dents, of the most
recent cretaceous period.

Thus in its main features the Valley of the Amazons, like that of the
Mississippi, is a cretaceous basin. This resemblance suggests a further
comparison between the twin continents of North and South America. Not
only is their general form the same, but their framework as we may call
it, that is, the lay of their great mountain-chains and of their
table-lands, with the extensive intervening depressions, presents a
striking similarity. Indeed, a zooelogist, accustomed to trace a like
structure under variously modified animal forms, cannot but have his
homological studies recalled to his mind by the coincidence between
certain physical features in the northern and southern parts of the
Western hemisphere. And yet here, as throughout all nature, these
correspondences are combined with a distinctness of individualization,
which leaves its respective character not only to each continent as a
whole, but also to the different regions circumscribed within its
borders. In both, however, the highest mountain-chains, the Rocky
Mountains and Coast Range with their wide intervening table-land in
North America, and the chain of the Andes with its lesser plateaus in
South America, run along the western coast; both have a great eastern
promontory,--Newfoundland in the northern continent, and Cape St. Roque
in the southern;--and though the resemblance between the inland
elevations is perhaps less striking, yet the Canadian range, the White
Mountains, and the Alleghanies may very fairly be compared to the
table-lands of Guiana and Brazil, and the Serra do Mar. Similar
correspondences may be traced among the river systems. The Amazons and
the St. Lawrence, though so different in dimensions, remind us of each
other by their trend and geographical position; and while the one is fed
by the largest river system in the world, the other drains the most
extensive lake surfaces known to exist in immediate contiguity. The
Orinoco, with its bay, recalls Hudson's Bay and its many tributaries,
and the Rio Magdalena may be said to be the South American Mackenzie;
while the Rio de la Plata represents geographically our Mississippi, and
the Paraguay recalls the Missouri. The Parana may be compared to the
Ohio; the Pilcomayo, Vermejo, and Salado rivers, to the River Platte,
the Arkansas, and the Red River in the United States; while the rivers
farther south, emptying into the Gulf of Mexico, represent the riv