Epact Scientific Instruments of Medieval and Renaissance Europe

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Theodolite
Unsigned
16th century; Italian
Gilt and enamelled brass; 480 mm in length

The overall shape is as a circumferentor with two diametric arms extending from either side of a central disc, the arms reinforced by decorative scrolls and terminating in decorated sights shaped to provide both vertical and horizontal edges for alignment. The central plate is divided into eight named winds, each with a 45-degree scale, divided to 5, subdivided to 1, numbered by 5. Inscribed within the wind scale is a quadruple shadow square, each quadrant with scales 0 to 12 to 0, divided to 1, subdivided to 1/2 and to 1/4, numbered by 1. The remainder of the plate has elaborate foliate decoration. A central circular compass box has a target line and a pin mount for a magnetic needle (the needle and cover are missing). It is surrounded by a ring which turns around the centre, and attached to it are the counterchanged arms of an alidade moving along the circle of winds and the shadow squares.

Underneath is a vertical sundial with lines for Italian hours, and a vertical adjustment with a racked semicircle, with a degree scale comprising four 45-degree sections, divided to 5, subdivided to 1, numbered by 5, and an inscribed double shadow square. The free space on this plate is also decorated in a similar manner.

Jim Bennett

Istituto e Museo di Storia della Scienza, Firenze
Inventory no. 144

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