50 GENERAL THEOREMS. 



In order, therefore, that an electrified body be in equilibrium 

 in an electrical field, either the force of the field must be zero, or 

 the field must be uniform, with the condition that the algebraical 

 sum of the electrical masses which the body possesses, be zero. 



In this demonstration, we have assumed that the electricity was 

 fixed on the body A, and that the external masses themselves formed 

 a rigid system. The theorem applies with the more reason to the 

 case in which the system contained conductors. If stable equilibrium 

 does not exist when connections are introduced into the system, this 

 is still less the case when these connections are suppressed; for 

 instance, when the electrified bodies are in part conductors, which 

 leaves more play to the displacement of electrical masses. 



