Some twenty miles above Maipures the Orinoco receives the large volume of water drained by the River Vichada from the llanos of the San Martin territory of Colombia, and a little over one hundred miles from Maipures the Guaviare and Atabapo discharge their waters side by side into the main stream. From the mouth of the Guaviare up to Esmeralda is probably the best known portion of the upper valley, since it is here that the majority of small rubber prospectors have obtained small fortunes after a short period of hard and rough labour in the insect-infested forests. The same causes as those referred to above in the lower parts of the Orinoco have here also prevented more systematic and continuous exploitation; those who have ventured to brave the discomforts and dangers of the forest have almost invariably retired with their gains to taste such pleasures of civilisation as the towns of the Lower Orinoco and neighbouring regions afford; thus the scanty population remains stationary, and previously, from want either of sufficient interest or opportunity, capital has never attempted to introduce colonists or to develop the resources of the region with such labour as can be had. The _picadores de goma_ have thus only seen the forests along the river for a few kilometres on either bank, and the remoter parts of the region are as little known as any other part of the territory of the Amazons. The rubber collectors enter the forest in the month of October, the season lasting from then to February or March, and parcel out the forest among themselves, each man taking an area including some five hundred trees or more. He then proceeds to cut an _estrada_ through the forest along a tortuous course, so arranged that about half the rubber-trees lie on either side. He will begin to traverse this path at sunrise and tap the trees of either group on alternate days, the latex being carried back to the river late in the day and put to smoke in huts by the river. Each day he may collect eight or ten gallons of sap, and so twelve or fifteen hundredweight in the season, in addition to inferior gums derived from the creepers which hang everywhere from the large forest trees. The rubber and other valuable trees, including the wild cacao and brazil-nuts, seem to become less scattered above Maipures, and this is doubtless an additional reason for the greater extent of exploitation in this more remote district, while it should also be remembered that the Casiquiare affords a highway for the bold and industrious Banibas and other Indians of the Rio Negro basin to the rubber-producing forests, which afford better returns than those in their immediate neighbourhood.