Description:
A basin is made of one pivoting and one fixed glass-plated walls, the angle of the former being measured on a graduated scale ranging from 0 to 45 divided in single degrees. The position of the moving wall is made on the curved threaded rod, on which a screw has been added. The basin can be filled with liquids of various densities to show how light is bent. The instrument is supported by a brass column that rests on a turned wooden base.