Accession No
4607
Brief Description
sector by John Newman, 1812 - 1856
Origin
122 Regent Street; London
Maker
Newman. John
Class
calculating; mathematics
Earliest Date
1812
Latest Date
1856
Inscription Date
Material
ivory; metal (brass)
Dimensions
length 159mm; breadth 33mm; thickness 3mm
Special Collection
Provenance
Purchased on 05/12/1991.
Inscription
‘I . Newman
122 Regent Street London’ (obverse)
Description Notes
Ivory sector with brass hinge and brass pins for holding limbs together.
Obverse:
Double line of lines marked ‘L’ divided [0] - 10 numbered by 1 subdivided to 0.1
Double line of secants marked ‘S’ divided [10] - 75 numbered by 10; 10 - 30 subdivided to 5, 30 -50 subdivided to 2, 50 - 75 subdivided to 1.
Double line of chords, marked ‘C’ divided [0] - 60 numbered by 10 subdivided to 30’.
Double line of polygons, marked ‘POL’ divided 12 - 4 numbered by 1
On the fully opened limbs a scale of inches divided [0] - 12 numbered by 1 (except 6) subdivided to 0.1
Reverse:
Double scale of sines marked ‘S’ divided [0] - 90 numbered by 10; 0 - 40 subdivided to 30’, 40 - 70 subdivided to 1, 70 - 80 subdivided to 2, 80 - 90 subdivided to 5
Double line of tangents, marked ‘T’ divided [0] - 45 and continued on second line to 75, numbered by 10; 0 - 30 subdivided to 30’, remainder to 15’
On fully opened limbs:
Log scale of tangents, marked ‘T’ divided [1˚10’] - 45 numbered 2, 3...10, 20, 30, 40, 45; 1˚10’ - 10˚ subdivided to 10’, 10 - 20 subdivided to 30’, 20 - 45 subdivided to 1˚.
Log scale of sines, marked ‘S’ divided [40’] - [90] numbered 1, 2...10, 20 ... 70; 40’ - 10˚ subdivided to 10’, 10 - 20 subdivided to 30’, 20 - 30 subdivided to 1˚, 30 - 70 subdivided to 2˚, 70 - 90 subdivided to 10˚
Log scale of numbers, marked ‘N’ divided 1 - 10[0] numbered 1, 2 ... 1[0], 2[0] ... 10[0]; 1 - 4 subdivided to 0.1, 4 - 10 subdivided to 0.2, 10 - 20 subdivided to 0.5, 20 - 50 subdivided to 1, 50 - 100 subdivided to 2.
On edge of fully opened limbs a decimal foot divided [0] - 100 numbered by 10 (except 50) subdivided to 1.
Condition good; complete
References
Events
Description
Sector
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:40353
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