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, 1785. 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 17th of April, 
1788. 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, 1798. ‘The date of the reading of that Memoir was the 
27th 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. 7 
We cannot believe that Blagden would have heard no 
mention of Cavendish’s theory prior to the date of Watt’s 
