96 THE ROYAL SOCIETY OF CANADA 



FJG. J . 



A. — Crystal of calcite. 



B. — Brass electrodes. 



C— Glass tubes filled with sulphur. 



D. — Calcium Chloride. 



E. — Tin container. 



The currents through the crystals, which varied from 5X10"^' 

 to 2.5X10-9 amperes, were measured by a Dolazalek electrometer 

 with a subdivided mica condenser in parallel with a pair of quadrants. 



To produce luminescence the calcite was cooled to -80°C and 

 then placed in a thermostat at 22°C. In other experiments the change 

 of temperature was from 22°C to 100°C. 



Effect of Time and Temperature on Conductivity 



During certain preliminary measurements it was noticed that 

 the current gradually decreased after the potential was first applied 

 to the crystal. Table 1 shows a characteristic set of readings. 



