Museo Galileo
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Folli's paper-ribbon hygrometer
    • Setting:
      Room IX
    • Inventor:
      Francesco Folli
    • Maker:
      unknown
    • Date:
      second half 17th cent.
    • Materials:
      wood, brass
    • Dimensions:
      length 711 mm, height 238 mm
    • Inventory:
      2434
    • Folli's paper-ribbon hygrometer (Inv. 2434)

Type of hygrometer invented by Francesco Folli c. 1660. A square-sectioned wooden rod carries a small roll at each end, on which is wrapped the end of a paper ribbon serving as a hygroscopic substance. The center of the rod holds a support for a decorated brass dial fitted with a circular graduated scale. The dial is integral with a pointer that, by means of a simple mechanical system, indicates the changes in ribbon length due to the variations in atmospheric humidity.