AMAZON, 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 Maranon 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 S.; general course N. of E.; length, including wind ings, 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 re ceives the water of about 200 tributaries. Northern tributaries: Santiago, Morona, Pastaga, Tigre, Napo, Putumayo, Ja pura, Ria Negro (the Cassiquiare con nects this stream with the Orinoco), etc. Southern: Huallaga, Ucayale, Javari, Jutay, Jurua, Coary, Purus, Madeira, Tapajos, Xingu, etc.
At Tabatinga, where it enters Brazil ian territory, the breadth is Ph 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 fath oms; 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 suit able for navigation. The singular phe nomenon 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 va riety of fish. It is a great highway of commerce. The Amazon was discovered by Yafiez Pingon 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 cir cumstance gave the name to the river.