It has been calculated that one cubic inch of powder is converted into 250 cubic inches of gas at the temperature of the atmosphere, and Dr. Hutton states that the increase of volume at the moment of ignition cannot be less than eight times; therefore one inch of gunpowder, if confined, at the time of explosion exerts a pressure of about 30,000lbs. being 250 by 8 by 15 = 30,000lbs. on the cubic inch, or 5,000lbs. on the square inch; and which at once accounts for its extraordinary power. The value of the temperature to which the gases are raised, on the explosion of the powder, has been variously estimated and it may be concluded to rise as high as will melt copper, or 4,000° Fahrenheit. All gases expand uniformly by heat, the expansion having been calculated with great precision, to be ¹⁄₄₈₀th for each degree of Fahrenheit. If therefore we take Dr. Hutton’s calculations of one volume of powder expanding into 250 volumes of gas at the temperature of the atmosphere, and if we suppose 4,000° Fahrenheit to be the heat to which they are raised on ignition, the expansion of gunpowder would be calculated. Thus, suppose the gas to be at 60°, the temperature of the atmosphere, we must deduct 60° from 4,000°, which will give 3,940, being the number of degrees remaining to which it is raised, hence temp. vol. temp. vol. vol. 1 3940 1° : --- 3,940° : ---- = 8·2 480 480 that is, each volume of gas would at a temperature of 4000° be increased 8·2 in volume. Gunpowder when at the temperature of the air being expanded 250 times in volume; therefore 250 by 8·2 = 2,050 as the increased expansion for each volume of gas generated by the explosion of gunpowder at the temperature of 4,000° Fahrenheit. Lieut-Colonel Boxer calculates that the heat generated by good dry powder is not under 3,000° Fahrenheit. It appears with our present knowledge, the absolute value of the force of gunpowder cannot be determined. Still by careful and extensive experiments no doubt a near approximation to the truth may ultimately be arrived at, so that although much has already been done by various eminent philosophers, there is still more to be accomplished; and the importance of the subject ought to act as a stimulus to the exertions of those belonging to a profession the most interested in the question. ~Loss of velocity by windage.~ It has been found by experiments that in calculating the initial velocity of a projectile, one third of the whole force was lost with a windage of ¹⁄₁₀th inch with a shot of 1·96-in. and 1·86-in. in diameter. The bore of the gun being 2·02-in. ~Definition of ignition and combustion.~ By ignition we understand the act of setting fire to a single grain, or to a charge of gunpowder, and by combustion we mean the entire consumption of a grain or of a charge. ~Quickness of combustion.~