840 DR J. H. HARVEY PIRIE ON 



deep blue colour seen in many of the tabular Antarctic icebergs, or even so deep in 

 colour and solid in structure as the bottom layers of these same ice-sheets as seen 

 on the terminal faces. The explanation of this direct conversion of snow into 

 ice is, I think, to be found in the meteorological conditions of the locality referred 

 to on pp. 842, 843. 



Main Poi'tion of Glaciers. — The second and main part of the glaciers extends 

 downwards from the Bergschrund, and forms a gently sloping terrace between the hills 

 and the sea. 



Winter Snow and Surface. — The surface of this more level portion of the ice- 

 sheets is throughout practically the whole year covered with snow. The snow which 

 falls in winter below temperatures of about 10° F. ceases to have the form of large 

 feathery six-rayed flakes, and consists of small dry powdery granules. It very quickly 

 becomes hard and firm in consistence through wind packing, and within a couple of 

 days, if there has been no subsequent fall of snow, will show erosion forms. This 

 erosion is brought about by the snow itself blown by the wind. At temperatures below 

 about 0° F. the snow is actually gritty like sand, and when blown by the wind, as it is 

 almost constantly with low temperatures, it forms something like a sand-blast on a 

 small scale. Large sastrugi are formed more as a result of wind drifting and accumula- 

 tion than of erosion, although secondary erosion may occur on the sastrugi themselves. 

 The usual erosion forms noted were shallow irregular-shaped areas, leaving correspond- 

 ingly irregular patches standing out a few inches above the general surface. The 

 typical barchan shapes described by Vaughan Cornish (17) were not observed. Where 

 the snow had been still more compressed, as, for instance, by the passage of a man on 

 ski, after one or two days, the erosion would result in the ski-tracks standing out like 

 a couple of rails about an inch above the surrounding surface. 



Thin streaks of ice quickly appear in the surface snow from the melting which 

 occurs even in winter at times when the temperature is above melting-point (see p. 834). 



Summer Surface. — In summer the whole surface becomes on warm days or in the 

 strong sun one huge wet, soft, granular n^ve. On foot one sinks into this in the day- 

 time although it makes a good enough travelling surface on ski ; at night a hard crust 

 forms which makes an excellent surface for travelling. Only on the more sloping 

 glaciers, where accumulation is probably less and ablation by the draining off of melted 

 snow more complete, does the snow coating entirely disappear in summer, leaving 

 exposed hard glacier ice. Examples of this which may be quoted are some of the small 

 glaciers on Mossman and Pirie Peninsulas, and the snout of the Scotia Bay ice-sheet 

 ending on The Beach. This summer melting gives rise to small rills of water running 

 in shallow grooves in the ice, but usually soon disappearing down tracks or crevasses, 

 and small streams are to be met with in places issuing from below the terminal ice- 

 cliffs apparently purely the result of surface melting. These are not numerous, 

 however, and are always quite tiny in size, the largest actually observed being not 

 more than a foot across and rather less in depth. 



