202 Mr. H. H. Lester : Determination of Work Function 



small fraction of itself by means of a 100-ohm shunt (y) 

 around a 1-ohm cell (x) in series with the battery. These 

 resistances were WolfE standards. The 1-ohm and the 

 10-ohm coils were maintained at constant temperature 



Fijr. 1. 



by means of an oil-bath. A Weston ammeter (A), reading 

 to 1500 milliamperes, served to measure the bridge 

 current. It was compared with another ammeter for which 

 the calibration was known. The battery potentials were 

 read on a Weston voltmeter (V) reading to 75 volts. It 

 was compared with a Weston standard voltmeter and found 

 to agree. The standard was later calibrated by means of a 

 Wolff potentiometer and a Weston normal cell. 



The thermionic current was introduced into the bridge 



