Accession No
1174
Brief Description
sector, brass, by Pierre Le Maire, French, 1750 (c)
Origin
France; Paris
Maker
Le Maire, Pierre
Class
calculating; mathematics
Earliest Date
1735
Latest Date
1785
Inscription Date
Material
metal (brass)
Dimensions
length 115mm; breadth 25mm; thickness 3mm
Special Collection
Provenance
Transferred from the Museum of Archaeology and Ethnography, University of Cambridge (now Museum of Archaeology and Anthropology) in 09/1953.
Inscription
‘P. le Maire
AParis’ (obverse)
Description Notes
Sector, brass, by Pierre Le Maire, French, c. 1750.
4-inch brass sector with decorated hinged and internal scroll piece.
On the obverse double scales of: ‘les Cordes’ divided [0] - 90˚, numbered by 10˚, 5˚ - 90˚ subdivided to 1˚; ‘les Solides’ divided 1 - [64], numbered 1, 5, 10, 20...60, subdivided to 1; ‘les Metaux’ marked by symbol. On fully opened limbs unequal scale of ‘Poids et diametre des Boulets’, divided [1/4] - 16, numbered 1/2, 1, 2, 3, 4, 5, 6, 8, 10, 12, 16.
On the reverse double scales of: ‘les Parties Egales’, divided [0] - 100, numbered by 10, 5 - 100 subdivided to 1; ‘les Plans’, divided 1 - [64], numbered 1, 5, 10, 20...60, subdivided to 1; ‘les Poligones’ divided 12 - 3, numbered by 1. On the fully opened limbs unequal scale of ‘Calibre des Pieces’, divided [1/4] - 16, numbered 1, 2, 3, 4, 5, 6, 8, 10, 12, 16.
Two brass pins to hold limbs together.
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:39547
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