Composition y and Analogies of Rocks. 43 



experiments, so often quoted; and that strata can, in nature, losfe 

 all their indications of watery deposition, while they preserve the 

 stratified shape under a new mineral form, is Evinced by the eX- 

 rilence of siliceous schists beheuth trap, tts Already quoted. A 

 greater degree of heat and a longer continuarlce of it, are all 

 that are required to produce all the differences in these eases ; 

 and the fact, of the frequent interposition of hornblende schiM 

 between beds of gneiss, is strongly confirmatory of the cottsis- 

 teticy and tfuth of these views. Thus, also, the transition of 

 gneiss into granite becomes a phenomenon of easy solution. 



Of the General Causes of Consolidation, 



I tie*d not here terminate this view of the consolidatiort of thesfe 

 primary rocks^ by any general inquiries respecting the origin of 

 the heat or its diffusion. Nothing can be said on this subject 

 that has not been often said ; and whatever difficulties may occur 

 in attempting to apply these principles tigidly to every Case that 

 may be examined, it can only be said that this theory offers a 

 general and obvious solution of the facts ; and that if it cannot 

 be exactly fitted to meet every exigency, it is no more than must 

 happen in every similar case of a general principle, when we are 

 not in possession of all the collateral circumstances by which it 

 may have been modified. 



In thus deducing, both from the agency of heat and of watery 

 solution, the consolidation of all the stratified rocks, and in limit- 

 ing these according to the various circumstances that have been 

 ihdiicated, it must be apparent that the power granted to th6 

 former is comparatively small, and that it is not here supposed to 

 have acted beyond the range of the more ancient rocks, probably 

 not through the whole of tliese. It is very possible, never- 

 theless, that the action of heat may have been much more ex- 

 tensive. But that it has acted in the consolidation of the se- 

 condary strata at large, is rendered in the highest degree 

 impl'obable, by a variety of circumstances which I need not 

 enumerate, because they have frequently been urged against the 

 whole theory, to which the name of a par|y Jias^j been given. 



