AIR 4 



3. In music, the term air signifies the 

 melody or treble part of a musical com- 

 position ; also the peculiar modulation of 

 the notes which gives music its character. 

 The common meaning is the leading part 

 of a tune, as distinct from the bass, treble, 



and counter. 3. In painting, as the air 



is the medium in nature through which 

 every object is viewed, it is to be trans- 

 ferred to the imitation on the canvas, 

 and the effects which it produces, in re- 

 gulating the sizes and colours of objects, 

 constitute a large part of the artist's 

 knowledge. 



AIRA, the hair-grass, a genus of the 

 class triandria, and order digynia. There 

 are eleven species, seven of which are Bri- 

 tish, and all the order perennials. N amed 

 from eu^ti, to destroy. _ This name was 

 anciently given to the bearded darnel 

 .Lolium temulentum), on account of its in- 

 jurious effects ; and now to this genus of 

 plants, which it was thought somewhat 

 to resemble. 



AIR-BALLOON. See BALLOON. 



AIR-BLADDER, ) the sound or swim of 



AIR-BAO, J fishes: an organ situ- 

 ated in the abdomen, by altering the 

 dimensions of which the fish regulates 

 its depth in the water. 



AIR-CELLS. 1. Of plants : cavities in 

 the stems and leaves intended to render 



the part buoyant in water. 2. Of birds: 



membraneous receptacles which commu- 

 nicate with the lungs. These permeate 

 throughout the whole body. 



AiR-Gu>, a. pneumatic instrument re- 

 sembling a musket, to discharge bullets 

 by the elastic force of the air compressed 

 into an iron or copper globe by means of a 

 condenser. To produce an effect equal to 

 that of gunpowder, 1000 atmospheres must 

 be forced into the globe, that is, the air 

 must be compressed into one thousandth 

 of the bulk which it occupies at .the com- 

 mon pressure of the atmosphere, taken at 

 the earth's surface. 



AIR-HOLDER, an instrument for holding 

 air, for the purpose of counteracting the 

 pressure of a decreasing column of mer- 

 cury. 



AIR-JACKET, a jacket made of leather 

 in which are several receptacles for air, 

 coinmunicating with each other, and 

 fitted to receive air by means of a brass 

 tube. This jacket is used by persons who 

 cannot swim, to support them in the 

 water. A jacket, formed of corks strung 

 together, serves equally well. 



AIR-LAMP, another name for Doberen- 

 nier's lamp. 



AIR-PIPE, a pipe used to withdraw 

 vitiated air from the hold of a vessel, &c. 

 by means of communication with the 

 furnace and the place to be cleared of 

 noxious air. Through this pipe only, the 

 ^re is supplied with air ; and as one end 



} A IS 



is placed in the hold, a perpetual current 

 is thus kept up, the foul air b?ing con- 

 stantly withdrawn from the hold to th 

 fire. 



AIR-POISE, an instrument foi ascertain- 

 ing the weight of a given quantity of air. 



AIR-PLANTS. See AERIAL and AERIDES. 



AIR-PCMP, a pneumatic machine for 

 exhausting the air of a proper vessel, A, 



by means of a pump, B. The figure repre- 

 sents a section of the machine. CD 

 supports the receiver, A, and the pump, 

 B, is fitted air-tight to this sole. There is 

 a communication-tube, t, through which 

 the air passes from A on working the 

 pump, just as water is drawn from a -well 

 by means of a common pump, from which 

 this does not differ. See PUMP. 



AIRS. In the manege, the artificial mo- 

 tions taught horses, as the demivolt, 

 curvet, capriole. 



AIR-SACS, certain receptacles of air in 

 birds, or vesicles lodged in the fleshy parts, 

 in the hollow bones, and in the abdomen : 

 they all communicate with the lungs. 

 These are supposed to be for the purpose 

 of rendering the body specifically lighter, 

 and to supply the place of a muscular 

 diaphragm. 



AIR-SHAI-T, a passage for air into a 

 mine, usually opened in a perpendicular 

 direction, and meeting the adits or hori- 

 zontal passages, to cause a free circulation 

 of fresh air through the mine. It may 

 be made to communicate with a furnace 

 above. 



AIR-THREAD, a name given to the spi- 

 ders' webs which are often seen in autumn 

 floating in long filaments in the air: they 

 are attached to branches of trees and 

 shrubs, and serve to support the spider 

 when in search of prey. 



AIR-TRAP, an opening for the escape of 

 air from drains, or sewers, or pipes. 



AIR-VESSELS, spiral ducts or canals in 

 the leaves and other parts of plants, which 

 are supposed to supply them with air, 

 after the manner of lungs in animals. 



AISLE (pron. He), Fr. aile, from Lat. 

 nla, a wing. When a church is divided 

 in its breadth into three parts, the two 

 extreme outward divisions are called 

 aisles, and the centre division the nate or 

 middle aisfo, although the last seems im- 



