4 APvT. 7. — K. HOlfDA AND T. TERADA. 



connected with the secondary circuit of the system and placed at 

 a distance of about 15 meters from the magnetizing coil to avoid 

 their direct action. The galvanometer was, however, still disturbed, 

 when a strong current was switched on to the magnetizing coil. 

 To prevent this, the compensating primary was so directed that 

 the direct effect of the combined system on the galvanometer Avas 

 null. To determine the constant of the galvanometer, we should 

 have used the compensating secondary coil, if it had been wound 

 in one layer, so that its effective sectional area could be determined 

 Avith sufficient accuracy. But, as the ambiguity of the sectional area 

 in the secondary coil of 6 layers was inevitable, another coil was 

 constructed with a thin copper wire wound on a wooden cylinder 

 of 5.04 cm. diameter, in a single layer ; the number of turns of 

 the coil was 48. This was always put in series with the second- 

 ary circuit and placed at a sufficient distance to be safe from any 

 sensible influence of the magnetizing circuit during the experi- 

 ments for magnetization. When the constant of the galvanometer 

 was to be determined, the compensating secondary coil was 

 removed from the primary coil and replaced by this coil ; then the 

 magnetizing coil for the specimen was shunted off, a weak magnetiz- 

 ing current of known strength switched on to the primary coil, 

 and the consequent deflection of the galvanometer was measured. 

 The constant of the galvanometer was thus determined from the 

 field in the primary coil and the dimensions of the secondary 

 circuit in the usual manner. The resistance of the whole second- 

 ary circuit was 10.80 ^. 



The deflection of the galvanometer was read by means of a 

 scale and telescope with a scale distance of 1.527 m. The sensi- 

 bility of the arrangement was such that one scale division corres- 

 ponded to a change of 1.42 C.G.S. units of intensity of magneti- 



