136 Dr. J. Moser on the Division of Induction in the 



thus be used as a Franklin's disk, a Ley den jar, or a condenser. 

 My electrophorus consisted of a circular ebonite plate 1*5 

 millim. thick and 30 centim. diameter. The coverings were 

 of zinc and were of the same diameter, one of them being pro- 

 vided with an ebonite handle. For other purposes I used three 

 plates of the same shape, of thinner ebonite, together with 

 other plates of zinc of similar dimensions. 



The simplest supposition is that the ebonite plate, lying 

 on the one uninsulated metal covering, being beaten by the 

 fox's tail becomes negatively electric. Then induction starts 

 from this negative layer of this ebonite plate as inductric 

 layer (inductor). The inducteous layer (inducendus), where 

 the induction ends, is the underlying uninsulated metal plate. 

 After putting on and uninsulating the upper metal plate, how- 

 ever, the ind action branches off again from the upper nega- 

 tive layer of the ebonite plate as inductric body (inductor), 

 and extends to both the metal plates as inducteous bodies (in- 

 ducendus). If there exists, as we have supposed, only one 

 inductric layer in the electrophorus, namely the negative one 

 on the upper surface of the ebonite plate, the differential in- 

 ductometer could be viewed as a scheme of the electrophorus. 

 The negative layer of the electrophorus would be represented 

 by the negatively charged middle inductric plate of the dif- 

 ferential in ductometer; and the two metal coverings of the one 

 apparatus would correspond to the two of the other. Further, 

 this similarity of the two apparatus appears still more com- 

 plete if we use the differential inductometer as electrophorus 

 for producing electricity. We can uninsulate the one plate 

 of the differential inductometer; and bringing the other near, 

 we can draw out of it a negative spark; then withdrawing it, 

 we can get a positive spark. But one difference now presents 

 itself, and proves the insufficiency of our last scheme. As to 

 the differential inductometer, it is perfectly indifferent whether 

 we uninsulate the right outer plate and insulate and discharge 

 the left one, or if we uninsulate this and change the distance 

 of the right one. We always get positive discharge from that 

 outer plate which we have removed from the negative middle 

 plate. The same kind, namely positive discharge, after re- 

 moval, must take place if there existed only one inductric 

 layer. Then there is, as Faraday (§ 1255) has already pointed 

 out, no difference as to the kind of induction through air and 

 that through ebonite. Therefore, the ebonite plate being in- 

 verted, the upper metal covering (which is now, however, 

 lying on the unrubbed ebonite surface) must give positive 

 electricity when it is lifted, as the plate did before. 



This, however, is not the case. If we turn the ebonite plate 



