THE DRYGALSKI-REEVES PIEDMONT 63 



sounding at Relief Inlet, is abundantly proved by the positive evidence of the 

 former height of the ice flood during the maximum glaciation. The most conser- 

 vative estimate of the heights up to which the adjacent mountains have been 

 glaciated places the former thickness of the ice here as at least 1000 feet, almost 

 certainly 1500 feet, and in the case of the Reeves Glacier probably 3000 feet higher 

 than it is at present. Therefore at Relief Inlet during the maximum glaciation the 

 ice would have been 668 fathoms + 1000 feet = in round numbers 5000 feet thick. 

 Thus we have evidence of three kinds as to the extent of former crlaciation : — 



1. The height to which the rocks above sea-level are glaciated above the 

 level of the adjacent glaciers. 



2. The depth to which the rocks below sea-level have been scooped out 

 by the old glaciers when they pressed hard on their rocky bed, as at Relief Inlet. 



The sounding of 624 fathoms at Relief Inlet does not probably represent the 

 fiill former thickness of the Drygalski ice below sea-level, as the driving tube on 

 each of the three soundings made at this pomt always brought up with it fine 

 marine mud. It may be noted that about 2 miles farther east we obtained a 

 sounding of 668 fathoms. 



3. The height to which the Drygalski Barrier has aggraded its own bottom 

 moraine and submarine eskers as it gradually floated up higher and higher as 

 the deglaciation progressed. 



That the Drygalski Barrier is an outlier of the former Great Ice Barrier, which 

 during the maximum glaciation was continuous with the Drygalski-Nansen 

 Piedmont, will become clear when the glacial evidence along the coast between 

 the Drygalski Barrier and the Ferrar Glacier is being discussed. 



It is much to be hoped that many more soundings will be secured along the 

 coast and in various parts of Ross Sea by the present British Antarctic Expedition. 

 It would be of great interest to further develop by sounding the contour of the 

 sea floor eastwards of the present termination of the Drygalski Barrier. It would 

 obviously also be of importance to secure soundings in Geikie Inlet. Much light 

 will be thrown on the structui'e of the Ross Barrier by a further study of the 

 Drygalski-Reeves Barrier. Its structure, compounded, as it is, of a number of ice 

 jetties united by strips of old bay ice reinforced with the granulated snowfall of 

 many years, makes the Drygalski-Reeves Piedmont in many ways a key for the 

 interpretation of much that is at present puzzling in the structure of the Ross 

 Barrier. 



Lastly, it may be added that the observer cannot but be impressed with the 

 stupendous erosive power of the glaciers of this region during maximum glaciation. 

 The D'Urville Wall and northern clifi" face of Mount Larsen are eloquent tributes 

 to the facetting power of glacier ice. 



