Also 7 -er. [f. CIRCUMFERENT + -OR, -ER. of the agent.]
1. Surveying. An instrument consisting of a flat brass bar with sights at the ends and a circular brass box in the middle, containing a magnetic needle, which plays over a graduated circle; the whole being supported on a staff or tripod. (Now commonly superseded by the THEODOLITE.)
1610. W. Folkingham, Art of Survey, II. iv. 53. With Plaine-Table, Theodelite, Sector, Circumferentor.
1644. Nye, Gunnery, II. (1647), 36. Circumferenter, or Geometricall Square.
1697. Phil. Trans., XIX. 625. The Circumferentor, by which the Down Survey, or Sir William Petty’s Survey of Ireland was taken.
1760. S. Wyld (title), The Practical Surveyor,… by the Plain-Table, Theodolite, or Circumferentor.
1864. Jeaffreson, R. Stephenson, I. 48 (L.).
2. An instrument for measuring the circumference of a wheel; a tire-measurer, tire-circle.
1874. Knight, Dict. Mech.
