ElVERS OF AMAZONIA. 97 



route has been followed by all recent explorers, such as D'Orbigny, Church, and 

 Keller-Leuzinger. The hydrogi-aphic chart prepared in 1878 to a scale of y'ô'uwwô^ 

 is based on the careful surveys of Selfridge. 



From the Guajara Guassu Falls on the Maraore to the last cataracts of Santo 

 Antonio the total incline scarcely exceeds 200 feet in a distance of about 240 miles. 

 The highest cascade, that of E-ibeirao, some 12 miles below the Beni, has a drop 

 of 40 feet, the 45 others varying from 30 feet to a few inches ; but the 

 whole system presents so many difficulties to the navigation that the native boat- 

 men take from two to three months to make the ascent from the lower to the 

 upper reaches. 



Below these obstructions the Madeira flows mainly north-east parallel to the 

 Purus with a uniform, though somewhat rapid current, which is nowhere less than 

 16 feet deep at low water, and in some places exceeds 500 feet, with a total mean 

 discharge of no less than 1,400,000 cubic feet per second. It enters the Amazons 

 through numerous island- studded channels, and throws off one branch, the 

 Parana Mirim ("Little River") which joins the main stream about 190 miles 

 lower down, thus enclosing the vast island of Tupinambaramas. 



The Trombetas, Tapajoz, and Xingu. 



Beyond the Madeira confluence the largest affluent on the north side is the 

 Trombetas, which collects the surface waters of the savannas, and on its course 

 to the Amazons develops a ramifying lake due to the alluvial matter deposited 

 by the mainstream about the confluence. Higher up similar phenomena aro 

 presented by the Urubu, Uatuma, Yamunda (Neamunda or Cumery), all carefully 

 explored by Barbosa Rodrigues. Farther down the Paru and the Jary, which 

 descend from the Tumuc-Humac Mountains, have a more regular course, freer 

 from stagnant waters, but obstructed at intervals by rapids and even by cascades. 

 Crevaux descended the Jary and the Paru in 1877-79 at the risk of his life. 



On the south side the Amazons is joined below the Madeira by the Tapajoz, 

 so called from the Tapajocos Indians, who have been completely exterminated by 

 the Portuguese. Its two headstreams, the Arinos and the Juruena, rise in 

 Matto Grosso, near the sources of the Paraguay, and after their junction the 

 Tapajoz flows parallel with the Madeira north-eastwards to the scarp of the 

 plateau. Here it is obstructed by a series of 16 cataracts, beyond which it 

 forms a broad navigable watercourse, flowing between wooded banks for 300 

 miles to a point where the navigation is again interrupted by the Sal to Augusto, 

 the only cascade which is impassable at all seasons. 



For the rest of its course of 220 miles the Tupajoz forms a sluggish stream 

 nearly as dark as the Rio îs"egro, which gradually expands into a broad lagoon 

 with scarcely perceptible current. Like that of the Trombetas, Lake Yillafranca, 

 as this flooded depression is called, owes its existence to the sedimentary matter 

 deposited by the Amazons at the confluence. The Tapajoz presents the shortest 

 natural route between the Amazons and Plate estuaries. 



The Xingu, last great affluent of the Amazons proper, rises on the same 



