With the centre line system, the imposition of fighting one side rather than the other is not imposed, and overhauling or being overhauled causes no disadvantage. Nothing is lost, save in the almost hypothetical case of two ships engaging exactly end-on--a condition which in no case would endure for more than a very short space of time, to say nothing of the fact that practically all gunnery errors being of “elevation” and not of “direction,” a ship adopting the end-on position offers the equivalent of a vertical target of some 60ft. to 70ft. instead of the equivalent of 30ft. or so that she would present broadside on. The centre-line system may, therefore, be expected to endure against all other dispositions pending the appearance of some fresh condition of affairs which would cause the old end-on idea to be reverted to.[35] [Illustration: DIAGRAM TO ILLUSTRATE WEAK POINT OF THE ÉCHELON SYSTEM.] The _Orion_ was the only one of her class which belonged to the normal Estimates, 1909–10, the other three--_Conqueror_, _Thunderer_, _Monarch_--being “contingent ships.” Details of the class are as follows:-- Displacement--23,500 tons. Length--(between perpendiculars) 554½ft; (over all) 584ft. Beam--88½ft. Draught--(mean) 27¾ft. Armament--Ten 13.5-inch, forty-five calibre; sixteen 4-inch; three 21-inch torpedo tubes. Armour Belt--12--4-inch. Turrets, 12-inch. Machinery--Parsons turbine. Horse-power--27,000 = 21 knots. Boilers--Babcock. Coal--(nominal) 900 tons; (maximum) 2,700 tons; oil, 1,000 tons. ============+=============+============= Name. | Built at. | Engines by. ------------+-------------+------------- _Orion_ | Portsmouth | Wallsend Co. _Conqueror_ | Beardmore | Beardmore _Thunderer_ | Thames I.W. | Thames I.W. _Monarch_ | Elswick | Hawthorn ============+=============+============= The _Orion_ was laid down in November, 1909, the others in April, 1910. The _Orion_ was the first of these ships to be commissioned, and her gunnery trials were watched with great interest. Few details of them transpired, save that part of the secondary battery was injured by blast. After commissioning, the _Orion_ was sent for a voyage across the Bay of Biscay, and attracted much attention by rolling very heavily, this being attributed to the fact that her bilge keels were not large enough--not to any general structural defect. An interesting feature of the _Orion_ type is that in it provision first appears for the protection of boats in action. Belonging to the same programme (1909–10), the first belonging to the normal Estimates and the second to the “contingent,” are the battle cruisers _Lion_ and _Princess Royal_. A great deal of secrecy was observed about these ships, but their main details are approximately as follows:-- Displacement--25,000 tons. Full load, 26,350 tons. Length--(water-line), 675ft.; (over all) 690ft. Beam--86½ft.