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

530 APPENDIX B
republican regime, as witnessed by the failure of the State to construct and distribute
the necessary secondary standards. The new standards were especially threatened by
a decree of Napoleon in 1812 that, yielding to prejudice, permitted for a decade a system
of mesures usuelles using odd multiples and fractions of the metric system to harmonize
with the very measures the metric system was intended to replace, those long established
in commerce and common usage. In 1837 the State repealed the edict and allowed 3
years for full compliance with the new measures. After January 1, 1840, under pain
of severe penalties for the use of any other weights and measures, the metric system
was made universal and compulsory throughout France.
The instability of 19th-century Europe, with its profusion of petty kingdoms and
principalities and its wars and revolutions acted to retard acceptance of the metric
system. Upon Tralles' return from Paris he urged introduction of metric weights and
measures into Switzerland and in 1801 saw a law passed adopting them. But the metric
system was not made compulsory in that country until 1856.
Some of the Italian provinces adopted it in the early 19th century, in 1816 the
metric system was declared obligatory in the Low Countries, and Spain accepted it in
1849. After 1860 adoptions increased rapidly, the entering wedge in most instances
the necessity of uniform weights and measures in international trade.
The metric system crossed the Atlantic when by law it came into effect in
Mexico in 1862, and before the end of the century it had become the legal system in
most South and Central American countries. Italy made the metric system obligatory
in 1863. In Great BritEln, an act of July 29, 1864, authorized the use of the metric
system concurrently with the imperial system. Two years later, with passage of the
Metric Act on July 28, 1866, Congress also made use of the metric system legal through.
out the United States.° By this act, the meter was declared to be 39.37 inches, the
kilogram 2.2046 pounds, based on the best metric standards available in this country,
Hassler's Committee Meter and the platinum Arago kilogram obtained in 1821 by Secre-
tary of State Gallatin.
The agreement among the federated states of Germany in 1868 to adopt the metric
system became obligatory under the empire in 1872, the same year it was officially
adopted in Portugal. Austria made its use compulsory in 1876, and Norway in 1882.
THE METRIC CONVENTION
It was not commercial application of the metric system but its growing use in
scientific work in Europe that made the accuracy of its fundamental units of increas-
ing concern, especially to mathematicians, geodecists, and physicists. The more accurate
measurements of arcs of meridians reported by British and Russian geodecists at the
International Geodetic Conference held at Berlin in 1867 resulted in new computations
of the shape of the earth and hence the length of the quadrant. The changes in this
last quantity therefore affected the length of the meter and raised serious questions
about it as a natural and absolute standard.1°
0 An act of Congress on July 27, 1866, authorizing the Secretary of the Treasury to
furnish the States with sets of metric weights and measures, actually preceded passage
of the Metric Act by 1 day. Hallock and Wade, pp. 128—129.
10 Hallock and Wade, p. 69. The actual difference in the Meter of the Archives, as in
the International Meter that replaced it, is minute but significant in metrology. It is
about 0.2 millimeter shorter than its definition, the ten-millionth part of the quadrant
of the earth's meridian. Similarly, the International Kilogram exceeds by 0.028 gram