The eastern margin of the plateau is near the Atlantic where it breaks off suddenly with an average height of 2600-3200 feet. This plateau is the best part of the country, the Atlantic slope heavily wooded, the more gradual west slope with many grass covered plains. A fertile soil, rich forests, and regular rainfall make this a favored region. Farther north than Minas Geraes, the section has less rain, is thinly wooded in places, with large areas suited to grazing but subject to drought. The plateau extends across Brazil north of Paraguay abruptly breaking down from a height of 2600-3000 feet towards the Paraná and Paraguay Basins. It has a gradual slope towards the Amazon, the parts excavated by the rivers having lowland characteristics. THE AMAZON BASIN The section of the Amazon Basin is indeed immense. The whole drainage area with that of the Tocantins, generally included though not strictly a component part, spreads over 2,700,000 square miles, much of it as we have already seen outside of Brazil, and occupying two-fifths of South America. This area is greater than the basins of the Mississippi, Missouri, Danube, and Nile, all combined. The course of one tributary to the sea is 3200 miles. Of the 55 largest rivers in the world, it is said that 33 are mainly if not wholly in Brazil. Twenty-seven thousand miles of navigable rivers are found in the country, the greater part connected with the Amazon, which is itself navigable for ocean steamers to Iquitos, Peru, a distance of 2300 miles, and 486 miles farther for vessels of 14 feet draft. The true mouth of the Amazon is west and north of the Marajos Island which is greater in area than Holland or Belgium, while the Pará River at the south and east is the mouth of the Tocantins. This, however, is the usual entrance for Amazon steamers even when they do not wish to call at Pará, for this river is connected by natural channels among islands with the greater stream, and the northern entrance has too strong a current to be desirable for navigation. As a matter of convenience the Tocantins is generally included with the Amazon in descriptions. The depth of the estuary is 90-900 feet, averaging 150. =The Tocantins River= is a great artery of Brazil flowing from south to north a distance of 1600 miles, with a west affluent, the Araguaya, almost its equal in size and 1000 miles long above the union. Both rivers receive many tributaries. The flat broad valleys are overlooked by steep bluffs. The cataracts and rapids which occur on nearly all of the rivers as they come down from the plateau greatly interfere with navigation, but in their lower courses many are navigable for hundreds of miles, the Tocantins for 130.