AISNE, a frontier department in the north-east of France, formed in 1790 from portions of the old provinces of Ile-de-France and Picardy. Area 2866 sq. m. Pop. (1906) 534,495. It is bounded N. by the department of Nord and the kingdom of Belgium, E. by the department of Ardennes, S.E. by that of Marne, S. by that of Seine-et-Marne, and W. by those of Oise and Somme. The surface of the department consists of undulating and well-wooded plains, intersected by numerous valleys, and diversified in the north-east by hilly ground which forms a part of the mountain system of the Ardennes. Its general slope is from north-east, where the culminating point (930 ft.) is found, to south-west, though altitudes exceeding 750 ft. are also found in the south. The chief rivers are the Somme, the Escaut and the Sambre, which have their sources in the north of the department; the Oise, traversing the north-west, with its tributaries the Serre and the Aisne, the latter of which joins it beyond the limits of the department; and the Marne and the Ourcq in the south. The climate is in general cold and humid, especially in the north-east. Agriculture is highly developed; cereals, principally wheat and oats, and beetroot are the chief crops; potatoes, flax, hemp, rape and hops are also grown. Pasturage is good, particularly in the north-east, where dairy-farming flourishes. Wine of medium quality is grown on the banks of the Marne and the Aisne. Bee-farming is of some importance. Large tracts of the department are under wood; the chief forests are those of Nouvion and St Michel in the north, Coucy and St Gobain in the centre, and Villers-Cotterets in the south. The osiers grown in the vicinity of St Quentin supply an active basket-making industry.

Though destitute of metals Aisne furnishes abundance of freestone, gypsum and clay. There are numerous tile and brick works in the department. Its most important industrial establishments are the mirror manufactory of St Gobain and the chemical works at Chauny, and the workshops and foundries of Guise, the property of an association of workpeople organized on socialistic lines and producing iron goods of various kinds. The manufacture of sugar is very important; brewing, distilling, flour-milling, iron-founding, the weaving and spinning of cotton, wool and silk, and the manufacture of iron goods, especially agricultural implements, are actively carried on. Aisne imports coal, iron, cotton and other raw material and machinery; it exports cereals, live-stock and agricultural products generally, and manufactured goods. The department is served chiefly by the lines of the Northern railway; in addition, the main line of the Eastern railway to Strassburg traverses the extreme south. The Oise, Aisne and Marne are navigable, and canals furnish 170 m. of waterway. Aisne is divided into five arrondissements—St Quentin and Vervins in the north, Laon in the centre, and Soissons and Château-Thierry in the south—and contains 37 cantons and 841 communes. It forms part of the educational division (académie) of Douai and of the region of the second army corps, its military centre being at Amiens, where also is its court of appeal. Laon is the capital, and Soissons the seat of a bishopric of the province of Reims. Other important places are Château-Thierry, St Quentin and Coucy-le-Château. La Ferté-Milon has remains of an imposing château of the 14th and 15th centuries with interesting fortifications. The ruined church at Longpont (13th century) is the relic of an important Cistercian abbey; Urcel and Mont-Notre-Dame have fine churches, the first entirely in the Romanesque style, the second dating from the 12th and 13th centuries, to which period the church at Braisne also belongs. At Prémontré the buildings of the abbey, which was the cradle of the Premonstratensian order, are occupied by a lunatic asylum.