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facls obferved. For, in the firfl place, 

 though this gas has the property of rifing 

 in flame, it has alfo that of extinguifhing 

 fire placed within its atmofphere. How- 

 then can the lava melted in the cavern of 

 Stromboli be penetrated, put in motion, 

 and rarefied by this gas, without the dimi- 

 nution, not to fay the entire lofs, of that 

 ardent rednefs which I obferved in it during 

 the night ? Secondly, though, in this vol- 

 cano, the detonation is always infeparable 

 from the explofion, we cannot fuppofe the 

 former occafioned by hydrogenous gas, un- 

 lefs we would admit an efFed: incomparably 

 lefs than the caufe. In the repeated vifits 

 I made to that volcano, I obferved that the 

 ftrongeft detonations were not louder than 

 the found of a very fhort hollow thunder ; 

 and that, at the moment they are heard, 

 the tumors which cover the lake of fiery 

 lava, many of which are feveral feet in dia- 

 meter, burft. Is it not then evident that 

 the fuperabundant quantity of this gas, 

 contained in fo great a number of tumors, 

 and fulminating almoft at one inftant, muft 



caufe 



