118 MR ROBERT C. MOSSMAN ON THE METEOROLOGY OF 



that, with the exception of this last-named low-pressure area, these cyclonic centres are 

 situated in those regions where the ocean extends furthest south and where the forces 

 exerted by the mixture of the rivers of cold desiccating air from the Antarctic continent 

 and the humid air of the oceans are at a maximum. As bearing on this point, it may be 

 noted that every occurrence of ''Glazed Frost" seen on the voyage of the " Scotia" in 

 the Weddell Sea was observed in from 67° 10' to 67° 39' S., and that at the South 

 Orkneys this phenomenon is at a maximum in winter, when the theatre of cyclonic 

 activity is north of its summer position. 



It will be further noticed that these low-pressure regions are situated approximately 

 in the longitudes occupied by the permanent southern high-pressure belts, and, like them, 

 are subject to seasonal oscillations. Judging from the summer observations, the 

 winds in and near the centre of these permanent low-pressure areas are not of much 

 force, the ring of steep gradients being, as one would expect, where the Antarctic 

 anticyclone is most developed with reference to the contiguous low-pressure system. In 

 the Weddell Sea the effect of the wind-circulation is clearly shown in the direction of 

 the sea surface currents. The observations of Weddell and the "Scotia "show that 

 there is a strong set to the N.W. to the south of 66° S., but in from 64° to 65° S. on 

 the meridian of 40° W. the set changes to the E. and E.N.E., which is the general 

 direction of the surface drift in lower latitudes. Not only so, but in the region 

 dividing these two currents a large number of weatherworn bergs were seen, which, 

 judging from their general appearance, had been in the vicinity for a long time. This 

 region may therefore not inappropriately be termed the " Weddell Sea Doldrums." 

 At the South Orkneys the whole set of the pack and of the icebergs is to the E.N.E., 

 and the few cases of opposite movement recorded were probably a tidal effect. 



The circumstance that there is a distinct seasonal change in the position of these 

 " centres of action " is evident. Not only do the surface winds change with the 

 season, but these changes are also clearly observable at the cirrus level ; thus in summer 

 the prevailing direction of the upper clouds at such places as South Georgia and the 

 South Orkneys is from the west and north-west, but in winter the upper currents show 

 a large movement from the south and south-west. This indicates that at the cirrus 

 level (which in these latitudes is at a comparatively low altitude) the low-pressure area 

 to the south-east has swung more to the north. At the " Belgica's" position in 70° to 

 71 ° S., long. 80° to 90° W., exactly the reverse obtains ; and it is of interest to note that 

 the maximum rate of movement was from the north-east at both seasons. The whole 

 question is exceedingly interesting, but it is not safe to draw conclusions pending the 

 publication of the reports of the various expeditions. 



It is unnecessary to dilate at length upon the maps of mean annual temperature and 

 cloud, as the factors affecting them have been fully discussed under the monthly 

 headings. Attention may, however, be called to the bending of the isotherms south- 

 ward west of 55° W., as a result of the prevailing north-east winds. On the other hand, 

 the crowding of the isotherms on the east side of Graham's Land is very striking. Here 



