THEORY OF CYCLONES VON BEZOLD 347 



from the northwest in the southern hemisphere, and then gradually 

 into a nearly true west wind. At the same time its velocity 

 increases as it advances into higher latitudes, according to the 

 theorem of the conservation of areas. At and beyond a certain 

 latitude the' centrifugal forces thus developed overpower the influence 

 of the temperature which would cause a steady rise of atmospheric 

 pressure toward the poles, so that this pressure which at first 

 increased with distance from the equator now diminishes from this 

 latitude onward very nearly up to the pole itself. Thus arise two 

 belts of high pressure which the averages show as nearly continu- 

 ous but with easily recognized separate nuclei, but which the 

 individual charts show as broken up into many parts. 



These two belts of high pressure are regions of descending currents 

 as is recognized by the clouds. 



Moreover, here the movements of the air are feeble since the kinetic 

 energy is materially diminished by reason of the enormous change 

 in section that the air currents experience in their transition from 

 horizontal to vertical motion. 



The trade winds blow on the equatorial sides of the two belts of 

 high pressure except at the point of interruption introduced into 

 the whole system by the monsoons; on the polar sides, at least at 

 great altitudes, the conditions are fulfilled that according to Helm- 

 holtz must give occasion for whirlwinds to originate. 



Thus in these regions cyclone follows after cyclone separated 

 from each other only by ridges of high pressure as they are carried 

 eastward in the great whirl that surrounds the pole. But the anti- 

 cyclones are portions of the ring of high pressure and the tempera- 

 ture conditions are an important consideration in determining the 

 locations of their central portions in so far that they always seek 

 relatively cold regions and therefore in summer and in low lati- 

 tudes rest on the sea, but in winter and in high latitudes on the con- 

 tinents. 



To these conditions is to be ascribed the fact that the ring of 

 high pressure in the southern hemisphere shows very closely the 

 form that is to be expected according to this theory, whereas that 

 of the northern hemisphere appears greatly modified. 



Especially does the influence of the great Asiatic continent make 

 itself felt to such an extent that the nucleus of the great Siberian 

 anticyclone is pushed about 25 north from the latitude at which 

 the average atmospheric pressure for a whole circle of latitude 

 attains its maximum value. Whereas this value both in the annual 

 mean and also in the extreme months falls nearly on the 35th 



