﻿M. W. von Bezold's Investigations on the Electrophones. 221 



ought to have assumed a series of alternately positive and nega- 

 tive layers in the insulator. 



It has hitherto only been shown that the facts observed by 

 Riess may be explained otherwise than by the assumption of 

 three layers. It now remains to prove that they must be other- 

 wise explained. This may be done with the aid of an experiment 

 which is quite analogous to one described in the paper in Pog- 

 gendorff's Annalen already cited. If the disk be electrified while 

 it is not lying on the bottom plate, and if it be treated with the 

 flame first of all upon the rubbed and then upon the unrubbed 

 side of the plate, on Riess's hypothesis the positive layer must 

 predominate, which is said to have been in the interior of the 

 insulator. On my view, on the contrary, the plate should be 

 quite unelectrical. 



Experiment shows, in fact, that the plate really loses all elec- 

 tricity. But it must be made with great caution. I could only 

 get it perfectly clear by taking a larger ebonite plate (at least 25 

 centims. in diameter), and by only rubbing this in one small 

 place in the middle. When a greater part of the surface was 

 electrified or a smaller plate used, it could not be avoided that 

 some positive electricity should pass from the tips of the fingers 

 of the hand in which it was held, from the sleeves, &c. to the 

 unrubbed side ; and thus the experiment became indecisive. An 

 investigation with the powder-mixture makes evident all such 

 disturbing influences. 



§ 3. The experiments are now to be described which serve as 

 basis for the new theory, which is founded only on electrical 

 action at a distance. A few repetitions could not here be avoided, 

 as they were indispensable for the comprehension of the whole. 

 Two circular ebonite plates were used for the experiments. One 

 was 5 millims. in thickness, and its diameter was 45 centims. ; 

 when used as an electrophorus-cake, it was placed upon a zinc 

 disk 52 centims. in diameter, and had a cover 45 centims. in 

 diameter. The other plate was only 4 millims. in thickness, 

 and its diameter was 23 centims. Experiments were moreover 

 made with plates of ordinary green glass, and identical results 

 obtained — of course, with the opposite sign. 



The larger of the two ebonite plates had already been in use 

 for a year as an electrophorus-cake, and in accordance with this 

 was ordinarily protected by its cover. Oddly enough, at the out- 

 side edge of this plate, where it was exposed to the light, a 

 breadth of 5 centims. exhibited a totally different behaviour from 

 that of the central part. The small plate was quite new, and in 

 its entire extent behaved exactly like the central part of the 

 other. As I convinced myself both in this manner and other- 

 wise that that peculiar deportment of the edge had its origin 



