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Gunner's Caliper
Signed by Lorenzo Batecin
16th century; Venice
Gilt brass; 280 mm in length

The legs of the callipers are connected by a five-element compass hinge, each leg having a straight section, a quadrant arc and a point. One of these quadrant sections has an attached degree scale 0 to 90, divided to 10, subdivided to 5 and to 1, numbered by 10. This was read by a plummet (now missing). The quadrant shape formed by the other leg is filled by a plate, which is pierced to accommodate a magnetic compass with a needle and glazed cover, mounted in gimbals, and having a rose of 64 divisions, the four cardinal directions marked by abbreviated wind names. Above the compass is the hinged hour ring of an equinoctial dial, with hour lines 1 to 12 twice, a pivoted gnomon and a pivoted strut with a latitude scale from 30 to 60. The underside of the compass bowl is marked 'HOROLOGIVM ?QVINOXIALE', and its edge has the names of cities and their latitudes.

Above the quadrants is a clinometer arc with a degree scale on both sides 38 to 0 to 38, divided to 10, subdivided to 5 and to 1, numbered by 10. Above this, on a curved arm fixed to one leg and passing through the other, is the hole for a plumb-line for use with the clinometer scale, while the legs have a sighting holes for making the observations.

The curved arm is itself used to measure the size of shot placed between 2 points, one at the end of the clinometer scale, the other at the end of the quadrant scale, and the arm is graduated on its four sides for diameters and for weights in iron, lead and stone.

There is a signature on the inner face of one leg: 'Sr. Laur. batecin Inuentor'.

Jim Bennett

Istituto e Museo di Storia della Scienza, Firenze
Inventory no. 3176

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