108 A. TAN AK A DATE. 



Hongkong 114'" lO.T) 22° 1S.'2 36837' -207 

 Zikawei 121° 2."):8 31° ll.'Ö 32908'' 

 Hankow 114° 17:5 30° 35:5 33922" 

 Sjasi 112° 14(8 30° 18!! 34112^ 



which give approximately at ;. = 116.°3 ^=28.°0 



-;r- = — 1/.8 -„-= — 1.4 -;r- =16. 2 per kilom. 



dz oz dz ^ 



(3h/R)X = -16. 3 (3h/R)Y=-0. 2 (3h/R)Z=14. 1 



sx\ , . ny , „ fiZ' 



wliilo those due to the image 



m = -AAlx\0'', o = IlSO kilom, ^ = G,° give 



9X' T. f)Y' OZ' 



-^- = - 10. ' 6, -. = 0.0, -V = + 1 1 . ' 5 per kilom. 



dz ' Oz ' Oz ' 



differing from the ol)served vahies by more than five times. 



Taking the second supposition, that the distribution is re- 

 presented by varying image, we see that it is nearly proportional 

 to the cube of the distance /> : — 



I. II. III. IV. V. Mean. 



711 



,=-1.96 -1.26 -1.24 -1.62 -1.75 -1..57xlO-i» C.G.R. 

 /'■ 



This makes m at the point / = 116'.°3E. ^-=.28°N. 



-1.57 X 10-"'x (1.18)"x 10-' = -2..")S x 10'^ C.G.S 

 and the variational anomalies 



nX' -' rïV ■' i)'L' 



f)'; 9,i bz 



* Tökj'ö Sngaku-buturigakkwai Jlokoku Vol. II. p. 4<i, 



