e and out, for defects
of metal or of manufacture, and note the results.

The interior of the bore is to be examined by reflecting the rays of
the sun into it from a mirror or mirrors; or, if the sun is obscured,
and there can be no delay, by means of a spirit-lamp, or of a wax
taper, on the end of a rod, taking care not to smoke the surface of
the bore.

The cylinder-gauge is then to be introduced, which must pass freely to
the bottom of the cylindrical part of the bore. If obstructed, the
depth to which it reaches should be noted.

The star-gauge is used to ascertain the exact diameter of the bore,
and of the cylindrical part of the chamber. The bore must be measured
at intervals of 1/4 inch from the bottom of the cylindrical part to
the seat of the shot; of 1 inch from that point to the trunnions; and
of 5 inches from the trunnions to the muzzle. If any marks of the
reamer or other defects are seen in the bore, they are to be searched
for, and their depths and positions noted. These results are to be
tabulated according to the blank forms furnished. The whole length of
the bore is ascertained by means of the measuring-staff, with the
point screwed on, supported in the axis of the bore by the disks and
half-tompion.

In the absence of this instrument, a pine rod, having the proper
length of the bore marked on it, and the end rounded to the curve of
the bottom of the bore, will answer as well, using a thread or a
straight-edge across the face of the muzzle.

The shape and dimensions of the chamber, and the position of the
interior orifice of the vent, are verified by means of the
chamber-gauge, the description of which will explain its use. An
inspection of the chamber-reamer will be generally satisfactory in
determining the size and shape of the chamber.

The vent is measured by the appropriate gauges, the smaller of which
must enter freely, and the larger not at all. It is searched for
roughness, or for cavities in the metal around it, by means of the
searcher, the point of which should feel every part of it carefully.

Its inclination to the surface, and its position externally, are
verified by means of the vent-guide furnished for the Dahlgren guns,
and by the semicircular protractor and the vent-gauge.

In guns of the ordinary construction, the position of the vent is
marked on the profile-board, and its inclination to the surface is
determined by the protractor and vent-gauge.

The exterior lengths of