[ XiX ] 



ance than thofe he made upon the 

 various kinds of airs. 



The difcovery of that wonderful 

 aerial fluid, which in purity and fit- 

 nefs for refpiration fo far exceeds 

 the befl atmofpheric air, that an ani- 

 mal may protract its life in it five 

 times longer than in the belt com- 

 mon air, excites fo much the greater 

 admiration, as he found it firfl in 

 fuch bodies which by their nature 

 muft have been fufpected to conceal 

 rather within their fubftance dele- 

 terious qualities, fuch as calcined 

 mercury and red precipitate. He 

 has given to this air the very proper 

 appellation of dephlogijlicated air, or 

 air deprived of that inflammable 

 principle which is the chief ingre- 

 dient that renders our atmofpheric 

 air more or lefs impure, and thus 

 more or lefs fit for refbiration. 



b 2 His 



