The Electrical Conductivity 53 



It is noted that the current through the crystal is increased 

 but that the X-Ray exposure has not a permanent effect on 

 the conductivity. 



Summary 



1. In calcite crystals there is a polarization effect due 

 possibly to a space charge near the electrodes or throughout 

 the crystal. 



2. There is a displacement current as well as a conduction 

 current. 



3. The relation between the current and the temperature 

 is approximately exponential. 



4. The conductivity is directional. 



5. Exposure of the crystals to X-Rays increases the con- 

 ductivity; returning to a normal value in one or two hours. 



The writer wishes to thank Dr. J. H. L, Johnstone who 

 suggested this problem and under whose direction the work 

 was carried out, and also Dr. H. L. Bronson who offered many 

 suggestions. 



