SCIENTIFIC RESULTS 



a fairly fine sediment. While the ice is at its present 

 extent, however, this last agency can only be a minor one. 



Section III 



EFFECT OF THE SUMMER SUN ON DIFFERENT VARIETIES 

 OF ICE AND SNOW 



The melting of large stretches of normally pure snow 

 is carried out by the increase of some grains to the detri- 

 ment of others, and this, in cases where the air tempera- 

 ture is low and the upper crust is cooled by a cold breeze, 

 results in the formation of crusts of snow delicately 

 equipoised over considerable areas, for the vapour from 

 the lower snow crystals is cooled and condensed on those 

 of the upper layer, and in time the crystals of the latter 

 become firmly joined together. Underneath this layer the 

 ablating process still continues, leaving as a final product 

 a powder of much larger granules of snow than the 

 particles of the original drift, whilst the upper crust is 

 only immediately supported from beneath in places few 

 and far between. Quite commonly, when the leader of 

 the sledge-party stepped on the edge of one of these areas, 

 the whole crust would shatter and fall to the ground with 

 a soft sibilant sound. 



It is this process which causes the lessening in the 

 amount of true drift in the summer blizzards. In those 

 winds during this season which were free from snow the 

 only drift was a low one, seldom reaching above our thighs, 

 and I should decidedly attribute this to the fact that the 

 granules of ice produced by the summer ablation are 

 sufficiently large and heavy to prevent an ordinary wind 

 from carrying them very far or high. 



When this process is going on in the drifts above the 

 sea-ice it is somewhat modified, because the sea-ice melts 



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