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XIII. On some Properties of Light, By David Brewster, LL.D. 

 F. R. S, Edin. In a Letter to Sir H. Davy, LL, D. F. R. S, 



Read January 28, 1813. 



Dear Sir, 



Having been for some time engaged in a series of experi- 

 ments on the phenomena of light arising from its transmission 

 through diaphanous bodies, I have taken the liberty of com- 

 municating to you, for the information of the Royal Society, 

 a short and general account of the results of my enquiries. In 

 the narrow compass of a letter, it would be impracticable to 

 include the various details of these experiments; the parti- 

 cular methods of observation that were employed ; or the 

 numerical results which I have obtained for the refractive and 

 dispersive powers of nearly two hundred substances. As these 

 will form part of a separate work, in which I am now engaged^ 

 I shall confine myself at present to some of those results 

 which appear to be most interesting, either from their novelty 

 or importance. 



1. On a new Property of refracted Light. 



As you are already well acquainted with the optical pro- 

 perties of doubly refracting media, and the analogous property 

 of reflected light discovered by MALus,it will be unnecessary 

 to take any notice of these phenomena. After repeating the 

 experiments of Majlus, and measuring several of the angles 



