60 HOBBS— CHARACTERISTICS OF THE [April 22, 



Within the northern hemisphere a large quantity of heat from 

 the tropics finds its way northward to the breaks in the northern 

 land chain, through the medium of great ocean currents — the Gulf 

 Stream in the Atlantic, and the Japanese Current in the Pacific. 

 Cold return currents from the Arctic region, and the widely dif- 

 ferent specific heats of land and water, cooperating with the effect 

 of the northward flowing warmer currents, result in a marked 

 diversity in temperature, winds and precipitation at different longi- 

 tudes within the same latitudes. Lack of symmetry in distribution 

 and wide variations in climatic conditions are, therefore, character- 

 istic of the north polar region ; and it follows that the present 

 glaciation of the northern hemisphere is localized within a few 

 scattered areas where the land projects farthest toward the pole 

 and near where there are sea areas of excessive evaporation to sup- 

 ply the necessary moisture. 



TJic Fixed Areas of Atmospheric Depression. — Examination of 

 Fig. I will show that the areas of existing heavy glaciation in the 

 northern hemisphere lie close to the so-called fixed areas of low 

 barometric pressure, each of which is a long, curved trough, con- 

 cave to the northward, one central over the Aleutian Islands' Arc 

 at the northern bay of the Pacific Ocean, the other extending from 

 the southeastern extremity of Baffin Land past Cape Farewell, 

 and northeastward across Iceland, so as to occupy similarly the 

 northern bay of the Atlantic Ocean. For such northern latitudes 

 these areas of fixed low barometric pressure are in consequence 

 characterized by abnormally large evaporation. Wherever the 

 moisture-laden winds proceeding from these areas are forced to 

 rise by upland barriers, or to come in contact with cold rock or 

 snow surfaces, condensation and precipitation must inevitably take 

 place. 



The prevailing westerly winds from the Pacific, when they 

 encounter the high backbone of the Cordilleran System of moun- 

 tains in Alaska nourish the great mountain glaciers of that region. 

 The Cordilleras of Alaska are, however, competent to arrest but 

 a small portion of these moisture-laden clouds, for it is only in 

 moderate latitudes that they bar the way, and no highlands lie 



