A witness of the quest to define the ‘Metre’.

We all are aware of the metre unit but how was it established? Was this tower related to that historic event?

After the French Revolution (1789), it was decided that a standard unit to measure distance was needed. The unit was named metre and it would be the one ten-millionth of the distance between the north pole and equator via the meridian passing through Paris.

While some estimates existed, a more accurate measurement of the meridian was required. Two surveyors(Pierre Méchain & Jean-Baptiste Delambre) walked a total distance of almost 1000km between 1792 – 1798. Delambre started from Dunkirk in northern France and Méchain started from Barcelona. They met at Rodez.

Méchain used this tower to measure coordinates of Barcelona, and then this tower served as the rig point for measurements further north. Their trigonometric measurements were further extrapolated, and the distance was finally calculated.

This tower was a defensive and signalling structure originally built in the 11th century and rebuild several times till the 1770s.