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Inventory no. 51706 - Former Display Label


Gilt brass and steel. Signed, "Christoff Tressler der Elter Mechanicus Anno 1617".

One arm of the sector can move over a semicircle, engraved with a scale of degrees. On each arm is a scale graduated with transversals, over which can slide a sight. There is a third fixed sight at the joint.

On the back of the arms is a scale marked, "Linea Recta divisio".

This instrument should be compared with that described by Leonard Zubler in his Novum Instrumentum Geometricum, Basle, 1607. Like Zubler's instrument, it differs from conventional surveying instruments, in forming similar triangles by making two sets of sides in proportion and the included angles equal, instead of by making two sets of angles equal.

Lewis Evans Collection.

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