PROCEEDINGS 



OF 



THE ROYAL IRISH ACADEMY. 



1843. No. 40. 



May 8. 



SIR Wm. R. HAMILTON, LL.D., President, in the Chair. 



I. G. Abeltshauser, Esq. was elected a member of the 

 Academy. 



The special thanks of the Academy were voted to Miss 

 Edgeworth for her donation of Wedgewood's Pvrometer. 



Professor Mac Cullagh read the following communication. 



On the Laws of Metallic Reflexion, and on the Mode of making 

 Experime?its upon Elliptic Polarization. 



Several years ago, as the Academy are aware, I made an 

 attempt to investigate the laws according to which light is 

 reflected at the surfaces of metals, and I then proposed cer- 

 tain formulae which represented, with sufficient accuracy, all 

 the facts and experiments which I was able to collect upon 

 the subject (see the Proceedings of the Academy, vol. i. p. 2, 

 October, 1836; Transactions, vol. xviii. p. 71, note). But 

 in order to test these formulae satisfactorily, it was neces- 

 sary to obtain measurements far more exact than any that 

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

 instrument, which was constructed for me by Mr. Grubb, 

 and of which a brief description has been given in the Pro- 

 ceedings, vol. i. p. 159. I regret to say, however, that no- 



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