Armor plate has been much improved in recent years. During the Civil War the armor on our monitors was only an inch thick. Through such an armor the projectiles of our time would penetrate as easily as a bullet through a pine board. It was the development of gun power and projectiles that called forth the thick armor, but it was soon found that it was impossible for the armor to keep pace with the deadliness of the guns as it was utterly impossible to carry the weight necessary to resist the force of impact. Then came the use of special plates, the compound armor where a hard face to break up the projectile was welded to a softer back to give the necessary strength. This was followed by the steel armor treated by the Harvey process; it was like the compound armor in having a hard face and a soft back, but the plates were made from a single ingot without any welding. The Harvey process enabled an enormously greater resistance to be obtained with a given weight of armor, but even it has been surpassed by the Krupp process which enables twelve inches of thickness to give the same resistance as fifteen of Harveyized plates. The armament or battery of warships is divided into two classes, viz., the main and the second batteries. The main battery comprises the heaviest guns on the ship, those firing large shell and armor-piercing projectiles, while the second battery consists of small rapid fire and machine guns for use against torpedo boats or to attack the unprotected or lightly protected gun positions of an enemy. The main battery of our modern battleships consists usually of ten twelve-inch guns, mounted in pairs on turrets in the centre of the ship. In addition to these heavy guns it is usual to mount a number of smaller ones of from five to eight inches diameter of bore on each broadside, although sometimes they are mounted on turrets like the larger guns. A twelve-inch breech-loading gun, fifty calibers long and weighing eighty-three tons, will propel a shell weighing eight hundred and eighty pounds, by a powder charge of six hundred and twenty-four pounds, at a velocity of over two thousand six hundred and twenty feet per second, giving an energy at the muzzle of over forty thousand foot-tons and is capable of penetrating at the muzzle, forty-five inches of iron.