﻿222 M. W. von Bezold's Investigations on the Electrophorus. 



only in an alteration of the surface, and not in the nature of the 

 electrophorus, I take no account of it in this preliminary notice. 

 The descriptions refer only to a new plate, or to the part of 

 an old one which has been protected by the cover. 



With these plates the following experiments were made : — 



First Experiment. — If the cake be rubbed while supported 

 vertically on a table and only held loosely at the upper edge, 

 after the dusting it will be found covered on both sides with red 

 oxide of lead. The two surfaces present nevertheless different 

 appearances. The rubbed surface exhibits streaks, from which 

 the direction of the rubbing may be inferred, occasionally inter- 

 mingled with yellow places. On the other side, on the contrary, 

 the powder is tolerably uniform. With stronger rubbing the 

 passage of positive electricity to the plate cannot be avoided, as 

 can be readily ascertained after sprinkling with the powder. 



The explanation of this experiment has been given above. 

 Here it is a case of a single negatively electrical layer, and hence 

 positive electricity is attracted on both sides. 



Second Experiment. — If the plate be feebly rubbed while it is 

 lying upon the form {abgeleitete Bodenplatte), after being lifted 

 up and dusted it acts just as if it had been rubbed in the air. 

 If now the cover be laid upon such a cake resting in the ordi- 

 nary manner upon the form, a positive spark may be taken 

 from the cover which has been lifted off. But if the cake be in- 

 verted so that it lies with the rubbed surface upon the form, the 

 cover after being removed gives either no electricity at all, or at 

 most only traces. If, however, the cake, while its rubbed side is 

 still turned towards the plate, be laid upon insulating supports 

 (for instance, rods of sealing-wax), positive electricity is obtained 

 from the cover when it is laid upon it and removed in the ordinary 

 manner, and the more the higher the supports are. 



These experiments show that, with very feeble'primary electri- 

 fying, electricity passes neither between the cake and the form 

 nor between the cake and the cover, and therefore that in this 

 case only that which is directly excited can come into play. 



If now the cake rests in the normal position on the plate, the 

 action of the originally excited electricity upon the cover is but 

 little enfeebled by the positive electricity attracted on the far 

 more distant form, and hence the cover when raised must exhibit 

 distinct quantities of positive electricity. If, on the contrary, 

 the cake has its rubbed side turned towards the form, owing to 

 the positive electricity collected in the closely adjacent form, the 

 action of the originally excited electricity upon the far more dis- 

 tant cover becomes extremely small, and hence when raised the 

 cover will be found to be unelectrical. 



A simple calculation shows that the quantities of electricity in 



