Dr. A. Schuster's Experiments on Electrical Vibrations, 347 



Many other observations agree with this conclusion. When, 

 for instance, the galvanometer of small resistance was employed, 

 a current about eighty times stronger passed through the induc- 

 tion-coil than when the usual galvanometer was used. It should 

 be expected that if the effect were due to a magnetization of the 

 magnet, it would be stronger in that case, if not eighty times, 

 perhaps thirty or forty times. Yet the effect was hardly stronger 

 than before, sometimes even not quite as strong. The nume- 

 rical results obtained give additional evidence against the expla- 

 nation which we have just discussed. 



IV. Two possible Explanations. 



As we cannot explain the effect by any known cause, we have 

 to find another explanation. I can only account in two ways 

 for the phenomenon which has to be explained ; and my experi- 

 ments give no clue as to which of them is the correct explanation. 

 The first, and perhaps the simplest assumption to be made, is 

 that Ohm's law is not rigidly correct. Ohm's law says that the 

 resistance which a wire offers to an electric current going through 

 it is independent of the strength of the current. I shall try to 

 show now that my observations can be explained by assuming 

 that the resistance decreases as the current increases, but that 

 the deviation from Ohm's law would be so small that it would 

 not have been found out by any of the usual methods of veri- 

 fying Ohm's law. Suppose the electromotive force of the rota- 

 ting magnet to be -\-e in one direction and — e in the other 

 direction, and that the electromotive force sending the perma- 

 nent current through the galvanometer-circuit is -\-2x. If the 

 permanent current and the electrical vibrations go^ through the 

 circuit at the same time, we have a current the electromotive 

 force of which is x + e, counterbalancing another current the elec- 

 tromotive force of which is x — e. If the resistance for both cases 

 is equal to r, we have as the resultant current affecting the galva- 

 nometer-needle 



x + e x — e _ 2% 

 r r r 



We should therefore have the same effect as if only the perma- 

 nent current went through the circuit. If, however, the resist- 

 ance of the first current is r + dr, we have for the whole effect 



x-\-e x — e 



r -f dr r 



If dr is very small, this expression is equal to 



2x x + e , 

 x-ar. 



