664 ZONES AND REGIONS [Pt. Ill, Sect. Ill 



low winter temperatures have no such deep significance as, for instance, 

 Grisebach attached to them ; in general they are not so severe as at many 

 points in the temperate zones. Of greater significance to plant-life than 

 the temperature minima are the smallness of the amount of atmospheric 

 precipitations during winter, and the strong gales which blow the usually 

 not very thick layer of snow into heaps and thus sweep it away from 

 extensive tracts of plant-bearing ground. Fatal also to vegetation during 

 winter are both the clearness of the sky, and the occasional atmospheric 

 dryness, which may be so great that even during the severest cold one's 

 breath does not condense and tobacco crumbles to dust. 



Winter is prolonged into the spring months, so that frequently March, 

 and in the North European polar district even April, may bring with it 

 the extremest cold. ' In May the temperature rapidly ascends, and July 

 is always the hottest month, for in August insolation again rapidly 

 diminishes V 



During the greatest part of the three summer months (June, July, August) 

 the sun is above the horizon continuously, for 65 days in latitude 70°, and 

 for 134 days in latitude 8o°. 



The summer temperatures are very unequal in the different parts of the 

 polar district, but are dependent, not so much on the latitude, as on the 

 distribution of land and water and on the presence or absence of warm 

 currents. Nearly everywhere, however, even during the hottest month, 

 July, the temperature of the air is low. Thus, in East Greenland, 3-8° C. ; 

 in Spitzbergen (Nordenskjold), 4-6° ; on the west coast of Novaya Zemlya, 

 4-6° ; at Boothia, at the northern extremity of America, 5*2° ; in Grinnell 

 Land, 2-8° ; at Godthaab, on the west coast of Greenland, 6-6°. The northern 

 coast of Asia is warmer, and the maximum at certain stations is not reached 

 until August ; thus at Tolstonosovskoye (August), 8-8° ; Filipowskoje 

 (August), 10-7°; Ust-Yansk (July), 13-4° C. 2 



The daily range of temperature at five stations between 70 and 75 N. is, 

 according to Hann : May, 5-4° ; June, 4-5° ; July, 2-4° ; August, 2-9° C. 



The temperature of the air, in particular its mean, represents even less 

 than in lower latitudes the amount of heat actually available for vegeta- 

 tion. 'At each pole, which has its six summer months, insolation before and 

 after the solar solstice for $6 days is stronger than at any other point on 

 earth, and during 84 days it is greater than at the equator at the same time 3 .' 

 True it is that the absorption of heat by the atmosphere on its long journey 

 to the poles is far greater than on its shorter one to the equator ; yet the 

 temperature of the air would be far higher than it actually is, were it not 

 that the sun's heat is for the most part expended in melting the masses 

 of ice. 



1 Hann, op. cit., Bd. Ill, p. 173. 2 Id., op. cit., Bd. Ill, p. 515 ; Woeikof, op. cit. 



3 Hann, op. cit., Bd. I, p. 98. 



