116 



THE ROYAL SOCIETY OF CANADA 



by a mirror through a glass window in the back of the instrument. 

 The separation of the fibres when charged was measured by means 

 of a microscope provided with a scale. The electrical system was 

 calibrated in the ordinary way with a set of storage cells, and by means 

 of a calibration curve the changes in the separation of the fibres were 

 transcribed into potential falls. In practice the fibres were charged 



Fig. 2 



by means of a Zamboni pile through the intermediary of an insulated 

 sound passing through the walls of the vessel as shewn by the diagram, 

 which could be turned when desired so as to come into contact with 

 a metal piece connecting the fibres to their upper insulating support. 

 All contacts, except in the case of the covering tube. A, were either 

 soldered or made by fluted joints provided with leather washers. 

 The lower end of the covering tube. A, had a ground conical surface 

 and was held hermetically connected to the body of the instrument 

 by means of a threaded shoulder piece. All the joints were carefully 

 examined before each experiment and found to be air-tight before 

 measurements were undertaken. All the gases used were carefully 

 dried before being admitted into the instrument. The latter, however, 

 was provided with a small drying chamber opening directly into its 

 interior and a small glass vessel in this chamber was always kept filled 

 with metallic sodium. 



In all experiments made with air it was found that the ionisation 

 was the same whether the sodium was present or not. 



