attached to the carriage: but the ordinary beds and
quoins are also still in use; they are arranged to allow the extreme
elevation and depression of the guns which the ports will admit with
safety. When the inner or thick end of the quoin is fair with the end
of the bed in place, the gun is level in the carriage; or horizontal,
when the ship is upright. The degrees of elevation above this level,
which may be given to the gun by drawing out the quoin when laid on
its base, are marked on the side or edge, and those of depression on
the flat part of the quoin, so that when the quoin is turned on its
side for depressing, the marks may be seen. The level mark on the
quoin is to correspond with the end of the bed. When the quoin is
entirely removed, and the breech of the gun rests on the bed, the gun
has its greatest safe elevation; and when the quoin is pushed home on
its side, the gun has the greatest safe depression that the port will
admit.

Care must be taken that the stop on the quoin is always properly
lodged, to prevent the quoin from flying out or changing its position,
and that the bed is secured to the bed-bolt.

Porter's bed and quoin has been adopted for all carriages requiring
quoins. This quoin, being graduated to whole degrees, requires a small
additional quoin for slight differences of elevation in smooth water.

When the elevating screw is used, a quoin should be at hand to place
under the breech of the gun, when at extreme elevation, to relieve the
screw from the shock of the discharge, and prevent a change of the
elevation, as well as to take the place of the screw if it should be
disabled. When the fire is continuous at the same distance, the lever
of the elevating screw should be secured by a lanyard, to prevent the
screw from turning and altering the elevation.

308. If a greater elevation for broadside-guns should be desired for
any special purpose, it may be obtained by placing inclined planes
behind the rear trucks, for them to recoil over and produce a
corresponding depression of the muzzle of the gun as it comes within
the port. But it will be observed that, beyond the elevation which the
ports will admit of, the sights can no longer be taken by the tangent
or any other top sight, as the upper sill of the port interferes. The
gun must therefore be laid by the quoin and pendulum.

Additional depression may also be obtained by placing inclined planes
for the front trucks to recoil upon, or by r