PACKAGE, AND STOWAGE OF SMALL STORES. STOWAGE OF SMALL STORE BOX-GUN. Same exactly for 6, 9, 12, and 24 Pounders, with the slight exception STOWAGE OF SMALL STORE BOX-WAGGON. Same exactly for the 6, 9, 12, and 24 Pounders. STOWAGE OF IMPLEMENTS, AND SMALL STORES, SHOWING WHERE PART XI. GUNNERY. By the Parabolic Theory, the greatest range is when the angle of elevation is 45°, or half a right angle; and the ranges are equal at angles, equally above, and below 45°. In projectiles, moving with velocities not exceeding 300 or 400 feet per second of time, the Parabolic theory will resolve cases tolerably near the truth; but in cases of great projectile velocities, that theory is quite inadequate, without the aid of data, drawn from good experiments; for so great is the effect of the resistance of the air to projectiles of considerable velocity, that some of those, which in the air range only two or three miles, would, in vacuo, range between twenty and thirty miles. The effects of this resistance are also various, according to the velocity, the diameter, and the weight of the shot. By experiments it will be found that the greatest range (instead of being constantly that at an elevation of 45°, as in the Parabolic theory), will be at all intermediate degrees between 45° and 30° (with ordinary charges about 42°), being more, or less, both according to the velocity, and the weight of the projectile; the smaller velocities, and larger shells ranging farthest when projected almost at an elevation of 45°; while the greatest velocities, especially with the smaller shells, range farthest with an elevation of about 30°. However, as sufficient experiments have not yet been made to establish true rules for practical gunnery, independent of the Parabolic theory, we must at present content ourselves with the data of some one certain experimental range, and time of flight at a given angle of elevation, and then, by help of these, and the Parabolic theory, we can determine the like circumstances for other elevations that are not greatly different from the former, assisted by the following rules: PRACTICAL RULES IN GUNNERY. 1.-To find the Velocity of any shot, or shell. It has been found by experiments, that with shot of mean windage, and powder of mean strength, a charge of one-third of the weight of the ball gives an initial velocity of about 1600 feet per second: therefore, to find the velocity given by any other charge, divide three times the weight of the charge by the weight of the ball, and multiply the square root of the quotient by 1600, the product will be the velocity in feet, or the space the shot passes over in the first second.* By the ballistic experiment, conducted in May, 1837, it was found that, with a heavy 6-pounder gun, a charge of 14 lb. gave a velocity of 1740 feet, 2. The first graze, with given elevation, and charge, being known, to determine the Charge for any other first graze, and elevation. Multiply the known charge, and elevation into the proposed first graze, also the proposed elevation into the known first graze, and divide the first product by the last, for the charge required in ounces. 3. Given the range for one charge, to find the Range for another charge, or the Charge for another range. The ranges have the same proportion as the charges; that is, as one range is to its charge, so is any other range to its charge, the elevation of the piece being the same in both cases. From Experiments on the velocities of shot, the following results have been obtained : 1. The time of a ball's flight is nearly as the range, the gun, and elevation being the same. 2. The velocities decrease as the distances increase (arising from the resistance of the air, which opposes the progress of the shot,) in a proportion somewhat higher than the squares of the velocities throughout, and subject only to a small variation. 3. Very little advantage is gained, in point of range, by increasing the charge more than is necessary to attain the object, the velocities given by large charges being very soon reduced to those by moderate charges; those, for instance, given by half the shot's weight are reduced to an equality with those by one-third, after passing through a space of only 200 feet. (Vide 8.) 4. Very little benefit is derived from increasing the length of guns, the velocity given by long guns of 22 calibres being reduced to an equality with that of short guns of 15 calibres with similar charges, after passing through the following spaces-viz.: 5. The resistance of the air against balls of different diameters with equal velocities, is very nearly in the proportion of the squares of their diameters, or as their surfaces. and a charge of 2 lb. a velocity of 1892 feet per second. The shot employed were of a high gauge, windage only 078 inch, and the powder was of the strongest quality; the weight of the pendulum fired into was 58 cwt. 3 qrs. 16 lb. A light 6-pounder, two feet shorter than the heavy 6-pounder, with similar charges, gave velocities of about 190 feet less. |