Bi' COMPRESSTOH. ggj 



difcovery of carbonic acid, explained the chemical nature of 

 the carbonate, no rational theory could be formed, of the che- 

 mical revolutions which it has unvioubtedly undergone. 



This difcovery was, in the firft inftance, hoftile to the fup- feems not pro- 

 pofed action of fire ; for tlie decompofilion of limeftone by fire "^' ^ y *" ' 

 in every common ki!n being thus proved, it feemed abfurd to 

 afcribe to that fame agent the formation of limeftone, or of 

 any mafs containing it. 



The contemplation of this difficulty led Dr. HuKon to view Dr. Hutton'i 

 the action of Mre in a manner peculiar to himfelf, and thus to ''^J'* 

 form a geological theory, by which, in my opinion, he has fur- 

 nifhed the world with the true folution of one of the moft inte- 

 refting prpblems that has ever engaged the attention of men of 

 fcience. 



He fuppofed, 



I. That heat has afted, at fome remote period, on all That rocks have 

 j-Qcks undergone heat 



under ftrong 



II. That during the a6lion of heat, all (hefe rocks (even preflure. 



fuch as now appear at the furface) lay covered by a fuperin- 

 cumbent tnafs, of great weight and ftrength. 



III. That in confequence of the combined aflion of heat 

 and preflTure, effects were produced different from thofeof heal 

 on common occafions ; in particular, that the carbonate of 

 lime was reduced to a ftate of fufion, more or lefs complete, 

 without any calcinalion. 



Theelfential and charadterifiic principle of his theory is thus 

 comprifed in the word comprefion; and by one bold hypothefis, 

 founded on this principle, he undertook to meet all the objec- 

 tions to the a6tion of fire, and to account for thofe circum- 

 flances in which minerals are found to differ from the ufual 

 products of our furnaces. 



This fyftem, however, involves fomany fuppofitions, appa- singular con^ 

 rently in contradiction to common experience, which meet us trail of the per- 

 on the very threOioId, that moft men have hitherto been de- ^'^JJ.'^^y,°^^^^_* 

 terred from the inveftigalion of its principles, and only a few verfation, and 

 individuals have juftly appredated its merits, Jf was long |J?^ ^'^^f ""^^ 

 before I belonged to the latter clafs; for I muft own, that, on 

 reading Dr. Hutton's firft geological publication, I was in- 

 duced to rejeft his fyfteni entirely, and fliould probably have 

 continued ftill to do lb, with the great majority of the world, 

 but for my habits of iHtimacy v^ilh the author; the vivacity 



and 



