222 
PHYSICAL HISTORY OF THE 
know thus far of their geological character 
goes to prove that this was actually the case. 
Such an extensive oceanic denudation must 
have carried away not only the gigantic glacial 
moraine here assumed to have closed the 
mouth of the Amazonian basin, but the very 
ground on which it stood. 
During the last four or five years, I have 
been engaged in a series of investigations, in 
the United States, upon the subject of the 
denudations connected with the close of the 
glacial period there, and the encroachments of 
the ocean upon the drift deposits along the 
Atlantic coast. Had these investigations been 
published in detail, with the necessary maps, 
it would have been far easier for me to explain 
the facts I have lately observed in the Ama¬ 
zonian Valley, to connect them with facts 
of a like character on the continent of North 
America, and to show how remarkably they 
correspond with facts accomplished during the 
same period in other parts of the world. While 
the glacial epoch itself has been very exten¬ 
sively studied in the last half-century, little 
attention has been paid to the results con¬ 
nected with the breaking up of the geological 
