OF FERROMAGNETIC WIRES BY MAGNETIZATION. 



By making use of Fig. 1, the curves showing the relation between 

 the change of length and the tension under a constant field are drawn 

 in Fig. 2. We learn from these curves that the effect of tension on 

 the magnetic change of length is not linearly related to tension. 



Generally speaking, these results coincide with those of Bidwell. 

 In our case, the reduction of the initial elongation by tension is flu- 

 greater than that in Bidwell's wire. The smallest tension, by which 

 the elongation vanishes, is about 4 times greater for the latter case 

 than in the former. The discrepancy perhaps arises from the fact that 

 our specimen is comparatively soft as regards the magnetic quality ; 

 this inference w^as actually verified in the case of wolfram steel. 



Some observed changes in length under different tensions are 

 exhibited in the following tables : — 



Here T is the tension per square millimeter, H the external field, 

 and -J- the elongation of the wire. 



