206 GENERAL GEOLOGY 



to the south, that is to say, their edges were directed towards the sun at the time 

 of day when it is highest. These ice plates were so fragile that they collapsed in 

 multitudes as we walked over the drifts, and a slight breeze whirled quantities 

 of them along, often rolling them on their edges." 



In the Drygalski-Reeves Piedmont area these plates were much thicker, 

 frequently quite strong enough to support the weight of a man. 



There can be little doubt that this remarkable and beautiful structure is the 

 result of etching of old snow-drifts by the heat rays of the sun. The thawing of 

 the surface snow sets free thaw-water, which under gravity creeps down the planes 

 of bedding of the snow, being arrested by the less pervious layers, and there during 

 the cold of night it freezes, and the process being repeated from day to day, the 

 remarkable inclined plates of ice result.* 



This is not a complete explanation of the phenomenon, for, as Murray remarks, 

 " a stratification resulted which appeared to have no relation to any original 

 stratification of the snow." 



Transportation. The glacier itself is still a very important agent of transport- 

 ation, but the amount of this work it does to-day is nothing to what it must have 

 done at or near its maximiun period of glaciation. All along the length, wherever 

 the slope of the sides of the valley is gradual enough to support debris, they are 

 strewn with a miscellaneous collection of rock which, for many hundreds of feet 

 above the present level of the ice, can only have been carried and deposited there 

 by the glacier. In many places the rock is mingled with angular fragments, 

 obviously derived by frost-weathering from the neighbouring cliffs, but the presence 

 of the old lateral moraine is still indicated by the number of subangular and 

 rounded blocks of rock in the lower portion of the screes. 



Another important agent in removing the light material is the wind, and its 

 power is shown by the amount of small sediment which is scattered over and in the 

 surface ice of the glacier. 



Lastly, the agents which are having most effect at the present day are the many 

 streams of thaw-water which seam the glacier in every direction during the thaw- 

 season. Inunense quantities of fine sediment must be annually removed in this 

 manner in spite of the shortness of the thaw-season, for all these streams that we 

 saw had a good deal of small gravel in them, and those pouring into the lake near 

 the Solitary Rocks were thick with sediment. The result of this transportation is 

 well seen in the New Harbour Dry Valley, from which the ice has retreated, 

 leaving a vast hummocky sheet of the ice- and water-transported debris exposed 

 to view. 



• Unfortunately we had exiausted the last of our photographic plates before we descended from 

 the Magnetic Pole Plateau on to this unique type of glacial surface, and so are unable to figure it. 



