M 



AGNETIC SURVEY OF JAPAN FOR THE EPOCH 1895.0. 141 



With these vahies the vertical variations at the mean point, 

 i=7°.lG and ç = 48°.G2, come out: — 



^i^ = - 7;!) -^ = - à -^ = + i'^>^ 



-(3h/R)X =- S.2 -(3b/R)Y = - 3.0 -(31./R)Z ^+20.1 



Diff. =~rä3 Diff. =+ O.l Diff'. =- -2.1 



He mio-ht have thns inferred the seat of the terrestrial magnetism 

 to lie chiefly inside the earth, even before nndertaking that 

 labourions series of computations which brought to light the 

 real state of the oeomagnetism for the first time. 



§ 13. Disturbances in the Vertical Variations of 

 Magnetic Force. 



The vertical variations of the terrestrial magnetic force 

 treated in the last section, differ from -(;3h/R) times the respective 

 components in all the three cases. The magnitudes of the dif- 

 ferences are greater than what can be accounted for l)y observa- 

 tional errors, being much larger than the quantities concerned 

 in the determination of the vertical current ; and their distribu- 

 tion is more uniform than those of the current in each country. 

 Any one by taking observations at a dozen of well selected 

 stations will reveal the fact if the same line of calculation be fol- 

 lowed ; as is suggested by the general resemblance of results 

 obtained from observations of three points in Europe with those 

 obtained from complete surveys in the two other countries. 



These are no doubt due to the existence of higher harmonics 

 in the sense of that expansion. From a physical point of view 

 the irrea-uhirities in the surface crust of the earth, as observed 

 in the upheavals of continents and depressions of ocean beds, 



