A very few words of description, aided by the very clear engraving annexed, will suffice to make the arrangement plain to every mechanical reader. The entire structure is metallic, chiefly of cast iron or of steel. Upon the platform of the casemate, or deck of the ship, or turret, is laid the heavy bed or traverse plate, cast hollow in iron, holding the vertical pivot at its forward end, on which the gun slide traverses in azimuth, and at its rear end the segment plate, bolted down and separately adjustable as to position upon the bedplate. The slide is also a ponderous hollow casting, the upper surfaces of which, on which the gun carriage runs forward or recoils, are curvilinear in a vertical plane, so that the inclination to the horizon is greatest at the rear end. At the rear end of the slide it traverses upon two heavy cast-iron turned conical rollers, which are geared together and actuated by the winch handle and spur gear, seen in our engraving; by these the slide is practically held fast in any position on the bedplate. The gun itself--in the model, a steel breech-loader, on the Prussian regulation system, very slightly modified--is sustained between two high and ponderous cheek plates of cast iron, which constitute the sides of the carriage, and which are connected together strongly at the lower edges by a heavy base or bottom plate, and at the top by two light cross distance bolts. The muzzle and breech extremities of the piece project well beyond those cheeks. Along the bottom of the trough of the carriage, directly under the gun, lies a nearly horizontal hydraulic press cylinder, the pump and handle actuating which are seen in the figures to the proper left of the gun, and the supply of water for which is contained in the hollow bottom of the carriage. On each side cheek of the carriage is formed, by curved planing, a circular segmental race, opening inward or toward each other, rectangular in cross section and into each of which is fitted a segmental block just filling it up, and occupying a portion of its length so as to slide easily up or downward through the whole range of the arc or segment.