and dollars have been
squandered on some court-favorite, the whole matter ends in the
explosion of the "_improvement_," and probably the destruction of the
"_inventor_," and perhaps also of his spectators. Let us be distinctly
understood on this subject. There may be _inventions_ and _improvements_
in the manufacture of wrought iron, but there is nothing _new_ in its
_application_ to the construction of cannon, for it has been used for
this purpose as long ago as the first invention of the art.

2. _Field Artillery_ is composed of the smaller guns and howitzers. In
our service this class of cannon includes the six and twelve-pounder
guns, and the twelve and twenty-four-pounder howitzers. All these are
now made of bronze. This material is more expensive than cast-iron, but
its superior tenacity renders it more useful where great weight is
objectionable. Improvements in the manufacture of cast iron may render
it safe to employ this metal in the construction of field-pieces. It is
also possible the wrought iron may be forged in masses large enough, and
the cost be so reduced as to bring it into use for field-pieces. It is
here important to combine strength with lightness, and additional
expense may very properly be incurred to secure this important object.

The _projectiles_ now in use are solid shot, shells, strap-shot, case or
canister-shot, grape-shot, light and fire-balls, carcasses, grenades,
and rockets.

_Solid shot_ are now almost invariably made of cast iron,[35] formed in
moulds of sand or iron. This projectile is used under almost every
circumstance, whether in the battle-field or in the attack and defence
of places, and is the only one that is effectual against the stone walls
of forts. _Hot shot_ are used against shipping and wooden structures of
every description. Red-hot balls were first employed by the king of
Poland, in 1575, but, on account of the difficulty of heating them with
rapidity, and the danger of loading the piece with them, this kind of
projectile was not in general use till a much later period. It was at
first supposed that the expansion of the metal would be so great, when
heated to a red or white heat, as to prevent the ball from entering the
piece; it is found, however, that the windage is still sufficient for
loading with facility. These red-hot balls are principally used to fire
wooden buildings, ships, and other combustible matter. They are
therefore much used as a projectile for coast