The Broken Arc

The fact is that nowhere, these days, is anyone genuinely happy, and that of the countless faces assumed by the Ideal—or, if you dislike the word, the concept of something better—travel is one of the most engaging and most deceitful. All is rotten in public affairs: those who deny this truth feel it even more deeply and bitterly than those who assert it. Nevertheless, divine Hope still pursues her way, assuaging our tormented hearts with the constant whisper “There is something better—namely, your ideal!”

—GEORGE SAND, Winter in Majorca

Redeemed from his suicidal melancholy in the remote Montagnes Noires, Méchain had been elevated to the celestial post of the nation’s chief astronomer. Honored by the nation’s leaders for his scientific integrity, he had been welcomed into the arms of his loving family and respectful colleagues. No wonder his conscience troubled him.

To expiate his sins, Méchain threw himself into his new administrative role. He complained that the Observatory had been neglected during his absence, and he vowed to transform it into the world’s premier astronomical facility. He bought superior telescopes and decided on their placement in the building. He resumed his own celestial observations, discovering two comets in 1799 and another in 1801, and joining in the exciting hunt for the newest members of the heavens, the minor planets known as asteroids. Yet he was miserable.

Friends and colleagues were baffled. He enjoyed every reward a savant could desire: a capable wife, a warm family, the most eminent position in his field, the respect of his peers, and last but not least—this was Paris, after all—the sumptuous Cassini apartments and full use of the Observatory gardens. Some colleagues found him reserved, severe, even caustic. Some, behind his back, took great pleasure in reviling his character. Yet everyone agreed he was a savant of unimpeachable integrity.

These public accolades only made his secret more unbearable. The more honors that were showered on him, the more unworthy he felt. He was a hollow impostor, a scientific fraud—and in a matter of such terrible consequence. He had introduced an error into the fundamental scientific value, the measure that would forevermore serve as the foundation for all scientific and commercial exchange. He avoided his colleagues, retreating to his apartment whenever one of them came by the Observatory.

Meanwhile, his one-time partner had been given the honor of composing the official account of their expedition. The choice was understandable. Although Delambre was the junior colleague (five years younger in age, with ten years less tenure in the Academy), he combined a background in the humanities with the necessary technical know-how—plus he had actually performed the bulk of the work. Delambre planned to publish everything: the tale of their adventures, the full roster of their data, all their formulas and technical apparatus. The work would be entitled the Base du système métrique décimal (The Foundation of the Metric System) and would run to two thousand pages in three thick volumes. It would show the world the exactitude of their labors. To complete the first volume by the end of the year, he needed Méchain’s data.

No wonder they resented each other. Their mission was done, yet they remained tethered together. Delambre needed the complete data of a man who had decided—out of spite, it must have seemed—to supply the absolute minimum, and in his own good time, too. As for Méchain, everyone knew he had only completed his mission with Delambre’s help: reason enough for him to begrudge Delambre’s success. On top of all this, Delambre was one of the First Consul’s favorites—Napoleon had taken a liking to him on his first day at the Academy—whereas the First Consul hardly knew who Méchain was. Méchain resented Delambre’s facile way with words and pretentious classical learning. He despised the ease with which the cloth-seller’s son moved in the highest circles of the new France.

The fall from camaraderie was hard. For seven years the two savants had trekked the high geodetic plateau, first in opposite directions and then on convergent paths, but always in a spirit of collegial rivalry. But a year in the capital had turned them into petty quarrelers. Paris can do that to you. There is something about the proximity of money and power that makes people peevish. Late in 1800 Delambre was elected president by rotation of the Bureau of Longitudes, making him Méchain’s nominal superior. A squabble ensued over who controlled the account books. A question was raised as to whether Méchain could officially claim the title of director of the Observatory. Méchain wrote bilious letters denouncing his “hyperpedantic and outrageously ambitious” colleague who had overstayed his term as president of the Bureau of Longitudes. Méchain complained that he had been reduced to begging his colleague for firewood and candlelight. Privately, he referred sneeringly to Delambre as his “absolute master.” Publicly, he threatened to resign unless he was formally installed as Observatory Director.

Deeper grievances festered. As Méchain now saw it, Delambre had deliberately deprived him of his rightful honors by relegating him to a secondary role on the meridian mission: grabbing two thirds of the triangles, muscling in on the latitude of Paris, and seizing both baseline measurements—including the one at Perpignan, which clearly lay within Méchain’s sector. And Méchain had proof of this. Late in 1799 he had become Borda’s scientific executor and had thereby gained access to all the commander’s papers. Among them he discovered the series of letters between Delambre, Borda, and his own wife. One can imagine the reaction of Méchain—a man given readily to paranoia—as he read of the conspiracy unfolding against him: their plan to lure him down from the Montagnes Noires, his wife’s secret mission to Rodez, their exchanges of confidences, their vows of silence. They had manipulated him, treated him like an underling, and tricked him across the finish line.

By the time Méchain had reclaimed full recognition as director of the Observatory, Delambre had risen higher still. In 1801 Napoleon added the presidency of the Academy of Sciences to his other titles, making him ruler of both the nation and the sum of its knowledge. Napoleon’s first act as President was to reorganize the Academy, appointing Delambre to the post of Permanent Secretary. This made the cloth-seller’s son the most powerful figure in French science: successor to Condorcet, liaison to the highest political authorities, author of its eulogies, and hence guardian of his colleagues’ reputations.

These circumstances go some way toward explaining why, on September 6, 1801, a member of the Bureau of Longitudes (Méchain, presumably) proposed extending the meridian measure south of Barcelona, as far as the Balearic Islands. The extension had long been one of Méchain’s fondest ambitions, and he insisted on his right to report on its feasibility. Such an extension would improve knowledge of the shape of the earth by anchoring the arc’s southern latitude on an island, where nearby mountains could not distort the readings. The new arc would straddle the 45th parallel of latitude, making any extrapolation from the partial arc to the quarter meridian less sensitive to the earth’s eccentricity. These were excellent scientific rationales for the expedition, and Méchain agreed to report on them—if, and only if, he was allowed to lead it.

Why would a fifty-seven-year-old man, reunited with his family after seven years of backbreaking travels, wish to undertake such a mission? Delambre and the rest of his colleagues argued that the task be given to someone younger. Méchain was needed in Paris, where he had begun to accomplish wonderful things at the Observatory. Moreover, he had just recovered from a severe illness which had nearly cost him his life, and which he himself blamed on the “long travails and thousand vexations of my mission, as well as those which followed upon my return.” But the more his colleagues protested, the more adamant he became. As Observatory Director and the nation’s senior astronomer, Méchain had the right to send whom he chose. And he chose to send himself.

Méchain had something to prove. He would prove he did not need Tranchot to lay out geodetic triangles. He would prove he could traverse an arc as great as Delambre’s. He would prove he did not need his wife’s help to complete a mission. Above all else, he would prove he could be trusted. Beneath their accolades Méchain could sense his colleagues’ skepticism. (They were professional skeptics.) He still had yet to release all his data for the latitude of Barcelona. He had not handed his logbooks over to Delambre. Only a new expedition could redeem his reputation, the thing he held most dear.

He had a secret motive as well. By extending the arc to the Balearic Islands, he would leapfrog the contradictory latitudes of Barcelona and fix a new secure southern anchor for the meridian. This was not a task he could hand over to someone else. Another savant, triangulating from Barcelona, might discover that its latitude did not match the published results. Already Alexander von Humboldt, on his way to South America, had stopped in Barcelona, checked himself into the Fontana de Oro, and set up his own repeating circle on the hotel terrace. He had taken latitude measurements there, he said, to follow in the footsteps of the illustrious Méchain. Was no place on earth safe from these prying savants? Was no fact of nature secure from their meddling? Mercifully, the young German had devoted only one night to observation, and his results did not contradict Méchain’s findings. But he had posted his data privately to Delambre, and Delambre had noted some minor discrepancies.

In the end, however, all these rationales pale before the only motive that ever really justifies scientific labor. To triangulate across the Mediterranean to the Balearic Islands would require measuring a geodetic triangle with sides 120 miles long, whereas ordinary triangles had sides of forty miles at most. It was a stupendous challenge: an expedition across uncharted terrain. Méchain had long held the extension to the Balearic Islands “close to his heart.” It was a challenge he could not resist.

That is not to say that the mission served no practical purpose. As Méchain himself astutely noted in his proposal to Napoleon, the expedition would cement the “intimate union” between France and Spain. The Balearic Islands occupied a strategic position in the western Mediterranean. Indeed, the British navy had occupied the island of Menorca in 1798 to intercept Napoleon’s invasion of Egypt, and Spain had only recovered the island in March 1802 when Britain and France signed the Treaty of Amiens. That treaty had ended a decade of warfare and opened the world’s sea lanes to France. Yet the peace was precarious, with Britain and France already probing for advantage. In September 1802 Napoleon—on Delambre and Laplace’s say-so—approved this scientific thrust into the western Mediterranean.


So scientific history repeated itself: the first time as epic, the second time as quixotic farce. The expedition began, appropriately enough, with Méchain on one of his periodic upswings. He spent 1802 assembling a team. This time, he intended to do things right. To maintain the repeating circle, he recruited a young naval engineer named Dezauche. For diplomatic cover he invited a former student of his, Jean-Baptiste Le Chevalier, who had just returned from a year spent in Madrid, ostensibly as an apostle for the metric system, but more probably as a spy. And for moral support, Méchain took along his younger son, Augustin, now a strapping lad of eighteen, born on the grounds of the Observatory and home schooled in astronomy.

Méchain also adapted his equipment for the mission. He refitted his Borda circle with more powerful lenses to triangulate far across the Mediterranean. And he procured outsized parabolic reflectors—some of them specially ordered from London—to take accurate nighttime readings. By early 1803 all the human and material elements were ready. He reminded his team to bear in mind that “never before and never again will anyone undertake so vast and important an operation under the watchful eyes of all the savants of Europe, subject to their criticism and to those of the centuries to come.”

As before, Méchain’s final act before leaving for Spain was to hand over a document: not a power of attorney this time—Madame Méchain had already been authorized to administer the mission’s 20,000-franc budget and run the Observatory in his absence—but rather the data Delambre had waited three years to publish. This consisted of his geodetic results, described in indifferent prose, and the same summary data he had already supplied to the International Commission.

Méchain expected to complete his mission in six months, and be back in Paris in ten. He planned to leave in early February, measure the triangles before the summer haze set in, observe the new southernmost latitude on the island of Ibiza during the winter, and resume the directorship of the Observatory by spring. He planned to do everything right this time. But the usual delays—as inevitable as they were unanticipated—prevented him from leaving Paris until April 26. After passing through Perpignan, he and his team sailed into Barcelona harbor on May 5, 1803—at which point everything fell to pieces.

Nothing in Spain was ready. Everywhere he turned he found obstruction, incompetence, conspiracy. On his first day in Barcelona the governor-general informed him that Madrid had yet to supply the passports he would need to travel to the islands. Next he learned that Captain Enrile of the frigate Prueba (Test), who had agreed to transport him across the straits and assist in the measurements, had been held up in the port of Cartagena, apparently on orders from Madrid.

These obstacles—or so his Spanish friends informed him—were no accident. Father Salvador Ximenez Coronado, director of the Royal Observatory of Madrid, hated France, hated the French Revolution, and considered the metric system a “fantastical lie” to pervert Spanish virtue. José Chaix, the Observatory’s vice-director, who had come to assist Méchain, warned the Frenchman that Ximenez Coronado was “ignorant, malevolent, and a mortal enemy of the sciences and all who cultivate them.” From Madrid he was blocking any assistance for the expedition. At last Méchain had a real conspiracy to contend with.

Behind these petty intrigues loomed the prospect of renewed war between France and Britain. Spain hoped to stay neutral, but seemed likely to be drawn into the conflict over the Mediterranean sea lanes. Méchain’s Paris colleagues asked their British counterparts to intercede with the British navy and grant safe conduct to the peaceable scientific mission. In the meantime, Méchain deferred his sea voyage. Instead, he set off with his team down the Catalan coast, scouting out new stations in the mountains south of Barcelona.

By attaching a new chain of triangles to his old chain via the stations of Montserrat and Matas, Méchain intended to bypass his old measurements at Mont-Jouy and the Fontana de Oro. During July and August, through the all-consuming Catalan summer, he sized up stations as far south as Montsia, an isolated 2,200-foot peak that marked the border where Catalonia ended and the Spanish province of Valencia began. There, on the dusty mountain above the pink flamingo marshes of the Ebro river delta, he was joined by Enrile, and they began triangulating their way back north toward Barcelona. All that autumn they worked, through torrential rains and gale-force winds. It was just Méchain’s bad luck that the mild Catalan autumn had suddenly turned ferocious. By late October he found himself back up at the Montserrat monastery, enjoying its thousand-year-old tradition of hospitality, and climbing once again to the Notre Dame chapel to take his measurements on top of the organ-pipe stone pinnacle. (Five years later, the monastery would go up in flames during Napoleon’s invasion.) Then in early November he went back down to Barcelona to prepare again for his sea trip across the straits.



This drawing by Méchain shows the position of the reflecting mirror he placed in front of the portico of the small chapel of Notre Dame, on a pinnacle of rock high above the monastery of Montserrat in Catalonia. (From the Archives de l’Observatoire de Paris)

During his six months in Spain he had measured five coastal triangles, but he had yet to learn whether his mission was feasible. The evidence so far was discouraging. Success depended on measuring a giant triangle across the straits to his arc’s final anchor, the southern island of Ibiza. Tightrope-walking his way up and down the Catalan coastline, Méchain had strained to catch sight of the island with all the telescopic power at his disposal. His Spanish hosts had sworn that from the summit of Montsia he would be able to see Ibiza as clear as daylight, but so far neither he nor Captain Enrile had been able to make it out through the autumn mist and rains. The Spaniards, Méchain feared, had lied to him.

The time had come to cross over to the islands, reverse perspective, and see for himself whether the coastal range was visible from there. The French ambassador in Madrid had finally procured him a passport. But no sooner had the Prueba pulled into Barcelona harbor to ferry her captain and learned passenger across the straits than half the crew died of yellow fever. Terrified, the port authorities ordered the ghost ship to sail for quarantine—with Enrile courageously volunteering to resume command of his contaminated vessel. Méchain begged his friend not to go, and instead to remain with him in Barcelona “where he could be useful to me.” Enrile insisted that his duty lay with his vessel and the remnants of his crew.

To the south, Andalusia was infested with yellow fever. Three hundred people a day were dying in Málaga alone, and the zone of infection was spreading. Rumor and panic surged up the coast. Barcelona’s wealthier citizens fled to the countryside before the city was sealed shut. The French government deployed a cordon of troops along the frontier to prevent any incursion of the disease. Stuck in Barcelona—lodged once again in the Fontana de Oro—his six-month supply of funds exhausted, Méchain’s courage began to fail him.

It was like a nightmare. On a December evening a decade earlier, from the tower at Mont-Jouy, he had sighted a signal flare on the island of Mallorca. Then war and injury had snuffed out his ambitions. Now war and disease threatened to cut him off again, while his hand-picked team deserted him. Three days after the team returned to Barcelona, Le Chevalier, Méchain’s former student, lit out for southern Spain in search of classical antiquities. Then Chaix left too, returning to the safety of Madrid. It was not just out of fear of disease. Both men complained that Méchain would not let them even look through the repeating circle.

Méchain had never understood the art of leadership: when to share responsibility, as well as when to assume it. For him, the quest for precision was like a voyage through purgatory, with each savant answering for his own sins. And Méchain was too absorbed in his own self-criticism to let others shine. He showed no tolerance for even their most trivial mistakes. When he opened a case of poorly packed reflectors, it was enough to convince him that he had erred, even that once, in trusting others. The ulcerating question, of course, was whether he could trust himself.

To whom could he turn in this moment of self-doubt? To none other than the man he most resented, his one-time partner, Jean-Baptiste-Joseph Delambre. A series of plaintive letters, as pathetic as any he had ever written, spilled from his pen. The winter was cold and the Spanish had no notion of indoor heating. What should he do? Which plan should he adopt? Might the Bureau of Longitudes supply him with additional funds? He even offered to return to Paris if the Bureau thought his “feeble lights” could be better employed in the capital. “This is truthfully and sincerely my current situation, my dear colleague, and I tell you all this without complaint. . . .”

It was as if nothing had changed, nothing had been learned. His son and the loyal Dezauche would stick with him to the end. To replace his renegade assistants he enlisted the aid of a Trinitarian monk named Agustín Canellas, a self-proclaimed astronomer, confident of his worth and eager for a role in a historic expedition. More valuable was the support of a local grandee, the Barón de la Puebla, an amateur astronomer from Valencia. The baron assured Méchain that Ibiza would be visible from the coastal mountain of Desierto de las Palmas, south of Montsia in the province of Valencia; and better yet, he offered to establish a signal on its peak while Méchain observed from the islands.

Finally, in early January 1804, Méchain arranged passage to Ibiza for himself and his son on the Hypomene, a Spanish frigate named after the youth in Greek mythology who dropped distracting golden apples as he raced the swift Atalanta. No such swift passage ensued. Méchain’s bad luck at sea held. A simple one-day crossing became a three-day torture of calms, contrary winds, and high seas. Unable to enter the main port at Ibiza Town, the Hypomene swung east around the island to a cove off Punto Grosa. Yet no sooner had they dropped anchor than a troop of armed islanders assembled on the shore to deny them landing. They would not even deliver a letter, for fear it would spread yellow fever. The ship had only two days of provisions remaining on board. Food and water were running low. Every effort to sail out of the cove failed. The Hypomene’s captain pleaded with the islanders to convey their situation to the governor, across the island. Two days passed before a response was shouted back: the crew might cut wood and collect water in an isolated spot while the governor looked over the mission’s official papers. These were duly transmitted, after first being carefully doused in vinegar. Reassured that the travelers were free of infection, the governor sent word that Méchain and one naval officer might search out a suitable station on the island.

About half the size of Oahu, Ibiza today is an “international resort destination.” Originally settled by Phoenicians, Ibiza Town wraps around its conical hillside like a white Moorish turban, the eyes of its cubical houses turned south toward Africa. The interior of the island is mountainous and was then sparsely populated. Poverty existed side by side with Edenic fertility: figs, almonds, grapes, melons, and olives grew in abundance. Palms fringed the coast, and pine trees covered the rugged hillsides. But Méchain’s unlucky star had followed him onto this island paradise. Ascending a rocky trail to the peak of Los Masons, he fell off his mule, injuring his head and spraining his wrist. He refused to call a halt. “It was nothing . . . ,” he wrote to Dezauche, still in Barcelona, “and you may laugh over it at the table of the Fontana de Oro, or wherever else you wish.” Worse than any physical injury, however, was the disappointment that awaited him on the top of Los Masons. He had been told the peak afforded the best view of the mainland coast, and indeed he could see a range of mountains to the west, as well as the big island of Mallorca to the north. Unfortunately, he could not make out the peak of Montsia, the southernmost station in his chain of completed triangles. The Spaniards had indeed lied. “I thumb my nose at them,” he wrote. This left him with two alternatives, each of which presented its own complications. He could return to the coast to extend his mainland triangle chain south into Valencia before triangulating across the straits to Ibiza—although this would mean that his chain would temporarily veer far west of the meridian. Or he could build his chain of triangles by island hopping: triangulating from Barcelona to Ibiza via Mallorca—although this would mean measuring several giant triangles as well as a baseline on Mallorca. Either way, the season for latitude measurements was ending and his budget was almost spent.

Not only that, but when he viewed the entire circumference of Ibiza from the top of Los Masons, his heart sank still further. He could not locate the Hypomene. The ship was no longer in its cove off Punto Grosa, nor had it docked in the main port at Ibiza Town. The boat had vanished, along with his son and his instruments. It was enough to make a savant curse his fate. He prepared himself for the eventuality that “my last leave-taking from my family and friends was my eternal adieu.”

Again he wrote to Delambre. Might his colleague recommend a course of action? What did the Bureau of Longitudes think of his two alternatives? Would the island-hopping scheme succeed? Would the westward deviation along the coast distort the results? And while he was at it, might he vent his frustration? “Hell and all the plagues it spews upon the earth—storms, wars, pestilence and dark intrigues—have been unleashed against me. What demon still awaits me? But vain exhortation will solve nothing, nor complete my task.”

The Hypomene, he soon learned in Ibiza Town, had sailed to Mallorca for provisions. So while he waited for a response from Paris, he likewise booked himself a passage across to the big island. On January 27, 1804, he sailed into Palma, Mallorca’s capital, a busy port town of 30,000 inhabitants, dominated by a hulking ivory-hued cathedral. He spent nearly two months—reunited with his son—on Mallorca, an island known since Roman times as “the fortunate isle.”

Mallorca was more populous than Ibiza, and four times its size. Its northern mountains reached an elevation of five thousand feet, and were covered with snow when Méchain arrived in the winter of 1804. Yet beneath the white peaks its plains were tropical, with groves of oranges, almonds, palms, dates, figs, carob, and plantain. Ruined temples lay scattered across the island. In the twelfth century the Balearic Islands had governed a continental kingdom that included Catalonia and much of southern France. The local Catalan dialect embodied millennia of exchange and conquest, with phrases from Syriac, Greek, Latin, Vandal, Arabic, and Castilian.

It was indeed an enchanted isle, a refuge from time’s march. The town of Palma was ruled by a mechanical “sun clock,” which rang from the Gothic town hall. Legend had it that the sun clock had been brought to the island by Jews from Jerusalem. More probably, the fabled instrument was installed by fourteenth-century Dominicans. The clock divided each day into twelve hours, but hours which lengthened proportionately as the summer days lingered and shrank proportionately as wintry darkness shortened the daylight. Eighteenth-century commentators considered the clock unsuitable for rational administration, but they admitted that the people of Palma found that its bells helped them to regulate the watering of their sumptuous gardens. Standardization lies in the eyes of the practitioner. Sadly, a few decades after Méchain’s visit, the sun clock vanished as mysteriously as it had come.

While he waited for the mountain snows to melt, Méchain conducted astronomical observations in Palma with his son, including a viewing of a dramatic solar eclipse. Not until March did he set out across the island for the north-coast town of Sóller in a fertile valley of orange groves. From there, Méchain and his party—his son, Captain Enrile, and a band of sailors—rode mules as far as the last manor house, then climbed on foot to the peak of Silla de Torrellas. The path was steep, rising nearly one mile in altitude within two miles of the coast. The lower slopes were planted with olive trees, gnarled and shaped by centuries of wind and pruners’ knives, and ringed by stones to ward off erosion. Further up, the pine forests had been logged to build ships for the Spanish navy. Higher still, in the crags, lay the nests of sea eagles and bearded vultures, while the birds circled apprehensively on the currents above. At the summit, they found the traces of the expedition that Méchain had sent across to light signal flares on the mountain a decade earlier, including stakes marking the line of the meridian. Far below, the glassy Mediterranean was streaked with pale blue bands that wandered to the horizon like rivers upon the sea. To the north they could see Barcelona; to the south Ibiza. Which meant that they could indeed triangulate their way through the Balearic Islands—if the Bureau of Longitudes in Paris approved Méchain’s island-hopping plan.

Méchain had essentially settled on this solution when Delambre’s response finally reached him in mid-March, three months after his query. The Bureau of Longitudes recommended the coastal plan. As Delambre demonstrated mathematically to Méchain, the deviation to the west would not distort the results. This coastal plan, moreover, required only one large sea triangle, whereas the island plan would require at least three. Finally, a baseline could be measured more easily along the mainland shore than on an island. To be sure, admitted Delambre, he was far away, while Méchain was on the spot; hence Méchain alone must decide which plan would ensure the most precise results. He wrote: “I wait with much curiosity, and look forward with much interest, to the good report of your journey in Mallorca.”

Méchain deferred to his colleague’s recommendation. At least the coastal chain was a sure thing, whereas every time he set foot on a boat disaster ensued. This meant, however, that his two months on Mallorca had been a waste of time. He ordered his team to summon their energy for one final foray along the southern coast. Though the prospect was exhausting, he warned his subordinates not to relax their vigilance. Continual self-surveillance is the only protection against error.

Even I, who can claim some experience and competence [in geodesy], who know a bit about what methods to use and when to take precautions, even I work in constant fear. I mistrust myself. I continually solicit the views and intelligence of my colleagues at the Academy and the Bureau of Longitudes, and nothing pains me more than when they respond that they rely entirely on me, and that no one is better placed than I to judge what must be done, to choose the right methods, and to carry them through. At such times I feel as if they are spitting in my face. Nothing comes easily, nothing is simple, when one seeks precision. All it takes to be convinced of this is to do a little observing of one’s own.

In early April 1804 he sailed back across the straits for Valencia, where he hoped to procure passports to scout out stations along the coast. For six weeks, during the finest season for geodetic surveying, Méchain waited for passports in the city of gaudy church spires and pungent yellow dust, an honored guest in the residence of the Barón de la Puebla, while his Spanish friends did bureaucratic battle with the diabolical director, Ximenez Coronado. Méchain was impatient to begin. The sun was stirring vapors from the sea, drawing up miasmas from the coastal plains. The heat accumulated daily. The season of disease was approaching. If Méchain did not measure the coastal stations soon, he would not be able to triangulate across to Ibiza until the following winter.

As soon as his passports arrived in mid-June he set out. In eighteen days he covered some three hundred miles on horseback, accompanied by Enrile’s second in command, zigzagging his way through valleys and over ranges. The royal road to Madrid, then under construction, ran straight across the plains for thirty miles until it hit the mountains; there it turned into a narrow track, impracticable for carriages and hazardous for horses.

Along the coast fishermen pulled their triangular-sailed vessels up onto the sand under the palm trees. On the plains irrigation systems dating back to Moorish rule fed cotton fields, orange groves, and stands of mulberry trees (for silkworms). The mountain slopes to the west were terraced for olive orchards. Lizards swarmed over the rocks, some of them a foot and a half long and fierce enough to intimidate dogs. In all, Méchain located fourteen more stations, including two end points for a baseline that would run alongside the Albufera lagoon, a shallow brackish body of water surrounded by rice fields and teeming with flamingos, herons, and numerous waterfowl. The lagoon, connected to the sea via sluice gates, was notorious for its vapors and pestilent insects. In the morning the wall of the inn would be dark with satiated mosquitoes.

Méchain wrote to his wife that the sun had roasted him alive, scorching his face as black as an African’s, except where his skin was peeling off. The summer heat was only now reaching maximum intensity. During the day the views were obscured by vapors. This meant that they would have to use signal flares and take their triangulations at night. As a precaution, he approached the archbishop of Valencia, a tall Franciscan in tobacco-stained robes, who tended to punch petitioners in the face when they bent to kiss his ring. Would he instruct his priests to warn their parishioners not to harass the strange men with the strange instruments who burned lights at night on the mountaintops? Hostility toward the French was fierce. Despite the presence of Castilian officers—or perhaps because of them—Méchain’s party had been threatened on several occasions.

In early July the team dispersed to conduct their nighttime triangulations, beginning at the town of Cullera on the southern edge of the Albufera marsh. While Méchain set up his repeating circle on a rocky outcrop seven hundred feet above the rice fields, each of his collaborators—Captain Enrile, the priest Canellas, loyal Dezauche, and young Augustin—led their respective groups of sailors to the surrounding mountaintop stations and directed their reflectors back at Méchain.

Two weeks later, after Méchain had tacked inland to La Casueleta to set up a new signal by the Roman aqueduct, his collaborators repositioned their reflectors on the surrounding stations. Then, another two weeks later, when he tacked back toward the coast, setting up his repeating circle on a hillock outside the town of Puig, his collaborators again adjusted their reflectors’ positions. By now it was August and the heat was at its most intense. Rather than lodge in the miserable town, a quarter hour walk down the road, Méchain decided to camp out in tents on the hilltop, two hundred feet above the dense coastal air.

Yellow fever had begun to claim new victims. And mixed in with it was something else: what eighteenth-century physicians called “tertian fever” (fièvre tierce). Already it had claimed the life of one of the sailors requisitioned to transport the instruments. On his way to join Méchain at the station outside the town of Puig the sailor had been hospitalized in Valencia, where he died four days later. Several other members of the expedition had been enfeebled by illness. A naval officer, sleeping in the tent beside Méchain on the hillock outside Puig, was seized by a violent fever in the middle of the night. He had to be transported the next morning to a monastery down the coast, then removed to a more salubrious location. Captain Enrile had also fallen ill, though he had since recovered.

More frustrating still, the monk Canellas had inadvertently cost Méchain two weeks of labor. His error of calculation had resulted in a misplaced signal. Those measurements now had to be redone—further proof, if any were needed, that Méchain could not trust others to do his work for him. The monk had also since fallen ill, of a “demi-tertian fever,” and had been bled three times. As a result of these delays Méchain was still outside Puig in late August. He had just turned sixty. In the town at the foot of the hill the disease was subsiding, although three or four deaths were still being reported every day from the town of Puzol a mile up the road. They could hear the funeral bells tolling while they labored. Méchain’s son was still atop La Casueleta; the death toll in the nearby town of Chiva had reached five a day.



This map shows the region where Méchain caught malaria. The area surrounding the Albufera marshes was cultivated with rice fields, and the lagoon itself teemed with flamingos and other waterfowl. The level of water was controlled by a sluice gate at the entrance to the Mediterranean. Méchain’s southernmost station was on the rocky promontory near Cullera, located in the bottom left corner of this map. The town of Valencia is located in the bottom right corner. (Note: This map is oriented so that north is to the right.) (From Antonio José Cavanilles, Observaciones sobre la historia natural, geografía, agricultura, población y frutos del reyno de Valencia [Madrid: Imprenta Real, 1795–97], 1:184; photograph by University of Chicago Library, Special Collections Research Center)

In his last letter to Delambre—another ten pages in his dense crabbed hand—Méchain admitted that he was exhausted. “For until this moment I have not proved successful, and my unlucky star—or rather, fate—which, as you say yourself, my dear colleague, seems to preside over this mission, hardly gives me leave to hope that I will bring it to a happy conclusion.” Yet he did not fear hard labor or the scorching heat; he did not fear anything, except failure. He would continue until he succumbed, he said—which admittedly seemed likely, given that one by one everyone around him had already fallen ill and “I am not made of harder stuff than they, nor am I younger, nor more robust, nor better acclimatized.” He was even ready to come home if the Bureau of Longitudes could find a savant to replace him, one “more able, less maladroit, and luckier than me.” He did not think that finding such a person would prove difficult. He had but one consolation, paltry though it might be: he had nothing to reproach himself with. He had made every effort to fulfill his mission. As he wrote to a friend:

As for the rest, I tell you that though I do not seek death, I am far from fearing it. I would watch its approach without the least regret and in my current state would even consider it a gift from heaven. . . . Never, no never, though I have spent much of my life in suffering and shed many tears over my loved ones and myself, never, I say, have I found myself in a situation so hopeless, so terrifying, and so wrenching. This dreadful commission, whose success appears so far off and so improbable, will more than likely be the end of me, and worse yet, that of my family, and become my tomb and that of my honor.

It was as if, having failed to die on his first trip to Spain, he was now mounting a more determined effort. In frustration, he handed over the final measurements at Puig to Dezauche—the first time he had trusted someone else with the repeating circle—so that he might prepare the next station. He ordered his son to shift his position sixty miles to the north and set up his reflector on the high mountain of Arès. He would himself move inland to the Sierra de Espadán, a three-thousand-foot mountain peak covered with pine trees.

Three days after he set up camp at Espadán, Méchain felt the first thrill of fever. At night, while he waited for the signal lights, icy chills crawled under his clothes. His body shivered in tune with the stars. His appetite had vanished. All that week he took no food, only hot tea. At night, the high dry air was filled with the scent of wild herbs: rosemary, thyme, lavender, and mesquite. One evening, overcome with exhaustion, he fell asleep before the reflectors were lit, and the night watchman did not dare wake him when the lights finally came on. In the morning, Méchain bitterly condemned this failure.



This panorama over the coast of Valencia captures Méchain’s last view as he descended from the Sierra de Espadán to the town of Castellón de la Plana (labeled “b” here). (From Antonio José Cavanilles, Observaciones sobre la historia natural, geografía, agricultura, población y frutos del reyno de Valencia [Madrid: Imprenta Real, 1795–97], 1:110; photograph by University of Chicago Library, Special Collections Research Center)

On September 12, although the observations were not quite complete, his companions convinced him that he had to leave the Sierra de Espadán. He was emaciated and his fevers, though intermittent, were growing more intense. He agreed to be taken to the provincial capital of Castellón de la Plana, an eight-gated city of 11,000 inhabitants, a mile from the coast and the hometown of his new friend the Barón de la Puebla. He could see its solitary octagonal bell tower as he rode down through the fertile fields of sugarcane and hemp. Once in town, he checked himself into an inn. At first, his illness did not appear serious, but he passed a horrible night. Summoned by an urgent letter, young Dezauche rushed down from his station to join his expedition leader the next morning, just as the baron arrived from Valencia. Together, they transferred him to the baron’s local residence. There he passed his final days, recorded with vivid sympathy in Dezauche’s private journal.

FRIDAY, SEPTEMBER 14, 1804: I go to see Monsieur Méchain. I find him well enough, but very weak because he refuses to take anything, not even chicken broth, and has not eaten in eight days.

SATURDAY, SEPTEMBER 15, 1804: I go promptly in to see M. Méchain and find him quite well, even gay, but still very weak.

SUNDAY, SEPTEMBER 16, 1804: At nine in the morning, a servant begs me to come quickly to the baron’s. There, I learn that M. Méchain passed a horrific night, and that since morning his mind has been distracted. I go in to see him. He opens his eyes very wide but does not recognize me.

MONDAY, SEPTEMBER 17, 1804: At seven in the morning, I go to see M. Méchain. I find him in the grip of a violent fever, in delirium, his mind vacant, not knowing what he says or does. The people looking after him find it difficult to confine him to bed. At nine, two doctors arrive, neither of whom inspires much confidence. They prescribe cinchona. I write to his son to come immediately. The doctors return at noon, and again in the afternoon. The patient has been enervated by his morning outburst. The doctors agree that he has a nervous tertian fever, which does not mean much to me. They summon the baron and me into the antechamber to tell us that the fever has turned deadly and that they cannot answer for their patient surviving another attack that night. Then, to ease their conscience, they ask that M. Méchain be confessed. The news stuns me. When M. Méchain himself is sounded on this topic, he indicates that he does not feel as bad as all that. I spend all day with my patient, turning him to urinate, and carrying him to the toilet when he needs to use it. Having heard the likely course of his illness from the doctors, I resolve to spend all night with him, not wishing to leave him to the servants, who are country people and cannot understand him. Around four-thirty in the afternoon I find him much better. His mind is again clear, and his speech orderly. At nine at night I give him cinchona, at ten-thirty a broth, and so on in alternation until three in the morning. My patient is getting better and better. He has no fever but is still excessively tired. Finally, at six-thirty in the morning, I leave him in a good state and hand him over to the care of the baron.

TUESDAY, SEPTEMBER 18, 1804: At seven-thirty I return to M. Méchain; he is doing very poorly and has lost consciousness. Four doctors, whom I summon, all say he has malignant tertian fever. At noon they say he has an ardent fever. That night, I have him given extreme unction out of fear that he will die at any minute. Then the doctors apply the Spanish fly—a blistering agent—to the back of his head. They put a compress on each of his feet. I send for M. Lanusse, the French commercial attaché in Valencia, and ask him to bring a surgeon and some cinchona, since the supplies here are no good.

WEDNESDAY, SEPTEMBER 19, 1804: I spend all night awake, watching over my patient. He will not drink. He rejects any medicine as soon as it is given him. He is unconscious; his eyes, half-closed, are yellow, as is his complexion. At six in the morning, the doctors return to examine the patient. His arms are trembling and they decide he is apoplectic. He is still unconscious, his eyes open and vacant. He still refuses to swallow. At ten in the morning, they remove the blistering agent, which has taken well; the wounds are dressed with a poultice of pear leaves and honey. At noon, the doctor prescribes a febrifuge to reduce the nervous heat in his chest. He revives somewhat, enough so that when I say to him, “My dear friend, drink, it is for your own good,” he looks at me through half-opened eyes and parts his lips for me to feed him some cinchona on a spoon. At one o’clock, I am summoned for my own lunch, and with hope for his improvement, I go.

As soon as the meal is done I return to my patient. It is two o’clock. I am astonished. I find him in agony, with a very strong bronchial rattle, his eyes almost entirely shut, his mouth wide open, his tongue very dry, and in the grip of a fever worse than any yet. I immediately call the four doctors. They arrive and agree there is no further remedy; he is all but dead.

At ten o’clock at night, the baron, M. Lanusse, and I are in the antechamber, discussing what arrangements to make for the calamity that awaits us, when suddenly we see Augustin Méchain enter. He embraces us all in turn, me last, then asks where his father is. I tell him that he cannot see his father at present because he has been in a fever all day, and is exhausted now and resting. He repeats his request more emphatically, and I tell him again that it is impossible for him to see his father. At this, the unhappy young man throws himself onto a bed and cries: “Where is my father? My poor father! I want to see my father! Oh, I know what you’re up to: this is his bed, he lay here and now he’s dead. My poor father, I will never see you again!” We assure him that his father is not dead, only very sick. The young man wants to sleep in the house, but I insist that he goes to M. Bigne’s instead, and have the gentlemen escort him there.

I then return to the father’s sickroom. The doctors agree that there is not much time left, but to drag things out, they place a compress of hot wine on his stomach and occasionally moisten his lips and tongue with wine and water. That is our procedure for the rest of the night. At midnight, the death rattle ceases, his pulse fails, and at five in the morning, on Thursday, September 20, 1804, on the third complementary day of the year XII, he dies in my arms: I receive his final breath.

And so ends the life of one of Europe’s greatest talents, a man who was very good to me and who will be mourned by all Europe.


Augustin Méchain fell sick that night. Unable to sleep, he collapsed in the morning. His fever was slight, although he suffered from an attack of nerves that caused his legs to twitch uncontrollably. He sobbed in his bed. Later that day he had a still more violent attack, and it took five men to hold him down while he cried out for his father and mother. He subsided only after being bled from the arm. Dezauche stayed all that night in a cot beside the young man.

The funeral was the next morning. Dezauche put on his naval uniform. The cortège was led by the Provincial Governor, the Barón de la Puebla, and the members of the expedition, followed by Spanish nobles and military officers, French expatriates, and three hundred monks. The cortège was met under the carved portico of the cathedral by the wives of the nobles and expatriates, all dressed in mourning. After the Mass Méchain was buried in the cathedral’s cemetery—in a lead casing, in case the French government or his family ever wished to retrieve the body.

What eighteenth-century physicians called “tertian fever,” because the fever returned every third day, we today call malaria. The disease was endemic in Valencia, especially around the Albufera marshes, which Méchain had recently traversed. The ailment had been diagnosed since ancient times, and by the end of the seventeenth century physicians had discovered a palliative: an extract of the bark of the cinchona tree of South America. This is what they were giving Méchain. But the bark’s active ingredient, quinine, comprised less than one-sixtieth of cinchona, and hence the potion was not always as effective as it would be today.

In his final delirium, Méchain had obsessed over the fate of his mission—and his papers. During all his years of geodesic travels he had always carried his manuscripts with him in a trunk. These calculations, logbooks, and notes were the summation of a life of scientific labor. They were his continual point of reference, consulted and adjusted with each new insight. As Méchain was famously reluctant to publish his findings, these papers were all the more precious. No wonder, reasoned his subordinates, that he spoke of them so often during his final collapse.

Now that Méchain was dead, they had no choice but to abandon the mission and return home to Paris. However, they took special care to bring the manuscripts with them. They deposited some of the larger surveying instruments in Valencia for the use of his replacement (should the Bureau of Longitudes appoint one), then packed one portion of his papers for shipment back to Paris. Augustin took the rest with him on his mournful journey home.

News of Méchain’s death reached Paris on October 8. A few weeks later, Augustin himself arrived. Without hesitation he personally delivered the papers to Delambre, his father’s former partner. The remainder, sent by post, were handed over to Delambre by Madame Méchain some four months later. All told, they included several thousand pages of formulas, observations, and calculations, scribbled, revised, and rewritten. As Méchain’s scientific executor, Delambre had the task of going through those papers and salvaging what knowledge he could.

The rest of Méchain’s small collection of scientific books and instruments was quickly auctioned off. Neither son had any intention of pursuing a scientific career. And after what they had seen of their father’s fate, who could blame them? With her husband’s death, Madame Méchain was obliged to vacate her apartments in the Observatory. She took up residence in Paris’ ninth arrondissement on a modest pension. The Méchain scientific dynasty had lasted five short years.


Augustin Méchain composed a brief obituary for his father. He wrote of a man who had died “far from his country, his wife, and his old friends,” but who had found in his last moments “the consolation one expects from untainted love . . . in the arms of those who accompanied him.” “They bathed him in their tears,” he wrote, “they were his friends and did not blush to call him maître.” His father had possessed the qualities that mattered most. He was “virtuous, frank, affable, modest, a good husband, a good father, a good friend. He loved his country, his fellow man, and the arts. His friends and the sciences will deplore his loss and record his memory to the most remote period of posterity.”

In a still briefer obituary, Lalande spoke of the young man he had brought into astronomy, and who had died a martyr to that science.

These touching obituaries were followed by a grand eulogy from Delambre, delivered before the assembled Academy of Sciences, with the bereaved family in attendance. Delambre paid this tribute not just as Méchain’s partner, but in his capacity as Permanent Secretary. In a tradition dating back to the masterful orations of the seventeenth century, a scientific eulogy in those days was more than a recital of the technical achievements of the deceased; it was a secular sermon on the moral qualities of the natural philosopher, whose life, like his work, was permeated with the virtues of self-sacrifice, disinterestedness, and stoic candor. These were the virtues that enabled the savant to contribute to the accumulation of true knowledge, thereby serving both the nation and humanity, and making him worthy, like the statesman and the general, of immortal remembrance. A eulogy consoled a family, assured colleagues of the sanctity of their calling, and inspired the young to join their ranks. Making sense of death is the survivor’s privilege—and his burden.

Delambre recounted Méchain’s life as a tale of arduous labor and ultimate sacrifice, driven not by overblown ambition but by the obstinacy of service. Méchain came from a humble family, he reminded his audience, but had risen by dint of hard study. Patient observation and fastidious calculation had led him to discover eleven comets. These same qualities had earned him a role in the grand mission to measure the world. Delambre did not make Méchain’s labors appear glamorous; on the contrary, he emphasized their tediousness.

It was those same virtues that had enabled Méchain to complete his grand mission. Delambre walked his audience through the stations Méchain had traveled on his route to martyrdom: his arrest on his first day’s travel out of Paris, his stamina through the mountains of Catalonia, his fateful accident at the pumping station, his detention in blockaded Spain, his long struggle to return to France, his battles with the ignorant peasants who tore down his signals, his triumphant return to Paris—and then, when his life promised ease at long last, his self-sacrificing return to the field of his scientific labor. Delambre did not assert that Méchain’s achievement was due to his genius or intellectual creativity. No such claim was possible. Rather, he ascribed his success to a kind of obstinacy. It was Méchain’s obsession that had produced the most precise measurements in the history of astronomy. For proof, one need look no further than his repeated efforts to confirm his latitude measurements at Barcelona. “And never has a verification been more thorough, more satisfactory, and for just that reason, all the more superfluous.”

Delambre acknowledged that Méchain had occasionally seemed to tarry on his mission. At times he had been tempted to set aside his burden, overcome by a melancholy brought on in part by his injuries, in part by the grievous trauma that had befallen his nation. In his darkest moments Méchain had even contemplated emigration, so painful was the thought of returning to Paris, where several of his colleagues had met a terrible fate. Yet the same obstinacy that had propelled him to complete his mission had also driven him to return home to perfect his study. He was a martyr to the endless quest for precision, Delambre concluded, not because he sought personal glory, but out of modesty and fierce self-doubt. Méchain had always been dissatisfied with his own work, piling on new observations, adjusting his formulas, refining his calculations. As a result, he had avoided the finality of the printed page, even when it came to their joint labor on the meridian. “Never did he consider these observations, the most exact ever achieved in this domain and conducted with unsurpassed certainty and precision, never did he consider them sufficiently perfected—and so he worked continually to refine them.” This scrupulousness had long delayed the publication of the Base du système métrique. But now that all Méchain’s papers were in his hands, Delambre promised to prove a faithful guardian.

From this day forth, my most cherished occupation will be to extract from this archive everything that may contribute to the glory of a colleague with whom I was honorably bound in a long common labor. And if I have not succeeded today in painting a picture of the departed astronomer worthy of his merits and the feelings I have for him, I am at least certain that whatever I publish of his work will do far more for his memory than even the most eloquent oration.


It was a sincere and moving eulogy. While it glossed over certain embarrassing details, it was true to the dead man’s spirit. It read Méchain’s character as the source of both his triumphs and his limitations. The family expressed their gratitude, and at their request Delambre had his eulogy published so that they could distribute it to their friends. No one, however, reclaimed Méchain’s body and it remained in the cemetery of Castellón de la Plana.

In January 1806, the same month the eulogy appeared in print, the first volume of the Base du système métrique was also published. There Delambre paid even greater homage to his deceased partner by listing Méchain first as the expedition leader. The volume offered a lengthy preface laying out the history of the meridian expedition, followed by the record of all the triangulation data from Dunkerque to Mont-Jouy. It deferred the latitude measurements to the second volume.

But between his delivery of the eulogy and its appearance in print, in the gap between the writing of the first volume of the Base and its publication, Delambre made a discovery—a scandalous discovery. The publisher had been pressing Delambre to deliver the first volume of his book manuscript, and so he had postponed his examination of Méchain’s papers. Now, as he worked his way through them, he discovered the discrepancy between the latitude results for Barcelona and those for Mont-Jouy, and worse—far worse—a systematic effort to cover up that discrepancy, suppress observations, and rewrite scientific results. It was a discovery and it was a scandal, for while it clarified many of the mysteries that Delambre had delicately glossed over in his eulogy and in his preface to the Base, it also presented him with an acute dilemma. The platinum meter had been constructed; the metric system had been published and made law. The metal bar sat contentedly in its triple-locked box in the National Archives. The bar did not equal the meter; it was the meter. What did it now matter that the data that had gone into its making had been erroneous? What should Delambre reveal?

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