THE HEART OF THE ANTARCTIC 



ridged with sastrugi, which trend from west by south 

 to east by north. These sastrugi have a sharp edge 

 directed towards the west. The latter is the quarter 

 from which the prevalent wind blows near the summit 

 of Erebus. This is the return current of air blowing 

 back from the South Pole towards the Equator. Next 

 our experience on Erebus showed that the south-easterly 

 blizzard sometimes extends from sea-level up to at least 

 as high as the top of the second crater, that is to over 

 11,000 ft. in height. Thirdly, it may be noticed that 

 on the day we reached the summit of Erebus, March 

 10, we found ourselves, at a level of 13,300 ft., within 

 the lower limit of the upper wind which at that time 

 was blowing gently from a northerly direction. It may 

 be remembered that this date was one and a half days 

 after a strong south-east blizzard. These conditions 

 seem to indicate that after a blizzard, and probably 

 during its later phases, the great middle air current 

 normally travelling from near the South Pole towards 

 the Equator, is temporarily abolished, having become 

 absorbed into the immense stream of the blizzard. 



" Fourthly, it may be recorded that the temperatures 

 taken by us demonstrate the following fact, obviously 

 of considerable importance: From sea-level at Cape 

 Royds, up to the summit of Erebus, for the first 6000 ft., 

 the temperature falls at the rate of about 4° Fahr. per 

 thousand feet, but above the altitude the fall is much less 

 rapid, being at the rate of less than 1 ° Fahr. per thousand 

 feet, and in one case the temperature curve on Erebus 

 was found to be inverted. 



" Finally, we had an opportunity, when in our camp 

 on Erebus on the morning of March 10, of seeing an 

 explanation of the remarkable phenomena called ' earth 

 shadows ' by Captain Scott. On that occasion we 

 saw that the rising sun projected across McMurdo 



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