VOLTAIC POTENTIAL DIFFERENCE BETWEEN CONDUCTORS. 



77 



very high (150 volts) and in a weakly ionized medium, the other low 

 (0.2 volt), but in an intensely ionized medium, but they may eventually 

 produce equal currents. Effectively this is the case. Other voltages such 

 as the room potential may be operative, but their effect proved to be 

 secondary. If the capacities C'C", are successively removed, the electro- 

 meter current increases proportionately, showing its origin to be directed 

 from the needle or the electrometer case toward the insulated or non- 

 earthed pair of quadrants. 

 60 



FIG. 27. Increment of potential (cm. of scale), in the lapse of 

 time (seconds), when the auxiliary condensers are successively 

 removed. 



FIG. 28. Variation of potential V (cm. of scale), in the lapse of 

 time (seconds) , when the aluminum core or the brass shell of 

 the electrical condenser are alternately put to earth. Subscript 

 zeros indicate the earthed metal. 



If the electrometer metals are reversed (see fig. 26), the voltaic couple 

 is reversed. This makes it possible to obtain both the voltaic contact 

 potential and the ionization in the cylindrical condenser C, from a pair 

 of commutated measurements. If the sign of the charge of the electro- 

 meter needle is reversed, the deflection of the needle is not reversed, but 



