[AIR- 7.]
1. Any chamber or cavity filled with air in an animal or plant, esp. those in a chambered-shell.
1847. Ansted, Anc. World, iii. 43. In the Nautilus we find a large, powerful, and complicated shell, composed of a number of separate compartments or air-chambers.
1855. Owen, Vertebr., I. ii. (L.). These air-chambers between the outer table and the immediate covering of the brain.
2. In a pump or other hydraulic machine, a receptacle containing air, the elasticity of which, when condensed, maintains a constant pressure upon the water; an air-vessel.
1873. Atkinson, trans. Ganots Physics, § 206. The fire engine is a force pump in which a steady jet is obtained by the aid of an air-chamber.