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.
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.
The Mamore, the upper part of which is called the Chimore, rises on the north-east slopes of the Sierra' de Cochabamba a little south of the 17th parallel, and follows a northerly serpentine course to its confluence with the Beni, the greater part of which course is between the 65th and 66th meridians.
The principal Bolivian tributary of the Mamore, the Guapay or Grande, which is larger and longer than the former above their confluence and should be considered the main stream, rises in the Cordillera Oriental east of Lake Pampa Aullaguas, and flows east to the north extremity of the Sierra de Misiones, where it emerges upon the Bolivian lowlands.
Turning to the north in a magnificent curve, it passes around the south-east extremity of the Sierra de Cochabamba, skirts the Llanos de Chiquitos, and, turning to the north-west, unites with the Mamore at Junta de los Rios in about 15° 20' S.
The other large Bolivian tributaries of the Mamore, all rising on the north-east flanks of the Andes, are the Chapare, Secure, Manique or Apere and Yacuma, the last draining a region of lakes and swamps north of the Sierra Chamaya.
The Beni and its great affluent, the Madre de Dios, though of smaller volume and extent than the Mamore, are of much greater economic importance, owing to their navigability, the fertility of the region they drain, and the great forests along their banks.
The Guapore, or Itenez, an affluent of the Mamore, is the third large river of this Bolivian drainage basin, but it rises in Brazil, on the south slopes of the Sierra dos Parecis, where it flows in a great bend to the south and then west of north to the Bolivian frontier in 14° S.
From this point to its junction with the Mamore, a little north of the 12th parallel, it flows in a northwesterly direction and forms the boundary line between the two republics.
The great lacustrine basin between the Beni and the Mamore contains several lakes and lagoons, two of them of large size.
The Bolivian port of entry for this trade, Villa Bella, is situated above the falls of the Madeira at the confluence of the Beni and Mamore, and is reached from the lower river by a long and costly portage.
The first includes the Guapay or Rio Grande, Piray or Sara, Yapacani and Marac6, upper tributaries of the Mamore, and the San Miguel, Blanco, Baures and Paragua, tributaries of the Guapore - both draining the western and northern parts of the department.
The capital and only large town of the department is Santa Cruz De La Sierra (pop., in 1900, 15,874; in 1906, estimated, 20,535), on the Piray, a tributary of the Mamore, 1450 ft.
The waters find their way to the falls of the Madeira by many great rivers, the principal of which, if we enumerate them from east to west, are the Guapore or Itenez, the Baures and Blanco, the Itonama or San Miguel, the Mamore, Beni, and Mayutata or Madre de Dios, all of which are reinforced by numerous secondary but powerful affluents.
The Guapore presents many difficulties to continuous navigation; the Baures and Itonama offer hundreds of miles of navigable waters through beautiful plains; the Mamore has been sounded by the writer in the driest month of the year for a distance of 500 m.
It makes a long curve through the mountains, and, after a course of about Boo m., joins the Mamore near 15° S.
The Chapare, Secure and Chimore, tributaries of the Mamore, are navigable for launches up to the base of the mountains, to within 130 m.
Beni, a river of Bolivia, a tributary of the Madeira, rising in the elevated Cordilleras near the city of La Paz and at first known as the Rio de La Paz, and flowing east, and north-east, to a junction with the Mamore at 10 20' S.
Above its confluence with the Mamore, where a fall of 20 ft.
The capital, Trinidad (pop. 2556), is situated on the Mamore river in an open fertile country, and was once a flourishing Jesuit mission.