164 M. G. Quincke on the Optical Properties 



upon the cross lines. Thereby the direction of the incident 

 light was fixed. The metal plate stood perpendicular to the 

 same, and parallel to the axis of the goniometer, when the rays 

 reflected from it were thrown back upon the cross lines next 

 to it. 



If we call ol the azimuth of the incident light, then the ratio k 

 of the amplitudes S and P of the components of the light polar- 

 ized perpendicular and parallel to the plane of incidence, when 

 these have equal intensity in the incident light, is given by the 

 equation 



S_tan/3 m 



Putting a for the number of revolutions of the compensator 

 which are required to give to the rays leaving the compensator 



a difference of path equal to a quarter of an undulation -, p 



for the number of the revolutions read on the compensator 

 necessary to eliminate the difference of path 8 of the compo- 

 nents of the light which is either reflected from metal or trans- 

 mitted through metal, then is 8, expressed in fractions of a quarter 

 of an undulation, 



= £,* (2) 



The following Table gives under I the angle of incidence, 

 under p and p 1Q0 the observed revolutions of the compensator 

 according as one side or the other of the gold-leaf is presented 

 to the source of light j under /3 and /3 180 are given the corre- 

 sponding values of the restored polarization ; under p and /3 the 

 means of these values. Since the incident light was polarized under 

 the azimuth a = 45°, it follows that the tangent j3 gives directly the 

 ratio k of the amplitudes of the components polarized perpendicu- 

 larly and parallel to the plane of incidence. For comparison, the 

 values p and /3 are given for light which had been reflected from 

 a portion of the same gold-leaf. This last piece of gold-leaf had 

 been placed on distilled water, taken up with a plate of glass, 

 and then dried on the same plate of glass. Between the eye 

 and analyzing NicoPs prism a piece of gold-leaf was inserted in 

 the experiments with reflected light, in order to have light of the 

 same colour as that obtained in the experiments on transmitted 

 light. 



