296 YOSHIJIRO KA.TO ; 



constant field. He found that when the intensity of field, in which 

 the specimen was kept before the step was made, was great, the time 

 effect became conspicuous, so that when the magnetising force was 4 

 C.G.S., the time effect after 1 minute might be six or seven times as 

 great as the immédiate effect. He also found that when the piece of 

 soft iron was exposed to the action of a constant magnetising force for 

 a long time, the amount of creeping became less in comparison with 

 the immediate effect of the step. He remarks that the amount of 

 creeping much depends on the annealing of the specimen, and, further, 

 that, when the iron is hardened by stretching it beyond its elastic limit, 

 the amount of creeping becomes considerably less. In steel, whether 

 annealed or in its usual temper, he found the creeping to be even 

 less than in hard iron. He adds the important remark that the 

 diameter of the wire has a great influence on the amount of 

 creeping, the latter being less marked in thin wires. A bundle of fine 

 iron wires bound together gave a creeping which was almost negligible 

 in comparison with that of a solid rod of the same aggregate diameter. 

 (It is true that this fact was observed by many experimenters before 

 Ewing, for instance, by v. Helmholtz, 1 but it was Ewing who made 

 it conspicuous that the phenomenon may be observed in the time- 

 lag in magnetisation itself, apart from the effect due to the Foucault 

 current.) 



Another investigation on this subject has been made by Dr. J. 

 Hopkinson and 11 Hopkinson," though in a different manner. They 

 took a bundle of fine wires, of soft iron and hard steel, well insulated 

 from one another, and formed them into a ring, which they subjected to 

 the influence of a rapidly reversing magnetic field. Their conclusion 

 is not very definite, hut amounts to this that up to a frequency of 



1 Pogg. Ann. 83, P- 535 (1851) 



2 The Electrician, 29, p. 510 (1892.) 



