LORD BROUGHAM’S APPENDIX. 475 
periments. In short, the letter was not read till April, 1784.* 
This letter was incorporated by Watt in a Memoir addressed 
to Deluc, dated 26th Nov. 1783.t Many new observations, 
and new reasonings, were introduced into this Memoir, although 
nearly the whole of the original letter was preserved in it, and 
in the printing it was distinguished from the additions by in- 
verted commas. The important deduction, previously quoted, 
will be found in the part thus marked. We read also that the 
letter was communicated to several Fellows of the Royal Soci- 
ety when it reached Priestley in April, 1783. 
In Cavendish’s Memoir, such as it was when read, there was 
no allusion to Watt’s theory; but it is mentioned in an addi- 
tion, entirely in the handwriting of Cavendish, posterior to the 
reading of Watt’s letters, (Phil. Trans. 1784, p. 140.) In this 
addition Cavendish gives his reasons for not liking to render 
his conclusions complicated as Watt did, with considerations 
relative to the disengagement of latent heat ; but it leaves us 
in doubt on the question as to whether the author was ever 
aware of the letter to Priestley of April, 1783, or whether he 
only saw the letter dated 26th of November, 1783, and read 
the 29th of April, 1784; on which it is requisite to remark 
that the two letters appeared in the Philosophical Transactions 
united in one. The letter to Priestley of the 26th April, 
1783, remained some time (two months according to Watt’s 
Memoir,) in the hands of Sir Joseph Banks and other Fellows 
of the Royal Society, during the spring of 1783. This is what 
we learn from the circumstances related in the note at p. 330. 
It seemed difficult to suppose that Blagden, Secretary of the 
* The letter to Priestley was read the 22d of April, 1784. 
+ Undoubtedly the Genevese physicist, then in London, received it 
at the time. It remained in his hands until Watt heard of the reading 
of Cavendish’s Memoir at the Royal Society. From that moment my 
father made ail possible arrangements for the Memoir addressed to 
Deluc and the letter of the 26th of April, 1783, addressed to Dr. Priest- 
ley, being read immediately at the Royal Society. This reading, 
claimed by Watt for the Memoir addressed to Deluc, was dated 29th 
of April, 1784.—( Note by Mr. Waitt, jun.) 
