Conical and Pyramidal Prisms
   The transparent glass cone will produce a circular spectrum, while the glass pyramid will produce a set of four spectra. 

   Most of this and similar apparatus that I have seen in American collections is French. For example, both of the Union College conical prisms at the right were made by the firm of Jules Duboscq of Paris. 

   Note that one of the conical prisms at Union is made of black glass, and so must be a device for illustrating the properties of light reflected from a smooth, conical surface


   The prisms below were all made by Lerebours and Secretan of Paris.

        St. Mary's College                Allegheny College                     Kenyon College                   Allegheny College

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