CASTRES, an arrondissement of the department of Tarn, in France, extending over 775 square miles. It is divided into fourteen cantons and 106 communes, and contains 115,252 inhabitants. The capital, a city of the same name, is situated on the navigable river Agout. It contains 1681 houses, and 13,717 inhabitants, who are employed in woollen manufactures, tanneries, paper-mills, and other industrious pursuits. Long. 2. 9. 50. E. Lat. 43. 37. 10. N.