PRESSURE WAVES AND PRESSURE DISTRIBUTION. 2l3 



At 8 A.M. on May 27th the highest pressure is at Framheim and the lowest at Cape 

 Adare. The easterly wind at Framheim, although light, is the only indication we have of 

 the run of the isobars. The lines have been drawn to show high pressure over the Barrier 

 and low pressure over the Ross Sea. At 8 p.m. of the 27th the wave crest is over Cape 

 Evans and this station now has the highest pressure, but instead of anticyclonic conditions 

 we find a blizzard blowing at Cape Evans which together with the easterly wind at Framheim 

 shows that there is an area of low pressure over the Ross Sea, just where one would expect 

 the maximum pressure to be if an anticyclone were travelling from Framheim to Cape Adare. 

 At 8 A.M. on the 28th the crest of the wave has arrived at Cape Adare where the pressure 

 is now highest. Thus since 8 a.m. on the 27th the crest of the wave has travelled from 

 Framheim to Cape Adare, but it is quite clear that an anticyclone has not crossed the Ross 

 Sea. Thus the trough of this wave was not connected with a travelling cyclone nor the crest 

 with an anticyclone. 



Another e.xample is the wave which passed Framheim during September 30th and 

 October 1st and 2nd, plate 16. At 8 a.m. on September 30th the pressure is lowest over the 

 Ross Sea just to the north of Framheim. The barometer is falling rapidly at all stations 

 but the most so at Framheim where the trough of the pressure wave arrives just after the 

 8 p.m. observation on the 30th. At 8 a.m. on October 1st the pressure is rising at Framheim 

 and the trough of low pressure is just over Cape Evans. By 8 p.m. the trough has arrived 

 at Cape Adare and the pressure crest is about to reach Framheim. At 8 a.m. on the 

 next day the trough has passed Cape Adare and the maximum is half way between Framheim 

 and Cape Evans. The crest has just arrived at Capo Evans on the evening of the 2nd 

 and passes on to Cape Adare where it arrives much reduced in intensity at 8 a.m. the 

 next morning. During the whole period there has been no essential change in the pressure 

 distribution over the whole area. When the trough was over Cape Evans on the morning of 

 October 1st the only effect was, by reducing the pressure over the west of the Ross Sea, 

 to bring the Ross Sea depression nearer to Cape Evans. It is quite clear from the maps 

 from 8 A.M. on the 30th September to 8 p.m. on the 3rd October that neither a cyclone 

 nor an anticyclone has travelled from Framheim to Cape Adare, yet in this interval a 

 wave, I mch in depth, has travelled across the whole area. It is important to notice 

 that here again the depression over the Ross Sea was highly developed when the 

 crest of the wave was between Framheim and Cape Adare on the evening of October 

 2nd. 



If the reader will now take the trouble to turn over the pages of maps and compare 

 the pressure distribution with the pressure waves, he will soon be convinced that the waves 

 are not caused by the movements of cyclones and anticyclones. 



As the pressure waves are not due to travelling cyclonic and anticyclonic systems, we are 

 compelled to assume that they are true pressure waves traversing the upper atmosphere 

 in the same way that water waves travel across the sea. If this is so, we ought to find 

 evidence of them on the surrounding plateau. The observations made there have, therefore, been 

 investigated. 



For this purpose two sets of data are available : 



(a) The observations made by the Polar Party during their journey to and from the 

 Pole after mounting to the plateau by way of the Beardmore Glacier. Latitude 

 87° S. was reached on December 31st, 1911, and from this point to the Pole 

 the surface was very uniform consisting of a rise at the rate of 7'3 feet per 

 geographical mile to about latitude 88° 10', then level until 88° 40' and finally 



