Vibration Microscope

You looked through it at a vibrating tuning fork, and the pattern you saw let you check its exact pitch.

Maker: Rudolph Koenig
Place: France: Île-de-France, Paris
Dimensions: overall: 17 1/8 in x 9 1/2 in x 9 1/2 in; 43.4975 cm x 24.13 cm x 24.13 cm
Museum: National Museum of American History
Credit line: United States Military Academy

The vibration microscope (or optical comparator) was used to calibrate the frequency of a tuning fork in terms of a fork of known frequency. Hermann von Helmholtz invented the form; Jules Antoine Lissajous introduced that in which the reference fork is driven electromagnetically. This electromagnetic example is inscribed “Rudolph Koenig a Paris” and was used at the U.S. Military Academy at West Point.

Ref: Rudolph Koenig, Catalogue des Appareils d’Acoustique (Paris, 1865), p. 12.

Rudolph Koenig, Catalogue des Appareils d’Acoustique (Paris, 1889), p. 83.

The museum's own record (Smithsonian, National Museum of American History)