by Ken Alder
Delambre responded to this plea with a lengthy letter, the core of which he had already read to a public session of the Academy of Sciences. As he explained to Méchain (and to the Academy), he had not observed the four additional stars Méchain had sighted at Barcelona because each presented disqualifying difficulties. The star known as Capricornus only came into position during daylight; it might be observed in Barcelona, but not in gray Dunkerque. The star Mizar, which had caused Méchain so much anxiety, passed too low on the horizon to be observed with confidence on the North Sea coast. And so on. Delambre declared himself satisfied with only the two stars. “Indeed, these are perhaps the only stars a savant ought to observe if he wishes to seek the certainty he needs, rather than to foster doubts.”
A public paper for the Academy is not the same as a letter to a colleague. So Delambre appended a personal note for Méchain. He lauded Méchain’s superior skills at observation, his ability to pick out faint stars that eluded others. “I could never claim to compete with you.” As for Méchain’s doubts about refraction, he assured his colleague that the problem was not worrisome. None of Méchain’s data suggested that the correction for refraction should differ at different latitudes. All their colleagues—Borda included—agreed that Bradley’s tables were inaccurate, and that Méchain’s Mont-Jouy data should be considered definitive, “the most perfect that could be hoped for.” By general acclamation, he told Méchain, his Paris colleagues had declared the astronomical portion of their mission complete. “That task is done,” he said.
Two savants defer to one other. Each denies he is competing. Each concedes the other’s superiority. Yet the same phrases in different mouths have different meanings. Delambre’s formulas rang with self-assurance. Méchain’s formulas quivered with self-doubt. The formulas of polite society—like the formulas of nature—can convey a great variety of meanings.
Delambre appended a final postscript. He informed Méchain that he would be dining two nights hence in the company of Madame Méchain, and hoped that he would likewise embrace his colleague soon. Méchain was missed in Paris, and he would find a warm welcome there. The new Academy was just like the old one; the new Bureau of Longitudes was staffed by their dearest colleagues. The government—now called the Directory—was still dealing with the aftershocks of Revolution and hoped to stabilize the currency by creating a new paper money called mandats. Delambre himself had arrived in the capital just in time to witness the suppression of the “conspiracy of equals,” a revolt led by Gracchus Babeuf, his old political sparring partner from Amiens. Currently he was assembling funds to resume his triangles to the south of Bourges. By midsummer he expected to be back on mission, advancing rapidly toward Méchain.
All this time, Méchain had been stalled in the mountains outside Perpignan, struggling to advance a few triangles north. The region was in turmoil. French soldiers, back from their Spanish conquests (bargained away by the diplomats), were being billeted in every spare room in town. Prices were soaring. The 24,000 assignats supplied by Calon fetched less than 800 francs in hard currency; a month later they were worth half as much. Not even Méchain’s parsimony could keep pace. His team members could barely afford their daily pound of bread and half pound of meat. Wine and any other “succor” had to be paid for out of their own pockets. Conditions were even worse in the mountains, where his assistants were setting up signals for observation. Villagers would not accept assignats at any price. No one would rent them horses or mules. The equipment had to be carried on foot, and porters were demanding wages of 100 francs a day. The workmen who built the signals expected still more. The bill for the two masonry pyramids that Méchain proposed as markers for the ends of the baseline near Perpignan came to 24,000 francs, his entire budget for the year.
To help out, Tranchot offered to transfer his three years of back pay to the expedition budget. This calculated generosity meant that Tranchot’s daily expenditures had to come out of general funds. To cope with inflation, the Bureau of Longitudes multiplied its pay scale eighteenfold that winter. But even Méchain’s astronomical salary of 144,000 francs (in assignats) did not match the inflation rate. If the Republican government had wanted to teach its people that price was the paramount variable, they could hardly have picked a more painful lesson plan. It was the world’s first experience of hyperinflation. Méchain noted that he and his collaborators would have died of hunger in the mountains without the hard currency he had put away from the sale of his repeating circle, “and that’s no jeremiad, but the truth.”
Tranchot’s first task was to reestablish the frontier signals, destroyed by two years of warfare. He revisited Puig d’Estella, where he had been ambushed by miquelets two years before. He replaced the signals at Mont Bugarach and Forceral. Meanwhile, Méchain assured General Calon of his determination. “Never believe, Citizen, that I am disposed to abandon the mission; I will exhaust every resource.”
Among those resources was his physical stamina, diminished by his accident but unexpectedly robust. Méchain decided not to reclaim his customized carriage, stored in Perpignan these past three years. The terrain was too rough for carriage travel, and horses were prohibitively expensive. He headed into the mountains on foot, alone. The assistants Calon had sent him were more trouble than help. With only one circle, he had nothing for them to do; so he sent them back to Paris—all except Tranchot. He did have one guiding light, however: Cassini’s triangles of 1740. The problem was that Méchain was trying to operate at a level of precision that was itself a kind of uncharted country.
The first stations around Perpignan were relatively benign. The summit of Mont Forceral, a barren cone-shaped hill to the immediate west of the town, overlooked a spectacular panorama of dusty vineyards, salt lagoons, and the Mediterranean coast. Méchain slept under the stars there because he could not afford a guardian to watch over the circle at night. Mont d’Espira, to the immediate north, stands in the foothills of the Corbières range, where the terrain became more forbidding—a landscape of stony valleys dominated by ruined castles. In the interior of this range stands an isolated, twin-peaked mountain, used in Cassini’s 1740 survey, and which Méchain would use as well: Mont Bugarach, known in local dialect as the Pech de Bugarach.
The Pech de Bugarach nearly broke Méchain’s spirit. This enormous limestone rock was considered sacred by the inhabitants of the valley. The town at its foot sheltered eight hundred inhabitants, a general store, three water mills, and a nearby mine that produced jet, a dense black coal that the locals fashioned into jewelry. Méchain had hoped to camp on the summit, but the twelve-foot-wide peak could not accommodate both his signal and his tent. So he lodged in a farm on the mountain’s flank and tackled the two-hour climb every day, scrambling up the slope on his hands and knees, hanging onto shrubs and dwarf trees for balance, then sidestepping his way warily across the bare rock of the final ascent, while loose pebbles underfoot rattled into the abyss below. One misstep and all was lost. He could cite a “thousand examples” of men who had plunged to their death, he informed Lalande. But at least he climbed unencumbered. “I trembled with fear for the men who carried the case for the circle and the timbers for the signal.”
Nothing would induce these men to repeat the performance. They also refused to guard the instruments overnight, or to sit watch over them during the day. The shark’s-tooth summit was scoured by fearsome winds. The new signal was the third on the site. A violent storm a month earlier had destroyed the signal Tranchot had built to replace the one he had built two years before. The place was precarious. Villagers spoke of the sinagries, spirits whose malevolent glance was enough to strike men dead.
Even today, a zone of mystery surrounds the mountain. The name Bugarach derives from Arabic, and means either “father of all rocks” or “the banished father,” signifying a high place where exiles are sent to die. The mountain still attracts mystics, who believe it to be the navel of the world, or a place extraterrestrials will one day land, or a crypt for ancie
nt gods and suppressed human memories. It is a stiff climb to the top. From the farmhouse where Méchain lodged, a climber in a hurry needs nearly two hours to reach the peak. Above the pasturelands, the trail takes a series of switchback turns through a steep scrub of beech trees and mineral springs. The earth is clinging and heavy. After the vegetation clears, the trail passes through a cleft in the twin-toothed peak for the final ascent to the summit. At the top, if the atmosphere is still clear, one can see the cool blue curtain of the Pyrénées drawn across the far southern horizon, and nearer in, a half-dozen ruined fortresses at strategic intervals along the receding ridges, their broken ramparts an extension of the broken hills. To the north, guarding the broad green trough that runs from the Atlantic to the Mediterranean, the citadel of Carcassonne, Méchain’s destination, is barely visible. Yet such clear days are an exception. In the old Occitan dialect of the local shepherds:
Quand Lauro porto cinto
et Bugarach mantelino
Aben pleijo sur l’esquino
When Mount Lauro wears his belt
and Mount Bugarach his cloak
Then it rains on the slopes
Imagine what it was like, Méchain asked Lalande, to set out on a clear morning and reach the top only to find that the surrounding signals had been obscured. Clouds advanced like armies between the ridges, or they flew in at a high altitude, smothering the entire region and lingering for days. Méchain slept in the farmhouse, and every day he had to climb the mountain to check his circle, left unguarded on the summit. Every morning he reassembled it for observations. Every evening he packed it back in its case and secured it under an oilcloth weighted down by stones, with only the sinagries to watch over it at night.
Then, when the weather cleared, Méchain saw a full panorama, including a view of the trail of his ascent. He could trace it back with his eye as it traversed the steep ridge, slipped through the rocky saddle, then emerged on the other side, before plunging into the tangled brush. It was the trail of his immediate past—and his future—the only way up or down the mountain. From the peak, time stretched out before him, like the view toward Carcassonne. Already it was late October. Each series on the repeating circle took an hour, and he needed a dozen series. The wind was cold. The clouds were closing in—then, just like that, his future was obscured.
This was not the sort of life he had envisaged when he took up astronomy. Astronomers are generally sedentary folk. They keep odd hours, to be sure: midnight vigils and predawn discoveries. But after a certain age they stay put and trade information by mail. In the ceremonious days of the Ancien Régime Méchain had held a sinecure as capitaine-concierge of the Royal Observatory. Until his survey across the English Channel in 1788, he had never left the dense soil of northern France. The Ancien Régime had been the fixed backdrop against which time advanced, like a fine chronometer. Every night he had strolled across the midnight gardens of the Observatory to the starry roof, and every dawn he had returned to his neat little house. But the Revolution had broken time, reset the clocks, and torn down the calendars, filling the days with events so rapid he could no longer hear the beat of the pendulum clock. The Revolution had cast him out into the periphery, where time had slowed to a crawl and his days were filled with repetitive ado. Now he slept in decrepit inns in provincial towns: the pork roasted to a chip, the servants always late, no parlor to write in, chairs that defied all notion of rest, doors that gave windy music as well as entrance, whitewashed walls, and tapestries so old as to be a “fit [nest] for moths and spiders.” When he was lucky he slept in the manor houses of the local gentry, or even better, in the homes of amateur savants, such as the Arago household in Estagel near Perpignan. When he was unlucky, he slept in the straw of an up-country cowshed, without candlelight to verify his calculations, or in a windy tent on an icy summit.
Yet he lived in an age when voyagers had approached the ends of the world, returning with sperm whale oil from Antarctic shores, breadfruit from Tahitian Edens, and visions of the Northern Lights. What glory was there then in traversing France, a nation which tens of thousands of ordinary French men and women crossed every year, only to bring back some numbers? One might just as well ask what challenge Thoreau faced in his two years at Walden Pond while tens of thousands of ordinary Americans braved a savage frontier a thousand miles west. For the men of Paris, their nation’s interior was a foreign land, as exotic in its way as any Andean highland. The people of the central provinces did not speak French, but a gamut of Occitan dialects more closely allied to Catalan or Provençal. The village mayor might understand French, but he would not speak it. The local measures enclosed each village in its own economy. The challenge was not whether France could be traversed, but how, by whom, and to what end. Shepherds might herd their flocks to up-country slopes. Brigands might hide in the mountains. Only a man of science would climb a peak to prove a point.
Ten days later, when Bugarach was done, Méchain moved to Mont Alaric, just as a storm knocked down the adjacent signal at Tauch. Tranchot was sent to repair it. Then it was Tauch’s turn. By the time he had finished with Tauch it was late December and bitterly cold. He had climbed each mountaintop station fifteen or twenty times, and each had required some eighty miles of travel through snow-covered fields over ice an inch thick, while violent northwest winds blew. The grease in the repeating circle clotted in the cold. His fingers were too numb to tighten the screws. And despite his efforts he had only extended his arc from Perpignan to Carcassonne, laying down three pitiful triangles in six months.
This might have been an opportunity for him to return to Paris for some much needed rest with his family. Certainly none of his colleagues would have begrudged him a break during the geodetic off-season. But Méchain had once again decided to winter in the south. He told Calon he wanted to choose a site for his baseline, a place he might best measure one of the sides of his triangles from end to end. For this, he needed a straight stretch of level terrain at least five miles long, whose terminal points could be triangulated from a nearby station. In 1740 Cassini had used the beach near Perpignan, but Méchain considered the shifting sands there too unstable. Instead, he picked a segment of the Grande Route that ran from Perpignan to the fortress of Salses. Tranchot directed the army engineers to build a masonry pyramid at each terminus, and Méchain linked them by triangulation to his station at Mont d’Espira. He also wanted to conduct the actual baseline measurement right then and there—Tranchot even assayed a preliminary run with a surveyor’s chain—but his colleagues in Paris insisted that he finish his geodetic angle-measurements first. The baseline measurement would have to be postponed until the special equipment could be prepared in Paris.
Méchain took this refusal to mean that his colleagues did not trust him. His spirits, after a temporary respite, had darkened. In March he admitted to Lalande that “my strength no longer matches my courage.” The cold weather had aggravated the old injury to his arm, but he himself admitted that the accident’s long-term effect had been more mental than physical. He was despondent, and did not quite know why. “All that remains now is to cure my head. I will make every effort. I still have hopes that I will conquer the apathy and lethargy that alienate me from my true self, and that chill my spirit the moment I am at rest or alone with myself, enervating the few faculties I ever had.” His melancholy had begun to overwhelm him. He felt paralyzed.
Then, in the next breath, he wrote to Delambre to offer to triangulate north of Rodez onto his partner’s side of the arc. The extra work would not strain him, he said, but simply allow him to make up for his inadequacies and balance their respective contributions. Delambre never answered this request. Spring came and went. The summer slipped away. Méchain remained in Perpignan taking latitude measurements.
Friendly bureaucrats there let him set up his observatory in the courtyard garden of the district office, where he also constructed a sundial. These measurements were doubly superfluous. The triangles, the baseline measurements, and the lat
itudes of Dunkerque and Barcelona were all that was needed to calculate the meter. But recently Borda, Laplace, and the other physicists on the Commission of Weights and Measures had decided that a series of intermediate latitude measurements along the arc would fine-tune their knowledge of the curvature of the earth, and hence improve the final extrapolation from the French meridian to the whole. They asked the two expedition leaders to gather this additional latitude data at three other sites: in Paris, within Delambre’s arc; in Evaux, at the halfway point of the meridian arc; and in Carcassonne, within Méchain’s arc. And they urged Méchain to join Delambre in Evaux to take the supplementary latitude measurements there together.
Méchain declined. He thought it best that Delambre measure alone at Evaux. That would ensure, he said, the accuracy of the latitude. “I know all too well that my results are far inferior to yours with regard to their exactitude!”
This remark, conveyed to Borda, prompted a sharp rebuke. This was no way for a self-respecting man of science to talk. When Méchain denigrated himself, he denigrated the mission. Borda set aside the usual courtesies and spoke frankly to the astronomer. The commander’s advanced age, his eminence, and his regard for Méchain gave him the right. “I have good cause to be angry with you,” he wrote. “Where did you get the notion that Delambre’s results, either for the latitude or the triangulation, are better than yours? Why do you deprecate your own work—or rather, the Commission’s work—when everyone else finds it excellent?” The discordant data for Mizar simply proved that Bradley’s old refraction tables were inadequate. If Méchain’s results did not match Cassini’s findings of 1740, then it was “tough luck for them.” “You were not sent out to find the same results as your predecessors,” he reminded Méchain, “but to find the truth.” Armed as he was with superior instruments, and thanks to the precautions he had taken in light of his mission’s supreme importance, his new results would undoubtedly differ from the old. If not, the entire mission would hardly have been worth the effort. In the meantime, Borda would use Méchain’s results to derive a new formula for refraction.