In the same year the Cunard Line followed with the _Carmania_, their first turbine liner, fitted with three turbines and three screws. She was preceded a little by the _Caronia_, a sister ship in every way except that the latter is propelled by two sets of quadruple-expansion reciprocating engines, driving twin-screws. These ships have a displacement of 30,000 tons, and a length over all of 675 feet. They were built of a strength that was in excess of Board of Trade and other requirements, and when we state that no fewer than 1,800,000 rivets were used in the construction of each, one begins to realise something of the amount of work that was put into them. Their steel plating varies in thickness from three-quarters of an inch to an inch and an eighth in thickness, the length of each plate being 32 feet. Fitted with a cellular bottom which is carried well up the sides of the ship above the bilges, they can thus carry three and a half thousand tons of water-ballast. The principles underlying the design and construction of these ships were steadiness and strength, and in the attainment of this they have been eminently successful. There are eight decks, which may be detailed by reference to the photograph of the _Carmania_ facing page 188. Immediately below the bridge is the boat deck. Then follow successively the upper promenade deck, the promenade, the saloon, upper, and main decks. Below the water-line come two other decks for stores and cargo, the depth from the boat deck being eighty feet. Both of these ships are fitted with the now well-known Stone-Lloyd system of safety water-tight doors, which renders the vessel practically unsinkable. This enables the doors to be closed by the captain from his bridge, after sufficient notice has been given by the sounding of gongs, so that everyone may move away from the neighbourhood of these doors. But should it chance that, after they have been shut, any of the crew or passengers have had their retreat cut off, it is only necessary to turn a handle, when the door will at once open and afterwards automatically shut again. The system is worked by hydraulics, and is a vast improvement on the early methods employed to retain a ship’s buoyancy after collision with an iceberg, vessel or other object. A glance at the illustration will show that a very great amount of consideration was paid to the subject of giving the _Carmania_ a comprehensive system of ventilation, a principle which has been carried still further in the _Mauretania_ and _Lusitania_. In the event of war the _Carmania_ and _Caronia_ would be fitted with twelve large quick-firing guns, for the hulls were built in accordance with the Admiralty’s requirements for armed cruisers. For this reason, also, the rudder is placed entirely under water, and besides the ordinary set of steering gear, there is another placed below the water-line. [Illustration: A STUDY IN COMPARISONS: THE “MAGNETIC” AND “BALTIC.”