18 
PROFESSORS W. E. AYRTON AND J. PERRY 
Let the capacity of each pair of quadrants be C p of 3 be C 3 , and of 4 be C 4 ; 
Let the coefficient of induction of the electrometer needle on each pair of quadrants 
be K,„ of substance 1 on plate 3 be K 1? and of substance 2 on plate 4 be K. : . 
Fig. 2. 
Now on reversal (fig. 2) the needle will be deflected and the change of the capacity 
of each pah’ of electrometer quadrants, as well as the change of the coefficient of induc¬ 
tion of the needle on each, will be proportional to the deflection, that is, proportional 
to cl the difference of potentials now existing between the two sets of quadrants, 
therefore let the potential of 3 become D+d, and of 4 become D ; 
Let the capacity of each pair of quadrants become C q -\-cd, and of 3 become C' 3 , 
of 4 become C' 4 ; 
Let the coefficient of induction of the electrometer needle on each pair of quadrants 
become K u -\-hd, of substance 2 on plate 3 become K' 3 , and of substance 1 on plate 4 
become K\; then— 
=AK 1 + BC s +NK„+Ba 
Before reversal, fig. 1, 
The charge in 3 and in 
the pair of attached 
quadrants 
The charge in 4 and in 
the pair of attached ^ = (A+a)K 2 -fBC 4 ,fl-NK„+BC ? 
quadrants 
After reversal, fig. 2, 
The charge in 3 and in 
the pair of attached 
quadrants 
> — (A+a)K 3 +(D+d)C / 3 -bN(K ;i +M)fl-(D-j-cZ)(C ? -f-cc£) 
The charge in 4 and in 
the pair of attached ^ =AK / 1 +DC' 4 +N(K ;( +M) + D(C y +cd) 
quadrants 
