WATT. 391 



refers to it, as having set him upon making his experiments. 

 (Phil. Trans. 1784, p. 126.) The experiment of Mr. Warltire 

 consisted in firing, by electricity, a mixture of inflammable 

 and common air in a close vessel, and two things were said to 

 be observed : first, a sensible loss of weight ; second, a dewy 

 deposit on the sides of the vessel. 



Mr. Watt, in a note to p. 332 of his paper, Phil. Trans. 

 1784, inadvertently states, that the dewy deposit was first 

 observed by Mr. Cavendish; but Mr. Cavendish himself, 

 p. 127, expressly states Mr. Warltire to have observed it, and 

 cites Dr. Priestley's fifth volume. 



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 measures of the former to 

 4'23 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 inflammable air, and about one-sixth of 

 the common air, are turned into pure water." 



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

 cated 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 inflammable 

 and dephlogisticated air is converted into pure water;" and, 

 again, that ' ' if these airs could be obtained perfectly pure, the 



It seems evident that neither Mr. Warltire nor Dr. Priestley 

 attributed the dew to anything else than a mechanical deposit of 

 the moisture suspended in common air. [NOTE BY MB. JAMES 

 WATT.] 



* 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.] 



