Hair hygrometer

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A hair hygrometer measures atmospheric humidity, using human hair as its hydroscopic, or moisture-absorbing, material. This example was made around 1790, probably by Haas & Hurter, scientific instrument makers based in London.

The hygrometer has a circular dial signed 'Haas & Hurter/LONDON'. Below the dial is the hydroscopic element encased in brass cylinders. As moisture is absorbed or evaporates, the hair lengthens or shortens, turning the pointer.

This instrument is adapted from a design published by the Swiss Horace Benedict de Saussure (1740-99) in 1783. Jacob Bernhard Haas (1753-1828) was in partnership with Johann Heinrich Hurter (1734-1799) in London between around 1790 and 1795.

Record details

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• Online ID: 000-100-102-709-C
• Image Rights Holder: National Museums Scotland
• Project: National Museums Scotland
  Project description   View all records in project
• Ref: National Museums Scotland  T.1967.14
• Date: 1790
  c. 1790
  
• Material: Brass cylinders, mahogany box. Inscription: Haas & Hurter, LONDON
  Hygrometer, hair / box
  
• Dimensions: 11.63" L x 2.38" D
  
• What: Hygrometer, hair / box
  
• Subject: 10. METEOROLOGY (Departmental Classification)
  
• Who: Haas and Hurter, London (Maker)
  
• Where: England, London
  
• Event:
• Description: Hair hygrometer, in a mahogany box, by Haas and Hurter of Londonc. 1790
  
• References:
  • Middleton, W. E. Knowles, Invention of the Meteorological Instruments. Baltimore, 1969, p 110 
  • Reis, A. Estacia dos, Uma Oficina de instrumentos matematicos e nauticos (1800-65), Lisbon: 1991, p 65 & fig 9 
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