Page:The New International Encyclopædia 1st ed. v. 09.djvu/434

* GUNS. 384 GUNS. into use. and theso were so much more compli- laterl that the tonii numnt began to be applied to them as well as I(j llie 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 during 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 nunuits is almost in- variably performed by hand, though the annnuni- tion is generally hoisted from below by electric or hand ammunition boists. 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 1.3 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, 1. .sniE VIEW. PEDEST,VL MOUXT. MARK VU., FOR 6-l.CH BREECB-LOADING RIFLE. .IAIIK For key to iiiinibpr?, see seetinual Jrawinj^. UNITED STATE.'^ NAVY. coil and counter-recoil cylinders, and sighting nieehanisni. The gun recoils through the sleeve which is cast in one with the cylinders; tbe.se latter have pistons connected by rods to a band around the gun; inside the pistons are heavy count«r-recoil springs and a liquid consisting of glycerin, 80 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 <'ylinders. The water pres- sure gradiuilly 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) Iieing only a fraction of a second. The elevating and training are effected by hand- wheels driving shafts connected to cogged racks or worm gearing, the perfect balance of parts and the ball-bearings rendering very little power necessary to train or elevate rapidly. The load- aiul the ))oint aimed at all in the same line; the three objects are all at different distances, and the eye sees them all imperfectly or else one per- fectly and the others imperfeetiy. The result is defective shooting. In the telescope sight the cross-wires are at the optical focus, and the image of the object aimed at is also formed there so that the eye is not straining to adjust itself to several focal lengths simultaneously. Further- more, the object aimed at is seen as well when l.clow the cross-wires as above them — a most im- liortant piunt when the ship is rolling. The prin- cipal objections urged against telescope sights are their fragility and the ease with which they may be thrown out of adjustment. Ten years' use in the United States Navy does not sustain the validity of these objections. Furthermore, for use in dark turrets or bright sunlight, they arc a ffreat relief to the eve. which is disturbed by irregular light on ordinary sights. Small guns, (i-puunders and less, have small, light mounts, culled cage stands. They are like