Accession No
2819
Brief Description
gunter sector, by Elias Allen, English, c. 1630
Origin
England; London; The Strand
Maker
Allen, Elias
Class
calculating; mathematics
Earliest Date
1630
Latest Date
1630
Inscription Date
Material
metal (brass)
Dimensions
l 248 mm x 57 mm
Special Collection
Provenance
Purchased from Peter Delehar, London, England, 20/02/1982. Purchased with assistance from the Preservation Fund administered by the Science Museum (PRISM).
Inscription
‘Elias Allen fecit’ (inner edge)
Description Notes
Brass Gunter sector with folding friction leaf. Engraved with lines as illustrated in frontispiece of E. Gunter, “The description and use of the sector” London 1624, namely (on recto): lines of lines, lines of solids, lines of inscribed bodies in the same sphere, lines of equated bodies, lines of metals, meridian line; (on verso): lines of superficies, lines of sines, line of tangents, line of secants, lines of quadrature, lines of segments; (on edge) line of inches (divided to 0.05 and numbered 0-9 and 9-18) line of tangents.
Condition good; complete.
References
Events
Description
Sectors were used for calculation by navigators, surveyors, gunners, and draftsmen (and, famously, by Galileo) from the about the mid-16th Century to the mid-19th Century. During the 16th Century, they were used as general mathematical tools, but the introduction of logarithms drastically expanded their application. Usually made of brass, wood, or ivory, they look like a jointed rule with scales engraved on either side.
Sectors use the principle of similar triangles (that the ratio of lengths of two sides of similar triangles will always be the same) with scales of proportion for calculating mathematical functions such as finding the line of equal parts, inscribing a rectangular polygon inside a circle of a given radius and protracting angles. This made them useful for similar calculations to a slide rule.
18/10/2002
Created by: Saffron Clackson on 18/10/2002
FM:39865
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