o supply the deficiency or remove the excess.

CANNON-PRIMERS.

172. These are of two kinds, percussion and friction. Each
percussion-primer is composed of a quill tube capped by an explosive
wafer. The quills used for this purpose are first inspected by passing
them through a gauge rather smaller than the vent.

The tube is filled with fine-grained powder.

The wafer is composed of a cap of cartridge-paper, enclosing a layer
of fulminate of mercury combined with a small quantity of mealed
powder. When pressed and perfectly dry, the wafer is coated with
uncolored shellac, to preserve it from dampness.

173. Primers are to be kept in tin boxes containing fifty each, the
lids of which are luted with shellac to exclude moisture until wanted
for immediate use. These boxes are intended to fit in and form a
lining to the primer-boxes which slip on the waist-belts worn by
Captains of guns. For purposes of exercise no more of these boxes
should be opened than are required; but for action a full box should
be delivered to each Captain and 2d Captain of a gun.

174. A friction-primer consists of a tube charged with gunpowder, to
the top of which is fastened a spur containing friction-powder, which
is exploded by means of a slider pulled out by a lanyard. It is
intended for use in case the lock should be out of order, or the other
primers fail from any unforeseen cause. Friction-primers are packed in
tin boxes in the same manner as percussion-primers. They are obtained
from the Army as required.

175. Filled boxes of primers are kept in close laboratory cases, for
which stowage must be provided in the general store-room of the ship,
or other safe place.[1] They are on no account to be placed in the
magazine, and the boxes must be so labelled before being put on board
ship.

176. When primers have been returned from cruising ships, or have
remained in store for one or more years, they must be tested by firing
five per cent. of the number, and not issued again without special
orders.

177. Damaged fuzes, primers, caps, and tubes, are always to be
returned to the Ordnance Yard at Washington, in the condition in which
they were received on the return of the ship.

178. The boxes containing metallic cartridges for breech-loading arms
require the same care as percussion-caps, and are to be labelled, "On
no account to be placed in the magazine."

179. PERCUSSION-CAPS for muskets, carbines, and pistols are made in
the labor