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cclTible, fuch as the carbonic acid gas, hy- 

 drogenous gas, oxygenous gas, &c. 



In fad:, M. Dolomieu^ though he did 

 not approach fo near to the crater of 

 Stromboli as I did, yet, from the obferva- 

 tions he made, conjectured that its ad:ion 

 was caufed by hydrogenous gas. He fup- 

 pofed that the internal fire might difengage 

 this gas from the matters exifting near, but 

 not immediately touching, the volcanic fur- 

 nace ; and that this gas, by fubterranean 

 paflages, might reach the principal cavity 

 in which the conflagration rages, and there 

 fuddenly take fire. 



This hypothefis, which that judicious 

 naturaUft has propofed only in the fhape of 

 a doubt or conjediure, is extremely plau- 

 fible, nor do I hefitate to believe that it Is 

 frequently the true explanation of what 

 takes place in burning volcanos ; though, 

 with refpedt to Stromboli, it cannot be 

 maintained when we compare it with the 



fafts 



