ich was explored by Crevaux in 1878-1879.
At Santa Maria, near the Cordillera (about 75 deg. 30' W. long.), the
elevation is 613 ft. above sea-level, on the 73rd meridian it is 538
ft., and near the 70th meridian 426 ft.--a fall of 187 ft. in a
distance of about 400 m. The northern part of this great region has a
somewhat lower elevation and gentler slope, and consists of open
grassy plains, which are within the zone of alternating wet and dry
seasons. In the south and toward the great lower basin of the Amazon,
where the rainfall is continuous throughout the year, the plains are
heavily forested. The larger part of this territory is unexplored
except along the principal rivers, and is inhabited by scattered
tribes of Indians. Near the Cordilleras and along some of the larger
rivers there are a few small settlements of whites and mestizos, but
their aggregate number is small and their economic value to the
republic is inconsiderable. There are some cattle ranges on the open
plains, however, but they are too isolated to have much importance. A
small part of the northern Colombia, on the lower courses of the
Atrato and Magdalena, extending across the country from the Eastern
to the Western Cordilleras with a varying width of 100 to 150 m., not
including the lower river basins which penetrate much farther inland,
also consists of low, alluvial plains, partly covered with swamps and
intricate watercourses, densely overgrown with vegetation, but in
places admirably adapted to different kinds of tropical agriculture.
These plains are broken in places by low ranges of hills which are
usually occupied by the principal industrial settlements of this part
of the republic, the lower levels being for the most part swampy and
unsuited for white occupation.

[Illustration: COLOMBIA]

The other part of the republic, which may be roughly estimated at
two-fifths of its total area, consists of an extremely rugged
mountainous country, traversed from south to north by the parallel
river valleys of the Magdalena, Cauca and Atrato. The mountain chains
which cover this part of Colombia are the northern terminal ranges of
the great Andean system. In northern Ecuador the Andes narrows into a
single massive range which has the character of a confused mass of
peaks and ridges on the southern frontier of Colombia. There are
several lofty plateaus in this region which form a h