The heavy sea-coast guns are now mounted either in armored turrets, _en barbette_, or on disappearing gun-carriages. The first system is very costly and is not generally used in the United States. The second system, in which the guns are fired over a parapet and are constantly exposed, is used only in rare cases. The third has been perfected in the United States in the Buffington-Crozier and the Gordon disappearing gun-carriages. These carriages enable the gun to be loaded in safety under cover of the carriage pit, and then to be raised by means of counterweights or compressed air to a position from which it can fire over the parapet. With trained cannoneers, the gun can be raised and fired in twenty seconds, and this brief period of exposure, especially when smokeless powder is used, renders it almost impossible for the enemy to locate the gun with any degree of accuracy. The shock of the recoil, taken up by pneumatic or hydraulic cylinders, brings the piece back, quickly but gently, to the loading position, whence it is again raised for firing. The siege artillery of the United States army consists of the 5-inch gun, the 7-inch howitzer, and the 7-inch mortar. They all use shell, and their effective range is from three to four miles. When the enemy is sheltered behind entrenchments it is difficult to reach him with shrapnel fired from field guns. Field mortars have accordingly been devised for this purpose and have given excellent results. The United States 3.6-inch field mortar is rifled, and carries a shrapnel weighing twenty pounds. The weight of the field mortar is only 500 pounds, and it can be easily carried in a cart drawn by a single mule. [Illustration: KRAG-JORGENSEN RIFLE.]