The universal geography : earth and its inhabitants

EIVEES OF AMAZONIA. 97
route has been followed by all recent explorers, sucb as D'Orbigny, Church, and
Keller-Leuzingcr. The hydrograi^hic chart prepared in 1878 to a scale of TinrVo"o"
is based on the careful surveys of Selfridge.
From the Guajara Guassu Falls on the Mamore 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 Ribeirao, 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 boatmen
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 ramifj'ing lake due to the alluvial matter deposited
by the mainstream about the confluence. Higher uji similar phenomena are
presented by the TJrubu, TJatuma, 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 Salto Augusto,
the only cascade which is impassable at all seasons.
For the rest of its course of 220 miles the Tapajoz forms a sluggish stream
nearly as dark as the Rio Negro, which gradually expands into a broad lagoon
with scarcely perceptible current. Like that of the Trombetas, Lake VHlafranca,
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
VOL. XIX. H