312 GUNNERY avers- considered typical of all sliding carriages on traversing plat- 5 forms. The direction of the gun is changed as required by ^ es- training the platform to the right or left, the trucks working on the racers, front and rear, which are usually of wrought iron, laid concentrically on a bed of stone. The level of the traversing platform rises towards the rear, so as to assist in absorbing the work of recoil on firing, and to facilitate running forward again after loading. The recoil is also checked either by a system of friction plates, called a com pressor, or by an hydraulic buffer, placed parallel to and between the sides of the traversing platform, so that the carriage on recoil forces a piston into a cylinder containing oil, which escapes, through holes cut through the piston held, into the space round the piston rod ; the size of the holes and the amount of the oil regulate the resistance offered to recoil, and enable the gunner to stop the piece at the proper place. ap- Several kinds of c images on the "disappearing" iring principle have from time to time been put forward. In these the gun is exposed to the fire of the enemy only whils being aimed and discharged; loading is performed under cover. The Moncrieff carnages are the most success ful of this class. In them the force of recoil is stored up and employed to raise the gun from the loading to the firing position. Colonel Moncrieff applies his principle in two vrays : the recoil either raises a counter-weight or forces a piston into a cylinder, compressing, by the aid of a fluid, air already much compressed. The counter-weight carri ages are used to some extent in coast defence, and the hydro-pneumatic carriages are under trial for siege-train guns. Plate V. gives the details of the former. On a level traversing platform rolls a carriage or " elevator," n- which places the gun in the required position either for
- ff s loading or firing. The end of the elevator opposite to that
em< which carries the gun is weighted, so that the recoil causes the elevator to roll to the rear and the gun to descend, at the same time raising the weight, which is retained in the upward position till released after loading, when its descent again raises the gun. Thus the elevator is a lever of the first order working on a shifting fulcrum, the curve (an involute) of the rolling surface being so adjusted that the resistance of the weight gradually increases as the gun recoils, and finally stops it smoothly and without violence. Conversely, by this form the gun is raised to the firing position gradually and without being jolted. Hydraulic Gear for Guns. As soon as the weights of ordnance increased so greatly that their service exceeded the power of manual labour, it became necessary to find some substitute. Steam power is always at hand in steam vessels, and it was quickly seen that it was best applied through the medium of water pressure. The simplicity and compactness of hydraulic machinery, the circumstance of its direct action rendering toothed gear unnecessary, and the perfect control it gives over the motion of heavy weights, especially adapt it for the purpose. ndel s Plate VI. represents the mode in which the system is applied to the working of the 80-ton guns on board H.M.S. " Inflexible." A mlic circular turret contains two guns placed side by side, and strictly items, parallel as to line. The hydraulic pressure is conveyed through the trunk A by pipes to the presses in the turret. At B is a press for elevating the gun; this press also absorbs the force vertically given off during recoil on the elevating beam C. D is the gun-slide which carries the recoil press G for checking the recoil. This press is sup plied with a tank T, up into which the water from the press G must escape through valves V loaded to the required pressure by springs. E is the gun run forward in the firing position ; its trunnion S is fixed to the end of a piston rod, the head of which enters the press G ; when the gun E is fired it recoils into the position F, shown by the dotted outline. The trunnion S forces the piston home into the cylinder G, driving the water up into the tank ; the trunnion fit tings run along the gun-slide horizontally, and the attachment or saddle below the gun runs up the elevating beam C, which is pivoted at the fixed point T, so as to depress the muzzle outside the port P of the turret PR. The gun is then in the loading posi tion. In the meanwhile the turret has been caused to revolve on the conical rollers H, H by hydraulic pressure till the muzzle of the gun is brought opposite the loading apparatus, which is securely housed beloiv deck. The water power is taken down the am munition hoist K, which raises a truck L, carrying a shell, on the top of which is laid a cartridge, to the loading position M. The sponge N, similarly worked by hydraulic pressure, serves as a rammer also. To perform the operation of loading, the sponge is forced home through the bore of the gun against the bottom, by con tact with which a button on the head is pressed, setting free a rush of water ; this thoroughly and visibly drenches the bore, and pre vents the remotest possibility of a burning fragment remaining from the previous round ; the sponge is then withdrawn, and the am munition raised to M ; the sponge now becomes a rammer, thrusts the cartridge into the muzzle of the gun, and is drawn back ; the truck is raised still higher, the rammer then pushes the projectile into the muzzle, and rams home both cartridge and shell together ; a wad previously placed on the head of the rammer is left behind, fast in the bore in front of the projectile, which is thus prevented from moving forward. An indicator on the rammer shows whether the charge is home. The press B is then put in action to lower the breech, raising the muzzle to the elevation required to suit the range of the object to be fired at ; the gun is run forward to the firing position E, and the turret is revolved till the guns point at the object. The sighting is not on the guns, but on the turret ; the captain of the battery looks through a hole in the roof K, behind the guns, and arrests the movement of the turret at the correct place, when the line between the sights, which is parallel to the axes of the guns, is directed to the object. The firing may be performed either in the usual way, or by electric tubes and wires from a distance. Plate V., fig. 2, shows a 100-ton rifled muzzle-loading gun, mounted en barbette for coast defence, and adjusted for hydraulic loading. After being fired the gun is traversed round to the posi tion A, where its muzzle is brought opposite the loading apparatus G, which is contained in a recess in the parapet D. An hydraulic hoist E raises the ammunition on a truck F to the muzzle ; a similar apparatus is constructed on the right of the gun, which is traversed to either at pleasure. The carriage B slides on the platform C, which pivots on P, a trunk through which is introduced the hydraulic power for running the gun back and absorbing the recoil. Many other applications of hydraulic power to gunnery besides those just described are due to Mr G. Rendel of the great Elswick firm. One of the most novel is that adopted in H.M.S. " Temeraire," in which 25-ton guns are mounted on the disappearing principle in a turret having no roof and no ports ; inside the turret is a turn-table carrying the gun by the trunnions on two arms, which are raised by hydraulic power, enabling the gun to fire en barbette over the wall of the turret. The recoil brings it down again, and it is placed opposite the loading gear by revolving the turn-table. The general principles are the same as those on which the .previously described systems are constructed. Loading. This article would be scarcely complete with- Muzzle- out a reference to the comparative advantages of the muzzle loa( ling and breech-loading systems. Many have been much im- rm * pressed with the great superiority of breech-loaders as small i oa( ii n ,r. arms, whether for sporting or military purposes, and have concluded that the same superiority must extend to ord nance constructed on this plan. Others, having seen the difficulty of avoiding complication and accident to the parts in the early breech-loaders, have hastily condemned the whole system. The truth, as is often the case, lies between the two views, as will be seen from the following considera- tions. The chief points of excellence to be attained by a field gun are () high ratio of power to weight ; (6) im munity from injury by its own fire ; (<) immunity from injury by the enemy s fire ; (d) capability of supporting the accidents of service ; (e) rapidity and facility of manipula tion ; (/) efficiency of projectile. (<r.) The power of a gun is most conveniently measured by the energy (in foot tons) communicated to the projectile on leaving the muzzle. The following table shows how the latest English and German field guns compare together in this respect. The English guns are muzzle-loaders, the German ones breech
loaders.