LONDON, AND VOYAGE TO SINGAPORE 317 



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 given here, 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 

 versa. 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 

 mountains of Guiana, and, perhaps, in some parts up to the 

 foot of the Andes. The other great peculiarity of the river 

 is its dark brown, or nearly black, waters, which are yet 

 perfectly clear and pleasant to drink. This is due, no doubt, 

 to the greater part of the river's basin being an enormous 

 forest-covered plain, and its chief tributaries flowing over 

 granite rocks. It is, in fact, of the same nature as the coffee- 



