The Measure of All Things

by Ken Alder

  Two years later, the metric system itself was withdrawn. The Revolutionary calendar was the first to go, its own creators delivering the coup de grâce. Rather than knit the world together, the calendar had only isolated France. Even in France, it was universally ignored. Parisians still celebrated January 1, and the ten-day working week had proved curiously unpopular. Napoleon Bonaparte had another objection; he wanted Catholic legitimacy for his new régime, and the Church wanted its Sundays and saint’s days back. Shortly after he was crowned Emperor he asked his Senate to reconsider the reform. Pierre-Simon Laplace, kicked upstairs to become Senator for life, agreed that the calendar should be abolished—for its scientific flaws, he said. At midnight on 10 nivôse of the year XIV, the date in France reverted to January 1, 1806.

  The rest of the metric revolution did not last much longer. Since 1801 the metric system (shorn of its classical prefixes) had served as the nation’s official system of measurement—without changing the shopping habits of French men and women. The imperial government exhorted its subjects to do better; it supervised the annual production of 300,000 metric rulers; it commanded its police to punish scofflaws; and it printed detailed instructions on the proper way to dole out wheat, firewood, wine, olive oil, and the countless other commodities that were still being shipped in Ancien Régime containers. Yet Napoleon’s administrators watched helplessly as trading continued in the old units. Again and again they found themselves denying rumors that the government was on the verge of revoking the metric system.

  The rumors were true. In 1805 the French savants, led by Senator Laplace and Secretary Delambre, lobbied against further dilution of the metric system as an affront to the rational administration of France. The Minister of the Interior, a chemist, helped his colleagues hold off the day of reckoning. Five years later, when the system came under renewed attack, the academicians took a different tack; now they praised Napoleon’s imperial conquests, arguing that they offered a unique chance to disseminate a universal metrical language. Senator Laplace took this appeal directly to the Emperor himself, pleading with his former examination pupil to retain the decimal division, even bowing so low as to suggest that the measures be renamed the “Napoleonic measures” if it would help. It did not.

  With preparations underway for his invasion of Russia, Napoleon decided to minimize economic turmoil at home. On February 12, 1812, France adopted the so-called “ordinary measures.” The empire’s legal standard would still be defined in relation to the platinum Archive Meter, but the workaday measures would approximate those of Ancien Régime Paris. Length, for instance, would be measured in a toise (fathom) two meters long and divided as before into 6 pieds (feet) of 12 pouces (inches) each. In principle the system of decimal weights and measures would still be taught in the nation’s schools and used for public works and wholesale transactions. In practice, however, Napoleon had revoked yet another Revolutionary achievement.

  The goal was now imperial uniformity, pure and simple. Napoleon had no patience for the Revolutionary fantasy that a new language for the objects of the material world would create an autonomous and egalitarian citizenry able to calculate its own best interest. Instead, he grasped at central rule. All the other elements of the metric system were discarded to achieve that single goal. Among the few French intellectuals brave enough to decry this act was Benjamin Constant.

  The conquerors of our times, peoples or princes, want their empire to possess a unified surface over which the arrogant eye of power can wander without encountering any inequality which hurts or limits its view. The same code of law, the same measures, the same rules, and if we could gradually get there, the same language; that is what is proclaimed as the perfection of the social organization. . . . [T]he great slogan of the day is uniformity.

  This was the tragic lesson of the past twenty years. This was the prospective measure of the world. Where absolutist régimes had once been satisfied with the outward show of homogeneity, modern dictators aspired to inner uniformity, leveling any difference that interfered with allegiance to the whole. Condorcet, the dead optimist of liberation, had naïvely imagined a world in which universal law, derived from nature’s truth, could produce equality and freedom without contradiction. Constant, the living pessimist of liberation, had witnessed how uniformity, enforced by mass mobilization, could suppress difference of thought and custom. Both men, of course, were right. Their aspirations and fears remain the two poles of the axis around which the modern world still revolves. And both underestimated just how difficult it would be, for good or ill, to realize that uniformity.

  Such a formidable goal lay beyond even Napoleon’s grasp. Across the Empire his “ordinary measures” were rejected, just as the metric system had been. To the people of the annexed territories, the measures were just another attempt to coax them into a unified Continental economic bloc. In Rotterdam, where a prodigious commerce flowed down the Rhine, citizens ignored broadsheets converting Dutch to French measures. The Imperial Prefect there despaired of “the character of the inhabitants, and the notions they have about the new measures.” But back in Paris, the Minister of the Interior was not surprised; he knew firsthand the tenacity with which the common people—French or Dutch—defended their particular ways of doing things.

  Failure stirs resentment. Defeat embitters allies. From his exile in remote Saint Helena, Napoleon slandered his former colleagues for foisting the metric system upon him—and upon the French people. “It was not enough for them to make forty million people happy,” he sneered, “they wanted to sign up the whole universe.” The savants had wanted to overturn every custom, rewrite every rule, remake every French citizen into an image of themselves, and all for the sake of a miserable abstraction. They had behaved like foreign conquerors, he said, “demanding, with raised rod, obedience in all things, without regard to the interests of the vanquished.”

  Delambre accepted the collapse of Napoleon’s Empire—and the demise of the metric system—with equanimity. He had faith in the long run of history. As the coalition armies entered Paris in the spring of 1814, he was at his desk working.

  On the day of the siege, in spite of the cannonade audible in my study, I worked peacefully from eight in the morning until midnight. I was confident that the army would not be so foolhardy as to defend the town long, and would open their gates to the allies, who, piqued with pride, would comport themselves with generosity. Some days afterwards I saw foreign troops crowd onto the quays of Paris, pass under my window, and fill the streets and boulevards. . . . The future does not offer a bright prospect for savants, but they should know how to content themselves with little. My savings will assure my own independence, and my wife’s small fortune offers a still more reliable resource. You know my needs are simple. Work occupies all my time and all my faculties. My happiness does not depend on having a little more comfort; and I do not expect that I will have to change my personal habits.

  The fall of the Empire cost Delambre several of his positions and three quarters of his salary. He did not regret their loss, though he had to change residence again, this time to 10, rue du Dragon, convenient to the Academy’s new home in the Collège des Quatre-Nations. Besides, Louis XVIII had reappointed him to the position that mattered most: Permanent Secretary of the renamed Royal Academy of Sciences. And he retained his chair at the Collège de France and his post at the Bureau of Longitudes. As he explained to the new royalist administration, his fellow astronomers had kept their noses out of politics; they ought not to be shunted aside just because the régime had changed. Their political neutrality (some might say their political submissiveness) entitled scientists to keep their posts.

  More and more, Delambre concentrated his attention on the past. The obligations of the present had already made him an accomplished historian. In a sense, he had been preparing for this labor all his life. He had spent his youth indoors, hiding his eyes from the sun, studying ancient and modern languages. He had spent his scientific career poring over old t
exts, combing the work of dead astronomers for data to compare with his own. (In that respect, every astronomer is something of a historian.) Since becoming Permanent Secretary, he had composed eulogies, reports on his colleagues’ accomplishments, plus a Report to the Emperor on the progress made by science during the past two decades. Even his preparation of the Base du système métrique had involved historical reconstruction.

  He now dedicated his final years to a comprehensive history of astronomy “from Hipparchus and Ptolemy to us.” One by one, in chronological order, he would pass each astronomer, ancient and modern, through the filter of current knowledge, extricating their genuine contributions from the ephemeral speculations of their age so that, as Delambre put it, his own Treatise on Astronomy would cap the whole. It was a six-volume, 4,000-page scientific-extraction machine, and it was the first great history of science.

  His theme was the rise of precision: the relentless drive for exactitude. His method was empirical: a close reading of original works. Delambre sharply criticized those historians who had conjured up an antique people whose comprehensive astronomy had since been lost. There was no evidence of such a people. Nor did he agree with his colleagues who believed that the ancient Egyptians had derived their system of weights and measures from the size of the earth. Delambre had taken great interest in the French geodesers’ trip up the Nile, but he rejected their conclusions. Their pyramid studies had unjustifiably projected current fantasies onto the past.

  The historian’s great duty was impartiality, and impartiality began at home. Thus, in his article on Descartes—France’s greatest savant—Delambre adopted a sharply critical tone. “The historian owes the dead nothing but the truth,” he wrote. “It is not our fault if in astronomy Descartes produced only chimeras.” And he proceeded to document just how often in his physics Descartes had violated his own norms for clear and consistent evidence. By ignoring this evidence Descartes’ many admirers had “cast a kind of ridicule upon the French nation by reviving the memory of the very errors they sought to hide behind the veil of official secrecy.” In the history of science, as in science proper, progress was only possible with the forthright acknowledgment of error.

  How fitting, then, that one of Delambre’s last acts as Permanent Secretary was to superintend Descartes’ reburial—and to determine whether they had buried the right man. One hundred fifty years earlier the great philosopher had died in self-imposed exile in Sweden, but his body had been exhumed and returned to France soon after. Since that time his remains had been buried in a church, exhumed again, and then transferred to an Egyptian-style sarcophagus for storage in a national museum during the Revolution (alongside the royal statuary from the basilica of Saint-Denis) while politicians debated whether he was worthy of being panthéonized. By 1819 the Panthéon had been reconsecrated as a Catholic church, Voltaire and Rousseau’s tombs had been shunted aside, and the motto “AUX GRANDS HOMMES, LA PATRIE RECONNAISSANTE” had been covered over by scaffolding. Descartes, it was decided, would be better off re-reburied in the church of Saint-Germain-des-Prés. Delambre watched as they opened the sarcophagus and removed the small interior case engraved “René Descartes, 1596–1650.” Inside, there was not much to see. “Only the femur was recognizable; the rest had been reduced more or less to dust.”

  Imagine everyone’s horror then, when two years later, Sweden sent France a precious gift: the skull of its greatest genius, Descartes. Had a horrible error been committed? Had the wrong man been buried? It was another discrepancy to resolve. The Permanent Secretary was seventy-two years old by then, and in failing health. Yet he marshaled the documentary and forensic evidence, and adjudicated the matter with the same rigor he had brought to science and history. The gift skull, he concluded, was fake; the authentic skull of Descartes was presumably dust. After the physical evidence was gone, only inference remained. That would have to be enough.

  That year Delambre made careful preparations for his own death. He knew all too well what historians are capable of. He destroyed the bulk of his personal papers. He also set aside his correspondents’ letters so that his wife might inquire after his death whether they wished to have them returned, lest their confidences fall into indelicate hands. He also composed a short manuscript autobiography, which later became the basis for the biography published by his student and scientific executor Claude-Louis Mathieu, and thus (as he knew it would be) the basis for all subsequent biographies.

  All this was part of a conscious strategy. He was acutely aware that he would one day become the subject of historical investigation. And he did what he could—within the bounds of honesty—to shape that story. Thus, he planted the clues to the true story of the metric system in plain sight, publicly announcing that the logbooks of the meridian expedition were on file in the archives of the Observatory. He did not destroy Méchain’s letters, but placed them under seal in the archives. He made it possible for historians to tell a story that he could not tell in his own lifetime.

  Jean-Baptiste-Joseph Delambre died at home, at 10, rue du Dragon, at ten o’clock in the evening on August 19, 1822. The Permanent Secretary was buried in the Père-Lachaise cemetery so that a new Permanent Secretary might live. Jean-Baptiste-Joseph Fourier’s first eulogy paid homage to his predecessor. This was not a eulogy by an Ancien Régime savant but a speech by a modern scientist intent on glorifying science. Fourier puffed up the meridian project with exclamation marks: he called it the greatest application of science in living memory—yet he gave all his data in the old units of measurement, the law of the land in Restoration France.

  History is made by the dead as well as the living. Their obsessions perch like fetishes upon our mantels and upon our consciences. Science likes to think of itself as the one human endeavor free of idolatry. It imagines that it erases the past each time new knowledge sweeps the mantel clean. But the errors of the past can shape the direction of science as much as its truths.

  Delambre left the sixth and final volume of his comprehensive history of astronomy unpublished at the time of his death. He warned his friends that The History of Astronomy in the Eighteenth Century would tell “the whole truth.” If they found some of its judgments severe, they should remember that history was no eulogy. He had written the book, he said, to “discharge my conscience.” Perhaps for that reason he profiled only dead astronomers and delayed publication until his own death. Mathieu, Delambre’s student, shepherded those pages into print five years later.

  Among the final astronomers to be discussed was Pierre-François-André Méchain. This was no eulogy. Delambre had learned a great deal about his former colleague since his funeral oration seventeen years before. So he began at the beginning: there was no evidence for the story that Méchain had made his start in astronomy by selling his telescope to Lalande to pay off his father’s debts. He reassessed his colleague’s career: Méchain had never been a scientific innovator and had borrowed all Delambre’s formulas for his calculation of the meridian. He hedged on the exact date when Méchain departed for Barcelona: delays in the making of the instruments, Delambre now said, meant that the operation “could not commence” until June 25, 1792—which is not the same thing as saying that Méchain actually left Paris on June 25. He reapportioned credit for the grand mission: Tranchot deserved full recognition for his work. (The engineer had died in 1815 while triangulating at Montlhéry, the station just south of Paris where Delambre had begun his survey thirty years earlier.) He revisited the discrepancy at Barcelona: Méchain’s “fatal decision” to conceal the 3.24-second gap in the latitudes had made a mystery of what any other astronomer would have frankly acknowledged. And he supplied further revelations: Madame Méchain had been obliged to coax the astronomer to finish the mission; Méchain had refused to return to Paris until promised the directorship of the Observatory; Méchain had hidden his data from the Commission and obstinately clung to the notion of returning to Spain; Méchain had kept his secret intact until his papers were brought back to Paris.


  Yet, after all this, Delambre still considered Méchain a man “admirable in every way,” and assured his readers that they could have confidence in the meridian the two men had jointly measured.

  No one can claim to have known Méchain in his capacity as an astronomer better than I. For ten years we maintained an intensive correspondence. I long had his papers in my hands, and made a careful study of them, going so far as to revisit every calculation which bore upon our mission. In this way, I assured myself that Méchain, enamored above all by exactitude, but also very jealous of his reputation, had the misfortune to believe that the repeating circle could produce a degree of agreement and precision which was, in truth, impossible. When his observations presented unexpected anomalies, instead of reconsidering this view, he began to doubt his own abilities. Indeed, he feared that his own (unjust) opinion of himself would come to be shared by others, and would eventually overshadow his reputation. But this was not to be, and he remains an astronomer forever worthy of our admiration.

  Delambre had left one more manuscript unpublished. In The Size and Shape of the Earth, he carried the history of geodesy up to his own day. In it, he rectified Méchain’s suppressed observations so as to “release ourselves from the obligation to disclose the falsehoods to which we had, in some sense, been made complicit.” Yet he also recorded them to console those geodesers who would follow in the path that he and his partner had marked out, and thereby “disabuse them of the chimera of perfection, which mankind has yet to achieve and will probably never achieve.” These revelations were considered impolitic by Mathieu, then campaigning to revive the metric system. Not until 1912 did an edition of this work find its way into print. It was at that time that the sealed letters between Delambre and Méchain were opened in the archives of the Observatory, where they lay unread for the rest of the twentieth century.