166 Messrs. K-M. Deeley and P. H. Parr on 



more and more pronounced as the)' advance. A thickening 

 o£ the upper portion also gives rise to an increased velocity 

 by thrust, and such pulses are known as Druckwellen, which 

 travel down the glacier from 20 to 150 times as fast as the 

 ice itself. Bliimcke and Finsterwalder, in the case of the 

 velocity curves of the Hintereis Glacier, shown in fig. 8, 

 state that they did not notice waves which could be regarded 

 as Schwellungswellen, phenomena which might render any 

 measurements of velocity and slope near them somewhat 

 misleading if used for the calculation of viscosity. 



In fig. 9, a is the mean annual velocity curve across the 



Fig. 9. 



glacier, b the summer velocity, and c the calculated velocity 

 curve on the assumption that the central surface-velocity 

 due to differential flow is 21 metres per annum and the slip 

 21 metres per annum. The curve c was obtained by com- 

 bining the curves b (fig. 3) and d (fig. 4). It is interesting 

 to note that both the theoretical and the actual curves show 

 a smaller velocity over the deep side of the glacier than they 

 do over the shallow side. The curve d (fig. 9) is Parr's curve 

 and e the actual section of the Hintereis Glacier. In our 

 former paper the velocity curve was plotted in accordance 

 with the equal velocity curves drawn by Bliimcke and Hess. 

 In fig. 9 the small circles represent the actual velocities 



