SURFACE OF BARRIER 117 



Drygalski Ice Barrier Tongue. In the work to which reference has just been made 

 these structures are described as movement chasms. Their width is given as about 

 three-quarters of a mile and their depth from 80 to 100 feet. 



It is probable that the inlets known as Skelton, Mulock, Barne, and Shackleton 

 Inlets are all of the nature of outlet glaciers. The fact that both on the west 

 and east sides of Ross Island vast quantities of boulders were discovered, up to 

 heights of 1000 feet above sea-level, of granite and other rocks from the main- 

 land is interesting proof of how, when the Koss Barrier stood about 800 feet 

 above its present level, glaciers descending from the inlets just mentioned carried 

 morainic material from the great horst in a general N.N.E. direction, the 

 erratics probably crossing the long sill terminating in Minna Bluff", and then im- 

 pinging on the western and eastern foothills of Ross Island. At the same time 

 it is possible that these erratics were derived from granitic hills due south of 

 Ross Island, such as those at the mouth of the Beardmore Glacier. The latter 

 hypothesis is less probable than the former, as before the erratics had travelled the 

 great distance of nearly 400 miles, which separates the Beardmore Glacier mouth 

 from Cape Royds, they would probably have thawed their way down for some depth 

 into the ice of the former Great Ice Barrier. Had they reached Cape Royds along 

 this route they would probably have reached it as bottom moi'aine.* 



In his account in The Heart of the Antarctic, vol. ii. p. 12, Sir Ernest Shackle- 

 ton states that the surface over which his party travelled over the Ross Barrier 

 was continually changing. He noticed that at first there was a layer of soft snow 

 on top of a hard crust, with more soft snow underneath that again. This pie-crust 

 snow has already been commented on in the description of the Northern Journey. 

 It is perhaps due to an actual melting of the snow just below the surface, when 

 the general air temperature is below freezing, as well as to deposition of ice 

 vapour ascending from a short distance beneath the snow surface. He states, 

 " When the sun was hot the travelling would be much better, for the surface 

 snow got near the melting-point and formed a slippery layer not easily broken." 

 Probably a certain amount of actual thawing, when the general air temperature 

 was below freezing-point, had taken place in this instance, the thawing being 

 due, as already explained in the account of the Northern Journey, to the 

 low specific heat of ice. The quantity of soft snow met with on the Ross 

 Barrier to the north of the Beardmore Glacier was no doubt due to streams 

 of drift snow which are poured by the plateau winds out of the Beardmore 

 Glacier Valley on to the surface of the Ross Barrier. Shackleton states that the 

 surface of the Barrier near the land was broken up by pressure from the glaciers, 

 but right alongside the mountains there was a smooth plain of glassy ice caused by 

 the freezing of water that had run off" the rocky slopes when they were warmed 



* They would also have become biuieJ probably under some hundreds of feet of snow before they 

 reached the edge of the Barrier. 



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