English-Style Sector

This ivory instrument has two rectangular arms with flat edges and is held together by a circular brass hinge. The scales run from top to bottom on each arm, unlike the paired double scales on Italian and French sectors. On one side, each arm has a sine scale, running from 10 to 80 degrees; a tangent scale, running from 45 to 75 degrees; and a second tangent scale, running from 10 to 45 degrees. Spanning both arms on the outer edge are three scales: log tangent, running from 2 to 40 degrees; log sine, running from 1 to 70 degrees; and logarithmic, running from 2 to 10 and then from 1 to 10. A double line separates these scales from the inner, diagonal set of scales. The top face of the instrument has a scale of equal parts that runs from 90 to 10. There is no maker's mark.
The other side has a double scale along the fold line for regular polygons, labeled POL and running from 12 to 4 sides. Each arm has a scale of equal parts, running from 1 to 10 and labeled L; a secant scale, running from 20 to 75 and labeled S; and a scale of chords, running from 10 to 60 and labeled C. The scales for dialing typically found on English-style sectors are not present. Spanning both arms on the outer edge is a scale of inches, running from 11 to 1 and divided to tenths of an inch. The sector likely dates to the mid-19th century. Compare to MA*335351, MA*333937, and MA*321755.
The donor kept this object and 1985.0580.01 in a blue cardboard box that originally held 12 Eldorado 4H no. 2 pencils made by the Joseph Dixon Crucible Company of Jersey City, N.J. Dixon sold this brand from 1917 to the mid-1950s.
Reference: Dennis B. Smith, "Wood Cased Drafting Pencils," Leadholder: The Drafting Pencil Museum, http://leadholder.com/wood-dixon-eldorado.html.
Currently not on view
Object Name
date made
19th century
Physical Description
ivory (overall material)
brass (overall material)
overall: .3 cm x 16 cm x 3.5 cm; 1/8 in x 6 5/16 in x 1 3/8 in
place made
United Kingdom: England
ID Number
catalog number
accession number
Science & Mathematics
Rule, Calculating
See more items in
Medicine and Science: Mathematics
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Gift of Mrs. Albert Haertlein
Additional Media

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