factured without difficulty. In 1861 a target representing a section of the 'Warrior,' and consisting of a 4½-in. iron plate, with 18 in. of teak backing, and an inner iron skin ¾ in. thick, was fired at with a Whitworth rifled gun throwing a flat-headed steel bolt of 80 lbs. The target was indented and cracked, but not perforated.
In 1862 Mr Brown was able to roll at his works at Sheffield, in the presence of Lord Palmerston, an iron plate 18 ft. long, 4 ft. wide, and 5½ in. thick. The following year, when the Lords of the Admiralty visited his works, at the opening of a new rolling mill, the energetic manufacturer showed that plates up to a thickness of 12 in. could be produced.
From that time there was no difficulty in supplying the increased protection demanded for the new ironclad navy, till in the 'Dreadnought' we placed on the hull and turrets plates 14 in. thick. Though the water line amidships of the 'Inflexible' has 24 in. of iron, it is not in one but two plates, each 12 in. thick, with a layer of wood between them.
But already there were indications that no increase in the thickness of wrought-iron plates would suffice to resist the growing energy of the gun. As early as 1869 a Krupp gun of 11 in. calibre had perforated 12 in. of iron and 36 in. of wood. Our own 38-ton gun pierced 19 in. of iron in 1876, and the following year the 80-ton gun sent its projectile through three 8-in. iron plates. In the meantime Mr Schneider had been developing at Creusot, in France, the manufacture of steel plates, and some experiments at Spezzia, in Italy, showed the soft-
