Page:The Development of Navies During the Last Half-Century.djvu/111

 When turrets were first introduced steam was employed to rotate them, and also, as the guns increased in weight, for many of the operations connected with their manipulation. But steam has the disadvantage of condensation in pipes when transmitted, and for such a delicate manœuvre as keeping the sights of a gun on a mark, which was effected by small movements of the turret, steam power has defects. Hydraulic power was therefore devised by Sir William Armstrong and Mr G. Rendel, of the Elswick firm, to perform all these operations, and applied in the ’Inflexible' with great success. The heavy turrets could be rapidly swung round or rotated with almost imperceptible motion, and stopped dead at any required moment.

From the day on which we had begun to construct warships of iron it became necessary to guard against injury in the event of such a vessel striking the ground or rock. A wooden ship might do this and suffer little damage or danger of foundering, as the material, being more elastic, had a tendency to close in over the fractured part, and swell as it became sodden with water. Iron did not possess this advantage, and, moreover, to give the requisite buoyancy the submerged portion of the hull must necessarily be thin, so that injury was easily inflicted in this part. Even at the slowest speed the momentum of a weight of 9000 tons coming in contact with a rock would crush in the fragile shell like matchwood. To meet this the double bottom was devised, which consisted in having an