ness of wrought-iron as compared with steel. The latter resisted penetration to a much greater extent, though it had a tendency to break up when attacked by numerous comparatively light projectiles. From this moment plates composed entirely of wrought-iron were doomed. The manufacturers of them in this country—Messrs Brown and Messrs Cammell—then proposed compound armour. In Cammell's method—which is according to Wilson's patent—a wrought-iron plate is put into a box, placed in a vertical position, and liquid steel poured in between one side of the plate and the side of the box. The composite plate thus made is then rolled, by which process the steel face is hardened and made to adhere rigidly to the wrought-iron foundation. In Brown's method—which is according to Ellis's patent—instead of a box, a thin steel plate is placed at the required distance from the iron plate and the melted steel poured in between the two, making the whole a solid mass. It is then reheated and passed through the rolling mill. In both systems the steel face is about one-third the total thickness. In 1877 experiments with compound armour plates showed their superiority to wrought-iron, and consequently it was decided to place them on the 'Inflexible's' turrets. In 1880 a compound plate made by Messrs Cammell, in which the steel face was 5 in. and the wrought-iron back 13 in. thick, was fired at by the 38-ton gun, with a Palliser chilled shot, the result being that the projectile broke up on impact with the plate, and effected no damage beyond slight indentation and surface cracking. It was
