MR. G. A. SCHOTT ON THE REFLECTION AND REFRACTION OF LIGHT. 879 
The values of B, E for the three pairS; are 
Beflection from flint-glass in air 
B = -00533, 
E= + 
•0562, ix^E = 
+ -0908 
?5 
,, air in flint-glass 
'0050, 
— 
•0861, 
- -0861 
55 
,, flint-glass in water 
•0120, 
I- 
•0737, 
+ -1186 
.* J 
,, water in flint-glass 
•0100, 
— 
•0751, 
- -1004 
55 
,, crown-glass in air 
•00040, 
+ 
•0113, 
+ -0171 
55 
., air in crown-glass 
•00111 
— 
•0250, 
- -0250 
Here of course, is the absolute refractive index of the second medium. It will 
be seen that the relations B = B' and = — (p-iE)' are satisfied with fair accuracy 
for the first two pairs, whilst for the third they are only of the same order of 
magnitude. 
According to Cauchy and Jamin the ellipticities e, e’ in such cases ought to 
satisfy the relation — e'/e =These ratios — e'/e are 1741, 1’244, and 
3'446 instead of 1'616, 1"2I0, and 1‘515, and the agreement is less than for our 
theoretical formula. 
Of course it has throughout been assumed that the nature of the film of transition 
is the same in both sets of experiments. The outstanding difference from agreement 
may possibly be due to a change in the film. Drude AVied. Ann.,’ 38, p. 35) by 
observations on cleavage faces of calc-spar has shown that there is in that case a 
gradual change in the elliptic polarization during exposure, so that part of the effect 
at least must be ascribed to condensed air or dust, and it is quite possible that such 
a layer would be affected by atmospheric conditions. 
AVithout some assumption as to the law of variation of refractive index in the 
layer, there is no relation between the constants for sets of media other than 
those given above. Theoretically Cauchy’s constant for reflection from medium 
hii _ jg very 
H-i H-a 
(1) in medium (2) should satisfy the equation 
and 
A is determined with an accuracy only about -1 that of B, 
F .-1 E 
n M 15 55 9 55 
In the experiments of Kubz just quoted, the “ probable error” of -sr is about 3.5', that of o about 'OOGO 
of Hence, in this ca.se the accuracy for B is only about •0021/'01I2, or that of E. 
But in most cases the disparity is not so great. 
The last constant F is of the second order in and in most cases is only fromy„qoth to-dyth of E ; 
the exceptions being fluorspar—air essence of lavender—air and flint glass—-water and crown-glass 
— air, j—i. In the case of essence of lavender E is very small. The last four pairs involve the most 
inaccurate measurements of all those considered. The effect of E is to make the polarizing angle differ 
from Brewster’s angle by an amount 2 fh F radius or F degi’ees ; this for realgar is about ^°, for 
/'o /'o 
flint-glass—water about If", for most other substances or so. As it is unlikely that the polarizing 
angle can be determined with an accuracy of 1 minute of arc, it is clear that E is known only roughly. 
