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



Fig-. 1. —Curves showing the Variation in Dielectric Constant with Temperature 

 of Various Organic Bodies. 



of the condenser when the particular substance mentioned was beiug 

 used as dielectric. The temperatures are given in platinum degrees, 

 as explained in our other papers to which reference is made." The 

 last column in the tables gives the electromotive force, in volts, 

 used to charge the condenser. The frequency of reversals was in all 

 cases 120 per second. 



The observations were stopped in each case at that temperature at 

 which any sensible true conductivity made its appearance in the 

 dielectric, and this, as we have already shown, takes place in the 

 case of many bodies quite suddenly, and at temperatures far below 

 their melting point. Thus it is impossible to carry up the dielectric 

 constant measurement, by the method we employed, of formic acid or 

 methyl alcohol much above about —120°, because at that point 



