An instrument used by surveyors for taking angles. It consists of a brass index, and circle, all of a piece; on the circle is a
chart, divided into 360 degrees. There are also two sights to screw on and slide up and down the index; also a
spangle and
socket screwed on the back side of the circle to put the head of the staff in.
1. A surveying instrument, for taking horizontal angles and bearings; a
surveyor's compass. It consists of a compass whose needle plays over a circle graduated to 360¡, and of a horizontal brass bar at the ends of which are standards with narrow slits for sighting, supported on a
tripod by a ball and
socket joint.
2. A graduated wheel for measuring tires; a
tire circle.
