35 



air that disappears in the combustion of dephlogisticated and of common 

 air, with inflammable gas, enjoying the peculiar advantage of a more in- 

 timate acquaintance with all the gases operated upon than any other 

 chemist possessed. Of the oxygen examined by so many chemical tests 

 he knew the quality, and the quantity, whether he used the air of 

 the atmosphere or obtained it from any other source, whilst his 

 constant employment of the test of specific gravity gave him an ac- 

 curate knowledge of the residual gas : he had ascertained also with 

 care the properties of inflammable gas, and even gone some way, in 

 1766, towards determining, by attention to the comparative loudness 

 of the explosion, the proportions in which oxygen and hydrogen most 

 perfectly combine*. 



These observations may tend to diminish the surprise with which 

 the most skilful and experienced in such researches cannot fail to 

 be struck, when they observe the precision with which Cavendish, 

 as soon as Warltire's experimentf had suggested to his mind an experi- 

 mentum, crucis, to determine between the truth of Scheele's supposition 

 and the more probable explanation of what had become of the burnt 

 air, offered by the circumstance of the deposition of water, proceeded 

 without the loss, if I may so speak, of a single move, by a regular 

 gradation of six quantitive trials of explosive mixtures, to solve the 

 question. In the fifth or mean of these (MSS. p. 114) he found the 

 point at tvhich the entire volume of two of the gases disappeared, lea- 

 ving the entire volume of the nitrogen of its proper specific gravity 

 and proved by chemical tests to have parted with all its oxygen : the 

 bulk of two volumes of hydrogen and one of oxygen was gone, but 



* Phil. Trans., vol. Ivi. 



f It was not Warltire, but Volta, who first fired mixtures of hydrogen and 

 air by the electric spark. (See a letter from Volta to Priestley, dated Como, 

 Dec. 10, 1776. Priestley's Experiments on Air, 3d Ed., 1781, App. p. 381.) 

 In 1779 Priestley endeavoured to ascertain the relative proportions of phlo- 

 giston in nitrous gas and inflammable air/ "by the help," he says, "of that 

 ingenious experiment of Mr. Warltire's mentioned in the Appendix to my 3d 

 volume, p. 367, viz., burning inflammable air in a given quantity of common 

 air." "Of this curious problem, however [the proportions of phlogiston], I 

 obtained a more accurate solution from the mode of experimenting introduced 

 by that ingenious philosopher, M. Volta, who fires inflammable air, in com- 

 mon, by the electric spark, and consequently can determine the exact propor- 

 tion of inflammable decomposed in a given quantity of common air." Priest- 

 ley's skill in Eudiometry did not enable him, however, to come nearer the 

 truth than to find the proportion of common air dephlogisticated by inflam- 

 mable air as 2 : 1 . 



c 



