a north-west and south-east direction between the 15th and 19th
parallels.

The popular conception of Bolivia is that of an extremely rugged
mountainous country, although fully three-fifths of it, including the
Chiquitos region, is composed of low alluvial plains, great swamps and
flooded bottomlands, and gently undulating forest regions. In the
extreme south are the Bolivian Chaco and the llanos (open grassy plains)
of Manzo, while above these in eastern Chuquisaca and southern Santa
Cruz are extensive swamps and low-lying plains, subject to periodical
inundations and of little value for agricultural and pastoral purposes.
There are considerable areas in this part of Bolivia, however, which lie
above the floods and afford rich grazing lands. The great drawback to
this region is defective drainage; the streams have too sluggish a
current to carry off the water in the rainy season. Between the
Chiquitos sierras and the Andes are the Llanos de Chiquitos, which have
a higher general elevation and a more diversified surface. North of this
elevation, which formed the southern shore of the ancient Mojos Lake,
are the llanos of Guarayos and Mojos, occupying an extensive region
traversed by the Guapore, San Miguel, Guapay, Mamore, Yacuma, Beni and
Madre de Dios rivers and their numerous tributaries. It was once covered
by the great Mojos Lake, and still contains large undrained areas, like
that of Lake Rojoagua (or Roguaguado). It contains rich agricultural
districts and extensive open plains where cattle-raising has been
successfully followed since the days of the Jesuit missions in that
region. The lower slopes of the Andes, especially toward the north-west,
where the country is traversed by the Beni and Madre de Dios, are
covered with heavy forests. This is one of the richest districts of
Bolivia and is capable of sustaining a large population.

The river-systems of Bolivia fall naturally into three distinct
regions--the Amazon, La Plata and Central Plateau. The first includes
the rivers flowing directly and indirectly into the Madeira, one of the
great tributaries of the Amazon, together with some small tributaries of
the Acre and Purus in the north, all of which form a drainage basin
covering more than one-half of the republic. The two principal rivers of
this system are the Mamore and Beni, which unite in lat. 10 deg. 20' S.
to form the Madeira. The Mamore, the upper part of which is called the
Chimore, rises on the nor