simple, as in the common perch, sometimes divided into Airer

One who exposes to the air. two or more compartments, by a lateral or trans verso ligature, as in the trout and salmon. In all cases it is com- posed of a thick internal coat of a fibrous texture, and of a very thin external coat; the whole being enveloped in the general covering of the intestines. The modifications of this organ are infinitely varied in different genera and species of fishes. In the greater number of instances, it has no external opening, and the air with which it is found distended, is believed to be certain glandulous organ, with which it is in all these cases provided. In general, all fishes which enjoy great pow- ers of locomotion, and have occasion to pa through varı- ous degrees of superincumbent pre ure in their rapid trans i- tions from the surface to the bottom of the ocean, are pro- vided with this important or- gan; while fishes whose habits and organization confine them either to the surface of the wa- ter or to the bottom of the sea, as skates, soles, turbots, brills. etc., have no air-bladder. It is probable, but not sufficiently proved, that the air- bladder is connected with the respiration of fishes.- See ISINGLASS. Air'-escape', n. A contrivance for riveting off air from water-pipes. Ai'rey, n. See AERIE and EYRY. of compre ed air Air-gun, n. An instrument for projecting bullets, in which the moving power is the rush of condensed air allowed to escape, instead of the formation of gases arising from the ignition of gunpowder. In the stock of the air-gun is a condensing syringe, the piston of which condenses air into a cavity having a valve opening inward, just behind the bullet. The barrel is open, and the bullet (which should just fit the barrel) is inserted in the usual way. The trigger opens the valve behind the bullet, and permits the rush of the condensed air, which propels the bullet forward. The moment the finger is withdrawn from the trigger, the air closes the valve, and remains, somewhat le condensed than be- fore, for the next discharge. No power, but only a con- venient adaptation of power, is gained in an air-gun, since the condensation of the air itself requires an ex- penditure of power. The instrument has hitherto been little more than a toy.-Invented by Marin, a French- man, who presented one to Henry IV. Air-hold'er, n. An instrument for holding air; a gasometer. Air'-hole, n. A hole to admit or discharge air. Fig. 60. -AIR-BLADDER. Air'ily, adv. In an airy manner; gayly. ( Corvina trispinosa .) at the top of a high mountain than one of the same size and weight at its bottom. From this it follows, that human beings must breathe slower in valleys and quicker at greater altitudes. The air is being continually rendared impure by the breathing of animals, the oxygen it contains being transformed into carbonic acid. This, however, lasts but a short time, being quickly separated into carbon and oxygen by plants, which retain the former body for their own nourishment, releasing the latter to serve again as support for animal life. This art. refers only to the chemical and mechanical properties of air. The constitution of the whole ma is to be found under the name ATMOSPHERE. - See also, ACOUSTICS, BALLOON, COMBUSTION, OXYGEN, RESPIRATION, . ( Mus .) A piece of music, composed of a certain number of melodious phrases, united in a regular symmetrical form, and terminating in the key in which it began. A melody. - As employed in music, the origin of the word air is unknown. Air is the most important of the constituents of music. A composition may be replete with learned and ingenious harmony, may abound in fugue, in imitation, and all the contrivances of science, but without good melody, will never appeal to the heart, and seldom afford any gratification to the ear. In music composed for the theatre, and which is constantly introduced into the concert-room, are the following varieties of air, designated by Italian denominations, viz.: Aria di bravura (literally, air of courage , or a dashing air ), in which the performer displays his powers of execution, and seeks rather to astonish than please. Aria di cantabile ( singing air), a tender, pathetic air, calling forth the expre ion and taste of the singer. Aria di carattere (characteristic air), which is distinguished by force and energy of expre ion, and by dramatic effect. Aria parlante ( speaking air ), which is rather declaimed than sung, and is best suited to the buffo , or comic performer. -An air var ié [Fr.] is literally an air with variations, but this name is often given by a composer, arranger, or performer to a melody fancifully variegated and embellished. (Print.) The medium, as transferred to a picture, through which natural objects are viewed. Air, in Alabama, a post-village of Clark co., 118 miles S. of Tuscaloosa. Air, in Mi ouri, a post-office of Johnson co. Air, in Pennsylvania, a village of Bedford co., on Big Cove creek. - Also , a township of Fulton county, more usually written AYR, q. v. See BALLOON.