While the increase of armour kept pace with the growth of the guns, and rose gradually from four inches on the _Warrior_ to two feet on the _Inflexible_, a species of internal defence was gradually developed by the division of the ship into numerous compartments; so that if she were pierced below the water-line by the explosion of a torpedo or the blow of an enemy's ram, the water would only partially fill her, and she would still be able to keep afloat. All the later iron-clads have a double bottom, the space between the inner and outer bottom being divided into numerous cells. The body of the ship is divided by the water-tight bulkheads extending from side to side, and from the bottom to the upper deck. To these transverse bulkheads Mr Barnaby, the present chief constructor, has added in all the iron-clads which he has designed a longitudinal bulkhead extending from stem to stern, and dividing the ship into two halves in the direction of her length. Further, there are minor compartments formed by strong bulkheads, designed for the protection of the engines and boilers. In a large ship these compartments of various kinds are very numerous; the _Inflexible_ contains upwards of one hundred and twenty; great care, therefore, has to be taken in planning them, in order to insure that this isolation of the various parts of the ship may not interfere with the working of her guns, engines, and steering apparatus while she is in action. Side by side with this development of defensive power, there went on an equally rapid development of machinery and mechanical appliances for the working of the ship. The first necessity of an iron-clad is powerful engines, to drive her at a speed of thirteen or fourteen knots an hour on an emergency, though of course in ordinary times a much lower rate of speed is considered sufficient, and the engines work at half their power, or are stopped entirely, while the ship proceeds on her way under sail. But the propulsion of the ship is only one of the numerous duties to be discharged by this new adoption of steam, a power which was only just really establishing itself in our navy when we went to war with Russia in 1854. An iron-clad does not carry anything like the crew that used to be put on board of an old three-decker. Eleven hundred men used to be the complement of a ship of one hundred and thirty-one guns; one-third of the number is more than the crew of some of our most formidable vessels of to-day. In former days guns could be handled and worked by men and even by boys, provided the number of hands were sufficient; and nowadays it is very different work running in and out guns weighing thirty-five, thirty-eight, and eighty-one tons, and dragging along and ramming down shot and shell weighing from six hundred pounds up to three-quarters of a ton, and cartridges each of which contains perhaps more than two barrels of gunpowder. This kind of fighting is work for giants, and so the giant Steam lends his