The New Student's Reference Work/Metric System, The
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.