English-Style Sector Signed William Harris

This brass instrument has two arms with flat edges, an undecorated hinge, and a central crossbar attached to the end of one arm that fits into a notch on the other arm to hold the sector open at a fixed acute angle. On one side and from the top down, each arm has a sine scale, running from 10 to 90 degrees; a tangent scale, running from 45 to 75 degrees; and a second tangent scale, running from 10 to 45 degrees. The top arm has a scale labeled "Rum." that runs from 1 to 8, and the lower arm has a scale labeled "Lon." that runs from 60 to 10. Spanning both arms on the outer edge are three scales: log tangents, running from 1 to 45 degrees and labeled "Tan."; log sines, running from 1 to 75 degrees and labeled "Sines"; and logarithmic, running from 1 to 10 twice and labeled "Num." This side is marked: W^m. Harris Holborn (/) London.

The other side has a double scale along the fold line for regular polygons, from about 8 to 4 sides. Each arm has a "line of lines" scale, running from 1 to 10; a secant scale, running from 30 to 75; and a scale of chords, running from 10 to 60. The upper arm has scales for the inclined meridian, chords, and sines, each running from 10 to 90. The lower arm has scales for tangents, running from 10 to 45; latitude, running from 10 to 90; and hours, running from I to VI. Spanning both arms along the outer edge is a scale of equal parts, running from 90 to 10; and a scale of inches, running from 12 to 1 and divided to tenths of an inch. On both sides of the instrument, the scales are small, worn, and difficult to read.

William Harris owned a workshop that made spectacles, telescopes, and mathematical and philosophical instruments on High Holburn Street in London from 1799 to 1839, when the workshop was renamed William Harris & Son.

References: Gloria Clifton, Directory of British Scientific Instrument Makers 1550–1851 (London: National Maritime Museum, 1995), 126; Adler Planetarium, Webster Signature Database, http://historydb.adlerplanetarium.org/signatures/.

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