J,96 On theJ)iscovery qf^the Composition of Water, 



In proof pi these assertions, I refer to the following passages 

 ffJ'Uie Ecfinburgh Uevievv. . 



''^*Mr. Watt felt a just indignation at the Idea suggested' Iby; 

 Deluc, of his not claiming the merit w/iich belo7igedto his )iy- 

 pothesis ; but we are sure that his astonishment would be 

 equal to ours, were he to learn that that hypothesis had been 

 made to supersede and cast into oblivion the grajid ex2)e7-i' 

 mental discovery of Cavendish. The great merits of these two 

 great men are fortunately not in collision, Mr. Watt will 

 for ever enjoy the honour of that singular sagacity which pre- 

 sented to him the hypothesis of the composition of water; and 

 Cavendish will never lose the glory 'which belongs to hitUy qf 

 having given that hypothesis, whether he ncas cog7iisant of it on 

 not, the force atid stability of truth." If the reviewer shaulct 

 perceive any ambiguity in these expressions when standing 

 alone, he will find their meaning amply explained in previoits 

 parts of the Review, and especially in the following expres- 

 sion : — "The glory of having discovered the composition of 

 water, that is, of having established it as a physical truth, &,c. 

 &c." I have likewise stated, that " Mr. Watt never pretendeijj 

 to have discovered the composition of water;" and a little 

 further on I add, that "as Mr. Watt never wrote another 

 word on the subject, nor made a single experiment after his 

 paper (the paper containing his hypothesis) was printed, how 

 is it possible to identify this hypothesis with the discovery of the 

 composition qfwaterl" — No. 142, p. 496, Jan. 1840. 



Now this decision, which in the Review I have characterize'c^ 

 as "deliberately and impartially formed," is precisely, and in 

 terms, the very same as that of Dr. Black. " This idea," 

 says he, "of the nature of water was suggested by Mr. Watt; 

 Mr. Cavendish, however, was the first who gave it solid foun- 

 dation and credibility" — p. 494. 



Having thus repelled the charges of the reviewer, I may 

 now state the reasons why I might have talten up the subject 

 as the British Quarterly reviewer expresses it, even if I had 

 not been compelled to discuss it in a review of the Life and 

 Inventions of Mr. Watt. In the year 1819, immediately after 

 Mr. Watt's death, his friends submitted to Dr. Hope and 

 myself his claims to the discovery of the composition of water. 

 After a careful examination of the documents on which these 

 claims were founded, we came to the decision that the merit 

 of the discovery belonged to Mr. Cavendish. This decision, 

 however, was not satisfactory to Mr. Watt's friends, and we 

 accordingly find a detailed statement of his claims in the bio- 

 graphical sketch of him published in the Supplement to the 

 Encyclopcedia Britannica. This statement was reprinted by 



