48 the force of

accuracy in the construction of the machines. In calculatejng effects steel ucible from physical causes, a precise solutionps the problem can never be obtained; it is always com-prised within limits more or less distant from the absolutetruth, in proportion to the number os causes that conduce tothe lame effect. Consequently in measuring the force ofpowder tired for military purposes, no precision can possiblybe expected ; and from the nature and number of adventi-tious circumstances, the limits that comprehend the solutionof the problem must necessarily vary ; sometimes even a ge-neral principle will be only applicable to particular cafes. Be-sides, as artillerists frequently prefer observations drawn frompractice to rules deduced from theory, it is necessary to dividethe problem into distinct parts, and consider each of the con-ditions separately, in order to combine as much as possibletheory with practice; In the course of this examination we(hall prove, that this combination is in all cafes advantageous,in some indispensable.

These preliminary remarks lead to the subject of the chap-ter. Since the inflammation of the grains, and the total de-struction of each is effected successively, and in a time pro-portionate to the quality of the powder, the size of the grains,&c. and since on the other hand the force of powder dependsprincipally on a permanent fluid generated at the explosion,the elasticity of which is increased by the presence of fire: itfollows that this force increases continually from the instantthat the inflammation commences, till all the powder beconsumed, and then is quickly reduced by the decrease ofheat, to the simple elasticity of the permanent fluid. Thereis then a period when .the degree cf heat is most iiitense ;but this varies even in powder of the fame quality, whenfired under st,ff. rent circumstances. As no general andconstant law can therefore be established, we must be con-tent with ascertaining the greatest degree of force in parti-cular cases ; which founded on certain data, may be usefullyapplied to the various services of artillery. But that noneof the most material points involved in the solution of thisproblem may be passed over in silence, nor any vain hypo-theses and chimerical suppositions formed ; let us in the firstplace examine the force of powder in its most simple slate,that is, when reduced by the temperature of the air, to theelasticity only of the permanent fluid, and afterwards in itsmost complex state, that is to fay, at the instant of explosion,

CHAP,