256 



SILSBEE AND HONAMAN: CONDUCTIVITY MEASUIIEMENTS 



sistance. As will be seen from the following, a wide variety of 

 sources was used to provide the appUed voltage and the indicating 

 instruments were correspondingly varied in character. 



VARIATION OP RESISTANCE WITH TEMPERATURE. 



The first experiments were carried out with an appUed direct 



Fig. 2. Typical results on porcelain cup showing variation of resistance with 



temperature. 



cmrent voltage of about 2000 volts which was obtained by recti- 

 fying with a kenotron a 3000 cycle voltage suppHed from a step- 

 up transformer. This rather compUcated system was chosen 

 in an attempt to dupHcate to some extent the voltages existing 



