
of Capacities in Electrical Work. 369 
Therefore C+:001 _ 235°8 | 
C 39°6 ¢ 
or C=:000201 microfarad; 
or (=201 micro-microfarads. 
(2) To find the small change in the capacity 2 when ed has 
been moved into its second position. 
In first position :— 
100 divisions in 59:0 seconds, 
100 divisions in 59°5 sy, 
160° divisions -in 5971... «,, 
Mean,..cp S520. -c; 
In second position :— 
100 divisions in 60°53 seconds, 
100 divisions in 59°8 __,, 
100 divisions in 60°70. ,, 
Mein... 6010: ~., 
Therefore C+a_ 601 
Cr B92’ 
and C=201 micro-microfarads ; 
ig a =3°'05 micro-microfarads. 
Calculating a from the formula 
l 
e—_ 
fe 
2 log ~ 
2 
where /=8°01 ecms., 
714=3°9D, cms., 
T= ''97 om: 
we get a=2°85 electrostatic units 
=3°16 micro-microfarads. 
We get, therefore, 3°16 by calculation, 
and 3°05 by experiment. 
The method is therefore quite capable of detecting and 
measuring with considerable accuracy a capacity of 1 micro- 
microfarad or even less. 
