What is "bow-compass"

Bow-compass \Bow"-com`pass\, n.; pl. Bow-compasses.

1. An arcograph.

2. 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.

3. A pair of compasses, with a bow or arched plate riveted to one of the legs, and passing through the other.