of Organic Bodies, $c, at very Low Temperatures. 251 



to be the substance under examination,, is connected, as shown in 

 the diagram, so that it can be placed in parallel with either of the 

 shunted condensers forming the third and fourth arms of the bridge. 

 The process of measurement is then as follows: — The experi- 

 mental condenser is placed in parallel, by the switch S, say, with 

 the third arm of the bridge, and the shunt resistances are first 

 adjusted, so that the telephone gives a minimum of sound. The capa- 

 city of one sliding condenser, 0], is then varied until complete silence 

 in the telephone in the bridge is obtained. The experimental con- 

 denser is next shifted over into parallel with the fourth arm, and the 

 capacity of the same sliding condenser is again adjusted to produce 

 silence in the telephone. The change in capacity thus made in the 

 sliding condenser corresponding to the change in position of the 

 experimental condenser is denoted by s. The experimental con- 

 denser then has its air dielectric replaced by a liquid of known 

 dielectric constant D , and the same process of change of its position 

 effected. Let the variation of the adjustable sliding condenser then 

 be denoted by S . Finally the experimental condenser has its air 

 dielectric replaced by a liquid or frozen liquid of unknown dielectric 



t 2 



