The fixtures for the slide and carriage differ in several particulars from the heavier ones. The slide travels on four _pairs_ of rollers, the rear rollers of the rear pairs being cogged for fine pointing as in the heavier ones. The slide rests on iron pillars with screw-threads at the upper extremities, the lower ones resting on the axles between the rollers, forming a pair. The threaded top has a capstan-head, so that, by turning, the front or rear of the slide may be elevated or depressed. These rollers are also arranged for transporting the slide from port to port. For this they may be turned to run in the desired direction, similar to the principle of chair-rollers (casters). Clamps are provided to hold them in the desired position. The carriage has only one in-tackle. The rocking-lever compressor is changed to the ordinary bow-compressor. (See English Ordnance, Compressor for wooden-slide carriages.) _Turret-Carriage and Slide for Heavy Guns._[7] [Illustration: Additional Gearing for Elevating-Gear of Turret-Carriage.] The turret-slide, instead of being provided with rollers for traversing, is mounted on a centre-pivoting turn-table. The turret itself is fixed, the gun firing over it “en barbette.” The turn-table is mounted on sixteen conical rollers, and is revolved by means of a fixed rack, to which gears a pinion worked by a crank attachment on the slide. This attachment consists of a horizontal axle revolving in bearings through the rear of the slide-plates, having a crank at each end and a chain-wheel in the middle. An endless chain transmits the motion to gearing at the forward end of the slide, which connects with the rack on the floor of the turret. A locking arrangement holds the turn-table in the desired direction. The slide resting on its supports rises to a much greater height than with broadside-carriages, and is provided with a short stairway from the turn-table to the slide-top. The carriage is similar to the ones heretofore described, except that extra gearing is applied to the elevating apparatus to enable it to be reached by the men standing on the turn-table. Chain-gear similar to Scott’s in and out gear is used with the carriage. Instead of a movable stirrup used to catch the chain, the upper part passes through a slit in the rear transom of the carriage, so that when the rear trucks are thrown in action teeth in it catch the chain. The same style of compressor is used as is found with the 24-cm. carriage previously described, except for the 19 cm. gun, which has the ordinary cramp-compressor. [7] See plate Part IV. French Barbette Turret. [Illustration: Barbette Turret-Carriage.] _Revolving-Slide Carriage._