Italian-Style Sector by Jacobus Lusuerg

The two arms on this brass hinged sector have decorative curves at one end. An acanthus scroll motif is on the hinge. Five double scales (i.e., the scales on one arm are identical to those on the other arm) are on one side. The scales are labeled on both legs. The outermost scale is labeled Metallorum and marked with the letters: Aur, Mer, Plu, Arg, Cup, Fer, Sta, Mar, Sax. These correspond to the specific weights of different metals. The second scale runs from 4 to 40 and is labeled Quadratrix Segmentorum. The third scale is marked with engravings of various polyhedra and the letters: D, I, C, S, O, T. It is labeled Solidorum Regularum. The fourth scale runs from 20 to 3. The letters D and R are on either side of the number 7. The scale is labeled Planorum AEqualium. The innermost scale runs from 10 to 180 and is labeled Graduum Circuli.
The reverse side has four double scales. The outermost runs from 20 to 3 and is labeled Figurarum Regularium. The second runs from 1 to 100 and is labeled Planorum. The third runs from 1 to 125 and is labeled Solidorum. The innermost scale runs from 20 to 300 and is labeled Partium AEqualium. One arm has a scaled diagram, labeled Orthographia Munimentorum, for dividing various heights, lengths, and depths of military fortifications into sections. The other arm has a table labeled Tabula Ignographia Munimentorum that gives the proportional dimensions for areas of fortifications that have between four and ten sides.
The outer edges of the arms have scales that run from 1/4 to 64. One is labeled Poids des boulets, and the other is labeled Calibre des pieces. Although most of the scales on this instrument reflect the Italian style of sector, these scales are typical of sectors made for the French market. See, for example, MA*321676 and MA*333929.
In the closed position, the front of the sector reads: Iacobus Lusuerg (/) Mutinensis Faciebat (/) Roma Ao. 1683. Jacob Lusuerg and his son, Dominicus, made mathematical instruments in Rome and Modena from 1674 until 1719. Henry Russell Wray, the previous owner of this instrument, graduated from the University of Pennsylvania and was a businessman in Colorado Springs, Colo., in the early 20th century.
References: Jim Bennett and Stephen Johnston, The Geometry of War, 1500–1750 (Oxford: Museum of the History of Science, 1996); Maya Hambly, Drawing Instruments, 1580–1980 (London: Sotheby's Publications, 1988), 25.
Currently not on view
Currently not on view
Object Name
date made
Lusuerg, Jacobus
Physical Description
brass (overall material)
overall: .5 cm x 21.3 cm x 4.3 cm; 3/16 in x 8 3/8 in x 1 11/16 in
place made
Italia: Lazio, Roma
ID Number
accession number
catalog number
Rule, Calculating
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Data Source
National Museum of American History, Kenneth E. Behring Center


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