Heading of letter from Arago as a member of the French Royal Academy.

135 brass disks form the Paris meridian that once challenged Greenwich as the zero longitude line.
Francois Arago

Mathematician, physicist, astronomer, politician, Francois Arago was born on 26 February 1786, in Estagel, Roussillon France, where his father was the mayor. He showed an early flair for mathematics when he was in the top five students in the 1803 intake to the Paris École Polytechnique. There he met Poisson, first as a teacher and then as a friend.

In 1805, Poisson asked Arago to complete the meridian arc measurements in order to determine the exact length of a metre. In addition, he was to use a pendulum to measure the force of gravity at certain points to be able to estimate more accurately the shape of the earth.

By 1808 he and his assistant Biot were in Mallorca, although the latter returned Paris once they had determined the latitude of Formentera, the southernmost point of their survey. A wall or two is all that remains of an observatory they built on Mola de s’Esclop (Galatzó) in the Tramuntana Range. Fires were lit there and Formentera and the summit of Camp Vell in Ibiza to measure the triangulation To measure the triangulation formed between there, Formentera and the summit of Camp Vell in Ibiza, fires were lit on the different peaks and the distances measures with very powerful lenses. When the French entered Spain, the unrest extended to Mallorca and the local inhabitants were quick to assume Arago was a French spy, lighting the bonfires to signal the enemy.

He was imprisoned in Bellver Castle and remained there for two months until July 1808 when he was able to escape by fishing boat. He landed in Algiers where the French consul supplied him with a forged Austrian passport and he set off by boat for Marseilles. Within sight of the port, his boat was boarded by a Spanish corsair and he was imprisoned in Roses where he was soon recognised by the authorities and put on a boat for Marseilles.
page 2

Spanish flag. home