A S. W. Department Of Bolivia, bounded N. by Oruro, N. E. by Chuquisaca, E. by Tarija, S. by the Argentine Republic, and W. by Atacama and Peru; area, 54,297 sq. m.; pop. in 1865, 290,304, of whom about three fourths were Indians. The surface is an elevated table land, mostly rugged and mountainous, traversed by many abrupt ridges, which increase in height toward the Cerro de Potosi. This mountain is a nearly perfect cone, rising 16,000 ft. above the sea. The country is generally of volcanic formation, but this peak is an exception. It is crowned with a bed of porphyry, but its lower part is composed of a yellow argillaceous schist, filled with veins of ferruginous quartz, in which are rich deposits of silver. It seems to be the culminating point in a metallic chain which is unexcelled for richness. More than 5,000 mines have been opened in it. The top is completely honeycombed and exhausted, and the miners now work lower down, where the influx of water has compelled the abandonment of many of the richest veins. The Oerro de Porco, a little S. W. of it, is also celebrated for mineral wealth. The department is generally barren and sterile, and the mountainous parts are very cold. It is drained by several affluents of the Pilcomayo. The chief production is silver.
Between 1545 and 1789 the mines of Potosi yielded $1,000,000,000 in silver, and they still give .an annual yield of $2,250,000. The name signifies an eruption of silver. The mines are worked almost exclusively by Indians. Potosi produces also gold, copper, iron, lead, tin, quicksilver, zinc, antimony, manganese, cobalt, potassium, sulphur, white clay, precious stones, and other minerals.
A City, capital of the department, on the N. slope of the mountain of the same name, about 13,500 ft. above the sea, 65 m. W. S. W. of Sucre; pop. in 1865, 25,774. The surrounding country is bleak and barren, and the atmosphere, except where tempered by the sun's rays, cold and piercing. It is the fourth city of Bolivia in point of population, but in the 17th century it contained 150,000 inhabitants. The greater part of the town is in ruins, but the central square, which contains the government house, public offices, a church, and a convent, is still in tolerable repair. The mint is a very large edifice, and contains the machinery which in former times did a vast amount of work, but only little over $2,000,-000 is now coined annually. There are numerous churches, a college, several primary schools, and 'a few others for the children of the miners. The plaza of Ayacucho was constructed in honor of the battle which in 1824 decided the independence of South America, and contains a lofty cylindrical shaft surmounted by a statue of Liberty. The town is supplied with water from 37 tanks, 8 or 10 m. distant, which were constructed at great expense about 200 years ago. The country in the immediate neighborhood produces nothing.
Considerable quantities of English and French manufactures are consumed there.