an arrondissement of the department of Landes, in France. Area 905½ square miles, comprising 8 cantons and 108 communes. Pop. 108,415.

AX, or Ags (Aquae Tarbellicae), an ancient town of France, department of Landes, capital of the above arrondissement, situated in a fertile plain on the left bank of the Adour, 32 miles S.W. of Mont-de-Marsan. It is surrounded by old walls flanked with towers, and has a cathedral, episcopal palace, hall of justice, prison mineralogical museum, agricultural society, &c. It possesses numerous thermal medicinal springs. Manufactures—earthenware, pitch, oil, thread, leather, &c.; and it has some trade in corn, wine, brandy, and wood. Pop. 5238. Before the Roman conquest of Gaul, Dax was the capital of the Tarbelli.