8 Profs. J. Dewar and J. A. Fleming. On the Dielectric 



In the following table the temperatures are given in terms of 

 platinum temperature (pt.) as denned by our standard platinum 

 thermometer P x .* 



Table III. — Dielectric Constant of Ice at Various Temperatures. 

 Frequency of Fork, 124. 



Temperature in 

 platinum degrees 



by standard 

 thermometer P x . 



Scale reading 

 or galvanometer 

 deflection in 

 centimetres. 



Dielectric 

 constant 

 of ice. 



pt. 







- 198 -0 



5-6 



2 -83 



-197-8 



5 -6 



2 -83 



-197-6 



6-0 



3-03 



-182 -0 



6 -25 



3 -16 



-176 -8 



6*4 



3 -23 



-171 -0 



6*8 



3*44 



-165 -7 



7 -2 



3 -64 



-161 -8 



7-6 



3 -84 



-159-7 



8-0 



4-04 



-155-2 



8-8 



4-45 



-150-8 



10-0 



5-05 



-146 -7 



10-6 



5-36 



-143 2 



11 -7 



5-92 



-141 -7 



12-7 



6-42 



-140 -0 



13-4 



6-77 



-138-5 



14-1 



7-13 



-137 -5 



15-1 



7-63 



-136-2 



16 -5 



8-34 



-134 -5 



17 -7 



8-94 



-133 2 



18-0 



9-1 



-131-0 



21-8 



11-0 



-130-7 



23 -0 



11 -6 



With the above frequency (124) the conductivity of the ice began to make itself 

 felt at about -130° pt. 



The above numerical results are plotted out in a curve in fig. 2. 

 They show clearly that the dielectric constant of the ice increases 

 progressively from a value of about 2' 8 to 1T6 between the limits of 

 — 198° and —131° pt. Moreover, the trend of the curve shows that 

 at the absolute zero the dielectric constant of the ice would probably 

 not be far from 2'0. With the above arrangements we were not able, 

 partly for want of time and partly because of the very moderate 

 frequency of the tuning-fork, to take the dielectric constant at higher 

 temperature, but this we hope to do before long, and also to examine 

 the effect of varying the frequency of the contact maker. 



* See Dewar aixd Fleming, " On the Thermo-electric Power of Metals and 

 Alloys," < Phil. Mag.,' July, 1895, p. 100. 



