ith the introduction of iron armor. With this form of armor we
have had a small amount of war experience. The combat of the Monitor
and Merrimac, in Hampton Roads, in May, 1862, not only marked an epoch
in the development of models of fighting ships, but also marked one in
the use of armor. The Monitor's turret was composed of nine one-inch
plates of wrought iron, bolted together. Plates built in this manner
form what is known as laminated armor. (See Fig. 1.) The side armor of
the hull was composed of four one-inch plates. The Merrimac's casemate
was composed of four one-inch plates or two two-inch plates backed by
oak. The later monitors had laminated armor composed of one-inch
plates. The foregoing, with the Albemarle and Tennessee rams under the
Confederate flag, are about the sum of our practical experience in the
use of armor.

[Illustration: Fig. 1.]

European nations took up the subject of armor and energetically
conducted experiments which have cost large sums of money, but have
given much valuable data. For a long time wrought iron was the only
material used for armor, and the resisting power depending on the
thickness; and the caliber and penetration of guns rapidly increasing,
it was not long before a point was reached where the requisite
thickness made the load of armor so great that it was impracticable
for a ship to carry it. The question then arose as to what were the
most important parts of a ship to protect. The attempted solutions of
this question brought out various systems of distributions.

Armored ships were formerly of two classes; in one the guns were
mounted in broadside, in the other in turrets. Every part of the ship
was protected with iron to a greater or less thickness. In more modern
ships the guns are mounted in an armored citadel, in armored barbettes
or turrets, the engines, boilers and waterline being the only other
parts protected. There may be said to be three systems of armor
distribution. The belt system consists in protecting the whole
waterline by an armored belt, the armor being thickest abreast of the
engines and boilers. The guns are protected by breastworks, turrets or
barbettes, the other parts of the ship being unprotected. The French
use the belt system, and our own monitors may be classed under it. The
central citadel system consists in armoring that part of the waterline
which is abreast of the engines and boilers. Forward and aft the
waterline is unprotected, but a p