552 PHILOSOPHICAL TRANSACTIONS. [aNNO 1779. 



difficult undertaking. The expansion of" the moisture always contained in gun- 

 powder, however dry, may also contribute its share towards the amazing powers 

 of this ingredient. Nitre contains from its nature a great share of water, which 

 is necessary for its crystallization, and charcoal is always found to contain it. 

 We know, that very hot vapour is capable of occupying almost 2000 times the 

 space it did in the state of cold water. The generation of dephlogisticated and 

 inflammable air by the inflammation of gunpowder is the reason why this ingre- 

 dient is almost the only one known, which does not want a free access of com- 

 mon air to be consumed by fire; and therefore it may be said to feed, as it were 

 on its own air. 



This theory of gunpowder induces me to venture a new one of thepulvis ful- 

 minans, which consists of 3 parts of nitre, of 2 of fixed alkaline salt, and of 1 

 of sulphur. This powder much surpasses the force of gunpowder in exploding, 

 with a very loud report, in the open air, when it is heated to a certain degree. 

 It is commonly said, that in the heating of this powder the sulphur joins with 

 the alkaline salt and constitutes an hepar sulphuris, which rising up in bubbles 

 confines the air contained in them, which air at last becomes so powerfully ex- 

 panded that it overcomes and breaks through the resistance of the coercive bubbles 

 of the hepar sulphuris, with all the force of its elasticity; which sudden emer- 

 sion must naturally occasion a proportionable sound. But I think, that the nitre 

 contained in this powder, being heated, yields its dephlogisticated air when the 

 melting sulphur yields inflammable air; at the same time the sulphur constitutes 

 with the alkaline salt, an hepar sulphuris, which rising in tough bubbles confines 

 this explosive air generated. At length however the increasing heat, which sets 

 fire to the sulphur, sets this explosive air on fire also; which then, following its 

 own nature, explodes with so much the more force from its having been entangled 

 and confined within the bubbles of the hepar sulphuris. 



After what has already been said, it will not be difficult to explain, why a 

 single spark of fire propagates the combustion with great rapidity through the 

 whole mass of gunpowder, however great. If we put a single grain of gun- 

 powder on a red-hot iron, we see the particles of red-hot charcoal projected with 

 great rapidity in every direction by the forcible explosion of the 2 airs extricated 

 in the manner before explained. Thus, if 1 or more grains, among a heap of 

 others, are set fire to, the particles of red-hot charcoal, being driven with great 

 violence against the surrounding grains, communicate their heat to all the par- 

 ticles of charcoal they hit, which particles, by heating the particles of nitre in 

 close contact with them, extricate their dephlogisticated air, at the same time 

 that the charcoal yields its inflammable air ; in consequence of which a more 

 powerful exj)losion happens. This secondary explosion projects with a much 

 greater force the particles of charcoal surrounded by the explosive flame of" the 2 

 airs; and thus the conflagration spreads with a very great veloeity through the 



