Born in Amiens in northern France, Delambre was most unusual for a mathematician and astronomer in that he did not begin the serious study of his subject until he was well over 30 years old. As a student he had been interested in the classics and only turned to the exact sciences when he was 36. He published tables of Jupiter and Saturn in 1789 and of Uranus in 1792. He also measured an arc of the meridian between Dunkirk and Barcelona to establish a basis for the new metric system. He succeeded Joseph de Lalande as professor of astronomy at the Collège de France in 1795. In his later years he devoted himself to a monumental six-volume Histoire de l'astronomie (1817–27; History of Astronomy).