GLACIAL STUDIES IN GREENLAND. 



779 



taken place. But, for the most part, this apparent outthrust was 

 seemingly due to differential melting. 



Little needs to be added to the photographic illustrations to 

 make clear the nature and disposition of the terminal material. 

 It is aggregated immediately at and under the ice edge. On its 

 external face it is usually heaped about as steeply as the material 

 will lie. It is composed of rocky material mixed with clay. 

 Gravel is occasionally present, but is only a very minor constit- 

 uent. The mixture of rock and clay is indiscriminate and 

 varying. It differs little from the well-known stony till produced 



Fig. 9. Illustration of the bruising, de-angulation and partial rounding of the 

 bowlders of the terminal moraine. 



by Alpine glaciers, where the rock element is abundant and the 

 grindings take the form of clay rather than sand, as is the case 

 with most basic igneous rocks. The bowlders are commonly 

 bruised and de-angulated in various degrees. They are some- 

 times, but not usually, well rounded. In a moderate degree 

 they are polished and striated in typical glacial fashion. The 

 amount of wear, however, is only moderate. It is far less than 

 the average wear suffered by the bowlders of our Pleistocene 

 drift, as would be expected from the shorter transportation. Fig. 

 9 illustrates fairly well the nature and degree of reduction. This 



