THE THEORY OF TERRESTRIAL MAGNETISM. 405 



When . = 2, 7,' -(I -/'), V;-(l-p.')fa), 



When m = 3, r,'=(l-f.f, 7/ = (l -^f (,.). 



When m = 4, F 4 4 = (l -/n 2 ) 2 , F 5 4 = (l -tf* fa), 



