AIN, a department on the eastern frontier of France, formed in 1790 from Bresse, the Pays de Gex, Bugey, Dombes and Valromey, districts of Burgundy. It is bounded N. by the departments of Jura and Saône-et-Loire, W. by Saône-et-Loire and Rhône, S. by Isère, and E. by the departments of Savoie and Haute-Savoie and the Swiss cantons Geneva and Vaud. Pop. (1906) 345,856. Area 2248 sq. m. The department takes its name from the river Ain, which traverses its centre in a southerly direction and separates it roughly into two well-marked physical divisions—a region of mountains to the east. and of plains to the west. The mountainous region is occupied by the southern portion of the Jura, which is divided into parallel chains running north and south and decreasing in height from east to west. The most easterly of these chains, that forming the Pays de Gex in the extreme north-east of the department, contains the Cret de la Neige (6653 ft.) and other of the highest summits in the whole range. The district of Bugey occupies the triangle formed by the Rhone in the south-east of the department. West of the Ain, with the exception of the district covered by the Revermont, the westernmost chain of the Jura, the country is flat, consisting in the north of the south portion of the Bresse, in the south of the marshy Dombes. The chief rivers of the eastern region are the Valserine and the Seran, right-hand tributaries of the Rhone, which forms the eastern and southern boundary of the department; and the Albarine and Oignin, left-hand affluents of the Ain. The Bresse is watered by the Veyle and the Reyssouze, both flowing into the Saône, which washes the western limit of the department. The climate is cold in the eastern and central districts of Ain, but it is on the whole healthy, except in the Dombes. The average rainfall is about 38 in. The soil in the valleys and plains of the department, especially in the Bresse, is fertile, producing large quantities of wheat, as well as oats, buckwheat and maize. East of the Ain, forests of fir and oak abound on the mountains, the lower slopes of which give excellent pasture for sheep and cattle, and much cheese is produced. Horse-raising is carried on in the Dombes. The pigs and fowls of the Bresse and the geese and turkeys of the Dombes are largely exported. The vineyards of Bugey and Revermont yield good wines. The chief mineral product is the asphalt of the mines of Seyssel on the eastern frontier, besides which potter’s clay, building stone, hydraulic lime and cement are produced in the department. There are many corn and saw mills and the wood-working industry is important. Silk fabrics, coarse woollen cloth, paper and clocks are manufactured. Live-stock and agricultural products are exported; the chief imports are wood and raw silk. The department is within the judicial circumscription of the appeal court of Lyons and the educational circumscription (académie) of Lyons. It forms part of the archiepiscopal province of Besancon. The Rhone and the Saone are navigable for considerable distances in the department; the chief railway is that of the Paris-Lyon-Méditerranée Company, whose line from Mâcon to Culoz traverses the department. Ain is divided into five arrondissements—those of Bourg and Trevoux in the west, and those of Gex, Nantua and Belley in the east; containing in all 36 cantons and 455 communes. Bourg is the capital and Belley is the seat of a bishop. Jujurieux, in the arrondissement of Nantua, has the most important silk factory in the department, occupying over 1000 workpeople. Bellegarde on the eastern frontier is an industrial centre; it has a manufactory of wood-pulp, and saw and flour mills, power for which is obtained from the waters of the Rhone, Oyonnax and its environs, north of Nantua, are noted for the production of articles in wood and horn, especially combs. St Rambert, in the arrondissement of Belley, besides being of industrial importance for its manufactures of silk and paper, possesses the remains of a Benedictine abbey, powerful in the 11th, 12th and 13th centuries. The Gothic church of Ambronay in the arrondissement of Belley, the church of St Paul de Varax (about 9 m. S.W. of Bourg), a building in the Romanesque style of Burgundy, and that of Nantua (12th century), are of architectural interest. Ferney, 4 m. S.W. of Gex, is famous as the residence of Voltaire from 1758–1778.