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BELL SYSTEM TECHNICAL JOURNAL 



different measure is desirable, having a homogeneous standard of 

 evaluating magnetic activity from year to year and for all time. This 

 standard measure was called "m," from which was derived the "wi" 

 measure used in this paper. 



Ui Measure 



"A short definition of u may be repeated as the average change, taken 

 without regard to sign, measured in the unit 0.0001 c.g.s, = IO7, of the 

 daily means of horizontal intensity on the magnetic equator of the 

 earth. The monthly means of Mi are derived from those of u: 



-10 -8-6-4-2 2 4 6 8 10 



DEVIATION OF 60-KILOCYCLE TRANSMISSION IN DECIBELS 



Fig. 9— Correlation diagram of scattering from mean of daily averages of radio 

 transmission over all-daylight paths for the 254 days from May 5, 1931 to March 31, 

 1932, when GKA-GBY (Rugby, England) was transmitting on 68 kc. and WNL 

 (Rocky Point, N. Y.) was transmitting on 60 kc. 



