90 



JAMIX ON METALLIC REFLEXION. 



Mirror-metal. — Azimuth of the minor axis of the ellipse of 

 oscillation of a molecule of (sther after reflexion. 



Not only is it interesting to know the direction of the axes of 

 the ellipse, inasmuch as it furnishes us with a verification of 

 theoretical formulae, but the determination alone of this unknown 



_ J2 



quantity will gi\'e us the ratio of the intensities ^ of the rays re- 

 flected in the principal azimuths. 



Let us call to mind that the azimuth of the principal section, 

 for which the two images are equal, is given by the formula 



tan 2 w' = — 



cot 2 a 



cosS 



(16.) 



