194 KNOTT AND TANAKADATE 



be looked for. It is the more important, then, to have as many differ- 

 ent stations as possible, so that in the final combining- of the results 

 a good selection may be made. This conviction grew upon us more 

 and more as the wc)rk progressed, as may be inferred from the less 

 scattered distribution of the later stations as com[)ared with that of 

 the earher ones. Indeed, only by a much closer distril)ution of sta- 

 tions can we hoi)e to make out anything very definite regarding the 

 magnetics characteristics of the north-east parts of Japan. In the 

 subjoined table are given the stations with their latitudes and long- 

 itudes. The dates on whicli the observations were made will be found 

 in the detailed tables farming Appendix B t(3 the paper. The st;itions 

 are numbered from 1 u[) to 81 ; Nos. 1 to 50 being the Northern Party's 

 stations arranged chronologically, and Nos. 50 to 81 the Southern 

 Party's similarly arranged. In the other tables to be given here, the 

 stations will usually be represented by their numbers. 



After the individual observations were finally reduced, rough 

 charts were prepared showing the broad features of the vari<3us iso- 

 magnetic lines. From these it M'as easy to tel] where the principal 

 centres of disturbance lay. Guided by this and other considerations, 

 a selection of 50 points was made. These are indicated in the four 

 succeeding tables by being represented in thicker type. The co- 

 ordinates of the Mean Station of these fifty chosen stations are: — 



Latitude 36° 30' N. 



Longitude 137° 9' E. 



Referred to this Mean Station as origin, the four sets of fifty ob- 

 servations — representing respectively the Dip, the Horizontal Force, 

 the Total Force, and the Declination — were combined by the method of 

 Least Squares. Tlie results will be discussed in the order just named. 

 For the sake of showing how far the formula deduced from the 50 

 chosen stations is applicable to tiie remaining 31, the various tables 



