[ 1 7 1 3 
a tobacco pipe, and to the end of this I tied a flaccid 
bladder, in order to catch the generated air. 
There is not, I believe, any vegetable or animal 
fubftance whatever, nor any mineral fubftance, that 
is inflammable, but what will yield great plenty of 
inflammable air, when they are treated in this man- 
ner, and urged with a ftrong heat ; but, in order to 
get the moll air, the heat mull be applied as fuddenly, 
and as vehemently, as poffible. For, notwithffanding 
the fame care be taken in luting, and in every other 
refped, fix or even ten times more air may be got 
by a fudden heat than by a flow one, though the 
heat that is laft applied be as intenfe as that which 
was applied fuddenly. A bit of dry oak, weighing 
about twelve grains, will generally yield about a 
fheep’s bladder full of inflammable air with a brifk 
heat, when it will only give about two or three ounce 
meafures if the fame heat be applied to it very 
gradually. To what this difference is owing, I can- 
not tell. 
Inflammable air, when it is made by a quick pro- 
cefs, has a very ftrong and offenfive finell, from 
whatever fubftance it be generated j but this fmell is 
of three different kinds, according as the air is ex- 
traded from mineral, vegetable, or animal fubftances. 
The laft is exceedingly fetid; and it makes no differ- 
ence, whether it be extraded from a bone, or even 
an old and dry tooth, or from foft mufcular flefh, or 
any other part of the animal. The burning of any 
fubftance occafions the fame fmell : for the* grofs 
fume which arifes from them, before they flame, 
is the inflammable air they contain, which is expelled 
by heat, and then readily ignited. The fmell of in- 
Z 2 flammable 
