BV COMPRESSION. ^33 



ftbm being convinced by thefe arguments ; for, without beihjr 

 able to prove that any artificial compreffion to which we could 

 expofe the carbonate, would, efiediially prevent its calcina- 

 tion in our fires, I maintained, that we had as little proof of 

 the contrary, and that the application of a moderate force 

 might poffibly perform all that was hypothetically afliimed in 

 the Huttonian theory. On the other hand, I confidered 

 myfelf as bound, in practice, to pay deference to his opinion, 

 in a field which he had already fo nobly occupied ; and ab» 

 flained, during the remainder of his life, from the profe- 

 cution of fome experiments with compreffion, which I had 

 begun in 1790. 



In 1798, I refumed the fubjed with eagerncfs, being ftill of Experiments! 



opinion that the chemical law which forms the bafis of the '"**^'2^''"'* 

 TT -I . . 1 - /- I in- « undertaken. 



Huttonian theory, ought, in the hrft place, to be inveltigated 



experimentally j all my fubfequent reflections and obferva- 

 tions having tended to confirm my idea of the importance 

 of this purfuit, without in any degree rendering me more ap- 

 prehenfive as to the refult. 



- In the arrangement of the following paper, I (liall firfi con- Order of tie 

 fine myfelf to the inveftigation of the chemical efTefts of heat preient trcatifc, 

 and compreffion, referving to the concluding part the appli- 

 cation of my refults to Geology. 1 ffiall then appeal to the 

 volcanoes, and ftiall endeavour to vindicate the laws of a<5iion 

 affiiraed in the Huttonian theory, by fliewing, (hat lavas, 

 previous to their eruptions, are (libjeft to fimilarlaws; and 

 that the volcanoes, by their fubterranean and fubmarine exer- 

 tions, mud produce, in our times, refults fimilar to thofeafcri- 

 bed, in that theory, to the former action of fire. 



In comparing the Huttonian operations with thofe of the 

 volcanoes, I (hall avail myfelf of fome fads, brought to light 

 in ihe courfeof the following inveftigations, by which a precife 

 limit is affigned to the intenfity of the heat, and to the force 

 of compreffion, required to fulfil the conditions of Dr. Hutton's 

 hypolbefis : For, according to him, the power of thofe agents 

 was very great, but quite indefinite; it was therefore im» 

 poffible to compare their fuppofed eftefis in any precife mapner 

 with the phenomena of nature. 



My attention was almoft exclufively confined to the carbo- Argument re- 

 nate of lime, about which 1 reafoned as follows : The carbonic t^o^naf" ofTimc. 

 *cid, when uncombined with any other fubftance, exifis natu- 

 6 rally 



