No astronomical instruments had been brought along during the frontier expedition in this region, so with my chronometer, and by the meridional height of the stars, I established the exact location of San Baltasar de Atabapo, Javita, San Carlos de Río Negro, the Culimacarai rock and the Esmeralda mission. The map I drew has resolved any doubts about the reciprocal distances between the Christian outposts. When there is no other road but the tortuous and intricate river; when little villages lie hidden in thick jungle; when in a completely flat country with no mountains visible, you can read where you are on earth only by looking up to the sky.

When we were about to leave the Can mission we had an argument with our Indian muleteers. To our amazement they had discovered that we were transporting skeletons from the Ataruipe caves, and were sure that the mule carrying 'the corpses of our ancient relatives' would die on the journey. All our precautions to hide the bones had been useless; nothing escapes the Carib's sense of smell. We needed the missionary's authority to be able to leave. We had to cross the Can river in a boat and ford, or perhaps I should say swim, the Río de Agua Clara. Quicksand on the bottom made the crossing during the floods very tiring. You are surprised to find such strong currents in flat land. We spent unpleasant nights out at Matagorda and Los Riecitos. Everywhere we saw the same things: small huts made of reed and roofed with leather, men on horseback with lances, guarding the cattle, semi-wild herds of horned cattle all the same color, fighting for grass with horses and mules. Not a goat or a sheep in these immense steppes!

On the 12th we continued our journey to the Caripe monastery, center of the Chaima Indian missions. Instead of the direct road, we chose the one that passes by the Cocollar (54) and Turimiquiri mountains. We passed the little Indian village of Aricagua, pleasantly located in wooded hills. From there we climbed up hill for four hours. This part of the route is very tiring; we crossed the Pututucuar, whose river bed is packed with blocks of calcareous rock, twenty-two times. When we had reached the Cuesta del Cocollar, some 2, feet above sea-level, we saw, to our surprise, that the jungle of tall trees had vanished. Then we crossed an immense plain covered in grass. 0nly mimosas, with hemispheric tops and trunks some 4 to 5 feet in diameter, break the desolate monotony of the savannahs. Their branches are bent towards the ground, or spread out like parasols.

May 10th. Overnight our canoe was loaded and we set off a little before dawn to go up the Río Negro to the mouth of the Casiquiare and begin our researches on the true course of this river linking the Orinoco and Amazon. The morning was beautiful, but as the heat rose the sky began to cloud over. The air is so saturated with water in these forests that water bubbles become visible at the slightest increase of evaporation on the earth's surface. As there is no breeze the humid strata are not replaced and renewed by drier air. This clouded sky made us gloomier and gloomier. Through this humidity Bonpland -lost the plants he had collected; for my part I feared finding the same Río Negro mists in the Casiquiare valley. For more than half a century nobody in the missions has doubted the existence of communications between the two great river systems: the important aim of our journey was reduced to fixing the course of the Casiquiare by astronomic means, especially at its point of entry into the Río Negro, and its bifurcation with the Orinoco. Without sun or stars this aim would have been frustrated, and we would have been uselessly exposed to long, weary deprivation. Our travelling companions wanted to return by the shortest journey, along the Pimichín and its small rivers; but Bonpland preferred, like myself, to persist in the original plan we had traced out while crossing the Great Cataracts. We had already traveled by canoe from San Fernando de Apure to San Carlos along the Apure, Orinoco, Atabapo, Temi, Tuamini and Río Negro for over 180 leagues. In entering the Orinoco by the Casiquiare we still had some 320 leagues to cover from San Carlos to Angostura. It would have been a shame to let ourselves be discouraged by the fear of a cloudy sky and the Casiquiare mosquitoes. Our Indian pilot, who had recently visited Mandavaca, promised us sun and 'those great stars that eat up clouds' once we had left the black waters of the Guaviare. So we managed to carry out our first plan and returned to San Fernando along the Casiquiare. Luckily for our researches the Indian's prediction was fulfilled. The white waters brought us a clear sky, stars, mosquitoes and crocodiles.

Towards night we reached a small farm in the port of Caìo Pimichín. We were shown a cross near the river, which marked a spot 'where a poor Capuchin missionary had been killed by wasps'. Here people talk a lot about poisonous wasps and ants, but we were not able to find any. It is well known that in the torrid zone tiny bites bring on intense fevers. The death of the luckless monk was more likely the result of exhaustion and dampness than the poison in the wasps stings, which the Indians also dread.

The extreme purity of the black waters is confirmed by their transparency, and by the way they clearly reflect all the surrounding objects. The minutest fish are visible at a depth of 20 or 30 feet. It is easy to see the river bottom, which is not muddy but composed of a dazzlingly white granite or quartz sand. Nothing can be compared to the beauty of the Atabapo river banks, overloaded with vegetation, among which rise the palms with plumed leaves, reflected in the river water. The green of the reflected image seems as real as the object seen with your eyes.

We set sail on the 9th of March before dawn, nervous about the uncomfortable narrow boat in which we had to sleep on deck. The cabin (càmara de pozo) had no light or air and was merely a hold for provisions; we could only just fit our instruments in there. These inconveniences lasted only twenty days.