196 Methods for the Solution of Special Problems [CH. vm 



The following table, applicable to two spheres of equal radius, taken to be unity, is 

 compiled from materials given by Lord Kelvin*. 



Images in dielectrics. 



224. The method of images can also be applied to find the field produced 

 by point charges when half of the field is occupied by dielectric, the boundary 

 of the dielectric being an infinite plane. 



FIG. 66. 



We begin by considering the field produced by a single charge e at P, it 

 being possible to obtain the most general field by the superposition of simple 

 fields of this kind. 



* Papers on Electrostatics and Magnetism, p. 96, 142. 



