THE WEDDELL QUADRANT AND ADJACENT AREAS. 107 



this meridian of 10° E. the summer isotherm of 34° is located only 540 miles from the 

 North Pole, but, as we have seen, quite 2300 miles from the South Pole. Such is the 

 great effect of the Antarctic drift-ice in the lowering of temperature. 



With reference to the characteristics of the strictly Antarctic climate, which form the 

 principal theme of this memoir, 1 may briefly summarise the conditions as follows. 

 Stations such as the South Orkneys, Port Charcot, and in a less degree Snow Hill and 

 the south of the Bellingshausen Sea, are strongly influenced by the ocean to the north. 

 At these places great variations of temperature and weather occur, especially in winter, 

 according as the influence at work is continental or oceanic. With southerly winds the 

 skies are clear, the air dry, and the temperature low ; but with a change to the north, 

 exactly the reverse conditions obtain. For this reason the summers are much cloudier 

 than the winters, and it is then that the maximum precipitation occurs. The tempera- 

 ture does not fall so low as one would expect — from — 40° to — 45° F. The maximum 

 temperature depends entirely on the situation. In the open sea or in the pack it rarely 

 rises in summer more than 2 or 3 degrees above the freezing point, but near the 

 land it may rise to 40° F., and at stations such as the South Orkneys and Snow Hill 

 (which are subject to occasional visitations of fohn) the thermometer may rise even in 

 winter to from 45° to 50° ; however, these high temperatures rarely last more than a few 

 hours. In the matter of sunshine, great differences are found, — Port Charcot in 1904, 

 for instance, recording 32 per cent, of the possible, with 140 sunless days, while at the 

 South Orkneys only 13 per cent, was registered, with 189 sunless days. 



In this connection I have prepared a map (see PL IV. fig. 5) showing the mean tem- 

 perature of the sea surface in summer. In the preparation of this I have employed all the 

 existing material. The bending of the isotherms to the north is clearly shown ; also 

 the higher temperature of the sea near the South Shetlands and to the west of Graham's 

 Land, due to the north-east winds driving the warm surface waters before them. It 

 may be incidentally mentioned that, as one would expect, there is a close relation 

 between the summer sea temperature and the distribution of fog. Fogs are compara- 

 tively rare between 40 and 50° S., west of 30° W., but between these latitudes, from 

 30° W. to the meridian of Greenwich, fog is very frequent, amounting on the average 

 to 13 per cent, of the observations. The indirect effect of the southern ice is apparent 

 even to the north of latitude 40°, a little to the west of the meridian of Greenwich, on 

 which longitude the greatest northern extension of the polar water occurs. (See plate 

 vii. of Captain Campbell-Hepworth's paper " On the Relation between Pressure 

 Temperature and Air Circulation over the South Atlantic Ocean," Meteorological Office, 

 London, 1905, official No. 177.) 



Having described the broad climatic features, I now proceed to deal with the 

 months in detail. 



In January there are two well-defined areas of low pressure ; one to the west of 

 Graham's Land in about 64° S., the other over the Weddell Sea. Round the western 

 low-pressure area the winds blow spirally inwards, being N.W. in lat. 60° S., long. 70° 



