480 JAMES WATT. 



chemist's habits when he communicated his discoveries to the 

 Royal Society. 



A Committee of that Society, to which Gilpin belonged, 

 made a series of experiments on the formation of nitric acid. 

 This Committee, placed under the direction of Cavendish, 

 sought to convince those who doubted of the composition of 

 the acid in question, incidentally indicated in the Memoir of 

 .January, 1784, and afterwards more at length in a Memoir of 

 June, 1 785. The experiments were made between the 6th 

 of December, 1787, and the 19th of March, 1788. The date 

 of the reading of Cavendish's Memoir was the 1 7th of April, 

 1 788. The reading and the printing then occurred within 

 less than a month of the completion of the experiments. 



Kirwan presented his objections to Cavendish's Memoir 

 relative to the composition of water, on the 5th of February, 

 1784. Cavendish's answer was read on the 4th of the follow- 

 ing March. 



The experiments on the density of the earth occupied the 

 interval between the 5th of August, 1797, and the 27th of 

 May, 1 798. The date of the reading of that Memoir was the 

 2 7th of June, 1798. 



In the Memoir on the eudiometer, the experiments quoted 

 were made in the latter half of 1781, but the Memoir was not 

 read till January, 1783. Here the interval was greater than 

 in the preceding communications. From the nature of the 

 subject, however, it is probable that the author undertook 

 fresh experiments in 1782. 



Every thing renders it probable that Watt conceived his 

 theory in the course of a few months or even of a few weeks 

 prior to April, 1783. It is certain that this theory was con- 

 sidered by him as his property, for he did not allude to any 

 anterior or analogous communication ; nor does he say that 

 he had heard of Cavendish having come to similar conclu- 

 sions. 



We cannot believe that Blagden would have heard no 

 mention of Cavendish's theory prior to the date of Watt's 



