gh to fight one of
her own size must be fast enough to run away. Any vessel which is inferior
in armament, and has no compensating superiority in speed, is outclassed.
The same is true of any vessel which is equal in armament, but inferior in
speed to an adversary.

The size of a vessel is measured by its displacement. This displacement is
the number of tons of water she will push aside to make room for herself.
A vessel of ten thousand tons will take engines of a certain weight and
power to drive her at a given speed, and the larger the engine the larger
the boilers and the greater the supply of coal required. Now, if it is
necessary to give this vessel heavy protective armour and big guns, the
additional weight of this equipment must be saved somewhere else, and
usually in the engine-room, reducing the speed of the vessel. Following
out this principle, it will be found that the fastest ships carry the
lightest armament, and that those which carry the biggest guns in their
batteries and the thickest armour on their sides are comparatively slow,
the extreme variation among vessels of the same displacement being about
eight or nine miles an hour.

In the matter of attack and defence, vessels are distinguished by the
number and weight of the guns they carry, and by the distribution and
thickness of their armour. Protective armour is of two kinds, that which
surrounds the guns, so as to protect them from the enemy's fire, and that
which protects the motive-power of the ship, so as to prevent the engines
from being rendered useless.

The maximum of guns and armour and the minimum of speed are to be found in
the first-class battle-ship, which is simply a floating fortress, so
constructed that she need never run away, but can stand up and fight as
long as her gun turrets revolve. The general plan of construction in a
battle-ship is to surround the engines, boilers, and magazines with a wall
of Harveyized steel armour eighteen inches or so thick, and seven or eight
feet high, which extends about four feet below the water-line and three
feet above it. This armour belt is not only on the sides of the ship, but
is carried across it fore and aft, immediately in front of and behind the
space occupied by the engines and magazines, and the whole affair is
covered with a solid steel roof three or four inches thick. Outside this
central fortress, and extending from it clear to the bow and stern at each
end, is a protective deck of st