254 LAVOISIER. 



communicated to the Royal Society in April, 1783: 

 there is even reason to think from his correspondence, 

 that it was formed earlier. Mr. Cavendish never gave 

 the least intimation of having drawn any such inference 

 from his experiment before April, 1783, when Mr. Watt's 

 letter was in the hands of the President of the Royal 

 Society, and was accessible to Sir Charles Blagden, one 

 of the Council. Mr. Cavendish's Diary of his experi- 

 ments has been carefully examined, and fac-siniiles 

 have been printed by Mr. Harcourt of all that relates to 

 the discovery ; not a word is to be found of the inference 

 or conclusion from the experiment, of a date prior to 

 April, 1783, when Mr. Watt's letter was in the hands of 

 the Society. It is certain that, whether he took the 

 theory from Mr. Watt or had formed it himself, he did, 

 previous to June, 1783, adopt and express the opinion 

 that his experiment shewed " dephlogisticated air to be 

 water deprived of its phlogiston/' Now this was, in the 

 language of the Stahl doctrine, holding that water was 

 formed by the union of phlogiston with dephlogisticated 

 air, a calx, as it were, of phlogiston. But Mr. Watt's 

 theory was, that phlogiston and inflammable air are 

 synonymous. Be this, however, as it may, the conclu- 

 sion contains the real doctrine of the composition of 

 water, how much disguised soever by the language of the 

 phlogistic theory; and that conclusion was communi- 

 cated, Sir C. Blagden says, "in summer, 1783," to M. 

 Lavoisier. His words are, "that he gave last summer 

 (1783) some account of Mr. Cavendish's experiments to 

 M. Lavoisier, as well as of the conclusion drawn from 

 them, that dephlogisticated air is only water deprived of 

 its phlogiston : but at that time so far was M. Lavoisier 

 from thinking any such opinion warranted, that till he 



