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tliey point witli gi-eat reg:ularit3' to the positive foei and fly 

 from the negative ones. 



As the arctic foei ai-e better to ln' repiesented on a map in 

 stereographic piojeetion, sueli a map lias been eonstructed 

 and reprodiiced in tlie phite. 



The two foei of the horizontal vectors of the aretic station 

 and their circular path, iliscnssed above have been introduced 

 as well as the pole of disturbanee, the northend of the 

 magnetie axis of the earth and the magnetic pole, in order 

 to make it obvious, how mnch nearer the pole of distnrbanee 

 is situated to the former than to the latter. 



The positive and the negative focus of horizontal veetors 

 are situated close to the region where the vertical component 

 shows a maximum and a minimum respectively ; the positive 

 one lying between the two maxima, the negative following 

 the minimum. 



On the Cause of the daiiy Field. 



The current vioAV of geophysieists on the fields of foree of 

 daily variation and disturbanee is, that they are generated 

 by currents of an eleetrieal nature, flowiug outside and inside 

 (rf the eartherust. 



If we suppose a eurrentring to exist outside the earth in 

 a plan parallel to its surfaee; then the lines of equal vertical 

 magnetic foree on the surfaee will be eoncentric with the 

 projeetion of that ring. In case the ring moves in its own 

 plan, the course of these lines in regard of the moviug 

 projeetion of the ling will so mueh the more deviate from 

 their original course in conse(|uenee of currents indueed in 

 the eartherust, the larger the rate of its motion and the 

 eonduetibility of the ernst are. 



In ease the primaiy current is not a ring, but if we have 

 to do with a system of currents enelosing various eentra the 

 lines of flow will be so much the less eoneentrieal with those 

 of equal vertical foree i the more inlrieated the svstem is. 



