12 Biographical Account of [Ji4N. 



it more probable, with Sir Isaac Newton, that it is owing to the 

 rapid internal motion of the particles of the hot body. The latent 

 heat of water he found to be 150'^. The observations on the con- 

 gelation of the nitric and sulphuric acids are highly interesting, 

 but not susceptible of abridgment. H e showed that their freezing 

 points varied very considerably, according to the strength of 

 each ; and drew up tables indicating the freezing point of 

 acids of various degrees of strength. These papers constitute 

 one of the most interesting, and perhaps the best established, 

 part of the theory of heat^ as at present taught by chemical 

 philosophers. 



But the most splendid and valuable of Mr. Cavendish's 

 chemical experiments were published in two papers, entitled 

 Experiments on ylir; the first inserted in the Philosophical 

 Transactions for 1784 (vol. Ixxiv. p. 119); and the second in the 

 Transactions for 17^5 (vol. Ixxv. p. S72). The object of these 

 experiments was to determine what happened during the 

 phlogistication of air, as it was at that time termed ; that is, 

 ^ the change which air underwent when metals were calcined in 

 contact with it, when sulphur or phosphorus was burnt in it, and 

 in several similar processes. He showed, in the first place, that 

 there was no reason for supposing that carbonic acid was formed, 

 except when some animal or vegetable substance was present ; 

 that when hydrogen gas was burnt in contact with air or 

 oxygen gas, it combined with that gas and formed water ; that 

 nitrous gas, by combining ivith the oxygen of the atmosphere, 

 formed nitrous acid ; and that when oxygen ^nd azotic gas are 

 mixed in the requisite proportion?, and electric sparks passed 

 through the mixture, they combine and form nitric acid. The 

 first of these opinions occasioned a controversy between Mr. 

 Cavendish and Mr, Kirwan, who had maintained that carbonic 

 acid is always produced when air is phlogisticated. Two papers 

 on this subject are published in the Philosophical Transactions 

 by Mr. Kirwan (Phil. Trans. 1784, vol. Ixxiv. p. 154 and 178); 

 and one by Mr. Cavendish (Ibid. p. 170); each remarkable 

 examples of the peculiar manner of the respective writers. All the 

 arguments of Kirwan are founded on the experiments of others ; 

 he displays great reading, and a strong memory ; but does not 

 discriminate between the m.erits of tlie chemists on whose 

 authority he founds his opinions. Mr. Cavendish, on the other 

 hand, never advances a single opinion which he has not put to 

 the test of experiment ; and never suffers himself to go farther 

 than his experiments will warrant. Whatever is not accurately 

 determined by unexceptionable trials, is merely stated as a 

 conjecture, upon which little stress is laid. 



In the first of these celebrated papers Mr. Cavendish has 

 drawn a comparison between the phlogistic and antiphlogistic 



