rotective deck extends from the
citadel in each direction, preventing the projectiles from entering
the compartments below. The hull is divided into numerous compartments
by water-tight bulkheads, and, having a reserve of flotation, the
stability of the ship is not lost, even though the parts above the
protective deck, forward and aft, be destroyed or filled with water.
The guns are protected by turrets or barbettes. The deflective system
consists in inclining the armor, or in so placing it that it will be
difficult or impossible to make a projectile strike normal to the face
of the plate. A plate that is inclined to the path of a projectile
will, of course, offer greater resistance to penetration than one
which is perpendicular; hence, when there is no other condition to
outweigh this one, the armor is placed in such a manner as to be at
the smallest possible angle with the probable path of the projectile.
This system is designed to cause the projectile to glance or deflect
on impact. Deflective armor should be at such an angle that the
projectiles fired at it cannot bite, and hence the angle will vary
according to the projectile most likely to be used. In the usual form
of deflective deck the armor is at such a small inclination with the
horizon that it becomes very effective. Turret and barbette armor may
be considered as deflective armor. The term inclined armor denotes
deflective armor that is inclined to the vertical. The kinds of armor
that are in use may be designated as rolled iron, chilled cast iron,
compound, forged and tempered steel, and nickel steel. Iron armor
consists of wrought iron plates, rolled or forged, and of cast iron or
chilled cast iron, as in the Gruson armor. Compound armor consists of
a forged combination of a steel plate and an iron plate. Steel armor
consists of wrought steel plates. Nickel-steel armor consists of
plates made from an alloy of nickel and steel.

I have spoken above of laminated armor. To secure the full benefit of
this kind, the plates must be neatly fitted to each other; the
surfaces must make close contact. This requires accurate machining,
and hence is expensive. To overcome this point sandwiched armor was
suggested. This consists in placing a layer of wood between the
laminations, as shown in Fig. 2. It was found that laminated and
sandwiched armor gave very much less resisting power than solid rolled
plates of the same thickness. Wrought iron armor is made under the
h