is point and form the _massif_ of the Andean
system. It is made up of a number of parallel ranges enclosing great
elevated plateaus broken by transverse ranges and deep ravines.
North-east of Lake Titicaca there is a confused mass or knot (the Nudo
de Apolobamba) of lofty intersecting ridges which include some of the
highest peaks in South America. Below this mountainous area the ranges
open out and enclose extensive plateaus. The western range, the
Cordillera Occidental, a part of the boundary between Bolivia and the
northern provinces of Chile, closely follows the coast outline and forms
the western rampart of the great Bolivian tableland or _alta-planicie_,
which extends from the Vilcanota knot in Peru, south to the Serrania de
Lipez on the Argentine frontier, is 500 m. long, and about 80 m. broad,
and contains about 40,000 sq. m. The northern part of this plateau is
commonly called the _puna_; the southern part, the "desert of Lipez," in
character and appearance is part of the great Puna de Atacama. This
plateau has an average elevation of about 12,650 ft. near Lake Titicaca,
but descends about 1000 ft. toward its southern extremity. It is a great
lacustrine basin where once existed an inland sea having an outlet to
the east through the La Paz gorge. The plateau is bleak and inhospitable
in the north, barren and arid toward the south, containing great saline
depressions covered with water in the rainy season, and broken by ridges
and peaks, the highest being the Cerro de Tahua, 17,454 ft. Overlooking
the plateau from the west are the snow-clad peaks of Pomarape (20,505
ft.), Parinacota (20,918 ft.), Sajama (21,047), Huallatiri (21,654),
Lirima (19,128), and the three volcanic peaks, Oyahua (19,226), San
Pedro y Pablo (19,423) and Licancaur (19,685). The eastern rampart of
this great plateau is formed by the Cordillera Oriental, which extends
north-west into Peru under the name of Carabaya, and south to the
frontier in broken ranges, one of which trends south-east in the
vicinity of Sucre. The main part of this great range, known as the
Cordillera Real, and one of the most imposing mountain masses of the
world, extends from the Peruvian border south-east to the 18th parallel
and exhibits a series of snow-crowned peaks, notably the triple-crested
Illampu or Sorata (21,490 ft.), Illimani (Conway, 21,204), Cacaaca
(20,571) and Chachacomani (21,434). Of the ranges extending south from
the Cordillera Real and branching out