114 Mr. Henry Holden on the 



force, I shall show later how it may be calculated on this 

 supposition. Taking this view of the matter, it is evident 

 why the so-called capacity of a conductor is not altered by 

 any changes in the conductor (such as change of material, 

 or change from a solid to a hollow conductor) which do not 

 alter the direction and extent of the lines of force. 



The capacity of a certain portion of a dielectric, bounded 

 by lines of force and equipotential surfaces, may be therefore 

 defined as the qtiantity of electricity^ zvJiich has to be dis- 

 tributed over one end {an equal but opposite quantity being on 

 the other e?zd)y in order to cause unit differejtce of potential 

 betiveen the two ends, and we may call the capacity of a 

 portion of a dielectrical medium of unit length and unit 

 section the specific capacity of that dielectric ; a term corres- 

 ponding to specific conductivity in the case of a conducting 

 medium. Each dielectric will have its own specific capacity, 

 and the ratio of this to that of air will, of course, be the 

 specific inductive capacity of the dielectric considered. 



Method of calcidating capacity. 



Consider a charged conductor A at potential Va in the 

 presence of other conductors B, C, etc., at potentials Vb, Vc, 

 etc., and suppose that the dielectric medium between has a 

 specific inductive capacity = K. 



1 The distribution of the electricity is supposed to be such that the lines of 

 force proceeding from one quantity of electricity to the other bound the portion 

 of the dielectric under consideration. 



