PHYSICAL HISTORY OF THE AMAZONS. 439 
that it connected the shoals of Newfoundland with the 
continent ; that Nantucket, Martha's Vineyard, and Long 
Island made part of the main-land ; that, in like manner 
Nova Scotia, including Sable Island, was united to the 
southern shore of New Brunswick and Maine, and that 
the same sheet of drift extended thence to Cape Cod, 
and stretched southward as far as Cape Hatteras ; in 
short, that the line of shallow soundings along the whole 
coast of the United States marks the former extent of 
glacial drift. The ocean has gradually eaten its way into 
this deposit, and given its present outlines to the conti- 
nent. These denudations of the sea no doubt began as 
soon as the breaking up of the ice exposed the drift to 
its invasion ; in other words, at a time when colossal 
glaciers still poured forth their load of ice into the At- 
lantic, and fleets of icebergs, far larger and more numer- 
ous than those now floated off from the Arctic seas, 
were launched from the northeastern shore of the United 
States. Many such masses must have stranded along the 
shore, and have left various signs of their presence. In 
fact, the glacial phenomena of the United States and 
elsewhere are due to two distinct periods : the first of 
these was the glacial epoch proper, when the ice was a 
solid sheet ; while to the second belongs the breaking up 
of this epoch, with the gradual disintegration and disper- 
sion of the ice. We talk of the theory of glaciers and 
the theory of icebergs in reference to these phenomena, 
as if they were exclusively due to one or the other, and 
whoever accepted the former must reject the latter, and 
vice versa. When geologists have combined these now 
discordant elements, and consider these two periods as 
consecutive, part of the phenomena being due to the 
