s-4-6 Combuftion without Flame. [Book VI. 



oxygen to decompofe vital air, they lofe their inflam- 

 mability. According to the old chemical doctrine, 

 the heat and Jight afforded by inflammable fubftances 

 were fuppofed to derive their origin from the difen- 

 gagement of phlogiftcn j but, according to the doc- 

 trine of M. Lavoifier, the vital air of the atmofphere 

 is the repofitory of light and heat, from which all ar- 

 tificial fupplies are derived, by means of inflammable 

 fubftances. 



There is one ftriking difference among inflammable 

 fubftances, which is, that fome burn with and Ibme 

 without flame. Of .the former kind are oils, fpirit 

 of wine, and moft others ; to the latter kind belong 

 the different fpecies of charcoal. The caufe of this 

 difference is, that fome inflammable bodies afford an 

 inflammable vapour, the burning of which produces 

 flame; others are entirely fixed, and produce no fuch 

 vapour. The vapour, however, as it rifes is not wholly 

 confumed ; the reafon of which is, that the air does not 

 find accefs to the, center of the column of vapour as was 

 formerly explained. In large flames, the furface on which 

 the air acts is lefs in proportion to the quantity of vapour 

 than in fmall flames ; hence the quantity of fmoke and 

 foot produced by fmall flames is proportionably lefs 

 than that produced by large ; for fmoke and foot are 

 only that part of the vapour which is unconfumed. 



In treating of inflammable fubftances it will be ne- 

 cefTary to confine the inquiry to thofe which poffefs 

 that property in a more remarkable degree. I fhall, 

 therefore, firft treat of the fimple inflammable fub- 

 . fiances, phofphorus, fulphur, and coal, or the carbon 

 of the French philofophers. Hydrogen, or inflam- 

 mable air, has already been defcribed under the liecid 

 of elaftic or aeriform fluids. With refpect to the 



compound 



