PLATEAU WINDS. 141 



observations from the north-west as compared with only 3 per cent, as observed from Hut 

 Point itself. This indicates that tlie position at Hut Point was not good for observing 

 motions of Erebus smoke from the north-west, while as one got into a better position 

 during the sledge journeys the relative number of observations from the north-west increased. 

 A perfectly free view would no doubt have increased the relative frequency still further. It 

 therefore appears safe to conclude that the frequency from the north-west as observed at 

 Hut Point should be increased 



If the south-west frequency at Cape Evans and the north-west at Hut Point were in- 

 creased as here suggested, the two diagrams would become the same in all essentials. 



On the Discovery Expedition cloud motion was determined without instrumental aid and 

 therefore the high clouds, the direction of which could be determined, were lower than those 

 observed at Cape Evans. From internal evidence I am inclined to believe that the high 

 clouds observed at Hut Point were those described as medium at Cape Evans, with a few 

 of the lower cirrus clouds included. As Hut Point is not within McMurdo Sound westerly 

 and south-westerly motion is possible at the height of the medium clouds above that station, 

 therefore the motion of these clouds over Hut Point was diiierent from their motion over 

 Cape Evans. It \\all be noticed that the diagram for high clouds at Hut Point is almost 

 exactly the same as the diagram for Erebus smoke as observed at Cape Evans, especially 

 if the latter is corrected as suggested above by increasing the observations from the south- 

 west. Thus the motion of the so-called high clouds over Hut Point confirms the mean motion 

 of the atmosphere deduced from the observations of Erebus smoke at both stations, leaving 

 the motion of the upper atmosphere to be indicated by the true cirrus clouds observed by 

 aid of the camera obscura at Cape Evans. 



Plateau Winds. 



The plateau which exists behind the Western Mountains and extends from north of Cape 

 Adare to well beyond the South Pole is at an elevation of between 6,000 and 10,000 feet. 

 The wnds on its surface are therefore important in discussing the motion of the atmosphere. 

 This plateau has been reached six times : (1) by Captain Scott in November 1903 when he 

 ascended the Ferrar Glacier and travelled westwards over the We.stern Plateau to 78° S. 

 and 146^° E. ; (2) by Shackleton in 1908-09 when he ascended the Beardmore Glacier and 

 reached the Polar Plateau for the first time ; (3) by David who in the same year ascended 

 by means of the Drygalski Glacier in his successful attempt to reach the south magnetic pole ; 

 (4) by Captain Amundsen who reached the South Pole on December 17, 1911 ; (5) by Captain 

 Scott in 1911-12 on his ill-fated journey to the Pole ; and (6) by members of Mawson's 

 Australian Expedition who in 1913 attempted to reach the south magnetic pole from their 

 base in Adelie Land. 



Of these six visits to the plateau detailed meteorological 'results are only available at 

 present for Captain Scott's two journeys and for Amundsen's. It is only possible therefore to 

 discuss the wind records in any detail for these three journeys, although from the descrip- 

 tive accounts of the other journeys more or less fragmentary information about the winds can 

 be obtained. 



Winds on the Plateau near the vxagnetic pole. 



Members of Mawson's expedition led by R. Bage * left their main base in Adelie Land 

 on November 10, 1913, and proceeded towards the magnetic pole. Their journey took them 



* The Home of the Blizzard, Vol. 1, page 274. 



