POTOSI, a department of Bolivia occupying the south-western angle of that republic, bounded N. by Oruro, Cochabamba and Chuquisaca, E. by the two last departments and Tarija, S. by Argentina and W. by Chile and Oruro. Pop. (1932 estimate), 567,291 the larger part Indians; area 45,031 sq.m. The eastern part of the department is traversed north to south by the eastern branch of the Andes, locally known as the Cordillera de los Frailes and the Sierras de Chichas. Spurs and broken ranges project eastward from these, between which are the headstreams of the Pilcomayo and Guapay, the first flowing south-east to the La Plata, and the second north-east to the Madeira and Amazon. The Pilcomayo itself rises in the department of Oruro, but several of its larger tributaries belong to Potosi—the San Juan, Cota gaita and Tumusla in the south, and Cachimayo in the north. The western part of the department belongs to the great Bolivian altiplanicie, or southern extension of the Titicaca basin. It is a barren, saline waste, almost uninhabitable. In the north, bor dering on the transverse ridge of which the Cerro de Tahua (17,457 ft.) forms a part, is the depression known as the Pampa de Empeza, 12,080 ft. above sea-level. Near the southern frontier is another transverse ridge, in part formed by the Sierra de Lipez, and in part by apparently detached groups of high peaks; it is a waterless desert like the Puna de Atacama.
Potosi is essentially a mining department, though agriculture and grazing occupy some attention in the eastern valleys. The plateau there is rich in minerals, especially silver and copper. The Huanchaca-Pulacayo group of mines, situated on the slopes of the eastern Cordillera, about 13,600 ft. above sea-level, over looking the Pampa de Empeza, has the largest output of silver in Bolivia, and ranks next to the Broken Hill mine of Australia in production. Between 1873 and 1901 it yielded 4,520 tons of
silver, of an estimated value of £23,200,000. Farther south are the Portugalete mines, once very productive, and near the Argen tine border are the Lipez mines. East of the Cordilleras are the famous "silver mountain" of Potosi, once the richest silver mine in the world; the snow-capped peak of Chorolque (18,452 f t.), which is claimed to have the highest mine in the world 18,00o ft. above sea-level; Porco, a few miles south-west of Potosi; Guada lupe, Colquechaca and Aullagas. Besides silver most of these mines yield tin, copper and some other metals, and are now being worked chiefly for their tin. The production of minerals in these famous centres has recently been eclipsed by the enormously rich deposits of tin at Uncia and Llallagua in the same depart ment. The department is traversed by the Antofagasta & Bolivia railway and by the recently opened line from Uyuni to the Argentine frontier at La Quiaca. A branch line of the former also runs to Potosi via Porco, and within 3o m. of the city of Sucre (q.v.). Besides Potosi, the capital of the department, the principal towns are Huanchaca-Pulacayo (pop. about io,000) ; Uyuni, 9 m. from Huanchaca, 12,100 ft. above sea-level, a small town but an important railway junction and commer cial centre on the waterless plain, the shipping point and supply station for an extensive mining region; and Tupiza (pop. about 5,000), a prettily situated town near the Argentine frontier, on a small branch of the San Juan river, 9,80o ft. above sea-level.