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Folding Rule
Signed by Humfrey Cole
Dated 1575; London
Brass; 350 mm in length

A folding rule with a flat three-leaf hinge, each arm with shaped and decorated compass points. The hinge has a semicircular degree scale 0 to 180, divided to 10, subdivided to 2, numbered by 10, and also numbered 180 to 0. This scale is used with two pairs of hinged shaped sights folding into recesses in the arms, with the scales and numbering continuing across them when folded.

The outer edge of the side with the sights has a 20-inch scale, continuous when the rule is opened out, the inch divisions numbered 1 to 24 along the centre of the rule; on one arm each inch is divided to 1/2, subdivided to 1/4 and to 1/8, while on the other each has a different division as marked: 16, 32, 64, 12, 24, 18, 20, 30, 14, 28, 21, 11. This side also has scales for 'Borde measure' and 'Timber Measure', the former non-linear 7 to 36 decreasing, divided to 1, numbered by 1; the latter non-linear 9 to 36 decreasing, divided to 1, numbered by 1.

A pair of linear scales [0] to 500, divided to 10, subdivided to 2, numbered by 10, originates at the central hole in the hinge and is marked on the inside rims of the arms and across the hinge.

As the hinge is opened there are positions at 90 and 180 degrees between the arms, where holes in the hinge leaves coincide and a peg can be used to clamp the arms. In the 90-degree position, quadrant scales on the other side of the arms can be used for measuring altitudes, and there is a hole for attaching a plumb-line (not extant). There are three such scales: a degree scale ('Quadrans') 0 to 65, divided to 10, subdivided to 5 and to 1, numbered by 5; and two geometrical quadrant scales ('Quadratum Geometricum'), one ('Latus Vmbra Versa') 0 to 60, divided to 15, subdivided to 5 and to 1, numbered by 5, and one ('Latus Vmbra Recta'), similarly divided but numbered 60 to 0. Signed on this side: '[star] Humfrey ? ? C?le ? 1575[star]'

Jim Bennett

Istituto e Museo di Storia della Scienza, Firenze
Inventory no. 2527

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