ICE-PERIOD IN AMERICA. 
91 
gravel-pit which has been partially worked 
compares with its banks. Look into any gravel- 
pit , a portion of which has already been carted 
away. At its bottom a number of larger 
stones and boulders are usually lying, too 
heavy for the cart, and therefore left upon the 
spot. Fragments of the same size and charac¬ 
ter, and equally numerous, will be seen pro¬ 
truding at various heights from the sides, 
where they are imbedded in the general mass 
of the drift. As soon as the work progresses 
a little further, and the finer materials are re¬ 
moved, these boulders will also drop out, and 
lie as thickly scattered over the surface of the 
ground as they now do in that portion of the 
bottom where the pit has been completely 
opened and the gravel removed. We shall see 
hereafter how these boulders, derived from the 
land-drift and scattered along the coast, may 
be distinguished from those cast ashore by 
icebergs. 
Notwithstanding the number of facts thus 
far collected respecting glacial phenomena in 
America, certainly forming in their combina¬ 
tion a very strong chain of evidence, the 
scientific world has, nevertheless, been slow to 
