18 inches out of water, of light
draught, and about 200 by 45 feet. Their side-armor, laminated, is 5
inches thick, upon 3 feet of oak. They have one turret, like those of
the Roanoke, and carry one 15-inch gun and one 11-inch smooth-bore, or
a 200-pounder rifle. The original Monitor is 174 by 44-1/2 feet, with
5-inch side-armor, and a turret 8 inches thick, 20 feet in diameter
inside, and armed with two 11-inch guns. These vessels of Ericsson's
design are each in fact two vessels: a lower iron hull containing
boilers and machinery, and an upper scow overhanging the ends and
sides, forming the platform for the turret, and carrying the armor. The
Onondaga, now constructing, is an iron vessel of 222 feet length, 48
feet beam, and 13 feet depth, with 4-1/2-inch solid armor having no
backing, and without the overhanging top-works of the Monitors. She has
two turrets, like those of the Roanoke, and four 15-inch guns. Nearly
all the vessels of Class IV. are without spars, and have a pilothouse
about 6 feet in diameter and 6 feet high on the top of one of the
turrets.

The English Royal Sovereign, 3,765 tons and 330 feet length, and the
Prince Albert, 2,529 tons and the same length, are razeed wooden
vessels. The former carries 5, and the latter 6 of Captain Coles's
turrets with inclined sides, each turret designed for two 110-pounder
breech-loading Armstrong guns. The class of iron vessels constructing to
carry two of Coles's turrets are 175 feet long, having 42 feet beam,
24 feet depth, 17 feet draught, and 990 tons displacement. All these
English vessels are much higher out of water than Ericsson's.

Besides these classes, there is the variety of iron-clad vessels called
turtles, from their shape,--among them, the Keokuk (Whitney Battery)
159-1/2 feet long, with two stationary 11-inch gun turrets,--and a class
of Western river vessels of very light draught and some peculiarities of
construction. The latter resemble the Stevens Battery in the shape and
position of their armor, but carry their guns within their casemates.

The Stevens Battery, the Onondaga, and the Keokuk have independent
screw-propellers, which will enable them to turn on their own centres
and to manoeuvre much more rapidly and effectively in action than
vessels which, having but one propeller, cannot change their direction
without changing their position, and are obliged to make a long circuit
to change it at all. This subject is beginning to receive in