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Note on a simple form of Reflecting Polariser. 

 By Frederic J. Cheshire. 



{Read May iWi, 1902.) 



When light is incident upon a plane crown-glass surface, the 

 reflected beam contains the miiximum proportion of polarised 

 light when the angle of incidence is about 56 1^ A slip of 



ground glass G, about 1| x 2| inches, with a coat of Aspinall's 

 black enamel on its back and ground side, is mounted, therefore, 

 at an inclination of 33|° on a short spindle A in the axis of the 

 microscope, which can be rotated by a milled head B. The 

 polariser is mounted on the tailpiece in the same way as the 

 usual mirror. By this construction it is obvious that, however 

 the spindle A may be rotated to bring the lamp flame or other 

 light source into view, any light that passes along the axis after 

 reflection must be fully polarised without any adjustment for the 

 polarising angle. The analyser must of course be capable of 



