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Graphometer

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probably made in Paris

Graphometer
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A graphometer is a surveying instrument used for measuring angles. This brass example (pictured here with its leather case) was made in 1774, probably by Louis-Pierre-Florimond Lennel, a scientific instrument maker based in Paris.

The large graphometer, typical of French survey instruments of the period, has a telescopic sight, attached to a rotatable alidade. It consists of a pierced semicircular plate, carrying at its centre a silvered compass, contained in a glazed box suspended below the plate. A second, fixed, telescope is mounted below the plate.

The instrument may well have been used in the French National Survey as its leather case carries the official fleur-de-lys stamp. This survey took place throughout the 18th century, but never received sufficient state backing: triangulation work began in 1747, with funding withdrawn in 1756. By 1784 only Brittany was unsurveyed, and this was not completed until well after the French Revolution, in 1818.

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