22 METEOROLOGY 



the nearest open sea, the temperature of which cannot be below 28° F. The steep 

 isotherm grade in Antarctica, combined with the quaquaversal slope of the land sea- 

 wards from the Southern Temperature Pole all tend to fuither accelerate convection 

 currents, and so promote advection of relatively warm air in winter, except in flat 

 areas like Framheim and the Ross Barrier to the south, remote from mountains or 

 plateaux. In summer the ice of the Arctic Ocean breaks up, and wide lanes of open 

 water penetrate to the North Pole itself, and this open water breathes warmth into 

 the surrounding air. Moreover the permanent surface cyclone of summer is con- 

 stantly carrying in warmth to the North Pole at that season. On the other hand 

 during the Antarctic summer the high gently domed land-mass, capped by a per- 

 manent anticyclone, blows cold air outwa)'ds spiralling seawards, and keeping down 

 the temperature along its coasts to near freezing-point, and according to Meinardus 

 and Hann, making the temperature at the South Pole, reduced to sea level, about 

 21-2° F. ( - 6-5° C.) for the month of January.* 



Such geographical differences appear to offer a partial, if not a comjolete, 

 explanation of the existence of such different temperatures on the same parallels oi 

 latitude, as have been recorded from the Arctic and the Antarctic respectively. The 

 matter is thus referred to by Dr. H. R. Mill : f 



" Even in the South Orkneys, in latitude 60°, in the three warmest months, the 

 air scarcely rises above the freezing-point as an average, while in Shetland (60° N.) 

 the temperature of the summer months averages 54° F. But, on the other hand, the 

 warmest month of the year even in 77° S. has had a mean temperature as high as 30°." 



Prevalent Winds. The accompanying map (Plate VI.) shows the direction of all 

 the principal sastrugi — hard snow ridges separated from one another by furrows torn 

 out of the hard snow by the fury of the blizzards. 



From the south end of Boss Island as far as 88° S., the information was obtained 

 by Lieutenant Adams ; while those from Mount Erebus, to the South Magnetic Pole 

 Area, were obtained by our Northern party. The sastrugi directions on the plateau 

 west of the Royal Society Range are taken from the description in Captain R. F. 

 Scott's "Voyage of the Discovery." The importance, in control of surface wind 

 directions, of distribution of land and water, and the relief of the land is at once 

 apparent from this map. 



The sastrugi from 88° S. on the King Edward VII. Plateau, northwards as far as 

 80° 30', come from between S. and S.E., modified by the presence of the outlet 

 glaciers, such as Beardmore Glacier, and the glaciers of Shackleton Inlet. Again 

 from south of Minna Bluff, nortliwards to the Drygalski Ice Barrier Tongue, the 

 general trend of the sastrugi is on the whole northerly. 



* It seem.s doubtful in view of the temperatures obtained by Sbackleton near the South Pole, and 

 Amundsen at the South Pole itself, whether 21'2° F. is not too high a figure for the mean temperature, 

 reduced to sea level, of the South Pole in January. Possibly about 12° F. is a closer approximation. 



t The " Encyclopiedia Britaunica," 11th edition, vol. sxi. p. 970. 



