XXI. OK THE LAWS OF METALLIC BEFLEXION, AM) 

 ON THE MODE OF MAKING EXPEBIMENTS UPON 

 ELLIPTIC POLARIZATION. 



[Proceedings of the Royal Irish Academy, VOL. n. p. 376. Read, May 8, 1843.] 



SEVERAL years ago, as the Academy are aware, I made an at- 

 tempt to investigate the laws according to which light is re- 

 flected at the surface of metals, and I then proposed certain 

 formulae which represented, with sufficient accuracy, all the 

 facts and experiments which I was able to collect upon the sub- 

 ject.* But in order to test these formulas satisfactorily, it was 

 necessary to obtain measurements far more exact than any that 

 had previously been made ; and for this end I devised an in- 

 strument, which was constructed for me by Mr. Grubb, and of 

 which a brief description has been given in the Proceedings.-^ I 

 regret to say, however, that nothing of much consequence has 

 yet been done with the instrument. Some preliminary trials of 

 its performance were indeed made in the summer of 1837, and 

 the results of one of these shall presently be given ; but an ac- 

 cidental strain which it suffered, while I was preparing to un- 

 dertake a series of experiments, caused me to discontinue the 

 observations at the time ; and being then obliged to superintend 

 the printing of my essay on the " Laws of Crystalline Reflexion 

 and Refraction,":}: my attention was drawn afresh to this latter 



* See the Proceedings of the Academy, VOL. i. p. 2, October, 1836 (supra, p. 58) ; 

 Transactions, VOL. xvm. p- 71, note (supra, p. 133). 

 + VOL. i. p. 159 (supra, p. 138). 

 % Transactions R. I. A. (supra, p. 87). 



