ANTARCTIC ADVENTURE AND RESEARCH 



end of the Ross Sea (see Figure 6). It is triangular 

 in plan and is about five hundred miles wide by five 

 hundred miles deep. The terminal face runs nearly 

 east and west in latitude 78° S. Here it effectively 

 bars the progress of ships and here only is the term 

 Ross Barrier really applicable. This ''sea wall" varies 

 in height from six to one hundred and sixty feet above 

 the sea. 



The northern edge is floating for most of its extent, 

 as is shown by the fact that the "Nimrod," when 

 moored to the ice, moved up and down with the tide in 

 unison with the ice shelf. Captain Scott in the hut 

 called our attention to the extreme tenuity of this 

 sheet of ice. For if it be assumed that it is about seven 

 hundred feet thick, this is a very small dimension com- 

 pared wath its extent of one hundred and fifty thousand 

 square miles. He compared it in shape to a sheet of 

 paper floating on the surface of the sea. The surface 

 is slightly undulating, but where it approaches land at 

 the margins, or where glaciers enter it, it is thrown into 

 pressure waves some forty feet high and one or two 

 miles from crest to crest. Its rate of movement has 

 been determined from the movement of a depot laid 

 down by Scott in 1903. The rate is about four hun- 

 dred and ninety-two yards a year in the portion one 

 hundred miles south of Ross Island. Here also it was 

 determined that eight feet two inches of snow (with 

 a density of 0.5) had been deposited in six and one 

 half years. 



Sir Edge worth David has given a good deal of at- 

 tention to the origin of the Ross Ice Shelf. He bases 



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