534. Prof. Faraday on the Experimental Relations 
since the light which passes is nearly all polarized. On sub- 
jecting thin gold-leaf, or heated gold-leaf, or films of gold, or 
any preparations which required the support of glass, results of 
polarization were obtained, but the observations were imperfect 
because of the interfering effect of the glass. 
Proceeding to employ a polarized ray of light, it was found 
that a leaf of gold produced generally the same depolarizing 
effect as other transparent bodies. Thus, if a plate of glass be 
held perpendicular to the ray, or inclined to it either in the plane 
of polarization or at right angles to it, there is no depolarization ; 
but if inclined in the intermediate positions, the ray is more or 
less depolarized. So it is with gold-leaf; the same effects are 
produced by it. Further, the depolarization is accompanied by 
a rotation of the ray, and in this respect the quadrants alternate, 
the rotation being to the right-hand in two opposite quadrants, 
and to the left in the intervening quadrants. So it is with gold- 
leaf; the same effects are produced by it, and the rotation is in 
the same direction with that produced by glass, when inclined 
in the same quadrant. 
As further observation in this direction was stopped by the 
necessity of employing glass supports for the leaves, films, &c., 
I sought for a medium so near glass in its character, as should 
either reduce its effect to nothing, or render it so small as to 
cause its easy elimination. Hither camphine or sulphide of car- 
bon was found to answer the purpose with crown-glass ; but the 
latter, as it possesses no sensible power of rotation under ordi- 
nary circumstances, is to be preferred. Should a medium of 
higher optic force be required, it would probably be supplied by 
the use of that dangerous fluid, phosphorus dissolved in sulphide 
of carbon. A rectangular glass cell being provided, which did not 
itself affect the polarized ray, was placed in its course and filled 
to a certain height with sulphide of carbon. A plate of crown- 
glass was then introduced perpendicularly to the ray ; it did not 
affect it ; being inclined as before described, the effect on the ray 
was still sensible, the glass appearing to be, for all ordinary 
observations such as mine, quite as the medium about it. I 
could now introduce gold-leaf attached to glass into the course 
of the polarized ray, its condition as a flat film or plane being 
far finer than when stretched on a wire ring as before. It proved 
to be so far above the sulphide of carbon, as to have powers of 
depolarization apparently as great as those it had in air, and 
being inclined, brought in the image at the analyser exceedingly 
well. It was indeed very striking to see, when the plate was 
moved parallel to itself, the darkness when mere glass intervened, 
and the light which sprung up when the gold-leaf came into its 
place ; the opake metal and the transparent glass having appa- 
