Sire's Polytrope
   Sire's Polytrope is used to demonstrate the effect of the earth's rotations on the movement of a rotating body. In this example the rotating body has been lost. Were it in place inside the gimbals in the upper right-hand part of the picture, this would easily be recognized as a form of gyroscope.

   A similar apparatus is described in English in the ca. 1900 catalogue of Max Kohl as "The apparatus is provided with bevel-wheels and serves for demonstrating the following laws: 1. That rotating axes place themselves parallelly; 2. that the rotation takes place in equal sense, from [which] is derived: the determination of the meridian and of the latitude of a place, the invariablness of the rotation-plane, the proof of the rotation of the earth on its own axis, the conical movement of the earth: precession of equinoxes, nutation and parallel advancement of the earth-axis in the space." It is obvious that this is a translation from the original German. It cost 250 marks, or about $60.

   This apparatus is listed at $65 in the 1913 catalogue of the Société Genovoise (Geneva) for the Construction of Physical and Mechanical Apparatus. It is on indefinite loan from King's College, London to the Smithsonian Institution in Washington, D.C.

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