French units of measurement

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200px, Table of the measuring units used in the 17th century at Pernes-les-Fontaines_in_the_covered_market_at_Provence-Alpes-Côte_d'Azur_Regions_of_France.html" "title="Provence-Alpes-Côte_d'Azur.html" ;"title="Pernes-les-Fontaines in the covered market at Provence-Alpes-Côte d'Azur">Pernes-les-Fontaines in the covered market at Provence-Alpes-Côte d'Azur Regions of France">region In geography, regions, otherwise referred to as zones, lands or territories, are areas that are broadly divided by physical characteristics ( physical geography), human impact characteristics ( human geography), and the interaction of humanity an ...

of southeastern France France has a unique history of Unit of measurement, units of measurement due to its radical decision to invent and adopt the metric system after the French Revolution. In the Ancien régime and until 1795, France used a system of measures that had many of the characteristics of the modern

Imperial System The imperial system of units, imperial system or imperial units (also known as British Imperial or Exchequer Standards of 1826) is the system of units first defined in the British Weights and Measures Act 1824 and continued to be developed th ...

of units but with no unified system. There was widespread abuse of the king's standards, to the extent that the ''lieue'' could vary from 3.268 km in Beauce to 5.849 km in Provence. During the revolutionary era and motivated in part by the inhomegeneity of the old system, France switched to the first version of the metric system. This system was not well received by the public, and between 1812 and 1837, the country used the '' mesures usuelles'' – traditional names were restored, but the corresponding quantities were based on metric units: for example, the ''livre'' (pound) became exactly 500 g. After 1837, the metric system was reintroduced and progressively became the only system of use, with other units now in only residual use.

Ancien régime (to 1795)

In the pre-revolutionary era (before 1795), France used a system of measures that had many of the characteristics of the modern

of units, but there was no unified system of measurement. Charlemagne and successive kings had tried but failed to impose a unified system of measurement in France. (In England, by contrast, the Magna Carta decreed that "there shall be one unit of measure throughout the realm.") The names and relationships of many units of measure were adopted from Roman units of measure and many more were added – it has been estimated that there were seven or eight hundred different names for the various units of measure. In addition, the quantity associated with each unit of measure differed from town to town and even from trade to trade to such an extent that the ''lieue'' ( league) could vary from 3.268 km in Beauce to 5.849 km in Provence. It has been estimated that, on the eve of the Revolution, a quarter of a million different units of measure were in use in France. Although certain standards, such as the ''pied du roi'' (the king's foot) had a degree of pre-eminence and were used by

savants Savant syndrome () is a rare condition in which someone with significant mental disabilities demonstrates certain abilities far in excess of average. The skills that savants excel at are generally related to memory. This may include rapid calcu ...

across Europe, many traders chose to use their own measuring devices, giving scope for fraud and hindering commerce and industry. As an example, the weights and measures used at Pernes-les-Fontaines in southeastern France differ from those catalogued later in this article as having been used in Paris. In many cases, the names are different, while the ''livre'' is shown as being 403 g, as opposed to 489 g – the value of the ''livre du roi''. (The Imperial pound is about 453.6 g.)

Revolutionary France (1795–1812)

150px, left, A clock of the republican era showing both decimal and standard time. The

French Revolution The French Revolution ( ) was a period of radical political and societal change in France that began with the Estates General of 1789 and ended with the formation of the French Consulate in coup of 18 Brumaire, November 1799. Many of its ...

and subsequent

Napoleonic Wars The Napoleonic Wars (1803–1815) were a series of major global conflicts pitting the French Empire and its allies, led by Napoleon I, against a fluctuating array of European states formed into various coalitions. It produced a period of Fren ...

marked the end of the

Age of Enlightenment The Age of Enlightenment or the Enlightenment; german: Aufklärung, "Enlightenment"; it, L'Illuminismo, "Enlightenment"; pl, Oświecenie, "Enlightenment"; pt, Iluminismo, "Enlightenment"; es, La Ilustración, "Enlightenment" was an intel ...

. The forces of change that had been brewing manifest themselves across all of France, including the way in which units of measure should be defined. The savants of the day favoured the use of a system of units that were inter-related and which used a decimal basis. There was also a wish that the units of measure should be for all people and for all time and therefore not dependent on an artefact owned by any one particular nation. Talleyrand, at the prompting of the savant Condorcet, approached the British and the Americans in the early 1790s with proposals of a joint effort to define the metre. In the end, these approaches came to nothing and France decided to "go it alone". Decimal time was introduced in the decree of 5 October 1793 under which the day was divided into 10 "decimal hours", the "hour" into 100 " decimal minutes" and the "decimal minute" into 100 "decimal seconds". The "decimal hour" corresponded to 2 hr 24 min, the "decimal minute" to 1.44 min and the "decimal second" to 0.864 s. The implementation of decimal time proved an immense task and under the article 22 of the law of 18 Germinal, Year III (7 April 1795), the use of decimal time was no longer mandatory. On 1 January 1806, France reverted to the traditional timekeeping. 200px, The Paris meridian, which passes through the Observatoire de Paris. The metre was defined along this meridian using a survey that stretched from Dunkirk to Barcelona. The metric system of measure was first given a legal basis in 1795 by the

ary government. Article 5 of the law of 18 Germinal, Year III (7 April 1795) defined five units of measure. The units and their preliminary values were: *The

metre The metre (British spelling) or meter (American spelling; see spelling differences) (from the French unit , from the Greek noun , "measure"), symbol m, is the primary unit of length in the International System of Units (SI), though its prefi ...

, for length – defined as being one ten millionth of the distance between the North Pole and the Equator through

Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 105 km² (41 sq mi), ma ...

*The are (100 m²) for area f land*The stère (1 m³) for volume of firewood *The

litre The litre (international spelling) or liter (American English spelling) (SI symbols L and l, other symbol used: ℓ) is a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metre (m3 ...

(1 dm³) for volumes of liquid *The

gram The gram (originally gramme; SI unit symbol g) is a unit of mass in the International System of Units (SI) equal to one one thousandth of a kilogram. Originally defined as of 1795 as "the absolute weight of a volume of pure water equal to th ...

, for mass – defined as being the mass of one cubic centimetre of water Decimal multiples and submultiples of these units would be defined by Greek prefixes - "myria", "kilo", "hecta" (100), "deka" - and Latin prefixes - "deci", "centi" and "milli". Using Cassini's survey of 1744, a provisional value of 443.44 ''lignes'' was assigned to the metre which, in turn, defined the other units of measure. The final value of the metre had to wait until 1799, when Delambre and Mechain presented the results of their survey between Dunkirk and Barcelona that fixed the length of the metre at 443.296 ''lignes''. The law 19 Frimaire An VIII (10 December 1799) defined the metre in terms of this value and the kilogram as being 18,827.15 ''grains''. These definitions enabled the construction of reference copies of the kilogram and metre, which were to be used as standards for the next 90 years. At the same time, a new decimal-based system for angular measurement was implemented. The right angle was divided into 100 ''grads'', which in turn was divided in 100 ''centigrads''. An arc on the earth’s surface formed by an angle of one ''centigrad'' was one kilometre.

''Mesures usuelles'' (1812–1839)

150px, left, The ''Mesures usuelles'' were introduced by Napoleon I in 1812 The metric system was introduced into France in 1795 on a district by district basis, starting with Paris. However, the introduction was by modern standards poorly managed. Although thousands of pamphlets were distributed, the Agency of Weights and Measures, which oversaw the introduction, underestimated the work involved. Paris alone needed 500,000 metre sticks, yet one month after the metre became the sole legal unit of measure, there were only 25,000 in store. This, combined with other excesses of the Revolution made the metric system unpopular. Napoleon ridiculed the metric system, but as an able administrator, he recognised the value of a sound basis for a uniform system of measurement. Under the ''décret impérial du 12 février 1812'' (imperial decree of 12 February 1812), he introduced a revised system of measure – the ''mesures uselles'' or "customary measures" for use in small retail businesses. 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. The names of many pre-metric units were reintroduced, but were redefined in terms of metric units. Thus the ''toise'' (fathom) was defined as being two metres with six ''pied'' (feet) making up one ''toise'', twelve ''pouce'' (inches) making up one ''pied'' and twelve ''lignes'' making up one ''pouce''. Likewise, the ''livre'' (pound) was defined as being 500 g, each ''livre'' comprising sixteen ''once'' and each ''once'' eight ''gros'' and the ''aune'' as 120 centimetres.

The metric system restored (1840–1875)

''La loi du 4 juillet 1837'' (the law of 4 July 1837) of the July Monarchy effectively revoked the use of ''mesures usuelles'' by reaffirming the laws of measurement of 1795 and 1799 to be used from 1 May 1840. However, many units of measure, such as the ''livre'', remained in colloquial use for many years and the ''livre'' still does to some extent. When this legislation was introduced, the metric system was beginning to take hold across Europe. Switzerland and the German state of Baden had both defined their ''Fuß'' (foot) as being 300 mm and the German state of Hessen-Darmstadt has defined its ''Fuß'' as being 250 mm. Moreover, the

Netherlands ) , anthem = ( en, "William of Nassau") , image_map = , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of the Netherlands , established_title = Before independence , established_date = Spanish Netherl ...

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, Lombardy and

Venice Venice ( ; it, Venezia ; vec, Venesia or ) is a city in northeastern Italy and the capital of the Veneto region. It is built on a group of 118 small islands that are separated by canals and linked by over 400 bridges. The isla ...

had all adopted the metric system, albeit with local names for the "metre", "kilogram" and so on. The metric system was given a boost when the German ''

Zollverein The (), or German Customs Union, was a coalition of German states formed to manage tariffs and economic policies within their territories. Organized by the 1833 treaties, it formally started on 1 January 1834. However, its foundations had b ...

'' (Customs Union) introduced the '' Zollpfund'' of 500 g in 1850. The Great Exhibition of 1851 in

London London is the capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary dow ...

was followed by international exhibitions in Paris in

1855 Events January–March * January 1 – Ottawa, Ontario, is incorporated as a city. * January 5 – Ramón Castilla begins his third term as President of Peru. * January 23 ** The first bridge over the Mississippi River open ...

and

1867 Events January–March * January 1 – The Covington–Cincinnati Suspension Bridge opens between Cincinnati, Ohio, and Covington, Kentucky, in the United States, becoming the longest single-span bridge in the world. It was renamed a ...

. The 1867 exhibition had a stand showing how the diverse units of measure were converging onto the metric system – a system that had been developed in France and whose standards were in the custody of the French government, but available for world use. In 1870, while France was preparing to host an international conference to discuss international cooperation in the sphere of units of measurement, the

war War is an intense armed conflict between states, governments, societies, or paramilitary groups such as mercenaries, insurgents, and militias. It is generally characterized by extreme violence, destruction, and mortality, using regular o ...

broke out. France was humiliated by Prussia's military action, but in 1872 France seized the diplomatic initiative and re-issued the invitations for the 1870 conference. The conference met in 1875 and concluded with the signing of the Treaty of the Metre. The principal agreements under the treaty were: * A three-tier organisation would be put into place to provide political ( CGPM), scientific (

CIPM The General Conference on Weights and Measures (GCWM; french: Conférence générale des poids et mesures, CGPM) is the supreme authority of the International Bureau of Weights and Measures (BIPM), the intergovernmental organization established i ...

) and secretarial ( BIPM) support for coordinating calibrations of national standards against an international standard. * One of the eighteen seats on the CIPM would always be filled by a Frenchman. * France would provide premises for the secretariat. These premises, at the

Pavillon de Breteuil The Pavillon de Breteuil is the headquarters of the International Bureau of Weights and Measures (BIPM). The building lies in the southeastern section of the Parc de Saint-Cloud in Saint-Cloud, France, to the west of Paris. It is listed in France ...

, near

would have a diplomatic status. * New prototypes of the kilogram and metre would be manufactured. These were ultimately made in England and delivered in 1889. Thus the French metre and kilogram passed into international control.

International era (1875 onwards)

During the early part of the twentieth century, the French introduced their own units of

power Power most often refers to: * Power (physics), meaning "rate of doing work" ** Engine power, the power put out by an engine ** Electric power * Power (social and political), the ability to influence people or events ** Abusive power Power may a ...

– the , which was defined as being the power required to raise a mass of 100 kg against standard gravity with a velocity of 1 m/s giving a value of 980.665 W. However, many other European countries defined their units of power (the in Germany, the in the Netherlands and the in Italy) using 75 kg rather than 100 kg, which gave a value of 735.49875 W (about 0.985 HP). Eventually, the was replaced with the , which was identical to equivalent units of measure in neighbouring countries. In 1977, these units, along with the and the (and amongst others, the German ) were proscribed by EEC Directive 71/354/EEC which required EU member states to standardise on the International System of Units (SI) and therefore to use the watt and its multiples.

References

{{systems of measurement Systems of units Science and technology in France

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan area ...