The only defensive advantage possessed by a steel unarmored cruiser over a wooden one is derived from this system of construction. [Illustration: U. S. FRIGATE “CHICAGO” (STEEL).] The _Chicago_ is a steam-frigate, built throughout of steel of domestic manufacture, the outside plating being 9/16 inch thick. Her length is 325 feet, beam 48.2 feet, draught of water 19 feet. She has a displacement of 4500 tons, and will attain a minimum speed of 14 knots per hour with an indicated horse-power of 5000. The capacity of her coal-bunkers is 940 tons, and she carries a battery of four 8-inch steel breech-loading guns in half-turrets, and eight 6-inch and two 5-inch steel breech-loaders on the gun-deck. This ship has nine athwartships bulkheads, dividing the hull into ten main water-tight compartments, and the machinery and boilers are covered by a protective deck one and a half inches in thickness. When the bunkers are full of coal she has a coal protection nine feet thick from the water-line to eight feet above it. [Illustration: DECK PLANS OF THE U. S. FRIGATE “CHICAGO,” SHOWING BATTERY.] The deck plans show the arrangement of the main battery, in addition to which she carries a powerful secondary battery of Hotchkiss rapid-firing single-shot, and revolving cannons and Gatling guns. The bow of the vessel is strengthened for using the ram with which she is fitted. The rudder and steering-gear are under water. She has two screws—a subdivision of power which is given to all ships-of-war of over 3000 tons displacement—from which a great advantage is derived if one engine is broken down, as three-fourths of the speed can be maintained with the other. The advantage of this in a naval action is obvious. [Illustration: U. S. SLOOP-OF-WAR “ATLANTA” (STEEL).] The _Atlanta_, of which the _Boston_ is a counterpart, presents another type of a steel unarmored cruiser. She is a steam-corvette, or sloop-of-war, a single-decked ship. Her length is 276 feet, beam 42 feet, draught of water 16 feet 10 inches. She has a displacement of 3000 tons, and has attained a speed of 15.5 knots per hour with a maximum horse-power of 3482. The capacity of her coal-bunkers is 580 tons, and her battery consists of two 8-inch steel breech-loading guns and six 6-inch, besides a secondary battery of Hotchkiss and Gatling guns. [Illustration: DECK PLAN OF THE U. S. SLOOP-OF-WAR “ATLANTA,” SHOWING BATTERY.]