PLATEAU WINDS. 



143 



January 4 inclusive) and. Scott durinc; 4.5 days (December •22 to February 4 inclusive, 

 observations are wanting on tlie .5th and 6th February). As a rule each observer recorded 

 the wind direction and force three times each day, but occasionally they observed more 

 frequently and occasionally less frequently. In order to obtain a regular series of observa- 

 tions, when more than three observations were taken on one day only three of the recorded 

 observations have been used, while on the few occasions on which less than three observa- 

 tions were recorded probable values have been inserted when possible. In this way the 

 series is homogeneous and complete except for two directions in Amundsen's series which it 

 was impossible to supply. Scott's Party recorded wind forces on the Beaufort Scale, these 

 have been reduced to velocities by the equivalent values given on page 130. Amundsen 

 estimated the wind strength in metres per second, which have been converted into miles per 

 hour. 



It is necessary to say a few words with regard to the directions used by the two 

 observers. 



Scott approached the Pok^ almost e.vactly along the 160'' E. meridian while Amundsen 

 approached it along a mean meridian of approximately 170° W. Now each observer naturally 

 recorded a mnd as south when it blew along the meridian on which he was situated, thus 

 for Scott a south wind blew along the 160° E. meridian and for Amund^en along the 170° W. 

 meridian, thus the winds recorded as south by the two observers were inclined to one 

 airother by 30°, and other directioias differed by the same amount. In other words a flow 

 of air which was south for Amundsen was 30° to the west of south for Scott. In order to 

 correct for this cliiference of designation of the same wind all the observations made on the 

 plateau by Amundsen have been rotated clockwise through one compass point (27|°), thus 

 making them agree very nearly with the direction which Scott would have experienced. This 

 may be stated by defining a south wind on the plateau as air motion parallel to the 160° E. 

 meridian with other directions related in the normal way to this main direction. The 

 following tables summarise the chief results of the wind observations. 



Table 75. 

 Wind on South Polur Plateau fS.=parallel to 160° E. merulmn). 



