559 



Rio Matacona falls. At the sources of the lat- 

 ter live the Guainares, who are much less cop- 

 per-coloured, or tawny, than the other inhabi- 

 tants of those countries. This is one of the 

 tribes called by the missionaries^^ Indians, or ' 

 Indios blancos, respecting whom I shall soon 

 treat more at large. Near the mouth of the 

 Ocamo, travellers are shown a rock, which is the 

 wonder of the country. It is a granite passing 

 into gneiss, and remarkable for the peculiar dis- 

 tribution of the black mica, which forms little 

 ramified veins. The Spaniards call this rock 

 Piedra Mapaya (the map-stone). The little 

 fragment which I procured indicated a stratified 

 rock, rich in white feldspar, and containing, 

 beside spangles of mica, which are grouped in 

 streaks, and variously twisted, some crystals of 

 hornblende. It is not a syenite, but probably a 

 granite of new formation, analagous to those, to 

 which the stanniferous granites (hyalomictes), 

 and the pegmatites, or graphic granites, belong. 



Beyond the confluence of the Mavaca, the 

 Oroonoko suddenly diminishes in breadth and 

 depth, becoming extremely sinuous like an 

 Alpine torrent. It's two banks are surrounded 

 by mountains, and the number of it's tributary 

 streams on the south augments considerably, 

 yet the Cordillera on the north remains the 

 most elevated. It requires two days to go 

 from the mouth of the Mavaca to the Rio Gi» 



