Naval gun carriages and slides, as a rule, are built of plate-iron, although many of the wooden ones are still retained in service for the lighter calibres. The lighter carriages are worked by tackles, and the heavy ones by gearing. Breechings are no longer used with slide carriages, the recoil being checked by friction compressors or hydraulic recoil cylinders and buffers. Wooden carriages are furnished for all smooth-bores and breech-loading rifles, and for 64-pdr. muzzle-loaders. Iron carriages may be furnished for these guns, but wooden ones are never furnished for others. The wooden standing carriage is the old-fashioned four-truck one. The wooden rear-chock carriage is similar to what is known elsewhere as the Marsilly. Breechings are rove through holes in these carriages, and are not attached to the guns. The wooden slide-carriages and their slides are of the ordinary old-fashioned type. The compressor for these carriages consists on each bracket of the carriage of two iron plates with hinged pieces on their lower ends. They are suspended on iron bolts passing through the bracket so that their lower ends hang down and overlap the side of the slide. Through the upper ends of the plates and the bracket an iron screw and lever passes, whose motion separates or approaches the pieces, allowing them to release or grip the slide. Some slide-carriages are provided with hydraulic recoil cylinders. _Iron Field-Carriage._ This carriage consists of two ¼-inch plate-iron brackets recessed to receive the axle-tree. These plates are strengthened by angle-irons riveted along the upper edge on the outer side from the trunnion-holes to the point. The brackets are lightened as much as possible by having pieces cut out of them. A front transom of plate-iron, having angle-irons riveted to it each side to connect it with the brackets; a similar transom about half way down the brackets; an iron trail-plate and axle-tree, and wooden wheels. The carriage makes a load for a mule, and the wheels another load. The elevating-gear consists of an iron stool-bed formed in front to hook loosely over a cross-bar, while the rear end, provided with two small studs, rests in racks riveted to the brackets. This is for getting rapid elevations. For fine sighting a sliding quoin is fitted to the stool-bed by clips, and is worked by a hand-wheel. Check-ropes are applied to the trail-eye and lashed to the wheels in firing. The Gatling gun is provided with a curved ratchet projecting down from the bottom of the gun-case, giving elevations by means of a hand-wheel and pinion. [Illustration: 7-pdr. Field-Carriage.] _Iron Boat-Carriage._ [Illustration: 9-pdr. Boat-Carriage.]