Jamin's Divided Circle
   This apparatus is listed in the 1885 catalogue of Jules Duboscq of Paris as the Grand Circle of MM. Jamin et Sénnarmont. It was designed for the study of the laws of polarization of light reflected from crystalline substances, from liquids and from metals. It could also be also to measure indices of refraction. With its accessories it cost 1000 francs (about $200).

   The circle is an early example of an ellipsometer, used to study the reflection of light at or near Brewster's angle. The Frenchman, Jules Jamin, described it in an 1850 paper in the Annales de Chemie et de Physique. Jamin developed one of the first interferometers in 1856, and was well-known for his lavishly-illustrated, two-volume textbook.

   The instrument at the left is in the Garland Collection of Classic Physics Apparatus at Vanderbilt University; on the right is an example from Washington and Lee University.

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