116 GLACIOLOGY 



as well as from islands such as Brown Island and Black Island. Ferrar on his geological 

 map of this region shows extensive moraines trending northward, from Black Island 

 and Brown Island up to the edge of the " pinnacle ice," belonging to the Boss Barrier. 

 A large portion of the surface of this pinnacle ice is heavily loaded with moraine 

 material. During the thousands of years that the Ross Barrier was at or near its 

 maximum, and flowing from the direction of Mount Discovery far to the north of 

 McMurdo Sound, it must have transported a vast amount of moraine material north- 

 wards, and dumped it on to the floor of the Sound. On this view the submarine 

 ridge is largely a medial moraine derived from Minna Bluft' and Black and Brown 

 Islands. 



Possibly both 2 and 3 causes, as suggested, may have co-operated in producing 

 this remarkable contour of the ocean floor. 



Beardmore Glacier. We can now leave Minna Blufli" and discuss the glaciology 

 of the continuation of the Antarctic Horst southerly to the Queen Alexandra Range 

 where it is intersected by the Beardmore Glacier, and then trace this glacier to the 

 inland ice, as far as Shackleton's farthest south, in latitude 88° 23', longitude 

 162° E. 



As already illustrated in the photographic album of the Discovery Expedition, 

 the eastern slopes of the horst, as far south as the mouth of the Beardmore Glacier, 

 show evidence of the presence of numerous outlet glaciers from the inland ice, and 

 also afibrd clear proof that glaciation has recently been waning. This is well shown 

 by the photographs, chiefly taken by Shackleton, as well as by the excellent sketches 

 by Dr. E. A. Wilson. Shackleton's photographs show very well that between the 

 edge of the Barrier and the land trends a deep almost impassable chasm for a great 

 distance. The origin of this is probably twofold : — 



1. The rocks in contact with the Barrier Ice became highly heated in the rays of 

 the sun, especially during the four months of perpetual sunlight, and consequently 

 thawed the ice for a considerable depth where it has been in contact with the 

 rocks. This is probably the chief cause of the existence of the gigantic moat which 

 in most places bars access from the direction of Ice Barrier to the land. 



2. In part the moat may be due to the Ross Barrier being actually forced or 

 sheared away from the shore-line by great glaciers descending from the high plateau 

 to the west to join the western edge of the Barrier. In this case the moat may be 

 of the nature of a shearing plane like those already recorded in the case of the 

 Drygalski Glacier. The chasm between land and barrier in Shackleton's photo- 

 graph (Plate CVII.) * undoubtedly illustrates a canal of the latter type. It is sug- 

 gested in the description accompanying this plate that the chasm may be considered 

 in part a tide crack " or line of constant rupture between the ice and the floating 

 barrier, and that it was formerly attached to land along the shore." There can 

 be little doubt that it is quite analogous on a larger scale to Relief Inlet in the 



* The Voyage of the Discovery. 



