Metric Set Square

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: N^elle 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.

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