Page:The Development of Navies During the Last Half-Century.djvu/134

 for protecting the machinery employed in the manipulation of the heavy guns. The ends of the vessel have no external armour, but a steel deck will confine any water that may enter, from this portion being penetrated by projectiles, and prevent it from flooding the ship. Even if the spaces at each end were so filled, the trim of the vessel would be little affected. To drive a floating weight of 14,000 tons through the waters obviously requires powerful machinery, and as it was considered desirable that these vessels should have a speed of 16 knots without pressing the engines, and under ordinary atmospheric draught for the fires, while with forced or artificial draught the speed should be capable of being increased to 17½ knots, boilers and engines are being provided equal to the development under the latter condition of 13,000 horse power. As there will be two sets of engines for revolving twin screws, each set will be of 6500 horse power. When we remember that the 'Warrior' had a single engine of 5000 horse power, which propelled her at 14 knots, it can be realised what a vast increase of power is required to obtain the additional 3½ knots, notwithstanding the great improvements in steam propulsion since that time. In the 'Collingwood', a vessel of the same displacement as the ’Warrior,' to pass from 14 knots to 17 knots required practically the horse power to be doubled. At moderate speeds modern marine engines are economical in coal consumption, but beyond a certain rate the fuel rapidly disappears. A large supply is therefore essential, and in the new battle ships the amount is fixed at 900 tons.