92 SOUTH AMERICA— THE ANDES EEGIONS. 



Canaburi, belonging to the Rio Negro system. The ditch connecting the Orinoco 

 with the Cassiquiare stands at its highest point 920 feet above sea-level, and the 

 latter river receives from the Orinoco only a third part of the water which it 

 sends down to the Rio Negro. 



Below the bifurcation the Orinoco flows first west, then north-west, collecting 

 on one side a few sluggish streams from the llanos, on the other some rapid 

 currents from the Guiana uplands. One of these is the copious Ventuari, below 

 the confluence of which the Orinoco resumes its westerly course as far as the 

 Guaviare, whose farthest headstreams, the Guayabero and the Ari-Ari, rise in the 

 Sierra de Suma Paz, that is, in the Colombian Andes east of the upper 

 Magdalena. Although obstructed here and there by dangerous narrows, the 

 Guaviare, which sometimes takes the name of the Western Orinoco, presents 

 an extent of navigable waters at least equal to that of the mainstream. It is 

 accessible to steamers as far as the Ari-Ari confluence, a distance of 620 miles, 

 and the Ari-Ari itself, which ought to be regarded as the true headstream, 

 is said to be navigable throughout its lower course. 



At its junction with the Orinoco the Guaviare discharges a volume estimated 

 at 113,000 cubic feet. This junction may be regarded as the true hydrographie 

 centre of the whole region comprised between the Caribbean Sea and the Amazons 

 basin. Here converge two great lines of navigatioQ, traversing the continent 

 from east to west. From the Orinoco below the confluence another line, per- 

 pendicular to the first, forms the fluvial highway, while southwards the Inirida 

 and Atabapo rivers, being connected by portages with the Guainia (Rio Negro), 

 present a much shorter and easier route towards the Amazons than the winding 

 channel of the Cassiquiare. The water of the Guaviare is argillaceous, and of a 

 yellowish-white colour, whereas the Inirida and Atabapo are black, doubtless 

 owing to the presence of organic matter, as is the case with the Irish " Black- 

 waters," which have their source in boggy districts. The fishes of the Atabapo 

 are all black, and none of the alligators which swarm in the neighbouring 

 Guaviare ever penetrate into this river. Even mosquitos avoid its dark waters. 



North of the Guaviare confluence the Orinoco skirts the eastern hills and 

 mountains too closely to receive any but short and precipitous attluents from this 

 direction. But the gently inclined western plains send down long watercourses 

 parallel to the Guaviare ; amongst others, the Vichada, whose waters are black, 

 like those of the Atabapo. But the mainstream, which here flows at an altitude 

 of 510 feet, has still to surmount some granite ledges before reaching the level 

 of its normal incline towards the Atlantic. Instead of following the foot of the 

 eastern mountains, it forces a passage through their projecting spurs, so that the 

 Clio's of the left as well as of the right bank belong to the Guiana orographic 

 system. The first great randal, or cataract, takes the name of Malpures from a 

 villag-e and an old Indian tribe now reduced to a few families of half-breeds. 

 From the crests of the granite rocks overlooking the falls the river is seen 

 breaking into several arras and into countless little channels, M^hich shift their 

 course aud volume with the seasons. Amid these winding channels rise verdant 



