MAGNETIC SUEVEY OF JAPAN FOR THE EPOCH 1895.0. 147 



öZ' 

 The Vertical Variation of the Vertical Component —^ is (al- 

 gebraically) 



Maximum at 6 = n i.e. antipode 



Älinimiun at ^/ = i.e. periceuter. 



There is another pair of such points, namely 



Maximum at e = .,.^{^,-1, + J{^f{Ff~,) J ^^ 

 Minimum at = o,«-.(A_i__^/( j; J_(K J^^^ _ | 



the maximum is possible for all positive values of r within 



JlWb'-l) II <r<a, (12) 



(= .78615 h) 

 and the minimum within 



V^(v^5-1) R < 'r<R 



At the lower limit the two values coincide at 



6=^o^-'{ll J l{vr-l)-J IWb-l)) (13) 



=60° 55!8 from the epicenter. 

 The variation vanishes at 



>(14) 



,/ 9 T> I ■> (above 



+ Ö = ain-y_:l -Ell _ sill- V-o- source) 



and ^-^-siii-y|- A_,iii-iyi- 



This is possible for all positive values of r within 



J 'A^Yx{-^.^V^:}OV.) < r <c/j ; (15) 



