16th century; German
Wood and gilt brass; 847 mm in length
Wooden (fruit-wood) rod with brass ends, one with a locating stud, the other with a ring handle. The is a second handle, in the form of a loop, in the middle of the rod. A brass disc, engraved on one side, is mounted on the rod by an eccentric pivot. Right angled lines extending to the letters 'A', 'B', 'C' and 'D' and marked 'Basus' and 'Cathetus', intersect at the pivot, on which is centred a circle with two adjacent quadrants marked for the angles of right-angled triangles whose sides are in the ratios from 1 to 6. Thus, each of these quadrants, together forming a semicircle, is marked 6 to 1 to 6, while on the opposite side of the disc, but now marked on the rim beyond the circle, is a degree scale which gives the corresponding angles, that is the divisions radiate from the pivot, not the centre of the disc. The degree scale is 0 to 90 to 0, divided to 10, subdivided to 5 and to 1, numbered by 10. An index arm marked 'Hypothenusa' is mounted on the rod.
A shaped steel rod pivots on the wooden rod and extends to the pivot of the disc. It is moved by a spring action against the wooden rod.
The instrument is incomplete.
Istituto e Museo di Storia della Scienza, Firenze
Inventory no. 691
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