The Metre Convention is the treaty that set up the International Bureau of Weights and Measures (BIPM). The BIPM is an inter-governmental organization that is responsible for harmonizing systems of measurement across the world. The treaty was first made in 1875 between 17 countries.
The member countries agreed to share the costs of running a laboratory on neutral territory. The international prototype metre and the international prototype kilogram would be kept at the laboratory. Member state's national prototype metres and kilograms would be compared with the international prototypes at regular intervals. Member states would have regular meetings to discuss developments in measurement technology.
In 1921 the treaty was extended to cover electrical and all other physical measurements. This enabled the BIPM to published the standards for the International System of Units (SI). Under SI, units of measurements that are used in science and engineering were defined in a logical manner. The rules for SI also standardized the way in which physical quantities are written.
In 2014 the BIPM had 55 member countries.
Before the treaty
The metric system was developed in France in the 1790s. The length of the metre was made to be one ten millionth of the distance between the North Pole and the equator. Between 1791 and 1798 the French men Delambre (a mathematician and astronomer) and Méchain (an astronomer) measured the distance between Dunkirk and Barcelona. The measurements were used to make a metal bar exactly 443.296 lignes long (the ligne is an old French unit of length equal to one twelfth of a French inch). The bar would be used as a standard for the metre. The bar was later called the metre des archives. By the 1860s it was found that the metre des archives was 0.03% shorter than it was supposed to have been.
The Great Exhibition in London in 1851 and the Paris International Exhibition in 1867 had shown the need for different nations to use the same units of measurement. In the 1860s there were many discussions by astronomers and surveyors from outside France whether they should use the metre des archives or whether they should use a "new metre" that took account of the 0.03% error. Prussia took the lead in organizing conferences in Berlin to discuss the matter. France did not take part in the conferences. Before any actions could be taken the Franco-Prussian War broke out. Prussia defeated France and the German Empire was formed.
In 1875 France invited representatives to Paris to discuss the matter. This helped France to score a diplomatic victory over Prussia and the German Empire.
Treaty details
The treaty was signed by seventeen of the countries at the conference in Paris on 20 May 1875. The United Kingdom and the Netherlands went to the conference but did not sign the treaty at that time. After further consideration, the United Kingdom did sign the treaty in 1884.
The meeting agreed: Three organisations would be set up to administer the treaty. Identical copies of the metre and kilogram would be manufactured. One copy of each would be chosen as the international master copy. Other copies would be distributed to member states. The master copy of the metre and the kilogram would be kept in the laboratory. The laboratory would be on neutral territory. Members would compare their copies with the master copies at regular intervals. The organisations would promote the use of the metric system.
International Bureau of Weights and Measures (BIPM) The organization set up by the treaty was the International Bureau of Weights and Measures. Its French name is Bureau international des poids et mesures. Its abbreviation is BIPM. The BIPM has its headquarters at the Pavillon de Breteuil, Sèvres, France (close to Paris). About 70 people work at the BIPM. The budget for 2013 was over €10 million ($12 million).
The three organisations were set up under the treaty. They are: The International Bureau of Weights and Measures (BIPM). The General Conference on Weights and Measures (CGPM). The International Committee for Weights and Measures (CIPM).
The Bureau has responsibility for safeguarding the international prototype kilogram.
The official language for the organisations is French. Until 1988 all reports of meetings were only published in French. Since then both English and French have been used. Abbreviations are based on the French words, not English words. Official communications between the BIPM and France are conducted via the French Foreign Ministry. Official communications with other countries are conducted via that country's embassy in Paris.