The recoil arrangement of this carriage is made up of two plates operated by a lever, and jamming between them a flat plate attached to the carriage. The carriage is run in and out by gearing, the driving-wheel engaging in racks inside the slide-rails. The training-gear is of the ordinary type, but gears directly into the slide-rollers, whose middle sections are cogged, the middle section of the circle or races being cut in a rack. [8] See page 299. [Illustration] [Illustration: Geared Carriage and Slide with Hydraulic Recoil.] _Ericsson’s Turret-Carriage._ The slide of the turret-carriage consists of two bars built into the turret. The carriage is made of double plate-iron worked on a frame. The compressor is the original of the Elswick compressor (see page 201), working on the same principle. The gun is run in and out by means of a large cogged driving-wheel gearing in a rack underneath the slide. [Illustration: Ericsson’s Turret-Carriage. (Top.)] [Illustration: Ericsson’s Turret-Carriage. (Bottom.)] _Friction-Drum Recoil-Check Carriage._ The carriage and slide are similar to those of the 11-inch iron pivot-carriage, except with regard to the recoil check, which is exactly the same in principle as that of the directing-bar carriage. [Illustration: Ericsson’s Friction Recoil Carriage.] GUNPOWDER. [Illustration: Cubical Powder.] [Illustration: Hexagonal Powder.] Gunpowder is classed in accordance with its size of grain as follows: Hexagonal | | not less than 70 nor more than 75 grains to the pound. Cubical | Mammoth ” ” 0.5 ” ” 1 inch measurement. Rifle ” ” 0.3 ” ” 0.5 ” ” Cannon ” ” 0.1 ” ” 0.3 ” ” Torpedo ” ” 0.1 ” ” .15 ” ” Small-arm ” ” 0.05 ” ” .06 ” ” Shell ” ” .02 ” ” .06 ” ” PROJECTILES. The projectiles used with both smooth-bores and rifles are shot, shell, shrapnel, and case-shot. All smooth-bore projectiles are of cast-iron. All rifle projectiles except the 8-inch shot are common cast-iron; the shot are chilled-headed. [Illustration: 100-pdr. Parrott-Shell.] [Illustration: 8-inch Shell.] [Illustration: 8-inch Shot.] [Illustration: 8-inch B. L. Shell.] Rifled projectiles for the boat-guns (B. L.) are provided with rotating grooved belts cast on them. They also have a rear centring ring. The rotating-rings for the larger calibres are brass rings screwing on the base of the projectile, and having an expansion groove or cup on the rear end. In the Parrott projectiles the ring is cast on the base around a heavy dovetailed score, having jogs to prevent the ring turning on the base of the shell.