288 Dr. Priestley’s Experiments and Obfervations 
Having had this fuccefs with the calx, or fcales of iron, I 
tried the calx of copper , or thofe fcales which fly from it when 
it is made red-hot ; and I found water produced in the inflam- 
mable air in the fame manner as when I ufed the fcales of iron 
in the fame circumftances. I alfo had the fame refult when I 
revived precipitate per fe in inflammable air; but having at that 
time a very weak winter’s fun, I could not make the experi- 
ment with fo much advantage as I could have wifhed. 
Iron, I found, acquired this additional weight by melting 
in an earthen retort, as well as in the open air by the fun- 
beams, if it were poffible for it to attrad air, or whatever elfe 
it is that is the immediate caufe of its additional weight. 
Three ounces of common iron flings, expofed to a ffrong heat 
in an earthen retort, gained 1 1 dwts, or 264 grains, and yet 
was very far from having been completely fufed. Having a 
glafs tube communicating with the retort, in order to colled’ 
any air that the iron filings might give out, I found that when 
they were very hot, the water afcended within the tube ; which 
ihews that the iron was then in a fate of absorbing, and not 
of giving out any air. 
Seeing fo much water produced in thefe experiments with 
inflammable air, I was particularly led to refled on the relation 
which they bore to each other, and efpecially to Mr. Caven- 
dish’s ideas on the fubjed. He had told me that, notwitH- 
ftanding the experiments of which I had given an account to 
the Royal Society, and from which I had concluded that in- 
flammable air was pure pjilogiflon, he was perfuaded that water 
was effential to the produdion of it, and even entered into it 
as a conftituent principle. At that time I did not perceive the 
force of the arguments which he flated to me, efpecially as, in 
the experiments with charcoal, I totally difperfed any quantity 
of 
