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MONDAY, JANUARY 24, 1859. 
James HentHorn Topp, D.D., President, in the Chair. 
Tue Rey. J. H. Jevterr read a paper— 
ON THE REFLEXION AND REFRACTION OF POLARIZED LIGHT. 
THE object which the author has in view in this communication is to 
ascertain how far the theory of light which had been proposed by M. 
Cauchy can be considered to have been experimentally established by 
the observations of M. Jamin. For this purpose it is necessary to as- 
certain— 
1. Whether the values of any of the quantities by which a ray of 
light is defined, as deduced from theory, differ from those given by ex- 
periment, by an amount greater than the necessary error of observation. 
2. What variation the theoretic expressions admit of, preserving the 
necessary amount of agreement with observation. 
In examining this question, he drew attention to the remarkable fact 
first noticed by Mr. Haughton, namely, that the expressions given by 
Cauchy and a modified form of those given by Green, although these 
expressions are essentially different, agree, so far as the case of reflexion 
is concerned, equally well with the experimental results of M. Jamin. 
This agreement between the expressions he accounted for by showing 
that the four equations of which each system consists may be reduced to 
the following form :— 
One equation containing a constant depending upon the nature of 
the substance, and distinct from its index of refraction. 
Three equations which do not contain any experimental constant. 
Of this system of equations, the first alone is different in the two 
systems, the remaining three being the same in both. He showed from 
this, that by a proper determination of the experimental constant, a tole- 
rable agreement between these equations may be insured. 
He then proceeded to compare the values of the amplitude and phase 
of the reflected ray, as deduced by M. Jamin from theory and observa- 
tion respectively, and showed that for certain values of the angle of in- 
cidence, the differences were too great to be ascribed to errors of obser- 
vation. 
Examining then the value given by M. Cauchy for the amplitude of 
the reflected ray, he showed that this expression would admit of very 
great variation, without ceasing to represent with sufficient exactness 
the results of observation. E 
On the whole, assuming the experiments of M. Jamin to have been 
accurately made, he concluded that these expressions did not represent 
the facts with sufficient accuracy ; and further, that with regard, at least, 
to the value of the amplitude, the nature of the expression is such as 
to render an experimental proof of its truth very difficult. 
