316 MY LIFE [Chap. 



During the two ascents and descents of the Rio Negro 

 and Uaup6s in 1850-1852 I took observations with a prismatic 

 compass, not only of the course of the canoe, but also of 

 every visible point, hill, house, or channel between the islands, 

 so as to be able to map this little known river. For the 

 distances I timed our journey by a good watch, and estimated 

 the rate of travel up or down the river, and whether paddling 

 or sailing. With my sextant I determined several latitudes 

 by altitudes of the sun, or of some of the fixed stars. The 

 longitudes of Barra and of San Carlos, near the mouth of the 

 Cassiquiare, had been determined by previous travellers, and 

 my aim was to give a tolerable idea of the course and width 

 of the river between these points, and to map the almost 

 unknown river Uaupes for the first four hundred miles of its 

 course. From these observations I made a large map to 

 illustrate a paper which I read before the Royal Geographical 

 Society. This map was reduced and lithographed to accom- 

 pany the paper, and as it contains a good deal of information 

 as to the nature of the country along the banks of the rivers, 

 the isolated granite mountains and peaks, with an enlarged 

 map of the river Uaupes, showing the position of the various 

 cataracts I ascended, the Indian tribes that inhabit it, with 

 some of the more important vegetable products of the sur- 

 rounding forests, it is here given to illustrate this and the two 

 preceding chapters (see p. 320). It will also be of interest to 

 readers who possess my " Travels on the Amazon and Rio 

 Negro," which was published before the map was available. 



The great feature of this river is its enormous width, often 

 fifteen or twenty miles, and its being so crowded with islands, 

 all densely forest-clad and often of great extent, that for a 

 distance of nearly five hundred miles it is only at rare intervals 

 that the northern bank is visible from the southern, or vice 

 versd. For the first four hundred and fifty miles of its course 

 the country is a great forest plain, the banks mostly of alluvial 

 clays and sands, though there are occasional patches of sand- 

 stone. Then commences the great granitic plateau of the 

 upper river, with isolated mountains and rock-pillars, extend- 

 ing over the watershed to the cataracts of the Orinoko, to the 



