36 REVIEWS. 
sheet of clay and sand, when the rocks beneath are found to be 
grooved and polished, when the coast clays are found to contain 
glacial, arctic shells, and the transported boulders described by 
the authors are more numerous and unmistakably of ice origin. 
But the grand objection to the theory of the former existence of 
a continental glacier in tropical America, is the unbroken conti- 
nuity of tropical life since the close of the Tertiary period. While 
_the coral reefs of Florida were slowly rising above the waves of a 
heated, equatorial sea, the waters of New York bay, and Massa- 
chusetts bay were the home of the walrus, the great auk, and the 
arctic seals, and the ocean depths were peopled with a truly arctic 
assemblage of animals and plants. At Charleston, however, the 
seas, as indicated by the fossils of the post-tertiary period, were 
not much colder than now, and the Floridian fauna was as tropical 
as now. Meanwhile in Brazil flourished giant sloths, and other 
quadrupeds, which roamed over the Pampas, while their ally, the 
Hairy Mammoth, braved the snows of the northern woods and 
prairies. It would be difficult for us to imagine that the valley of 
the Amazon differed so greatly in its climate at that time, and not 
leave behind the usual marks (at least more than Agassiz and 
Hartt here indicate) of an ice period. The deposit of Tertiary 
shells at Pebas, about two thousand miles from the mouth of the 
Amazon, described by Conrad, and discovered by Professor Orton 
in Professor Agassiz’s Amazonian ‘ drift,” must effectually settle 
the question of the Amazonian beds at least. There may have 
been loeal glaciers on the Organ mountains about Rio. 
An interesting sketch of the Botocudos, a very degraded In- 
dian tribe, without a belief in a supreme God, is appended to Mr. 
Hartt’s narrative, of which we would not take leave without refer- 
ring to its value to the colonist and capitalist, from its full 
accounts of gold and diamond mines, and other natural produc- 
tions. The Brazilians will remain under lasting obligation to the 
author, who has given them a most compact and accurate account 
of the geology and mineral wealth of their magnificent country. 
Since its publication, Professor Hartt has led a new expedition to 
Brazil, accompanied by a large corps of assistants, to make fresh 
explorations about the mouth of the Amazon. The Emperor of 
Brazil, who has already done so much towards developing the 
natural resourees of his empire, might do much for its advance- 
ment by instituting a geological survey under the direction of one 
so familiar with the subject as our author. 
