98 GLACIOLOGY 



the higher land which formerly existed to the east and constituted the boundary 

 of the lake has been worn down and removed during the recent elevation of the 

 moraines by a combination of the successive summer thaws and marine erosion. 



Thus in the case of all three of these moraines, those of the East Fork of the 

 Ferrar Glacier, those of the Dry Valley, and the Stranded Moraines, the conclusion 

 is irresistible that a considerable portion of the material composing them has either 

 been brought many miles up the coast or has been carried right across the Sound. 

 The three agencies which alone could be responsible for this transport to any large 

 extent are : (1) Shore-drift. (2) A considerably greater extent of the ice-sheet and 

 all its affluents, such as glaciers, barriers, &c. Of such an extension there are 

 abundant evidences, of which we may here mention the finding of granitic and 

 schistose erratics at a height of 1100 feet on the slopes of Erebus. (3) The third 

 agency is the transporting power of icebergs and pieces broken off the ice-foot. At 

 Cape Royds, esjaecially around FlagstaflP Point, large boulders of kenyte were fre- 

 quently seen being carried out to sea on pieces of the ice-foot, and some of the 

 icebergs were observed to contain much fine rock debris. 



This occurrence of kenyte boulders of some size as far north as Granite Harbour 

 has already been noted. The probable explanation of their distribution will be con- 

 sidered when the past history of the Great Ice Barrier is being reviewed. 



The Piedmont. The piedmont ice which has been traced continuously from the 

 Drygalski Ice Barrier to New Harbour, a distance of 150 miles, narrows in very 

 much south of New Harbour. Whereas to the north of this its width has been 

 from 10 to 15 and even up to 20 miles, it is only 2 to 4 miles wide south of the Ferrar 

 Glacier. This narrowing in width is no doubt connected with the presence of that 

 great horst within a horst, the Royal Society Range. Before considering the 

 remarkable ice slabs and Snow Valley to the east of the Royal Society Range we 

 may refer to the piedmont south of the entrance to the Ferrar Glacier Valley known 

 as the Butter Point Piedmont. 



This is part of the gi-eat fringe of glacier ice which borders the great coastal 

 shelf of Victoria Land. It has its origin on the slopes of the Northern Foothills 

 several hundred feet above sea-level,* and at Butter Point is about 2| miles wide. 

 To the south it fringes the sea for 6 miles, and then takes a turn to the S.S.W. as 

 the landward border of the Stranded Moraines, finally ending at the entrance to the 

 Blue Glacier. To the north it continues for a dozen miles as a fringe to the foothills 

 which form the southern border of the lower portion of the Ferrar Glacier Valley. 



A view of this piedmont looking westerly from McMurdo Sound is shown 

 in Plate XXI. 



At the sea it is a cliff" which varies in height from 6 to 20 feet, and during the 

 early days of our stay at Butter Point this cliff was overhung by a fine snow-cornice. 

 During the summer thaw a large number of very fine icicles were formed beneath 



• Fiom about 1000 feet to about 1500 feet. 



