MAGNETIC SURVEY OF .JAPAN. 



223 



angle of dip. In the other expeditions the dip was not measured. 

 Excepting at the Donin Islands the horizontal force was measured by 

 swinging various magnets which had been already swung at Tökvö, 

 and which were again swung at Tokyo on the return of the Party. 

 The declination was observed at Kat^osliima and Xaha bv means of 

 an ordinary theodolite needle, the compass card being graduated only 

 to half-degrees. At the Bonin Islands, however, the measurements of 

 the horizontal force and of the declination were of a much hiüher order 

 of merit. Here, indeed, Mr. Tanakadate used his first form of electro- 

 magnetic declinometer ; and carried out complete series of deflection 

 and vibration experiments for the determination of the horizontal 

 force. The accounts of these various determinations are sriven in 

 the Memoirs of the Science Department of tlie Tokyo University 

 (Nos. 5 and 7) and the several Appendices to Xo. 5. For the sake of 

 comparison the results are here reproduced. The Horizontal Forces 

 as given for all except Bonin are calculated on the assumption that 

 the Horizontal Force at Tokyo was .2964. This was the value ob- 

 tained by the Bonin Island Party before they started on the expedition, 

 and agrees perfectly with our (jwn value. 



The latitudes and lon^^itudes of the last three stations are as 



follows 



Latitude N. 



Kagoshima 31° 35' 30" 



Naha 26 12 6 



] 



)onin 



27 4 11 



Longitude E. 



130° 30' 10" 

 127 40 

 139 45 45 



