ii6 



Mr. Henry Holden on the 



dielectric enclosed by the tubes of force proceeding 

 A to B = Cab, say and .". 



4^' Ca b 

 K 



from 





We should get similar expressions for the portion of the 

 dielectric enclosed by the tubes of force proceeding from A 

 to the other bodies, so that summing up so as to include all 

 the dielectric through which the lines of force from A pass, 



47rC 



K 



% 



dr_ 



The following examples will show the applicability of the 

 method. 



Ex, I. Concentric spheres, 

 radii Ri and R2. The lines of 

 force are radii, and dS = rWw ; 

 the limits of r being Ri and R2 



R2 R2 



/dr^ _ r dr _ 1 f 1 i\ 

 dS ~ J r^~ dio\Ri~ R2J 

 Ri Ri 



The inverse of this has now 

 to be integrated so as to in- 

 clude all the tubes of force 

 proceeding between the two Fig. 2. 



spheres ; the limits of dio are .*. and 47r, or 



j\.iK.2 4^ R1R2 



R2 — Ri R2 ~ Ri 



or C 



47r R1R2 

 R2- Ri 



R R1R2 

 R2 — Ri 



£x. 2. — Parallel planes, surface S, at distance e. 



