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Started: nov 7, 2004
Last Update: dec 18, 2004

Le Quart de Cercle


The Quart de Cercle or quadrant was designed by Picard in 1667. It has a 38 inch radius and was used for triangulation. The two small telescopes, fitted with crosshairs made it possible to measure with extreme accuracy. Picard used it during the research he did in 1669 for his Mesure de la Terre, that was published in 1671.
It was extensively discussed in Mesure de la Terre for which S. Le Clerc made the illustrations.