412 On the Action of Non-conducting Bodies in Electric Induction. 



I always found that the induced electricity of the neutral sphere 

 was increased. Consequently we can apparently change the 

 induction of a charged body upon a neutral one in any manner 

 we please, without introducing into the space between both, 

 which is occupied by atmospheric air, either a conducting or a 

 non-conducting body. 



The preceding research may be considered as demonstrating 

 the following fact. The inductive influence exercised by a 

 charged body upon a neutral one is not changed by bringing 

 any interposed body, conducting or non-conducting, into its 

 neighbourhood. An increase or decrease of the quantity of 

 electricity upon an induced body may be produced by a con- 

 ducting or a non-conducting interposed body ; this increase or 

 decrease arises from two new inductions proceeding from the in- 

 terposed body itself, whose total action will depend upon the 

 distribution of the electricities upon this body, and consequently 

 also upon its substance, form and dimensions. 



Accordingly, there is no essential difference between the 

 actions of conducting and non-conducting bodies ; but inasmuch 

 as the distribution of electricity upon them depends also in ex- 

 treme cases upon their substance, interposed bodies of the same 

 form and magnitude will act differently. This difference of 

 action was particularly perceptible when the interposed body 

 was placed in the space between the charged and neutral bodies, 

 and may be explained by the well-known peculiarities of con- 

 ductors and insulators. In conducting bodies the distribution of 

 the induced electricities depends solely upon the attracting and 

 repelling forces of these electricities, and of the inducing elec- 

 tricity; in non-conducting bodies the distribution depends not 

 only upon these forces, but also upon the resistance which the 

 substance opposes to the motion of electricity. For example, in 

 a conducting disc, when influenced by a positively charged sphere 

 placed perpendicularly opposite to its centre, the most positively 

 electric places lie in all cases at the circumference ; in a non- 

 conducting disc they may be at some distance therefrom. If, 

 as interposed body between a charged and a neutral sphere, we 

 employ a disc whose diameter may be conceived gradually to 

 increase, then the induced positive electricity upon it will sooner 

 cease to exercise a superior influence upon the neutral sphere 

 when the disc is composed of a conducting, than when of a non- 

 conducting substance. Accordingly, with a conducting disc, the 

 action of the electricity, unlike that of the charged sphere, more 

 easily manifests itself, therefore the inductive action of this 

 sphere will be apparently diminished; with non-conducting 

 discs, the electricity, like that of the sphere, acts more easily, 

 consequently the inductive action of the sphere will be increased. 



