120 GLACIOLOGY 



large valley was excavated entirely first, and the smaller modern valley over- 

 deepened in it later, or whether, in the third case, the modern trogtal and the 

 "alb" terrace are being excavated simultaneously, the former by the ice of the main 

 glacier stream, the latter by corrie glaciers. It appears to the authors that the clitf 

 face above the corrie glacier is due to some more powerful erosive action than that 

 of the well-known work of the cirque glacier at its sides and base, aided by changes of 

 temperature and thaw phenomena. The foreign erratics on the top of Mount Hope 

 force upon one the conclusion that thick masses of glacier ice have at one time 

 attained to this level. It seems further probable that the level of this terrace was 

 not the lowest level of the great glacier, the ancestor of the Beardmore, during 

 the maximum of the ice flood. One may arrive at some approximation to the 

 thickness of the Beardmore ice during maximum glaciation from the following 

 consideration : — 



According to the levels taken by means of the hypsometer the ice surface ot 

 the Ross Barrier, near the outlet of the Beardmore Glacier, does not much exceed 

 200 feet above sea-level. This would give a thickness for the ice where it fanned 

 out at a distance of some 20 miles from the shore of the Ross Barrier of from 1600 

 to 1800 feet. Opposite to Mount Hope itself the thickness of the ice is probably 

 considerably greater. If we are correct in surmising that during the ice flood 

 the ice was thick enough to floAv steadily over the top of Mount Hope, it was 

 probably at that time at least 3000 feet, certainly 2000 feet, higher than it is now.* 

 One may, however, reasonably assume that during the maximum of the ice flood 

 the ice of the Beardmore Glacier was from 3000 to 4000 feet in thickness, possibly 

 more. Traces of waning glaciation were observed not only in the form of the foreign 

 erratics stranded on the top of Mount Hope, but also in the shape of enormous 

 lateral moraines. These moraines in the neighbourhood of the Cloudmaker ascended 

 to 200 feet above the present glacial level, and evidently mark a very recent retreat 

 of the glacier. Had the moraines been very ancient the blocks of stone would 

 have crumbled down into the form of fine rubble as the result of the great diurnal 

 range of temperature. An immense medial moraine was observed between the 

 Cloudmaker and the great nunatak, Buckley Island, formed partly of coal-bearing 

 rocks, partly of limestone. This moraine was traced over a distance of 60 miles 

 up to the head of the glacier to the large nunataks of Mounts Bartlett, Buckley, 

 and Darwin. It was in one of the sandstone blocks in this moraine, derived from 

 the Beacon Sandstone, that a small piece of fossil wood, figured later in this 

 volume, was obtained.f The boulders of the moraine here in December 1908 were 



• It does not of course follow that it was nece.ssai-ily from 2000 to 3000 feet thicker than now, 

 as one has to allow for perhaps a fair amount of glacial erosion subsequent to the climax of the 

 ice flood. 



t The presence of small plant structures resembling rootlets in the adjacent shales suggests that 

 the tree to which this wood, apparently coniferous, belongs was not drift wood, but grew in situ. 



