216 



PRESSURE, WINDS AND WEATHER. 



Figure 63 is a rough sketch map of the region under consideration. The South Pole 

 is marked S.P., the mean position of the Polar Plateau P.P., Framheim F., Cape Evans E. 

 and Cape Adare A. 



EAST LOka 170° 



WEST LONG- 160' 



Fio. 63. Diagram of pressure wave front. 



Now the wave takes twice as long to travel from Framheim to Cape Adare as from 

 Framheim to Cape Evans, hence if we bisect the line A F in Y the wave must reach Y 

 at the .same time as Cape Evans, hence E Y is the position of the wave front at the 

 moment it reaches Cape Evans. As it happens E Y is practically perpendicular to the line 

 joining Framheim and Cape Adare, hence this latter line gives the direction of movement 

 of the waves. 



Now if we draw lines F X and P.P. Z, parallel to E Y they give the position of the 

 wave front as the wave arrives at each station, and the perpendicular distance between them 

 is proportional to the time taken for the wave to travel from place to place. 



It will be seen that the distance F Z is similar to F Y, hence the wave would take 

 approximately the same time to travel from the Polar Plateau to Framheim as from Framheim 

 to Cape Evans, and we found this to be the case. We also see that the wave would affect 

 the Western Plateau, W.P., very shortly after it arrived at Cape Evans, which also was 

 shown to be so by the observations. 



