192 Dr. G. Quincke on the Position of the Oscillations of the 



In the belief that the question can alone be decided by ex- 

 periment, the author has adopted the following- way : — 



From Malus's laws of the property of luminous rays polarized 

 perpendicularly to one another, and from Fresnel and Arago's 

 laws of the interference of polarized rays, it follows that the 

 vibrations are perpendicular to the luminous ray itself, and 

 either parallel or perpendicular to the plane of polarization. 

 In a perpendicular incidence, the rays which are reflected from 

 any surface must have the same deportment whether their vi- 

 brations are perpendicular or parallel to the plane of incidence. 

 But if the angle of incidence increases, there is no change for 

 the rays with vibrations perpendicular to the plane of inci- 

 dence, while for the rays whose vibrations are in that plane 

 the inclination of the path of the aether-particles in reference to 

 the reflecting surface changes. From the elliptic polarization of 

 light which is reflected at the limiting surface of metals and air, 

 or of glass and air, it is known that the rays with vibrations 

 perpendicular, and those with vibrations parallel to the plane 

 of incidence, undergo a change of phase which is different in 

 each case, and that the difference of the change of phase alters 

 with the angle of incidence. According to the author's view, 

 the ray with vibrations perpendicular to the plane of incidence 

 would undergo the same alteration of phase for all different 

 angles of incidence ; while the alteration of phase of the ray whose 

 vibrations are in the plane of incidence, as follows from Jamin's 

 experiments*, would increase by a magnitude corresponding 



to half a wave-length, -, if the angle of incidence increased from 



0° to 90°. However this may be, the phase of the rays which 

 vibrate in the plane of incidence must, in any case, change to a 

 greater extent with the incident angle than that of the rays 

 vibrating perpendicular to the plane of incidence ; and with the 

 same angle of incidence this change must be different according 

 to the nature of the media whose limiting surface reflects the 

 rays. In the reflexion from metallic surfaces, the change of 

 phase, at an angle of incidence which is considerably less than 

 the principal incidence (in which the difference of phase of the 

 components polarized parallel and perpendicular to the plane of 



incidence amounts to -), is already perceptible, but in reflexion 



from glass it is imperceptible. If, therefore, rays reflected 

 from the same surface, half glass and half metal, and which in 

 other respects are the same, could be made to interpose, the 



* Ann. de Chim. et de Phys. (3) 1850, vol. xxix. p. 2/9, and vol. xxxi. 

 p. 165. 



