All the big guns, which are mounted in pairs in turrets on the centre line, can fire on either broadside. Protection is afforded by a 12-in. armour belt amidships, with thinner plating above and at the ends. The turrets are of 11-in. armour. The secondary battery of 4-in. quick-firers is practically unprotected. A maximum fuel supply of 2,700 tons can be carried. The complement is 900 officers and men. Each of these ships cost more than £1,900,000 to build and equip. ORION CLASS. (Completed 1911-12.) ORION. MONARCH. CONQUEROR. THUNDERER. Super-Dreadnoughts of 22,500 tons displacement and 545 ft. in length. The Orion class, to which these ships belong, inaugurated the “super-Dreadnought” era by reason of the super-calibre guns with which they are armed. They are propelled by Parsons’ turbines of 27,000 h.p. at a speed of 21 knots, but did considerably better than this on the trial runs. The main armament comprises ten 13·5-in. breech-loading guns, firing a 1,250 lb. projectile at the rate of two per minute. These guns are mounted in five twin turrets on the centre line of the vessel, and all of them can be trained on either broadside. Sixteen 4-in. quick-firers are mounted for use against torpedo craft, and there are three 21-in. submerged torpedo tubes. The armour belt is 12-in. thick amidships, the turrets 11-in. Some of the smaller guns are protected by 4-in. armour. Coal and oil to the amount of 2,700 tons can be carried. The complement of these ships is 900 officers and men. They cost complete nearly £2,000,000. NEPTUNE CLASS. (Completed 1911.) NEPTUNE. HERCULES. COLOSSUS. These are Dreadnought battleships of 20,000 tons displacement. They are 510 ft. in length, and have Parsons’ turbines of 25,000 h.p., which give them a speed of 21 knots. The main battery consists of ten 12-in. guns, 50 calibres (_i.e._, 50 ft.) long, mounted in five twin turrets. Two of these turrets are in echelon amidships, the remaining three being on the centre line, an arrangement that permits all ten guns to come into action on either broadside through a limited arc. In the class to which these ships belong the super-posed turret appeared for the first time in the British Navy. Sixteen 4-in. quick-firers and three submerged torpedo tubes complete the armament. There is an 11-in. armour belt on the waterline, similar protection being given to the big guns. The fuel capacity is 2,700 tons. The complement numbers over 800 officers and men. These vessels cost about £1,700,000 apiece to complete. ST. VINCENT CLASS. (Completed 1910.) ST. VINCENT. VANGUARD. COLLINGWOOD.