794 



R OLLIN D. SA LI SB UR V 



amount of debris is shown in Fig. 20 along the line where 

 one of the upturned layers reaches the surface. Where the 

 debris in or between upturning layers is abundant, it is often 

 accumulated in large quantities on the surface of the ice along 

 the line of outcrop of the debris-bearing layer. This seems to 



Fro. 23. — Diagram showing the structure of a small glacier as seen from its ver- 

 tical end. 



necessitate the conclusion that the drift is carried up to the 

 surface by the upward movement of the upturned layers. 



If the debris in a layer of ice, or between any two layers, 

 were equal in amount at all points, it would appear at the sur- 

 face in a continuous line or belt of drift, equal at all points. 

 Its abundance would be dependent on the abundance of debris 

 in the layer concerned, and on the length of time it had been 

 bringing debris to the surface. In the course of time a very 

 considerable ridge of drift micrht accumulate at the surface. 



On the other hand, if the debris in or between layers of ice 

 be more abundant at some points than at others, the accumu- 

 lation on the surface would be in the form of an unequal, or 

 possibly even a discontinuous ridge, more massive where the 

 debris brought up is abundant, less massive where it is meager, 

 and absent where it fails altogether. The same general rela- 



P'lG. 24. — Diagrammatic representation of the structure of a large glacier as seen 

 from its vertical end. 



tions would hold concerning the upturning of the layers along 

 the lateral margins of a glacier as along its end. 



Phenomena illustrating these points were seen in many 

 localities, both on the ice-cap itself, and on differentiated 



