( 314 ) 



Later considerations ') bi'o light ine to the result that the regular 

 part of the disturbance phenomenon might be ascribed to the existence 

 of a circular system of electric currents chiefly in tlie higher layers 

 of the atmosphere, compassing the earth, and parallel to the lines of 

 equal frequency of aurora borealis. 



Considering with Schmidt -) magnetic disturbances to be caused by 

 movement of smaller current-rings over the surface of the eartli, the 

 whole exhibits a strong analogy to the great cyclonic movement of 

 atmospheric air around the poles and the wandering depressions 

 within it, so as it has recently been described by H. Hildebrandsson, 

 It seemed evident that such a system of circular currents must 

 undergo a daily fluctuation caused by the rotatie »n of the earth 

 and I tried to separate this influence by taking the difference of 

 corresponding hourly values on days following a magnetic disturbance. 



Though the results pointed to an influence indeed, they were too 

 vague to lead to definite conclusions; the minuteness of this daily 

 fluctuation as compared \\'\\\\ tlie irregular changes accompanying 

 magnetic disturbance being no doubt the cause of it. 



Now in 1899 Dr. Lüdeling ') showed that sharp results were to be 

 obtained, Avhen comparing the hourly values of the horizontal com- 

 ponents on quiet days (Kormaltage) with those for all days. In his 

 interesting paper he gives the liourly values of the horizontal com- 

 ponents {.Ks and ?/,.) of disturbing force for the arctic stations for the 

 months June and July 1883. 



The vectordiagrams drawn by iiim show the remarkal)Ie fact that 

 the vector for all stations moves anticlockwise, with the oidy excep- 

 tion of that for the station Kingua Fjord where tlie vector moves 

 decidedly in a clockwise direction. Also at Godthaab during part of 

 the day the same occurs. 



In order to study these diagrams for other })arts of the earth 1 

 computed them for Greenwich, Washington, Tiflis, Zi-Ka-Wei, Batavia, 

 South Georgia and Cape Hoorn for the same months (June, July) ; 

 also deriving on the same princijiles the x-ertical component for 

 these latter stations and the arctic ones, I found this component to 

 exhibit chieflv a single dailv fluctuation of an amount of the same 

 order as that found for the horizontal component. 



It was easy to classify the stations in the following groups: 



^) Terrestrial Magnetism V, pg. 123. 



2) Meteorologische Zeitschrift 1899, pg. 385. 



^) Terrestrial Magnetism IV, pg. 245. 



