52 GLACIOLOGY 



gentle to steep slopes directed southwards, and vertical to overhanging cliffs with 

 snow cornices directed northwards. These chasms were usually about 40 feet deep. 

 According to aneroid levels, which cannot be considered very reliable, as the 

 crossing of the Drygalski lasted for six days, the high portions of the Drygalski 

 Barrier on the route where the northern party crossed it ranged from 130 feet to 

 about a maximum of 200 feet above sea-level. At about a couple of miles south of 

 its northern margin the Drygalski Glacier merged gradually into an undulating 

 snow plain about 100 feet above sea-level. Where this terminates at Relief Inlet 

 soundings were obtained by Davis, first officer on the Nimrod, in 624 fathoms. 

 The bottom was a fine marine mud. If the density of the Drygalski Ice be 

 taken as '88, and the maximum height as 200 feet, the maximum thickness of 

 the Barrier ice, on the line of section, would be about 1960 feet. Obviously, 

 therefore, at Relief Inlet, where the thickness of the Barrier is only about 800 

 to 900 feet, the Barrier must be afloat ; and even where the Barrier on our 

 route of crossing was thickest, if the depth of sea water is still maintained 

 southwards from Relief Inlet at over 3700 feet, the Barrier must be afloat there 

 also. But the question is. Is the depth found at Relief Inlet maintained right 

 under the Drygalski Barrier ? As yet no soundings have been obtained in Geikie 

 Inlet. Two miles E.S.E. of the end of the Barrier Captain R. F. Scott, in the 

 Discovery, got a sounding of 300 fathoms, and at a spot 3 miles to the south-east of the 

 Barrier end one of 368 fathoms. If this shallower depth of 1800 feet be maintained 

 under the highest point of the Barrier on our route, viz. 200 feet, the ice there 

 having a total thickness of 1960 feet, the ice there below sea-level would be about 

 1760 feet thick, so that it would just float in the 1800 feet of water. It therefore 

 becomes a nice point as to whether the Drygalski Ice Barrier is for the greater part 

 aground or afloat. Probably the centre is aground, the sides afloat. As already stated, 

 no definite traces of a tidal crack were observed by us on the south side of the 

 Drygalski, at the point where we first struck it, but at the point where we made 

 our second (the successful) attempt to cross it there was a curious section of 

 this kind (Fig. 10). 



At Relief Inlet the crevasse into which Mawson fell probably marked one of 

 many tidal cracks. The whole of the glacier is a perfect network of crevasses, and, 

 on the assumption that many of them extend right down into sea water below the 

 bottom of the Barrier, the Barrier must be capable of diflereutial movements, so 

 that it may be likened to a slab of flexible sandstone (itacolumite). The eastern 

 extremity of the Barrier was determined by Scott to be 70 feet high. At a distance 

 of 2 miles off it the water is 1800 feet deep, so that if this depth is maintained 

 under the eastern end of the Barrier it must be afloat. 



The curious growths of moss ice which were so conspicuous above the lids of the 

 crevasses near our position, marked on map of Drygalski Ice Barrier 1.12.08, imply 

 probably, as already suggested, that the crevasses for about 2 miles north of the 



