398 



Prof. W. M. Thornton on the Polarization of 



cases. The value of K before the field was reversed was 25, 

 of which 9 was the sudden rise at the start. At reversal 

 there was a rapid change equal to twice that from zero, i. e , 

 of 18, leaving a polarization of: K=7 in a direction opposite 

 to that of the field. It will be seen that Curve B starts from 

 a value — 7. 



The ellipsoid was then exposed to the field for three weeks 

 and acquired a value of K = 6075. 



The following numbers give the free depolarization from 

 this high value; The periods from which K was calculated 

 were taken by applying a weak field and measuring the 

 period after it had been on for a minute in each case, after 

 which it was cut off. There is no doubt a sudden rise o£ 

 polarization at the moment of applying the field, but since 

 the conditions are the same in each case the figures give an 

 approximation to the rate of relaxation. 



Free depolarization of Flint Glass, A 3*3. 



Time 



10 m. 



1 b. 



2 h. . 



3 b. 



4 b. 



5 b. 







19-5 h. I 

 1 



i 



1 K 



6075 



426 



79-7 



28-0 



12-73 



9-0 



8-17 | 



4. Equality of Final Values. 



Before proceeding to examine whether these high con- 

 stants are true polarization as distinct from the movement of 

 free charge, four typical substances were examined for 

 equality of K in different fields, the periods being taken to 

 be steady when they did not change by a measurable amount 

 in twelve hours. Since the derived value of K is propor- 

 tional to F 2 /(?* 2 — n*) equality in observed values of the latter 

 is also true for the dielectric constants. 



Paraffin Wax Ellipsoid. — Free period 16*5 seconds. After 

 7 days in F = *259, period 13*63 ; after 48 hours more in a 

 field -132, 24-0 seconds. From these F 2 /(ft 2 -;* 2 ) =13*65 and 

 13*69 respectively, giving equality of K. 



Sulphur Cylinder. — Free period 23*1. After 16 hours in 

 F = *131, period 19-7 ; after 24 hours longer in F = *259, 10*8 

 seconds. F 2 /(?i 2 -— w 2 ) = 24*62 and 25*0 respectively. 



Gutta Percha Cylinder. — Free period 49*6 seconds. After 

 66 hours in a field '26, period 9*01 ; after 30 hours longer 

 in F = *132, 16-7 seconds. F 2 /(n 2 -» 2 ) = 5-66 and 5*50. 



Ebonite Cylinder. — Free period 86*2 seconds. After 48 



