TARN, a river of southern France, tributary to the Garonne, watering the departments of Lozere, Aveyron, Tarn, Haute-Garonne and Tarn-et-Garonne. Length, 234 m. Area of basin, 5733 sq. m. Rising on the southern slope of Mt. Lozere at a height of 5249 ft., the Tarn flows westward and, having received the Tarnon, enters the gorge, famed for its beauty, which separates the Causse de Sauveterre from the Causse Mejan. Emerging from this canon after a course of 37 m. it receives the Jonte on the left and, still flowing through gorges, passes between the Causse Noir, the Larzac plateau and the Causse de St Affrique (at the foot of which it receives the Dourdou de Vabre) on the left and the Levczou range and the Plateau of Segala on the right. In this part of its course the most important town is Millau, where it receives the Dourbie. At the cascade of Sabo, above Albi, the river enters the plains and, flowing in a deep bed, passes Albi and Gaillac, some distance below which, at the confluence of the Agout, it exchanges a west-south-westerly for a north-westerly course. At Montauban the Tarn receives the Tescou and 6 m. farther on unites with the Aveyron. It then reaches Moissac, 2% m. below which it flows into the Garonne.