On Polarization of Light by Refraction. 



227 



right angles to that of reflexion. This difference is exactly what 

 might have been expected from the opposite character of the result- 

 ing polarization, the poles of the particles of light which were form- 

 erly repelled by the force of reflexion, being now attracted by the re- 

 fracting force. 



In this experiment the action of the two surfaces is developed in 

 succession, so that we cannot deduce from the maximum rotation of 

 21° 19', the real action of the first, or of a single surface, which must 

 be obviously more than half of the action of the t«p surfaces, because 

 the planes of polarization have been widened before they undergo the 

 action of the second surface. 



In order to obtain the rotation 

 due to a single surface, I took a 

 prism of glass ABC (Fig. 2.) hav- 

 ing such an angle BAG, that a ray 

 RR, incident as obliquely as pos- 

 sible, should emerge in a direction 

 Rr perpendicular to the surface 

 AC. I took care that this prism was well annealed, and I caused 

 the refraction to be performed as near as possible to the vertex A, 

 where the glass was thinnest and consequently most free from the in- 

 fluence of any polarizing structure. In this way I obtained the fol- 

 lowing measures. 



R 



Angles of 

 Incidence. 



GLASS. 



Inclination of Planes nb, cd, (Fig. 1.) 

 to tlie Plane of Reflexion. 



Rotation. 



ui ixeiieAiuiJ. 



87° 38' 54° 15' 9° 15' 



54 50 ..... 47 25 2 25 



32 20 45 22 ..... 22 



I next made the following experiments with two kinds of glass, — 

 the one a piece of parallel plate glass, and the other a piece of very 

 thin crown. The latter had the advantage of separating the reflected 

 from the transmitted light. 



PLATE GLASS. CROWN GLASS. 



Inclination. Rotation. 



45° 0' 

 47 18 

 49 19 

 52 16 

 58 4i 

 61 



0° 0' 

 2 18 

 4 19 

 7 16 

 13 42 

 16 d 



