ARCTU´RUS, or ALPHA BOÖTIS, a fixed star of the first magnitude in the constellation of Boötes (the Ploughman), is one of the brightest stars in the northern heavens, yellow in colour. Its light is believed to be intrinsically at least 140 times as brilliant as the sun's, and to take over 40 years to reach us. It is notable as having a comparatively large proper motion.
ARDAHAN´, a small fortified town about 6400 feet above the sea, between Kars and Batúm in Armenia. It was captured by the Russians in 1877, and ceded to them by the Berlin Treaty, 1878. It was handed over to Turkey by the Treaty of Brest-Litovsk in 1918, but the Turkish troops evacuated it after the armistice in 1918.
AR´DEA, the genus to which the heron belongs, type of the family Ard[=e]idæ, which includes also cranes, storks, bitterns, &c.
AR´DEBIL, or ARDABIL, a Persian town, province of Azerbaijan, near the Karasu, a tributary of the Aras, about 40 miles from the Caspian, in an elevated and healthy situation; it has mineral springs and a considerable trade. Pop. 16,000.
ARDÈCHE ([.a]r-d[=a]sh), a department in the south of France (Languedoc), on the west side of the Rhone, taking its name from the River Ardèche, which rises within it, and falls into the Rhone after a course of 46 miles; area, 2144 sq. miles. It is generally of a mountainous character, and contains the culminating point of the Cevennes. Silk and wine are produced. Annonay is the principal town, but Privas is the capital. Pop. (1921), 294,308.
ARDEN, FOREST OF, a wood in Warwickshire. Shakespeare is supposed to have used it as a setting for _As You Like It_.
ARDENNES ([.a]r-den´), an extensive tract of hilly land stretching over a large portion of the north-east of France and south-west of Belgium. Anciently the whole tract formed one immense forest (_Arduenna Silva_ of Cæsar); but large portions are now occupied by cultivated fields and populous towns.
ARDENNES ([.a]r-den´), a frontier department in the north-east of France; area, 2027 sq. miles, partly consisting of the Forest of Ardennes. There are extensive slate-quarries, numerous ironworks, and important manufactures of cloth, ironware, leather, glass, earthenware, &c. It was the scene of many battles during the European War (1914-8). Chief towns, Mézières (the capital), Rocroi, and Sedan. Pop. 277,791.