266 



.Dielectric Constants at very Low Temperatures. 



(v) Because the high dielectric values of water and alcohol and 

 other bodies at ordinary temperatures remain, even when 

 the observations are taken with alternating electromotive 

 forces of exceedingly high frequency and under conditions 

 when there are no electrodes to polarise, as when the 

 electric refractive index is measured with electromagnetic 

 radiation. 



We consider that the results of observations so far made are best 

 expressed by merely considering the dielectric constant to be a 

 function of the frequency and the temperature, and represented 

 therefore by a dielectric surface, which surface has for some substances 

 a region of abnormal dielectric ordinate. 



In all cases so far examined by us, lowering the temperature suffi- 

 ciently acts in the same manner in reducing the dielectric constant 

 as sufficiently increasing the frequency, and both actions reduce the 

 abnormally large dielectric values of some substances to values more 

 approximately equal to the square of the optical refractive index of 

 the body. 



The question then to be considered is the physical reason for the 

 high dielectric values for particular substances for certain ranges of 

 electromotive force frequency and temperature. Whether this 

 abnormal electric displacement is considered to be the result of a 

 molecular strain superimposed on a true electric strain, or whether 

 ifc is the beginnings of that molecular deformation which finally ends 

 in chemical decomposition, remains to be seen. Having regard to 

 the enormously high electrical resistivity which we have shown these 

 frozen dielectrics to possess, it does not appear to us likely that 

 polarisation in the sense of a deposition of ions on the electrodes can 

 be invoked to explain the differences we have shown exist. 



