Measures for Progress: A History of the National Bureau of Standards

THE FRENCH ORIGIN OF THE METRIC SYSTEM
APPENDIX B
ThE METRIC SYSTEM
IN THE UNITED STATES
The genesis of the modern metric system was a decimal system, based on the length
of an arc of 1 minute of a great circle of the earth, first proposed by Gabriel Mouton, a
vicar of Lyons, France, in the late 17th century. The proposal confronted a plethora
of arbitrary systems of weights and measures current in France, as in the rest of
Europe, their lineage going back to medieval measures based on the size of barley
corns and the length of human feet. Mouton's plan was discussed for almost a hundred
years before the progress of commerce and science called for more rational measures
than the weights and measures in common use.
The beginning of order took place in 1790 when Tallyrand proposed to the French
National Assembly the desirability of a system of weights and measures that would
not only bring uniformity to France but would also be international in application.
It must, therefore, he reasoned, be based on some invariable unit of nature that couli'
not only be readily reproduced but would be capable of being measured with a high degree
of precision.
A decree of the National Assembly on May 8, 1790, sanctioned by Louis XVI
on August 22, called upon the Academy of Sciences, in concert with the Royal Society
of London, "to deduce an invariable standard for all the measures and all the weights." 1
When English interest in a French undertaking could not be obtained, a committee of
philosophers of the Academy, composed of Borda, Lagrange, Laplace, Monge, and Con.
dorcet, began deliberations, reporting its conclusions in March 1791. The choice of a
fundamental unit as the basis of a rational system of measures was between the length
or fraction of the length of a pendulum, vibrating in intervals of 1 second or some
chosen unit of time; the quadrant of a great circle of the equator; and the quadrant of
a great circle of the earth's meridian. Since the pendulum introduced a new and
unlike element, the second, and depended on the varying intensity of the gravitational
force on the earth's surface, the committee preferred a terrestrial arc.
1 William Hallock and Herbert T. Wade, The Evolution of Weights and Measures and
the Metric System (New York: Macmillan, 1906), p. 47. Hallock and Wade and
the article by Henrie Moreau, "The Genesis of the Metric System and the Work of
the International Bureau of Weights ana Measures," J. Chem. Educ. 30, 3 (1953), pro.
vide the basis for this account of the metric system. Other sources that have been
consulted but not cited here include NBS S17, "History of the standard weights and
measures of the United States" (Fischer, 1905), reprinted as M64 (1925) ; M122,
"Weights and measures in Congress" (S. A. Jones, 1936) ; C570, "Units and systems
of weights and measures" (Judson, 1956) ; C593, "The Federal basis for weights and
measures" (R. W. Smith, 1958) ; TNB 43, 1—3 (1959) ; and M247, "Weights and
measures of the United States" (Judson, 1963). The most complete history of the
metric system is that of Guillaume Bigourdan, Le Système Métrique des Poids et Mesures
(Paris, 1901).
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