Signedon front: E. Ducretet et Cie / A PARIS
FunctionThis instrument was used to measure the number of vibrations of a body in a given time.
Here is the description given by Ganot: "For the sake of simplicity, let us first suppose that in the moveable disk A there are eighteen holes, and in the fixed plate B only one, which faces one of the upper holes. The wind from the bellows striking against the sides of the latter, the moveable disc begins to rotate, and the space between two of its consecutive holes closes the hole in the lower plate. But as the disc continues to turn from its acquired velocity two holes are again opposite each other, a new impulse is produced, and so on. During a complete revolution of the disc the lower hole is eighteen times open and eighteen times closed. A series of effluxes and stoppages is thus produced, which makes the air vibrate, and ultimately produces a sound when the successive impulses are sufficiently rapid. If the fixed plate, like the moving disc, has eighteen holes, each hole would separately produce the same effect as a single one, the sound would be eighteen times as intense, but the number of vibrations would not be increased." [...]
"Since the sound rises in proportion to the velocity of the disc A, the wind is forced until the desired sound is produced. The same current is kept up for a certain time, two minutes for example, and the number of turns read off. This number multiplied by 18, and divided by 120, indicates the number of vibrations in a second."
Historical AttributesCharles Cagniard de la Tour invented the siren in 1819, which it has been argued was a revolutionary instrument for generating and studying sound. It used pulses of air rather than vibrating strings or forks to make sound.
Primary SourcesE. Ducretet et Cie, Petit catalogue des instruments de précision de E. Ducretet et Cie (élève de M. Froment) (Paris, 1880), part 2, 167, no. 1652.
ProvenanceDavid P. Wheatland, Topsfield, MA; gift to CHSI.
Related WorksGanot, Elementary Treatise of Physics, Experimental and Applied, transl. by E. Atkinson, 2nd ed. (London: Longmans, Green and Co., 1867), 157-159.