The lock-heads serve as breech-plugs, and receive the recoil when the cartridges are fired. Each lock carries a _hooked extractor_ which rides over and catches the flange of the cartridge, when the lock is forced forward, and when the lock retreats withdraws the empty shell until it comes within reach of the ejector, by which it is positively thrown out. The ejectors, _ff_, hinged to the case, are driven by projections on the sides of the locks which give them positive movements to eject the empty shells. The =Feed=, resembling the Bruce feed but without the wheel, is fixed to the casing in rear of the barrels. Below the feed-guide the casing has two holes for the passage of cartridges, and below the holes is the feed-valve, which slides at right angles to the barrels when driven by the forked-shaped lever which receives its motion from the bolts as they move forward. OBSERVATIONS. 1. If the crank be turned before the feeding of the cartridges is commenced, the first few will fall irregularly and check the working of the gun. 2. Be careful to reclamp firmly the swivel and pointing-lever after pointing. 3. To oscillate the gun without changing the elevation, unclamp the swivel and turn the gun back and forth from right to left by means of the pointing-lever, regulating the amplitude of the vibration by the oscillation-stop head. 4. When the firing is discontinued, turn the safety-crank downwards and to the front, until the crank-stop drops into its front recess in the casing. 5. This gun may be fired by turning the crank backward. NOMENCLATURE OF THE GUN. =In and about the Casing.=--Lock (lock-frame; lock-frame heads; lock-frame truck; locking-lever; locking-lever pins; locking-lever stop-pins; firing-pin; firing-pin rack; mainspring; sear; sear-pin; sear-spring; sear-spring pin; extractor); casing (body); casing (cover); cascable; cascable-screw; rear sight and pinion; rear-sight guide; lock-cam; lock-cam recoil-plates; lock-cam journal-boxes; perforated plate; perforated plate cartridge-support; shell-starter; cocking-cam; cocking-cam screws; hand-crank; hand-crank pin; hand-crank handle; ejector; ejector-pins; lock-guide; cartridge-guide; feed-valve; feed-valve slide; feed-valve seat; feed-valve lever; feed-valve lever-screw; feed-valve lever-slide; feed-guide; feed-guide catch; feed-guide cartridge-stop; front sight; mainspring-compressor; lever and compressor locks; compressor-guide; safety-crank; safety-crank stop; safety-crank stop-spring; safety-crank shaft, safety-crank shaft-lever and pins; front-sight spring; barrels; front barrel-plate; front barrel-plate pin; rear barrel-plate; rear barrel-plate pin.