145 



though it should retain its elasticity *." Dr Hooke 

 asserted, that this ingredient or substance inherent 

 in, and mixed with the air, is like, if not the very 

 same with that which is fixed in saltpetre, by which, 

 during combustion, inflammable bodies are dissol- 

 ved f. The same opinion was afterwards held by 

 Willis, Lower, and Mayhow, all of whom likewise 

 considered the nitrous quality of the air to act an 

 important part in respiration. The last author, in 

 particular, made experiments precisely similar to 

 those which have lately been brought forward, to 

 prove, that both by the burning of a candle and 

 other combustible bodies, and by the respiration of 

 animals, the nitro-aerial particles of the air were ex- 

 hausted, whereby the volume of air was diminished, 

 and the residual air was unable afterwards to sup- 

 port either life or flame J. The exhibition, how- 

 ever, of this peculiar, or nitro-ae'rial, part of the air 

 in a distinct and separate form, we owe to the ge- 

 nius of Dr Priestley, who, by the discovery of pure 

 or dephlogisticated air, in the month of August 

 1774, first made us acquainted with the true com- 

 position of the atmosphere. This great discovery, 

 and the use which he made of it, enabled this cele- 

 brated philosopher to propose the first consistent 

 explanation of the phenomena of respiration that 

 had ever been offered to the public ; and, although 

 the theoretical opinions on which that explanation 



* Sins, par. 14-3. et seq. 2d Edition, 

 f Micrographia, p. 103. An. 1665. 

 t Tractat. Quinque, p. 98. et seq. 



K 



