MUSEUxM OF COMPARATIVE ZOOLOGY. 225 



explained. It seems likely to solve the euigtnus 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 gi-eat 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 nan'ow zone where the 

 glacier rested upon the earth. The hypothesis will clearly account for 

 tlie 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 

 in(piiry on the part of those who are well trained in the interpretation 

 of physical phenomena. 



