58 WATT. 



Mr. Cavendish himself could find no loss of weight, and 

 he says that Dr. Priestley had also tried the experiment, 

 and found none.* But Mr. Cavendish found there was 

 always a dewy deposit, without any sooty matter. The 

 result of many trials was, that common air and inflammable 

 air being burnt together, in the proportion of 1000 meas- 

 ures of the former to 423 of the latter, " about one-fifth of 

 the common air, and nearly all the inflammable air, lose 

 their elasticity, and are condensed into the dew which lines 

 the glass." He examined the dew, and found it to be pure 

 water. He therefore concludes, that " almost all the in- 

 flammable air, and about one-sixth of the common air, are 

 turned into pure water." 



Mr. Cavendish then burned, in the same way, dephlogis- 

 ticated and inflammable airs (oxygen and hydrogen gases), 

 and the deposit was always more or less acidulous, accord- 

 ingly as the air burnt with the inflammable air was more or 

 less phlogisticated. The acid was found to be nitrous. Mr. 

 Cavendish states, that " almost the whole of the inflam- 

 mable and dephlogisticated air is converted into pure water;" 

 and, again, that " if these airs could be obtained perfectly 

 pure, the whole would be condensed." And he accounts 

 for common air and inflammable air, when burnt together, 

 not producing acid, by supposing that the heat produced is 

 not sufficient. He then says that these experiments, with 

 the exception of what relates to the acid, were made in the 

 summer of 1781, and mentioned to Dr. Priestley ; and adds, 

 that "a friend of his (Mr. Cavendish's), last summer 

 (that is 1783), gave some account of them to M. Lavoisier, 

 as well as of the conclusion drawn from them, that dephlo- 

 gisticated 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 was prevailed upon to 

 repeat the experiment himself, he found some difficulty in 

 believing that nearly the whole of the two airs could be 

 converted into water." The friend is known to have been 

 Dr., afterwards Sir Charles Blagden ; and it is a remarkable 

 circumstance, that this passage of Mr. Cavendish's paper 



* Mr. Cavendish's note, p. 127, would seem to imply this ; but I have 

 not found in any of Dr. Priestley's papers that he has said so. [Note by 

 Mr. James Watt.'} 



