Ea 
30 Physical Geography of the Amazons Valley. (January, 
are seen near the river in the table-topped hills of Almeyrim and 
Velha Pobre, each more than 1500 feet high. This plain may be 
regarded as a great terrace, abutting abruptly against the high 
peaks of the Guiana chain,and cut down as sharply near the 
Amazons to a second terrace which forms a low region between 
the table-topped hills and the river flood-plain. Sometimes an 
intermediate terrace may be distinguished, as at Monte Alegre 
and Prainha; outlying and much denuded portions of the upper 
terrace are seen in the rugged hills of Ereré and Tajury, west 
and north of Monte Alegre. 
The southern side of the valley, from the Madeira eastward, 
seems to be everywhere a low table-land, which rises gradually 
or by terraces to the elevated plains of Central Brazil. Near the 
Amazons and its tributaries it is abruptly cut down, forming 
bluffs three or four hundred feet high. A line of these bluffs ex- 
tends, with slight interruptions, from the Tocantins almost to the 
Madeira. Generally the bluffs form the southern edge of the 
Amazonian flood-plain, but in some places, as near Santarem, 
they are separated from it by strips of low land answering to the 
lower terrace on the northern side. The bluffs themselves may 
correspond to the intermediate terrace of Monte Alegre and 
Prainha. 
Between these northern and southern terraces, crossing the 
country from W.S.W. to E.N.E,, is a low, flat, perfectly level ex- 
panse, very irregular in outline and varying in width from fifteen 
to forty miles; at the Atlantic end only it spreads out like a fun- 
nel, occupying perhaps a hundred miles of coast. The yellow 
Amazons winds through this flood-plain, rarely touching the bor-* 
ders, now pouring through the narrow pass at Obidos, now ex- 
panded into sea-like reaches, again broken into two or three por- 
tions, separated by great islands. Everywhere the alluvial land 
is dotted with shallow lakes and seamed with channels—goodly’ 
rivers which hardly appear on the maps. Constant changes are 
taking place in this network; new islands and shallows are 
formed almost every year, and old ones are altered or washed 
away. I know of one island, three miles long, which disappeared 
completely in less than ten years; the river steamboats now pass 
directly over its site. 
On the Lower Amazons the islands and river-borders of the 
flood-plain are called varzeas, though Properly the term is applied 
