CHAPTER XIII.

PHYSICAL HISTORY OF THE AMAZONS.

Drift about Rio de Janeiro.—Decomposition of underlying Rock.—Different Aspect of Glacial Phenomena in different Continents.—Fertility of the Drift.—Geological Observations of Messrs. Hartt and St. John.—Correspondence of Deposits along the Coast with those of Rio and those of the Valley of the Amazons.—Primitive Formation of the Valley.—First known Chapter of its History.—Cretaceous Fossil Fishes.—Former Extent of the South-American Coast.—Cretaceous Fossils from the Rio Purus.—Comparison between North and South America.—Geological Formations along the Banks of the Amazons.—Fossil Leaves.—Clays and Sandstones.—Hills of Almeyrim.—Monte Alégre.—Situation and Scenery.—Serra of Ereré.—Comparison with Swiss Scenery.—Boulders of Ereré.—Ancient Thickness of Amazonian Deposits.—Difference between Drift of the Amazons and that of Rio.—Inferences drawn from the present Condition of the Deposits.—Immense Extent of Sandstone Formation.—Nature and Origin of these Deposits.—Referred to the Ice-Period.—Absence of Glacial Marks.—Glacial Evidence of another Kind.—Changes in the Outline of the South-American Coast.—Souré.—Igarapé Grande.—Vigia.—Bay of Braganza.—Anticipation. 397–441