by Ken Alder
In pursuit of this goal, Calon decided to consult the learned savant Jean-Baptiste-Joseph Delambre, initiator of the meridian survey. Unfortunately, he did not know in which prison to seek the savant. He asked Lenoir to locate the right facility, and was pleased to learn that Delambre was residing comfortably in a country manor. He invited the savant to Paris to plan a resumption of the expedition, and petitioned the Committee of Public Safety to re-engage both Delambre and Méchain to that end.
Soon afterwards, under the impetus of Representative Prieur de la Côte-d’Or, the National Convention passed the law of 18 germinal III (April 7, 1795). This law represented the final evolution of the metric system as we know it today. It provided the final set of prefixes and names that comprise the metric nomenclature. The new law also signaled some retreats from the principle of rationalization. Although the Revolutionary calendar was preserved, the decimalization of the hours was abandoned, ostensibly because of the cost of replacing all the nation’s clocks, and because the decimalization of time would help only astronomers, not ordinary citizens. Prieur also recognized that the transition to the new measures would have to proceed more “gently.” To oversee the process he created a Temporary Agency of Weights and Measures under the leadership of the gifted mathematician Legendre. He also decided that the meter would be introduced in Paris first, and set a target date three months in the future so that merchants and customers could prepare themselves. The rest of the country would follow later.
The new law also formally relaunched the meridian expedition. Prieur set aside his preference for a quick, cheap standard, and praised the “rightly celebrated” savants he had purged from the project eighteen months before. For the meter to become a truly international standard, he now noted, it had to be based on something grander than the fifty-year-old Cassini survey used to define the provisional meter. He urged Delambre and Méchain to recommence their survey “as soon as possible.” Any further delay was inimical to the public good. He even authorized the savants to approach him directly should they encounter the least obstacle. “I will endeavor with assiduousness,” he wrote to Delambre, “to prove to you my zeal for the success of your mission.” Prieur had good reason to demonstrate his good will; he was himself under suspicion for having allied himself too closely with the Jacobins during the Terror. Delambre smiled inwardly at this switch. As he noted to Méchain, “I would have accomplished a lot more last winter had I not been in the bad graces of Robespierre and one of his colleagues—whose name I’ll tell you later—and who has since treated me more favorably.”
Delambre had learned a thing or two about state-sponsored research in the intervening years. This time, before setting out on his expedition, he made a few requests. Even a savant could learn to calculate as other men did. “It is true that until now the astronomers charged with this mission have been unstinting in their efforts and parsimonious in their expenditures, such as one might expect from impecunious savants who spare the Republic every expense as if the costs were their own. They have neither requested nor received any payment for their labor.” Now, however, the expedition leaders deserved a salary like any other citizens employed by the state, plus back pay for the twenty-one months of geodetic work done before the Academy had been shut. In May 1795, after he and Calon agreed on terms, Delambre rejoined the Commission of Weights and Measures.
On June 28, 1795, Delambre left Paris in his custom-built carriage after an eighteen-month hiatus, accompanied as before by his manservant Michel and the instrument-maker Bellet, plus a new assistant to keep the logbook. The team provisioned their carriage for an extended journey, including thirty pounds of axle grease, a set of ropes and pulleys to hoist the repeating circle into church towers, two crates of astronomical texts, plus tools for repairs: borax, copper, mercury, oil, nails, and steel for screws and springs.
Their first night south of the city, the team put up in the d’Assy country château, where Delambre was always welcome. Two days later, they arrived in Orléans on the banks of the Loire, where Delambre had been forced to halt his operations eighteen months before. Three days later, they pulled into the cathedral town of Bourges, which was to serve as their base of operations while they worked their way back north toward Orléans. The team took lodgings at an inn known as the Coeur de Boeuf, located just off the square where a Liberty tree stood. By sighting from the inn to the nearby cathedral Delambre verified that the expedition team of 1740 had lodged in the same inn. Thus trigonometry informed history. The meridian expedition was back in business.
Bourges cathedral is a jewel of Gothic architecture. Above the front portal, the archangel Gabriel weighs the souls of the dead on Judgment Day. Inside, the stained-glass scenes of redemption rise in blue panels like an interior heaven. The town had served as an entrepôt for Renaissance finance, the central town of France’s Centre. But the sixteenth-century wars of religion had ravaged the region, and Huguenot zealots had decapitated the statues of the apostles in the cathedral. More recently, local revolutionaries had beheaded the copper effigies of the Duc and Duchesse de Berry, and turned the building over to the worship of the Supreme Being “who likewise rules from on high.”
The cathedral tower dominated the countryside for thirty miles around and more. It was 396 steps up the hexagonal stairwell to the platform two hundred feet above the pavement, itself at the summit of the hilltop town. In one corner of the platform, a filigree iron bell tower rose twenty feet further still; at its peak turned a weathervane in the form of a pelican. The selfless metallic bird, a symbol of Christ’s devotion, pierced its own breast for blood to feed its young. It would serve as Delambre’s signal, the point he would observe from afar. Beyond the low balustrade the rolling plain of patchwork farmland, dotted with small towns, stretched into the vaporous distance. Out there was his destination, if he could ever leave Bourges.
VIEW FROM BOURGES CATHEDRAL
This view from the top of the tower of Bourges Cathedral shows its pelican weathervane, unique in France, which Delambre used as his sighting target. In medieval legend, the pelican fed its young with blood plucked from its breast, and hence served as a symbol of Christ’s sacrifice. (Photograph from Valoire-Blois, France)
Delambre had left behind the noise and violence of Paris; yet even in this pastoral center, the retreating tide of Revolution threatened to suck him under. No sooner had he arrived in Bourges than the expedition stalled. The cost of travel had risen beyond his means. Inflation had gathered a frightening momentum since the fall of Robespierre. In the earliest days of the Revolution, the legislature had created a paper money called assignats to pay off the national debt (itself one of the principal causes of the Revolution), backing its value with the sale of confiscated church lands and the property of émigrés. This paper currency had always been treated with skepticism in the countryside, and the war had set off a first round of price increases. The Committee of Public Safety had tried to contain the escalation with wage and price controls. But the moderates had decided to lift the controls and print more money. The value of the assignats began to plummet with alarming speed. Delambre’s expense book documents the accelerating price of food, lodgings, and transportation as he traveled away from Paris. At each successive post, the cost of rented horses doubled and doubled again. The first stage out of Paris cost 92 francs; the last stage to arrive in Bourges a week later cost 804 francs. A few months later, the cost of a stage had doubled again to 1,400 francs. As the price of ink, paper, and basic foodstuffs soared, so did the cost of repairing church towers, erecting scaffolding, and building observation stations. Even the gratuity for the stableboys had risen by a factor of ten. Within a few weeks Delambre had spent his entire budget for the campaign season. He pleaded with General Calon for more funds. Without hard currency, he would be stuck in Bourges for the entire summer.
Nearly a month passed before Calon came through with the money. The Treasury would only release assignats, even though provincials would accept nothing but hard cu
rrency. To compensate, Calon raised the men’s salary (reduced to a pittance by inflation), and awarded them military rank: Delambre, Méchain, and Tranchot became captains. This entitled them to food rations. The challenge was to get the peasants and innkeepers to accept the army’s coupons.
Money was not the only obstacle. Geography also presented a challenge. The mournful region between Orléans and Bourges—triste (dreary) Sologne—was one of France’s most level. Where the expedition had once battled suspicious peasants and northern fogs, they now confronted a marshy terrain almost impossible to survey. The green ponds, tall grasses, and patchy forests offered few views into the distance. The rare church steeples were hard to make out through the mists: the steeple at Salbris, used by the surveyors of 1740, had been incinerated by a lightning strike; elsewhere, the Revolution had taken its toll. Delambre expressed his disappointment. “The sans-culottes have destroyed half the steeples in the Bourges region for ‘daring insolently to rise above the height of their humble cottages.’ ” It took Delambre three trips up and down the region to select a chain of workable triangles.
The villages of the Sologne are as isolated today as they were before the region’s swamps were drained. Ponds collect seepage, ditches surround farms, and ruler-straight roads run between twin rows of plane trees. The whine of an occasional motorbike only emphasizes the quiet. The churches are locked year round and are badly in need of repair. The area is depopulated, the number of priests dwindling. In the eighteenth century, the region was already known as the nation’s Siberia. Sandy soil, barren heaths, and thick swamps made even subsistence agriculture burdensome. “There is no soil more unyielding and painful to labor in all the world,” said the locals. Peasants rarely owned their own land. The cattle were sickly, the sheep weak. The ponds bred “Sologne fever” (probably malaria), which afflicted the villages each autumn. And on top of this, the people were beset by a plethora of taxes.
Such a climate bred suspicion. Certain families were said to have the power to bring storms upon their enemies. Sorcerers gathered before dawn at ponds like Boisgibault to beat the waters with great sticks and shout horrible cries. “It was enough for them to seek to change the weather and the blue sky would cloud over and the thunder rumble.” To clear away the fogs and evil vapors required holy incantation and the continual ringing of church bells, called the dindon. The curés had to stuff cotton in their ears to withstand the continual pealing.
The church in Vouzon dates from the sixteenth century and the bell in the square tower used by Delambre still tolls the hours, although the rest of the edifice burned down in the 1880s. At Souesme the church tower has been rebuilt since Delambre’s day, and is covered with scaffolding in anticipation of further repairs. The octagonal Sainte-Montaine belfry still stands, dwarfed by a venerable chestnut tree. Luckily for Delambre, when he visited the site in November the tree was bare of foliage and he could make out the surrounding signals between the branches.
Where no steeple was available Delambre paid locals to build him an observation tower. At Oizon, he had a twenty-two-foot signal built in the form of a pyramid, which he covered with planks of wood painted white. At Ennorde, he had a twenty-four-foot pyramid built, which he then had transported to the middle of a hummocky wheat field. At Morogues, northeast of Bourges, he had a twenty-five-foot signal erected beside a road as it crested a small hillock. Delambre and Bellet climbed the scaffolding and perched themselves on bales of hay to sight the surrounding stations. At Méri-es-bois, just north of Bourges, an elderly villager led them to the ruins of the signal post used in the survey of 1740, and assured Delambre that he remembered Cassini’s passage through town fifty-five years earlier, but that some local lads had torn down the signal last year as a sign of “feudalism.” All this activity attracted unwanted attention.
Even those with the best notion of who we were, took us to be prisoners of war being transported from place to place. Others, on seeing the crates for our circles, took us for charlatan salesmen and refused to give us lodging. That’s what happened in Vouzon. At Souesme, we were also refused a place at the inn; but that was because they knew who we were, and knew we only had assignats to pay them. Without the help of the municipal council, who promised to compensate with grain anyone who sold us bread, we would not have been able to procure any food. Even so we passed several days with nothing to eat but bread. . . . Not only that, but an epidemic was then sweeping through Vouzon, and one of my collaborators fell sufficiently ill that we had to leave him behind when we left the town for Chaumont.
Triste Sologne took Delambre several months to measure, and proved the least accurate sector of the entire survey because the triangles could not be evenly spaced. By working well past the optimal season for geodetic measurement, however, he managed to complete the chain of triangles between Bourges and Orléans by late November. He planned to use the winter—otherwise impractical for geodesy—to conduct his astronomical measurements at Dunkerque and determine the latitude of the northern extremity of the meridian arc, the counterpoint to the measurements Méchain had already conducted at Mont-Jouy.
So before leaving Orléans for Dunkerque Delambre composed a letter to his distant colleague. This letter renewed their correspondence after a two-year silence. Delambre was pleased to be back in touch with his colleague: he was eager to trade information about data, funding, and personal matters too. There was one thing in particular he wished to know. As Méchain had already performed the latitude measurements at the southern end of the arc in Mont-Jouy—and with such precision—might he advise Delambre as to which stars he had observed, what methods he had used to measure their height, and what precautions he had taken against the possibility of error? This information would ensure that his own results could be most fruitfully compared with the superb results Méchain had already achieved.
No innocent request could have touched so sensitive a nerve in so sensitive a man as Pierre-François-André Méchain.
CHAPTER SIX
Fear of France
Must it be ever thus—that the source of happiness must also be the fountain of our misery? The rich and ardent feeling which filled my heart with a love of Nature, overwhelmed me with a torrent of delight, and brought all paradise before me, has now become an insupportable torment—a demon which perpetually pursues me.
—JOHANN WOLFGANG VON GOETHE, The Sorrows of Young Werther
Upon leaving Barcelona harbor Méchain’s precious repeating circles had been blasted by a bolt of lightning, and no sooner had he sailed within sight of neutral Genoa than an English frigate blockaded his vessel and forced her eighty miles south to the port of Leghorn (Livorno in Italian), where he and his fellow expedition members were placed in quarantine while customs officials threatened to impound his instruments.
Was ever a natural philosopher so beset by misfortune? Storms of fate, both natural and man-made, had forced him from the narrow meridian where his duty lay, and if the calamities of war and the frailties of his body were not enough to drive any man, even a natural philosopher, to helpless despair, these multiple woes were compounded by the knowledge of his own mistake, greater because it was self-inflicted, greater still because it was unrectified, and greatest of all because it was secret. A stoic natural philosopher might have coped with headstrong Revolutionaries, capricious generals, mischievous nature, and violent machinery; but the error for which he blamed himself was more than enough to plunge a sentimental natural philosopher—such as he—into a most profound melancholy.
Méchain was a stranger in Livorno, without acquaintances there. He could expect no help from his wife and colleagues in distant Paris; any letter to them would have to travel over the Alps, across battle lines, and through the thick of Revolutionary chaos. So, from the local lazaret—the compound where goods and visitors waited out their obligatory ten-day quarantine—he wrote to the director of the astronomical observatory in the nearby university town of Pisa, ten miles north in Tuscany.
Méchain co
uld claim no prior acquaintance with Giuseppe Slop de Cadenburg. But the Pisan had long been a regular correspondent of Méchain’s maître Lalande and had also assisted the French navy with its Mediterranean maps, Méchain’s task for much of the past twenty-two years. They also shared a fascination with comets. So although they had neither met nor corresponded, the two men knew one another by reputation, always a savant’s most precious possession. As a scientific colleague, Méchain importuned Monsieur Slop to use his credit with the local authorities to get his instruments through customs. In return, he would visit Pisa upon his release to express his gratitude in person, and also to demonstrate the new astronomical repeating circle, should the Pisan wish to examine the most advanced scientific instrument of the day. The device was not contraband, and as his mission served the general good, it ought to be protected by all nations. “When war divides people,” Méchain wrote to Slop, “science and the love of the arts must reunite them.”
Such an eloquent plea and collegial connection was sufficient to unite two astronomers wherever they met. Slop sent an associate in Livorno to assist “the famous Méchain,” introducing him to top officials and negotiating the various payments—which some might call bribes—to clear his instruments through customs. A grateful Méchain arrived at the astronomer’s house in Pisa on June 22, 1794, the day of the summer solstice. He stayed for three weeks.