250 GENERAL AIR CIRCULATION. 



One must agree mth Meinardus in this matter and there can be little doubt that Hobbs 

 has left unsolved what we shall see in the next section is the greatest problem of the 

 Antarctic anticyclone, namely, the origin of the precipitation within the anticyclone. 



(2) & (3). Hobbs shows from the records obtained in Greenland and the Antarctic that 

 all alon" the coast and at the outlets from the plateaux there are great accumulations of 

 snow which have been deposited by the \vind and he says : — 



' What may be characterised as the centrifugal snow broom which sweeps out snow 

 deposits from the central areas and collects them upon and about the margins of 

 continental glaciers, is a necessary consequence of strong anticyclonic conditions 

 and its work is in evidence within all areas where inland ice has been extensively 

 explored.'* 

 Hobbs is not very happy in his line of reasonmg here, for the snow accumulations do 

 not themselves prove anticyclonic conditions, they only show that the winds blow outwards, 

 of which th^. actual wind observations have given conclusive evidence. The snow accumulations 

 do however prove that the conditions are not cyclonic, for if they were the greatest accu- 

 mulations would be in the interior where the forced ascending currents would be accompanied 

 by gi-eat precipitation. 



(4) & (6). The blizzard is considered by Hobbs to be one of the strongest factors in 

 support of the general theory of the glacial anticyclone. He therefore goes somewhat fully 

 into the mechanism of the blizzard. As similar explanations have been given elsewhere it is 

 worth our while to examine this theory in some detail. According to it the blizzard is the 

 result of the cooling of the lower air layers which is supposed to proceed until the dense 

 cold air over the inland ice becomes unstable when there is a great outrush of cold air 

 towards the surrounding warm air over the ocean. 



I will o-ive Hobbs' explanation of blizzards in his own words,! and add a series of remarks 

 to point out weak places in the theory. 



'The sequence of events during a bUzzard begins with gentle northerly winds which 

 continue for a day or two during which temperatures are low.' 

 Except that northerly winds naturally occur only in the interval between bhzzards, there 

 is nothing to indicate their connexion. As a matter of fact northerly winds most often occur 

 immediately on the termination of a blizzard and might therefore more justly be connected 

 with the blizzard just passed than with the blizzard to come. We have already shown in 

 the discussion of temperature that the temperature during northerly winds is higher than 

 during similar winds from the south. 



' David has suggested that during this time air is flowing south to take the place of 



air whose volume has been reduced as a result of the heat abstracted from it 



on the ice sirrface.' 



This sucfcestion is obviously impossible. Any loss of volume due to coohng would be made 



good by air flowing inwards in the upper atmosphere and not along the surface where it 



would encomrter the increased pressure due to the dense air. Also a very Uttle consideration 



of the chauf^e of volume with temperature would have showm the fallacy of the suggestion 



even assuming that all the motion takes place along the surface. 



' Then there follow two or three days of absolute calm, during which the temperature 

 continues to fall. Still further cooled upon the ice surface, the air, a week or 



* hoc. cit., page 198. 

 ■)• Loc. cit., page 208. 



