[BookV. 



BOOK V. 



OP AIR. 

 CHAP. I. 



HISTORY OF DISCOVERIES RELATIVE TO 

 AIR. 



Vague Notions ?f the early Chemifis.Van Hetment.Choak and Fire 

 Damp. Mr. oy!e.Di/coveries of Dr. Hales. Of Dr. Black. 

 Of Dr. PrieJtley.Of Mr. CavendiJh.Of Lavoi/ter. Vital or 

 dtphlogijiicated Air dif covered by Dr. Priejlley. Composition of 

 Water and ofNitrout Air discovered by Mr. Cavend'ijh. 



THOSE aerial fluids, which in their nature and 

 effects are different from the air of our atmo- 

 fphere, did not efcape the notice of the early chemifts; 

 but they paid little attention to the nature of them, 

 contenting themfelves with giving them a name which 

 meant nothing, denominating them, in general, Jpiritus 

 Jyheftris. 



Van Helmont diftinguilhed them by the name of 

 gas, which he defined to be a fpirit or incoercible va- 

 pour, as the word gas, or rather ghoaft, in the Dutch 

 language, fignifies. He fuppofes the gas to have been 

 retained by the fubftances from which it is extracted, 

 in a fixed or concrete form. He afitrts, that fixty- 

 two pounds of charcoal contain fixty-one of gas, and 

 only one of earth, and attributes the fatal effects which 



workmen 



