The Measure of All Things

by Ken Alder

  That winter, while Lavoisier languished in prison, the same forces closed in on Delambre’s patron, Geoffroy d’Assy, also a wealthy financier associated with the detested taxation system of the Ancien Régime. The neighborhood council in the Marais—renamed the Section de l’Homme Armé (the Armed Man)—sent two officials to search the d’Assy residence in Paris for evidence of disloyalty. When the house servants explained that the d’Assy family had relocated to the countryside, the officials sealed shut the residence at 1, rue de Paradis. Then on January 25, 1794—just as Delambre arrived at the d’Assy country château on his way north from Orléans—d’Assy was arrested there. No explanation was given, but in light of d’Assy’s position in the Ancien Régime, none was needed. A second search of the d’Assy residence in Paris a week later turned up a table lamp engraved with the fleurs-delys and made by an artisan who worked “by appointment to His Majesty.”

  It was up to Delambre to remove any further incriminating evidence from the house. After a week spent comforting the family in Bruyères, he drove his custom-built carriage back to Paris, paid a last month of wages to Bellet and his manservant Michel, returned his repeating circle to Lenoir’s workshop, and presented himself to the neighborhood council. He showed them his passport, signed by the Minister of the Interior, declaring his residence to be 1, rue de Paradis. He showed them the certificate attesting to his status as the Republic’s Commissioner for the Measure of the Meridian. And he explained to the council that he needed to gain access to the d’Assy residence to recover important astronomical equipment essential to his mission. Needless to say, he did not mention that he had been purged earlier that month from the meridian expedition for “lacking revolutionary zeal.”

  Delambre’s ostensible goal was to retrieve his own papers from his apartment on the third floor. He was accompanied by two officials. On entering his room, he discovered that his secretary-cabinet was locked and that he had forgotten the key. This enabled him to make a second trip inside the sealed building a month later. On the second occasion, the officials examined every scrap of paper he removed from the cabinet, including a piece of parchment covered with a Latin scrawl and signed by King George III of England. This document attested to Delambre’s membership as a foreign correspondent in the Royal Society of London. The officials seemed uneasy about this document, as well as several other sheets covered with scribbled calculations and drawings; these might be ciphers or secret plans. In the end, however, they let Delambre remove these papers, having found “nothing suspect.” He later recalled that “this was a supreme indulgence on their part for a man they thought in correspondence with kings.”

  Lavoisier was not so fortunate. He was executed on May 8, 1794, along with the twenty-seven other tax farmers. As one mathematician confided to Delambre: “It only took them an instant to cut off that head, and it is unlikely that a hundred years will suffice to produce a comparable one.”

  By that time Geoffroy d’Assy had spent five months in the Luxembourg prison. Initially, conditions were tolerable; prisoners had the use of a café in the prison’s central courtyard. But as war fever intensified, the Committee of Public Safety suppressed dissent by populists and moderates alike. That summer, the Revolutionary Tribunal sentenced d’Assy to death, along with fifty other coconspirators who had plotted a prison revolt to “reestablish the monarchy and tyrannical power.” A more motley set of conspirators could hardly be imagined: aristocrats, bakers, and an entire family. Only an elderly wine merchant and a fourteen-year-old boy escaped the death sentence—although the boy’s sixteen-year-old brother was executed. Two weeks later, Robespierre himself was guillotined during the counterrevolution of thermidor.

  The incarceration and death of Delambre’s patron made him now the chief protector of the d’Assy family. In June, he returned to the d’Assy home in Paris, armed with a power of attorney from Madame d’Assy, to retrieve various legal documents belonging to the family. In January 1795 he petitioned to recover all his own possessions from the house, including his astronomical equipment, his furniture, and a small portrait of himself on the dressing table of Madame d’Assy. He spent the rest of this period far from Paris in the d’Assy country château near Bruyères-le-Châtel, then renamed Bruyères-Libre. When Madame d’Assy’s brother died of a fever later that year, Delambre promised to shed tears for him as soon as he had a spare moment. At the time the tragedies were coming too fast.

  The Revolution had provided the French savants with a unique chance to rewrite the world’s measures. Yet the opportunity carried corresponding risks. Persist in the old ways of treating your subordinates and they might take you down a peg. Place your talents in the service of the state, and the state might call you to account for your findings. Commit an astronomical error, and you might wind up in prison.

  Most of the purged members of the Commission had sequestered themselves in the countryside during the long hot summer that became known as the Terror. Borda retired to his family estate. Laplace retreated with his wife and two young children to Melun, thirty miles southeast of Paris. But Cassini IV’s residence was the Paris Observatory, and he now paid the price of having refused to serve the Republic. In the decade before the Revolution, Cassini had hired three men as astronomical aides and housed them on the Observatory grounds, where they might be instructed by Méchain and the rest of the staff. These apprentice astronomers now demanded equality with their boss, as well as the other rights of free men. The eldest, a mild fifty-year-old monk named Nicolas-Antoine Nouet, who also served as Observatory chaplain, informed Cassini that he wished to marry his personal serving woman. Cassini was horrified and the two men, once cordial, never spoke again. The second student, a young man of astronomical talent named Jean Perny, returned drunk to the Observatory late one night after a meeting of his Revolutionary club, and banged on his patron’s door with the butt of his sword, shouting “Cassini the aristocrat must be killed!” He had to be subdued and taken to bed. A few days later he penned an abject letter of apology. The third student, Alexandre Ruelle, a youthful deserter from a dragoon regiment, whom Cassini had harbored and trained until his amnesty came through, became his benefactor’s most bitter enemy.

  The apprentices’ complaint was the perennial complaint of junior scientists in the laboratories of their seniors: they accused Cassini of having appropriated their work to publish it under his own name. They wanted equal credit and equal pay. The “horrific despotism,” of the Observatory director, they claimed, had “stolen the fruits of their nighttime labor.” In truth, Cassini had generally acknowledged his students’ contribution in his reports to the Academy, albeit in a patronizing manner.

  In this topsy-turvy time, however, the assistants made their accusations stick. With the aid of a sympathetic politician, they reorganized the Observatory along egalitarian lines. Science, after all, was a democratic enterprise, open to all aspirants. No savant should inherit his position like an aristocratic title. The government created four new posts of “Observatory Professor.” Cassini retained one of these. But rather than give the other three to the country’s leading astronomers—Lalande, Delambre, and Méchain—the apprentices convinced the authorities that these savants harbored “aristocratic” sympathies, and had themselves appointed instead. Cassini’s salary was halved, and Perny was elected the first director in rotation. Faced with this humiliation, Cassini resigned, ending 120 years of family rule. His resignation only worsened his situation. His students were able to evict him from his apartments in the Observatory. Then the government seized his map of France, the family’s great commercial and scientific enterprise and, when Cassini dared to protest this theft, threw him in prison. Immediately, his student Ruelle, a member of the neighborhood’s Revolutionary council, suggested that his former protector be sent before the Revolutionary Tribunal, a certain death sentence. Mercifully, the council rejected his suggestion.

  But topsy-turvy times will flip and flip again. Once Robespierre himself had fallen from powe
r, the student-professors fell out among themselves. Suddenly Ruelle found himself under attack by his fellow students. Apparently he had committed an error of ten seconds in a solar observation. More damaging still, his results were fraudulent, based on theoretical guesswork, rather than on direct observation as he had claimed. For this crime against science—and also, of course, for his affiliation with the radical party now out of favor—Ruelle was himself imprisoned on August 22. Such were the risks of scientific error in perilous times. To replace him, the other two former students invited Delambre to join them as Observatory Professor.

  Thus the winds of revolution shifted in science as they did in politics. Robespierre’s Republican successors, self-conscious moderates, made a great show of reviving the nation’s scientific institutions. In June 1795 they established a new institution, the Bureau of Longitudes, in imitation of Britain’s Board of Longitudes, to help France rival that nation’s commercial and naval dominance. The Bureau supervised the Observatory of Paris, and was staffed by the nation’s finest savants, including Lalande, Laplace, Legendre, and Borda, plus Delambre and Méchain. Then they restored the Academy of Sciences as part of the new National Institute, where almost all the (surviving) academicians—Delambre and Méchain included—resumed their old chairs.

  Now it was Cassini who was free, while Ruelle languished in prison—though neither found scientific redemption. When Ruelle was finally released, only Lalande would vouch for him, and he finished his career at the national lottery, where one hopes he did not indulge the sort of fabrications that had cost him his career in astronomy. As for Cassini, he spurned the entreaties of Delambre and Lalande that he rejoin the scientific fold. He said he had witnessed too many bitter divisions in the Academy to contemplate a return. He retreated to his country château in Thury with his mother, his five children, and nine nuns evicted from a nearby convent. “My swallows,” he called them. “I have named it the Republic of Thury,” he wrote, “where I assure you we lack only Republicans.” The savant who had once claimed the meridian expedition as his birthright no longer believed in the metric reform—nor even in science.

  “But what of your astronomy?” you ask. I confess, it is nothing to me now. . . . “But,” you ask, “does not your glory, your reputation, your duty as a savant all speak against this retreat?” My friend, the duty of a father surpasses that of an academician. . . . And as for my reputation, my glory, I have sacrificed them, and it has cost me little. . . . Obliged to flee the Observatory, I saw the Academy of Sciences delivered to the government of the sans-culottes. And what grieved me most, I saw the savants themselves up in arms, divided against one another, partaking of the delirium and the rage of the Revolutionary horde, adopting their morals, their manners, and even their language. . . . How can I recognize myself in the changes they have wrought in our old ways of calculating, our old measures, when we had not ten hours in a day, but twenty-four, and no circles of four hundred degrees . . . ? Everything has changed, and I am too old to abandon my old habits and ideas. The year, the months, the almanac, the astronomical tables, all are changed. If Galileo, Newton, or Kepler were to descend from heaven and appear at the Academy, they would not comprehend a word in the presentation of Citizen Lalande when he told them that on 20 brumaire, the moon, in a 200 degree opposition to the sun, passed the meridian at 5 hours. . . .”

  Peasants, shopkeepers, and villagers were not the only ones attached to the old numbers of the Ancien Régime. To the numerate, numbers matter. Some old-time savants, like Cassini, considered the metric system an affront to the harmonious values that had once described their universe.

  But where Cassini retreated, Citizen Lalande advanced. On May 17, 1795, he became the new Director of the Observatory. Throughout the advances and reversals of the Revolution, the great iconoclast remained unbowed. When he was elected to the head of the Collège de France in 1791, his first official act was to admit women to all classes. He ended the announcement of prizes in Latin. He even tried to get professors to teach their own courses. Every evening, rain or shine, he took his long constitutional through the streets of Paris—sometimes walking for five or six miles—handing out alms. With his purple waistcoat and his umbrella (a newfangled invention), he cut a singular figure on the city streets: under five feet tall, unkempt, unwashed, his thick gray hair matted to the back of his eggplant-shaped skull. Yet shameless men can demonstrate great courage. “I am so constituted,” he reflected, “as to fear no thing nor person, neither danger nor death.” It may have been his philosophe’s vanity, yet he always insisted on speaking the truth. “I am frank to the point of rudeness; I have never dissimulated, even when the truth might displease.” He had spoken his mind during the Ancien Régime, and he refused to quit now.

  He later admitted that it was probably his notorious reputation as an atheist that saved his life during the Terror. If so, it was the only time his irreligion found favor with the powers that be. “I don’t feel sorry for the nuns who lose their pensions because they refuse to swear allegiance to the state,” he wrote to his daughter. “It ought to be a joy for them to starve to death for God.” Yet he proved to be an ecumenical savior. He hid the monarchist Du Pont de Nemours in the dome of his observatory in the Collège des Quatre-Nations, and brought him food and drink there for several weeks at the risk of his own life. Years later, at Lalande’s funeral, the founder of the Du Pont Corporation asked God to bless the notorious atheist. Lalande also disguised several condemned priests as astronomers for their protection, telling them not to worry about this deception. “But of course you are astronomers; who can better claim that title than men who live for heaven?” At a time when it was risky to do so, Lalande also published laudatory eulogies of guillotined savants such as Lavoisier—and then quibbled with their scientific views.

  His finest moment was the inaugural Festival of the Supreme Being, where he helped celebrate the deity of the ersatz religion Robespierre had hoped to substitute for Christianity. The ceremony took place on June 8, 1794, inside the Panthéon, a year after Delambre had observed the Paris triangles from its cupola. Offered at last a pulpit to preach his atheism and denounce the priestly cabal, Lalande instead seized the occasion to warn against the ferocious patriotism of the times.

  The time has come to declare these important and incontestable truths, known to all people, at all times, and in every corner of the globe: love of country, love of virtue, and the reign of reason. . . . Love of country is not a patriot’s only duty; charity is also a duty. We cannot all serve our nation in the army, in the state, in the arts and sciences, but we can all come to the aid of our brothers. . . . It is in this way that charity, added to love of country, will make us truly worthy of our Revolution, our victories, and the admiration of the entire Universe.

  But however great his love for his nation or his fellow man—and woman!—Lalande’s highest priority was always his stars. A few days after his Festival address, he announced he had added 1,200 new stars to his catalogue in the past ten days, bringing his total to 21,000. Six months later—during which time Robespierre was deposed and the moderates took power—he added another thousand. He refused to serve on a criminal jury lest it distract him from astronomy. “There is no sanction,” he informed the authorities, “which would make me leave my stars; I would do anything rather than defer to your summons.” Sometime in 1796, the family workshop surpassed their initial goal of 30,000 stars and decided to shoot for 50,000. His daughter continued to calculate “with a courage rare for her age and sex.” Her young son Isaac was placed in childcare because he so distracted his mother and grandfather. When Lalande hit 41,000 stars in 1797, he boasted that “this inventory of the heavens has been my constant project for the past twenty years, and occupies me to the point that I could die without regret, knowing that I have left behind a monument of my passage here on earth.”

  All this time, Delambre had quietly been plying his astronomical trade at the d’Assy country château at Bruyères. To be on the
safe side, he secured a certificate from the local municipal council attesting to the fact that he was not an émigré, and had never been imprisoned. Mostly he stayed out of the public eye. On only one occasion did the Jacobin government call upon his expert advice: Delambre had detected a flaw in the new Republican calendar.

  In their efforts to keep the autumnal equinox aligned with the birthday of the Republic, the calendar’s designers had instituted the franciade, a leap-year day. But they had failed to see that it would not fall every four years as intended, but occasionally in the fifth year instead. A perfect alignment of Republic and nature was not a simple matter. Looking 150 years into the future, for instance, Delambre discovered a year in which it would be impossible to predict whether the equinox would occur before or after midnight on September 22. He brought these prognostications to Lalande, who informed the calendar’s principal author, Romme, who in turn asked Delambre to help resolve the problem. Delambre suggested some possible solutions, although he warned that certain inconsistencies would resurface 36,000 years hence. When Romme presented these modifications to the relevant government committee, they pronounced themselves unconcerned. “Do you want us to legislate eternity?” one member wanted to know. No, Romme responded, he would be satisfied if the committee agreed to revisit the issue in 36,000 years. And so, to general amusement, it was decreed. Romme himself would not live to see another year, however. He was arrested and executed for his Jacobin sympathies two months later.

  By then France’s military conquests—thanks to its Jacobin-led armies—had inspired a new sponsor of geodesy. In 1794, General Etienne-Nicolas Calon was appointed Director of the Dépôt de la Guerre et de la Marine, thereby uniting the army and navy cartographers under a single command. Calon dreamed of a detailed geographic survey to extend the Cassini map to France’s newly conquered territories in the Low Countries, Germany, and Italy. He was a perpetual enthusiast, a self-promoting military cartographer, now a brigadier general and a member of the national legislature. More to the point, he had the budget to make things happen. He envisaged a “museum of geography” assembling forty-five of the nation’s leading savants in an effort “to raise to the highest possible degree the development and glory of the astronomical and geographical sciences.” The spine of this geographical knowledge would be a precise geodetic survey of the meridian.