2o8 TJie American Geologist. October, i899 
ci])itation is again faulty, for the massive Laurentide g^lacier, al- 
tlu)Ui;h reaching to the mouth of the Ohio, was hmited by the 
Missouri, which for many hundred miles flowed against its 
base, and but rarely yielded more than a few scores of miles to 
its mighty advance. On the north the great glacial dispersion 
from the belt of maximum precipitation flowed towards it, and 
forced its way around the eastern border of the unglaciated 
area to the mouth of the Ohio in Lat. 37° N., or 8° nearer to 
the equator than to the pole. We must therefore confront the 
problem of its escape in its broad, bold form. Why should warm 
rain have fallen on the unglaciated area, whilst snow accumu- 
lated to enormous depths all around it except on the lava beds 
to the w-est, and flowed towards this area from the north. 
Assumptions of unequal rainfall, and unequal upheavals 
have been appealed to as causes for the escape of this area from 
glaciation. 
Unequal rainfalls could only have affected the depth of gla- 
ciation, but could not cause an escape, and could in no way 
have checked the flow of the great continental or Laurentide 
glacier. 
To have remained at a lower level whilst adjacent areas 
were sufftciently upheaved to cause glaciation would have ac- 
celerated rather than retarded glacial flow from the northeast; 
consequently, these hypotheses complicate rather than explain 
the phenomeha. 
The presence of the great chain of glacial material extend- 
ing from the intersection of the 49th parallel and the 113th 
meridian, southeasterly to the intersection of the 38th parallel 
with the 89th meridian must be accounted for by showing that 
there were positive conditions causing the precipitation upon 
the unglaciated area to be rain instead of snow, and stopping 
or warding off the glacial flow from the north. 
We have in the vast heat escaping from the Columbia lava 
plain, an energy starting before and continuing long after the 
Ice age had departed from this latitude. 
The influence of this energy must have locally affected 
climatic conditions at all periods of intervening time, and these 
effects must be recorded in that area most exposed to their in- 
fluence, namely, to the east, since this is the direction of at- 
mospheric circulation. 
