THE DISTURBANCE OF ISOMAGNETICS. 153 



due to the ends of the solenoid is up and down, and consequently 

 it gives no deflection so long as there is no substance in tlie 

 solenoid. This position was determined experimental 1}^ by passino- a 

 strong current through the solenoid. The soil to be experimented 

 upon was filled into a glass tube which had been tested and f(3und 

 to be sensibly free from magnetic matter. The inner diameter of this 

 tube was 1.3 cm. and its length 19.55 cm. When introduced into 

 the solenoid, its lower end wns brought nearly level with the mao-ne- 

 tometer, so that only the upper half of the solenoid was used. The 

 magnetometer deflection was a maximum when the lower end of the 

 glass tube was slightly below the level of the magnetometer, and in 

 tili s position the reading was taken. Taking tlie deflection as propor- 

 tional to the strength of the pole induced by the field, and applying 

 the correction due to the upper pole, the susceptibility was easil^^ 

 deduced. The only soils that gave any sensible susceptibility were 

 those of Numazu and Shimizu, two stations which are so far east of 

 the region under consideration that they do not come into the chart 

 of isomagnetics at the end of this pnper. The results of the deter- 

 minations are as follows : — 



Soil from Nnmazu Station. 



Soil from Shimizu Station. 



It is remarkable tliat these soils seem to be far from beino- 



o 



saturated in these fields. 



In the following description of stations we give the geological 

 nature of the soils.* 



* We are iiide1»teil to Mr. Y. Kikuchi, Assi-st. Prof, of Geolog-y, for giving this information 

 about the soils. 



