132 GLACIOLOGY 



horizontally stratified layers of snow, no doubt now largely converted into ice. 

 There is an entire absence of the vertical lamination and disturbed bedding with 

 which one is familiar in true glacial ice in temperate latitudes. At the same time 

 the fact must not be overlooked that in many of the Antarctic glaciers the ice, 

 at all events in its upper portion, shows signs only of horizontal stratification. On 

 the left-hand side of the photograph it will be noticed that the material exhibits 

 a very perfect flat conchoidal fracture. Another proof that, though it may be ice 

 in its lower portions, it is not formed of glacier ice is afforded by the entire absence 

 of vertical fluting of the cliff" face. Had even a small amount of rock dust been 

 present in the material, as is usually the case in the land glaciers of Antarctica, this 

 would quickly have formed dust wells when warmed by the sun's beams, and these 

 wells would have been enlarged downwards to form grooves, as we observed to be 

 the case with the vertical faces of true icebergs facing the sun, i.e. facing north. 



That the Barrier is not altogether formed of old compressed snow is, of course, 

 obvious from the fact that great glaciers like the Beardmore, the Heiberg, the Devil's 

 Glacier, &c., are continually discharging into it vast volumes of glacier ice. It is 

 also proved by direct observation. H. T. Ferrar states : * " The intimate structure 

 of piedmont ice shows that, as far as water-level, it consists of normal glacial ice. 

 On the surface away from the land only fine snow was met with, but close to the 

 shore crevasses and pressure ridges show massive and vesicular ice. The vesicular 

 ice contains air amounting on the average to about 8"5 per cent, of its own volume, 

 and the ice grains are usually less than \ inch across." 



One of us (R. E. Priestley) has recently observed that the material of the Barrier, 

 in the cliffs at the Bay of Whales, is formed of true ice. This locality is, of course, 

 in the immediate neighbourhood of the island buried under ice to the south of 

 Framheim. 



The next piece of evidence, though it is not certain that it bears directly ujaon 

 the question of the origin of the Barrier, is, in itself, very significant. Towards the 

 end of the summer, early in 1908, two tabular bergs drifted from the north down 

 McMurdo Sound, and grounded half-way between our winter quarters at Caj^e Royds 

 and Cape Barne. During the winter, when the sea was firmly crusted over with ice, 

 we visited these bergs, and were able to examine their internal structure by studying 

 the walls of the wave-worn caves. They appeared to be wholly formed of compressed 

 snow down to sea-level, with a veneer of sea ice in such parts as were exjaosed to the 

 wash of the waves and the dash of the spray. During the summer of 1908-9 the 

 Nimrod made use of one of these bergs as an anchorage for shelter from the blizzards. 

 Soundings alongside the bergs, obtained by Captain F. P. Evans, showed a depth of 

 13 fathoms, i.e. the berg was stranded in water having a depth of 78 feet. The berg 

 rose to almost the same height out of the water, but as its eastern side had been 

 lowered considerably through the tunnelling action of the waves and the collapse of 

 * National Expedition, 1901-4, Natural History, vol. i., Geology, London, 1907, i^p. 67-68. 



