Our coast fortifications are for the purpose of protecting coast cities, naval bases and other utilities from bombardment, of preventing the occupation of harbors by an enemy and of providing safe harbor for our fleet. For these purposes large caliber guns and mortars of great power have been mounted on concrete emplacements and supplied with necessary accessories in the way of searchlights, submarine mines, observing and range finding stations. Of the two systems of guns in use in coast artillery, the high power guns with a flat trajectory (those shooting in a straight line) are designed to pierce the side armor of battleships ; the high angle pieces, howitzers or mortars, are for the purpose of throwing a projectile on the decks. The former has the greatest accuracy and the latter attacks a ship at its weakest point. A gun of at least 12-inch caliber is required to pierce the armor of a battleship. Twelve-inch guns were placed in many of our coast defenses several years ago. They are mounted on disappearing carriages, and, when fired, the gun rises above the battlement for a moment, sends forth its shell, then sinks down again concealed behind the fortification. The 12-inch gun weighs 52 tons and fires a shell weighing 1,070 pounds, which travels 2,250 feet per second and can pierce the vitals of a battleship 6 miles away, or perforate the casement armor of one 11 miles away. This type of gun shoots in a straight line. The 12-inch guns have been thought insufficient to protect against the modern battleship and some have been replaced by new 16-inch guns.