ary
levels and to the enormous volume of water brought down by the Amazon,
especially in the flood season. As the outlet of the Tocantins is so
near to that of the Amazon, and their lower valleys are conterminous,
it is convenient to treat them as parts of the same hydrographic
basin.

In the extreme north-east corner of the republic where the Brazilian
Guiana plateau slopes toward the Atlantic there is a small area lying
outside the drainage basin of the Amazon. Its rivers flow easterly
into the Atlantic and drain a triangular-shaped area of the plateau
lying between the northern frontier and the southern and western
watersheds of the Araguary, whose extreme limits are about 0 deg. 30'
N. lat. and 53 deg. 50' W. long. The more important of these rivers
are the Araguary, Amapa, Calcoene, Cassipore and Oyapok. The Araguary
rises in the Tumuc-Humac mountains, in about 2 deg. 30' N. lat., 52
deg. 10' W. long., and follows a tortuous course south and north-east
to the Atlantic. Its largest tributary, the Amapary, rises still
farther west. Little is known of the country through which it flows,
and its channel is broken by rapids and waterfalls where it descends
to the coastal plain. The Amapa is a short river rising on the eastern
slopes of the same range and flowing across a low, wooded plain,
filled with lagoons. The Calcoene and Cassipore enter the Atlantic
farther north and have a north-east course across the same plain. All
these small rivers are described as auriferous and have attracted
attention for this reason. The Oyapok, or Vicente Pinzon, is the
best-known of the group and forms the boundary line between Brazil and
French Guiana under the arbitration award of 1900. It rises in about 2
deg. 05' N., 53 deg. 48' W., and flows easterly and north-easterly to
the Atlantic. Its course is less tortuous than that of the Araguary.

The rivers of the great Brazilian plateau which flow directly to the
Atlantic coast may be divided into two classes: those of its northward
slope which flow in a northerly and north-easterly direction to the
north-east coast of the republic, and those which drain its eastern
slope and flow to the sea in an easterly direction. The former reach
the coastal plain over long and gradual descents, and are navigable
for considerable distances. The latter descend from the plateau much
nearer the coast, and are in most cases navigab