| David Brewster (1781-1868) is perhaps best
known for his invention of the Kaleidoscope, about which he wrote a treatise
published in 1819. In the first part of his scientific career he did a
good deal of research in optics, but later turned to writing and editing
of scientific works as his main source of income.
In 1815 he observed the fringes produced when two thick, parallel-sided plates of glass of identical thickness were placed close to each other. The plates are located at one end of a brass tube that has a narrow slit at the other end; the inside of the tube is blackened to prevent reflections. The two plates can be seen at the end of the apparatus shown at the right. An adjusting screw for changing the angle of inclination of the two plates can be seen. The theory of the apparatus may be found in Thomas Preston, The Theory of Light, 2nd ed (London, Macmillan Co., 1895) pp 194-197.
This apparatus is in the collection of the United States Military Academy at West Point, New York, and was purchased from Duboscq of Paris about 1844. The brass tube is 30 cm in length.
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