510 Rev. W. V. Harcourt on Lord Brougham's statements 



Hales however rendered essential service to what may be 

 more strictly called the chemical philosophy of aerial fluids. 

 I have before noticed that we owe to him the discovery of a 

 fact in gaseous chemistry, the consequence of which it is im- 

 possible to overrate — the condensation of atmospheric air by 

 nitrous gas, in such a manner that the two gases were observed 

 by him to occupy the. same space. He first also determined 

 with numerical exactness, and by very ingenious methods, tJie 

 volume of air absorbed in a variety of chemical processes, and 

 stated in the clearest terms the chemical nature of that ab- 

 sorption, — a statement adopted, as I have shown, by Caven- 

 dish, and strangely misconstrued by Priestley. " They were 

 changed," he says, " from a repelling elastic to a fixed state 

 by the strong attraction of other particles which I call absorb- 

 ing." He taught the chemists of the succeeding generation 

 how T to procure almost all the gases which formed the sub- 

 jects of their investigation; and he taught them also the more 

 important lesson of conducting those investigations by measure 

 and weight. Some of his experiments led directly to the most 

 important conclusions at which they arrived. It was not for 

 nothing that he observed that the " Sal Tartar" (very highly 

 calcined) with which he essayed to purify the air for respira- 

 tion had " absorbed one-third of the fuliginous vapours which 

 arose from the burning candle*," or that he recorded experi- 

 ments on phosphorus, in which " 2 grains, fired in a large 

 receiver, flamed and filled the retort with white fumes, ex- 

 panded into a space equal to GO inches, and absorbed 28 cubic 

 inches of air;" and "when 3 grains were weighed soon after 

 it was burnt, it had lost half a grain of its weightf." 



It is true that he made no advance towards analysing the 

 air: and further, he argued, and argued justly, that "the 

 sudden and fatal effect of noxious vapours, which has hitherto 

 been supposed to be wholly owing to the loss and waste of the 

 vivifying spirit of air, may not unreasonably be also attributed" 

 to other causes, which he enumerates. " If," he says, " the 

 continuance of the burning of a candle be wholly owing to the 

 vivifying spirit, then supposing, in the case of a receiver capa- 

 cious enough for a candle to burn a minute in it, that half the 

 vivifying spirit be drawn out with half the air in 10 seconds of 

 time, the candle should not go out at the end of those 10 se- 

 conds, but burn 10 seconds more; which it does not, there- 

 fore the burning of the candle is not wholly owing to the vivi- 

 fying spirit, but to certain degrees of the air's elasticity," — 

 a principle which he goes on to illustrate by the " common 



* Analysis of the Air, edit. 1727, p. 272. 

 f Ibid. p. 169. 



