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Amazon (River of South America)

a river of South America, the largest in the world, formed by a great number of sources which rise in the Andes; the two head branches being the Tunguragua or Marañon and the Ucayale, both rising in Peru, the former from Lake Lauricocha, in lat. 10° 29′ S., the latter formed by the Apurimac and Urubamba, the headwaters of which are between lat. 14° and 16° S.; general course N. of E.; length, including windings, between 3,000 and 4,000 miles; area of drainage basin, 2,300,000 square miles.

It enters the Atlantic under the equator by a mouth 200 miles wide divided into two principal and several smaller arms by the large island of Marajo, and a number of smaller islands. In its upper course, navigation is interrupted by rapids, but from its mouth upward for a distance of 3,300 miles (mostly in Brazil) there is no obstruction. It receives the water of about 200 tributaries. Northern tributaries: Santiago, Morona, Pastaça, Tigre, Napo, Putumayo, Japura, Ria Negro (the Cassiquiare connects this stream with the Orinoco), etc. Southern: Huallaga, Ucayale, Javari, Jutay, Jurua, Coary, Purus, Madeira, Tapajos, Xingu, etc.

At Tabatinga, where it enters Brazilian territory, the breadth is 1½ miles; below the mouth of the Madeira, it is 3 miles wide, and where there are islands often as much as 7; from the sea to the Rio Negro, 750 miles in a straight line, the depth is nowhere less than 30 fathoms; up to the junction of the Ucayale there is depth sufficient for the largest vessels. The Amazonian water system affords some 50,000 miles of river suitable for navigation. The singular phenomenon of the bore, or, as it is called on the Amazon, the pororoca, occurs at the mouth of the river at spring-tides on a grand scale. The river swarms with alligators, turtles, and a great variety of fish. It is a great highway of AMBASSADOR commerce. The Amazon was discovered by Yañez Pinçon in 1500, but the stream was not navigated by any European till 1540, when Francis Orellana descended it. He stated that he found on its banks a nation of armed women, and this circumstance gave the name to the river.