M. Arago's Biographical Memoir of James Watt. 271 



Lavoisier distinctly states, in precise terms, that Mr Blagden, 

 secretary of the Royal Society of London, was present at his 

 first experiments on the 24th June 1783 ; and " that he told 

 him that Cavendish, having previously endeavoured, in Lon- 

 don, to burn hydrogen in close vessels, had obtained a sensible 

 quantity of water." Cavendish, also, in his own memoir, al- 

 ludes to the communication made by Blagden to Lavoisier. 

 According to him, it was more ample than the French chemist 

 avows ; and he states that the confidential communication em- 

 braced the conclusions to which the experiments led ; in other 

 words, the theory of the composition of water. Blagden also 

 himself took part in the controversy ; and in Crell's Journal, 

 in the year 1786, did what he could to confirm the assertion 

 of Cavendish. According to him, the experiments of the 

 Parisian academician were only a simple verification of those 

 of the English chemist ; and he assures us, that he announced 

 to Lavoisier, that the water produced in London was of a 

 weight precisely equal to that of the two consumed gases. 

 Finally, Blagden adds : Lavoisier has said the truth, hut not the 

 whole truth. This reproach is severe ; but, if it was deserved, 

 shall I not materially diminish its severity, if I prove that, 

 with the exception of Watt, all those whose names appear in 

 this piece of history were more or less exposed to it ? 



Priestley reports in detail, and as his own, the experiments 

 from which it results that the water produced by the detona- 

 tion of a mixture of oxygen and hydrogen, is of a weight pre- 

 cisely equal to that of the two consumed gases. Cavendish, 

 some time after, claims this conclusion as his property, and 

 insinuates, that he had communicated it verbally to the che- 

 mist of Birmingham. 



From this equality of weights. Cavendish deduces the conse- 

 quence that water is not a simple body. In the first instance, 

 he makes no mention whatever of a memoir deposited in the 

 archives of the Royal Society, and in which Watt developed 

 the same theory. It is true that, when Cavendish's paper was 

 printed. Watt's name is not omitted ; but it is not in the re- 

 cords that the account of the labours of the celebrated en- 

 gineer had been found : it is stated that the information was 

 obtained from a paper recently read at a public meeting. It 



