relative to Black, Watt, and Cavendish. 115 



such feelings, as he ought always to have been above their influ- 

 ence, that may be said without offence of which he so disliked 

 the mention; he had the honour of raising himself to the highest 

 place among the chemical philosophers of the age, emerging by 

 his merit alone from an obscure condition." A simple anecdote 

 may suffice to set his feelings on this subject in a more favour- 

 able light. When Davy was exhibiting to myself and three 

 others the discoveries which he had then recently made rela- 

 tive to his safety-lamp, and when those present, among whom 

 were the Hanoverian minister and the late Lord Lonsdale, 

 were highly admiring the beauty of his experiments, with still 

 higher admiration I heard him reply, "Yes, 1 have some rea- 

 son to be proud of them, for my experiments on flame were 

 first made with a tallow candle in an apothecary's shop." 



In these slight sketches which you have given us of the 

 history of men eminent in science, tnere is one other scientific 

 subject besides the discovery of the composition of water, on 

 which you appear to have bestowed some consideration, 

 namely, — the first discoveries of the gases. Here Cavendish 

 is still out of favour with you. You pluck another feather 

 from his wing ; and having made a present of the discovery 

 of water to Mr. Watt, dispense that of hydrogen gas to Dr. 

 Black. 



"The nature of hydrogen," you say, " was perfectly known 

 to him, and both its qualities of being inflammable, and of 

 being so much lighter than atmospheric air ; for as early as 

 1766 he invented the air-balloon, showing a party of his friends 

 the ascent of a bladder filled with inflammable air: Mr. 

 Cavendish only more precisely ascertained its specific gravity, 

 and showed, what Black could not have been ignorant of, that 

 it is the same from whatever substance it is obtained*." 



You ought to have recollected, when again contravening the 

 received opinion of chemists f, your own remarks on the sup- 

 posed omission of Cavendish to state exactly the time when 

 he had communicated to Priestley his experiments on the com- 

 position of water. " Dans une addition de Blagden faiteavec 

 le consentement de Cavendish, on donne aux experiences de 

 ce dernier le date de l'ete" de 1781. On cite une communica- 

 tion de [a] Priestley, sans en preciser I'epoque, sans parler de 

 conclusions, sans meme dire quand ces conclusions se pre- 



* Life of Black, p. 383. 



t The received account of the discovery of hydrogen is this : — " Its com- 

 bustible quality is described in the works of Boyle and Hales, of Boerhaave 

 and Stahl; but it was not till the year 1766 that its properties were par- 

 ticularly ascertained, and the difference between it and atmospheric air 

 pointed out by Mr. Cavendish." — Encycl. Brit., Art. Chemistry, 1810. 



