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" of water is at once removed ; the loofe and difcontinuous body 

 " of a flratum may be clofed by means of foftnefs and com- 

 " prejpon^ the porous ftrudure of the materials may be con- 

 " folidated in a fimilar manner by the fufion of their fub- 

 " fiance, and foreign matter may be introduced into the open 

 " flrudlure of flrata, in form oi Jieam or exhalation \ confequently 

 " heat is an agent competent for the confolidation of flrata, 

 '* which water alone is not. The examination of nature gives 

 " countenance to this fuppofition ; confequently, however difficult 

 " it may appear to have this application of htat, we cannot 

 " from natural appearances fuppofe any other cat'fe." Pages 22g, 

 230, and 237. He adds " For the explanation of thofe natural 

 " appearances which are fo general, no further conditions are 

 " required, than the fuppofition of a fufficient intenfity of fire or 

 " lieat, and a fufficient degree of compreflion upon thofe bodies, 

 *' which are to be fubje<5ls to that violent heat, without 

 " calcination or change. So far as this fuppofition is not gratuitous, 

 " the appearances of nature will be thus explained." 



Here we have the whole theory of our author; in oppofition 

 to which I make bold to fay, ifl, That the fuppofition of a 

 degree of heat under any given comprefTion, ftifficient for the 

 fufion of flony fubflances in general, without calcination or 

 change, is not only gratuitous, but contrary to all that we at pre- 

 fent know of the agency of heat. Secondly, That all the appear- 

 ances of nature dcpofe in favour of an aqueous folution or 

 difFufion, and a cryflallizarion, concretion or fubfidence therefrom, 

 and againfl an igneous fulution or fufion. 



And 



