192 ELLIPTIC POLARIZATION. 



the property was extended, by Sir John Herschel, to all trans- 

 parent bodies possessing an adamantine lustre. Sir GK B. Airy 

 has proved, that plane-polarized light becomes elliptically 

 polarized by reflexion from diamond. And, finally, Mr. 

 Dale and Professor Powell have shown that these two pro- 

 perties, supposed to be peculiar to metals, belonged to all 

 transparent bodies having a high refractive power. 



In this state of the question, the problem of reflexion by 

 transparent bodies was taken up by M. Jamin, and received 

 at his hands its complete experimental solution. The con- 

 clusions deduced by M. Jamin from his observations may be 

 summed up as follows : 



I. All transparent bodies polarize the light incompletely 

 by reflexion, the polarization of the reflected light becoming 

 a maximum at a certain angle of incidence. 



II. They transform plane-polarized light into light el lip- 

 ticatty polarized. 



III. The difference of phase which they impress upon 

 light, polarized in the two principal planes, undergoes the 

 same variations as in metallic reflexion, within certain limits 

 of incidence. 



(204) It is necessary to enter a little more minutely into 

 the consideration of this third law, which (it is obvious from 

 the preceding) virtually includes the two others. 



According to Fresnel's theory, when a ray polarized in 

 any plane falls upon a transparent body, the reflected light 

 continues polarized. But its plane of polarization is changed ; 

 and lies at the opposite side of the plane of incidence, when 

 the incidence is less than the polarizing angle, and at the 

 same side when it is greater (190). It follows from this, 

 that the two components of the reflected ray, polarized 

 respectively in the plane of incidence, and in the perpendicu- 

 lar plane, agree in phase at all incidences above the angle of 



