THE STORAGE OF COLD. 



519 



much importance. Were it not for the snow-fall the problem of 

 climate would be materially modified, and the temperature of the 

 earth's surface much ameliorated. The seasons would gain a regu- 

 larity which they do not now possess, the agricultural period of 

 the colder zones be much extended, and the domain of agriculture 

 be considerably widened, by the recovery of broad regions which 

 are now covered during much or all of the agricultural season 

 by snow. 



In the winter the frost-laden strata of the atmosphere descend 

 to the surface over much of the globe, and produce a direct re- 

 frigerating influence upon the surface soil and waters. This win- 

 ter freezing, however, is of minor importance, as it, except in the 

 polar regions, quickly yields to the spring suns, while its influence 

 upon the summer temperature of lower latitudes is but slight. 

 Only for the snow-fall this would be our sole source of cold. But 

 the vast blanket of snow which descends annually upon the colder 

 zones conveys downward the severe chill of higher layers of the 

 air, borrowing from a mighty storehouse of cold which broadly 

 impends above the earth. This snow blanket must be removed, 

 and its stored cold overcome by solar heat, before agriculture can 

 begin, and in this process weeks or months pass away, the effect 

 being greatly to reduce the area of the earth's surface which is 

 suitable for human habitation. 



The snow of the frigid zones does not wait for the sun to reach 

 it. It travels toward the tropics to meet the sun. This creep of 

 the snow, as we may call it, takes the forms of the glacier and 

 the iceberg. It also acts in another curious method, not generally 

 known, but which is described by Nordenskiold, in his Voyage 

 of the Vega. Speaking of the natural conditions at a winter 

 station near Bering Strait, he says : " The fall of snow was not 

 great, but, as there was in the course of the winter no thaw of 

 such continuance that the snow was at any time covered with a 

 coherent melted crust, a considerable portion of the snow that 

 fell remained so loose that with the least puff of wind it was 

 whirled backward and forward. . . . Even when the wind was 

 slight and the sky clear, there ran a stream of snow some centi- 

 metres in height along the ground in the direction of the wind, 

 and thus principally from northwest to southeast. . . . The quan- 

 tity of water which in a frozen form is thus removed in this 

 certainly not deep but uninterrupted and rapid current, over the 

 north coast of Siberia to more southerly regions, must be equal 

 to the mass of water in the giant rivers of our globe, and plays 

 a sufficiently great role among others as a carrier of cold to the 

 most northerly forest regions to receive the attention of mete- 

 orologists." It may be that a similar condition prevails over 

 northern America, though concerning this we have no evidence 



