St Memoir on Neio Optical Phenomena. [Fe«, 



independent of the other modes of action, which they exercise on 

 light. After having determined the angle under which this pheno- 

 menon takes place with respect to different bodies, water and glass, 

 for example, I sought for that at which the same phenomenon 

 would take place at their surtace of separation, when they are rn 

 contact : but the law according to which this last angle depends 

 upon the first two still remains to be determined. 



I published, a year ago, in the Memoirs of the Society d'Arcueil, 

 that after having modified a solar ray I made it pass through any 

 number of diaphanous bodies without any of it being reflected, 

 which gave me a method of measuring exactly the quantity of light 

 that these bodies absorb — a problem which the partial reflection of 

 light by bodies rendered of impossible solution. 



Thus, by placing in the direction of a polarized ray a pile of 

 parallel glasses forming with it an angle of 35° 25', I had ob- 

 served that this ray produced no reflected light upon any of them j 

 and I concluded from this that the light, which would have been 

 reflected on employing a common ray, in this case passed through 

 the diaphanous bodies. A foreign philosopher, in giving an account 

 of my experiment, observes, that he is not of my opinion that the 

 modified light is transmitted by the surfaces when it is not reflected, 

 and that he is rather inclined to believe that in this case the portion 

 reflected in ordinary cases is entirely absorbed or destroyed. I have 

 solved that question decisively by the following experiment : I made 

 the incident ray turn round without changing place, and pre- 

 serving the same position with respect to the pile. When it ha* 

 made ^th of the circumference, it is totally reflected by the suc- 

 cessive action of the glasses, and it ceases to be seen at the extre- 

 mity of the pile. After half a revolution on itself it begins to be 

 transmitted anew. This experiment presents the singular pheno- 

 menon of a body which appears sometimes diaphanous and some- 

 times opaque, while it receives not only the same quantity of light 

 but the same ray, and under the same inclination. 



It is needless to observe, that in order to make a polarized ray 

 turn round, I employed a ray formed by the ordinary refrac- 

 tion of Iceland crystal, whose faces are parallel to each other, and 

 pei-pendicular to the dii'ection of the ray. By turning these faces^ 

 in their own plane, I change the position of the poles of the ray 

 without varying its direction or intensity. 



I shall not detail the consequences that may be deduced from 

 what 1 have stated : all that I could add would be a repetition of 

 the same fects presented in a different manner. 



