ENORMOUS METER-LONG MATHEMATICAL SECTOR — the struggle to adopt the metric system
Stock Number: 9366
For sale, antique enormous mathematical sector to bridge the transition in France to the metric system which was introduced between 1795 and 1800. It was poorly understood by the general population so Napoleon designed a system which was used between 1812 and 1839 when it was abolished.
39-7/16 inches (100 cm) open
Country of manufacture
ENORMOUS METER-LONG MATHEMATICAL SECTOR, French, c. 1820, signed “Compas (Viret)”, and “No. 9.” This major instrument measures 4-1/8″ x 20-3/4″ x 5/32″ (10 x 53 x 0.4 cm) closed, and opens to a full 39-7/16″ (100 cm). It has a three-leaf sector hinge, and closes on the central steel alignment leaf and the three alignment pins. One side is divided with a linear scale from 0 to 12 by twelfths, labeled “Pied Ancien” representing the 18th century standardized “Pied de Roy” (27.1 mm / inch), plus a double sector scale of equal parts divided from 0 to 57 by ones. The reverse has (1) a similar but unlabeled “Foot” scale of 12 inches by twelfths of an inch (at about 26.8 mm / inch), (2) a linear “Pied Métrique” scale also running from 0 to 12 by twelfths (and curiously at 27.9 mm / inch), and (3) a double sector scale of equal parts divided from 0 to 220 by ones. Condition is fine, noting numerous small nicks and scratches. This remarkable rule is housed in its softwood case with slide off lid.
The “Pied Métrique” scale on this sector represents a fascinating period in the transition to the metric system in France. An inch of 27.9 mm gives a foot of approximately 335 mm (actually intended to be 333-1/3 mm), and thus a meter of exactly 3 feet. This was part of the “mesures usuelles” introduced by Napoleon in 1812, and finally abolished in 1839. The formal metric system had been gradually introduced into France, département by département (Paris being first), between 1795 and 1800. It was poorly understood by the populace, unpopular, and little used in local trade. As a compromise, Napoleon introduced this sort of “metric” system based on the old measures. A meter thus equaled one yard of three traditional feet, the liter was subdivided as a quart, the kilogram was specified as exactly two pounds, etc. It was a confusing journey into the eventual acceptance of the greatly simplified true metric system. The engraved word “Viret” in parentheses is something of a puzzle, but probably indicates the maker of this grand sector. A clockmaker by this name is indeed listed in Paris directories during the 1820’s, and a splendid gilt clock by him is known.
Ask the Dealer
David and Yola Coffeen both have enjoyed academic careers, as planetary astronomer and as linguist/educator. But since 1982 (yes, 1982!) they have been full-time dealers in early scientific and medical instruments, under the name Tesseract. Selling primarily by catalogue (over 100 issued so far) they also have a web presence at www.etesseract.com, and can be contacted at email@example.com.