182 Dr. W. von Bezold on the Electrical 



had been supposed ; I refer to the peculiar part played by the 

 insulating medium in the electrical condenser, Leyden jar, or 

 coated plate, which shows itself in the so-called residual effects — 

 that is, in the diminution of the charge after it is first given, and 

 in the reappearance of a charge after complete discharge. 



These facts have called forth several investigations, a portion 

 of which are referred to in a paper published by the author in 

 PoggendorfPs Annalen, vol. cxiv. p. 404. This communication 

 was intended to serve as introduction to the researches of which 

 he now takes leave to record briefly the principal results. 



It was mentioned on the former occasion that Kohlrausch 

 was the first, as well as the only person who had formed any 

 precise conception as to the behaviour of insulators in the case 

 in question. He assumed that the force with which the electri- 

 cities distributed upon the coatings tend to separate the natural 

 electricities of any portion of the insulator, either produced such 

 separation in the smallest particles, or caused the particles which 

 already contained the separate electricities to rotate so as to 

 come into such a position as to exert an electrostatic moment 

 upon the coatings, and so to affect the phenomena of tension. 



It was shown in the paper referred to, that two consequences 

 necessarily follow from this conception. If Kohlrausch's view 

 is correct, it follows — 



(1) That a small intervening layer, the connecting medium, 

 for example, can exert no effect upon the disappearance of the 

 charge — that is to say, upon the formation of a residual charge. 



(2) That, provided the coatings are large enough in propor- 

 tion to the distance between them, this phenomenon must re- 

 main precisely the same whether thick or thin plates are used 

 as insulators, so long as they are all of the same material. 



The author had ascertained on a previous occasion that the 

 first of these consequences is not borne out by experiment, and 

 he has more recently found the observation confirmed. 



Having subsequently, by the kind intervention of Dr. Quincke, 

 obtained eight very fine glass plates of various thicknesses, but 

 each pair of equal thickness, all blown from the same pot and 

 cooled in the same manner, he was in a position to investigate the 

 second point also. 



The experiments showed that the alterations of the charge 

 took place at rates which were essentially different with different 

 plates, in such wise that the times which elapsed until the charge 

 had sunk by the same proportion of its original amount were nearly 

 proportional to the thickness of the plates *. 



* This, as well as all the subsequent comparisons, relates only to the first 

 few minutes after the charge was given ; and the numerical statements are 

 here only approximate. 



