Chap . II .] Chem leal Pit ilosophy, 1 07 



While Dr. Priestley was making experiments on 

 oxygen gas, Scheele, of Sweden, proceeded to the 

 analysis of air in a different manner. Froni iirs 

 experiments he concluded that common air is com- 

 pounded of two diilerent elastic fluids, viz. foul 

 mvy which constitutes more than two thirds of the 

 whole, and another air, which is alone capable of 

 -supporting flame and animal life, and to which he 

 gave the name of empyreal air. The foul air of 

 Scheele was the same with the phlogisticated air of 

 Priestley ; and the empyreal air of the former ^\ as 

 the same with the depJdogisticated air of the latter, 

 or with what is at present called oxygen gas. 



While Scheele was occupied with these experi- 

 ments, Lavoisier was assiduously employed on the 

 same subject, and was led, by a different road, to 

 precisely the same conclusions. He found that 

 common air is composed of azotic and oxygen 

 gases ; and, from a variety of experiments, he de- 

 termined the proportions to be 73 parts of azotic 

 gas, and '21 parts of oxygen gas. These experi- 

 ments were made in the year 177(>. 



The discovery of the composition of zcater, before 

 alluded to, next follows in the list of those bril- 

 liant acquisitions which distiuguish the annals of 

 chemical science during this period. — ^\'ater v.as 

 believed, by the ancients, to be one of the fcuir 

 elements of which every other body is composed. 

 The opinion of its being a simple substance seems 

 generally to liave prevailed until the year 17^ 1 , when 

 Mr. Henry Cavendish, of Great Britain, discovered, 

 by several experiments, that it is a compound, and 

 formed by the union of oxygen and hydrogen. In 

 iifew mx)nths afterwards, the conclusion of Mr. Ca- 



