All the four spiral firing springs can be taken out, without opening the rest of the mechanism, in 1-1/2 seconds. All the parts of the mechanism are made interchangeable, so that reserved parts can at any time be substituted. The gun can be placed on half cock, so that the strikers do not act; and for further security the lever can be locked. The carrier block, without which the gun cannot be fired, is loose, and can be taken away, in case it becomes necessary to abandon a gun, which is thus made useless to the enemy. The bullets are solid steel, weighing about 1/2 lb. At 1760 yards at right angles this gun will penetrate a 3/16 inch steel plate, which represents the thickness of the plates of a torpedo boat. At 200 yards at right angles it will penetrate one 3/16 inch steel plate placed in front of a 1/2 inch steel plate with a space of 3 feet between them, this target representing the plates and boiler of a torpedo boat. At the same distance, at 30° angle against the line of fire, it will penetrate a 1/2", 1/4", or 3/16" steel plate. The holes in some instances are from 6 to 11 inches in length, and 2-1/2 inches in height. Angle of depression 20°, of elevation 30°, and of direction 360°. Weight of the gun 3-3/4 cwt., and weight of carriage 2-1/2 cwt. _Hotchkiss Torpedo Gun._--This gun consists of a group of five barrels, revolving on a central shaft, a breech block, containing the firing mechanism, a feeding hopper, and the necessary hand crank for training and firing. The gun is mounted on trunnions attached to a vertical column, which rests in a suitable socket bolted to the ship's side; by this means a universal motion is obtained. The essential difference between this and the Nordenfelt gun is, that the _barrels_ and mechanism are put into rotatory motion. Another point of difference is that single shots only can be fired, and not a volley, as in the Nordenfelt gun. With the Hotchkiss gun, only some thirty shots can be fired in one minute at an advancing torpedo boat. The weight of the Hotchkiss steel shot is about 1 lb., but owing to the low velocity of the gun, its penetrative power is little more than that of the Nordenfelt 1/2 lb. bullet. The object to be gained in firing at an attacking torpedo boat is to sink her, and not merely to kill or disable her crew, for supposing the attack to be made with a contact spar torpedo, and the boat to have reached within 300 yards' distance from the ship, then, even if all the crew (probably two or three men) were disabled or killed, the boat would, if not sunk, still carry out its work of destruction; therefore the projectiles to be used under such circumstances should be only those capable of penetrating a torpedo boat's plates, _i. e._, solid steel shot, not shells.