|Friedrich Wilhelm Georg Kohlrausch (1840-1910) was a professor of physics at Göttingen, Zürich, Würtzburg, Strasbourg and Berlin during his career. He wrote a widely-used book on methods of experimental physics, and developed improved measurement techniques in electricity and magnetism.|
|| The Catalogue and Price-List of Electrical Testing
Apparatus, issued by James W. Queen & Co. of Philadelphia in 1887,
shows the upper version of the Kohlrausch Universal Bridge (from the Denison
University Collection). The catalogue description is:
"Professor Kohlrausch's Universal Rheometer, or Bridge and Rheometer combined; with induction coil, for measuring the resistance of solid and fluid conductors, batteries, etc., by means of galvanometer or telephone ... $52.00." The telephone receiver was an extra $6.00.
The prefix rheo, introduced by Wheatstone in 1837, refers to resistance.
The second piece of apparatus, from Washington and Lee
University, can be found in the 1921 catalogue of E. Leybold's Nachfolger
[Successors] of Cologne at a price of $38. The text reads:
The Kohlrausch bridge in the third picture is on display
at the Garland Collection of Classical Physics Apparatus at Vanderbilt
University. It was made by Hartmann & Braun of Frankfort am Main, and
is clearly the same as the Queen apparatus from Denison University, showing
that Queen was the importer.
The bottom picture shows a similar Hartmann & Braun Kohlrausch
bridge in the collection of the University of Vermont in Burlington.