The old “flint” lock has now quite gone out of use, having been
superseded by the “percussion.” This is a contrivance to cause that
part of the lock called the cock or hammer to strike the percussion
cap with great force, and so discharge it (figs. 3 and 4). The cap is
put on to a small projection called the “nipple,” which has a hole at
the top communicating with the barrel, and down which the spark from
the percussion cap passes.
In rifled guns, of late, the use of conical balls has been
introduced, for the effect of the charge in propelling a ball rapidly
out of a barrel with spiral grooves is to turn it as it passes out
of the barrel, and consequently to “spin” it with great velocity in
one direction, like a top; the effect of this is to balance every
part of the ball in the air and so cause it to take a true direction,
for if the merest notch or hollow existed in a spherical ball, that
part being lightest and having the least momentum would not maintain
its rate so long, and by lagging behind cause the ball to describe a
part of a circle in its course. It is thus that the balls from common
muskets, although rightly directed, often fall extremely wide of the
mark. Military muskets and rifles are fitted with bayonets, that they
may act both as lances and fire-arms (fig. 5).
Illustration: GUN-MOULD.
Illustration: GUN-BORING MACHINE.
“Ordnance,” or great guns are made of cast-iron or of gun-metal
(a mixture of copper and tin), but experiments have lately been
made with wrought-iron and cast-steel, with the view of obtaining
a tougher and more durable material. They are cast solid, and
afterwards bored with a machine. The following account of gun-casting
at Woolwich Arsenal appeared in the “Times” of January 22, 1858:--“As
the plug was drawn the glowing mass leapt out like a stream of
silver, filling up the moulds for two twelve-pounder howitzers
that were to be cast, and leaving a bright, hungry-looking flame
playing over them, making everything red-hot which it approached.
In this workshop about twenty men and boys produce twelve brass guns
per week, as well as tangent-scales for ships’ guns, lock-covers,
brass fittings for machinery, &c., and iron castings. Each gun
cast requires two days to cool, when it is removed to the turnery
to be bored; and it was to this workshop that the royal party
next proceeded, and saw the guns in all their stages of trimming,
finishing, and boring. Three-quarters of an hour suffice to cut a
gun to its proper length and remove the rough sand which adheres
to it after casting. It is then turned over to another man and
another machine, and the whole of its outside shaping and marking
is completely finished in two days, when it is again turned over
to a fresh machine, and bored and drilled ready for service in a
day-and-a-half more. With the present machinery the turnery at
Woolwich could finish thirty brass guns in a week, though at this
time it never completes more than ten or twelve.”
Illustration: FIG. 6. (‡ FIELD GUN).
The ordinary form of “gun” is shown by fig. 6. The knob at the
right-hand side of the cut is called the “button,” the next division
the “vent field,” beyond this to the rim the “first reinforce,”
further on, the “second reinforce,” from which a cylindrical bar
projects on each side for attaching the gun to the carriage, called
“trunnions.” Beyond this to the next rim is called the “chace,” and
beyond this again to the end the “muzzle.” Guns are chiefly used to
throw solid round shot of cast-iron, accurately turned to a sphere,
and the weight of these determines the character of the gun, as a
thirty-two pounder, &c., the words “heavy” and “light” designating
the thickness and consequent weight of the metal composing it. There
is a smaller and shorter kind of gun, called a “carronade,” which
is held to the carriage by a projection underneath, having a hole
for a bolt to secure it, instead of trunnions. Another kind of gun,
called a “howitzer,” is of shorter proportions than the ordinary gun
and larger in the bore; it is chiefly intended to throw shells at a
slight elevation. The mortar is still shorter, and of much thicker
metal; it is held to a sort of platform by trunnions at its extreme
end, and is intended to throw shells to great distances, and at a
great elevation.
Illustration: FIG. 7. SHELL CASTING.
Illustration: BULLET-CASTING, WOOLWICH ARSENAL.