Museo Galileo
Virtual Museum
Coulomb magnetic declination compass
    • Setting:
      Room XVI
    • Inventor:
      Charles Augustin Coulomb
    • Maker:
      Giovanni Fortini
    • Place:
    • Date:
    • Materials:
      marble, brass, copper, steel
    • Dimensions:
      base 690x320 mm, length 490 mm (needle), suspension tube height 500 mm
    • Inventory:
    • Coulomb magnetic declination compass (Inv. 918)

The massive marble base with leveling screws has a rectangular trough containing a long asymmetric magnetic needle. The trough is surmounted by two profiled marble arches connected at the top by a marble cross-piece with two openings. Through one of the openings passes a glass tube with brass finishings. The other opening is empty and accommodates the microscope currently associated with item inv 924. This type of inclinometer is fairly similar to those described by Charles-Augustin Coulomb in 1785. The wire suspension made the instrument highly sensitive, while its massive structure made it extremely stable. In the instruments he designed, Coulomb exploited the results of his detailed research on wire torsion and magnetization. This specimen was made by Giovanni Fortini for the Museo di Fisica e Storia Naturale of Florence, and was thus formerly in the Lorraine collections.