Friday, June 14, 2013

Excerpt 3

Beauty from the Symmetry of Their Form:

The Invention of the Kaleidoscope

In 1817, Sir David Brewster patented the kaleidoscope. Others had noticed the effect of two mirrors meeting at an angle before, as recounted in this selection from an 1818 article in The Edinburgh Magazine and Literary Miscellany:
The repetition and reversion of images in a glass is noticed in the Masfiti Naturalis of Baptista Porta, a Neapolitan nobleman, who flourished about the latter part of the sixteenth century, and was distinguished for his zeal in promoting philosophical pursuits…
In the Ars Magna Lucís et Umbra of Kircher, printed in 1646, we have an account of the same circumstance, and also of the repetition of the sectors round the centre of the circle:
“A wonderful property,” says he, “and one which has not, as far as I know, been observed by any one, is exhibited with two specula, so constructed as to open and shut like a book; and placed on any plane in which you have described a semicircle divided into its degrees. For, if the point in which the specula meet be placed in the centre of the semicircle, so that the side of each speculum shall stand upon the diameter, the image of an object will only be seen once, and two objects will appear, one without the specula, the true one,—and one within, the image. But if the sides be placed at an angle of 120°, you will see the image of the object within the specula twice, that is, along with the real image, three objects But if the specula intercept an angle of 90°, you will see the circle divided into four parts, and four objects; in the same manner, at an angle of 60°, you will see a hexagon with six objects.’1
He then applies the principle to some curious contrivances which, by his own account, filled his spectators with astonishment. With one candle he shows how to make a complete chandelier. “With angles of 120°, 72°, and 45°, you will see,” says he, “with no less delight than admiration, a chandelier with three, with five, and with eight branches.”

1 Athanasius Kircher, Ars Magna Lucís et Umbra, 1646

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