armament; their function in war is to capture the commerce-destroyers of the enemy, to act as commerce-destroyers themselves, and to convoy and protect fleets of large and fast merchant vessels. To accomplish these purposes great speed is necessary, either to overtake or convoy swift merchantmen; great endurance or coal supply, to enable them to keep the sea for long periods on the

path usually frequented by merchant vessels; and offensive and defensive power sufficient to enable them to successfully resist the attacks of vessels of their own class.

The type next in importance and general usefulness is styled the protected cruiser, or those whose only protection against injury consists of sloping armor decks of varying thickness, in combination with coffer dams filled with waterexcluding material and closely divided compartments in the region of the line of flotation. The characteristics of this type are not capable of being so clearly defined as those already considered, as they include such widely differing vessels. as the triple-screw Columbia of 7,350 tons displacement, the Olympia. of 5,500 tons, down to cruisers of 2,000 and 3,000 tons displacement as rep

resented by the Cincinnati and Detroit. Their function is a varied though exceedingly useful one; some are designed particularly for preying upon the commerce of an enemy so as to cripple its resources, the most notable examples being the Columbia of our own and the Blake of the British Navy.

Speed and endurance are the features emphasized, combined with guns of light caliber for dealing with unarmed vessels;

FIG. 8.-UNITED STATES STEAMER MIANTONOMOH. Monitor.

others again, like the Chicago, Newark, Baltimore, and San Francisco, are designed for purposes of general utility, such as protecting our mercantile interests abroad, the one feature emphasized being endurance, with those of speed, protection, and armament very fairly developed. Our gunboats of the Yorktown and Machias types are miniature cruisers, except that speed has been sacrificed to enable them to carry heavy batteries; at present they are constructed entirely of steel, although many fruitless efforts have been made to adopt in this class the style of construction known as composite-that is, all the parts of steel as is customary, except the outer covering of the hull, which is formed of wood planking coppered instead of steel plating. This system has been most earnestly and ably advocated by Chief Naval Constructor Philip Hichborn, and has formed the subject of special reports by him. to the Navy Department, but the wording of the congressional appropriations has been such as to preclude its adoption.

The advantages to be gained are cheapness and ease of maintenance, freedom from fouling and consequent ease of propulsion, with the ability to keep the sea for long periods without being docked. All vessels of war are in a certain sense compromises between speed, endurance, protection, and armament; no one feature can be largely developed without corresponding sacrifices in the development of the others: for example, if great speed is required, it entails machinery of great power and weight with a large supply of coal; the weights, therefore, of the other main features must necessarily be reduced in order to emphasize that of speed; therefore, when Congress has appropriated for a certain type of vessel and fixed the limit of cost, a very careful study of all existing vessels of the desired type is made by the designing staff of the construction department, the particular requirements of the service are considered, the features to be emphasized determined, and the results embodied in a carefully prepared design. It is a very usual custom, and perhaps a natural one, for the press, when the design is made public, to compare it with some similar vessel of a foreign navy whose conditions of service are very dissimilar, sometimes to the seeming disadvantage of the proposed vessel, especially when such criticism may have been suggested by private builders who desire greater latitude in certain directions, and the general public may receive the impression that the best has not been attained; but to those who know the care and study given to the preparation of the design. in view of the service required, and are able to comprehend fully its military value, the conclusion is very different. Taking, then, our battle-ships, we find the highest representative in the Iowa (Fig. 1), now building at the Messrs. Cramp's, which has a displacement of 11,250 tons, and carries a battery of four

12-inch, eight 8-inch, and ten 4-inch breech-loading guns, besides twenty machine guns and six tubes for discharging 18-inch automobile torpedoes. It is one thing for a vessel to carry a large battery capable of firing a tremendous weight of metal when all the manipulating apparatus is in perfect order, but quite another in these days of high explosives to have that battery and apparatus securely protected from the guns of its antagonist, therefore the 12-inch forty-four-ton guns of the Iowa are mounted in pairs in turrets having walls of solid steel fifteen inches thick, and protected from the water-line up by steel of the same thickness, which effectually protects the loading, turning, and controlling mechanisms. In order that these guns may be fought in heavy weather the forward turret is placed on a forecastle deck with the axis of the guns some twenty-five feet above the load line, and has a train of three hundred degrees, or only sixty less than a complete circle; the after 12-inch guns are mounted in the same manner, but on a deck seven feet nearer the load line. Both forward and after turrets are placed in the mid line of the vessel, in order to have a great train and be as free as possible from the motion due to rolling; the turrets are revolved by steam power at the rate of one revolution per minute. Some idea of the power of these guns may be obtained from the following data: The weight of one powder charge is four hundred and twentyfive pounds; that of the projectile, eight hundred and fifty pounds; its muzzle velocity, 2,100 feet, or four tenths of a mile per second; the muzzle energy, 25,985 foot tons, or capable of raising that amount one foot in a minute, with a penetration in wrought iron of 276 inches. The 8-inch guns are also mounted in turrets, having great range, and are protected by armor varying from ten inches to seven inches and a half in thickness; the ten 4-inch guns, each discharging projectiles of thirty-six pounds weight at the rate of ten rounds per minute, are protected by fixed segmental shields four inches thick.

While so much has been done to develop the battery and its protection, the features of defense, stability, speed, and endurance have received most careful attention; the magazines, boilers, engines, steering mechanism, etc., are all inclosed in a belt of steel, covering about sixty-five per cent of the load-line area, of a maximum thickness of fourteen inches, and extending fr in three feet above to five feet below the load line; at the upper edge of this is worked from side to side of the vessel a horizontal deck three inches thick (see Figs. 2 and 3); above this, to protect the stability, a steel belt four inches in thickness is worked to the main deck, and at the unarmored ends double coffer dams six feet wide, the outer one filled with obturating and the inner one with water-excluding material, are provided as shown in Fig. 4.