Effects of Heat inodified by Compression. 145 



bf opinion that the chemical law which forms the basis of 

 the Huttonian theory o.ughtj in the first place, to be investi- 

 gated experimentally ; all my subsequent reflections and 

 observations having tended to confirm my idea of the im- 

 portance of this pursuit, without in any degree rendering me 

 more apprehensive as to the result. 



In the arrangement of the following paper I shall first 

 confine myself to the investigation of the chemical effects, of 

 heat and compression, reserving to the concluding part the 

 application of my results to geology. I shall then appeal to 

 the volcanos, and shall endeavour to vindicate the laws of 

 action assumed in the Huttonian theory, by showing that 

 kvas, previous to their eruptions, are subjeet to similar 

 laws ; and that the volcanos, by their subterranean and 

 submarine exertions, must produce, in our times, results 

 similar to those ascribed, in that theory, to the former action 

 of fire. 



In comparing the Huttonian operations with those of the 

 volcanos, I shall avail myself of some facts, brought to 

 light in the course of the following investigations, by which 

 a precise limit is assigned to the intensity of the heatj and 

 to the force of compression, required to fulfil the condi- 

 tions of Dr. Hutton's hypothesis : for according to him the 

 power of those agents was very great, but quite indefinite} 

 it was therefore impossible to compare their supposed effects 

 in any precise manner with the phenomena of nature. 



My attention was almost exclusively confined to the car- 

 bonate of lime, about which I reasoned as follows : the 

 carbonic acid, when uncombined with any other substance, 

 exists naturally in a gaseous form at the common tempera- 

 ture of our atmosphere J but when in union with lime, its 

 volatility is repressed, in that same temperature, by the che- 

 mical force of the earthy substance which retains it in a 

 solid form. When the' temperature is raised to a full red- 

 heat, the acid acquires a volatility by which that force is 

 overcome, it escapes from the lime, and assumes its gaseous 

 form. It is evident, that were the attractive force of the 

 lime increased, or the volatility of the acid diminished by 



Vol. 24. No. 94. Afarc/M 806. K any 



