— 245 — 



Accordiiig' to the rosults obtained liere we may suppose as 

 a tirst approxiniation, tliat the daily field of disturbing force 

 is g-enerated by the existciice of a systeni of currentrings 

 enclosing eight foei. 



As the horizontal vectors point to the foei of maximum 

 component, directed to the zenith, tliis system of eurrents, 

 according to Ampère' s nile. must be situated chiefly outside 

 the earth. 



When a eurrentiing moves centrally over a place, the 

 influenee of induction into the earth is such, tliat the extreme 

 value of the vertical component for that place occurs after 

 the moment the centrum passes, the horizontal component 

 vanishing before this moment. 



From the representation of the field for the arctic calote 

 we may conclude, that the negative focus and the minimum 

 (—47 7) of vertical component behave in a quite contrary 

 way, the latter preceding the former. 



For the positivo region of vertical component the doublé 

 focus makes any result ambigeous. In how far this may be 

 understood to be an objection against the hypothesis of electric 

 eurrents is quite uncertain. 



iScHUSTEH remarks that the course of the equipotential lines 

 of his field of daily variation, constructed after terms of a 

 lower degree of the series in which the potential-function has 

 been developed, will deviate only slightly ft om the course 

 of electric flow, which may be supposed to be the cause of 

 the production of the field. 



Accordingly it is allowed to compare directly the lines 

 of equal vertical force, drawn here for the field of disturbance, 

 witli the equipotential lines of the field of daily variation as it 

 has l)een constructed by von Bezold ^) after Schustek's 

 calculations. 



The most striking difference may be said to be, that the 

 areas of positive and negative potent ials of daily variation are 



1) SitzHng>fheyich(c dvr Akiuleinie za Berlin, 18Vt7. p. -JTl. ïafcl III. 



