I have stated the origin of the fable of the lake Cassipa, and the influence it has had on the opinion that the lake Parima is the source of the Orinoco. Let us now examine what relates to this latter basin, this pretended interior sea, called Rupunuwini by the geographers of the sixteenth century. In the latitude of four degrees or four degrees and a half (in which direction unfortunately, south of Santo Thome del Angostura to the extent of eight degrees, no astronomical observation has been made) is a long and narrow Cordillera, that of Pacaraimo, Quimiropaca, and Ucucuamo; which, stretching from east to south-west, unites the group of mountains of Parima to the mountains of Dutch and French Guiana. It divides its waters between the Carony, the Rupunury or Rupunuwini, and the Rio Branco, and consequently between the valleys of the Lower Orinoco, the Essequibo, and the Rio Negro. On the north-west of the Cordillera de Pacaraimo, which has been traversed but by a small number of Europeans (by the German surgeon, Nicolas Hortsmann, in 1739; by a Spanish officer, Don Antonio Santos, in 1775; by the Portuguese colonel, Barata, in 1791; and by several English settlers, in 1811), descend the Noeapra, the Paraguamusi, and the Paragua, which fall into the Rio Carony; on the north-east, the Rupunuwini, a tributary stream of the Rio Essequibo. Toward the south, the Tacutu and the Urariquera form together the famous Rio Parima, or Rio Branco. This isthmus, between the branches of the Rio Essequibo and the Rio Branco (that is, between the Rupunuwini on one side, and the Pirara, the Mahu, and the Uraricuera or Rio Parima on the other), may be considered as the classical soil of the Dorado of Parima. The rivers at the foot of the mountains of Pacaraimo are subject to frequent overflowings. Above Santa Rosa, the right bank of the Urariapara, a tributary stream of the Uraricuera, is called el Valle de la Inundacion. Great pools are also found between the Rio Parima and the Xurumu. These are marked on the maps recently constructed in Brazil, which furnish the most ample details of those countries. More to the west, the Cano Pirara, a tributary stream of the Mahu, issues from a lake covered with rushes. This is the lake Amucu described by Nicolas Hortsmann, and respecting which some Portuguese of Barcelos, who had visited the Rio Branco (Rio Parima or Rio Paravigiana), gave me precise notions during my stay at San Carlos del Rio Negro. The lake Amucu is several leagues broad, and contains two small islands, which Santos heard called Islas Ipomucena. The Rupunuwini (Rupunury), on the banks of which Hortsmann discovered rocks covered with hieroglyphical figures, approaches very near this lake, but does not communicate with it. The portage between the Rupunuwini and the Mahu is farther north, where the mountain of Ucucuamo* rises, the natives still call the mountain of gold. (* I follow the orthography of the manuscript