bow-compass

CIDE DICTIONARY

bow-compass, n.

An arcograph. [1913 Webster]
A small pair of compasses, one leg of which carries a pencil, or a pen, for drawing circles. Its legs are often connected by a bow-shaped spring, instead of by a joint. [1913 Webster]
A pair of compasses, with a bow or arched plate riveted to one of the legs, and passing through the other. [1913 Webster]

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