( .•^J8 ) 



course llic })rincipcil aim), I lui\'e cliosen as represeiilative for each 

 group oue station with au obviously regular diagram. 



They are : Kingua Fjord, Jan May en, Sodankyla, Greenwich, 

 Titlis, Zi-Ka-Wei, Batavia, Cape Hooni, (Godthaab has been left out, 

 it being rather su})ei-fluous foi' the horizontal component, and the 

 vertical component not being available). 



The values of the components have been graphically smoothed. 

 Now to obtain a re])resentation of the daily field the method at 

 present common of distributing the successive hourly values for each 

 station along the parallel of that station, has been a])|)lied, and thus 

 I have constructed a map in ^Iercatok's projection hut. ncconliiui to the 

 axis of disturbance, witli the lines of ecpial xerlical c()m])()ncut and 

 horizontal vectors on it. 



The lines of equal vertical component compass chielly eight foci 

 of maximum and mininuun vertical force (of which two are double), 

 tabulated hereafter. (It should be kei)t in mind, that latitudes and 

 longitudes are according to the axis of disturbance). The longitude 

 of the sun for its position on June 21^* has been taken zero. 



Latitude Longitude Amount Latitude Longitude Amount 



.77° 6 E +57"/ ) 



71° 161° W -47 y !.^o 81 E +56 J 



. 52 156 W + 7 



I f^9 



+ 567 

 52 88 E —11 



52 131 W + 7 



-10 41 W +3 22 129 E - 1.5 



South of -60 V W -? South of -60 ?E + ? 



The hoi'hoiila] rirtors draint in tlw. saim' map ai-e j)0///t/i/(/ ahnost 

 irithout c.rci'ptioji toirarJs the jjositirc foci and <nnni froui the 



iK't/atii'e ones. 



Supposing the disturbing force to originate from existing electric 

 currents, the fact that these curi-ents must follow nearly the course 

 of the lines of equal vertical fores conducts to the hypothesis of 

 systems of circular currents with eight foci revolving daily around 

 the axis of disturbance. 



The horizontal vector being directed to the i)oiiit where the vertical 

 component is ui)wards, the application of Ampere's rule teaches that 

 these currents must How for the greater part abo\e the surface of 



the earth. 



Remarkable is the rapid diinimition of the force with the polar 

 distance, almost parallel to the equally rai)id diuiinution in the 

 occurrence of auroral display. I must emphasize an iuipoi-lant 

 di\'ergence between the fields of ordinary daily variation aud that 



