Discovery of the Composition of Water. 47 



he had a knowledge of the experiments both of Mr Cavendish 

 and of Lavoisier and La Place on the composition of water. 

 In his published paper, he says, " I am obliged to your friend- 

 ship (De Luc's) for the account of the experiments which 

 have been lately made at Paris on this subject, with large 

 quantities of the two kinds of air, by which the essential point 

 seems to be clearly proved, that the deflagration or union of 

 dephlogisticated and inflammable air, by means of ignition, 

 produces a quantity of water equal in weight to the airs ; 

 and that the water thus produced appeared to be pure water." 

 M. de Luc's letter, conveying this information, is of the 9th 

 of February 1784. 



Mr Watt, it would appear from this his published statement, 

 was induced by his friends to bring forwai-d his views on the 

 composition of water. The friend who was most active on 

 this occasion, judging from the correspondence, was M. de 

 Luc, who seemed to take a pleasure in exciting Mr Watt 

 against Mr Cavendish. His letter of the 2d of May, finished 

 on the 4th, is an example of the kind, in which he raises the 

 suspicion of plagiarism on the part of Mr Cavendish,* and 

 to which, in reply, Mr Watt observed, " I mean to be in 

 London next week, where your demands on my person shall 

 be answered, and to which time I must refer particulars, 

 having much business, but of another nature than the pla- 

 giarism of Mr C, pressing hard upon me. On the slight glance 

 I have been able to give your exti'acts of the paper,t I think 

 his theory very different from mine ; which of the two is right 

 I cannot say ; his is more likely to be so, as he has made 

 many more experiments, and has, consequently, more facts 

 to argue upon. I by no means wish to make any illiberal 

 attack on Mr C. It is barely possible he may have heard 

 nothing of my theory," adding, " as to what you say of mak- 

 ing myself ' des jaloux^ that idea would weigh very little ; for 

 were I convinced I had foul play, if I did not assert my 

 right, it would either be from a contempt of the modicum of 

 reputation which could result from such a theory, or from a 



* Correspondence, p. 48. 



t Sent by Mr Cavenrlish, in MS., to W. de Luc, at tin' i'0([iiest cf the latter. 



