340 



Prof. A. LI. Ruolies on the Contact 



(This was done in another apparatus.) The film was 

 generally exposed to the atmosphere for about two days 

 before contact potential experiments were made. Two quartz 

 furnaces, F, which could be heated electrically, are situated 



TO £LfCTf?OMET£R 



below the glass disk and in positions making an angle of 

 120° with one another and with the brass electrode E. 

 One contained bismuth and the other, zinc. The furnaces 

 with the metals in them were heated beforehand for a 

 considerable time in an auxiliary vacuum to get rid of 

 occluded gases as much as possible. The distilled metals 

 were deposited on the under side of the glass disk. The 

 partitions A, surrounding the furnaces and the electrode E, 

 served to confine the deposit to definite areas of the disk. 

 The distance between the disk and the electrode E was about 

 1 mm. This electrode was connected to a quadrant electro- 

 meter whose sensitiveness was 700 divisions per volt. The 

 apparatus was exhausted by means of a Gaede molecular air- 

 pump, to which it was joined by a short brass tube about 

 25 mm. wide. All joints were made airtight by a mixture 



