Both percussion and friction primers are used. The percussion primer consists of a quill tube, the upper end of which is split and spread out to form a wafer. The body is filled with fine powder, the lower end being sealed with shellac, and the wafer is filled with detonating composition, covered and sealed with shellac. The friction primer is a quill tube filled with fine powder, and having in its head a wire igniter in contact with detonating composition. The end of the wire is twisted into a loop for the purpose of hooking a firing laniard. A small preventer-loop is attached to the primer, hooking over a small pin just forward of the vent. [Illustration: Percussion Primer.] [Illustration: Friction Primer.] LOCKS. Percussion-locks are used with all smooth-bores. They are of the ordinary type of heavy brass gun-locks, the pivot-hole being slotted so that in firing, after the lock strikes the primer it is drawn clear of the vent. SIGHTS. The smooth-bore broadside-guns are provided with centre-breech and reinforce sights, pivot-guns with centre and tangent sights, and the rifled guns with tangent-sights. The smooth-bore breech-sights are rectangular bars shipped with an angle to the rear so that two sides may be seen. These sights are marked on one side for ordinary and on the other for heavy charges, corresponding to shot and shell. The reinforce sights are of the ordinary pattern. The Parrott tangent-sight does not slide in a sight-box, but has a stem which seats in a casing. It is cylindrical, and the sight-notch, fixed to a ring, slides up and down the sight-bar. The sight-notch itself is a small capstan-head having four radial notches, and working on a screw perpendicularly to the sight-bar to allow for drift. The tangent-sight for the 8-inch M. L. R. is set at a permanent angle of deflection of 1° 50´, and is provided with a sliding leaf. The graduation on all sights except the Parrott rifles and the boat-guns is in hundreds of yards. In the remainder it is in fractions of degrees. MACHINE-GUNS. [Illustration: Hotchkiss Revolving Cannon.]