282 On Polarization of Light by Reflexion. 
PLATE GLASS. 
Inclination,of Plane of Polarization 
Angle of Angle of to Plane of Reflexion. 
Incidence. Refraction. Observed. Computed. Difference. 
900. ne QO ss 45% 0'.. 5 469-0. ¥ 
BS eee a) 2, 4D. 4... 42.49. ee 
eater ed 7 +s. 4048.5... 40.86... see 
84 42 8 $8:49.0< 4:38.92 2. Ue oe 
80 A137 33.42. < +93. 46 =0 33 
75 40. 40 ., 28 45 27 Al... +b eet 
70 39 20 2 Of <2]. 3.272 ae 
65 37 (41 ~ 14.40 13 53 +0 47 
ee ee re ‘6 10 6 16-. —0 6 
56... 34605. 25 a0 20.0 an 
50 31. 22 ae 9 0 0 0 
45 28 29 16:65. 16 3h; +0 24 
90 2 65, 26 AR 5 1, OP SI F QS Fos . pet 
RO siti 89 ASH sas. «82 B6-.2...83. 19°. 2 
aes ASSO. TSE. 0 4. 1 
10. . 6 4 .. 4 0; 488. - 402 
These results, obtained in every part of the quadrant, completely 
establish the accuracy of the formula. The differences are all with- 
in the limits of the errors of observation,-and amount, at an average, 
to 324’ on each observation 
It is a curious A le BE which I believe has not before been 
remarked, that at an incidence of 45° the deviation produced by re- 
fraction, or i—7’, is, in every substance, the complement of the an- 
gle of refraction ¢ to 45°; and in the action of all substances 
upon polarized light at an Some of 45°, the rotation of the plane of 
polarization of a pencil polarized +- 45°, or — 45°, is equal to the 
the angle of refraction; while the inclination of the clane of polari- 
zation to the plane of sillciion, or 9, is equal to the deviation i—#- 
In order to establish the accuracy of the formula for different de- 
grees of refractive power, I made the following ite on Dia- 
mond, in which the index of refraction was 2.440. 
