relailng to Air and 'IVu kr. £ 9 1 



In my laft communications to the Royal Society, it will be 

 ieen that I had tranfmitted the vapour of feveral fluid lub- 

 ftances through red-hot earthen tubes, and thereby procured 

 different kinds of air. M. Lavoisier adopted the fame pro- 

 cefs, but ufed an iron tube ; and by means of that circumliancc 

 made a very valuable difcovery which had efcaped me. I had 

 indeed on one occafion madeuie of an iron tube, and tranfmit- 

 ted fteam through it ; but not having at that time any view to 

 the production of alr^ I did net collect it at all, contenting 

 myfelf with obferving that ivater^ after being made -red-hot 

 was flill water, there being no change in Its fenfible properties. 

 Being now fartlier infl:ru6i:ed by the experiment of M. La- 

 voisier, I was determined to repeat the procefs with all the 

 attention I could give to it ; but I fliould not have done this 

 with fo much advantage, if I had not had the afliflance of Mr^ 

 Watt, who alway-s thought that M, Lavoisier's experi- 

 ments by no means favoured the conclufion that he drew fi'om 

 them. As to myfelf, I was a long time of opinion that his 

 conclufion was juft, and that the inflammable air w^is really 

 furnlfhed by the water being deconipofed in the procefs. But 

 though I continued to be of this opinion for fome time, the 

 frequent repetition of the experiments, with the lig;ht which 

 Mr. Watt's obfervations threw upon them, fatlstied me at 

 length that the inflammable air came principally from the cliar* 

 coal, or the iron. 



I fhall firfl: relate the refult of the experiment that was made 

 with charcoal^ and then thofe with iron and other fubftances, in 

 contad with which (when they were in a ftate of fufion, or at 

 leafl: red-hot) I made fleam, or the vapour of other liquid fub- 

 fiances, to pafs. I fhall only obferve that, previous, to this, I 

 began to make the experiments with coated glafs tubes, which 



P p 3 I found 



