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 and the point 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 imperfectly. 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 below the cross-wires as above them—a most im portant point 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 are a great relief to the eye, which is disturbed by irregular light on ordinary sights.
Small guns, 6-pounders and less, have small, light mounts, called cage stands. They are like pedestal mounts, but simpler, though fully ade quate to their purpose. Rail mounts consist of sockets bolted to the rail or upper works of a ship in which fit the stalks of the top-carriages of light guns. Mounts for light guns in military tops run on a rail inside the top-rail, and the force of the recoil is received by a clamp extend ing over the top-rim.
Turret mounts are by far the most complicated of any fitted in ships. For small guns they differ chiefly in the ammunition hoist and training mechanism, which latter is necessarily effected by means of a motor—electric, steam, hydraulic, or compressed air—as the whole turret and contents turn when the gun is trained. In turrets for large guns the size of the guns entails numerous special appliances. The shell and powder-charge made in short lengths separated froi each other by disks, which are free to move with the springs. The ammunition car, hoisted by a wire rope, the motive power usually electric, carries an entire round—powder and projectile. It is stopped in
rear of the open breech and the shell, and then the powder pushed in by a sectional rammer, also operated by electricity. The training is done by a turret trainer in the central or forward hood (an armored lookout large enough for the head and shoulders, and rising about a foot above the top of the turret) who attends to nothing else but keeping the guns directed to the proper part of the enemy's vessel, following the directions of the turret officer. The gun-firers are in the side hoods. Each has controlling mechanism for ele vating his own gun and the sight, which in our are both too heavy to handle, and power appli ances are necessary, not only for hoisting them up from below, but for loading them into the gun. Nevertheless, in the getteral arrangement of recent turret mounts much has been borrowed from the lighter deck types. The gun is generally balanced on extensions (called projecting from the trunnions which are shaped like Vs, the sharp edge (not very sharp by the way) rest ing on a bard steel bar. The latter is supported at the ends, and gives sufficiently. when the gun is fired, for the trunnions to drop .02 of an inch and bear against the heavy trunnion seats. As the gun is normally supported on the knife-edges and is quite accurately balanced on them, it is easily elevated and depressed by hand gear. The recoil is taken up by four recoil cylinders equally spaced about the gun and containing pistons working in a mixture of SO per cent. glycerin and 20 per cent. water; the cylinders also contain the heavy counter-recoil springs naval service is invariably of the telescopic type and carried on a side arm which is given the proper direction by a system of parallel motion connecting with the trunnions of the gun-slide. The magazines and shell-rooms are grouped about the base of the turret shaft leading below, and are fitted with shell and powder trolleys for bringing am mu nit ion to the ammunition ear when it is down; and the men handling the am munition are under the orders of the turret officer.