The universal geography : earth and its inhabitants

ElVEES OP AMAZONIA. 99
doubt ttat at some remote period the whole region of plains and terraces formed
the bed of a vast lake, or of several lakes constituting an American Mediterranean
larger than the Canadian lake system, larger even than the Mediterranean of the
Old World. In the Pebas cliffs on the Peruvian Maraiion, Orton discovered,
embedded in layers of many-coloured clays, a mass of marine shells comprising no
less than 17 extinct species dating from the close of the Tertiary epoch.
At that time the Maranon, issuing from the Manseriche gorges, entered the
inland sea through a delta, which, gradually advancing eastwards, at last filled
the whole plain. Possibly the fluvial waters were then discharged north-eastwards
in the direction of the Caribbean Sea through the depression at present traversed
Fig. 33.
—
Amazonian Depeessiou and Outer Zone of the Catasacts.
Scale 1 : 36,000,000.
'^x.:^
West op Gneenwich
"Zone of the Amazons Affluents above the Falls,
1,250 Miles,
by the Rio Negro, the Cassiquiare, and the Orinoco. At least the marine shells
of the Upper Amazons resemble the types characteristic of the West Indian
waters. In that case, the bluffs of Monte Alegre, the Santarem heights, and
the other hills approaching the banks of the Amazons at the Obidos narrows,
should be regarded as the remains of the ridge or dyke which formerly closed the
basin of the inland sea and of the lakes ascending in terraces up the slopes of the
Andes to Lake Titicaca.
The Amazoxi.\n Floods.
As regular in its periodical changes as the Nile itself, the Amazons rises and
falls with the alternating seasons by a succession of " ebbs " and " flows
{enchente and vasante), in which the inhabitants recognise a sort of tidal move'
h2
48-
"