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TheBureau des Longitudes (French:[byʁodelɔ̃ʒityd]) is a French scientific institution, founded by decree of 25 June 1795 and charged with the improvement of nauticalnavigation,standardisation oftime-keeping,geodesy andastronomical observation. During the 19th century, it was responsible forsynchronizingclocks across the world. It was headed during this time byFrançois Arago andHenri Poincaré. The Bureau now functions as anacademy and still meets monthly to discuss topics related toastronomy.
The Bureau was founded by theNational Convention after it heard a report drawn up jointly by the Committee of Navy, the Committee of Finances and the Committee of State education.Henri Grégoire had brought to the attention of the National Convention France's failing maritime power and the naval mastery ofEngland, proposing that improvements in navigation would lay the foundations for a renaissance in naval strength. As a result, the Bureau was established with authority over theParis Observatory and all other astronomical establishments throughout France. The Bureau was charged with taking control of the seas away from theEnglish and improving accuracy when tracking thelongitudes of ships through astronomical observations and reliable clocks.
The ten original members of its founding board were:
By a decree of 30 January 1854, the Bureau's mission was extended to embrace geodesy, time standardisation and astronomical measurements. This decree granted independence to theParis Observatory, separating it from the Bureau, and focused the efforts of the Bureau ontime andastronomy. The Bureau was successful at setting a universal time in Paris via air pulses sent throughpneumatic tubes. It later worked to synchronize time across theFrench colonial empire by determining the length of time for a signal to make a round trip to and from a Frenchcolony.
The French Bureau of Longitude established a commission in the year 1897 to extend themetric system to the measurement oftime. They planned to abolish the antiquated division of the day intohours,minutes, andseconds, and replace it by a division into tenths, thousandths, and hundred-thousandths of aday. This was a revival of adream that was in the minds of the creators of the metric system at the time of theFrench Revolution a hundred years earlier. Some members of the Bureau of Longitude commission introduced acompromise proposal, retaining the old-fashioned hour as the basic unit of time and dividing it into hundredths and ten-thousandths.Poincaré served as secretary of the commission and took its work very seriously, writing several of its reports. He was a fervent believer in auniversal metric system. But he lost the battle. The rest of the world outside France gave no support to the commission's proposals, and the French government was not prepared to go it alone. After three years of hard work, the commission was dissolved in 1900.
Since 1970, the board has been constituted with 13 members, 3 nominated by theAcadémie des Sciences. Since 1998, practical work has been carried out by theInstitut de mécanique céleste et de calcul des éphémérides.
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