Dr. A. Schuster's Experiments on Electrical Vibrations. 345 



Additional experiments to prove the impossibility of accounting 

 for the effect by bilateral deflection were made. The needle was 

 deflected by permanent magnets placed near the galvanometer. 

 The relative position of the galvanometer-needle to the axis of 

 the coil was therefore changed; and this was done in such a way 

 that bilateral deflection, instead of increasing the deflection, 

 would tend to diminish it. As, however, in this case the deflec- 

 tion was just as much increased by the rotation of the magnet 

 as before, I consider it proved beyond doubt that no change of 

 magnetization of the galvanometer-needle can have caused the 

 effect. 



3. It remains for us to consider in detail what effect the per- 

 manent current has on the magnetism of the rotating magnet. 



Let a c be the axis of the coil within which the magnet ro- 

 tates. The wires of the coil 

 are therefore parallel to b d. 

 Suppose the current passes in 

 the direction indicated by the 

 arrow-head in that part of the 

 coil which is above the plane 

 of the paper. The permanent 

 current would in that case in- 

 crease the strength of the ro- 

 tating magnet while the north 

 pole moves from b to d, the 

 rotation being in the direction 

 of the movement of the hands 

 of a watch. The magnetism, 

 on the other hand, is decreased 

 while the north pole moves 

 from d to b. The induction will be in the direction d b while 

 the magnet moves from a to c, and in the direction b d while 

 it moves from c to a. The weakening and strengthening of the 

 magnet, therefore, take place symmetrically with respect to the 

 direction of the induction-shocks. While the induction-shock 

 passes from b to d } the magnet is first strengthened and then 

 weakened. While the induction-current passes from d to b, the 

 magnet is first weakened and then strengthened. Such a differ- 

 ence in the magnetism could not, therefore, alter the strength of 

 the induction-shocks ; and they would counterbalance each other 

 just as much as before, were it not for a secondary effect which, 

 indeed, tends to produce the phenomenon that has to be ex- 

 plained. There will be an induction of currents in the coil due 

 not to the motion of the magnet, but to its magnetization 

 and demagnetization. While the north pole moves from b to c, 

 the magnet is strengthened and the current in b if weakened 



