AINTAB, A town in the Syrian vilayet of Aleppo, Asiatic Turkey, situated about 65 miles north of the city of Aleppo (Map: Tur key in Asia, G 4). It is an important military post and is well fortified. It carries on an ex tensive trade in leather and cotton, and lies on the route leading from Aleppo to Armenia. its population is about 43,000, and consists, to a great extent, of Armenian and Greek Christians.
AIR, or A hilly region in the southern part of Sahara, situated between 17° and 20° northern latitude and 7° and 10°eastern longitude. It is regarded as one of the best pop ulated centres of Sahara, but has been very little explored as The valleys are supposed to be fertile and the climate temperate. There are no permanent rivers, but the numerous ravines fill with water during the rainy season, and it often happens that a large valley is converted into a river in a very short time. The country
is ruled by a native Sultan, and the population, estimated at about 100,000, consists chiefly of Tuaregs. Capital, Agades (q.v.).
AIR (Lat. aer, Gk. 4p, a-er, from den', (win, to blow). The mixture of gases forming the at mosphere of the earth. It consists essentially of 79.03 parts of nitrogen and 20.97 parts of oxygen, with varying small quantities of carbonic acid, ammonia. ozone, argon, helium. neon, krypton, and xenon (qq.v.), aqueous. vapor. Certain chemical compounds, as common salt, ammonium nitrate, etc.. as well as minute particles of ani mal, vegetable, and mineral matter, are also fre qnently found in the air. Early chemists called all gases airs. The chief properties of air and the phenomena they give rise to may be found treated under ATMOSPHERE; AERODYNAMICs; AEROSTATICS; BAROMETER; AERONAUTICS, etc.