GUMPOYVDER. lf>7' 



time. Now the increase of the weight being propor- 

 tioned to the quantity of vapour contained in the at- 

 mosphere, and to the length of time that the powder 

 is exposed to it, it follows, that powder easily attracts 

 moisture. Wherefore, if a degree of heat, sufficient- 

 only to fire dry powder, he applied to powder that is 

 damp, the moisture will oppose the action of the fire j 

 and the grains either will not take fire at all, or their 

 inflammation will be slower. Thus, as the fire will 

 spread more slowly, fewer grains will burn at a time; 

 and the penetration of the fire from the surface to the 

 centre of each grain, and, consequently, their con- 

 sumption, will require more time. Whence it may 

 be concluded, that all degrees of moisture diminish 

 the force of powder. Saltpetre, not sufficiently re- 

 fined, attracts moisture very readily; and as the sub* 

 stances that render it impure lessen the quantity of . 

 fluid, and prevent its detonation, it should be refined 

 as much as possible, before it is used in the fabrica- 

 tion of gunpowder. 



The force of powder is owing to an elastic fluid ge- 

 nerated at the explosion, the suddenness of which de- 

 pends upon the proportion of the ingredients, the 

 contact between the nitrous and combustible parti- 

 cles, and the size of the grains, &c. Hence it may 

 be concluded, that when several powders, equally 

 well dried, and fired under the same state of the at- 

 mosphere, are compared together, that which pro- 

 duces the greatest quantity of elastic fluid, in a given 

 space of time, is the strongest. 



