On the nature and component parts of Gunpotvder, and the quantity 

 of' air produced by its explofton : together ivith the Author s fen- 

 timents refpeSing the Jize of great Guns, and his ohfervations on 

 condenjed and rarifed Air. 



It has long been my opinion, that all the faline particles which 

 by the force of fire are elevated or driven upwards, from different 

 fubflances, muff be of a globular figure ; becavife by the fire they are 

 rendered foft, and are driven about with a very quick motion; in 

 which opinion T was confirmed by recolleding the ohfervations I had 

 formerly made on Gunpowder. And now, to repeat thofe experiments, 

 I provided feveral glafs veflels, which I made as clean as if they had 

 newly come out of the glafs-houfe ; fome of thefe as deep as the 

 breadth of three fingers, others of four, and others of fix. Thele I 

 heated, in order to expel from them all the moifl air of the atmof- 

 phere which we experience in this country in the autumn, and to 

 introduce in its place a more rarified or thinner air than that in 

 which we breathe. In a glafs fo prepared, 1 placed one or more 

 of the largell: grains of Gunpowder, flopping the glafs fo clofely as 

 to exclude all the moifl atmolpheric air ; and I then applied to that 

 part of the glafs where the Gunpow^der lay, a fufficient degree of 

 heat to fire the Powder. Hereupon the glafs appeared filled with 

 a kind of white fmoke, in which could be feen, both at the bottom 

 and fides of the glafs, the * charcoal and fulphur, which had en- 

 tered into the compofition of the Gunpow'der. When, in this 



* It is generally known (hat Oiinpowdor i» compof'd of fa!tpetre, fiilpliur, and charcoal, 

 ill tho propo.'.ons of thrcc-fouiihs falipoiru, one eighth fiilplinr, and one eighth cliarcoal ; 

 the whole well pounded and mixed together, and afterwards prepared for ufe in the form of- 

 fmall grains, rcfcmbling feed?. 



