ANTARCTIC ADVENTURE AND RESEARCH 



section of the Ross Shelf (see B, Figure 21), which 

 suggested that the higher portions of the shelf are 

 sunk deeper in the sea. The highest point noted on 

 the Barrier in 1908 was 240 feet above the sea. If we 

 assume that the density of the ice is eight-tenths that 

 of water, then the lower edge of the ice will be deep 

 sunk in the water as shown in the diagram. If the 

 density is greater (nine-tenths of water), then the 

 lower edge of the shelf is shown by the lower broken 

 line. These higher portions may therefore represent 

 the portions directly fed to the Ross Shelf by huge 

 outlet glaciers of the south, such as the Barne, Shackle- 

 ton, and Beardmore glaciers. The regions between may 

 be largely composed of snow, which fell on the shelf, 

 or in part of frozen sea-ice. He compares the whole 

 structure to a shield formed of a wickerwork frame and 

 covered with hide. Here the rods represent the glacier 

 tongues, the smaller osiers the pressure-ridges, while 

 the drift and fallen snow represent the hide. This 

 theory agrees with the section shown in Figure 19 at N. 

 Obviously portions of the Ross Shelf may resemble (or 

 have formerly resembled) Figure 19 at M. Where 

 Amundsen's and Byrd's headquarters are situated, it 

 seems likely that the structure locally is like Figure 19 

 at O. The whole front has retreated about thirty miles 

 since the survey of Ross. At the Ice Flood Epoch it is 

 likely that the Barrier was one thousand feet above sea 

 level, and at that time it was probably resting largely on 

 the sea floor. This point is also discussed in the next 

 chapter. 



