thap. 6.J 



which brings a fupply of pure air to unite with the 

 inflammable matter contained in the coal. 



The inflammable and pure air, which are apparently 

 confumed by the procefs of combuftion, are in reality, 

 by their union, converted into water, as will be evinced 

 by fixing an alembic head, or any good recipient, to 

 the top of Mr. Argand's lamp, in which a quantity of 

 water will prefently be found, but no foot. 



There are, however, certain fubilances, fbch as 

 gunpowder, &c. which will burn with a very fmall 

 fupply of air, as when included within the barrel of a 

 gun, and cloiely wadded. To explain this, it mufc be 

 premifed, that nitre, or fome of the ingredients of fuch 

 compofitions, contains a large quantity of the bafis of 

 pure air : and it mud be remembered, that air confifts 

 of a certain matter or bafis, which is expanded by a 

 union with the matter or element of fire, but which is 

 alfo capable of exifting in a more condenfed ftate. 

 Let it alfo be remembered, that though air, which is 

 a compound body, will not penetrate metallic fub- 

 ftanees, yet the element of fire, or caloric, will pene- 

 trate them, or any other fubftance with which we are 

 acquainted. One of the ingredients of air, therefore, 

 is contained in the nitre or gunpowder, and the other 

 (the fire or caloric) cannot be excluded. When there- 

 fore the matter or elementary part of the air, is fet 

 free from the nitre by accenfion, it immediately meets 

 with the matter of heat or fire, and becomes embodied 

 into the form of air, and thus an adual fupply of that 

 material is generated, though the air of the atmofphere 

 h nearly excluded *. 



According 



* Gunpowder is a mixture, which in an hundred parts contains 

 about 75 of nitre, 9! of fulphur, and 1 5f of charcoal. The effects 

 f gunpowder depend on the fudden production of a quantity of 



VOL. L L ir > 



