a thin transparent fluid which encompasses the globe of the earth to a considerable height. For the weight, pressure, elasticity, &c., of air, see PNEUMATICS.

Air, in medicine, one of the six non-naturals, and as essential to the life of animals as food, or any of the ordinary evacuations.

Air, in mythology, was adored by the heathens under the names of Jupiter and Juno; the former representing the superior and finer part of the atmosphere, and the latter the inferior and grosser part. The augurs also drew prefiges from the clouds, thunder, lightning, &c.

Air, in painting, &c., denotes the manner and very life of action; or it is that which expresses the disposition of the agent.

It is sometimes also used in a somewhat synonymous sense with gesture or attitude.

Air, in music, denotes the melody proper for songs, odes, and the like; being usually quick and lively.

Sometimes it is used for the songs themselves, called by the Romans aera, from which the modern term air is derived.

AIRS, in the menage, are the artificial motions of taught horses, as the demivolte, curvet, capriole, &c. See DEMIVOLT, &c.

Air-bladder, a vesicle in the bodies of most fishes, by which, being filled with air, they are enabled to sink or raise themselves in the water, by compressing or expanding the air contained in this bag, and thereby rendering their bodies at pleasure specifically heavier or lighter than water.

Air-gun, a machine for exploding balls by means of condensed air. See PNEUMATICS.

Air pump, a machine by which the air contained in a proper vessel may be exhausted, or drawn out. See PNEUMATICS.

Air-shafts, among miners, are holes made to meet the adits, and supply them with fresh air. These, when the adits are long, or exceeding thirty or forty fathom, become highly necessary, as well to give vent to the damps and noxious vapours, as to let in fresh air.

Air-threads. See GOSSAMER.

Air-vessels, are spiral ducts in the leaves, &c., of plants, supposed to be analogous to the lungs of animals, in supplying the different parts of a plant with air.