228 On Polarization of Light by Refraction. 
_ Twas now desirous of ining the influence of refractive pow- 
mnidbciea I had already determined in 1813, that a greater quan- 
tity of light was polarized, at the same angle of incidence, by plates 
of a high than by plates of a low refractive power. I experienced 
great difficulty in this part of the inquiry, from the necessity of having 
plates. without any crystalline structure. I tried gold leaf in a varie- 
ty of ways ; but I found it almost impossible to obtain correct results, 
on account of the light which was transmitted unchanged through its 
By stretching a film of soapy water across a rectangular frame. at 
copper wire I obtained the following measure. 
WATER. 
Incidence. Inclination. Rotation. 
it OPewesr eo, BAG PY ge 9° fF 
I next tried a thin plate of metalline glass of a ae high refractive 
power. 
METALLINE GLASS. 
Incidence. Inclination. Rotation. 
eS Saag 2 
RS her ee eee 
er ee SOR ees 
CS eS eS ee a —- 
80 - = ee 
From a Gueerect of. these results it is oS os the rotation 
SReECEOe a the. releacsire paren. 
In examining the effects produced at different angles ¢ Ps incidence, 
it becomes obvious that the rotation varies with the deviation of the 
refracted ray; that is, with i—7, the difference of the angles of inci- 
dence and refraction. Hence from a consideration of the circum- 
stances of the phenomena I have been led to express the inclination 
g of the planes of polarization to the plane of refraction by ~~ bic 
mula, 
Cot o=cos (i—7), 
the rotation being =» — 459, 
‘This formula obviously gives a minimum at 0°, and a maximum 
at 90°; and at intermediate points it represents the experiments 50 
accurately, that when the rhomb of calcareous spar is set to the cal- 
culated angle of inclination, the gate MnpEe is completely i “ot 
visible,—a striking test of the correctness of principle on which i 3 
is founded. 
