nder shall also transmit to the Bureau a quarterly return,
according to the prescribed form (_See_ Appendix B, No. X.) of all
firing whether with or without projectiles, in action or otherwise;
noting particularly the kind of shell, species of fuze, kind, charge,
and name of maker of the powder used in the gun and shell. He shall
take care to note also the number of premature explosions of shells,
and the point at which they take place, with the supposed causes
thereof.

60. The Inspector will also furnish the commander with a set of leaden
impressions of the interior orifice of the vents of the guns, secured
in a suitable box, that he may be able to compare the wear and gradual
enlargement. These will be transferred with the guns to other ships or
when landed.

61. The protracted firing to which the Navy cannon have been
subjected, and to which they will continue to be liable, renders it
necessary not to exceed the number of fires designated for each vent.

These must never exceed five hundred (500) fires for each vent.

In the IX-in., XI-in., and guns of similar form, the right vent is
always bored through, and the left initiated sufficiently to give it
direction.

When five hundred (500) rounds have been fired from the right vent,
it is to be closed by filling it with molten zinc or lead, and the
left vent is to be bored, which will require a skilful mechanic.

When the left vent has been fired five hundred (500) rounds, the gun
is to be disused, as it will then have been fired one thousand (1,000)
times.

It may happen, from some peculiarity in the nature of the iron, that
the vent may be worn to its full extent before five hundred (500)
rounds have been fired, in which case the vent is then to be closed,
and the other vent opened.

The gun should be frequently and critically examined inside and out
for cracks or defects, especially about the interior orifice of the
vent, of which impressions should be taken after every ten shotted
rounds in practice, and at the close of an action.

The instrument described on p. 16 is convenient, but by no means
indispensable--any small spar, such as a boat's mast, or even the
rammer handle with a curved piece of wood seized to the end, will, in
expert hands, take an impression of the vent or crack equally well.

62. As the best indication of the amount of firing to which any
smooth-bored gun has been exposed, when it is not otherwise known, is
given by the enlargement