140 Remarks on Priestley’s Analysis 
flammable as ever. Not being able to succeed, { 
had recourse to the ingenuity of my friend Mr. 
William Henry. We repeated the experiment 
over mercury with no better success. I also kept 
the black oxyd of manganese, and the red oxyd of 
mercury in hydrogenous gas; expecting, that as the 
oxygen has a weaker attraction to these metals than 
to iron, it would more easily combine with the hy- 
drogen; but I was again disappointed. There 
cannot however be the least doubt of the truth of 
the facts mentioned by Dr. Priestley ; and I mean 
to make fresh attempts, and to acquaint the Society 
with their result if successful. In the mean time, 
is it not probable that the oxygen of the rust * 
combining with the hydrogen, formed water; and 
that, at the same time, a portion of azote, of which 
all metallic oxyds contain more or less (particularly 
those which have been exposed to the atmosphere) 
was disengaged? This conjecture is so much the more 
plausible, as it rests on well known phenomena. If 
it should be discovered that azote is not a simple 
substance, I cannot see what the doctrine of phlo- 
giston would gain by it. The phenomena of com- 
bustion and calcination in pure oxygenous gas, 
where no azote is produced, will still be inexplicable 
on that theory. 
