**Met′ric System, The,** is an international system of measurement of lengths, surfaces, weights and volumes which was gradually
developed as the need for a universal system
became more and more imperative.
Abbé Gabriel Mouton in 1670 proposed an
aliquot part of the circumference of the earth
as an international unit of length. Other
authorities, including Picard, La Condamine,
Jefferson and Talleyrand, favored the length
of a pendulum beating seconds. A committee
of the French Academy of Sciences, which
was appointed in 1790 and included Laplace,
Condorcet, Borda, Lagrange and Monge,
reported in favor of the tenth-millionth part of
a quarter of a terrestrial meridian or the
distance from the equator to the North Pole
as the standard unit of length. The success
of the decimal money-system of the United
States appears to have won many advocates
for the metric system of weights and
measures. The unit recommended by the
committee of 1790 was established by decree;
and the nomenclature was legally fixed by a
law of 1795; but the metric system had still
to secure adherents among the masses and
abroad. This was effected by the adoption
of the report of an international commission
in 1799. Standard units were deposited in
the Paris archives; and by 1837 the use of
the metric system was made compulsory in
France in all departments. In 1866 the
metric system was recognized by law in the
United States. Several attempts have been
made to render it obligatory; but it has
seemed preferable to allow the system to
win its way for a time, as it is doing, on its
own merits.

The unit of length is a *metre;* the unit of
weight a *gram;* the unit of capacity a *litre.*
The equivalent of a metre is 39.37079 inches;
of a gram, 15.43235 grains; of a litre 61.02705
cubic inches. A gram has the weight of one
cubic centimetre; a litre the volume of one
cubic decimetre. Prefixes are used to indicate
submultiples and multiples of the units,
thus:

Milli | — one thousandth part. |

Centi | — one hundredth part. |

Deci | — one tenth part. |

Deca | — ten times. |

Hecto | — one hundred times. |

Kilo | — one thousand times. |

So a centimetre is the hundredth of a metre, a decimetre the tenth of a metre, a kilogram one thousand grams, and so on. The labor of the calculations and reductions in terms of weights and measures is reduced to a minimum by the simple relation between the units of mass and dimension and by the use of decimal parts and decimal notation. Metres and kilograms constructed of an alloy of iridium and platinum are furnished to countries which need them from the Observatory of the International Bureau, established at St. Cloud in 1878.