A rare hair hygrometer to the Saussure design.
Signed: Hygrometre selon Saussure,
Ed. Sacre a Bruxelles
Arched brass frame with scale of relative humidity devided into 100 degrees with the ends marked Secheresse and Humidite. The index pointer with contra weight is driven by a central double pulley. Thermometer scale calibrated into Centrigrade. Suspension ring.
This type of hygrometer was invented by Horace Benedict de Saussure (1740-1799).
Dimensions: 27 cm high and 8,5 cm wide.
France, ca 1840.