The center point of the length of each of those blocks carries one side of the gun, which is connected also with the two heavy radius bars seen outside the cheeks, and pivoted close to the segment races on the outside, and with a system of link work between the gun itself and the crosshead of the ram of the hydraulic cylinder, which gives motion to the gun in elevation or depression, through a vertical arc, the imaginary center of which, and of the segments of the side cheeks, is situated in the horizontal diameter across the muzzle of the gun. This is in brief the muzzle-pivoting part of the arrangement, of which, were it worth while to go into its details, we should need some further diagrams to make it quite clear. Nor is it worth while to go into the description of various minor points of refinement about the gun mounting, such as the very exposed long tangent scale seen in the figure, by which the elevation or depression is read off, nor the still more exposed and rather ricketty arrangement by which the rear sight is arranged to rise and fall with the gun, and allowance for dispart avoided. The recoil of the gun is resisted through and by the segment blocks in the side cheeks, and by the heavy radius bars, etc., and thus transferred to the carriage itself. This moves upon four eccentro-concentric rollers, in all respects identical with those brought before the Ordnance Select Committee of Woolwich by Mr. Mallet, in 1858--then rejected, after some time adopted, and brought into use in our own service, where they are now universal, and from which they have been adopted into every artillery in the world, and, we understand, without the slightest recognition of the inventor's rights. On the axle of each of these rollers is keyed a circular eccentric cam plate, those at the same side being connected together by a linking bar so as to move in concert. Adjustable tripping plates attached to the sides of the slide, are so arranged that when the loaded gun has been run forward its carriage base rests hard down, with its full weight upon the top faces of the slide, and thus the recoil is made under the full resistance due to the friction of the entire load. Arrived at the highest point, it rests there until loaded. The cam plates being then given a slight motion of rotation by the help of socket levers--the rectangular projections to be received by which are seen on the top edges of the cam plates in the figure--the carriage, by its own commenced descent, gets again upon its rollers, and runs forward upon these at once into firing position. The two elevated horns which are seen standing up at the rear part of the slide above the roller frame are designed to receive the thump of the two short buffer-blocks--seen at the rear part of each carriage cheek--in the event of the recoil not being wholly expended in raising the weight of gun and carriage, etc., along the curved racers of the slide. These buffer-blocks bear against plugs of vulcanized