MECHAIN, Peter Francis Andrew, a well-known practical astronomer and geographer, was born at Laon, on the 16th April 1744. His father was an architect, and educated him with the intention of making him his successor in his business. He afterwards took charge of two young men at Sens, as their private tutor, and accidentally became acquainted with Lalande, under whose patronage he was subsequently brought forward as an observer, surveyor, and computer. He made two voyages with Μ. de la Bretonniére, and assisted him in surveying some parts of the coast of France. He was afterwards employed in various computations by the Marquis de Chabert, and the Duc D’Ayen. Having obtained a prize from the Academy of Sciences in 1782, for a Memoir on Comets, he became a member of the Academy the same year. About the year 1785, he undertook the publication of the Connaissance des Terns, and continued it till he was employed in geodetical operations at a distance from Paris. He was appointed member of a committee, along with Cassini, de Thury, and Legendre, to meet the English astronomers for the determination of the relative situation of the observatories, which had been proposed by Cassini. It was in these operations that he first brought Borda’s circle into general use. In 1791 he was appointed, in conjunction with Delambre, to execute the intentions of the Constituent Assembly, with regard to the determination of a basis of linear measures. A variety of delays and difficulties occurred in these operations. In Spain he was wounded in the head and side, by an accident which occurred whilst he was inspecting a water-wheel; and the political circumstances of the times produced many embarrassments, which caused him to linger in Italy perhaps a little longer than was actually necessary; but the establishment of the Bureau des Longitudes, and his nomination as a member of it, determined his immediate return to Paris. He was now director of the Observatory, and he entered with great zeal on a series of observations, which were to rival those of Flamsteed, of Bradley, and of Maskelyne; but he seems to have been a little tired of the confinement, and he readily accepted, or rather solicited, the appointment to assist in the measurements required for the still farther extension of the arc of the meridian to the south of Barcelona. But the secret motive for his seeking this humbler employment appears to have been a desire to remove some doubts which he entertained respecting the latitude of Barcelona, as it appeared after his death from his papers, that there had been a discordance of 3' ’ in some observations which he had not made public. In this unfortunate undertaking, he paid a heavy penalty for any want of candour which may have been attributed to the concealment. Shipwreck and disease awaited him; and he died at last, on the 20th of September 1805, of a fever, which fatigue and a bad climate had brought on. From the time of his accident in Spain he had become habitually melancholy and timid, though regardless of personal danger in the pursuit of his professional objects. His whole time was occupied in observing and calculating; he published little; and never ventured to advance any reflections on the subjects which employed him, being probably more in the habit of acting than of speculating. He married, in 1777, Mademoiselle Thérèse Maijon, with whom he had become acquainted at Versailles. This connexion was in every respect happy; he was indebted to it for a competent fortune, and he left a daughter and two sons.

1. Of his publications the most important are to be found in the Mémoires des Savans étrangers; that is, besides some Observations of eclipses and occulaticyns, a Memoir on the comets q/T532«wíZ1661, showing that theyare not the same; and their non-appearance seven or eight years afterwards fully; ustified his conclusions, and the adjudication of the prize. 2. In the Memoirs of the Academy, from 1782 to 1784, there are several of his Observations of transits, eclipses, occulations, and comets. 3. There are also some letters of Méchain in Zach’s Geographical Ephemerides about 1800, on the instruments of ∖hoParisian Observatory, and on other subjects. 4. He edited the Connaissance des Τems, from 1786 [7:14:460]to 1794. (See Lalande.) 5. Base du système métrique, décimal. 3 v. 4. Paris, 1806, 1807, 1810. This last is the joint work of Méchainand his friend and colleague Delambre.