Later 16th century; Italian
Brass; 440 mm in length
There are five rules held together by four pivots, one fixed at the end of the central staff securing two arms, one on a mount sliding on the staff securing the other two arms, and two pivots connecting the pairs of arms. One side of the staff has a linear scale 0 to 150, divided to 10, subdivided to 5 and to 1, numbered by 10, with a second, non-linear scale with graduations between 1 and 120. One rim of the staff has two non-linear scales, one with graduations 3 to 12, numbered by 1, the other 12 to 3, numbered by 1, and is shorter. The two shorter arms (which are the fore-arms) have linear scales 0 to 63, divided to 10, subdivided to 5 and to 1, numbered by 10; the longer have scales 0 to 90, similarly divided and numbered.
The reverse has a non-linear but unnumbered scale on the staff, with symbols for three directions, mostly given as initials of wind names. The shorter arms are blank on the reverse, but the longer have shadow square or geometrical quadrant scales.
Istituto e Museo di Storia della Scienza, Firenze
Inventory no. 647
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