two reasons apply to merchant ships
as well as naval ships. A third reason applies to naval vessels
only, and is that a few large ships can be handled much better
together than a large number of small ships, and embody that
"concentration of force" which it is the endeavor of strategy and
tactics to secure. A fourth reason is the obvious one that large
ships can carry larger guns than small ships.

The distinctly military (naval) purpose for which a war-ship is
designed necessitates, first, that in addition to her ability to
go rapidly and surely from place to place, she be able to exert
physical force against an enemy ship or fort, and, second, that
she have protection against the fire of guns and torpedoes from
enemy ships and forts, against bombs dropped from aircraft, and
against mines.

This means that a man-of-war, intended to exert the maximum of
physical force against an enemy and to be able to withstand the
maximum of punishment, must have guns and torpedoes for offense,
and must have armor and cellular division of the hull for defense;
the armor to keep out the enemy's shells, and the cellular division
of the hull to prevent the admission of more water than can fill
one water-tight compartment in case the ship is hit.

It must be admitted here that, at the present moment, torpedoes
hold such large charges of explosive that the cellular division of
ships does not adequately protect them. This means that a contest
has been going on between torpedo-makers and naval constructors like
the contest between armor-makers and gunmakers, and that just now the
torpedo-makers are in the lead. For this reason a battleship needs
other protection than that imparted by its cellular subdivision.
This is given by its "torpedo defense battery" of minor guns of
about 5-inch calibre.

By reason of the great vulnerability of all ships to attack below
the water-line, the torpedo was invented and developed. In its
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