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34 Physical Geography of the Amazons Valley. |January, 
Atlantic, a narrow estuary bay or inland sea divided the northern 
part of the South American continent. The water in the eastern 
portion was clear and salt; heavy tides swept up the long sand- 
beaches and dashed against the cliffs of clay and conglomerate. 
In general the channel was clear, but here and there little rocky 
islands added to the picturesque beauty of the shores. On the 
northern side a number of blue mountains could be seen; spurs 
and outlyers of the table-land which stretched down from the 
Guiana chain. To the south a line of bluffs fronted the water, 
the northern edge of another great table-land. The Tapajós, 
Xingu, Trombetas and many smaller rivers flowed into the Ama- 
zonian sea through long branch estuaries or tidal bays. Some of 
these streams were muddy and tended to fill up their mouths; 
others preserved clear, deep channels. 
Just at its mouth, on the southern side, the great estuary met 
a lesser one, now the Lower Tocantins, and its outlet, the Para. 
The two bays were partly separated by a string of low sandy 
islands and reefs, like those now fronting the sounds along the 
` south-eastern coast of the United States. These reefs now form 
the ¢orrées along the southern and eastern side of Marajó. 
In the Amazonian bay the greatest extent of brackish or fresh 
water was towards the western end, where the water was shallow 
and much obstructed by islands. Islands and shallows owed their 
existence to, and were yearly being built up by, the Solimoens 
and Madeira, which here poured in their floods of muddy water. 
The mouths of these rivers formed two branches at the head of 
_ the bay; a third branch marked the outlet of the Negro, which, 
as it brought down little sediment, preserved a wide and clean 
channel. 
Then, as now, the trade-wind blew in freely from the Atlantic, 
and the climate was equable and moist. The plants and animals 
of the shores were probably similar to those which now inhabit 
the highland, but the great estuary formed an impassable barrier 
to many species, and the Guiana fauna and flora were more 
sharply divided from those of Brazil. The estuary itself was-in- 
habited principally by marine forms of fishes, Crustacea and Mol- 
lusca; only at the western end, where the hae rivers emptied 
in, brackish-water forms prevailed. 
© Gradually the alluvial land at the head of the bay extended 
eastward, filling up the estuary with islands, As this eastward 
