Wiedemann's Galvanometer
   Gustav H. Wiedemann, along with Helmholtz and Tyndall, was a pupil of Heinrich Gustav Magnus at Berlin. His version of the Helmholtz type of tangent galvanometer was developed in 1874. The coils on either side of the suspended needle could be moved back and forth to change the sensitivity, and a series of coils, ranging from 2000 Ohms down to about 6 Ohms, was provided. Damping was provided by surrounding the magnet with a copper ring (at the left below) or a copper sphere (at the right below; developed by M.T. Edelmann, who worked with Wiedemann). He employed Gauss and Weber's method of using a mirror attached to the lower part of the torsion fiber to act as an optical lever to increase the sensitivity of the instrument.

   The instrument at VMI was manufactured by Edelmann of Munich, while the Washington and Lee instrument was sold by Queen of Philadelphia. A somewhat similar galvanometer is listed in the 1887 Queen catalogue of electrical testing apparatus at $156.00.
                       Washington and Lee University                                                     Virginia Military Institute
   This example of Wiedemann's Galvanometer bears the label of James W. Queen of Philadelphia. This firm imported it from Europe. 

   It is in the Millington/Barnard Collection at the University of Missippi Museum. 

   This example of Wiedemann's galvanometer is in the collection of historical instruments at Case Western Reserve University in Cleveland, Ohio.

   It has the label of James W. Queen & Co. of Philadelphia, who imported it. This is "Prof. Braun's large dead beat reflecting galvanometer", with "coils that are free to moved by hand" on the round rod. It is listed in the Queen 1887 Catalogue and Price List of Electrical Testing Apparatus" at $156,

   A good example of a piece of non-commercial apparatus is the Wiedemann galvanometer made about 1900 by Prof. Joseph Naylor of DePauw University.

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