76 ELECTRICAL EQUILIBRIUM. 



If the conductors A and B are identical, and arranged sym- 



metrically, the coefficients a and b are equal, and the formula 

 becomes 



We have assumed that the action of the two bodies reduces to a 

 single resultant. If it were not so, the same reasoning would apply 

 to the two resultants by which the whole of the forces may be 

 replaced. 



As a matter of fact the calculations required by this method for 

 determining the coefficients C a , C 6 , C' a and C' 6 , and the resultant R, 

 are extremely tedious even in the simplest cases. We shall after- 

 wards explain the application which Sir W. Thomson has made of it 

 to calculating the reciprocal influence of two spheres. 



