of Energy in the Atmosphere, 457 



mean velocity of the air, corresponding to this valne of vis 



C=a/- i -^ = 379 m. per second. 



viva 



This is the velocity corresponding to the 35th degree of 

 latitude. 



If we now imagine the whole atmosphere suddenly in- 

 timately mixed in such a way that each particle should have 

 assumed the above mean velocity, then the air from the 

 equator up to the 35th degree of latitude must rotate slower 

 than the earth's surface, but in higher latitudes, on the con- 

 trary, faster ; under the equator itself this difference in 

 velocity would be 84 metres in the direction from east to 

 west, at 45°, 59 metres, and under the 54th degree of latitude 

 107 metres in the direction from west to east. By friction 

 with the earth's surface this difference of velocity would 

 gradually be destroyed again if no currents of air in the 

 direction from the equator to the poles, and in the opposite 

 direction, were produced. Since these currents, however, 

 always do occur, a condition of equilibrium must result, in 

 which the mixture of the more rapidly ro eating equatorial air 

 with the more slowly rotating polar air is so far accomplished 

 that the accelerating friction of the equatorial zone up to the 

 35th degree of north and south latitude is equal to the re- 

 tarding friction of the rest of the earth's surface. Hence in 

 the whole atmosphere of the equatorial zone east winds must 

 prevail, and west winds in the regions lying north and south 

 from 35°, and moreover the preponderance of the west winds 

 must increase with the latitude *. 



We will now consider the hypothetical case, that the earth 

 is a smooth solid globe of homogeneous surface, and that the 

 water contained in the atmosphere is vanishingly small. Then 



* I regret that the recently published Handbook of Dr. A. Sprung has 

 only reached rne a short time ago, from which I learn that Ferrel, from 

 similar observations, has also designated the 35th degree of latitude as 

 that above which the whole of the air-currents must have a meridional 

 direction. I cannot, however, adopt his view, that in consequence of 

 the retarding friction of the air on the surface of the earth the position 

 of this zone must be displaced towards the equator. Friction at the 

 earth's surface can, according to my view, only diminish the difference 

 in velocity, that of the lower equatorially directed current of air, but not 

 the place where this difference between the velocity of the earth and air 

 is zero. It is evidently the endeavour of the author of this important 

 work to furnish a mechanico-physical foundation for meteorological 

 phenomena, and he has therefore frequently arrived at conclusions 

 similar to those presented here. It is unfortunately not possible for me 

 to examine further the, in some respects important, differences between 

 us. 



