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LXI. On some new Laws of Reflexion of Polarized Light, 

 By the Rev. Samuel Haughton*. 



IT is well known to experimental opticians, that the laws of 

 polarization of plane-polarized light reflected from the sur- 

 faces of transparent bodies, given by Fresnel and Brewster, are 

 only approximate laws, except in the case of some glasses of a 

 certain refractive index and reflecting power, in which the laws 

 of Brewster and Fresnel become as exact as can be expected in 

 such experiments. But although the fact that these laws are 

 only approximate was well known, it was not until the experi- 

 ments of M. Jamin were published that we had a numerical 

 statement of the extent of deviation from these generally received 

 laws. These experiments are published in the Annales de Chimie 

 et de Physique^ vol. xxix. p. 263, and must be regarded as a 

 model of accurate and unprejudiced observations of facts. The 

 facts ascertained by M. Jamin in his examination are summed 

 up by him as follows : — 



1st. That almost all solid substances polarize light imperfectly 

 by reflexion. 



2nd. That they transform an incident plane-polarized beam 

 into a beam elliptically polarized. 



3rd. That if the incident plane-polarized beam be resolved 

 into its two components, in and perpendicular to the plane of 

 incidence, the difference of phase in the reflected components, at 

 the perpendicular, principal, and grazing incidences, is 180°, 270°, 

 360°, respectively. 



4th. That the laws of reflexion depend on two constants, one 

 of which is the index of refraction, and the other the coefficient 

 of ellipticity arising from the reflecting power of the body. 



5th. That all substances, whose index of refraction is greater 

 than 1*46, accelerate the phase of the component in the plane of 

 incidence. 



6th. That all substances, whose index of refraction is less than 

 1*46, retard the phase of the component in the plane of incidence. 



7th. That substances whose index of refraction is sensibly 

 equal to 1 '46, polarize the reflected light rectilinearly, and obey 

 Fresnel and Brewster's laws. 



8th. That M. Cauchy's formulse for the diamond apply to all 

 bodies, while FresneFs apply only to the particular case of re« 

 fleeted light which is plane-polarized. 



9th. A table, p. 303, contains the constants of elliptic po- 

 larization of forty-three substances. 



In a paper published by me in the Philosophical Magazine, 

 Fourth Series, vol. vi. p. 81, 1 have shown that the 8th statement 



* Communicated by the Author. . 

 2 L 2 



