266 THE RIVER OF DOUBT [chap, viii 



north, and sometimes east of north, yet where there 

 were rapids the river had generally, although not always, 

 turned westward. This seemed to indicate that to the 

 east of us there was a low northward projection of the 

 central plateau across which we had travelled on mule- 

 back. This is the kind of projection that appears on 

 the maps of this region as a sierra. Probably it sent 

 low spurs to the west, and the farthest points of these 

 spurs now and then caused rapids in our course (for the 

 rapids generally came where there were hills), and for 

 the moment deflected the river westward from its 

 general down-hill trend to the north. There was no 

 longer any question that the Diivida was a big river, 

 a river of real importance. It was not a minor affluent 

 of some other affluent. But we were still wholly in the 

 dark as to where it came out. It was still possible, 

 although exceedingly improbable, that it entered the 

 Gy-Parana, as another river of substantially the same 

 size, near its mouth. It was much more likely, but not 

 probable, that it entered the Tapajos. It was probable, 

 although far from certain, that it entered the Madeira 

 low down, near its point of junction with the Amazon. 

 In this event it was hkely, although again far from 

 certain, that its mouth would prove to be the Aripuanan. 

 The Aripuanan does not appear on the maps as a 

 river of any size ; on a good standard map of South 

 America which I had with me its name does not appear 

 at all, although a dotted indication of a small river or 

 creek at about the right place probably represents it. 

 Nevertheless, from the report of one of his lieutenants 

 who had examined its mouth, and from the stories of 

 the rubber-gatherers, or seringuerros. Colonel Rondon 

 had come to the conclusion that this was the largest 

 affluent of the Madeira, with such a body of water that 



