to purposes of protection, a style of construction now universally adopted and known as cellular was developed by Sir E. J. Reed, then chief constructor of the British Navy, in which the maximum of strength with the minimum of weight was sought after and very fairly obtained. Then began, what has continued to this day, the race between armor and armament; the makers of armor striving to make plates that would effectually resist the largest guns, and the gun-makers using every means at their command to produce guns capable of breaking up or penetrating the heaviest armor. The outcome is, on the side of armor, the solid steel plate with a face case-hardened by the Fig. 2.—Iowa. Section through Armor. Harvey process—a face so hard that no drill will in the slightest degree affect it, and this extreme hardness gradually shaded off to a soft back to prevent through cracks. On the other hand is the steel built-up breech-loading gun, with a length of from thirty-five to forty-five times its diameter of bore, using slow-burning powder, having low initial pressures and giving a muzzle velocity from two thousand to twenty-five hundred feet per second, and special steel armor-piercing projectiles for the purpose of racking or breaking up the armor and then piercing the hulk This competition has indirectly opened up a new material of some twenty per centum greater strength when compared with wrought iron, known as mild steel, which naval architects are employing to enable them to produce lighter structures, and to use the weight saved in giving greater thickness to the armor, increased armament, or added power and speed, as the necessities of the design contemplated may demand. Shortly after the introduction of this material, or in 1882, the Congress of the United States appropriated for the construction of three cruisers and one dispatch boat, which are now familiar to us all under the names of the Chicago, Boston, Atlanta, and Dolphin; fortunately for our Government, its corps of naval constructors and engineers had by repeated visits to the ship-yards and gun factories abroad, and a close study of the principles involved in the new methods of construction, kept themselves fully
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THE POPULAR SCIENCE MONTHLY.