Armor Plates
slabs of metal with ered for the purpose of rendering them on against miswhich the sides of war vessels are covshot-proof. The idea of using slabs of iron or steel for protection against misiron or steel for protection siles is not a recent invention. The first attempt to use armor-plate on the sides of ships was made by John Stevens, of Hoboken, in 1812. He built a vessel shaped somewhat similar to the later vessels of the "Monitor" type, and sheathed it along the water line with laminated iron plates. His vessel was offered to the United States Government they sent floating batteries to the Black but was not accepted. The French were the first to adopt armor-plating. In 1854 Sea, sheathed with 43 inches of laminated iron, which was proof against the fire of the 68-pounders, then the most powerful guns. The British admiralty, following this example, sent out very slow and unmanageable iron-clad batteries in 1855-1856. These batteries proies in 1855-1856. These batteries protected the ships very well against round day. It was not, however, till the Ameri- The Confederate ram can Civil War that armor-plating came into general use. "Merrimac" was the first practical arcan Civil War that armor-plating came into general use. The Confederate ram "Merrimac" was the first practical arher sheathing consisting of railroad rails. Her successful opponent, the "Monitor," her sheathing consisting of railroad rails. iron plates extending several feet below the water line. which may be carried on a ship may be penetrated. A Kruppized plate, eight inches thick, resisted a shell striking it ARMORY Harvey introduced the process of carbonizing the face of armor-plate, greatly increasing its hardness. The plate, having been placed in a furnace, is covered with a layer of carbonizing material about a foot thick, over which is laid a covering of brick to exclude the flame and air from the carbonizing material. The doors of the furnace are bricked up and a high heat maintained for about 100 hours. The plate is removed and its surface cleared when cold, it is then reheated, and sprayed with cold water, producing an exceedingly hard surface. This Harveyized steel was used for nearly all the American and foreign men-of-war, until, in 1895, a process was discovered at the iron works of Krupp, at Essen, by which the face of the plate was made so hard that it cut glass like a diamond, while the back remained so tough that it would suffer no injury from cracks when struck by a projectile. The Krupp process is somewhat similar to, and an improvement on, the Harvey process.
A Harveyized plate has been pierced to a depth of 14 inches by a 6-inch softcapped projectile, so that the cap showed on the back. The Krupp armor is perforated, but not cracked, by a projectile with a velocity exceeding 2,500 feet per second. The Harvey plate is cracked but rarely perforated at a velocity of less than 2,000 feet per second. The projectiles used for testing purposes vary from 100 pounds to 850 pounds in weight.