HOBBS' THEORY. 251 



more after the calm begins, starts to move outwards in all directions and so 

 develops (on the edge of the Barrier) a south-easterly blizzard.' 



It would be interesting to know what has been holding the cold heavy air in place 

 on the ice surface during ' the week or more ' that it has been cooling. All theories 

 similar to this neglect the fact that the air will start to move as soon as it commences 

 to coal, ths cons3quenc3 of which is that the cooling might produce a flow of air, but it 

 could njver produca a typical blizzard with its sudden commencement and its violent air 

 motion. 



' Simultaneously with this movement the steam cap over the volcano of Erebus, which 

 normally indicates an upper current from the south-west, swings round to the north 

 and takes on an accelerated movement as though it were being drawn from that 

 direction to supply air to the void resulting from the violent surface current towards 

 that direction.' 



No such action of blizzards on Erebus smoke as that mentioned here was observed by 

 us. We have already discussed th? motion of Erebus smoke during blizzards and have found 

 that the only change is a considerable increase in the frequency of motion from the south- 

 east, so that the relative frequency with which the Erebus smoke moved from the north was 

 less during blizzards than at other times. 



' Corresponding to the increased velocity, the normal f ohn effect near the Pole must be 

 much increased as it is also on the descent of the surface current from the plateau. 

 As soon as the warming of the Polar air from this cause has become general, the 

 high air pressure of the central area is automatically reduced, and thus the blizzard 

 gradually brings about its own extinction. To the warming efiect of the descending 

 air current there is rather suddenly added the latent heat of condensation of the 

 moisture when it is precipitated in the form of fine ice crystals nithin the air 

 layer just above the snow-ice surface. The rather sudden termination of the blizzard 

 may be thus in part explained.' 



Unfortunately for this very ingenious explanation of the end of a blizzard, the temperature 

 observations do not support it in any way. The main rise in temperatm'e which is such a 

 well-marked feature of winter blizzards occurs at the instant the wind rises. The highest 

 temperature is generally reached when the blizzard is at its height, and in nearly all cases 

 the temperature falls appreciably during the last few hours of the blizzard's duration (see the 

 diagrams showing simultaneous wind and temperature during typical blizzards given on pages 

 48 and 49 above). If Professor Hobbs' theory of blizzard action were correct, we should 

 expect a steady rise of temperature from the beginning to the end of the blizzard and a 

 sudden fall of temperature as soon as the wind dropped. 



On considering the whole of Hobbs' paper one cannot helj) feeling that in sjjite of his 

 failing to explain the origin of the precipitation and the mechanism of blizzards he has made 

 out a very strong case for the existence of an anticyclone over all extensive masses of inland 

 ice and over the Antarctic in particular. One would therefore be inclined to agree with the 

 generally accepted idea that there is an intense anticyclone concentric with the Pole and 

 covering the whole of the Antarctic Continent. 



On the other hand, however, Meinardus in his discussion of the results of the Gauss 

 Expedition attacks the theory of the Antarctic anticyclone with gi-eat vigour and one must 

 admit with most convincing success. We will therefore now examine the problem from 

 Meinardus's point of view. 



