I.] GEOLOGICAL OBSERVATIONS 349 



show that the seasonal variations occur at considerably later date 

 than the corresponding air temperatures, and that the maximum 

 temperature reached by the ice is far below its freezing-point. One 

 observation may be quoted in conclusion : Crevasse near the meet- 

 ing-point of the ice of the South-West Arm and of the main 

 stream from the inland ice, November 3, 1903, 7 p.m., depth thirty 

 feet. 



Temperature of the air, + 20 F. ( - 67 C.) 

 ice, -21 F. (-29-4° C.) 



Denudation. 



Wind. — The winds of South Victoria Land prove to be as 

 strong and as constant as any oceanic trade-wind. Around Winter 

 Quarters the bare land surfaces are usually covered by a loose 

 cloak of rock debris quite six inches deep. Below this depth the 

 earth is permanently frozen throughout the year, and from this 

 zone rocks with fresh unweathered fractures may be obtained. 

 The wind removes all the finer disintegration products, so that the 

 exposed surfaces are always composed of stones loosely packed 

 together, which protect a mixture of small stones and impalpable 

 powder beneath. These loose stones are often smoothed and pitted 

 in the manner peculiar to wind- worn stones, and some of the harder 

 ones have a superficial glaze on their exposed surfaces. 



In the Snow Valley at the foot of the Royal Society Range 

 there are granite boulders which have become hollowed by some 

 agent which may be aided by wind. These hollowed blocks 

 resemble cavities in Corsica and elsewhere, to which reference has 

 already been made. 



Water. — In the area covered by our observations the effect of 

 water as an agent of denudation is limited. On the sides of 

 glaciers and among the moraines it serves to separate the gravel 

 from the finer material and to distribute the latter over the surface 

 of the ice. On the north-east side of Brown Island its present-day 

 effects are most marked, for after a summer snowfall in January 

 1903, thawing took place at such a rate that cascades were pro- 

 duced. These coursed down the hillside in narrow channels and 

 spread mud and sand in deltaic form over the lower slopes. 



On the sides of the Ferrar Glacier, the streams that are pro- 

 duced during the summer follow channels between the ice and the 

 rock, and in this way must undercut such cliffs as the Cathedral Rocks. 



