made in Rome

Sector

A sector is an instrument for solving computations which use the rules of proportion. This brass example was made in 1691, probably by Dominicus Lusuerg, a scientific instrument maker based in Rome.

This side has a range of scales for different calculations, including a pair of lines marked 'Figurarum Regularium' for setting out regular polygons with between 3 and 20 sides. There are two further features for the military surveyor: one, 'Tabula Igonographical Munimentorum', gives the Proportional dimensions of features of fortifications between 4 and 10 sides; the other, 'Orthographia Munimentorum', is a scaled section, giving lengths, heights and depths according to a horizontal scale.

The invention of the sector is attributed to Thomas Hood by the English, and to Galileo Galilei by the Italians. Both published quite independent accounts in 1598. However, the instrument had its origins in the earlier proportional compass.

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Online ID:	000-190-002-070-C
Image Rights Holder:	National Museums Scotland
Project:	0098: National Museums Scotland Project description \| View all records in project
Ref:	National Museums Scotland T.1985.75
Date:	1691
Material:
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Subject:
Who:	Dominicus Lusuerg (Possibly the maker)
Where:	Rowe
Event:
Description:	Sector by Dominicus Lusuerg of Rowe, 1691
References:	A similar sector made by Nicolaus Blondo of Naples in 1694 is described in Bennett, J & Johnston, Stephen, The Geometry of War 1500-1750. Oxford: 1996, p 72 For instruments by Lusuerg, see Hambly, Maya. Drawing Instruments 1580-1980. London: 1988, p 25, and Wynter, Harriet & Turner, Anthony. Scientific Instruments. London: 1975 p 68
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