caliber, can
hardly be overestimated.

The relative value of steel and compound armor is much debated, and at
present the rivalry is great, but the weight of evidence and opinion
seems to favor the all-steel plate. The hard face of a compound plate
is supposed to break up the projectile, that is, make the projectile
expend its energy on itself rather than upon the plate, and the
backing of wrought iron is, by its greater ductility, to prevent the
destruction of the plate. It seems probable that these two systems
will approach each other as the development goes on. An alloy of
nickel and steel is now attracting attention and bids fair to give
very good results.

The problem to be solved, as far as naval armor is concerned, is to
get the greatest amount of protection with the least possible weight
and volume, and this reduction of weight and volume must be
accomplished, in the main, by reducing the thickness of the plates by
increasing the resisting power of the material. In the compound plate
great surface hardness is readily and safely attained, but it has not
yet been definitely determined what the proper proportionate thickness
of iron and steel is.

A considerable thickness of steel is necessary to aid, by its
stiffness, in preventing the very ductile iron from giving back to
such an extent as to distort the steel face and thus tear or separate
the parts of the plate. The ductile iron gives a very low resisting
power, its duty being to hold the steel face up to its work. If now we
substitute a soft steel plate in the place of the ductile iron, we
will get greater resisting power, but our compound plate then becomes
virtually an all-steel one, only differing in process of manufacture.
The greatest faults of the compound plate are the imperfect welding of
the parts and the lack of solidity of the iron. When fired at, the
surface has a tendency to chip.

In the all-steel plate we have the greatest resisting power
throughout, but there are manufacturing difficulties, and surface
hardness equal to that of the compound plate has not been obtained.
The manufacturing difficulties are being gradually overcome, and
artillerists are in high hopes that the requisite surface hardness
will soon be obtained.

The following may be stated as well proved:

1. That steel armor promises to replace both iron and compound.

2. That projectiles designed for the piercing of hard armor must be
made of steel.

3. That the larger t