IN CYLINDRICAL CONDUCTORS, ETC. 71 
in which d ( = 2a) is the diameter of either cylinder, and G (z) = \z\j ,, is plotted in 
fig. 3, its limiting value 
G( 2 ) = ( v / 22:-1)/8 .(46) 
being indicated by the broken line (B). 
Finally the expression included in { } includes the effect both of disturbance of 
current distribution due to proximity and of non-uniformity of the field. 
At low frequencies, by (21a), <p n is negligible and both (42) and (43) give for { } 
1 i 1 2 , 1 4 | 
1 T "Q/W + ] 8^ + ••• • 
This is identical with the result obtained for the thin wire (Equation 26), so that at 
low frequencies the distortion of distribution due to reaction of eddy-currents is quite 
negligible, and the effect of non-uniformity of the field will give in the extreme case 
where the cylinders are touching a correcting factor of amount 1 *0456 to be applied to 
the result obtained by the uniform field theory. 
At frequencies so high that (21 b) holds, the factor { } becomes 
