118 GLACIAL PHENOMENA IN MAINE. 
and even the tops of the mountains attest, by 
their rounded and polished summits, that they 
formed no obstacle to its advance. It has 
been assumed by some geologists, and espe¬ 
cially by Sir Charles Lyell, that the ice-period 
was initiated by the spread of local glaciers 
from special centres. The particular charac¬ 
ter of the more extensive glacial phenomena 
satisfies me, on the contrary, that they must 
have preceded in course of time all mere local 
glaciers, and that the latter are but the rem¬ 
nants of the great ice-sheet lingering longer in 
higher and more protected valleys. From the 
evidence we have of its thickness and extent, 
such a mass of ice advancing over the country 
would have swept away all evidences of local 
glaciers, all morainic accumulations previously 
formed. I therefore infer that the local phe¬ 
nomena were the latest in time, and conse¬ 
quent upon the shrinking of the larger con¬ 
tinuous ice-sheet. It is mv belief that the 
V 
ice-period set in, as our winters now do,— 
only upon a gigantic scale, — by snow-falls, 
and that it faded as do our winters, leaving 
local patches of ice wherever the temperature 
was favorable to their preservation. 
