Museo Galileo
Virtual Museum
Folding rule
    • Setting:
      Room I
    • Maker:
      Antonio Bianchini
    • Place:
    • Date:
    • Materials:
      gilt brass
    • Dimensions:
      length 375 mm
    • Inventory:
    • Folding rule (Inv. 2514)
    • Folding rule (Inv. 2514)

Folding rule consisting of two wide, flat legs engraved with: the degree scale, the shadow square, the windrose, a scale of equal parts, and a list of forty-two European cities with their respective latitudes. On the legs are four folding viewers. The leg joint holds a magnetic compass complete with glass cover and magnetic needle; the hours are inscribed on the rim. Around the compass mount is a motto recalling the brevity of life. The instrument is signed by its maker, Antonio Bianchini, and dedicated to Cosimo I de' Medici. It appears in the Trattato di diversi istrumenti matematici (a manuscript dated to 1593) by Antonio Santucci under the name of "Gran Regola di Tolomeo" [Great rule of Ptolemy]. The instrument was used to measure terrestrial and astronomical distances with the help of a ruler (now missing) hinged to one of the legs. The ruler served as the base of the many triangles formed by folding the instrument. The base represented a measure proportional to the distance to be calculated. Identical to item inv. 2511, apart from the material and the format of the maker's signature. Provenance: Medici collections.