ly, and by longer
channels. The largest of them is the Segovia, in Nicaragua and
Honduras, which has a course of 450 m. Lake Nicaragua, the largest
inland sheet of water, has an area exceeding 3500 sq. m. There are
also several mountain lakes of exceptional interest and beauty, such
as Atitlan and Amatitlan, in Guatemala, besides two great land-locked
salt-water lakes--the Pearl Lagoon of the Mosquito Coast, and the
Carataska Lagoon in Honduras.

[Illustration: Geologic Map of Central America.]

_Geology._--The neck of land which unites the continents of North and
South America is not, geologically, the direct continuation of either,
but constitutes a third element which is wedged, as it were, between
the other two. The folds in the earth's crust which form the Andes and
the Western ranges of North America, are not continued along the
connecting isthmus, where, on the contrary, the strata are folded from
west to east, obliquely across the trend of the continent. It should,
however, be noticed that the Andes, as they approach the Caribbean
sea, bend round towards the east; and it is probable that the folds of
the North American Cordillera similarly bend eastward beneath the
volcanic rocks of Mexico. The folds of Central America are tangential
to the two arcs thus formed.

By far the greater part of Central America and Mexico is covered by
Cretaceous and Tertiary deposits, both sedimentary and volcanic; but
the foundation on which they rest is exposed at intervals. From the
Rio Grande to the southern declivity of the Mexican plateau the
existence of ancient crystalline rocks at the surface is yet unproved,
but they probably occur in the Sierra Madre del Pacifico. South of the
plateau, in the state of Oaxaca, low mountain ridges composed of
granites and gneisses, supposed to be of Archaean age, begin to
appear. They strike from west to east, and mark the front of the
series of east and west folds which stand _en echelon_ across the
Central American region. Between the 15th and 17th parallels of
latitude, in the state of Chiapas and in the republic of Guatemala,
there is a second group of ridges composed of granites and schists
with an eastward trend. In this case the evidence of age is clear, for
the rocks are covered by a limestone which is proved to be
Pre-Carboniferous. Similar rocks, supposed to be of Archaean or at
least of early Palaeozoic a