MOUNTS FOR NAVAL GUNS.
Mounts for naval gnus are of three types, tur ret, deck, and rail. The principal features of mounts are the method of checking recoil. re turning the gun to the firing position after recoil. elevating, training, sighting, and loading. Up to the middle of the nineteenth century naval guns were mounted upon simple wooden carriages with heavy side frames or timbers supporting the side; the length of the breech was sufficient to allow the gun to recoil several feet, and this not only reduced the strain on the breeching, but also allowed the gun to come in far enough so that it was easily loaded. After loading, the gun was run out and trained by tackles. Some guns were pivoted amidships, and these had a lower struc ture mounted on trucks called a slide, on which the gun-carriage slid during recoil. The re coil was taken up by breeching secured to the slide, and the strain transferred to the deck by means of a pivot belt. The broadside mount-: or carriages continued in favor until the Civil War. when the turret system was established by the Modifications of the old carriages were still used on the broadside, though they had begun to be made of iron and brass. The increased size of ships, however. caused the pivot carriages to be fitted for shifting from side to side, and the convenience of training them resulted in the so-called muzzle-pivot carriage, which was only the old pivot carriage fitted with an arm at the forward end pivoted at the ship's side. About 18S5 the central-pivot carriages were brought into use, and these were so much more compli cated that the term mount began to be applied to them as well as to the fittings of the turret guns. The central-pivot carriage was very heavy and clumsy, however, and it was displaced some eight or ten years later by the pedestal mount, which had the further advantages of returning the gun to the firing position by the use of heavy springs compressed (luring recoil and of permitting the gun to pivot close out to the side. Improved pedestal mounts are still in general use for guns carried on deck, and there seems to be no im mediate prospect of their being displaced. The
latest one consists of a heavy casting called the pedestal, bolted to the deck; a top-car riage resting on cone-shaped rollers or balls working in a roller path on the pedestal; an oscillating sleeve with trunnions on the sides resting in trunnion sockets on the top-carriage; lastly. elevating and training gear, combined re ing of guns on pedestal mounts is almost in variably performed by hand, though the ammuni tion is generally hoisted from below by electric or hand ammunition hoists. In the United States Navy all guns of 4-inch calibre and larger are fitted with telescope sights, and have been so fitted for years, but in other navies the telescope is just beginning to be appreciated. It is about 15 inches long with an object glass about 2 inches in diameter. The magnifying power is not great—only about two diameters—but the real gain is not in this direction..Ordinary bar sights consist of a fixed, pointed bar on the trun nion, and a bar on the breech with a notch in the top. The rear sight-bar can be moved up and down in its sight-box in order to adjust it to the elevation corresponding to the desired range (for which the bar is marked on the side). To take sight on the object it is necessary to bring the rear sight notch, the tip of the front sight, coil and counter-recoil cylinders, and sighting mechanism. The gun recoils through the sleeve which is cast in one with the cylinders; these latter have pistons connected by rods to a band around the gun; inside the pistons are heavy counter-recoil springs and a liquid consisting of glycerin, SO per cent., and water, 20 per cent. As the gun recoils the liquid escapes past the piston-head in small grooves, decreasing in depth from front to rear, which are cut in the inner surface of the cylinders. The water pres sure gradually brings the gun to rest, the pres sure of the springs assisting. As soon as the re coil is checked the springs return the gun quickly to the front, the total time of recoil and return to firing position (or to battery, as it is called) being only a fraction of a second.