English-Style Sector

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This yellowed ivory instrument has two rectangular arms with flat edges and is held together by a circular brass hinge. The lower arm is broken. The scales run from top to bottom on each arm. 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 3 to 45 degrees; log sine, running from 1 to 70 degrees; and logarithmic numbers, running from 1 to 10 twice. 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 divides one foot into 100 increments and 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 18th-century English-style sectors are not present. Spanning both arms on the outer edge is a scale of inches, running from 12 to 1 and divided to tenths of an inch. Compare to MA*321755, MA*333937, and 1985.0580.06.
This sector may have been used at the New York Meteorological Observatory in Central Park, established and directed by Daniel Draper from 1868 to 1911.
References: Christopher J. Sangwin, "Edmund Gunter and the Sector," January 21, 2003, http://web.mat.bham.ac.uk/C.J.Sangwin/Sliderules/sector.pdf; Robert S. Harding and Jeffrey L. Tate, "Draper Family Collection, ca. 1826–1936," Archives Center, National Museum of American History, http://amhistory.si.edu/archives/d8121.htm.
Currently not on view
Currently not on view
date made
19th century
place made
United Kingdom: England
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
ID Number
accession number
catalog number
Credit Line
Gift of John William Christopher Draper and James Christopher Draper
Rule, Calculating
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Data Source
National Museum of American History, Kenneth E. Behring Center


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