208 KNOTT AND TANAKA.DATE 



mean probable error comes out ±13' A. There are three Stations, 

 however, which have such large differences that, when they are 

 neglected, the me;ai probable error is reduced to ± 8'. These Stations 

 are Miyako (No. 10), Hakone (No. 41) and Pusan in Korea (No. 

 (64). The manner in wliich the declinations at these Stations di- 

 verge from the values given by the formula suggests local disturbances 

 of quite a limited area of action. This is peculiarly true of Ilakone 

 (No. 41). That the disturbance at Pusan (No. 64) is of quite a 

 local character is proved by the fact that at the contiguous stati(jns 

 (Nos. 62 and 63) the differences are comparatively small. Miyako 

 (No. 10) is another striking instance, for Avhich, liowever, no certain 

 conclusions can be drawn as, unfortunately, «observations at neigh- 

 bouring points were not taken. 



This whole region indeed, lying loetween the tliirty-eighth and 

 forty-first parallels of latitude — and more especially the centra] and 

 eastern portions of it — seems to be one of marked magnetic disturb- 

 ance. It is highly volcanic and contains nearly a score of distinct 

 volcanoes, of which four are especially prominent. These are* Iwaki- 

 san ( 5,260 ft. ) in the northwest near Hirosaki ( No. 20 ), Ganju-san 

 ( 7,000 ft. ) in the centre near Morioka ( No. 9 ), Moriyoshi-san (5,800 

 ft.) to the south of Odate (No. 21 ), and Chökai-san (7,100 ft. ) to 

 the north of Sakata ( No. 28 ). This great spread of volcanic rock, 

 however, is confined entirely to the Central and Western portions. 

 The Kita-kami Hiver, which flows from its sources a little to the 

 north of the fortieth parallel due south to Ishinomaki (No. 6), is 

 virtaallv the dividins: line between the volcanic and non-volcanic 

 deposits. In the hilJy country t(3 the east of tliis river the rocks are 

 largely schists and granites. Nevertheless in this part also the dis- 



* See Professor Milne's " The Volcanoes of Japan," Transactions of the Seismological 

 Society of Japan Vol. XI. ( 1886). 



