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Hadley's Quadrant: Detail

The quadrant's lower index arm, which is adjusted along the vernier (fractionally subdivided scale) in order to read off the angle measured along the arc. To the left of the index arm is a magnifier that can be positioned over the vernier, making it easier to read.

Curator Sara Schechner demonstrates the use of a quadrant.

CHSI Inv. Number 1998-1-1663
Date: 1735
Jonathan Sisson
London, England

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