See Rio Negeo.
A River Of South America, an affluent of the Amazon, which rises in the Sierra Tunuhy, an isolated group of hills in the state of Cundinamarca, United States of Colombia. Above the Cassiquiare it is called the Guainia, and a portion of its lower part is known as the Paraná Pishuna. After flowing E. about 200 m. from its source, it turns S. to lat. 2° N., where it is joined by the Cassiquiare, whose mouth is 600 yards wide, and which connects it with Orinoco. (See Cassiquiare.) About 50 m. below this it enters Brazil, and at the equator is joined by the Uaupes or Ucayari, which rises in the same hills as the Negro, but pursues a widely divergent course. After the junction the Negro descends over a series of rapids to São Gabriel, about 600 m. from its mouth at Manaos, and then becomes navigable, with a current of 3 or 4 m. an hour, flowing E. about 250 m. and receiving many tributaries. About lon. 63° W. it receives the Rio Branco, after which it turns S. E., widens in some parts to 12 or 15 m., and becomes deep and sluggish, its waters sometimes flowing backward during the annual rise of the Amazon. Its extreme length is about 1,200 m.
Steamers ascend to São Gabriel. The Negro was discovered by Favella in 1637, and soon after the Portuguese founded a settlement near the present site of Manaos.
A River Of South America, forming the boundary between the Argentine Republic and Patagonia. It rises between lat. 38° and 39° S., on the E. slope of the Chilian Andes, descending in four streams which unite and flow southward to lat. 40° 30', where it turns N. E. and flows over a series of rapids to about lon. 69° W. Here it receives the Neuquen from the north, after which it flows E. to lon. 66°, where it forms two islands, Rosas and Chole-chel, the latter, which is 210 m. from the sea, being 27 m. long by 3 m. broad. It then pursues a general S. E. course to its mouth in lat. 41° 2' S., lon. 62° 45' W. Navigation to Cholechel island is always unimpeded. The lands along the river are well adapted to grazing and agriculture, and many kinds of valuable timber abound. Carmen de Patagones, a flourishing town of 6,000 inhabitants, is situated on both banks about 20 m. from the sea. The river banks near this place are thickly settled by Scotch and English farmers; the most distant settlement is about 100 m. from the sea.
The value of the exports in 1873 was $430,000. The Negro was first explored by Villarmo, who after encountering great difficulties reached the base of the Andes. In 1873 the Argentine government sent up an exploring party in a steamer, but after many mishaps the expedition was abandoned.