44. 



the errors in this account are such as to exonerate Watt from any su- 

 spicion of having supplied or revised it. 



The fault which, since the subject has been forced into public no- 

 tice, we are compelled not to leave unobserved in the conduct of the 

 latter, is the silence with which he passed by the experiments of Ca- 

 vendish in his letters both to Priestley and De Luc. How fully Priest- 

 ley's acknowledgment, that Cavendish had made before him the same ex- 

 periments, was understood by others, appears from the following abs- 

 tract of the contents of Priestley's paper on the seeming conversion of 

 water into air, which I have extracted from the Journal Book of the 

 Royal Society. " These arguments received no small confirmation /wm 

 an experiment of Mr. Cavendish, tending to prove the reconversion of 

 air into water, in which pure dephlogisticated air and inflammable air 

 were decomposed by an electric explosion, and yielded a deposit of wa- 

 ter equal in weight to the decomposed air." This abstract, which shows 

 how ill-founded the story is of the discovery of the composition of water 

 being received with ridicule by the Royal Society, was made by the Se- 

 cretary of the Society immediately after the reading of Priestley's paper 

 in June 1 783. The Secretary was Mr. Maty, not Dr. Blagden, who did 

 not hold the office of Secretary till May 1784, and was not a member of 

 the Council ; so that he is in no way liable to the suspicion intimated 

 by Lord Brougham of having shown Watt's letter to Cavendish, nor 

 to the reproach which M. Arago casts upon him, of not speaking the 

 whole truth respecting the precise date at which Watt's opinions were 

 made known in London. The fact is, that there is a good deal of con- 

 fusion attending this letter of Watt's ; the date with which it is printed 

 is April 26 ; but that date is corrected in the MSS. in two places to 

 April 2L Watt says it was received by Priestley in London ; and 

 yet it is certain that Priestley transmitted it to Sir J. Bankes, with his 

 own paper, from Birmingham : its date however is of no consequence. 

 The perusal of the entire letter has satisfied me that the real ground 

 of Watt's claim to original views on this subject was not the observa- 

 tion of what he calls " the obvious fact, that inflammable and dephlo- 

 gisticated air unite with violence, and that water is the only fixed pro- 

 duct," but the theory which he engrafted on this fact, that the airs are 

 decomposed, and that their bases, parting with the elementary heat with 

 which they were combined, enter into a new combination, and so form 

 water — a theory which Lavoisier had applied generally to the other 

 pheenomena of combustion six years before. 



M. Arago, however, might have found for the subject of his Eloge a 

 higher ground of scientific praise in less questionable applications of the 



