The central armoured citadel protecting the machinery and boilers and the magazines, besides part of the machinery for working the turrets and the guns, was no less than 58 feet in breadth, and extended to within a fraction of 6 feet below the load water-line, and was 107 feet in length. Above the citadel was a second central armoured compartment protecting the turret bases and a part of the machinery for loading and working the guns; and above this compartment were the turrets themselves. The turrets of the _Duilio_ were not placed amidships, but the experiment was tried for the first time on an Italian ship of setting them at opposite corners of the central citadel, so that one should command the stern and the other the bows, and that each should be able to fire ahead or astern, or on the broadside, without interfering in any way with the other. The decks before and abaft the citadel were 4 feet 9 inches below the water-level, and were protected by horizontal armour. Extensive experiments were conducted at Spezzia with a 100-ton gun, and guns of 10- and 11-inch calibre, on different types of targets. As first designed these ships were to carry two 60-ton guns in each turret, but when the British Admiralty announced that the _Inflexible_ would have guns of 81 tons, the Italians equipped these two warships with 100-ton guns manufactured at the Elswick works. The armour at the water-line was 22 inches thick on the central portion, and that of the turrets was 18 inches, further strengthened by heavy teak backing. Each ship had a heavy projecting ram, and also had an apparatus for discharging Whitehead torpedoes. Although these ships were described as Italian-built and were certainly put together in Italy, it is interesting to note that the _Duilio_ had trunk engines by Messrs. John Penn and Sons, that practically all the iron and steel put into the vessel’s frames, etc., were made in France, that the armour-plates came from Cammell’s establishment at Sheffield, and that the guns were made at Elswick. Only the heavy forgings for the ship were made in Italy. The _Dandolo_, although described as a sister ship, differed in many particulars from the _Duilio_. The _Dandolo_ had engines of Maudslay’s inverted vertical compound type, a pair of which was given to each of her screw propellers, and she had eight boilers, heated with thirty-four furnaces, and working at a pressure of 60 lb. per square inch. These great ships were out of date soon after being completed, as the discovery of the means of making steel cheaply, and the much greater strength and lightness of the homogeneous metal, as it was called, rendered it possible for ships and guns to be built of much greater power than ever before. Indeed, so great was the progress in these two departments that in a very few years these vessels would no longer have been invulnerable, but would have been relegated, as being slow and unwieldy, to harbour or coast defence work, and thence to the scrap-heap.