eel, three inches thick, which is placed
several feet below the water-line. Everything above this deck and outside
this fortress might be shot away, and the vessel would still float and
fight.

On the roof of the fortress are placed the turrets containing the big
guns. The largest of these guns, 13-inch calibre, weigh about sixty tons
each, and will carry a shell weighing eleven hundred pounds about twelve
miles. The turrets are circular, as a rule, large enough to hold two guns,
and are made of face-hardened steel from fifteen to eighteen inches thick.
They revolve within a barbette or ring of steel eighteen inches thick,
which protects the machinery by which the guns are trained. Farther back
on the roof of the fortress are other and lighter turrets made of 8-inch
steel and carrying 8-inch guns, and at other places are stationed
rapid-fire guns of lighter calibre, protected by thinner armour than that
of the main belt.

If all this secondary battery is stripped off, leaving nothing but the
turrets with the big guns, and these are brought down close to the water,
and the armour belt is reduced to seven or eight inches in thickness, the
type of vessel known as the monitor is reached. It is simply a battle-ship
on a reduced scale. Such vessels are very slow and cannot stand rough
weather, on account of their low freeboard. The speed of the monitors is
seldom more than twelve or fourteen miles an hour, and they are intended
to act in coast defence, usually in connection with shore-batteries. The
best types in the navy are the _Terror_ and the _Puritan_.

The speed of a battle-ship is about eighteen miles an hour. The best
specimen in the navy is the _Indiana_, declared by its admirers to be the
most powerful battle-ship afloat. Second-class battle-ships, like the
_Texas_, are smaller vessels, usually about seven thousand tons, and they
have a much lighter armour belt, about twelve inches, and do not carry so
heavy an armament as ships of the first class. The _Maine_ was a
second-class battle-ship. Her largest guns were of 10-inch calibre; her
armour was twelve inches thick, and her turrets were eight inches thick
only.

The first step in reducing the armament from that of the battle-ship
proper, at the same time increasing the speed, produces the armoured
cruiser. This type of vessel may carry no guns of more than 8-inch
calibre, and the armour belt is reduced to three or four inches in
thickness. Instead of the roof