Background
Pierre François André Méchain was born on August 16, 1744, in Laon, Picardie, France to the family of Pierre-François Méchain, a master ceiling plasterer of modest means, and Marie-Marguerite Roze.
6-8 Avenue Blaise Pascal, 77420 Champs-sur-Marne, France
In Loan that Pierre Méchain was educated by the Jesuits and as a young boy his aim was to become an architect, although his main hobby was astronomy. His ability at mathematics was soon spotted, however, and he was advised to study at the École Nationale des Ponts et Chaussées in Paris. Studying there was, however, expensive and Méchain's father did not have the necessary resources to be able to support his son. Méchain had to interrupt his studies.
6-8 Avenue Blaise Pascal, 77420 Champs-sur-Marne, France
In Loan that Pierre Méchain was educated by the Jesuits and as a young boy his aim was to become an architect, although his main hobby was astronomy. His ability at mathematics was soon spotted, however, and he was advised to study at the École Nationale des Ponts et Chaussées in Paris. Studying there was, however, expensive and Méchain's father did not have the necessary resources to be able to support his son. Méchain had to interrupt his studies.
Pierre Méchain was a member of the French Academy of Sciences.
Pierre Méchain was a member of the Royal Society.
An elderly Pierre Méchain, shown wearing the cross of the Legion of Honor.
Astronomer geodesist hydrographer scientist
Pierre François André Méchain was born on August 16, 1744, in Laon, Picardie, France to the family of Pierre-François Méchain, a master ceiling plasterer of modest means, and Marie-Marguerite Roze.
In Loan that Pierre Méchain was educated by the Jesuits and as a young boy his aim was to become an architect, although his main hobby was astronomy. His ability at mathematics was soon spotted, however, and he was advised to study at the École Nationale des Ponts et Chaussées in Paris. Studying there was, however, expensive and Méchain's father did not have the necessary resources to be able to support his son. Méchain had to interrupt his studies.
Méchain had to interrupt his studies and take on the role of tutor to two young boys from a noble family some 50 km from Paris. His tutoring position put Méchain on a firmer financial footing and he was able to save enough to buy some good quality astronomical instruments so that he could pursue his hobby.
In some fashion, Méchain came into communication with Lalande, who sent him the proofs of the new second edition of his Astronomie. Filled with enthusiasm, Méchain made such rapid progress in this study that in 1772 Lalande procured for him a position as hydrographer at the naval map archives (Depôt de la Marine) in Versailles. The archives were then a seat of political patronage and intrigue, and, caught in the political crosscurrents, Méchain twice lost his job; but each time he was reinstated because of his competence as a map-maker. The archives were soon transferred to Paris, and there he drew up the maps for the shoreline from Nieuwpoort in Flanders to Saint-Mato.
Beginning in 1780 he determined the network of fundamental points for large military maps of Germany and northern Italy.
Meanwhile, Méchain was also active as an astronomical observer, his early efforts being crowned in 1781 with the discovery of not one but two comets. He calculated the orbits for both, and in the following year, he calculated orbits for the comets of 1532 and 1661, proving, contrary to general expectation, that they were not the same. This research won both the 1782 prize of the Académie Royale des Sciences and admission to its ranks. Encouraged by these successes, Méchain threw himself into observing with still greater zeal, and ultimately discovered nine more comets, including the remarkable short-period one now named after Encke. He calculated the orbits for all of these, as well as thirteen found by other observers. In addition he found many nebulae, which were incorporated by Charles Messier into his famous catalogue of clusters and nebulae. In 1785 he became editor of the French national almanac, Connoissance des temps, and he prepared the seven volumes for 1788 to 1794.
In 1787 a joint Anglo-French project undertook the triangulation between the Greenwich and Paris observatories. Méchain was chosen as one of the French commissioners, along with Legendre and J.-D. Cassini. Both countries engaged in a friendly rivalry to produce new and more accurate measuring instruments. In France, Borda developed the principle of the cercle répétiteur, or repeating transit, in which after the first set of readings, the circle was clamped with the telescope and moved back to the original line of sight. In this way the angles could be measured against different segments of the circle, thus averaging out graduation errors. The commissioners systematically tested Borda’s device, with Méchain using the older equipment; the tests demonstrated the great superiority of this new circle.
In 1790 the National Assembly approved an Academy proposal to establish a decimal system of measures, and Méchain and Delambre were designated to carry out the fundamental geodetic measurements for a new unit of length. This unit, the meter, was intended to be one ten-millionth part of the distance from the terrestrial pole to the equator, and it was to be based on an extended survey from Dunkerque to Barcelona, Méchain was assigned the shorter but more difficult southern zone, the previously unsurveyed region across the Pyrenees.
The new repeating transit became the fundamental instrument of the survey, but not until June 1792 was the new equipment, including parabolic mirrors for reflecting signals, ready. By this time the Revolution was engulfing France and the monarchy was tottering; Méchain with his suspicious array of instruments was arrested at Essonnes just south of Paris as a potential counterrevolutionary. Only with much difficulty was he located and released two months later, so that he could continue his journey to Spain. In September and October, he swiftly carried out the triangulation between Perpignan and Barcelona. During the winter of 1792–1793 he undertook the astronomical observations to establish the latitude of Barcelona, almost at the southernmost limit of the meridian. At the same time, he investigated the possibility of extending the meridian 2½º southward to the Balearic Islands. Otherwise, only a few weeks of work remained to complete the network across the frontier.
Méchain's plans were abruptly interrupted at the beginning of spring in 1793 when, invited by a friend to inspect a new hydraulic pump in the outskirts of Barcelona, he was invoked in an accident. While trying to start the machine, a friend and an assistant were caught in the mechanism. Méchain, rushing to aid them, was struck by a lever that knocked him violently against the wall, breaking some ribs and a collarbone. He was unconscious for three days and afterward was forced to remain completely immobile for two months. By June he still did not have the use of his right arm; but, undeterred, he used his left hand to make the solar observations at the summer solstice.
During Méchain’s convalescence, the open war had broken out between Spain and France, and he was denied a passport to return home. Profiting from his captivity, he determined the latitude of Mont-Jouy, just south of Barcelona, and surveyed the triangle connecting these points. He then noticed a 3″ discrepancy in the latitude previously obtained for Barcelona. Anguished by his failure to find the cause, and blaming himself for the error, he kept the discrepancy a carefully guarded secret. In the remaining years of his life, he became a driven and tormented man, whose behavior was mysterious and inexplicable to his colleagues. Delambre, who found out the secret only when he inherited the notes, intimated that Méchain simply put too much trust in the precision of the repeating transit.
Eventually, Méchain obtained a passport for Italy, and he managed to reach Genoa in September 1794. Saddened by the guillotining of several of his colleagues and in poor health, he delayed his return to France, not embarking for Marseilles until the following year. After additional hesitation, he journeyed to the vicinity of Perpignan and in September 1795 resumed the triangulation. Méchain slowly continued his work through 1796 and 1797. Meanwhile, after a fifteen-month suspension for political reasons, Delambre proceeded with measurements of the northern part of the network and in April 1798 he invited Méchain to join him in linking the sections. Méchain remained incommunicado, and Delambre finally sought him out in Carcassonne. Méchain expressed a stubborn desire, inexplicable to Delambre, to return to Spain for further latitude determinations. Faced with the choice of returning to Paris and the warm welcome of his colleagues, or remaining forever an expatriate, Méchain reluctantly came back to Paris. There he was less than cooperative in presenting his observations to the commissioners charged with setting up the decimal metric system.
In Paris, he was made the director of the observatory, considered a just and tranquil reward for an astronomer who had labored so faithfully without a real astronomical position. But to Méchain nothing was right, and in a remarkable letter to Franz von Zach, he aired his complaints publicly. Always he yearned to return to Spain; and eventually the Bureau of Longitudes approved the extension of the meridian to the Balearic Islands, a project that would render his imperfect latitude of Barcelona unnecessary. The Bureau, believing that Méchain’s abilities were best employed as director of the observatory, appointed another astronomer to extend the meridian, but to their surprise, Méchain insisted on doing it himself.
The expedition left Paris on 26 April 1803 but encountered unexpected delays in Spain. When the ship at last departed for the islands, an epidemic of yellow fever broke out on board. Méchain eventually reached Ibiza, but he discovered that his mainland station at Montsia could not be sighted from the island. Thus he was obliged to change the pattern of triangles and survey a greater distance southward in the mountains along the Spanish coast. Exhausted by the work and further weakened by fever and a poor diet, he collapsed and died on 20 September 1804. Several years later the extension of the meridian was completed by Biot and Arago.
Méchain was arrested at Essonnes to the south of Paris as a potential counterrevolutionary. Only with much difficulty was he located and released two months later, after that he continued his trip to Spain.
Méchain was concerned about the quality of the results of his survey and refused to publish them for a long time.
Pierre Méchain was a member of the French Academy of Sciences and the Royal Society.
Mechain was a passionate comet hunter, and found nearly a dozen comets on his own, or as a co-discoverer, with others.
In 1777 Méchain married Barbe-Thérèse Marjou, whom he met while working in Versaille. They had two sons, Jérôme-Isaac born 1780 and Augustin born 1784, and a daughter. Their eldest son was named after Lalande who was his godfather.