defence, and all
fortifications on the seaboard should be provided with furnaces and
grates, arranged so as to heat them with facility and rapidity.

[Footnote 35: In Mexico, where iron is scarce, copper is used for shot
and shells; but it is a poor substitute.]

There are several kinds of _hollow-shot_ and _shells_, called _bombs,
howitzes, grenades_, &c. They are made of cast iron, and usually in a
spherical shape, the cavity being concentric with the exterior surface.
The cavity was formerly made eccentric with the exterior, under the
belief that the heavier side would always strike first. The rotary
motion of the shell during its flight rendered this precaution of no
use. Fire is communicated to the combustible matter within the shell by
means of a fuse, which is so regulated that the explosion shall take
place at the desired moment. Hollow-shot are used with advantage to
destroy ordinary buildings, ships, earthwork, and thin walls of masonry;
they, however, are of little avail in breaking the massive walls of
well-constructed forts. Howitzes and grenades are particularly effective
against cavalry and columns of infantry, and are much employed on the
battle-field; they are also much used in the attack and defence of
places.

We find that as early as 1486 the Spaniards made use of a projectile
similar to the modern bomb. "They threw from their engines large
globular masses, composed of certain inflammable ingredients mixed with
gunpowder, which, scattering long trains of light," says an eye-witness,
"in their passage through the air, filled the beholders with dismay, and
descending on the roofs of edifices, frequently occasioned extensive
conflagration." In the siege of Constantinople by Mahomet II., shells
were used, and also mortars of enormous size. In 1572 Valturus proposed
to throw, with a kind of mortar, "globes of copper filled with powder."
In 1588, an artificer of Venloo burned Wachtendeck by throwing bombs
into the place. A similar attempt had just been made at Berg-op-Zoom.
The use of this projectile became quite common in France under Louis
XIII. Howitzes were not much used till the seventeenth century. They are
of German origin, and the howitzer first bore the name of _hausmitz_.

The _strap-shot_ consists of a round ball attached to a _sabot_ of the
same calibre, by means of two strips of tin passing over the shot at
right angles, and fastened to a third, which is soldered around the
sabot. One end