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
hammer or under the rolls, in the ordinary manner of making plates,
and has been exhaustively studied and experimented with--more so than
any other form of armor.

[Illustration: Fig. 2.]

Chilled cast iron armor is manufactured by Gruson, in Germany, and is
used in sea coast defense forts of Europe.

In 1867 several compound plates were made by Chas. Cammell & Co., of
Sheffield, England, and were tested at Shoeburyness, in England, and
at Tegel, in Russia. These plates were made by welding slabs of steel
to iron; but the difficulties were so great that the idea was
abandoned for the time.

[Illustration: Fig. 3.]

[Illustration: FIG. 4.]

Compound armor, as now manufactured, is of two types: Wilson's patent,
a backing of rolled iron, faced with Bessemer steel; Ellis' patent, a
backing of rolled iron, faced with a plate of hard rolled steel,
cemented with a layer of Bessemer steel. Both these kinds are
manufactured in England and France in sizes up to fifty tons weight.
The Wilson process is used at the works of Messrs. Cammell & Co., of