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Galileo Galilei, Compasso geometrico e militare
Galileo Galilei, Geometric and military compasses

c. 1606
Brass; length 25,6 cm, width (open) 36 cm
Florence, Istituto e Museo di Storia della Scienza, inv. 2430

Thanks to 7 scales marked on the legs, this instrument was able to solve all the arithmetical and geometrical problems of the abacus tradition. Thanks to other scales on the removable quadrant, it could act as a gunner’s square, astronomical quadrant, clinometer and quadrant for measuring by sight.