The shrapnel for the boat-guns is of the simplest description, having a thin shell and a central powder-chamber throughout its length. Shrapnel for the heavy calibres is similar to the English type. Case-shot is of the ordinary construction. [Illustration: 12-pdr. Smooth-Bore Shrapnel.] [Illustration: 3-inch B. L. Shrapnel.] [Illustration: Fixed Charge for Boat-Gun. (Shell and Cartridge.)] FUSES. [Illustration: Navy Time-Fuse.] The fuses used in the navy are both time and percussion. There are three types of time fuses. The navy time-fuse, used in rifled and smooth-bore projectiles, consists of a brass fuse-case pierced by a centre hole, the bottom of which is closed by a small leaden plug simply jammed into place, called a safety-plug. On the top of this is the column of fuse composition driven in a paper case. Over this screws a small metal plug, called a water-cap, having angular passages cut through it to prevent the passage of water to the flame. These holes are filled with igniting composition. Over the water-cap is secured a leaden patch, sealing the fuse. This patch is torn off when the projectile is put in the gun; the flame of discharge ignites the composition, and the projectile starting from its seat drives the safety-plug out of its place into the shell, leaving the passage clear for the flame. The Bormann fuse is used with the smooth-bore shrapnel. In this, the composition is driven in a horizontal cavity opening into a centre magazine. The top of the fuse is sealed, and its periphery marked to fractions of seconds. When inserting the projectile this fuse is cut, laying the composition bare at the desired time. [Illustration: Bormann Fuse.] [Illustration: Boxer Time-Fuse.] [Illustration: Schenkl Percussion Fuse.] The Boxer fuse is a wooden-cased fuse similar to its English original. There is but one type of percussion fuse used in the service. It consists of a brass case containing a small iron hollow cylinder filled with composition, and having at its head a small anvil on which an ordinary percussion-cap is fitted. This cylinder is suspended midway of the case by a small brass screw through the wall of the case. The top of the fuse is closed by a small screw-cap, one side of which is hollowed in a small cavity. Ordinarily this cap is screwed in place with the cavity turned downward, so that in case the cylinder breaks from its fastening the cap cannot be struck as it enters the cavity, while the shoulders bring it up before striking. To prepare it for firing, the cap is unscrewed and reversed, putting its flat side down. When the time-fuse is used in rifled shells, the safety-plug is removed before inserting the fuse. PRIMERS.