74 G/ar/'ers and G/acial Badimtfs — Claypoh. 
could be found on the great plain of the Amazon at the earth's 
very equator, a statement which seems to carry as a consequence 
the glaciation of almost all the dry land at one time or another. 
Dr. James Croll, of the Scottish Geological Survey, carried 
away with the belief that he had found an astronomical cause 
for the cold, has extended the time of the action of ice over 
160,000 years, sees in imagination a vast ice-cap on either pole 
alternately many thousand feet in thickness and follows M. 
Adht5mar in trying to compute the efEect of such »n ice-cap in 
changing the centre of gravity of the earth. 
Professor Ramsay in a well known ])aper has advocated the 
opinion that the eroding power of a glacier was so great that it 
was able to excavate its bed in certain spots and thus to form 
basins or bo.it-shaped hollows. To this cause he attributed the 
existence of many lakes in tlie temperate regions of the globe 
and the great depth of m iny of the fiords along some of our 
northern coasts. 
All the above mentioned writers have pushed the effects and 
the })0w-er of glacier-ice to an extreme in oue direction, but on 
the other hand there are not lacking geologists who would con- 
fine this power within very much narrower limits. Some of 
these go so far as to doubt the abilit}^ of a glacier to erode at 
all and have even affirmed that the ice is a positive protection 
to the rocks on which it lies. When considering the phenomena 
of the ice-age they deny altogether the existence of a conti- 
nental ice-slieet, and attribute all the observed phenomena to 
the action of local glaciers flowing off spots of elevated ground 
in the glaciated region, and aided largely by floating ice. 
This conflict of opinion is a necessary stage in the investiga- 
tion, and time and study alone can show exactly where the 
truth lies. As in many similar cases, it will in all probability 
be found between the two extremes. 
The writer has on more than one occasion opposed the views 
of those glacialists who maintain an excessive abrading power 
for glacier-ice.* It is difiicult to see in the facts brought for- 
ward any justification of the often expressed opinion that pro- 
found modifications of the surface have been wrought by this 
agent. Even admitting that valleys can be deepened unequally 
*See the Canadian Naturalist for 1879, and the Proceedings of the Amer- 
ican Association for the Advancement of Science for 1881. 
