MUSEUM OF COMPARATIVE ZOOLOGY. 225 
explained. It seems likely to solve the enigmas presented by the very 
sudden variations of a temporary nature in the position of the ice front. 
It appears to explain the way in which the ice journeyed for great dis- 
tances over surfaces of slight inclination in the direction of glacial flow, 
or which sloped towards the centre whence the glacial movement radi- 
ated, for it limits the friction to the probably narrow zone where the 
glacier rested upon the earth. The hypothesis will clearly account for 
the small amount of erosion which is often traceable in the regions which 
lay in the central parts of the glaciated district, and therefore beneath 
the deeper parts of the accumulation; for in that part of the field 
pressure melting was probably first established, and must have continued 
for the longest time. It furthermore bids fair to explain the very puz- 
zling phenomena exhibited by drumlins or lenticular hills, by showing a 
way in which, through the thickening of the ice, the rocky matter which 
it had taken up from the bed rock might be rapidly deposited in the 
form in which we now find it. 
The only justification for presenting such highly speculative consid- 
erations as are offered in this writing is that they may serve to explain 
phenomena which, in the present state of our knowledge, cannot be 
otherwise rationalized. It seems to me, therefore, that this view may 
fairly be submitted to debate. I am by no means sure that it can 
withstand the criticism which it merits, but it seems to me worthy of 
inquiry on the part of those who are well trained in the interpretation 
of physical phenomena. 
