., and Cerro
Dona Ines, 16,706 ft. It is broken to some extent in crossing the
province of Antofagasta, the southern division being known as the
Sierra de Huatacondo. At the southern frontier of Bolivia the main
chain, which has served as the boundary line between Argentina and
Chile, divides into two great ranges, the principal one continuing
almost due north along the eastern side of the great Bolivian
_alta-planicie_, and the other forming its western rim, where it is
known as the Cordillera Silillica, and then following the trend of the
coast north-westward into Peru becomes the Cordillera Occidental. The
western slopes of the Andes are precipitous, with short spurs
enclosing deep valleys. The whole system is volcanic, and a
considerable number of volcanoes are still intermittently active,
noticeably in central and southern Chile. The culminating point of the
Chilean Andes is Aconcagua, which rises to a height of 23,097 ft.

In southern Chile the coast is highly mountainous, but the relation of
these elevations to the Andes has not been clearly determined. The
highest of these apparently detached groups are Mt. Maca (lat. 45 deg.
S.), 9711 ft., and Mt. Arenales (about 47 deg. S. lat.), 11,286 ft.
Cathedral Peak on Wellington Island rises to a height of 3838 ft. and
the highest point on Taytao peninsula to 3937 ft. The coast range of
central Chile has no noteworthy elevations, the culminating point in
the province of Santiago being 7316 ft. Between central Chile and the
northern desert region there is a highly mountainous district where
distinct ranges or elongated spurs cross the republic from the Andes
to the coast, forming transverse valleys of great beauty and
fertility. The most famous of these is the "Vale of Quillota" between
Valparaiso and Santiago. The Chilean Andes between Tacna and Valdivia
are crossed by 24 passes, the majority of them at elevations exceeding
10,000 ft. The best-known of these is the Uspallata pass between
Santiago and the Argentine city of Mendoza, 12,870 ft. above
sea-level. The passes of central and southern Chile are used only in
the summer season, but those of northern Chile are open throughout the
whole year.

The volcanic origin of the Andes and their comparatively recent
elevation still subject Chile, in common with other parts of the
western coast region, to frequent volcanic and seismic disturbances.
In