relating to Air and Water , 
-of it v with a burning lens in vacuo, and thereby filled my 
receiver with nothing but inflammable air. 1 had no fufpiciori 
that the wet leather on which my receiver flood could have 
any influence in the cafe, while the piece of charcoal was fub- 
je£t to the intenfe heat of the lens, and placed feveral inches 
above the leather. I had alfo procured inflammable air from 
charcoal in a glazed earthen retort two whole days fucceflively, 
in which it had given inflammable air without intermiflion. 
Alfo iron filings in a gun-barrel, and a gun-barrel itfelf, had 
always given inflammable air whenever I tried the experiment. 
Thefe circumftances, however, deceived me, and perhaps 
would have deceived any other perfon ; for I did not know, 
and could not have believed, the powerful attraction that char- 
coal, or iron , appear to have for water when they are intenfely 
hot. They will find, and attract it, in the midft of the hotteft 
fire, and through any pores that may be left open in a retort ; 
and iron filings are feldom fo dry as not to have moifture 
enough adhering to them, capable of enabling them to give a 
confiderable quantity of inflammable air. But my attention 
being now fully awake to the fubjet, I prefently found that 
the circumftances above-mentioned had actually mifled me; I 
mean with refpecft to the conclufion which I drew from the expe- 
riments, and not with refpedt to the experiments themfelves, 
every one of which, I doubt not, will be found to anfwer, 
whenever they are tried by perfons of fufficient ikill and pro- 
perly attentive to all the circumftances. 
Being thus apprifed of the influence of unperceived moifture 
In the production of inflammable air, and willing to afcertain it 
to my perfect fatisfation, I began with filling a gun-barrel with 
Iron filings in their common ftate, without taking any parti- 
cular precaution to dry them, and I found that they gave air as 
Vol. LXXV. 
they 
