Desaguadero (Span., drain). I. A navigable river of Bolivia, the outlet of Lake Titicaca, flowing 180 m. S. S. E. through the plain named from it, with a descent of about 490 ft., into Lake Aullagas, which has no outlet. Its width varies from 25 to 60 yards, and it is quite deep. The current is very slow. Near Lake Titicaca it is crossed by a bridge built by the fifth inca of Peru for the passage of his army. II. An immense inter-alpine plain comprised between the Cordilleras Oriental and Occidental of the Bolivian Andes, about one third in Peru, and the remainder in Bolivia, 400 m. long and from 30 to 80 m. wide. Save in the towns, the population is mainly made up of the Quichuas or Incas, and the Aymaras. From its elevation, which averages 13,340 ft., above the level of the sea, its extent, and the number and height of the snow-capped peaks by which it is surrounded, it has been called the Thibet of South America. The main element in the formation of the more elevated portions is trachytic conglomerates in various stages of decomposition, especially in the northern parts, which are intersected by isolated hills and low mountain ranges.

Corocoro to the north was long celebrated for its rich silver mines; and both silver and gold have been found in various localities, more particularly in the region contiguous to the Nevada de Illimani, from the base of which a large block of native gold was detached by lightning. The mass was afterward sold at an enormous price, and deposited in the museum of natural history at Madrid. The tin mines of Oruro are among the richest in the world; copper is said to be as plentiful in the mountain country as silver has been in the Cerro de Potosi; and many other minerals are likewise abundant; but, owing to the difficulty of transportation, these sources of wealth still lie unexplored. Of several thermal springs, those named Urimiri and Mochacamarca are the best known. Notwithstanding the intertropical situation of the valley, its elevation gives it a mild and salubrious climate. The year is divided into two seasons : summer, from November to April; and winter, from May to October. During the former, which is the wet season, almost every day brings rain, and the nights are often chilly, with occasional frost; but during the winter snow and fain are never seen, except at the commencement and end. Not a tree is to be seen.

The lower districts are clothed with a beautiful green turf, and in the valleys grows a coarse grass affording excellent pasture. Although the plain is well watered by the great Lake Titicaca, Lake Aullagas, the river Desaguadero connecting these lakes, another smaller lake, and many minor streams, the cereals do not attain maturity. Potatoes are plenty and grow wild; and the quinoa (chenopo-dium quinoa), often used as a substitute for the potato, is sedulously cultivated. The banks of Lake Titicaca have a luxuriant growth of rushes useful to the Indians for making huts, mats, boats, and other commodities. Remarkable among the fauna of the plain are the guanaco and the allied genera of alpacas, llamas, and vicunas, all of which roam in numbers in every direction, yielding abundant fleeces of precious wool. Numerous herds of cattle graze along the banks of the rivers; horses, asses, and mules are very plentiful; and there are two rodents, a species of hare, and the bizcocha, whose burrowings render travel on horseback dangerous in many localities. Some delicious fish are taken in the lakes and rivers.

Of the towns, which are few and small, Oruro is the most important.