Polarising Filter

Polarizing filter in a wooden box. The filter consists of two parts: one is a brass tube with a round disc at each end, one of which is arranged as an eyepiece. In the tube a prism is set in wood. The other part is also a brass tube, which fits into the first, and has a large round disc at one end; a prism is also arranged in this part. When assembled, the pointer on the disc of the first part opposite the eyepiece indicates the angle on the scale on the large disc of the second part: this scale goes from 350° to 100°. At 360° or 0° maximum polarization of the light is obtained.