WATT. 65 



municatmg it to Mr. Cavendish, and on the omission of 

 any assertion in Mr. Cavendish's paper, even in the part 

 written by Sir C. Blagden with the view of claiming pri- 

 ority as against M. Lavoisier, that Mr. Cavendish had 

 drawn his conclusion before April 1783, although in one 

 of the additions to that paper reference is made to Mr. 

 Watt's theory. 



As great obscurity hangs over the material question at 

 what time Mr. Cavendish first drew the conclusion from 

 his experiment, it may be as well to examine what that 

 great man's habit was in communicating his discoveries to 

 the Royal Society. 



A Committee of the Eoyal Society, with Mr. Gilpin the 

 clerk, made a series of experiments on the formation of 

 nitrous acid, under Mr. Cavendish's direction, and to satisfy 

 those who had doubted his theory of its composition, first 

 given accidentally in the paper of January 1784, and after- 

 wards more fully in another paper, June 1785. Those 

 experiments occupied from the 6th December, 1787, to 

 19th March, 1788, and Mr. Cavendish's paper upon them 

 was read 17th April. 1788. It was, therefore, written and 

 printed within a month of the experiments being concluded. 



Mr. Kirwan answered Mr. Cavendish's paper (of 15th 

 January, 1784) on water, in one which was read 5th Feb- 

 ruary, 1784, and Mr. Cavendish replied in a paper read 4th 

 March, 1784. 



Mr. Cavendish's experiments on the density of the earth 

 were made from the 5th August, 1797, to the 27th May, 

 1798. The paper upon that subject was read 27th June, 

 1798. 



The account of the eudiometer was communicated at 

 apparently a greater interval ; at least the only time men- 

 tioned in the account of the experiments is the latter half 

 of 1781, and the paper was read January 1783. It is, 

 however, probable, from the nature of the subject, that he 

 made further trials during the year 1782. 



That Mr. Watt formed his theory during the few months 

 or weeks immediately preceding April, 1783, seems pro- 

 bable.* It is certain that he considered the theory as his 



* That the idea existed in his mind previously, is proved by his de- 

 clarations to Dr. Priestley, cited by the latter; by his own assertions, 



F 



