224 



KNOTT AND TANAKADATE 



The value of the Horizontal Force on the top of Fiiji-yama is 

 ahout 5 per cent snialler than wc^uld l)e the case at a normal station 

 at its hase. In the ahsence of measnrements of Dip it is inipossihie 

 to interpret the result. The vahie for Sai)poro is distinctly smaller 

 than the value ohtained hy us ; hut it would hardly he safe to draw 

 any conclusion from their comparison. The other stations lie quite 

 outside the region surveyed hy us. We may however compare the 

 measurements made with the values given hy means of the mean 

 formulae which have heen calculated. Tlie results nre g-[\en in the 



fdlowinsr tahle 



Dip. 



Kao'oshima 45° 55'. 4 



Naha 40 13 1 



l)onin 



Horizontal Force. 



.8170 

 .3396 

 .3262 



Declination. 



3° 47'.2 

 2° 11'.5 

 r 43'. 6 



If we compare these calculated values with the ohserved values 

 given ahove, we see that jSFaha stands the test hest, at least so far as 

 the Horizontal Force and Declination are concerned. Especially as 

 regards the latter, Naha tits in fairly well into the general system. 



The circuit of Stations at which Mr. Schiit t made his observations 

 in 1880 may he said to touch our route in only one place — and that 

 a very exceptional place, namely, Hakone. A general comparison, 

 h(^wever, of the mean values for the district is possible. Thus the 

 Dips give a mean of 49° 41' — about half a degree greater than what 

 is indicated by the isoclinic lines as shown on our chart ( Plate YIII) 

 The mean of the declinations is 4° 19' — about 10' smaller than the 

 value as given by the mean formula, 'l'hese ditferences are of a 

 magnitude in no way extraordinary, seeing that the district is so highly 

 volcanic. Hence how much of these ditferences may be referable to 

 secular variation during eight years, it is quite impossiI)le to say. The 



