214 Biographical Memoir of Henry Cavendish. 



this combustion, remarked, with surprise, some moisture on 

 the vessels which he employed ; but he went no further. Mr 

 Cavendish, who in some measure introduced inflammable air 

 into chemical experiments, was also the first who announced the 

 great influence which it exerted over the combination of bodies *. 

 Carrying, as in his first investigation, the precision for which 

 he was distinguished, to a subject hitherto but superficially exa- 

 mined, he burnt inflammable air in close vessels by the electric 

 spark, supplying it by degrees with the inflammable air neces- 

 sary for its combustion. He saw that the former of these airs 

 absorbed a determinate portion of the other, and that the whole 

 resolved itself into a quantity of water equal to the weight of 

 the gases that had disappeared. This great phenomenon, which 

 Mr Cavendish took three years to establish, was announced to 

 tile Royal Society on the 14th January 1784. Our fellow mem- 

 ber. Count Monge, who had formed the same idea, and made 

 the same experiments as Mr Cavendish, communicated their 

 result about the same time to Lavoisier and M. de La Place. 



If the combination of these airs yields water, said M. de la 

 Place, it is because they result from its decomposition. At- 

 tempts were therefore made to decompose water in the same man- 

 ner as it had been composed, and they were successful. These 

 experiments became the key-stone to the arch of his new theory, 

 and explained almost every thing that had previously puzzled 

 him. In fact, water being but a combination of the two airs, 

 wherever it exists, it can furnish them on being decomposed ; 

 and wherever they are formed, it may arise from their union. 



The solutions of metals were at first deduced from inflam- 

 mable air ; and, by a numerous suite of other consequences, the 

 decomposition of organized beings, and the most complicated 

 transformation of their principles. In a word, the theory of 

 chemistry was henceforth seated on its basis. Thus it may be 

 said that this new theory, which produced so great a revolution 

 in science, owed its origin to a discovery made by Mr Caven- 

 dish, and that it was a second discovery of the same philoso- 

 pher which gave it its final completion. He made a third dis- 

 covery, which would suffice to immortalize him, had the others 



• Phil. Trans. 1784, Part I. p. 119; Journ. de Phys. 1704, t. xxv. 

 p. 417. 



