Dielectrics in a Steady Field of Force. 



399 



hours in F = *26, period 12*64; after 48 hours longer in 

 F='13, 24-0 seconds. F 2 /(w 2 -« *)=H-land 10'85. 



Thus for different substances and over a wide range of 

 values the effective polarization of an insulated rod approaches 

 the same final value whatever the intensity of the field 

 may be. 



5. Rate of Polarization. 



In the foregoing observations of the rate of change of K in 

 steady fields there appear then to be three stages, a sudden 

 yield, followed by a change at a uniform rate for intervals of 

 time differing in the various substances from a few minutes 

 to several hours, and later an approach to saturation. 



In order to see how these, especially the second, hold over 

 a wider range of substances the following measurements 

 were made. The details of the observations and their 

 reduction, which are lengthy, are not given. In every case 

 the specimen was dried for several days, in some cases weeks, 

 over phosphoric anhydride and in vacuo, until the period tested 

 in an alternating field of force had become steady. 



Fused Quartz. K^ = 3*78. 



Time 



1 ID. 



4 m. 



7 m. 



10 m. 



30 in. 



120 m. 





K 



^ 



83 



97 



12-8 



14 7 



Paraffin Wax, K— =2'32 



Time 



i m. 



1 in. 



2 m. 



5 m. 

 704 



10 m. 



K 



6-28 



C>52 



077 



7-12 



Sulphur, Iw = 4-03. 



Time 



•2 m. 



1 m. 



1 



j 2 m. 



1 



6 m. 



4-99 



10 m. 



50 m. 



2-5 h. 



19 h. 

 101 



27 b. 

 141 



K 



44 



1 

 4-51 



1 459 



543 



1007 



20-8 



