The advance in artillery took place in connection with Italian construction. In 1872 Italy laid down the _Duilio_, and a year later the _Dandolo_, two mastless turret ships of a novel class, engined by Penn and Maudsley, and equipped with two diagonally placed turrets each designed to carry two 60-ton Armstrong guns; guns which were afterwards changed to 100-ton guns of 17¾ inches bore. In the same ships the Italians introduced a solution of the armour difficulty. They abandoned vertical armour altogether, except for a very thick belt over the central portion of each vessel which was to protect the vital machinery and the gun turrets. The reply to these was the _Inflexible_, laid down in ’74. We have already seen how, in the last of the _Devastation_ class, the central armoured breastwork was widened to the full beam of the ship. It had been proposed by Mr. Barnaby to take advantage of this arrangement to off-set the two turrets of the _Dreadnought_ at a distance each side of the centre line of the ship, so as to allow a powerful ahead fire. Although not then approved, this suggestion was embodied in the _Inflexible_ as her most distinctive feature. In this, however, she was forestalled by the Italians. Her two turrets, each weighing 750 tons, were carried diagonally on a central armoured citadel plated with compound armour of a maximum thickness of 24 inches. Forward and aft of this citadel the unarmoured ends were built flush with it, and along the centre line was built, the whole length of the ship, a narrow superstructure. This superstructure did not contribute anything to her stability; nor was such contribution needed in view of the comparatively high freeboard. But it rendered unnecessary a flying deck such as had been fitted in the _Devastation_ class, and provided accommodation for the crew, without restricting to any appreciable degree the arcs of fire of the big guns. The _Inflexible_ was of over 11,000 tons displacement, the heaviest and most powerful warship that had ever been built. She was 320 feet in length and 75 feet broad at the water-line; this unprecedented beam being required, in spite of the high freeboard, on account of the height at which the turrets were carried. Nevertheless, so improved was her propulsive efficiency as compared with that of former ships, so great the gain resulting from Mr. Froude’s historic researches on ship form and the action of propellers, that a speed of 15 knots was obtained at a relatively small expense in horse-power.