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PLATE VI.THE DISTRIBUTION OF ARMOR.

PLATE VII. THE DISTRIBUTION OF ARMOR.

General Paixhans, who revolutionized naval artillery by the invention of the modern shell, prophesied, in an official letter to the French government in 1824, that the new projectile would force the creation of armored ships. In 1841 he recommended officially the clothing of vessels with iron armor, as a protection against his own missiles; and in 1853 his words of warning met complete and terrible fulfillment in the annihilation by shell guns of the Turkish fleet at Sinope. This action was the immediate cause of the introduction of armor in modern navies.

The British admiralty, in 1843, had duplicated the Stevens experiments, using a target of 14 plates of boiler iron riveted together, which gave a total thickness of 6 inches; and experiments on laminated plating had been also at this time carried on at Gavres, in France. In 1845 Dupuy de Lôme, the famous naval architect, submitted to the French government the first European design for an armored frigate. His plans were, however, rejected; and only with the outbreak of the Crimean War was the construction of armored vessels begun. On October 17, 1855, the three French batteries which were the first results of this new departure went into action off Kinburn, in the Crimea, silencing in four hours forts which had held at bay the combined fleets of England and France. Armor had won its first victory, and had shown most signally its position as one of the main factors in the warship design of the years which were to come.

These vessels, with three similar batteries constructed immediately thereafter by the British government, were clad with solid iron plates 4½ inches thick, backed by 27¾ inches of oak, comparative experiments at Vincennes, France, having shown the marked superiority of solid over laminated plating. They were, however, in but a most limited sense sea-going ships, their low speed and other inferior qualities being radical defects as to this. France led in a further advance, beginning in 1857 and completing in 1859 the transformation of the wooden line-of-battle ship Napoleon into the armored vessel of 5000 tons, which, as La Gloire, is famous as the first sea-going ironclad. She carried a strake of 4¾-inch plating at the water line, and 4½-inch plates in wake of the battery. England answered the challenge of her hereditary foe with the Warrior, an iron vessel of 9210 tons, completed in 1861. While her rival had a fully armored side, but 212 of the Warrior’s 380 feet of length carried plating. Its thickness was 4½ inches.

“La Gloire” (France) 1857. Side Armor Iron 4½ in. Solid. “Warrior” (England) 1859. Side Armor Iron 4½ in. Solid. U.S. Monitor “Passaic” 1862. Side Armor Iron 3 to 5 in. Laminated. Turret Armor Iron 11 in. Laminated. “Inflexible” (England) 1876. Belt & Citadel Armor Iron Sandwiched. “Duilio” (Italy) 1876. Belt Armor Steel Solid. U.S. Battleship Oregon. Belt Armor Harveyed Nickel Steel Solid. 13 in. Turret Armor Harveyed Nickel Steel Solid.

PLATE VIII. THE GROWTH OF ARMOR.

At the outbreak of the Civil War in the United States, the government appointed a special naval committee to report upon types of ironclads. The conclusions of this board are of interest, in showing the state of armor development at that period. They required rolled armor of solid iron, whose minimum thickness was 4½ inches. Ericsson’s Monitor, however, carried laminated plating from 3 to 5 inches thick on her low sides, and 11 layers, each one inch thick, on her turret. This construction, which the difficulties in the manufacture of solid plate necessitated, made the record of endurance of this type far from good. The defect lay mainly with fastening bolts, which broke frequently, thus loosening or detaching the side armor, and the heads or nuts of which, flying off with violence when the armor was struck by shot, became sometimes fatal missiles against those within the turrets. In contrast with this, the behavior of the New Ironsides, clothed with solid armor, was most excellent. She was a casemated ironclad frigate with unarmored ends, her plating was 4½ inches thick, and inclined throughout the citadel, at an angle of 30° from the perpendicular. For two years she was subjected to the most severe test that a war-vessel must meet, the tossing and straining of blockade duty and the fiery ordeal of close action with fortifications. In one engagement, she sustained alone a fight against the combined fire of the forts in Charleston harbor, and, although struck on her side-armor sixty times, came out of the struggle unhurt. The record of this ship is one which does honor to the flag.

The achievement of the Confederacy during this war, in the matter of armor, was remarkable. With iron worth almost its weight in gold, and with most limited facilities for manufacturing, they yet succeeded in constructing some of the most formidable ironclads of their day. The Merrimac, for instance—with 3-inch armor, in two layers of narrow bars, at an angle of 30° with the horizontal—sustained no material damage to her plating from the fire of the Monitor; although had the full charge of 30 lbs. of powder been used in the 11-inch smooth-bores of the latter, the story would have been different. Every fair blow would have smashed a hole completely through the armor, and driven a shower of splinters about the battery-deck. Again, the armor of the Atlanta and the Tennessee—both casemated ships, with the sides of the citadel inclined at a sharp angle to the horizontal—was sufficiently strong, with the former vessel, to withstand, at 500 yards, the 11-inch projectile fired with a 20-lbs. charge, and, with the latter, the same shot practically at the muzzle, although the 15-inch projectile broke through completely in both cases.

It is unnecessary to follow in detail, through its many tests in peace, the advance of iron armor. Its growth in strength, as the power of the gun developed, came almost solely from increase in thickness, the latter reaching its maximum with the British Inflexible, completed in 1876, which carries from 16 to 24 inches of iron on her belt and citadel. This plating, however, is divided and “sandwiched” with wood, there being, exterior to the skin, 6 inches of teak, then 12 inches iron, 11 inches teak, and an outer 12-inch plate. As armor, iron received its death-blow in the famous tests at Spezia, Italy, during the autumn of 1876, when the 100-ton gun, with a full charge, at a range of 100 yards, attacked solid and “sandwich” targets of iron and solid targets of steel—the single or aggregate thickness of metal in each case being 22 inches. These trials were undertaken through Italy’s desire to build, in the Duilio and Dandolo, the most formidable vessels afloat. Steel won the day, and the roar of that mighty gun, thundering from the Spezia firing ground, sounded the knell of iron armor, deprived the as yet unlaunched Inflexible of her crown of invulnerability, and demanded, with success, a revolution in the armor manufacture of Europe.

As a compromise, compound armor, i.e., iron faced with steel, became popular for a time. As with steel, its beginnings were old, dating back at least to the year 1857. The first perfected compound plate, made by Cammel & Co., of England, was tested at Shoeburyness in 1877. It was composed of 5 inches of iron with a 4-inch face of steel; the iron being raised to a welding heat and the molten steel poured on its top. The great heat partially fused the contact face, the two metals were united, and the combination was assured by immediate rolling. Compound plates sprang in 1877 from obscurity to popularity; by 1879 iron armor had become obsolete with progressive naval powers, and, in 1880, both compound and steel plates had reached such development that they were close rivals, the leading competitors being Cammel in England and Schneider in France. Steel, however, slowly forged ahead during the next decade; and, at its close, compound armor was practically out of the race. In steel’s victory, its alloy with nickel, in minute proportions, has materially aided; the combination imparting hardness without decreasing the toughness of the plate. This material gave superior results from the beginning. Its first plate, tested in 1889, was 9⅓ inches thick; it was pierced by a Holtzer shell, whose body did not pass wholly through and whose energy was 1.6 times that just necessary to perforate a wrought-iron plate of the same thickness. To the increased strength given by nickel there has been added a further gain through the application of face-hardening processes—such as that of the American, Harvey—which produce superficial carbonization, transforming the surface into a high grade of very hard steel, without the pronounced plane of demarcation between the two qualities of metal, as in the weld of the compound plate. A 10¼-inch nickel steel Harveyized plate, tested at the Indian Head Proving Grounds in 1892, showed a strength which previously had never been equaled in the history of armor, and established beyond question the value of the face-hardening process, which, by various methods, is applied to the nickel-steel plating of to-day. The distribution of armor in the development of battleship construction is shown by the shaded sections on Plates VI and VII, and its relative thicknesses, on various vessels during this progress, by Plate VIII.