The recoil indicator is located just back of the trunnion bracket on the right side of the cradle and consists of a steel spring which is adjusted by means of a nut so that the pointer bears against a scale engraved on the edge of the sleigh indicating the length of recoil. The front end of the cradle is covered by the cradle head and provided with an opening through which the pressure-gauge adapter may be assembled to the gauge-cock body. The lower half of the front end of the cradle is closed by the front transom, forming a guide for the piston-rod lock which is operated by means of a lever. When this lever is lowered the lock plate moves to the right, releasing the piston-rod nuts. When the lever is raised the lock moves to the left, locking the nuts in firing position. The locking device is protected by the cradle front cover which holds the lever in firing position when closed. The filling valve is accessible through the cradle bottom cover located on the bottom of the cradle to the rear of the front transom. The pump bracket is located on the left side of the cradle near the front. [Illustration: 155 MM HOWITZER, MODEL OF 1918 (SCHNEIDER) LEFT SIDE ELEVATION, IN BATTERY] [Illustration: 155 MM HOWITZER, MODEL OF 1918 (SCHNEIDER) ELEVATING MECHANISM] =Recoil and Counter-Recoil Mechanisms.= When the howitzer is fired the recoil mechanism exercises its retarding influence by means of a liquid which is obliged to pass through an orifice whose size diminishes as the movement proceeds, thus checking the recoiling mass. The recoiling movement of the gun actuates at the same time the counter-recoil mechanism, which acts on the counter-recoil liquid and forces it into two reservoirs, thus further compressing a gas therein contained. When the recoil movement is ended the expansion of gas forces the counter-recoil mechanism back “into battery,” and the recoil cylinder again exercises its retarding influence to prevent a too rapid return and shock. The normal recoil is 51.375 inches (1.305 meters). When the piece is fired the howitzer and sleigh move to the rear, the recoil and counter-recoil rods, which are held by the piston-rod lock remaining stationary. The liquid in the counter-recoil cylinder is thus forced into the air cylinders, building up a pressure sufficient to return the howitzer to battery. The liquid in the recoil cylinder is forced through the orifices in the recoil piston rod and then through the throttling ring. The tapered buffer rod, which is attached to the recoil cylinder head, moves through the throttling ring, gradually closing the orifice, thus keeping the pressure constant as the velocity of recoil is reduced. As the buffer rod moves to the rear the counter-recoil valve is opened, allowing the liquid to pass freely into the buffer chamber. As the gun returns to battery the buffer valve closes, forcing the liquid to pass through the small clearance around the valve, thus absorbing the energy of counter recoil.