At the mouth of the Zama river we entered into a fluvial network worthy of attention. The Zama, Mataveni, Atabapo, Tuamini, Temi and Guianai rivers have aguas negras, that is, seen as a mass they appear brown like coffee, or greenish-black. These waters are, however, beautifully clear and very tasty. I have observed that crocodiles and mosquitoes, but not the zancudos, tend to avoid the black waters.

The Casiquiare Indians, though easily reverting to barbaric customs, show some intelligence in the missions, work well and learn Spanish. As most missions have two or three tribes speaking different languages the language of the missionaries lets them communicate with each other. I saw a Poignave Indian talk in Castilian with a Guahibo, though both had left the jungle only three months before. Every quarter of an hour one spoke a carefully prepared phrase in which the verb, following the grammar of their own languages, was always a gerund ('When me seeing the father, the father me saying...').

We left the Esmeralda mission on the 23rd of May. We were not exactly ill, but emaciated and weak thanks to the torment of mosquitoes, the bad food and the long journey on that narrow and damp pirogue. We did not go further up the Orinoco than the mouth of the Guapo; had we wanted to reach the Orinoco sources we would have gone beyond this point, but private travelers are not authorized to leave pacified areas. From the Guapo river to the Guaharibo cataract there are only 15 leagues. But the cataract is crossed by a liana bridge where Indians armed with bows and arrows stop whites from entering their lands. Up to the present time the Orinoco posed two distinct problems for geographers: its sources, and the nature of its communications with the Amazon. This latter was the aim of our journey.