original form, the torpedo was motionless in the water, either
anchored to the ground, or floating on the surface, and was in
fact what now is called a "mine." But forty-eight years ago an
Englishman named Whitehead invented the automobile, auto-steering,
torpedo, which still bears his name. This torpedo is used in all
the navies, and is launched on its mission from battleships, battle
cruisers, destroyers, submarines, and other craft of various kinds.

Most torpedoes are to be found in destroyers--long, fast, frail
vessels, averaging about 700 tons displacement, that are intended to
dash at enemy ships at night, or under other favorable conditions,
launch their torpedoes, and hurry away. The torpedo is "a weapon
of opportunity." It has had a long, slow fight for its existence;
but its success during the present war has established it firmly
in naval warfare.

The submarine has followed the destroyer, and some people think
will supplant it; though its relatively slow speed prevents those
dashes that are the destroyer's rôle. The submarine is, however,
a kind of destroyer that is submersible, in which the necessities
of submersibility preclude great speed. The submarine was designed
to accomplish a clear and definite purpose--a secret under-water
attack on an enemy's ship in the vicinity. It has succeeded so well
in its limited mission that some intelligent people declare that
we need submarines only--ignoring the fact that, even if submarines
could successfully prevent actual invasion, they could not carry
on operations at a distance from their base of supplies. It is
true that submarines may be made so large that they can steam at
great speed from place to place, as capital ships steam now, carry
large supplies of fuel and food, house their crews hygienically,