THE THEORY OF TERRESTRIAL MAGNETISM. 431 



20. Example of the application of these formulae. 

 Suppose n = 6, w t = 4 and m = 2. 



Then 



Hence ^' = (1 - M f ^ = 2/*(l -/*')'- 2/t(l - 



also 



and Z 4 - 5 (1-fi 1 ) **'- 



But by formula for X?, we have 



= (1 /u, 2 )' -I 4/A 3 fj, >- , which agrees. 



Also 



