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Plane Table
Signed by James Kynvyn
Dated 1595; English
Brass; 467 x 355 mm

A rectangular plate has a border attached by a hinge on one side. On one side a square is occupied by a sinecal quadrant and a surveying quadrant, the alidade is missing. Raised edges on the sides opposite the pivot hole for the missing alidade have two scales, one a geometrical quadrant 0 to 120 to 0, divided to 10, subdivided to 5, to 1 and to 1/2 with alternate hatching, numbered by 5. Outside this is a degree scale, but marked by radiating divisions on a zigzag line, each straight section covering 21/2 degrees, so it is an unusual use of diagonals: the whole scale is 0 to 90, divided to 5, subdivided to 30 minutes and to 10 minutes, numbered by 5 with alternate whole degree divisions marked by 3 dots. The sinecal quadrant has side scales 0 to 500, divided to 100, subdivided to 10, to 2 and to 1 with alternate hatching, numbered by 10. A quadrant, divided to degrees but not numbered, is inscribed within the square, and straight lines are ruled across the quadrant for every 20 minutes; every fifth degree line is marked with a doted line and the central interval for every degree is indicated by a wavy line. Signed on this side: 'Iacobus ? Kynuyn ? fecit ? 1595 ?'.

The reverse has a border held by five hinges (one pin is missing), and secured by 5 pivoted catches. This border, when closed, surrounds a raised plate riveted to the border for the other side, and can be used to clomp a sheet of paper to the instrument in the manner of a plane table. There are five central holes for a mount (missing) for the table when in use. In the centre is a diagram for relating shadow square or geometrical square readings to degrees. The outer circle has a degree scale 0 to 360, divided to 10 degrees, subdivided to 30 minutes and by diagonals to 5 minutes, numbered by 10 degrees. Within this circle the 32 points of the compass are marked and initialled, and inscribed within this circle are four geometrical quadrants, each with scales 0 to 60 to 0, divided to 5, subdivided to 1, numbered by 5, and a second scale 0 to 12 to 0.

Jim Bennett

Istituto e Museo di Storia della Scienza, Firenze
Inventory no. 663

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