Orinoco
one of the great rivers of South America, has its origin on the slopes of the Sierra Parima, in the extreme S. E. of Venezuela; its exact sources were only discovered in 1886 by Chaffanjon. It flows at first W. by N., a mountain-stream, as far as lon. 67° W. A little below Esmeralda (lon. 65° 50' W.) it divides and sends off to the S. an arm, the Cassiquiare, which, after a course of 180 miles, enters the Rio Negro, a tributary of the Amazon. The other branch on reaching San Fernando (lon. 68° 10' and lat. 4° 2' N.) is met by the strong current of the Guaviare; the united stream then turns due N., and after passing over the magnificent cataracts of Maypures and Atures and picking up the Meta on the left, meets the Apure. Below the confluence with the Apure the Orinoco turns E. and traverses the llanos of Venezuela, its waters, with an average breadth of 4 miles, being augmented from the right by the Caura ORIOLE and the Caroni. About 120 miles from the Atlantic into which it rolls its milkwhite flood, its delta (8,500 square miles) begins. Of the numerous mouths which reach the ocean over 165 miles of coast line only seven are navigable. The waterway principally used by oceangoing vessels, which penetrate up to Ciudad Bolivar (Angostura), a distance of 245 miles, is the Boca de Navios, varying in width from 3% to 23 miles. The total length of the river is some 1,550 miles, of which 900, up to the cataracts of Atures, are navigable, besides a farther stretch of 500 miles above the cataracts of Maypures; area of drainage basin, 368,600 square miles.