gS NEW PROPERTY OF REFLECTED LIGHT. 



Partial rcflcc- When a pencil of light traverses a transparent substance, 

 tion from g portion of the rays is reflected by the refractive surface, 

 bodies. apdanolher portion by tlie surface of emergence. The caus«sr 



of this partial reflection, which lias hitherto escaped the 

 researches of natural philosophers, seems, in several ciroum- 

 stauces, to have soine aaaloj;y with the forces that produce 

 the double refraction. 

 From water. For example, light reflected by the surface of water 



under an angle of 52° 4a' with the perpendicular has all the 

 characters of one of the pencils produced .by the double 

 refraction of a crystal of calcareous spar, the principal 

 section of which is pacallel or perpendicular to the plane, 

 that parses through the incident rayand . the^.veflectfd r^y,j 

 which we shall call the plane of reflection. „,.'- .!,;;.' i i~ 

 1 he rcftected If this reflected ray be received on any.cuystji!,._^jhat has( 

 rjy received the. property of doubling Images, and the principal ^Qtiojft 

 refracting CIVS of wliich is, parallel- to the plane of. refleciion, it wj^ niOt, 

 ''' ' be divided into two pencils, as^a'ray of direct ligh,t would. 



Rave been ; but it will be refracted entire according to the 

 ordinary law, as if the crystal had lost the faculty of 

 doubling images. If, on the contrary,^ the principal section 

 of the crystal be perpendicular to the plane of reflection', 

 the reflected ray will be refiacted entire according to the 

 extraordinary law. In the intermediate positions it will be 

 divided into two pencils according to the same law, and in 

 the same proportion, as if it had acquired its new character by 

 the influence of the double refraction. The ray reflected 

 by the s^irface of the liquid therefore, under this circuni- 

 fitancCi; has all the characters of an ordinary ray formed by 

 a crystal, the principal section of which is perpendicular to 

 the plane of reflection. 

 Tltispheno- .To analyse th]s phenomenon completely, I placed a 

 crystal so that its principal section was vertical; and after 

 having divided a luminous ray by means of the double re- 

 fraction, I re;ceived the two pencils proceeding from it on the 

 surface of water, at an angle of 52° 45'. The ordinary ray» 

 in being refracted, gave up to the partial reflection a por- 

 tion of its particles, as a pencil of direct light would have 

 done; but the extraordinary ray penetrated the liquid en- 

 tive, and none of its . particjes escaped refraction. On the 



controry 



meijon ana 

 ' lysed. 



