(c) _Explosive._ The matter used in a shell to detonate it at the end of its flight. =Cradle.= In general, that part of the carriage which houses the recoil and counter-recoil mechanisms. =Elevating Mechanism.= The device used to elevate the gun through a vertical arc in order to give the gun an elevation corresponding to the desired range at which the piece is to be fired. =Fire Control Equipment.= Those instruments used to compute firing data, observe and correct the fire, such as B. C. Telescopes, Aiming Circles, Range Finders, etc. =Firing Mechanism.= A device located in the breechblock for exploding the primer and thus causing the ignition of the powder charge. =Fuze.= That part of the round which is fastened to the point or to the base of the projectile and causes the latter to be detonated or exploded near the time or the place desired. =Fuze Setter.= A device used to set time fuzes in such a manner that shrapnel or shell will burst at or near the desired height in air. =Gun.= A metallic tube from which projectiles are hurled by gases generated from the ignited powder. In general, all fire arms; but in Field Artillery terms, comparatively long-barreled weapons using relatively high muzzle velocity in contra-distinction to the howitzers and mortars. =Howitzer.= A weapon which differs from a gun in that for the same caliber it uses a shorter tube, lower muzzle velocity and generally a more curved trajectory. From two to seven varying strengths of propelling charges may be used in the howitzer. This gives it selective angles of fall, and allows the howitzer to reach targets that are hidden from the flat trajectories of guns. =Initial Velocity.= The speed with which the projectile first moves. =Limber.= A two-wheeled carriage which is sometimes used to carry an ammunition chest and always used to support the weight of the trail of the piece or caisson. It adds the other two wheels to make a four-wheeled vehicle. =Materiel.= A term used in the Field Artillery in contra-distinction to Personnel. =Mortar.= A weapon using for the same caliber, a barrel much shorter than the corresponding howitzer. Used at short ranges with extreme steep angles of fall to reach highly defiladed targets. =Muzzle.= The front end of the bore. =Muzzle Velocity.= Speed or velocity of the projectile measured as it leaves the muzzle. =Ogive.= The rounded shoulder of the projectile. =Ordnance.= Arms, ammunition, and their accessories. =Piece.= A fire arm, small or large. =Primer.= Device used to insure ignition of the propelling charge. =Projectile.= The effect-producing part of the round. The bullet-like form which is thrown toward the target. =Quadrant, gunners.= A device for measuring angles of elevation.