THE HEART OF THE ANTARCTIC 



tion of the dominant sastmgi. Maps of these will be 

 published in the Meteorological Memoir. It is certain 

 that a good deal of the westerly wind experienced by the 

 Northern Party in their journey along the sea-ice near 

 the coast was practically a land breeze. It used to spring 

 up soon after midnight, and keep on blowing pretty 

 freshly until about 10 a.m. on the following day. It was 

 observed that occasionally in the neighbourhood of Mount 

 Nansen a breeze would spring up from the north-east off 

 Ross Sea, carrying dense cumulus clouds inland. 



High-level Atmospheric Currents.— On January 

 14, 1908, Messrs. Leo. Cotton, Douglas Mawson and T. 

 W. Edgeworth David were able to get some observations 

 of the direction and rate of movement and height of the 

 upper wind current, in latitude 69° 53' South, longitude 

 179° 47' West. We estimated that the mean height of 

 the mackerel sky which seemed to be formed at the base 

 of the anti-trade wind was on this occasion between 13,000 

 and 14,000 ft., and we determined that the rate of move- 

 ment of the mackerel clouds was about twenty-miles per 

 hour in a south-easterly direction. This does not mean 

 necessarily, of course, that the upper wind was not moving 

 at a still more rapid rate, but the figure may be looked 

 upon as the minimum speed for that current. 



At Mount Erebus our winter quarters were situated 

 in an exceptionally favoured position for observing the 

 upper cuiTcnts of the atmosphere. Not only had we the 

 great cone of Erebus to serve as a graduated scale against 

 which we could read off the heights of the various air 

 currents as portrayed by the movements of the clouds 

 belonging to them, but we also had the magnificent steam 

 column in the mountain itself, which by its swaying from 

 side to side indicated exactly the direction of movement 

 of the higher atmosphere. Moreover, during violent 

 eruptions like that of June 14, 1908, the steam column 



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