68 Messrs. K. Honda and T. Terada on the 



was so directed that the direct effect of the combined system 

 on the galvanometer was null. To determine the constant o£ 

 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 with sufficient 

 accuracy. But, as the ambiguity o£ 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 secondary circuit and placed at a sufficient distance 

 to be safe from any sensible influence of the magnetizing 

 circuit during the experiments 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 magnetizing current of 

 known strength switched on to the primary coil, and the 

 consequent deflexion 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 secondary circuit was 10*80 12. 



The deflexion of the galvanometer was read by means of a 

 scale and telescope with a scale distance of 1*527 m. The 

 sensibility of the arrangement was such that one scale- 

 division corresponded to a change of 1*42 c.G.S. units of 

 intensity of magnetization. To obtain a smooth motion of 

 the galvanometer mirror due to the induction, it was found 

 , necessary that the two primaries as well as the two secon- 

 daries should have nearly the same dimensions respectively ; 

 the kick, which was observed when the dimensions of these 

 coils were different, was probably due to the self-inductions 

 and the capacities in these coils. 



Compensation for the earth field was effected by a special 

 coil of fine copper wire wound on a glass tube in a single 

 layer. This coil fitted closely to the inside of the magnetizing 

 coil and to the outside of the secondary. It was fed by a 

 current from two Daniel cells with adjustable resistance in the 

 circuit. 



The current in the primary circuit was measured by a 

 Siemens and Halske ammeter with tw T o shunts, ~ and ^. 

 This was occasionally compared with a Kelvin's ampere- 

 balance. 



The specimen to be tested was cut to a suitable length 

 (about 27 cm.) so that, if placed centrally, it might lie in a 

 nearly uniform field of the magnetizing coil ; it was brazed 



