Kaleidoscope
   The Kaleidoscope that we usually see today consists of three long, narrow mirrors arranged in a circle, with movable, transparent, colored objects at one end and an eyepiece at the other. It was invented by David Brewster (1781-1868) in 1816. Much of Brewster's scientific work was directed toward optics, where his work with polarized light led him toward the discovery in 1811 of Brewster's angle, the angle of incidence at which light reflected from a dielectric surface is 100% plane polarized in a direction perpendicular to the plane of incidence. Brewster wrote extensively about science and is best known today for his Treatise on Optics and Letters on Natural Magic (both 1831) and his Life of Sir Isaac Newton (1832).

   In 1819 Brewster wrote A Treatise on the Kaleidoscope, an exhaustive account that also included information on mirror configurations other than the usual three-sided, equiangular arrangement.
   The parlor-type kaleidoscope at the left above is in the collection of historical instruments at Harvard University. It is marked " G. G. Bush - Claremont, NY, pat Nov.. 11, 1873". The example at the right is from St. Mary's College in Notre Dame, Indiana, and is also a Bush instrument, although it has lost its stand. This is by far the most common 19th century kaleidoscope and often turns up on email auctions, although with prices far, far above the $2.50 at which Queen of Philadelphia sold a very similar model in 1895.
   The kaleidoscope at the left is in the Garland Collection of Classical Physics Apparatus at Vanderbilt University. The apparatus has only two mirrors, unlike the usual three, and the mirrors can be set at various angles by means of setting circles. 

   It was made by the firm of Jules Duboscq of Paris, and probably purchased ca. 1875. In the 1885 Duboscq catalogue a simple, Brewster-type kaleidoscope is listed at 15 francs ($3.00).
 
 




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