1881.] 



583 



[Chase. 



119. Magnetic Correlations. 



In studying the above table for a proper interpretation of its indications, 

 we can follow no better clew than the known correlations of electricity 

 and magnetism, which may be classed under the following heads : 



a. Friction. — Thermal and tidal currents, combined with the resistance 

 of the Earth's surface, must produce atmospheric friction. 



