Editing Metre Convention (section)

== Background ==
[[File:Systeme-Metrique.jpg|thumb|250px|Woodcut dated 1800 illustrating the new decimal units which became the legal norm across all France on 4 November 1800]]
Before the [[French Revolution]], which started in 1789, [[Units of measurement in France|French units of measurement]] were based on the [[Carolingian Renaissance|Carolingian]] system, introduced by the first [[Holy Roman Emperor]] [[Charlemagne]] (800–814 AD) which in turn were based on ancient Roman measures. Charlemagne brought a consistent system of measures across the entire empire. However, after his death, the empire fragmented and many rulers introduced their own variants of the units of measure.

Some of Charlemagne's units of measure, such as the {{lang|fr|pied du Roi}} (the king's [[Foot (unit)|foot]]) remained virtually unchanged for about a thousand years, while others, such as the {{lang|fr|aune}} ([[ell]] – used to measure cloth) and the {{lang|fr|livre}} ([[Pound (mass)|pound]]) varied dramatically from locality to locality. By the time of the revolution, the number of units of measure had grown to the extent that it was almost impossible to keep track of them.

In England in 1215, clause 35 of [[Magna Carta]] required that the same standards of measurement be applied throughout the realm. The wording of the clause emphasized that "There is to be a single measure ... throughout our realm".<ref>
{{cite web
 |url = https://www.archives.gov/exhibits/featured-documents/magna-carta/translation.html
 |title = Magna Carta
 |date = 6 October 2015
 |translator-first = Nicholas
 |translator-last = Vincent
 |access-date = 30 September 2012
 |archive-date = 15 November 2015
 |archive-url = https://web.archive.org/web/20151115024814/http://www.archives.gov/exhibits/featured-documents/magna-carta/translation.html
 |url-status = live
}}</ref> Five centuries later, when in 1707 [[Acts of Union 1707|England and Scotland were united]] into a single kingdom, the Scots agreed to use the same units of measure that were already established in England.<ref>[[s:Act of Union 1707|Act of Union 1707]], Article 3</ref> During the eighteenth century, in order to facilitate trade, [[Peter the Great]], Czar of Russia adopted the English system of measure.<ref>
{{cite book
 |first1 = Thomas
 |last1 = McGreevy
 |title = The Basis of Measurement: Volume 1 – Historical Aspects
 |page = 166
 |isbn = 0-948251-82-4
 |year = 1995
 |publisher = Pitcon Publishing (Chippenham) Ltd
}}</ref>

From 1668 to 1776 the French standard of length was the [[Toise]] of Châtelet which was fixed outside the [[Grand Châtelet]] in Paris. In 1735 two geodetic standards were calibrated against the Toise of Châtelet. One of them, the Toise of Peru was used for the [[French Geodesic Mission to the Equator]]. In 1766 the Toise of Peru became the official standard of length in France and was renamed Toise of the [[French Academy of Sciences|Academy]] ({{langx|fr|links=no|Toise de l'Académie}}).<ref>{{Cite web |title=What is the unit called a toise? |url=https://www.sizes.com/units/toise.htm |access-date=2025-04-10 |website=www.sizes.com}}</ref><ref>{{Cite web |title=Pied de roi - 1774 - La Toise de l'Académie des Sciences et le Mètre - Musée des arts et métiers - Paris - France |url=https://www.aly-abbara.com/utilitaires/convertisseur/Images/pied-roi-1774-France.html |access-date=2025-04-10 |website=www.aly-abbara.com}}</ref>

Profusion of units of measures was a practical problem of importance before the French Revolution and its reform was one of the items on the agenda of [[National Assembly (French Revolution)|National Assembly]].<ref name=":1">{{Cite news|url=https://www.entreprises.gouv.fr/metrologie/histoire-metre|title=Histoire du mètre|work=Direction Générale des Entreprises (DGE)|access-date=27 December 2017|archive-date=3 October 2015|archive-url=https://web.archive.org/web/20151003055350/http://www.entreprises.gouv.fr/metrologie/histoire-metre|url-status=live}}</ref> In 1799, after the remeasurement of the [[Paris meridian]] arc ({{langx|fr|links=no|Méridienne de France}}) between [[Dunkirk]] and [[Barcelona]] by [[Jean Baptiste Joseph Delambre|Delambre]] and [[Pierre Méchain|Mechain]], the metre was defined as a quarter of a 10-millionth of the Earth circumference or 3 {{lang|fr|[[pied]]s}} (French feet) and 11.296 {{lang|fr|[[ligne]]s}} (lines) of the Toise of the Academy.<ref name=":1" /> [[Charles Maurice de Talleyrand-Périgord|Talleyrand]], an influential leader of the Assembly invited British and American participation in the establishment of a new system, but in the event, the Assembly went it alone and introduced the metre and the [[kilogram]] which were to form the basis of the metric system, manufacturing prototypes which, in 1799, were lodged with Archives.<ref name="McGreevy1">
{{cite book |last1=McGreevy |first1=Thomas |title=The Basis of Measurement: Volume 1 – Historical Aspects |publisher=Pitcon Publishing (Chippenham) Ltd |year=1995 |isbn=0-948251-82-4 |pages=145, 151}}</ref>

Between 1840 and 1870, a number of countries definitively adopted the metric system as their system of measure including France, Spain, many South American republics and many of the Italian and German states (the Netherlands had adopted the system in 1817).<ref name=":1" />

In 1863, the [[International Postal Union]] used grams to express permitted weights of letters. In the 1860s, inspections of the prototype metre revealed wear and tear at the measuring faces of the bar and also that the bar was wont to flex slightly when in use.<ref name="McGreevy1" />