AMAZON. A river of South America, for merly called the Orellana, after a Spanish sol dier of that. name, who first explored it (Map: South America, I) 3). The name Amazon is said to be derived from an Indian word meaning "boat-destroyer,' from the dangerous action of the tidal waves at the river's mouth. The native name of the river from the mouth of the Negro to the junction of the Maranon and the Ucayali, is SolimiIens.
The head waters of the Amazon, the Maranon and the Ucayali rivers, rise in the central and northern Peruvian Andes, and after a northerly course parallel with these mountains unite in about long. 74° \V., and the united waters pursue an almost easterly course between lat. 5° S. and the equator to the Atlantic, which is reached in long. 50' \V., where this meridian intersects the equator. The Maranon. which rises in long. 76° 30' W. and lat. 10° 30' S., is properly the head stream of the Amazon, as it is furthest west; but the Ucayali is slightly the larger, and has its source farther south in the Andes in long. 72° W. and lat. 16° S. From long. 70° W., where the Amazon leaves Peru, its course is confined to Brazil.
The total length of the Amazon from the head waters of the Ucayali is about 3300 miles. It is between one and two miles wide where it enters Brazil, and gradually increases in breadth, en larging to a width of fifty miles at its main mouth; and where it enters the sea the distance across it, from headland to headland, is fulls' one hundred and fifty miles.
The total area drained by the Amazon is about two and one-half millions of square miles, a territory equal in extent to about 85 per cent. of that of the United States (exclusive of Alas ka), and embraces most of the South American continent west of long,. 50° W. and between lat. 3° N. and lat. 17' S., except a comparatively narrow strip along the Pacific coast, and a some what broader one on the Atlantic. The latitu dinal zone drained by the rivers from the north averages only 6° or 7° in width, while that on the south has a breadth of 13° or 14°.
The chief rivers flowing into the Amazon from the north are the NaPutumayo, Yapura, and Rio Negro. These rivers flow in a direction more
or less parallel with that of the Amazon, and thus they drain but a narrow longitudinal belt.
The chief affluents from the south (in addition to the Huallaga, an affluent of the Marafion, and the Ucayali) are the Javari, Jurmi, l'urus, Ma deira, Tapajos. and The Tocantins River practically belongs to this system of southern branches. being connected with the Amazon by an arm of that river, which cuts off the large island of 51araj5.
The basin of the Amazon lies almost wholly within the belt of remarkably uniform equatorial beat. so that there is an uninterrupted plant growth throughout the year. There is a mod erately heavy rainfall over the whole of the basin, except in the western part, where, east of the Andes, the rainfall is excessive; and higher up among the Andes, where it is deficient. The very heavy rains in the upper waters of the basin are responsible for the enormous amount of water supplied to the river, which makes it (and its western tributaries) navigable to such a great distance from its mouth. In most sec tions there is a rainy season from January to May, and a six months' dry season from June to December. In the Upper Amazon Valley the rainy season begins in November and continues until July, during which time the prevailing wind is northwest; but in the dry season the wind is chiefly from the southeast. The rainfall amounts to over 100 inches a year in this sec tion.
The alternation of the rainy and dry seasons produces corresponding periods of high and low water in the rivers. Even in the Marafion a rise of 30 feet occurs in the wet season, and through out the whole length of the Amazon during about half the year its waters are swollen and the adjoining low country inundated. These floods are not by any means of uniform magnitude. and at intervals of every few years abnormally high water occurs. The current of the Amazon averages about 27A miles per hour, but its veloci ty is much increased during the floods.