Surveying Compass

Surveying Compass in Case. Thomas Jefferson Foundation, Inc.

Artist/Maker: John Bleuler (1757-1829)

Created: 1791-1829

Origin/Purchase: England

Materials: brass, steel, glass; case: wood (probably pine), paper

Dimensions: L: 39.4 (15 1/2 in.); H: 5.1 (2 in.); 17.8 (7 in.) with sights; dial: D: 15.2 (6 in.); Depth: 2 (3/4 in.); case: 29.4 × 17.1 × 6.7 (15 1/2 × 6 3/4 × 2 5/8 in.)

Provenance: John Hartwell Cocke; by descent to John Page Elliott; by gift and purchase to the Thomas Jefferson Foundation in 1992

Accession Number: 1992-4-3

Historical Notes: Although no references to the English instrument maker John Bleuler appear in Jefferson's records, this instrument may have been his, as John Hartwell Cocke purchased other surveying equipment from Jefferson's estate in 1827.^[1]

Jefferson almost certainly owned and used a plain surveying compass (in England it was known as a circumferentor). It would have been his major surveying tool before he acquired his Ramsden theodolite in 1778. He later expanded his surveying equipment by purchasing more portable circumferentors — called graphometers in England. While in London in 1786 he bought "a pocket graphometer by Cole," and in 1805 he asked Thomas Freeman, leader of the Red River exploring expedition, to buy him "an accurate compass for surveying, with 2. pair of sights moving concentrically, an outer graduated circle with a Nonius to take angles accurately without regard to the needle, with it’s ball & socket & staff." He reflected the still-present confusion in terminology when he added that he believed "they are called Circumferentors but is not certain." He added it to his instrument list as "a common Theodolite or Graphometer," eight inches in diameter and costing $54.37.^[2]

-Text from Stein, Worlds, 360

Further Sources

• Bedini, Silvio A. With Compass and Chain: Early American Surveyors and their Instruments. Frederick, MD: Professional Surveyors Pub. Co., 2001.