e comparatively unimportant, but
from Bolivia it receives the Baures and the San Miguel, both rising in
the Sierras de Chiquitos and flowing north-west across the llanos to the
Guapore. The Baures has one large tributary, the Blanco, and the Itonama
(San Miguel) has its origin in Lake Conception, lying among the west
ranges of the Chiquitos mountains 952 ft. above sea-level.

The south-east drainage basin, which is smaller and economically less
important than that of the Madeira, discharges into the Paraguay and
extends from the Sierras de Chiquitos south to the Argentine frontier,
and from the Cordillera Oriental east to the Paraguay. It possesses only
one large river in Bolivia, the Pilcomayo, which rises on the east
slopes of the Cordillera Oriental opposite the south end of Lake Pampa
Aullaguas and flows east and south-east through the sierra region to the
Bolivian Chaco. It flows through a nearly level country with so sluggish
a current that its channels are greatly obstructed. Nothing definite is
known of its tributaries in the Chaco, but in the sierra region it
possesses a number of small tributaries, the largest of which are the
Cachimayo, Mataca and Pilaya or Camblaya, the latter formed by the
Cotagaita and San Juan. The Bermejo, which is an Argentine river,
receives one large tributary from the Bolivian uplands, the Tarija or
Rio Grande, which drains a small district south-east of the Santa
Victoria sierra. The Bolivian tributaries of the upper Paraguay are
small and unimportant. The Otuquis, the most southern of the group, is
formed by the San Rafael and Tucabaca, which drain both slopes of the
Cerro Cochii range; but is lost in some great marshes 50 m. from the
Paraguay. Another considerable stream of this region, which is lost in
the great marshy districts of the Bolivian plain, is the Parapiti, which
rises on the eastern slopes of the Sierra de Misiones and flows
north-east through a low plain for about 150 m. until lost.

The third drainage basin is that of the great central plateau, or
_alta-planicie_. This is one of the most elevated lacustrine basins in
the world, and though it once drained eastward, now has no surface
outlet. Lake Titicaca receives the waters of several short streams from
the neighbouring heights and discharges through the Desaguadero, a
sluggish river flowing south for 184 m. with a gradually diminishing
depth to Lake Pampa Aullaguas or Poopo. The Desaguadero is navigable for
small