262 E. C. ANDREWS. 



allowance is made in their discussions for the fact that the 

 present day glaciers are the weaker, less plastic, and 

 the dirtier representatives of glaciers which produced the 

 channels in which they in turn do little but stagnate. [A 

 consideration of such conditions might result in ascertain- 

 ing that the textural unit of the old heavy glacier varied 

 considerably from that of the relatively stagnant modern 

 glacier.] 



They find in glaciers, all other things being equal, some- 

 thing akin to the following 1 : — 



1. The movement of the ice mass increases with increased 



depth. 



2. Movement is greater on steep slopes. 



3. Constrictions in channels give increased speed. 



4. Enlargement of the channel cross-sections results in 



decrease of speed. 



5. The ice flow is fastest in the neighbourhood of the 



centre, slower at the sides and at the base. 



6. Ice flows round corners. 



7. Ice is subject to other differential motions, often 



resulting in shearing. 



The significance of these points in order appears to be as 

 follows : — 



1. With increasing pressure the textural units of the 

 glacier ice move more freely on each other, that is, the 

 flowage rate is increased. 



1 " Ic (the glacier) works its way down the valley in a manner which 

 in the aggregate, is similar to the movement of a stiff liquid. The like- 

 ness to a river extends to many details. Not only does the centre move 

 faster than the sides, and the upper part faster than the bottom, as in 

 the case of streams, but the movement is more rapid in constricted por- 

 tions of the valley and slower in the broader parts " (Chamberlin and 

 Salisbury, Geology, Vol. i, p. 236). Such a statement of motion is practi- 

 cally all that is needed to establish the conclusions arrived at in these 

 papers. 



