984 Dr. Gr. Breit on the Effective Capacity of 



and because it may be shown to be the real part of 



~ J 2a dt L 6 



OO e -{4S-L){U-t?V)-hJ2-l 



-J/» 47^1 J' 



At any point on the square the charge density due 



to V is 



■ _*a&V. (28) 



where as before k is 9 ° u , K being the dielectric 



constant of the mediam outside the square and <r* being 



the directional derivative along the normal drawn outward 

 at the surface of the square. Since that surface has the 

 equation m = 0, 



k BV I dw 



4lit ~du J dz 



Let as usual I denote the perimeter of one turn and ds 

 an element of length along the perimeter of the square 

 reckoned positive when in the direction of v increasing. 

 The amount of charge in the element ds is 



Kq , BV [ dw 

 kir ~du I dz 



ds. 



If now dv should stand for the change in v corresponding 



to ds. -=- = |~ because the transformation used is con- 



dv J aw 



formal. Hence the amount of charge between v and 

 v + dv is 



Q ( „)«fo = _^(|Y) dv. 

 ^ V 47r \du/ u= o 



Hence, since the function a(v) is -~- , then by (27) 



. . . (29) 



It is now also necessary to find M(v). This is found 



