In June 1792 the French astronomers Jean Baptiste Joseph Delambre and Pierre François André Méchain set out to measure the meridian arc distance from Dunkirk to Barcelona, two cities lying on approximately the same longitude as each other and also the longitude through Paris.
Using this measurement and the latitudes of the two cities they could calculate the distance between the North Pole and the Equator in classical French units of length and hence produce the first prototype metre which was defined as being one ten millionth of that distance [REF].