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Metric Set Square

Metric Set Square

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This 6-3/8" brass rule unfolds to form a set square. The outer edge of one leg has a centimeter scale numbered by ones from 1 to 16. It is marked: Nelle Mesure. The outer edge of the other leg has a scale for French inches (approximately 1-1/16") numbered by ones from 1 to 5. The first unit is divided into twelfths. The scale is marked: 6 Pouces. This leg has a pinhole for hanging a plumb bob and a rectangular hole with a rounded end (approximately 15/16" long) for viewing the plumb bob. The square has no maker's mark.
For a brief history of squares, see MA.316929. Typically, the legs were marked with scales for measuring lengths. What is unusual about this square is that it has both a traditional French measure and a unit from the newly introduced metric system, which is denoted as a "nouvelle mesure," or "new measure." The metric system was created in France in the 1790s, after the French Revolution of 1789. This suggests a date of about 1800 for the instrument.
Albert Haertlein (1895–1960), who collected this square, graduated with a bachelor's degree in civil engineering from the Massachusetts Institute of Technology in 1918. He served in the engineering corps of the U.S. Army during World War I and taught engineering at Harvard from 1919 until 1959. Haertlein was prominent in the American Society of Civil Engineers.
References: "News From the Classes," Technology Review 21 (1919): 645; Albert Haertlein, Papers, HUG4444, Harvard University Archives, Cambridge, Mass.
Entry 1985.0580.05.
Currently not on view
Object Name
set square
date made
ca 1800
place made
Physical Description
brass (overall material)
overall, folded: 16.2 cm x 2 cm x.4 cm; 6 3/8 in x 25/32 in x 5/32 in
ID Number
accession number
catalog number
Credit Line
Gift of Mrs. Albert Haertlein
Drawing Instruments
See more items in
Medicine and Science: Mathematics
Measuring & Mapping
Science & Mathematics
Squares and Triangles
Metric System
Data Source
National Museum of American History
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