220 



Prof. D. E. Hughes. 



[May 19, 



having a total of 200 turns, with an exterior diameter of 1*5 millims., 

 withdrawing the steel wire, leaving this closely wound helix free, 

 it ^ave some 190°, instead of the 200 of the steel wire alone ; thus the 

 spiral currents fully equalled a closely wound copper wire helix of 

 200 turns in a similar length. 



If it were possible to twist a magnetised wire several turns to the 

 right, and that its line of magnetism should coincide with that of the 

 twist, then on passing a positive or negative current, there would 

 be an apparent augmented or diminished spirality of the current, but 

 both would have a right-handed twist. The result would be identical 

 with the phenomenon described, although the cause is different. 



The explanation of this phenomenon can be probably found in the 

 fact that the constant spirality now observed is that of the electric 

 current under which it was magnetised, for whilst magnetising it we 

 had a powerful source of magnetism constantly reacting upon the 

 electric current, and the constant spirality now observed is the result 

 or remains of a violent molecular reaction at the instant of magnetisa- 

 tion, and the remaining evident path or spiral is that of the electric 

 current. On testing this wire as to its longitudinal magnetic force, I 

 found that it was less than that of a wire simply magnetised in the usual 

 way ; thus the effects are internal, affecting the passage of the electric 

 current, giving, however, no external indications (except apparent 

 weakness) of the enormous disturbance which has taken place. 



If, instead of drawing the north pole of the magnet as above, from 

 positive towards negative, I draw it from negative to positive, all the 

 effects are repeated, except that we have now, as we should expect, a left- 

 handed spiral. But if I draw the magnet from the extremities of the 

 wire to the centre, then at this centre I find an absolute zero of twist, 

 but on each side a contrary twist, the wire then having a left and 

 right-handed twist, the positive travelling towards the centre in a 

 right-handed twist gradually ceasing in zero; this is as we might 

 expect, but if done under the influence of a constant current, no matter 

 what pole of the battery enters afterwards the north pole of the 

 magnet, it will have during its first half a right-handed, and its second 

 a left-handed spiral. It became important to know if a wire which 

 had been magnetised under the influence of a current could be re- 

 stored to something like its original condition. Electric currents had 

 no effect. Heat, which would not destroy its temper, had no effect. 

 Mechanical vibrations and torsions failed to disturb the molecular 

 arrangement ; but magnetising it strongly by a magnet, when 

 no current was passing, at once broaght the wire to its usual 

 apparently rigid state, and the constant or intermittent currents now 

 indicated only 18° of spiral currents against a previous 200°, and the 

 sounds were, as usual from steel, excessively weak. I have since 

 used this method with invariable success, when I wished to repeat 



