BABBITT. — THE VON WALTENHOFEN PHENOMENON. 257 



The galvanometer was not tested at the end of this set but on the next 

 day it was found to be the same to within 0.1 of one per cent. The 

 comparatively wide divergence between the flux changes in the iron as 

 indicated by the instrument are far greater than any variation in it was 

 ever found to be. When the 1-step process yields such heterogeneous 

 results, it is not possible to draw any decided conclusions by comparing 

 them with 2- or 3-step processes of magnetization. Taking an average 

 in a case like this introduces an average error of 1^ per cent at the 

 start. Consequently all such data were discarded. 



One magnetization differs from the next only in the effects produced 

 by the previous history of the iron. We may divide that into two 

 parts : (1), the previous magnetizations, (2), the previous demagnetiza- 

 tions. If the variations were due to the former, we should expect at 

 least that there would be a continuous change and not the jumps back 

 and forth which were often more pronounced and numerous than those 

 recorded above. In other words, a continuous rise or fall in the flux 

 induced would not be unexpected ; but an alternation of the two, giving 

 wavy curves no two of which can be superposed for the same maximum 

 fields, leads one to suspect that some disturbing element enters which is 

 more potent than the previous magnetization. 



The demagnetization seems to be that element. Only by chance is 

 it twice the same. In one instance it may consist of 500 reversals with 

 a maximum field of 3, 260 with a maximum field of 2.8, 800 with a 

 maximum field of 2.5, and so on ; in the next instance it may consist of 

 200 reversals with a maximum field of 3.1, 400 with a maximum field 

 of 2.9, 350 with a maximum field of 2.6, and so on. The motion of the 

 secondary, which could not be made continuous and of which the various 

 small distances moved were by no means equal, would give just this sort 

 of thing. To assume that such a variation in the process should not 

 have its effect on the non-magnetic condition in which the iron is left 

 is hardly safe. In fact, the results obtained when ever}'thing except 

 this process is constant are so variable as to indicate in all probability 

 that the cause of the variation lies here. 



The trouble with this method led to one somewhat similar to that 

 used on core I. The iron was demagnetized and then carried around 

 a hysteresis cycle with a constant maximum field for any desired num- 

 ber of times. It was stopped at some point between the two maximum 

 fields, brought to a zero inducing field by simply breaking the circuit, 

 and carried on in the direction in which it was going originally to the 

 peak of the hysteresis curve in one step. If the flux change is always the 

 same when the one step is repeated, it is to be inferred that the one-step 

 replacing a larger number does not have any appreciable effect on the 



VOL. XL VII. — 17 



