ICE-PERIOD IN AMERICA. 
79 
face of the land in the eastern half of the 
continent, from the Atlantic shores to the 
States west of the Mississippi, and from the 
Arctic Sea to the latitude of the Ohio, in its 
middle course, while within the range of the 
Alleghanies they stretch as far south as Geor¬ 
gia and Alabama. In no other region where 
these traces have been observed do they extend 
over such wide tracts of country in unbroken 
continuity, this being of course owing to the 
level character of the land itself. 
The continent of North America, east of the 
Rocky Mountains, is, indeed, an immense uni¬ 
form plain, intersected from east to west only 
by the ranges of low hills running in the 
direction of the St. Lawrence and the Cana- 
dian lakes, and from northeast to southwest 
by the Alleghany range stretching from Ala¬ 
bama to New England, where it trends towards 
the Canadian Hills in the ridges known as 
the Green and White Mountains. This coast- 
range has a short slope towards the Atlantic, 
and a long one in the direction of the great 
Mississippi Valley. With the exception of 
some higher points of the Alleghany range, 
the surface of this whole plain is glacier-worn 
