349 



with the marked end of the deflecting bar to the East and to 

 the West respectively. The value of the constant k is given 

 by the formula 



1i — \\ +- j tan0; 



denoting the angle corresponding to one division of the 



scale, and — the ratio of the torsion force to the magnetic 



force. When the mirror is employed, the formulae of re- 

 duction are similar, if only we substitute 2 m and 20 for u 

 and %. The following Table gives the values of the constants 

 employed in the reduction: 



The following Tables contain the calculated results: the 

 values of ^(«e— ««,) are corrected for the changes of declination 

 which occurred in the interval of the two readings tie and «„^. 

 Series I. and II. 1 = 1' ■= '5. 



Series III. and IV. / =z -5, I' = .375. 



2 G 2 



