MAPPING AN UNKNOWN RIVER 305 



whom had lived in the neighbourhood for eight or ten 

 years ; and yet on no standard map was there a hint of 

 the river's existence. We were putting on the map 

 a river, running through between five and six degrees 

 of latitude — ^of between seven and eight if, as should 

 properly be done, the lower Aripuanan is included as 

 part of it — of which no geographer, in any map pub- 

 lished in Europe, or the United States, or Brazil, had 

 even admitted the possibility of the existence ; for the 

 place actually occupied by it was filled, on the maps, 

 by other — imaginary — streams, or by mountain ranges. 

 Before we started, the Amazonas Boundary Commission 

 had come up the lower Aripuanan, and then the eastern 

 branch, or upper Aripuanan, to 8° 48', following the 

 course which for a couple of decades had been followed 

 by the rubber-men, but not going as high. An em- 

 ployd, either of this Commission or of one of the big 

 rubber-men, had been up the Castanho, which is easy 

 of ascent in its lower course, to about the same latitude, 

 not going nearly as high as the rubber-men had gone ; 

 this we found out while we ourselves were descending 

 the lower Castanho. The lower main stream, and the 

 lower portion of its main affluent, the Castanho, had 

 been commercial highways for rubber-men and settlers 

 for nearly two decades, and, as we speedily found, were 

 as easy to traverse as the upper stream, which we had 

 just come down, was difficult to traverse ; but the 

 governmental and scientific authorities, native and 

 foreign, remained in complete ignorance ; and the 

 rubber-men themselves had not the slightest idea of 

 the headwaters, which were in country never hitherto 

 traversed by civilized men. Evidently the Castanho 

 was, in length at least, substantially equal, and probably 

 superior, to the upper Aripuanan ; it now seemed even 



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