ij6 Analyfis of the Air. 



ceffion of cold air mud give a brisker motion 

 to the Fire, than the like fucceffion of hot 

 air : And fuch colder and more condenfed 

 air will alfo ( as Sir Ifaac Newton obferves, 

 qu. n.) by its greater weight check the 

 aicent of the vapours and exhalations of the 

 Fire, more than a warmer lighter air. So 

 that between the aftion and re-a&ionof the 

 air and fulphur of the fuel, and of the colder 

 and denfer cirumambient air, which rarifles 

 much upon entering the Fire, the heat of 

 the Fire is greatly increafed. 



This continual fupply of frefh air to the 

 fuel feems hence alfo very neceiTary for 

 keeping a Fire alive 5 becaufe it is found, that 

 a Brimftone Match will not take Fire ifi 

 avacunm> but only boil and fmoak; nor will 

 Nitre incorporated into Brown Taper then 

 detonize, except here and there a fmgle grain, 

 that part only of the Taper turning black 

 on which the focus of the burning glafs falls j 

 nor would they burn when a half exhaufted 

 receiver with fumes in it was filled with 

 frefh air added to thofe 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- 



quently 



