286 Iv. HONDA: ON THE MUTUAL INFLUENCE 



diam. =0.842 cm.; demagnetizing factor =0.0308. 



4. Nickel tube : 



lengtli = 17.02 cm.; external diam. = 1.328 cm.; internal 

 diam. = 1.252 cm.; demagnetizing factor=0.0261. 



During the experiment, it was almost impossible to avoid the 

 change of temperature due to circularly magnetizing current. It 

 was thus necessary at the first step to determine the effect of 

 temperature on the intensity of magnetization of iron or nickel 

 wire between the temperatures 10° C and 100° C. 



An iron wire was heated by passing steam through the si)ace 

 between two co-axial tubes of brass ; it was placed in the 

 axial line of the tubes, and the magnetizing coil was wound on 

 the external tube. The effect of heating on the magnetization of 

 iron is very small, the greatest change amounting only to 0.10 

 C.G.S. units per degree rise of temperature in the field of 21.2 

 C.G.S. units (1 = 1060 C.G.fS. units). In fields less tluui 11 

 e.G. 8. units, it is to increase and above tliat lield to decrease 

 the intensity of nuignetizatiun. AV ith nickel wire, the character 

 of the change of magnetization is similar with that of iron, but the 

 amount of the change is comparatively large. The greatest 

 increase of magnetization amounted to 0.35 C.G.S. units per degree 

 rise of temperature in the field of 7.6 C.G.S. units (1 = 121 C.G.S. 

 units). Thus the change of magnetization due to a small rise of 

 temp)erature may be neglected for iron as well as for nickel. 



The effect of torsional strain of iron or nickel caused by 

 the magnetizing field and the longitudinal current on the inten- 

 sity of magnetization was also carefully examined and found to 

 be negligibly small. 



To study the action of longitudinal current passing through 

 the magnetized wire by the ballistic method, a secondary coil 



