[ is 5 ] 



ing that candles would burn, and animals live, in 

 air extracted from faltpetre. I therefore fpent a 

 good deal of time in attempting, by a burning-glafs, 

 and other means, to impregnate this noxious air 

 with fome effluvium of faltpetre, and, with the fame 

 view, introduced into it the fumes of the fmoaking 

 fpirit of nitre j but both thefe methods were altoge- 

 ther ineffectual. » 



In order to try the effect of heat, I put a quantity 

 of air, in which mice had died, into a bladder, tied 

 to the end of the item of a tobacco-pipe, at the other 

 end of which was another bladder, out of which the 

 air was carefully preffed. I then put the middle 

 part of the ftem into a chafing-difh of hot coals, 

 ftrongly urged with a pair of bellows j and, preffing 

 the bladders alternately, I made the air pafs feveral 

 times through the heated part of the pipe. I have 

 alfo made this kind of air very hot, itanding in water • 

 before the fire. But neither of thefe methods were of 

 any ufe. 



Rarefaction and condensation by inftruments were 

 alfo tried, but in vain. 



Thinking it poffible that the earth might imbibe 

 the noxious quality of the air, and thence fupply the 

 roots of plants with fuch putrefcent matter as is 

 known to be nutritive to them, I kept a quantity 

 of air, in which mice had died, in a phial, -one half 

 of which was filled with fine garden mould ; but, 

 though it flood two months in thefe circumftances, 

 it was not the better for it. 



I orice imagined that, fince feveral kinds of air 



cannot be long feparated from common air, by being 



confined in bladders, in bottles weli corked; or even 



Vol. LXIL B b clofed 



