664 



sensibility h was increased every time by 2 Volts in potential 

 for every state separately. The state, as indicated over every 

 curve, always represents the initial state. All the measurements 

 following here were made with a provisional apparatus ; the suspen- 

 sion consisted of a Wollaston wire 7 ii thick, and 97 mm. long. 

 (Scale distance 1.5 m.). 



From these curves appears the greater potential sensibility of 

 the system for greater potential difference between a and h ; for the 

 state (+ 32.0, — 6) V e. g. a displacement of almost 700 mm. was 

 fuund for 2 V potential increase oï h; for (-f 8.0, — 2) V it amounted 

 to it 500 ram. for 20 Volts. The state (+32.0, —6) V does not 

 represent the most sensitive state that could be obtained. 



I think the cause of this greater potential sensibility is the 

 following : 



When a recedes from h in consequence of a potential increase 

 of h, which is brought about by increase of charge of ó, the negative 

 induced charge on b will diminish in consequence of this motion, 

 or rather the potential value of b will be c//mz?2«Vié?c/; for a positively 

 charged body {a) recedes from b. The greater the potential difference 

 is between a and b, the greater will be the potential diminution in 

 question for a definite angle; in other words the potential diminution 

 of b required for a receding of a over a definite angle will be the 

 less, i. e. the potential sensibility will be the greater. Besides the 

 said change of the induced ciiarge at the same time increases the 

 angular displacement, which is another reason for greater potential 

 sensibility. 



2. It follows from the foregoing, that greater potential sensibility, 

 obtained in this way, must be attended by an increasing capacity ; 

 for when through a definite addition of charge to è in a state with 

 greater potential difference between a and b a slighter potential 

 increase will set in in consequence of the motion of a, this will imply 

 a greater capacity of b. Capacity measurements (method Harms, 

 Phys. Zs. 1904) give the same result; the capacity in the state 

 (4-8,0 — 2) V amounted namely to 5,2 e.s. units; that in the state 

 (-|- 20,0 — 3) V 6,0 e.s. units. Both values are the mean from a great 

 many determinations. 



What is the reason why, in spite of this increase of capacity, the 

 increase of potential sensibility more than counterbalances it, will 

 appear from the application of the following consideration of the 

 capacity. 



Though for an electrometer tiie sensibility of charge is in direct 

 ratio to the potential sensibility, and at the same time in inverse ratio 



