protected, and carry 30 casemate-guns.  All the above vessels are to carry two or more Armstrong swivel-guns fore and aft.  Four vessels of La Gloire class, (French,) 255 feet long and built of wood, resembling the Royal Oak, carry 34 guns, and are completely clad in 4-1/2-inch solid armor.  Ten French vessels, of a little larger dimensions, are similarly constructed.  The Galena (American) is of this class as to extent of protection.  The quality of her armor has been referred to.

CLASS IV. Ships with Revolving Turrets.  The Roanoke, (American,) a razeed wooden frigate of 4,500 tons, is 265 feet long, 521/2 feet wide, and 32 feet deep, and will draw about 21 feet, and have a speed of 8 to 9 knots.  This and all the vessels to be referred to in this class are iron-clad from end to end, and from the upper deck to 4 or 5 feet below the water-line.  The Roanoke’s plates (solid) are 4-1/2 inches thick, except at the ends, where they are 3-1/2, and are backed with 30 inches of oak.  She has three turrets upon her main-deck, each 21 feet in diameter inside, 9 feet high, and composed of 11 thicknesses of 1-inch plates.  Her armament is six 15-inch guns, two in each turret.  Of the Monitors, which are all constructed of iron, two now building are to be seagoing and very fast, and are to act as rams, like several of the other vessels described.  One of these, the Puritan, is 340 feet long, 52 feet wide, and 22 feet deep, and will draw 20 feet.  The armor of her hull, 10-1/2 inches thick, composed mostly of 1-inch plates and 3 feet of oak backing, projects beyond her sides by the amount of its thickness, and overhangs, forming a solid ram 16 feet long at the bow.  The whole upper structure also overhangs the stern, and protects the screw and rudder.  This vessel will carry two turrets, 28 feet in diameter inside, 9 feet high, and 2 feet thick, composed of 1-inch plates.  Each turret contains two 15-inch guns.  The other vessel, the Dictator, is similarly constructed, except that it has one turret, two guns, and 320 feet length.  The upper (shot-proof) deck of these vessels is 2 feet out of water.  The 18 smaller Ericsson vessels, several of which are ready for service, are 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.