The idea of armor-plate is, as has been said, scarcely half a century old, and the moment it was put on (amid the jeers of the old line-of-battle tars, who thought they had done all that the dignity of the profession permitted when they arranged their rolled-up hammocks along the bulwarks to catch musket-balls, and spread nettings to prevent somewhat the flight of splinters) ingenious men began to improve their powder and strengthen their guns to overcome the new defenses. To meet these improvements armor has been increased and perfected, until now war-vessels are no longer “ships” in any proper sense of the word, but floating fortresses of steel, the names of whose defensive parts, even, have been borrowed from land fortifications, such as _turret_ and _barbette_. [Illustration: THE UNITED STATES BATTLE-SHIP “MASSACHUSETTS.”] A limit to this defensive strength is marked in two directions. First, by the size it is possible to make a vessel, and still keep her seaworthy and manageable; and, second, by the weight of armor such a vessel can carry, in addition to the weight of the framework, machinery, guns, and other things necessary. These limits seemed to be reached some time ago in some of the monstrous battle-ships built in Europe, and when it was found that even while they were in construction rifled guns had been invented that would drive their projectiles through the thickest wall of wrought-iron or steel that these or any other vessels could carry, naval constructors began to despair of keeping ahead of the gun-makers, and there was even talk of abandoning armor altogether, and fighting battles out with bared breasts as we used to do. The percentage of weight which may be allotted to armor in the design of a ship limits the area which can be wholly protected, but often permits the partial protection of other areas of less importance to her vitality and destructive force. Motive power, steering-gear, and magazines stand first upon the list of those features demanding complete protection.... The heavy shells from an enemy’s guns may do many other forms of injury besides sinking a vessel and disabling her crew. They may strike and disable her engines, or pierce her boilers, causing disastrous explosions. They may injure her steering-gear, destroy the mechanism which controls her turrets and guns, or injure the guns themselves and their carriages. In every feature of offense which renders her a formidable and dangerous foe—her speed, her mobility, the fire of her guns—a man-of-war is dangerously vulnerable unless she be protected by armor, unless the enemy’s shot be rejected by plates which it cannot penetrate.