Museo Galileo
Virtual Museum
Nautical hemisphere
    • Setting:
      Room V
    • Inventor:
      Michel Coignet
    • Maker:
      Charles Whitwell
    • Place:
    • Date:
      late 16th cent.
    • Materials:
    • Dimensions:
      diameter 280 mm
    • Inventory:
      1099, 1122
    • Nautical hemisphere (Inv. 1099, 1122)

The instrument, made by Charles Whitwell, consists of two superposed disks. On the front of the larger one is the maker's signature and a slit that may have served to fasten it to a support. On its rim are four diametrically opposing prominences carrying two right-angled semi-armillae. One of the prominences holds a suspension ring. Two other semi-armillae—one of which can be tilted—are attached to the four similar prominences on the smaller disk and rotate together with the latter around the center of the instrument. A diopter, pivoting on the center of the smaller disk, was used for sighting. This nautical hemisphere probably served to compute tides and is derived from a model invented by Michel Coignet c. 1580. Provenance: Robert Dudley bequest to the Medici collections.