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



in consequence. Vfhile the north pole moves from c to d, the 

 temporary magnetism dies away again, and thereby strengthens 

 the current in b d. The consequence of this reaction of the 

 magnetization on the current is that the maximum of magneti- 

 zation does not take place when the north pole is at c } but only 

 after it has passed c. Similarly the minimum does not take 

 place when the north pole is at a, but only after it has passed a. 

 The induction-shock is therefore stronger while the north pole 

 of the rotating magnet moves from c to a than while it moves 

 from a to c. The two induction-shocks are not of equal strength, 

 but the direction will have the upper hand in which the perma- 

 nent current goes. A phenomenon similar to the one observed 

 would therefore take place. We have therefore to settle the 

 question whether this effect would be sufficiently strong to pro- 

 duce any visible effect. This could best be done experimentally. 

 While I was engaged with these experiments I did not think 

 of this retardation of the maximum of magnetism, to which 

 my attention has since been drawn by Professor Kirchhoff. I 

 can therefore, unfortunately, offer no direct evidence on the 

 subject; but I hope to be able to show that it is extremely un- 

 likely, and even next to impossible, that the phenomenon is due 

 to the cause just described. The strongest argument which I 

 can offer regarding this point is this : — The magnetism induced 

 by the permanent current must have been much weaker than 

 the magnetism induced by the earth. The temporary magnetism 

 induced by the earth did not, however, affect the experiments ; 

 and I conclude therefore that magnetism induced by the current 

 did not affect the experiments. 



That the magnetic force of the current was weaker than the # 

 magnetic force of the earth is shown as follows : — The tangent 

 of the deflection of the galvanometer-needle never exceeded 

 0*2. This is therefore the ratio of the magnetic force of the 

 current on the galvanometer-needle to the retaining force, which, 

 as the needle was astatic, was much weaker than the earth's 

 horizontal force. The magnetic force of the current on the gal- 

 vanometer-needle must have been much stronger than that on 

 the rotating magnet, as the resistance of the galvanometer was 

 2477 and that of the induction-coil only 30, the wires being about 

 the same thickness. It follows that the magnetizing force of 

 the current on the rotating magnet was much weaker than the 

 magnetizing force of the earth. As the induction-coil was used 

 in various positions, and no effect dependent upon that position 

 was ever observed, I conclude that the effect of the earth's in- 

 duction was too small to be observed, and consequently that 

 the permanent current could not have produced any sensible 

 alteration in the magnetism of the rotating magnet. 



