large, we may have — ^ > — and then dC > and the curve slopes 



[CLARK] CAPILLARY ELECTROMETER 77 



with those with positive charging. The same must be true for C2. 



Hence — ? will be very large, as the slope of the tangent in the negative 



dCi Q^2 



part of the curve changes very rapidly. So in case — is not very 

 dC2 ^ Cf 



dCi Ci^ 

 upward in the positive portion. 



Q 



In case — is very large the curve will slope as in Figure 1. 

 Ci 



Since in making these determinations of capacity, it is necessary 

 to have the meniscus stop at the same point aftv^r the discharge into 

 the standard condenser, the pressure requires adjustment to bring 

 the meniscus to the proper final point. While it seemed unlikely that 

 this small change of pressure would have any effect on the capacity, 

 an electrometer was arranged to be placed inside a bell jar from which 

 the air could be removed. This necessitated an arrangement for a 

 wide change of pressure, which was accomplished without much 

 difficulty. There is certainly no change in capacity due to change of 

 pressure of an amount less than one atmosphere. 



A striking example of the increase of capacity with negative 

 charging of the electrometer was seen in the case of electrical oscilla- 

 tions of a system in which the electrometer was included. All attempts 

 to build an electrometer with resistance low enough to obtain oscilla- 

 tions ^ with it in series with a self-inductance proved futile. But, by 

 arranging a standard condenser in parallel with the electrometer and 

 these in series with the self-inductance, oscillations are possible. 

 Approximate theory shows that these are oscillations impressed on a 

 logarithmic charge or discharge curve. 



■mmmJ-^^^m\h 



G. Ci 



FI G.Z 



^ In a later paper an oscillatory system will be described where the capacity is 

 that of a pair of polarized electrodes. 



