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Inventory no. 17420 - Former Display Label


Brass; with folding tripod of wood, brass and steel. Unsigned and undated.

The graphometer, or surveying semicircle, was invented by Philip Danfrie, of Paris, about 1597. It is a triangulation instrument consisting of two alidades, one of which is fixed and has attached a semicircular scale of degrees, the other alidade being moveable over the scale of degrees. The graphometer was mounted on a ball and socket joint on a tripod, and either horizontal or vertical angles could be measured. The instrument shown here, unlike Danfrie's design, has a double moveable alidade.

[Orrery Collection, no. 50]
Lent by Christ Church

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