486 ELEMENTARY GEOLOGY 
broken up the ice of Arctic regions, and transported materials 
from northern points by means of the icebergs thus derived. 
This theory failed to account for many of the phenomena, and 
was very unsatisfactory, even before the glacial theory was sug- 
gested. Louis Agassiz, studying the valleys of the Swiss Alps, 
saw glacial deposits and signs of glacial action below the termi- 
nus of the Alpine glaciers (p. 211). Upon this evidence he con- 
cluded that at one time glaciers had extended further down the 
valleys than at present. Coming to America he saw that the 
soils and surface feature of New England resembled those in 
the Alpine valleys, which had once been glaciated. Upon this 
evidence he proposed the glacial theory, now so universally 
accepted. 
This explanation alone, of those that have been suggested, will 
account for the phenomena. There are many things connected 
with the deposits which cannot possibly be explained by the 
effects of water, the most notable of which is the fact that the 
terminus of the glacial deposits is a purely arbitrary belt, extend- 
ing westward across the country, and not governed by irregulari- 
ties of topography. Why should the ocean floods stop at such 
a belt, sweeping over the country on the northern side and pro- 
ducing no effect to the south ? 
Conclusion. The Glacial period influenced this coun- 
try so recently that its effects are very noticeable. The 
ice sheet has withdrawn from Labrador even more re- 
cently, and indeed, the surface of some of the rocks of 
that peninsula have been so ttle changed since the 
Glacial period, that the striz and grooves formed by 
the ice have not been decayed, even from the surface 
of rocks that are exposed to the air. In Greenland the 
glacier still remains, but it is withdrawing at a notably 
