he vent-bouching.
2. On the top of the bore, between the trunnions and
reinforce-band.
3. On the lower side of the bore, near the seat of the shot,
at the junction of the lands and grooves.
4. Near the inside of the muzzle, caused by explosion of
shells.

Although shells have been frequently ruptured in the guns without
leaving any visible traces of injury, yet they may be developed after
a certain number of rounds. Thus, in proving a gun at West Point, a
shell exploded in the gun at the second fire: on examination, no
traces of injury could be perceived; but, on a re-examination of the
gun after the tenth fire, a fine transverse crack was discovered in
the rear of the vent, extending two-thirds round the bore. It is
therefore important that frequent examinations shall be made, even if
no apparent injuries exist, as it is the opinion of the inventor of
the guns that the principal, if not the only cause of failure of these
guns in service, is due to the rupture of shells within the bore.

Experiments have been made, and are still in progress, which appear to
show that these premature explosions may be to a great extent
obviated, if not altogether prevented, by lining or coating the rough
surface of the interior of the shell with a smooth and elastic
coating.

All rifle-shells, except those for howitzers, before being issued for
service, shall therefore be lined or coated on the interior with a
mixture composed of--

16 ounces of soap--common yellow, not salt-water soap.
7 ounces of tallow.
7 ounces of rosin.

The tallow should be melted first, then melt and add the rosin, and,
lastly, the soap, bringing the mass to a heat that will make it _very_
fluid.

The shells having been first thoroughly cleaned, fill them about
one-third full of the composition, roll them slowly so as to spread
the mixture over the whole interior surface, and then pour off the
residue. This coating should be about five-hundredths (0.05) of an
inch in thickness, and is expected, from a series of experiments made
for the purpose, to prevent the premature explosion of shells in the
bores of rifled guns.

The Bureau further directs that hereafter the charge of the
100-pounder, or 6.4 inch, Parrott rifle, shall be reduced to eight (8)
pounds of rifle, or No. 7 powder, and that only the short shell or
solid shot, not exceeding eighty (80) pounds weight, and spherical
projectiles, prepared as directed in