Hair Hygrometer

A human hair stretched or shrank with the dampness of the air, moving a pointer that showed humidity.

Date: ca 1829
Maker: Fortin et Herrmann
Place: France: Île-de-France, Paris
Dimensions: overall: 13 in x 3 7/8 in x 2 1/8 in; 33.02 cm x 9.8425 cm x 5.3975 cm
Museum: National Museum of American History
Credit line: U.S. Military Academy

Brass hygrometer with silvered scale inscribed "Fortin et Hermann, Genve. [?] à Paris" and "Humidité" (humidity) and "Secheresse" (dryness). Nicholas Fortin, the senior member of this firm, was an instrument maker well known for his improved mercury barometer. The U.S. Military Academy bought this example in the early 1830s.

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