Photo by David Friend Productions, San Diego, California
18th C AMERICAN SURVEYOR'S WALNUT SEMI-CIRCUMFERENTOR
06-002. American, dated 1790 on the back, unsigned. Made of walnut, 8 5/8" x 5" x 1", with a 8 1/2"
diameter brass protractor mounted on top and a 5 5/8" x 1 1/4" trough compass inset in the center of
the protractor. The trough compass needle is 5 3/8" long and the original compass glass is sealed
in with wax. The sighting mechanism mounts on a screw with the original nut in the center of the
base of the protractor, with 5 1/8" tall sight vanes on each end and cutouts to read angles on the
protractor. There is a 13/16" diameter x 3/4" deep hole in the back for staff mounting. This
attractive early American surveying instrument is in very good overall condition, with original
patina on the brass and only minor age cracks in the wood. See page 69 and Plate XXXII in M.V.
Brewington's "The Peabody Collection of Navigating Instruments" for a picture and description of a
similar American semi-circumferentor (dated circa 1730).
