ICO 



Messrs. R. M. Deelev and P. H. P 



arr on 



If the theory propounded be sound, then the slip is 

 proportional to the shear stress on the glacier-bed. 



The theory also makes the velocity of the slip proportional 

 to the thickness of the glacier, whereas the surface speed, 

 due to the differential movement of the ice resulting from its 

 viscosity, is proportional to the square o£ the thickness of 

 the glacier, and the slip and viscous flow are about equal 

 when the shear stress on the glacier bottom is about 1 kg. 

 per cm.-. 



Measurement of slip. — After making the experiments on 

 the downward movement, under load, of a glass bar into ice, 

 the apparatus was altered so as to enable the slip of a piece 

 of ice on a stone surface to be measured. 



Fisr. 6. 



The stone was brought to a smooth level surface by 

 grinding. It was then scratched diagonally with the edge 

 of a second-cut file. The stone upon which the ice rested 

 was fixed in the wooden bar a (fig. 6). Three Y-shaped 

 grooves were cut with a file longitudinally on the stone, to 



