*Units and Significant Figures 411
(our inch). It was not until around the early 1500s that man began to
consider quantifying and standardizing dimensions such as time and length.
The yard, for example, has its origin with Saxon kings, whose gird was the
circumference of the waist. It was King Edgar who, in an apparent attempt
to provide a standard of measurement, declared that the yard should be
the distance from the tip of his outstretched fingers to his nose. Other royal
declarations, such as one made by Queen Elizabeth I defining the statute
mile to be 5280 feet (8 furlongs at 220 yards per furlong) instead of the
Roman mile (the distance of 1000 Roman soldier paces or 5000 feet), served
to standardize what has become known as the English system of units.
The metric system, on the other hand, was not burdened with units of
anthropometric origin, as was the English system. The metric system did not
arise until near the end of the Period of Enlightenment, around the end of the
17th century. Thus, its development followed a more rational and scientific
approach. Prior to its introduction, practically no single unit of measure
was consistent. Footplates abounded, which marked the lengths of the most
common footmeasures in Europe. In Rhineland, a foot was 31 centimeters,
whereas in Gelderland it was 27 centimeters. The pound in Amsterdam
was 494 grams. Slightly farther south in the Hague, it was 469 grams. This
presented considerable confusion and impeded intercity commerce.
In 1670, a decimal system based on the length of one arc minute of the
great circle of the earth was proposed by Gabriel Mounton. Jean Picard, in
1671, proposed that the length standard be defined as the length of a clock’s
pendulum whose period was a specified time. It was not until 1790 when
a commission appointed by the French Academy of Sciences developed and
formalized a decimal-based system defining length, mass, and volume. The
unit of length, the meter, equaled one ten-millionth of the distance from
the north pole to the equator along the meridian of the earth running from
Dunkerque, France, through Paris to Barcelona, Spain. The unit of mass,
the gram, was defined in terms of a liquid volume, where one gram equaled
the mass of one cubic centimeter of water at its temperature of maximum
density. The unit of volume, the liter, equaled one cubic decimeter. This
approach established mass and volume as supplementary units in terms
of a base unit (the meter), which was to a physical standard (the earth’s
circumference).
In 1866, the United States Congress made it lawful to use the metric
system in the United States in contracts, dealings, and court proceedings.
Various metric units were defined in terms of their English counterparts.
For example, the meter was defined as exactly 39.37 inches. In 1875, the
United States signed in S`evres, France, along with 16 other countries, an
international treaty called the Metric Conversion. This treaty established a
permanent international bureau of standards and the standards for length
and mass. In 1893, the US customary units (those based on the English sys-
tem) were redefined in terms of their metric standards (which was opposite
the approach taken in 1866). The yard became exactly 0.9144 meters (hence,