100 GLACIOLOGY 



This width is maintained until the Nordenskjold Ice Tongue is approached, and 

 there it almost ends near Charcot Bay and Cape Bruce. 



To the south side of the Nordenskjold Ice Tongue it reappears, having there 

 a width of from 7 to 8 miles, extending with slightly varying width from here 

 to New Harbour. Its surface area cannot be far short of about 1500 square 

 miles. Its upper surface is for the most part convex from the foothills to the sea- 

 cliff. It is rough and irregularly pitted. Probably dust blown off the ranges 

 contributes to this end. In places, as between Mount Chetwynd and Mount Creak, 

 it is seamed with channels apparently formed by thaw-water. (See Fig. 3-3.) 

 They seem to be of different origin to the shearing channels already described 

 as conspicuous features at the Drygalski Ice Barrier Tongue. Probably they are 

 formed by thaw-water streams having their origin in the steep slopes of the plateau 

 rocks above the foothills at the head of the piedmont. 



Seawards the piedmont terminates either in low cliffs, from 10 to 50 feet in 

 height, or in a steep, convexly curved slope. The piedmont rests on a foundation 

 which is certainly in part formed of solid rock. It is also certain that at intervals 

 some morainic material of the nature of bottom moraine is present, but there is no 

 evidence of its attaining any considerable thickness. Nothing of the nature of 

 till (or boulder clay) was observed under the piedmont. At the same time it must 

 be admitted that the deepest hollows below sea-level in which boulder clay would 

 be most likely to accumulate are still hidden under the ice. The piedmont cannot 

 be in a state of active movement, as no single instance was observed of its having 

 ridged up the sea ice in contact with the base of its cliff, a result which would cer- 

 tainly follow from rapid forward movement, as was observed in the case of the old 

 sea ice at its junction with the southern side of the Drygalski Ice Barrier. In the 

 vicinity of the outlet glaciers the piedmont of course merges insensibly into the ice of 

 those glaciers. The question which now arises is, what is the origin of the piedmont ? 



Two suggestions may here be offered : — 



(1) That it is a shrinking remnant of the part of the old Boss Barrier where 

 it was fed chiefly from the snows from the western plateau. 



(2) That it owes its origin (a) partly to local snowfall on the platform on which 

 the piedmont rests, (6) partly to snow drifted (i) by plateau winds, (ii) by the 

 southerly blizzards. 



This second suggestion may be termed the snow-dune theory. 



In reference to the first suggestion, it is certain that the Boss Barrier has at one 

 time covered the whole of the plain upon which the piedmont now rests from a 

 little south of the Ferrar Glacier mouth to at least as far north as the Drygalski 

 Glacier. 



When it is said that the ice of the Great Ice Barrier formerly covered the plain, 

 on which the great piedmont of the west shore of Ross Sea rests, it is to be under- 

 stood that the ice of this piedmont did not come necessarily from the south, but was 



