THE BOLIVIAN ElVEES— CLIMATE. 865 



ia 1884 by Armentia, the explorer best acquainted with the forest regions of east 

 Bolivia, who ascended the river up to Peruvian territory. 



On the other hand, the Purus was also surveyed as far as the region of its 

 headwaters, while the whole basin has been traversed in all directions by the 

 collectors of rubber. Hence there can no longer be any doubt that the Inambari, 

 flowing north-west parallel with the Carabaya Alps, effects a junction with the 

 Beni winding to the north-east. At the confluence the Madre de Bios (lower 

 Inambari), much the broader of the two, is 1,260 yards wide from bank to bank. 

 Farther down the united stream is precipitated a vertical height of 30 feet. 



The Pilcomayo. 



South-east Bolivia sends its running waters through the Pilcomayo to the 

 Paraguay. Rising inclose proximity to theGuapay (Rio Grande), the Pilcomayo 

 flows south-east, successively piercing several chains, and after its junction with 

 the Pilaya, a river of equal volume, winds in a shallow bed through the plains of 

 Gran Chaco. A few headstreams of the Bermejo have also their sources in 

 Bolivian territory, while the upper Paraguay receives some small tributaries, of 

 which the Otuquis is the most important, from the eastern savannas and the 

 upland valleys of the Chiquito mountains. Lastly, in the broad space between 

 the Mamore and Pilcomayo affluents various watercourses of undecided incline 

 run out in closed basins on the divide, leaving saline incrustations on their banks. 



In this part of Bolivia, where the rainfall is deficient, the lakes or lagoons are 

 due mainly to the small volume of the streams, which lack the strength to excavate 

 deep and regular channels. In the north, on the contrary, that is, in the Beni 

 and Mamore basins, the analogous formations owe their origin to the super- 

 abundance of water which overflows into the lacustrine depressions skirting both 

 sides of the rivers. The Pogoaguado, one of these basins of fluvial origin, 

 between the Beni and the Mamore, is reported to cover a space some thousand 

 square miles in extent. 



IV. 



Climate. 



In Bolivia the climate varies with the zones of the plateau, the Cordilleras, 

 the upland regions sloping eastwards, the Yungas valleys and the eastern plains, 

 while the zones themselves are further modified by latitude. Being comprised 

 within the tropics, Bolivia would naturally be a land of extreme heat but for 

 the great elevation of its plateaux and highlands, which give it the advantage 

 of a superimposed series of climates, ranging from a torrid to an arctic tempera- 

 ture. 



The districts in which the towns have been founded and where the populations 

 are mostly concentrated, between the altitudes of 12,500 and 8,000 feet, have a 

 mean temperature ranging from 54° to 61° Fahr. Here the south-east trade 



