

Ij6 Anatyfis of the Air. 



ccifion of cold air rnuft give a brisker motion 

 to the Fire, than the like fucceflion of hot 

 air : And fueh colder and more condenfed 

 air will alfo (as Sir Ifaac Newton obferves, 

 qu. i i . ) by its greater weight check the 

 afcent of the vapours and exhalations of the 

 Fire, more than a warmer lighter air. So 

 that between the action and re-a&ionof the 

 air and fulphurof the fuel, and of the colder 

 and denfer cirumambicnt air, which rarines 

 much upon entering the Fire, the heat of 

 the Fire is greatly increafed. 



This continual fupply of frefh air to the 

 fuel fcems hence alfo very neceflary for 

 keeping a Fire alive 5 becaufe it is found, that 

 a Brimftone Match will not take Fire in 

 avacitum, but only boil and fmoak; nor will 

 Nitre incorporated into Brown Taper then 

 dctonizc, except here and there a fmgle grain, 

 that part only of the Taper 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 

 frefh air added to thofc fumes: In which 

 cafe it is plain, that a good quantity of the 

 fuppofed vivifying fpirit of air muft enter 

 the receiver with the frefh air, and confe- 



i . qucntly 



pot 

 rfacn 



to 



MB 





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