266 PRINCIPLES OF CRYSTALLOGRAPHY. 



movement of light in crystals resulted the ellipsoid of polarization for 

 the derivation of all special rules. The relations of symmetrj^ of the 

 separate systems of crystallization allow us to discover in a very simple 

 manner the nature of the ellipsoid of polarization, and with it the optical 

 characters of every system, with which we have completed the object 

 of this memoir. 



