of Organic Bodies, at very Low lemperatures. 261 



electrodes of the condenser, and that the capacity measured is a 

 polarisation capacity and not a true dielectric capacity, and he 

 supports this contention by pointing out that whenever we have 

 obtained a large dielectric value at the low temperature it has 

 always been measured with an electromotive force of 1*434 volts, 

 which is less than the ordinary full reverse electromotive force of 

 polarization. 



There are, however, reasons for considering that this contention is 

 not a valid one. In the first place we have always in all the 

 measurements begun operations by testing the dielectric capacity of 

 our condenser with an electromotive force of one Clark cell 

 (= 1*434 volts) in order to see roughly whether the dielectric value 

 was large or small. If it was a small value we then gradually in- 

 creased the electromotive force until a good readable galvanometer 

 deflection was obtained. We never found that with an electromotive 

 force of 1*434 volts, the dielectric constant of any substance was 

 greater than with a much higher voltage. 



In the next place, in many cases we changed from a working 

 electromotive force of about 20 volts to one of 1*434 volts, and w^ 

 never found any marked discontinuity in the calculated value of the 

 dielectric constant at that point. If our previous papers on this 

 subject are examined the following instances may be found. 



Table VII.- 



-Measurement of various Dielectric 

 different Electromotive Forces. 



Constants with 



Substance. 



let 



Sodic chloride, 



10 p. c. solution. . 

 Potassic chromate, 



30 p. c. solution. . 

 Cupric carbonate, 



10 p. c. suspension 

 Baric hydrate, 



5 p. c. suspension 

 Bismuth oxide, 



10 p. c. suspension 



Tempera- 

 ture, 

 f- 89*4 

 \~ 87*2 

 J -124*2 

 1 -119*2 

 J -118*5 

 | -114*0 

 / -112*4 

 \ -100*0 

 J -124*7 

 \ -120*8 

 -178*0 

 -174*2 

 -129-2 

 -127*3 



Dielectric, 

 constant. 



27*6 

 29*0 

 181 

 21-8 

 21*2 

 2*2*3 

 1G*9 

 22*3 

 16*5 

 21*8 

 23*9 

 25*5 

 19*9 

 24*5 



Yoltage with 

 which con- 

 stant was 

 measured. 



19*8 



1*4 

 20*3 



1*4 

 20*2 



1*4 

 20*0 



1*4 

 18*2 



1*4 

 19*5 



1*4 

 17*8 



1*4 



Eeference. 

 Boy. Soc.Proc.,' 

 vol. 61, p. 318. 



ji&zU, p. 321 



} 

 } 

 } 



Ibid. 



Ibid., p. 387. 

 Ibid., p. 390. 

 Ibid., p. 372. 



Ibid. 



376. 



An examination of the above instances will show that if the 

 electromotive force is changed from about 20 volts toJ"4 volts, it does 



