PART III. EARTH CURRENTS AND EARTH MAGNETISM. CHAP. 



II., 



-f 



(cos 9 cos cos ft) [0 - (A '/) cos 

 sin- ft . d 



\ 

 f i) \k\. R is very small. 



In accordance with equation (7), we then have 



P ."2 



= -'/ if 

 * <*'} } 



[cos cos cos ft] [g (L d) cos ft] 

 " 



" 2 



sn 



."1 



hat is, 



i dif 



*-Trf*J 



cos 6 cos 'C cos ft r 



__ !_ I /r 



(16) 



The integration could be carried further, but the above form is the most practical for the numerical 

 alculation. 



For the current-components /^ and im , we find 



infl 3/.< 



hat is 



nd 



psinfl x 



i 3(/< i 



- -- 



cos cos cos ft 

 sin 2 ft 



ft = //-j 



. [g cos ft -f rf L] 



cos ft + rf Z. 



L 



"1 



vhere we have put 



3 cos cos cos ft _ sin 2 8 + (cos 6 cos ft cos ) cos 



36 sin 2 ft 



sin sin 2 ft 



2 (cos cos cos ft) (cos 6 cos ft cos ) cos ft 

 sin 8 sin 4 ft 



nd 



cos 6 cos L cos ft 3 cos ft (cos 6 cos cos ft) (cos 9 cos ft cos C) 



sin- ft 30~ sin 2 /? sin fi 



sin 2 ft sinfl 



'or the magnetic potential V t , we have, according to equation (14), 



(I?) 



(20) 



o o 



Ve now have 



