THE PROPERTIES

24

burn; and the penetration of the fire from the surface to thecentre of each grain, and consequently their consumption,will require more time. Whence it may be concluded, thatall degrees of moisture diminish the force of powder. Salt-petre, not sufficiently refined, attracts moisture very readily;and as the substances that render it impure lessen the quan-tity of fluid, and prevent its detonation, it should berefined as much as possible before it is employed in the fabri-cation of gun-powder.

66. In drying damp powder, the degree of heat should bemoderate. (63.) When any of the saltpetre has been dissolved,it should be ground afresh, to establish a just mixture of theseveral ingredients ; and if part of it be absolutely lost, whichmay be known by passing a certain quantity of the powder,well dried and weighed, through a sieve, it will be necessary,before it is ground, to add the quantity of saltpetre that isdeficient.

67. Having thus shewn that the force of powder is owingto an elastic fluid generated at the explosion, the suddennessof which depends upon the proportion of the ingredients, thecontact between the nitrous and combustible particles, andthe size of the grains, &c. it may be concluded, that whenseveral powders, equally well dried, and fired under the samestate of the atmosphere, are compared together, that whichproduces the greatest quantity of the elastic fluid, in a givenspace of time, is the strongest.

CHAP. IV.

The Properties of Powder are the samein Fire-Arms of all Calibres.

68. Having proved that every degree of heat is

not capable of firing powder, and that its force depends onthe elastic fluid generated at the explosion, it is needless toadduce any more arguments in support of this fact 5 butwith regard to the second and third properties (44, 48, 49.)of powder, which are undoubtedly of greater consequence,and have often, for want of due investigation, occasioned adifference of opinion among artillerists, in treating of theproper charge and length of guns, it is necessary to be more

particular.