dvaly/is of the Air. 279 



This continual fjpply of frefh air to the 

 fuel, feems hence alfo very neceiTary for keep- 

 ing a Fire alive 3 becaufe it is found, that a 

 Brimftone Match will not take fire in a va- 

 cuum, but only boil and fmoke -, nor will 

 Nitre incorporated into Broun Paper then 

 detonize, except here and there a fingle grain, 

 that part only of the Paper turning black, on 

 which the focus of the burning-glafs falls ; 

 nor would they burn when a half-exhaufted 

 receiver with fumes in it was filled with frefii 

 air added to thofe fumes : In which cafe it 

 is plain, that a good quantity of the fup- 

 pofed vivifying jpirit of air mufl enter 

 the receiver with the frefh air, and confe- 

 quently thofe fubftances mould take fire, and 

 burn for a fhort time at leaft, which yet they 

 did not. 



And that the air's elafticity conduces much 

 to the intenfe burning of Fires, feems evident 

 from hence -, that Spirit of Nitre (which, by 

 Experiment 75, has but little elaftick air in 

 it) when poured upon live Coals, extinguishes 

 inftead of invigorating them : But Spirit of 

 Nitre, when by being mixt with Sar Tartar 

 it is reduced to Nitre, will then flame, when 

 thrown into the Fire, viz. becaufe Sal Tartar 

 abounds with elaftick aereal particle?, as ap- 



T 4 pears 



