84 
ICE-PERIOD IN AMERICA. 
overtopped the rocky inequalities of the land, 
and that the detached fragments remaining 
beneath the icy covering underwent the same 
action from friction and pressure to which the 
whole mass of drift was subjected. The dis¬ 
tribution of the few angular boulders scattered 
over the country no doubt began when some of 
the higher portions of the land had emerged 
from the mass of snow and ice; and they are 
most frequent in New England, where the 
mountain-elevation is greatest. 
The mineralogical character of the loose ma¬ 
terials forming the American drift leaves no 
doubt that the whole movement, with the ex¬ 
ception of a few local modifications easily ac¬ 
counted for by the lay of the land, was from 
north to south, all the fragments not belong¬ 
ing to the localities where they occur being 
readily traced to rocks in situ to the north of 
their present resting-places. The farther one 
journeys from their origin, the more extraor¬ 
dinary does the presence of these boulders 
become. It strikes one strangely to find even 
in New England fragments of rock from the 
shores of Lake Superior; but it is still more 
impressive to meet with masses of northern 
