Pierre Francois Andre Mechain, a French mathematician and astronomer, born in Laon, Aug. 16, 1744, died in Castellon, Spain, Sept. 20, 1805. After receiving a limited education, he became a mathematical tutor, devoting his leisure hours to the study of astronomy. Trying to sell his telescope in order to assist his father, he attracted the notice of the astronomer Lalande, who procured him a situation as hydrographer under the government. In this capacity he assisted M. Bretonniere in surveying the French coast between Nieuport and St. Malo; but his attention was chiefly directed to the theory of eclipses and comets, 11 of the latter having been discovered and the orbits of 24 computed by him. In 1782 the academy of sciences admitted him to membership and awarded a prize to his "Memoir on Comets." Under the republic he was employed, together with Delambre, to measure the arc of the meridian comprised between Dunkirk and Barcelona. On returning to Paris, he refused to deliver his papers to the academy, because he had detected a difference of 3" in his calculations respecting the latitude of Barcelona. After being appointed director of the observatory of Paris, he solicited the board of longitude to permit him to prolong the measurement of the arc from Barcelona to the Balearic islands, that he might have an opportunity of correcting his error.

The board consented, and Mechain set out for Spain to conduct the operation, but fell a victim to an epidemic disorder on the way. The most important of his scientific papers are to be found in the Memoires des savants eirangers, in the Transactions of the French academy, and in the Connaissance des Temps from 1786 to 1794, of which he was for some time editor.