WATT. 399 



A Committee of the Royal 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 afterwards 

 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 February, 

 1 784, 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 probable.* 

 It is certain that he considered the theory as his own, and 

 makes no reference to any previous communication from any 

 one upon the subject, nor of having ever heard of Mr. 

 Cavendish drawing the same conclusion. 



The improbability must also be admitted to be extreme, of 

 Sir Charles Blagden ever having heard of Mr. Cavendish's 

 theory prior to the date of Mr. Watt's letter, and not mention- 

 ing that circumstance in the insertion which he made in Mr. 

 Cavendish's paper. 



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

 declarations to Dr. Priestley, cited by the latter ; by his own asser- 

 tions, p. 335 of his paper ; and by the existing copies of his letters 

 in December 1782. [NOTE BY MR. JAMES WATT.] 



