ICE SHEETS AND GLACIERS 



snouts, one of which formed the Mackay Ice Tongue. 

 The Ferrar Glacier was simpler in plan and occupied 

 the finest valley. It offered a relatively unbroken slope 

 to the Plateau and was joined in Siamese-twin fashion 

 to the Taylor Glacier. The latter was stagnant and its 

 empty lower valley has already been referred to. The 

 Koettlitz Glacier was the largest of the four and of- 

 fered an unrivaled study of the effects of thaw-waters 

 and surface weathering on a broad surface of rela- 

 tively stagnant glacier. A detailed description of a 

 traverse of the Ferrar Glacier will give a good 

 idea of their characters (see Figure 8). 



Their positions and dimensions are as follows : 



Name 



Koettlitz, 



Ferrar . , 

 Taylor . , 

 Mackay , 



Position, 

 S. Lat. 



78° 30'- 

 77" 50' 

 77° 50' 

 77° 40' 



77° 



Approxi. 



Average 



Slope 



I in 45 



I in 35 

 I in 30 

 I in 40 



* Has retreated 20 miles from the sea. 



It will be noticed that the grades are by no means 

 steep. Usually for long stretches the glacier is nearly 

 level, and then a considerable rise is encountered where 

 the glacier flows over some sub-glacial and nearly 

 worn-down bar (riegel). Here are numerous cre- 

 vasses, which also occur opposite the tributary glaciers, 

 owing to the thrust of these latter upon the ice of the 

 main glacier. Were it not for these icefalls and tribu- 



141 



