02 WATT. 



with many further ohservations and reasonings, hut almost 

 the whole of the original letter is preserved in this, and is 

 distinguished by inverted commas. One of the passages 

 thus marked is that which has the important conclusion 

 above mentioned ; and that letter is stated, in the subse- 

 quent one, to have been communicated to several members 

 of the Eoyal Society at the time of its reaching Dr. Priest- 

 ley, viz. April, 1783. 



In Mr. Cavendish's paper as at first read, no allusion is 

 to be found to Mr. Watt's theory ; but in an addition made 

 in Sir C. Blagden's own hand, after Mr. Watt's paper had 

 been read, there is a reference to that theory (Phil. Trans. 

 1784, p. 140), and Mr. Cavendish's reasons are given for 

 not encumbering his theory with that part of Mr. Watt's 

 which regards the evolution of latent heat. It is thus left 

 somewhat doubtful, whether Mr. Cavendish had ever seen 

 the letter of April 1783, or whether he had seen only the 

 paper (of 26th November, 1783) of which that letter formed 

 a part, and which was read 29th April, 1784. That the 

 first letter was for some time (two months, as appears from 

 the papers of Mr. Watt) in the hands of Sir Joseph Banks 

 and other members of the Society, during the preceding 

 spring, is certain, from the statements in the note to 

 p. 330 ; and that Sir Charles Blagden, the Secretary, should 

 not have seen it, seems impossible ; for Sir Joseph Banks 

 must have delivered it to him at the time when it was in- 

 tended to be read at one of the Society's meetings (Phil. 

 Trans., p. 330, Note), and, as the letter itself remains 

 among the Society's Records, in the same volume with the 

 paper into which the greater part of it was introduced, it 

 must have been in the custody of Sir C. Blagden. It is 

 equally difficult to suppose, that the person who wrote the 

 remarkable passage already referred to, respecting Mr. Ca- 

 vendish's conclusions having been communicated to M. 

 Lavoisier in the summer of 1783 (that is, in June), should 

 not have mentioned to Mr. Cavendish that Mr. Watt had 

 drawn the same conclusion in the spring of 1783 (that is, 



both the letter to Dr. Priestley of 26th April, 1783, and that to M. De 

 Luc of 26th November, 1783, should be successively read. The former 

 was done on the 22d, and the latter on the 29th April, 1784. [Note by 

 Mr. James Watt.'] 



