476 JAMES WATT. 



Society, did not see the Memoir. Sir Joseph Banks must have 

 given it to him, since he intended it to be read at the meeting, 

 (Phil. Trans. 1 784, p. 330, note.) Let us add that as the letter 

 was preserved in the archives of the Society, it was in charge 

 of blagden, the Secretary. Would it be possible to sup- 

 pose that the person whose hand wrote the remarkable passage 

 already quoted, relative to a communication made to Lavoisier, 

 in June, 1 783, of the conclusions that Cavendish had come to, 

 would not have told Cavendish that Watt had come to those 

 conclusions at the latest in April, 1783 ? The conclusions are 

 identical, with the mere difference that Cavendish calls de- 

 phlogisticated air water deprived of its phlogiston, and that 

 Watt affirms water to be a union of dephlogisticated air and 

 phlogiston. 



We must remark that in Watt's theory there is the same 

 uncertainty, the same vagueness, which we have already ob- 

 served in that of Cavendish, and that it also proceeds from the 

 use of the term phlogiston, which was not well defined.* In 

 Cavendish we cannot decide whether phlogiston is merely in- 

 flammable air, or whether this chemist is not rather inclined 

 to consider a combination of water and phlogiston as inflam- 

 mable air. Watt says expressly, even in his Memoir of the 

 26th November, 1 783, . and in a passage that does not form 

 part of the April letter in 1783, that inflammable air, accord- 

 ing to his ideas, contains a small quantity of water and a great 

 deal of elementary heat 



These expressions from two such eminent men, should be 

 regarded as indicating a certain degree of hesitation, relative 

 to the composition of water. If Watt and Cavendish had had 

 a precise idea that water results from the union of two gases 



* In a note to his Memoir of the 26th of November, 1783 (p. 331), 

 vve read the following remark by Watt: " Anterior to Dr. Priestley's 

 experiments, Kirwan had proved, by some ingenious deductions bor- 

 rowed from other facts, that inflammable air is in all probability the 

 true phlogiston in an aerial form. Kirwan's arguments appear to me 

 perfectly convincing; but it seems more suitable to establish this point 

 of the question by direct experiments." 



