THE GAUSS STATION. 241 



Thus we have good evidence that during 9 months 30 depressions passed near to Cape 

 Adare and it is clear from the maps that in every case the centre could not have been 

 far to the north of the station. 



But for our purpose the most important conclusion is that the large pressure waves 

 which affect the whole of the Ross Sea area are not associated with travelling depressions 

 over the Southern Ocean. On the contrary the pressure changes due to such travelling depres- 

 sions are clearly superposed upon the larger pressure waves. 



Usually the depressions only aSect the pressure curve at Cape Adare, but there are a 

 few exceedingly interesting exceptions to this rule. The depression which passed Cape Adare 

 just before midnight on August 2nd, plate 11, is one of the most interesting examples. 



During August 1st the barometer was falling at all three Antarctic stations under the 

 influence of an Antarctic pressure wave. There can be little doubt that if there had been 

 no disturbance the minimiim of this wave would have occurred at each station in some such 

 way as that shown by the dotted line on the diagram. A deep depression, however, passed 

 just to the north of Cape Adare and its effect on the barometer curves at the three stations 

 is interesting. The dip at Cape Adare was deep and rapid, the fall between 20 hours on 

 the 1st and 20 hours on the 2nd being no less than 115". This rapid fall at Cape Adare 

 appears to have induced a rise of the barometer at Framheim and Cape Evans which if 

 we may take the dotted curves as being approximately the undisturbed barometer conditions 

 was ■&' at Framheim and "3" at Cape Evans. If this example had stood alone it would 

 have been natural to assume that the rise at Framheim and Cape Evans was not really, 

 but only accidentally related to the Cape Adare depression, but there are several other 

 examples. Another and probably better example occurred on August 15th and as in this 

 case there was no pressure wave the increase in pressure is clearly shown on both the curves 

 for Framheim and Cape Evans. In both these cases the fall of the barometer at Cape Adare 

 was large and rapid and the wind at that station reached hurricane force. With lesser 

 depressions at Cape Adare the rise in pressure at the other stations was naturally much 

 smaller and- is generally lost in the larger pressure waves. If, however, the Framheim curve 

 is carefully examined many cases can be seen of the induced rise of pressure at Framheim 

 when a depression passed Cape Adare, generally as a slight increase in the rate of rise or 

 a decrease in the rate of fall. The following examples may be mentioned : April Idth, May 

 16th, August 31st, September 16th. The explanation of this rise of pressure is not obvious, 

 and as far as the writer knows it is a unique phenomenon. Any explanation in the absence 

 of more information is of the nature of a guess ; but there can be little doubt that it is a 

 dynamical effect due to the system of rotating winds suddenly appearing in the opening of 

 the Ross Sea. 



The conditions at Cape Adare are seen from the above discussion to be different from 

 those at Cape Evans and Framheim. The two latter stations are dominated by conditions 

 which are truly Antarctic, while at the former station the weather is affected by cyclones 

 which form over the Southern Ocean and move on the whole from west to east. It is 

 however to be strongly insisted upon that the main pressure changes at Cape Adare are not 

 due to travelling cyclones, but to pressure waves which travel in a north-westerly direction 

 and affect the whole of the Ross Sea area and the surrounding plateau. 



Pressure, winds and weather at the Gauss Station. 



Having discussed in detail the weather conditions in the Ross Sea area and having 

 come to the conclusion that the weather there is not governed by travelling cyclones and 

 anticyclones, but by travelling pressure waves moving outwards from the continent it is 



31 



