344 Temperature and the Refractive Index of Liquids. [Mar. 12, 



values obtained for the temperature-variation of specific inductive 

 capacity of four of the liquid dielectrics investigated were compared 

 with the corresponding values of the temperature-variation of refrac- 

 tive index found by Messrs. Dale and Gladstone.* And the relations 

 between these two quantities, though not in accordance with Clerk 

 Maxwell's electromagnetic theory of light, were near enough to 

 make it worth while to try whether the divergence from theory 

 might not be due to differences in composition. Accordingly I 

 measured the rate of change of refractive index with temperature for 

 the same specimens of the liquids as were used in the electrical 

 experiments. In the case of olive oil, however, the original supply 

 could not be found. The results obtained are very close to Messrs. 

 Dale and Gladstone's for those of the liquids they had examined, and 

 for the others the optical effect shows a similar divergence from 

 Maxwell's theoretical relation. And considering the enormous diffe- 

 rence in the rapidity of the electrical and optical effects, this is not 

 surprising. 



The change of refractive index was measured by observing with 

 spectrometer the minimum deviation of the D lines for a bottle pri 

 filled with the liquid. The observations were taken at two tempe: 

 tnres, viz., that of the room, 16 or 17 C., and a higher temperatu 

 about 40 C., obtained by heating the prism and its contents in warm 

 water. The results are shown in the following table, the last column i 



In the case of glass, the change of refractive index with temj 

 ture was found by Stefanf to be 0'0000023 per degree centigrade 

 quantity of quite a different order from 0'002, the rate of change > 

 specific inductive capacity. And in view of the influence of the time 

 of charging, even when extremely short, upon the specific indue 



Result* collected in Watts's ' Diet, of Chem.,' vol. 3. 

 t ' Wien., Akad. Sitzber.,' vol. 63, Abth. 2. 



