196 



K. TAKIZAWA. 



In conclusion, it may be .stated that the phenomena described 

 are in no way peculiar to the mica fihn. Any thin film can he used. 

 The same phenomena 'twere observed hy means of a thin air film 

 between two achromatic prisms. I'lie observation of course, much 

 more difficult than Avith a mica film. 



