140 BAUER— SOLAR ACTIVITY AND [April 23, 



According to the theory of magnetic disturbances as set forth 

 above, the various manifestations of solar activity zvith their result- 

 ing emanations and radiatiotts are not the direct but the indirect 

 cause of the earth's magnetic storms. Their effect appears to be 

 more in the nature of a releasing or trigger action, setting in opera- 

 tion forces already in existence in the upper regions of the atmos- 

 phere; terrestrial sources, in reality, however, supply the energy 

 required for a magnetic storm. To connect then the zuell-estab- 

 lished, general relationship between magnetic disturbances and the 

 sunspot period, zve nfust suppose that the radiations zuhich alter the 

 conductivity of the atmosphere vary in their amount and intensity 

 in accordance zvith the periodicity of the solar phenomena. 



In the above theory of magnetic disturbances we had to depend 

 on an already existing electric field. If we analyze the results of 

 magnetic observations made at various points over the earth's sur- 

 face, it is found that about 95 per cent, of the measured magnetic 

 force can be accounted for by an internal magnetization of the 

 earth or by an equivalent electric current system in its interior. 

 The outstanding 5 per cent., however, can only be due to an electric 

 field in the atmosphere. 



A preliminary examination discloses the possibility that these 

 atmospheric electric currents may be ascribed to Foucault, or eddy 

 currents, induced in the more or less conducting layers of the 

 atmosphere as, during its general circulation around the earth, the 

 air currents are made to cut across the earth's lines of magnetic 

 force. 



The general atmospheric circulation consists in the main of two 

 great atmospheric whirls, the one in the middle and higher latitudes 

 of the northern hemisphere whirling around the north pole in a 

 counter-clockwise direction supposing we are looking down on the 

 north pole. A similar whirl exists in the southern hemisphere ex- 

 cept that, if we could look down on the south pole we would see 

 that the whirling is done in the clockwise direction. Could we, 

 however, look at the two whirls in the same direction, for example, 

 from the south pole to the north pole, then the motion would be in 

 the same direction for both, viz., clockwise. 



