AIR-GUN, a weapon like a common gun in shape, in which the force employed to propel the bullet is the elas-ticity of condensed atmospheric air. It has attached to it, or constructed in it, a strong metal chamber, into which air is forced by a condensing syringe (see PNEUMATICS). In this way a pressure may be obtained of several hundred atmospheres. When a trigger is touched, the condensed air rushes into a space behind the bullet with such force as to propel it from the barrel to a considerable distance. If only a little air be allowed to escape each time, a single charge will propel a number of bullets in succession, with a constantly diminishing force. Sometimes the weapon is made in the form of a walking-stick, and is then called an air-cane. The air-gun is little else than a scientific toy, and has no practical value. The apparatus is costly, the process of condensation requires considerable labour, and the propulsive force of the air is, at its maximum, less than that of an ordinary charge of gunpowder. The only advantage it can be said to have in any way is the ques-tionable one of its use being unattended by the explosive noise that accompanies the discharge of a common gun.