Definition:Metre/Historical Note

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Historical Note on Metre

It differs from the modern metre by half a centimetre.

It was soon established that as Acceleration Due to Gravity varies considerably according to location, this was not a sustainable definition to maintain a standard.

  • 26 March 1791: this proposal was adopted.
  • 1805: Ferdinand Rudolph Hassler brought a standard metre made in Paris to the United States. He designed a baseline apparatus which instead of bringing different bars in actual contact during measurements, used only one bar calibrated on the metre and optical contact. Thus the metre became the unit of length for geodesy in the United States.
  • 1889: The international prototype metre was defined as the distance between two lines on a standard bar composed of an alloy of $90 \%$ platinum and $10 \%$ iridium, measured at the melting point of ice.


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