the Hintereis Glacier. 



167 



found at numerous points on the surface at section Y. It 

 will be seen that not only is there a lower mean velocity on 

 the deepest side, but that near the centre there is a distinct 

 lowering of the actual velocity curve between the deepest 

 portion of the glacier and its centre. That this is not an 

 accidental local feature is shown by fig. 10, which shows a 



Fig. 10. 



Lines of equal velocity on the Hintereis Glacier. 

 Velocities in metres per annum. 



line of low velocity near the centre extending throughout 

 the glacier tongue. In drawing their equal velocity curves, 

 Blum eke and Hess did not give any weight to certain appa- 

 rently irregular velocity determinations near the middle. 

 In figs. 9 and 10 we have drawn the equal velocity curves as 

 strictly as possible in accordance with the velocities observed 

 by Blilmcke and Hess. 



The reason why the summer velocity curve b (fig. 9) does 

 not agree more nearly with the theoretical curve <?, is no 

 doubt due to the fact that the ice at the shallow sides is 

 dragged along by the rapidly moving central portion, and 

 also because the depth of the ice at the shallow side is greater 

 than in the case of Parr's curve. The great viscosity of the 

 ice has also resulted in the velocities being more even over 

 the central portion of the glacier. We have previously 

 suggested that the reason why the greatest velocity is over 

 the shallow side is probably partly due to the curve of the 

 valley. It now seems that it is mainly due to the varying 

 amount of slip across the glacier-bed. 



