AJOVEA, in botany, a genus of the Hexandria Monogynia class and order: the calyx is single-leaved, the corolla has three petals, the stigma is divided into six segments, and the fruit is a roundish, single -celle d, monospermous berry. There is one species that grows in the foreits of Guiana.
AIR, a thin elastic fluid, surrounding the globe of the earth. it is compounded principally of two gasses, viz. oxygen and azote, together with a variety of other substances, suspended or dissolved there in. The mechanical and chemical effects of this extensive fluid mass are discussed under various heads of science. See AT 7402iPHLIIE, C/IENISTRY, and the articles thence referred to.
Ala, in music, generally speaking, is any melody, the passages of which are so constructed as to lie within the province of vocal expression, or which, when sung or played, forms that connected chain of sounds which we call tune. The strict import of the word is confined to vocal music, and signifies a composition writ ten for a single voice, and applied to words.
a machine for exploding balls by means of condensed air.
Authors describe two kinds of this ma chine, viz. the common one, and what is called the magazine air-gun. See Pistu DIATICS.
Ain pipes, a contrivance invented by Mr. Sutton, a brewer of London, for clear ing the holds of ships, and other close places of their foul air. The principle upon which this contrivance is founded is well known. It is no other than the rare fying power of heat, which, by causing a diminution of the density of the air in one place, allows that which is i n contact with it to rush in, and to be succeeded by a constant supply from remoter parts, till the air becomes everywhere equally elas tic. If ft tube, then, be laid in the well hold, or any other part of a ship, and the upperpart ofthistube be sufficiently heat ed to rarefy the impending column of air, the equilibrium will be maintained by the putrid air from the bottom of the tube, which, being thus drawn out, will be sue eeeded by a supply of fresh air from the other parts oldie ship ; and by continuing the operation, the air will be changed in all parts of theship. Upon this principle, Mr. Sutton proposed to purify the bad air of a ship by means of the fire used for the coppers, or boiling places, with which every ship is provided. Under every such copper or boiler there are two holes, se parated by a grate, one for the fire and the other for the ashes ; and there is also a flue, communicating with the fire place, for the discharge of the smoke. The fire,
after it is lighted, is preserved by the con stant draught of air through these two holes and the flue ; and if the two holes are dosed, the fire is extinguished. But when these arc closed, if another hole, communicating with any other airy place, ' and also with the fire, be opened, the fire will of course continue to burn. In order to clear the holds of the ships of the bad air, Mr. Sutton proposed to close the two holes above mentioned, viz. the fire-place and ash-place, with substantial iron doors, and to lay a copper or leaden pipe, of suf ficient size, from the hold into the ash place, and thus to supply a draught of air for feeding the fire ; a constant discharge of air from the hold will be thus obtained, and fresh air will be supplied down the hatches, and by such other communica tions as are open into the hold. If other pipes are connected with this principal pipe, communicating either with the wells or lower decks, the air that serves to feed the fire will be drawn from such places.
Am n-shafts, among miners, arc holes made from the open air to meet the adits, and supply them with fresh air.
These, when the adits are long, or ex ceeding thirty or forty fathoms, become highly necessary, as well to give vent to the damps and noxious vapours, as to let in fresh air.
Ant-trunk, a simple contrivance by Dr. Hales, for preventing the stagnation of putrid effluvia, and purifying the air in Jails and close rooms ; which consists of a square trunk, open at both ends, one of which is fixed in the ceiling, and the other is extended to a considerable height above the roof. The noxious effluvia, as cending to the top of the room, escape by this trunk. Some of these have been nine, and others six, inches in the clear ; but, whatever be their diameter, their length should be proportional, in order to promote the ascent of the vapour. As the pressure of fluids, and consequently of the air, corresponds to their perpendi cular altitude, the longer these trunks are, so much the greater will be the dif ference between columns of air pressing at the bottom and at the top ; and of course so much the greater will be their effect. See VENTILATOR.