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The first recorded proposal for what is now known as the metric system was by John Wilkins, a Fellow of the Royal Society, in 1668. The metric system was further developed during the French Revolution to replace the various measures previously used in France. The metre (also spelled "meter" in some dialects of English) is the unit of length in the metric system and was originally based on the dimensions of the earth, as far as it could be measured at the time. The litre (also spelled "liter"), is the unit of volume and was defined as one thousandth of a cubic metre. The metric unit of mass is the kilogram and it was defined as the mass of one litre of water. The metric system was, in the words of French philosopher Marquis de Condorcet, "for all people for all time".〔 The metric system has names to cover different ranges of the same measure. Instead of using names based on the context of the measure, the metric system mainly uses names made by adding prefixes, such as ''kilo-'' or ''milli-'', as decimal multipliers to the base unit names. Thus, one kilogram is 1000 grams and one kilometre is 1000 metres. During the nineteenth century the metric system was adopted by both the world-wide scientific community and many countries as the system of measurement. It therefore became truly international. Until 1875 the French government owned the prototype metre and kilogram, but in that year the Convention of the metre was signed and control of the standards relating to mass and length passed on to a trio of inter-government organisations. In 1960 the metric system was extensively revised to form the International System of Units, abbreviated to SI. ==Origins== On the eve of the French Revolution, France had an estimated quarter of a million different units of measurement. In many cases the value of a unit differed from town to town and even from trade to trade even though they might have the same name. While certain standards, such as the ''pied du roi'' (the King's foot) had a degree of pre-eminence and were used by savants (scientists), many traders used their own measuring devices. This gave scope for fraud and hindered commerce and industry.〔 The metric system was designed to replace this confusion with a radical new system with fixed values. In England, Magna Carta in 1215 decreed that "there shall be one unit of measure throughout the realm",〔(【引用サイトリンク】 Magna Charta translation )〕 However, France 〔(【引用サイトリンク】History of measurement )〕 and the rest of Europe had a multitude of measurement units. The differences were like those between United States customary units and United Kingdom imperial units — that measure liquids - a US pint consists of 16 US fluid ounces while an imperial pint is 20 UK fluid ounces and the US fluid ounce is about 4% larger than the UK fluid ounce. Differences such as these were multiplied almost infinitely across Europe. Between 1795 and 1800, during the French Revolution, and with the backing of Louis XVI, the system of weights and measures was totally reformed. The new system of measures had a rational mathematical basis and was part of the radical effort to sweep away old traditions and conventions and replace them with something new and better.〔 The French philosopher, the Marquis de Condorcet, who was one of those entrusted by Louis XVI to overhaul the system of measurement, characterised the metric system as "for all people for all time". The key units of the ''republican measures'' system were: *The ''mètre'' - the unit of length, defined as one ten-millionth of the distance between the north pole and the equator on the meridian passing through Paris〔(【引用サイトリンク】title=Historical context of the SI )〕 *The ''are'' - for land area, defined as the area of a square with sides of length 10 metres *The ''stère - for volume (particularly of stacked firewood), defined as 1 cubic metre *The ''litre'' - for dry and liquid volume, defined as the volume of a cube with sides of one-tenth of a metre *The ''gramme'' - for weight, defined as the weight of a cube of pure water with sides of one-hundredth of a metre and at the temperature of melting ice. Since it was not practical to realise the metre and kilogram, reference kilogram and metre artifacts, the ''metre des Archives'' and ''kilogramme des Archives'' were manufactured to meet these definitions as closely as possible. The modern metre is a refinement of the original artifact, but the kilogram is still waiting to be redefined. The new system was not popular and people continued to use their customary measures. Napoleon recognised the value of a sound basis for a system of measurement but ridiculed the metric system. In 1812 he introduced the ''mesures usuelles,'' a modification of the metric measures for use in small retail businesses. These ''mesures usuelles'' used some older unit names but used the ''metre des Archives'' and the ''kilogramme des Archives'' as its basis for measurement. However, all government, legal and similar works still had to use the metric system and the metric system continued to be taught at all levels of education. This system survived in France until the metric system was reinstated for all purposes in 1840. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Introduction to the metric system」の詳細全文を読む スポンサード リンク
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