coming to a point at an angle of 80 degrees. The upper hull is 174 feet long, 41 feet 4 inches wide, with perpendicular sides 5 feet high. It juts over the lower hull on each side 3 feet 7 inches, and at each end 25 feet. The sides of this portion are built of white oak, 2½ feet thick, covered with 6 inches of iron plates on the outside, and a ½-inch plating of iron within; the object of the latter being to arrest splinters in case of a ball penetrating the sides. The top is covered with a bomb-proof flat deck unprotected by any railing or bulwark. This deck consists of oak beams, 10 inches square and 26 inches apart, covered with 8-inch plank, and this with 2 layers of iron, each an inch thick. The draught of water is 10 feet, leaving only 18 inches above the surface. The projecting ends of the upper hull serve as a cover for the propeller and rudder in the stern and the anchor in the bow. The former are entirely out of reach of shot; and the latter is carried in the upper hull, from which it is readily lowered, and into which it is hoisted again by men working below, without any exposure or sign of their movements on the outside. The lower hull is so situated beneath the upper, that it can only be reached by a ball after this has passed through at least 25 feet of water, and the inclination of the sides would then prevent its penetration; and the upper is impregnable in its 6 inches of iron, backed with 30 inches of white oak, and the inner lining of ½-inch iron.
The prominent object upon the deck in the middle of the boat is the turret or castle, a cylinder of 20 feet diameter within, and 9 feet high, built of 8 thicknesses of 1-inch plates, bolted securely one over another with overlapping joints, and lined with an additional layer of iron an inch thick, thus making 9 inches in all. The weight of the turret is about 100 tons, and its support is a circular bed plate of composition metal firmly secured to the deck. Upon this it is supported except in time of action, when the weight is taken by a vertical central shaft of iron, with which it is made to revolve as desired, the motive power being a steam-engine specially designed for this service, as also for working the blowers for the fires, and for ventilation. On the top, the turret is covered with iron beams and perforated iron, shell-proof. This, while