GEOLOGICAL OBSERVATIONS 



amount of the sediments now forming on the sea floor. 

 Ferrar has abeady commented on the great importance 

 of the wind in these regions as a destructive agent. 



By accelerating evaporation of snow and ice, and by 

 its mechanical erosive force on the surfaces of snow-fields, 

 the blizzards are important contributors to the present 

 deglaciation of Antarctica. The amount of snow annually 

 blown out to sea must be very great, inasmuch as during 

 blizzards, often of several days duration, the air is fre- 

 quently so thick with fine particles of snow that one cannot 

 see more than a few yards in front of one. We observed 

 that sledge tracks and footprints on the snows of the 

 coastal areas, or of the inland plateau, were nearly always, 

 after the expiry of a few weeks, left in relief. This 

 suggests that, at present, in many parts of Antarctica the 

 general surface of the snow and ice is being continually 

 lowered by ablation and wind drift. 



(c) Changes of Temperatuee 



During spring and autumn when sunrise and sunset 

 replace the perpetual sunlight of summer, and the per- 

 petual darkness of winter, the range of temperature 

 between noon and midnight is most marked. On March 

 10, 1908, when at an altitude of about 9000 ft., on Mount 

 Erebus, and with the thermometer at about 10° Fahr., 

 we observed that snow in contact with black lumps of 

 kenyte lava exposed to the sun's rays thawed rapidly, so 

 that we were able to get water to drink by laying a lump 

 of snow in saucer-shaped hollows on the surface of this 

 lava. At night these same rocks became very cold. There 

 was no question here of the survival of any original vol- 

 canic heat in the lava, as there was no thaw whatever of 

 the snow where it touched the lava in spots shaded from 

 the sun's heat. This absorption of heat by black rocks 



307 



