260  Mr,  A.  Russell  on  the 
Now  R  has  its  maximum  value  ROT  wlieu  r  is  AL. 
Hence  IL,  = 
Zqc 
Vqc 
2^ 
AL(c— AL)  ~  a{d-'la)  ~  ax  ' 
where  x  is  the  minimum    distance  between   the   cylinders. 
Now,  we  have  "* 
_  V 
*-41og{(d  +  c)/2«}' 
where   V  is  the  potential-difference  between  the  cylinders 
and  c2  =  d2  —  4a2. 
Hence  we  have 
V  c/2ar 
R_  = 
xlog\(d+c)/2a\ 
V  , 
-A 
where 
and 
log  (1  +  ,//2a  +y)- 
y={*/a+(*/2a)'p. 
Values  of/ are  given  in  the  following  table  :- 
Table  V. 
(27) 
xla . . . 
o-oi 
1-00 
0-02 
0-03 
0-04 
0-05 
0-06 
0  07 
0-08 
009 
' i 
i-oo 
1-00 
101 
101 
1-01 
1-01 
1-01 
1-015 
x  a  ... 
o-i 
0-2 
03 
0-4 
0-5 
0-6 
0-7 
0-8 
!      0-9 
f 
102 
1-03 
105 
1-065 
1-08 
1-10 
111 
1-13 
!     114 
x  a  ... 
1 
2 
3 
4 
1-61 
5 
6 
7 
8 
9 
' 
1-16 
1-315 
1-46 
1-74 
1-88 
201 
2-11 
2-24 
x  a  ... 
10 
!     20 
30 
40 
50 
100 
1000 
10.000 
/ 
:  2-39 
1 
3-56 
|  4-62 
1 
5 -62 
I 
6-58 
11-0 
72-5 
587 
*  Russell,  {  Alternating  Currents/  vol.  i.  p.  102. 
