Differential Inductometer and in the Electrophorus. 141 



maining part of the circuit) changes of induction take place. 

 In the ordinary experiments with the electrophorus this con- 

 ducting wire is represented by the earth, the base being unin- 

 sulated. Here we can speak of a circuit only with the same 

 right as in the case of a telegraphic battery with earth-con- 

 duction. If the conduction is broken by insulating the sole 

 after having it uninsulated, the electrophorus is without effect. 

 As to the changes of induction in the interior of the electro- 

 phorus (which we may imagine as a polarization of the dielec- 

 tric), I will further adduce the following experiments : — 



If the ebonite plate, put on the uninsulated base, is strongly 

 excited, it attaches itself to the base. If now the cover is put 

 on and both metal plates are uninsulated at the same time, it 

 attaches itself to the cover, so that we can lift the plate 

 by means of the cover. A current of positive electricity has 

 flowed at the moment of uninsulating from the sole through the 

 outer conducting wire to the cover. Before the current has 

 flowed, the induction (polarization) went wholly through the 

 ebonite plate; after the current the inductive (polarizing) 

 effect of the excited layer extends, for the greater part, through 

 the thinner interval of air to the cover, and only for a smaller 

 part of it through the thicker ebonite plate to the sole. 



Finally, I may mention an experiment in which branching 

 of induction, as well as branching of conduction, may easily 

 be observed. I beat the ebonite plate lying on the uninsulated 

 base, and put on the excited surface of the first another equal, 

 but not excited, ebonite plate, and then on this the metal cover. 

 This cover, being uninsulated and lifted, gave positive sparks, 

 just as if there had been in place of the upper ebonite plate a 

 corresponding layer of air. Immediately after this I tried 

 the upper ebonite plate, endeavouring to use it alone as the disk 

 of an electrophorus. But this trial did not succeed; the plate 

 was ineffective. 



Now I repeated the experiment, laid the same plate again on 

 the rubbed surface of the first ebonite plate, put on it also again 

 the cover, but left the apparatus unaltered during twelve hours. 

 In this case there is ebonite on the two sides of the inductric 

 layer of the ebonite plate; induction extends from this layer 

 through ebonite to the sole and to the cover. In the same 

 manner the conduction — the penetration or absorption of elec- 

 tricity — must take place to both sides; and I expected that the 

 negative electricity would penetrate not only into the lower 

 ebonite plate, but would go over to the upper plate also. This 

 is indeed what took place. After twelve hours the upper plate 

 could be used as the disk of an electrophorus. Both plates 

 gave now strong and, as it seemed, equal effects. As was 



