Cartridge Case and Grains of Powder, U.S.N. 220 Common Shells, U.S.N. 220 Unburned and Partially Consumed Grains of U.S.N. Powder 222 Section of U.S.N. 6-inch Built-up Steel Breech-loading Rifle 222 Broadside Carriage for 6-inch Breech-loading Rifle 223 Rapid-firing Single-shot Hotchkiss Gun 224 New 6-inch Breech-loading Rifle 238 Longitudinal Plans of Nordenfeldt Boat 254 The Submarine Monitor “Peacemaker” 257 MODERN SHIPS OF WAR. INTRODUCTORY CHAPTER. During the last thirty years the changes in naval science have been so much greater than in its whole previous history as to be epoch-making. Between the wooden vessel of 1857 and the metal machine of 1887 there exist in common only the essential principles that each is a water-borne structure, armed with guns and propelled by steam. Beyond this everything is changed—model, material, machinery, rig, armament, equipment. In truth, so radical are the differences, and so sudden have been the developments, that authorities are widely separated in opinion, even upon such a primary question as a universally accepted system of classification. But as this is necessary to a proper appreciation of the subject, a generalization may be made in which war-vessels are divided into armored and unarmored types, the former including battle-ships, and the latter those employed in the police of the seas, in commerce protection or destruction, or in the attack of positions which are defenceless.