228 
PHYSICAL HISTORY OF THE 
restored, when it was found that both elements 
had been equally at work in forming the solid 
crust of the globe. To the stranded icebergs 
alluded to above, I have no doubt, is to be 
referred the origin of the many lakes without 
outlet existing all over the sandy tract along 
our coast of which Cape Cod forms a part. 
Not only the formation of these lakes, but also 
that of our salt-marshes and cranberry-fields, 
I believe to be connected with the waning of 
the ice-period. 
I hope at some future time to publish in 
detail, with the appropriate maps and illus¬ 
trations, my observations on our coast changes, 
and upon other phenomena connected with the 
close of the glacial epoch in the United States. 
It is reversing the natural order of things to 
give results without the investigations which 
have led to them ; and I should not have intro- 
duced the subject here, except to show that the 
fresh-water denudations and the oceanic en¬ 
croachments which have formed the Amazo¬ 
nian Valley, with its river system, are not 
isolated facts, but that the process has been 
the same in both continents. The extraordi¬ 
nary continuity and uniformity of the Ama- 
