was fired. Such a torpedo is now effective up to
two miles, and it will traverse this distance in about six minutes.

Torpedoes are discharged from what are called "torpedo tubes" by means
of compressed air. These tubes are to all intents and purposes, guns
made of thin steel, the torpedo being put in at the breech. Those used
on board torpedo boats or similar light fast craft are mounted on a
swivel on the deck; in larger vessels they are usually placed below the
waterline so as to be free from the serious consequences that would
ensue if the tube were struck by the enemy's shot, while a torpedo was
in it. Torpedoes have also been invented which are steered by
electricity.

The problem of protecting ships against torpedoes is a difficult one,
and no satisfactory solution has yet been arrived at. All large
warships, however, are provided with "torpedo nets" of thick iron wire,
which are hung round her at the end of long poles, which, when not in
use, are tied up alongside. But mechanism has been invented by which
the torpedo will cut through the netting, if it encounters it, so that
at present the torpedo is master of the situation, within its range. In
fairly shallow water a torpedo will throw a column of water nearly 200
feet into the air, by the impulse of the gases generated by the
explosion, and no ship yet built would be able to withstand its enormous
shock.

Reference has already been made to the huge guns of the _Inflexible_,
and to the improvements in both powder and guns made later on. The
modern gun is what is called a "wire gun," from its method of
construction. Round a central tube of steel, several layers of
immensely strong steel wire is tightly wound; a second steel tube is
then slipped on above the wire, and as this tube is hot when first put
on, when it cools it contracts and binds the layers of wire tightly
together, forming a gun of very great strength--as, indeed, it would
need to be, seeing that it has to withstand a pressure of over 16 tons
to the square inch.

The projectiles fired from naval guns are of three kinds, solid shot for
piercing the thickest armour,--as on the conning-tower, or barbettes;
"armour piercing shell," with very thick walls and small bursting
charge, which can only penetrate armour, two-thirds of that piercible by
solid shot; lastly, "common shell," in which the shell walls are much
thinner, and can thus only be used with effect against the lighter
structures