from which, indeed, it is often 

 so little distinguishable, that it has been confounded with them, 

 by those who choose to believe in the aqueous origin of trap, under 

 the name of primitive greenstone. That it is further actually 

 produced by heat, is evinced by finding that the argillaceous 

 schists, when in contact with granite, are actually converted into 

 it. Whether simple, or compounded of hornblende and felspar, 

 the same reasoning applies to it. It is, nevertheless, admitted, 

 that its original materials have been deposited from water, and 

 thus its laminar and stratified disposition is explained. That it 

 has further consisted of clay or schist, is not only rendered pro- 

 bable by the numerous facts occurring in the trap rocks, but by 



