new inflammable Air or Gafs , See. 397 
Inflammable air, the gas flarnmeum of van helmont, 
was confldered as an aerial fluid, lufceptible of inflam- 
mation by itfelf. 
But we now know, that inflammable gas concentrated 
will not burn at all; but on the contrary extinguifhes 
flame. Mr. cavendish was the firft who fet this matter 
in a proper light. He difeovered, by experiments, that a 
mixture of a fmall quantity of common air with a great 
proportion of inflammable air, as, for inftance, two parts 
of common air with eight parts of inflammable air, 
caught, fire without noife, and confumed gradually; but 
that three parts of inflammable air and feven parts of 
refpirable air exploded with a very loud found. 
It was Dr. Priestley’s important dilcovery which 
fuggefted to me the theory I intend to lay before the 
Royal Society. 
This acute philofopher found, that, if inftead of com- 
mon air, dephlogifticated air is mixed with a due propor- 
tion of inflammable air, the explofion is confiderably 
louder. 
The principal ingredients of gunpowder, and thofe to 
which it owes its force, are nitre and charcoal; for thefe 
two ingredients, well mixed together, conftitute gun- 
powder at leaft equal if not fuperior in ftrength to com- 
mon gunpowder (as I found by experience, and may be 
Vol. LXIX. G >j .a; feen 
