[ J 7* 1 



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 moil air, the heat muft be applied as fuddenly, 

 and as vehemently, as poffible. For, notwithftanding 

 the fame care be taken in luting, and in every other 

 refpect, 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 offensive fmell, from 

 whatever fubftance it be generated -, but this fmell is 

 of three difTerent kinds, according as the air is ex- 

 tracted from mineral, vegetable, or animal fubftances. 

 The laft is exceedingly fetid j and it makes no differ- 

 ence, whether it be extracted 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 



