The northern slope of this great plateau is drained by the AraguayaTocantins, Xingu, Tapajos and Guapore-Mamore-Madeira, which flow northward, and, except the first, empty into the Amazon; the southern slope drains southward through a multitude of streams flowing into the Parana and Paraguay.
"very small"), a group of tribes in the province of Santa Cruz de la Sierra, Bolivia, and between the head waters of the rivers Mamore and Itenez.
Evans, " The Rocks of the Cataracts of the River Madeira and the adjoining Portions of the Beni and Mamore," Quart.
6° 52' 15" S., which is half the distance between the mouth of the Mamore and the mouth of the Madeira, divides the Spanish and Portuguese possessions in this part of South America, according to the provisions of the treaty of San Ildefonso of 1777.
West of the Cordillera Oriental, where special conditions prevail, a great desert plateau stretches entirely across one corner of the republic. Apart from the Andean system there is a group of low, broken, gneiss ranges stretching along the east side of Bolivia among the upper affluents of the Mamore and Guapore, which appear to belong to the older Brazilian orographic system, from which they have been separated by the erosive action of water.