Standard metre

To put an end to the multiplicity of weights and measures units, France’s revolutionary government decided to create a universal system. On 26 March 1791 the Constituent Assembly adopted the proposal made by the Académie des Sciences, creating the metre, equal to one ten-millionth of the distance from the Earth’s equator to the North Pole. Two astronomers, Jean-Baptiste Delambre and Pierre Méchain, were charged with measuring this imaginary line representing a quarter of the Earth’s meridian. It took them six years, from 1792 to 1798, during which time the law of 1 August 1793 established the new decimal system. The metre was the unit of length and the cubic decimetre that of volume, initially called the pinte and then the cadil, it became the litre around 1800. These new weight and measurement units were finally linked: a litre of water occupies a cubic decimetre and weighs one kilogram. Standard metres and kilograms were made in 1799 [Year VII of the Revolutionary Calendar] and kept in the National Archives. In 1848 examples of the two units, also made in the Year VII, were transferred to the Conservatoire, where they still are today.