( 35:^ ) 



them but by an indired way, that is, by 

 obferving the gafeous fubftances which 

 arife from volcanos when they have return- 

 ed to a ftate of tranquillity. If we perufc 

 the works of writers on this fubjedt, we 

 fhall find feveral of them named ; fuch as 

 hydrogenous gas, fulphurated hydrogenous 

 gas, carbonic acid gas, lulphureous acid gas, 

 azotic gas, &c. thefe different gafes having 

 been found in volcanic countries *, 



But, befides thefe concurrent caufes, It 

 is extremely probable that, in the greater 

 and more terrible ejedlions, another more 

 powerful principle comes in aid, which is 



* From the agents which by their expanfive force 

 produce the eruiSlations of volcanos I do not mean to 

 exclude caloric, which fometimes mud neceffarily co- 

 operate J that is, when in the volcanic recefles a greater 

 quantity of this fluid is fuddenly difengaged than can 

 eafily find a pafTage through the pores of the furround- 

 ing bodies. Then, as Lavoifier has obferved. Caloric 

 will adl like other common eiaftic fluids, and overturn 

 C'^'ery thing which oppofes it. Except in this circum- 

 ftance, however, I do not fee what immediate adlion it 

 can have in volcanic eje6lions. 



v©L. nr. A a water. 



