( 3^3 ) 



the volcanic fires. The matrafles were of 

 that capacity, that the twelve ounces of 

 every product fcarcely occupied one third 

 of their body ; fo that the melted matter 

 might inflate and tumefy without impedi- 

 ment. 



This glafs I expofed in a chemical fur- 

 nace to a fire of eight hours continuance ; 

 three with a moderate, and five with a 

 ftrong heat. At the end of an hour and 

 three quarters, there appeared upon the 

 mercury a fmall quantity of aeriform fluid, 

 which, when examined, did not take fire 

 at the flame of a candle immerfed in it, no|* 

 extinguifh that flame, nor render it brighter, 

 but left it precifely as it was in the atmo- 

 fphere ; confequently this fluid muft be 

 confidered as common air, that is, a portion 

 of that contained in the vefl^els ufed in the 

 experiment. That fuch was the fadt, I was 

 ftill more convinced by fubjeding this fluid 

 to other experiments. Another fmall quan- 

 tity of fluid afterwards colle<Sted from time 

 to time on the mercury, which I examined 



as 



