346 DISCOVERY REPORTS 



winter slightly over 14° F. The average temperature of February, the warmest month, 

 is 33° F., and that of July, the coldest, 13° F. The highest recorded temperature for 

 summer up to the year 1925 is 52° F., and the lowest for winter —40° F., but both these 

 extremes are highly exceptional and even an approach to them is rare. In summer, 

 however, the temperature frequently rises to about 40° F., and winter temperatures of 

 — 20° F. are not uncommon. While Fohn winds are blowing the temperature, even in 

 vwnter, may rise above 40° F. 



A comparison of these figures with those obtained by Charcot^ at Port Circoncision 

 on the west Graham Land coast shows what a marked efli'ect the Weddell current has on 

 the climate of the South Orkneys. Port Circoncision, though situated in 65° 10' S, 

 64° 14' W, more than 250 miles south of the latitude of the Laurie Island station, would 

 nevertheless seem to have a climate which is actually milder than that of the South 

 Orkneys. Charcot's observations from January to November 1909 point to a mean 

 annual temperature of about 26° F., a mean summer one of about 34° F., and a mean 

 winter of 20° F. The lowest winter temperature he records is only — 11° F. 



The prevailing winds are westerly and south-westerly, 57 per cent of all observations 

 being from those directions. North-westerly and south-easterly winds are also fairly 

 common, the former prevailing in the northern semicircle; but winds from the north, 

 north-east, east and south are relatively infrequent. The warmest come from the north 

 and north-west, the coldest from the south. The winds blow strongly throughout the 

 year, frequently reaching gale force, especially in March and April and in August and 

 September. The calmest months are December, January and June, but all three can 

 be boisterous on occasion. The mean annual barometric pressure is 993 mb. It varies 

 only slightly from month to month but is highest as a rule in winter. The mean annual 

 cloudiness (scale o-io) is 8-5, the South Orkneys being situated in one of the cloudiest 

 regions in the world. The sky as a rule is most heavily overcast throughout the late 

 spring, summer, and early autumn months, that is from November to March. The late 

 autumn and winter skies are the clearest. The relative humidity is extremely high, 

 nearly 90 per cent. Precipitation is heavy and is chiefly in the form of snow, although 

 rain is not unusual in summer. Throughout the year fog or mist is exceptionally pre- 

 valent owing to the meeting of the warm north-westerly and northerly winds with the 

 cold air over the glaciated land or the ice-covered water in its vicinity. 



The observations of the meteorologists on Laurie Island are said to be of the highest 

 value to the Argentine Republic, inasmuch as it has been claimed that the temperature 

 conditions at the South Orkneys in any winter are an index of the rainfall in various 

 parts of Argentina some time later. Fifteen years after the inception of the observations 

 Mossman wrote : 



Generally, the statistical analysis indicates that a very cold winter at the S. Orkneys will be 

 followed after an interval of 3J years by a drought over the great cereal belt of Argentina, a very 

 mild winter by bountiful rains. This remarkable relationship has held good for the past few years, 

 and though the physical mechanism involved is obscure, it is certain that the varying temperature of 



1 See Antarctic Pilot, p. 167. 



