Prisms, Liquid-Filled

   The multiple liquid-filled prism is related to the polyprism in which the refraction and dispersion of a number of types of glass can be observed and compared. The iron footed example at the right is at St. Mary's College and probably dates from about 1900. The very similar one at the left at Dartmouth College may be by Lerebours et Secretan. If so, it is listed at 35 francs in the 1853 catalogue. These can be tilted slightly on an axis running through the centers of the compartments. At the middle is an unmarked multiple liquid prism at the Smithsonian Institution; this has a tilt adjustment beneath its compartments.
  From Ganot's Physics (1883): "The prism with variable angle is used for showing that the angle of deviation increases with the refracting angle of the prism. It consists of two parallel brass plates fixed on a support. Between these are two glass plates, moving on a hinge, with some friction against the plates, so as to close it. When water is poured into the vessel the angle may be varied at will. If a ray of light be allowed to fall on one of them, by inclining the other more, the angle of the prism increases and the deviation of the ray is seen to increase."

   At the left is a Duboscq prism at the Smithsonian Institution. 

   Below: At the left is an unmarked example from Grinnell College in Iowa; by comparison with one below it was made by Max Kohl. In the middle is a Duboscq variable-angle prism in the Garland Collection of Classic Physics Apparatus at Vanderbilt University that was purchased about 1875. The unmarked example at the right is at Union College

   Both of these variable-angle, liquid-filled prisms are by Max Kohl. In the 1900 Kohl catalog the one at the right (at Cornell University) is listed as "Prism with adjustable angle for liquids, on stand... 30 Marks" (about $7). The one at the right, from the Greenslade Collection, is listed as "The same, better make, with graduations, 44 marks." But, the graduations are missing.  
  This is is the prism designed by J. P. Biot to hold volatile (an smelly) liquids, such as carbon disulphide. It was made by Lerebours et Secretan, and was listed at 90 francs (about $18) in their 1853 catalogue. This example has three compartments; with two compartments it was 75 francs, and with one compartment was 60 francs.

   At the left is a prism at the United States Military Academy at West Point, New York. On the right-hand side is a prism bought by Prof. F.A.P. Barnard for the University of Mississippi in the second half of the 1850s.

   This example of Silbermann's prism is at Union College in Schenectady, New York. 

   While the prism itself is clearly of French manufacture, it is described in the Max Kohl catalogue (ca. 1900) as "Silbermann's prism for showing that the deflection increases when the angle of refraction is growing." The prism is filled with water, alcohol or some other liquid, and the apparatus is then tilted backward to change the angles of incidence and refraction of the incoming beam.

   J. T. Silbermann, a Frenchman, invented the apparatus about fifty years earlier.

   This cubical box is listed in the 1853 catalogue of Lerebours et Secretan of Paris at 36 francs. The Duboscq/Pellin catalogue, ca. 1900, describes a similar piece of apparatus at 45 francs.

   The box, divided diagonally by a glass plate, is used for refraction studies. My assumption is that the two sides were filled with different liquids, allowing the index of refraction of one liquid to be found with respect to the other using angle measurements and Snell's law. 

   The apparatus is at Allegheny College in Meadville, Pennsylvania. 

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