242 PRESSURE, WINDS AND WEATHER. 



natural to examine the weather at other Antarctic stations to see if further evidence in 

 support of this conckision can be found. In view of Meinardus's full discussion of the 

 observations made at the Gauss Station this offers a suitable example. 



The Gauss Station was in G6° 2' S., 89" 38' E. only 53 miles from the edge of the 

 Antarctic Continent. The situation was ideal for observing the force and direction of the 

 wind as there were no high lands in sight. 



The most remarkable feature of the weather of the Gauss Station was an almost im- 

 interrupted succession of high easterly winds. Meinardus devoted a large amomit of work to 

 investigating the weather characteristics of these wdnds and found that they were accompanied 



by " 



(«) high temperature, 



(b) vapour pressure and relative humidity in excess, 



(c) large amounts of cloud, 



(d) large amounts of precipitation. 



He sums up his discussion of these winds with the remark : 



'All these weather characteristics correspond in every detail with the type of weather 

 found in both hemi.spheres in the eastern half of depressions near to their centres. 

 This leads to the conclusion that the weather during the east winds is governed by 

 depressions the centres of which lie in the northern or north-west quadrant of the 

 horizon.' 



Further these cyclones are supposed to travel from west to east along the parallels of 

 latitude ; and the geometrical position of their centres is along the trough of low j^ressure 

 which he fixes, in the longitude of the Gauss Station, as varying between 59° S. and 

 64° S. 



This conclusion is little different from that of Lockyer, except that Meinardus appears 

 to consider that the centres of the cyclones often pass over or near to the edge of the Antarctic 

 Continent, while Lockyer considers that the conditions are best represented by cyclones of 

 large extent the centres of which actually travel on or near 60° S. 



We will now examine a few typical records of the barometer changes at the Gauss 

 Station and then build up a cyclone which would account for the pressure changes and 

 see how the winds observed agree with those which the passage of the cyclone would 

 cause. 



On plate IV of this volume the pressure and wind observations made at the Gauss 

 Station have been plotted for eleven periods during which there were large and rapid clianges 

 of the barometer. In the following discussion we shall fi.x our attention on the portion of 

 the pressure waves in which the barometer falls and rises by half an inch. A line has 

 therefore been drawn in the hollow of each wave half an inch above the minimum and the 

 time taken for the barometer to fall and rise the half inch has besn entered above each line. 

 Now if these waves are caused by the passage of cyclones the wind changes below the line 

 should correspond to the changes observed when the ' trough ' of a cyclone passes over a 

 station. What these changes would be can be found by the method indicated by Gold in 

 his paper ' Barometric Gradient and Wind Force ' (M. 0. No. 190, 1908). 



Suppose that the circular cyclone represented in the following diagram is moving from the 

 west to east, and that the centre passes to the north of the station which successively occupies 

 the positions A, C and B relatively to the centre. From A to C the barometer falls and 

 from C to B it rises. Let us consider that A is so chosen that the barometer falls 

 half an inch in going from A to C, then from the geometry of the figure we can calculate 



