Amazon, or Amazonas, a vast stream formed in equatorial S. America by the confluence of many rivers, draining an area of some two and a half millions of square miles. The name Amazon applies strictly to the lower reaches, and is derived, not from the fabulous female warriors of the Classics, but from a native word, amassona, "boat destroyer," as the spring tides produce a dangerous "bore" near the mouth. The middle portion is known to the Portuguese as Rio dos Solimoens, or Orellana, from the explorer who first navigated it. The upper waters are called Maranon, that river disputing with the Ucalayi, or Upurimac, the claim of being the head-stream. The former has its rise in Lake Lauricocha, Peru, lat. 10° 30' S, long. 76° 50' W., and flowing down between the Andes and the E. Cordilleras, turns E. at about the fifth degree of S. latitude, receives the Ucalayi, that starts from near Cuzco. and continues its course of some 3,000 miles to the sea. Many huge tributaries fall into the central stream, such as the Purus (2,000 miles), the Madeira (1,500 miles), the Tapajos, and the Xingu, from the S., and the Napo (530 miles), the Japura, or Caqueta (1,000 miles), the Negro (1,000 miles), and the Trombetas from the N. The mouth, which is traversed by the Equator, is 50 miles broad, but the delta with its islands extends for 200 miles. The influence of the tide (Prororoca) is felt 400 miles up the river, which is navigable for 2,000 miles. For most of its course it flows through dense forests (selras), rich in various kinds of timber, but especially in the caoutchouc, or indiarubber tree. The waters abound in turtle, fish, and caimans, or alligators. The estuary was discovered by Pinion in 1500, but Francis Orellana was the first to navigate the stream from the Rio Napo to the sea in 1540.