4 JMr. Faraday and Dr. P. Riess on the Action of 



through its mass. Now my view of the induction agrees with 

 yours as respects the anterior and posterior faces of the shell-lac 

 plate ; but it differs in two important points : it assumes that if 

 the plate be supposed to consist of an infinite number of parallel 

 plates, each composed of a single layer of particles, each plate 

 has its anterior negative, and its posterior positive surfaces ; and 

 that the outer posterior positive surface is not the consequence of 

 the transmission of electricity by the intervening conducting par- 

 ticles between it and the anterior negative surface, but of a trans- 

 mission of the force by the polarity of the insulating particles. Upon 

 so stating the case, one or two considerations arise fitted to test the 

 relative value of the two views, and as yet they confirm me in 

 mine. 



If the shell-lac plate had had its anterior surface charged 

 negatively, as the like surface of a metallic or conducting plate 

 would have been, then that surface should not have remained 

 exclusively charged on the removal of the plate from the induc- 

 tion ; the shell-lac plate, like a conducting plate, should have 

 been found charged over both faces and all its surface ; for the 

 same conduction which would permit the flow of electricity under 

 induction, would permit the return to all parts when the induc- 

 tion was removed. As induction cannot be assumed for one 

 part of the expei-iment and reftised for the other, so I find this 

 consideration alone fatal to your view, as I understand it from 

 the translation. 



The second consideration is of this kind. If the shell-lac 

 plate whilst in the inductive position be considered, according to 

 my view, as a mass of non-conducting particles polarized, then 

 the action of the spirit-lamp flame will have been to convey, by 

 convection, negative electricity to the posterior surface of the plate, 

 to neutralize for the time its temporary constrained induced 

 positive state ; and it is that surface which (after the removal of 

 the plate from the induction, and the return of the constrained 

 state now no longer sustained by P) is to be considered as nega- 

 tively charged, and not the anterior surface, the latter now being 

 only held in a relatively negative state by the still remaining 

 polarity of the particles between it and the really chai-ged pos- 

 terior surface. So, apart and beyond the argument derived from 

 conduction, other determining considerations may thus be raised. 

 If your view be the correct one, it is the anterior surface only 

 which is charged negatively, and that by an inductive action half 

 discharged; in my view, it is the posterior surface which has 

 that state conferred on it by convection from the flame : — in your 

 view the inner parts of the plate are in their natural condition ; 

 in my view they are still polarized, being retained in that con- 

 dition by the posterior negative charge, Happily the question 



