312 POLAR PROBLEMS 



northeast. The storm of longest duration during two years of obser- 

 vation lasted no less than 164 hours, with ']'] hours of winds of greater 

 velocity than 21 meters per second. 



At Wandel and at Petermann Islands, on the western coast of 

 Graham Land, the velocity of the wind, as at the South Orkneys and 

 at Snow Hill, is less in summer than in winter, contrary to the case 

 in Tierra del Fuego. The greatest monthly mean, 8.2 meters per 

 second, is much lower than the highest monthly mean at Snow Hill, 

 which was 13.65 meters, but it is of the same degree as at the South 

 Orkneys. The maximum velocity observed in 1909 at Petermann 

 Island was 33 meters per second, whereas during the same year 

 the wind at the South Orkneys did not exceed 23.50 meters. At 

 Petermann Island 19 hours out of 100 hours were characterized by 

 winds of greater velocity than 18 meters per second, whereas at Snow 

 Hill there were only 12 such hours out of 100. 



The gales at Petermann Island all come from the northeast, 

 with a falling barometer. The difference between the gales at Snow 

 Hill, all from the southwest with a rising barometer, and those at 

 Petermann Island, all from the northeast with a falling barometer, 

 although the two stations are very close to each other, is evidently due 

 to the steep pressure ridge that separates them. This difference in 

 direction of the high winds has very important consequences for the 

 climate of the two stations : at Petermann Island the gales, which there 

 come from the north, raise the temperature, whereas at Snow Hill, 

 where they come from the south, they lower it. It is a well-known 

 fact that low temperatures are all the harder to support when the wind 

 is high. 



TRAJECTORY OF THE DEPRESSIONS 



If the mean monthly values of atmospheric pressure at Punta 

 Arenas and in the Antarctic are compared it will be seen that for 

 certain sequences of months these curves resemble each other, whereas 

 for other months they are reversed. It therefore seems that at 

 times Tierra del Fuego and the Antarctic are under the influence of 

 the same center of atmospheric action and at times under the influence 

 of different centers having a seesaw movement in the opposite sense. 

 Although the climate of Patagonia is entirely different from that of 

 the American quadrant of the Antarctic the climates of these two re- 

 gions are seen to be often only the different manifestations of the same 

 cause, provided that one accepts barometrical variations as the deter- 

 mining causes of meteorological phenomena. 



An examination of the hourly values of the pressure shows that in 

 a general way the barometric variations transplant themselves from 

 west to east and that they take from 24 to 48 hours to go from the 

 65th to the 35th degree of west longitude. 



