56 ELEMENTS OF STATIC ELECTRICITY. 



composed of an infinite number of such surfaces, or 

 spherical shells, having a common center ; and their 

 radii as equipotential lines cut by such surfaces. From 

 which it is evident that no difference of potential could 

 exist in the interior of such a sphere. 



If it were insulated, a positive charge communicated 

 to it would evidently be distributed equally through 

 every part, if there were no influence tending to pro- 

 dace a different effect. But, since the sphere would 

 be at a higher potential than its surroundings, induc- 

 tion would create lines of force in the direction of the 

 radii, which must result in the condensation of the en- 

 tire charge on the surface. 



Also, since every portion of the sphere is at the 

 same potential, and since electrified bodies at the same 

 potential repel each other, it is evident that the mole- 

 cules would be self-repellent. But since they are rigid, 

 the electricity of each molecule would repel that of 

 every other, and move in the direction of least resist- 

 ance. Let a row of molecules composing a diameter 

 be selected, the direction of least resistance would be 

 from the center each way. For, if surface condensa- 

 tion takes place (and experiment shows that it does), 

 as the electricity of the molecules near each end of the 

 diameter became condensed at the extreme points, its 

 reaction being thus neutralized, more would be repelled 

 from the center, and. this would continue till all the 

 electricity of the diameter was condensed at the ends. 



But since the ends are points on the surface, and the 

 surface is made up of an infinite number of such points, 

 it is evident that the entire charge would be condensed 

 on the surface. 



Hence surface condensation takes place under the 



