/ttiul perhaps lefs time would have been fufScient; 

 'when I found, upon trial, that it was reftored to 

 sits former perfectly wholefome (late. It effer* 

 vefced with nitrous air as much as the bed common 

 ■air ever does, and even a candle burned in it very 

 well, which 1 had never before obferved of any kind 

 •of noxious air meliorated by agitation in water. 

 This feries of facts* relating; to air extracted from 

 nitre, appear to me to be very extraordinary and 

 important, and, in able hands, may lead to confi- 

 o*erable discoveries. 



There are many fubftances which impregnate the 

 •air in a very remarkable manner, but without 

 making it noxious to animals. Among other things 

 I tried volatile alkaline falts, and camphire* the 

 latter of which I melted with a burning glafs, in 

 air inclofed in a phial. Themoufe which was put 

 into this air fneezed and coughed very much, efpe- 

 cially after it was taken out ; but it prefently re 

 covered, and did not appear to have been fenilbly 

 injured. 



Having made feveral experiments with a mixture 

 of iron filings and brimftone, kneaded to a parte 

 with water, I had the curioiity to try what would 

 be the effect of fubftitutinr brais duff in the place 

 of the iron filings* The refult was, that when 

 -this mixture had flood about three weeks, in a 

 given quantity of air, it had turned black, but was- 

 not increafed in bulk. The air alfo was neither 

 fenfibly increafed nor decreafed, but the nature of 

 it was changed, for it extinguished flame, it would 

 have killed a moufe prefently, and was not reft ored 

 •by fixed air, which had been mixed with it feveral 



l have 



