THE HEART OF THE ANTARCTIC 



got to the latitude of Cape Royds, 77° 32' South, an 

 acceleration of the upper current above it had already set 

 in. This led to the curving of the upper current into a 

 direction more or less parallel to meridians as it rushed in 

 to take the place of the cold wind escaping from the 

 neighbourhood of the pole. The increased speed of circu- 

 lation of the upper current increased the normal fohn 

 effect at the pole, and this, combined with the more rapid 

 transfer of warm air from the north to the south by the 

 medium of the upper current, together with the latent 

 heat from the snow formed combined to raise the polar 

 atmospheric temperature, and so temporarily to make that 

 region a region of relatively low pressure instead of rel- 

 atively high, that is, relatively, as compared with the 

 normal atmospheric pressure there. As soon, however, 

 as this warming of the polar air had become general con- 

 ditions for a blizzard wind ceased, and a period of calm 

 supervened. At the moment of the cessation of the wind, 

 conceivably, a species of hydraulic ram effect made itself 

 felt in the suddenly checked anti-trade wind current above, 

 which led to the stoppage of that great air stream tem- 

 porarily, and its resurging back equatorwards, thus pro- 

 ducing a curious high-level current frequently seen by us 

 after a blizzard in the neighbourhood of Erebus. 



To return from this theoretical digression to 

 observed facts, an occasional precursor of the cessation 

 of a blizzard was the veering of the wind from south-east 

 through east-south-east to east. 



That these blizzard winds occasionally blow right 

 across the Antarctic Circle, and reach the shores of 

 Australasia, is indicated by the experience of the Nimrod. 

 When she left Cape Royds on February 23, 1908, she 

 left us in a light south-easterly wind, the survival of a 

 previous blizzard, and the following four days it was still 

 blowing a blizzard. Then, after a partial cessation of the 



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