THE 
LONDON, EDINBURGH, and DUBLIN 
PHILOSOPHICAL MAGAZINE 
AND 
JOURNAL OF SCIENCE. 
[FIFTH SERIES.] 
JUL Y 1883. 
I. On the Constant of Dielectricity and the Double Refraction 
of Insulating Fluids. By G. Quincke*. 
ACCORDING to the views of Faradayf, we must assume 
that in every point of an insulating fluid which is elec- 
trified like the glass of a Leyden jar there is a pulhng force 
in the direction of the hues of force, and a pushing force per- 
pendicular to those lines. According to Maxwell J, these 
pushing forces are given by the equation 
,=£.? a) 
if P denotes the difference of electric potentials, a the dis- 
tance between the plane metallic faces, or electrodes, between 
which the fluid is situated. K x would have for the forces 
parallel and perpendicular to the lines of electric force the 
same value and would be equal to the clielectricity-constant K, 
or the number which represents the increase of the capacity 
of a condenser when the plates are separated from one another 
by another insulating substance instead of air. According to 
the most recent theoretic investigations by Helmholtz§, the 
ratio between the amounts of the pressures and tensions per- 
* Translated from the Sitziuigsberichte der Km. Preuss. Akad. der 
Wissensch. Berlin, 18S3, April 5, pp. 413-420. 
t Expei-irnental Besearches, §§ 1224 & 1297. 
% Electricity and Magnetism, i. §§ 111 & 124. 
§ Berlin Monatsber. xvii. 2, 1881. 
Phil. Mag. S. 5. Vol. 16. No. 97. July 1883. B 
