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XXL On the Phenomena and Laws of Elliptic Polarization, as exhibited in the 
Action of Metals upon Light. By David Brewster, LL.D. F.R.S. Lond. 
8c Edin. 
Read April 22, 1830. 
From the first dawn of the science of polarization, the action of metals upon 
light has presented a troublesome anomaly. Malus at first announced that 
they produced no effect whatever ; but by employing a different method of 
observation, I found that the light reflected by metallic surfaces was so far 
modified as to produce, when transmitted through thin crystallized plates, the 
complementary colours of polarized light. From a second series of expe- 
riments made previous to mine, Malus came to the conclusion, that the diffe- 
rence between transparent and metallic bodies consisted in this: that the former 
refract all the light which they polarize in one plane, and reflect all the light 
which they polarize in another ; while metallic bodies reflect what they polarize 
in both planes. 
Having discovered the property of transparent bodies to polarize light by 
successive reflexions at angles at which a single reflexion produced no percep- 
tible effect*, I resolved to apply this method of examination to metals ; and on 
the 7th of February 1815, when I first made the experiment, I discovered the 
curious property possessed by silver and gold of dividing a polarized ray into 
complementary colours by successive reflexions. As this subject promised 
to open a wide field of inquiry, I prepared for the ardent prosecution of it 
with all the metallic bodies which could be procured ; but the pressure of pro- 
fessional business prevented me for about a month from doing any thing very 
effectual. 
On the 6th of March 1815, 1 received a letter from M. Biot, requesting some 
information on a matter of business ; and in answering this letter on the 
same day, I communicated to him an account of the discovery above men- 
* Phil. Trans. 1815, p. 142. 
MDCCCXXX. 2 P 
