ma. The eastern boundary of Central America
was usually regarded as identical with that of Costa Rica until 1903,
when the republic of Panama was formed out of the northern territories
of Colombia; and the more modern definition given above does not command
the universal assent of geographers, because it fails to include the
whole region up to the natural frontier on the north-west, i.e. the
Isthmus of Tehuantepec in Mexico. It has, however, the support of
political and historical considerations, as well as of common usage; and
it may therefore be regarded as adequate, although, in respect of
climate and natural products, it would be more accurate to define
Central America as lying between Tehuantepec and Darien.

_Physical Features._--The _Cordilleras_, or mountain chains of Central
America do not form a complete link between the western ranges in the
north and south of the continent, for their continuity is interrupted
by various depressions, of which the chief is the lacustrine basin of
Nicaragua. With these exceptions, they traverse Central America from
end to end, their main axis trending from north-west to south-east.
They do not, as a rule, rise in sharply serrated ridges or series of
volcanic crests, like the Andes, but the central Cordilleras are
disposed in a succession of mountain masses, with many lesser chains
radiating from them. The principal summits have an altitude of 12,000
and even, in a few cases, of 13,000 ft., and the general character of
the ranges is volcanic, many craters being still active. Large tracts
of land remained imperfectly surveyed at the beginning of the 20th
century, owing to the unhealthiness of the tropical climate, and the
dense underwoods which impede exploration. In the northern part of
Guatemala, on the Pacific coast of the same country, in British
Honduras, along the Segovia river, on the Mosquito Coast, and in the
basin of Lake Nicaragua and the San Juan river, there are broad
stretches of comparatively flat country. The main line of watershed is
everywhere nearer to the Pacific than to the Atlantic, except in
southern Costa Rica and Panama, where it is almost equidistant from
the two oceans. In consequence, the rivers of the Pacific seaboard are
mostly short and swift,--mere mountain torrents, in many instances,
until they reach the sands and swamps which border the sea. The rivers
of the Atlantic littoral descend more gradual