11 



of the arguments which he stated to me, especially as, in the experi- 

 ments with charcoal, I totally dispersed any quantity of it with a burn- 

 ing lens, ill vacuo, and thereby filled my receiver with nothing but in- 

 flammable air. I had no suspicion that the wet leather on which my 

 receiver stood could have influence in the case, while the piece of char- 

 coal was subject to the intense heat of the lens, and placed several 

 inches above the leather. I had also procured inflammable air from 

 charcoal in a glazed earthen retort two whole days successively, in 

 which it had given inflammable air without intermission : also iron 

 filings in a gun-barrel, and a gun-barrel itself had always given in- 

 flammable air whenever I tried the experiment." " But, my attention 

 being now fully awake to the subject, I found that the circumstances 

 above mentioned had actually misled me." " Being thus apprised of the 

 influence of unperceived moisture in the production of inflammable 

 air, and willing to ascertain it to my perfect satisfaction, I began with 

 filling a gun-barrel with iron filings in their common state, without 

 taking any precaution to dry them, and found that they gave air as 

 they had been used to do ;" " at length however, the production of in- 

 flammable air from the gun-barrel ceased, but on putting water into it, 

 the air was produced again ; and a few repetitions of the experiment 

 fully satisfied me that I had been too precipitate in concluding 

 that inflammable air is pure phlogiston." Dr. Priestley afterwards 

 gives an account (Phil. Trans. 1785) of his repeating Lavoisier's 

 celebrated experiment, in which the decomposition of water was 

 proved by passing steam through an iron tube. " I was determined," 

 he says, " to repeat the process with all the attention I could give 

 to it ; but I should not have done this with so much advantage if 

 I had not had the assistance of Mr. Watt, who always thought 

 that M. Lavoisier's experiments by no means favoured the conclu- 

 sion that he drew from them. As to myself, I was for a long time 

 of opinion that his (Lavoisier's) conclusion was just, and that the in- 

 flammable air was really furnished by the water being decomposed 

 in the process ; but though I continued to be of this opinion for some 

 time, the frequent repetition of the experiments, with the light which 

 Mr. Watt's observations threw upon them, satisfied me at length, that 

 the inflammable air came from the charcoal or the iron." 



It appears from these statements, and may be still more clearly ga- 

 thered from Cavendish's own remarks * in his " Experiments on Aii-," that 

 he not only set Priestley right as to his supposed fact of the production 



* Phil. Trans, vol. Ixxiv. p. 137. 



