440 



Mr. R. Shida. 



magnetisation is greater in the case of " Off" than it is in the case of 

 " On." Comparing the curves (<x) and (&) in the Diagrams I, II, 

 and III, we notice a vast difference for low magnetising forces between 

 the intensity of magnetisation of the pianoforte wire and that of the 

 s^ft iron wire ; but seeing that when the magnetising force is so high 

 a; 30 units or so (when the permanent effect of "Ons and Offs " begins 

 to be insignificant, that is, when retentiveness gets inconsiderable), 

 the intensity of magnetisation of the steel wire is very much the same 

 as that of the soft iron wires, I think it probable that the above 

 difference is, in a great measure, due to the fact that a weight 

 of 16 kilogs. (less than one-sixth of the breaking weight of the 

 pianoforte wire) used for the operation of " Ons and Offs " is far too 

 small to produce anything like full effect on the magnetisation of the 

 steel wire, and that this difference can be greatly diminished by using 

 a heavier weight (perhaps 40 or 50 kilogs.) to operate " Ons and Offs." 

 The difference that exists between the intensity of magnetisation of 

 the steel pianoforte wire and that of the glass-hard- tempered steel 

 wire, corresponding to low magnetising forces, is greatly due to a 

 similar cause ; but observing that there subsists a considerable differ- 

 ence in the intensity of magnetisation of these two wires even for so 

 high a magnetising force as 50 or 60 units, it seems probable that 

 the intensity of magnetisation of the glass-hard-tempered steel wire is 

 really smaller for every magnetising force than that of the iron- 

 tempered steel wire, even when the effect of stress is taken into 

 account. 



As regards the limit of the magnetisation of these wires, on com- 

 paring the curves (a) and (b) in these diagrams, it will be seen that 

 that limit is attained at so low magnetising force as 80 units or so, 

 both in the case of the soft iron wires and the non-tempered steel wire, 

 and that the maximum magnetisation of the pianoforte wire is not 

 lower than that of the soft iron wires in the ordinary cases — results 

 certainly unexpected. On the other hand, the comparison of the 

 curves (b) and (c) in the Diagram III requires a careful study. It 

 shows that at about 80 or even 100 units of the magnetising force 

 there is a notable difference between the magnetisation of the non- 

 tempered and glass-hard-tempered steel w T ires ; but whether this 

 difference is due to the fact that the maximum magnetisation of the 

 latter is not yet reached at the above-stated magnetising force, or it 

 represents the actual difference in the maximum magnetisation of the 

 two wires, it is difficult to decide. In whichever way this difference 

 is accounted for, it is not unfair to say that the maximum magnetisa- 

 tion of the glass-hard-tempered steel wire is very nearly, if indeed 

 not exactly, equal to that of the steel pianoforte wire or the soft iron 

 wires, and that the minimum magnetising force corresponding to the 

 maximum magnetisation is somewhat higher in the case of the former 



