PARIS NOTES
November 2001
Volume 10 Issue 9
Disks and Dials
A mini-marathon traversing Paris to find 135 Arago meridian disks and 109 historical sundials
By Ethan Gilsdorf
"Where is that damned disk?" Isabelle cursed, her attention wavering after two hours of stooping, neck craning and obsessive list checking. "Wait, I got it." She pointed to the 12-centimeter copper, zinc and tin alloy medallion, sunk flush into the sidewalk.
Just because Paris missed its 2008 bid to Beijing doesn’t mean you can’t invent your own Olympic event. Or two. Consider entering the 6K systematic (or entirely idiosyncratic) search for the city’s 135 Arago disks, or hurdle both space and time in the 109-sundial dash. Athleticism takes a back seat to inquisitive fitness. If you don’t mind scrutinizing road surfaces and building facades, sweet-talking your way into private courtyards, and scratching your head in public—in short, looking like a weary, quest-laden marathoner—then go for the gold medal. Or bronze disk.
My wife Isabelle agreed to co-pilot the first leg of the biathlon, the connect-the-dots rally along the ground-breaking meridian, credited to François Arago (1786-1853), that slices the city from Montmartre to the Parc Montsouris, crossing the 2nd, 6th, 9th, 14th and 18th arrondissements. Earlier that morning, clearly overconfident, I had said, "With a compass, we’ll have this wrapped up in no time."
"You think?" Isabelle had wisely doubted. For while the Paris Meridian runs directly north-south through the city, hitting such landmarks as the Palais Royal and Louvre on its way through the length of France (from Dunkerque to Perpignan), she reminded me that Paris is laid out like 1,000 triangles of apple tart. This imaginary line that established France as the ground-zero reference for navigation hops and bores through cars, fences and buildings with ease, but for the hunter in hot pursuit, Paris’ charming plan becomes a pain in the comp-ass.
Arago’s career as both an astronomer and a politician was impressive—he helped outlaw slavery in the French colonies, for example. However, it turns out that he didn’t actually pencil-in the meridian idea. It was first determined in 1667 to orient the Paris Observatory, whose walls the meridian bisects (and whose construction contains no iron so as not to muddle compasses and other devices), to a perfect N-S-E-W axis. In 1718, Jean-Dominique Cassini drew out the line, which was later revised in 1739-40 and again in 1792-98. Arago’s contribution, while he was still a student at the Ecole Polytechnique in 1806, was to re-measure and extend the Paris Meridian all the way to Les Iles Baléares in Spain. After being held prisoner by pirates, Arago completed the operation in 1809, returning to Paris to be elected to the Académie des Sciences at the ripe old age of 23 and later, head of the Paris Observatory.
Unfortunately, the Observatory is closed to the public (except one Saturday a month), but the tranquil gardens out back reveal two disks, plus a few meters of the Arago line neatly delineated in brick. Crossing Boulevard Arago, just south of the Observatory, we found Place de l’Ile-de-Sein, where Arago’s statue once stood (it was melted down during World War II; today, only the base remains). Some kind of tribute was long overdue, so the government commissioned Dutch artist Jan Dibbets to design a conceptual monument to Arago. In 1984, 135 of Dibbets’ proposed 200 disks, emblazoned with an "N," "S" and "Arago," were glued into asphalt, cobble and cement, perplexing Parisians ever since.
Back to the quest. You can jump in anywhere; we actually began near the middle, finding our first disk of the day at the Institut de France on the Left Bank near the Pont des Arts. It can be a few yards or many blocks to the next disk: we proceeded down Rue de Seine (scoring six disks) to Boulevard Saint-Germain (where the next two are enshrined at numbers 152 and 125-127). Attention: the disks can be easily mistaken for gas and water manhole plates. Even armed with our official list of addresses, we couldn’t locate several. We saw suspicious-looking holes where the medallions should have been, evidence of vandalism, over-zealous souvenir hunters or absentminded street-paving crews. Alternately pleased and vexed, we continued by foot and bicycle, trying to tune into the vibe of the imaginary line.
Just before entering the Luxembourg Gardens, across the street from the disk near the Sénat at 26 Rue de Vaugirard, we discovered an interesting tangent. Under the colonnades, carved into marble, is one of the two remaining meter markers established as a standard measure in 1796-97. The only one still in its original location, the worn "yardstick" indirectly relates to Arago’s work: in 1799, the meter was measured as exactly one ten-millionth part of one quarter of the total length of the Paris meridian line that connects the city with the earth’s north and south poles. Nowadays, the meter is measured by an atomic device that’s more about time than distance. But more on clocks later. (Today, the Bureau of International Weights and Measures—BIPM—just outside of Paris, ensures worldwide uniformity of measurements.)
Our pursuit took us through the Luxembourg, where we batted 7-for-10, and through the south gate to the Jardin Marco Polo. We split up the territory: "I’ll cover this side of the street," said Isabelle, pedaling away. "You cover the other." Avenue Denfert-Rochereau and Avenue de l’Observatoire (six more) led to the Paris Observatory, the mother of the whole invention.
This is where space and time converge. The 19th-century advent of "fast" railroad travel and the telegraph required a rethink of both clocks and navigation. A battle between England and France ensued: would the world’s prime meridian split hairs at Greenwich or the Paris Observatory? Though France’s meridian was first, England won, persuading delegates at the International Meridian Conference in 1884 to move the zero-degree longitude mark to Greenwich. They agreed upon Greenwich Mean Time (GMT, today called Coordinated Universal Time, or UTC) and established the world’s first standard time zones. In 1891, the Observatory synchronized clocks throughout France relative to Paris only, snubbing its perennial enemy, and along with Ireland didn’t adopt the new worldwide "zero" until 1911. Greenwich ended the Paris Meridian’s geographical prominence, but the Observatory still plays an important role. Deep in its basement is the Bureau International de l’Heure (International Time Bureau), which keeps track of universal time. Meanwhile, BIPM is responsible for all kinds of terrestrial and space navigation standards, satellite orbits and such heady calculations as the velocity of the earth’s rotation.
As Isabelle and I continued, we became more clued into Arago’s and Dibbets’ tricks. Bing, bing, bing! Three in a row. We raced through Parc Montsouris (10 there; we located eight). A meteorological tower lies just off-target and a 13-foot obelisk called the Mire du Sud, erected in 1806, marks the then end-of-the-line (the Mire du Nord, now inaccessible in Montmartre, stakes out the other end). Across the Boulevard Jourdan, into the Cité Universitaire, we lost the markers entirely, and we seemed to have hit "the wall."
However, on the backside of the university’s abandoned, razor-wire-topped Cambodian pavilion, the Périphérique beltway whining beside us, we found the southern terminus, set into an unused sidewalk. In fact, all we found was the hole. Compared to the act of great imagination and abstraction uniting space and time that bisected the center of the Enlightenment (hence, City of Light), a thieved disk at the edge of Paris was neither a fitting conclusion to French geography’s ambition nor our incomplete quest. Our daily stats: 35 disks down, exactly 100 to go. Though pleased with our progress, Isabelle and I were feeling outdone by Arago. The remaining medallions would have to wait for another race of linear thought.
I had often spotted Arago disks in my quotidian travels around Paris, even when I had only a faint clue about their history. More difficult to stumble upon are Paris’ 109 sundials, typically set high on building facades or within private courtyards, their markings often worn, paint faded and hardware damaged or missing. I never noticed them, but in fact these timekeepers are common in the older arrondissements (3rd, 4th, 5th, 6th and 7th), relics from an age when clocks either did not exist or, as late as the early 1800s, when primitive clocks required constant resetting from a sundial. The oldest were created in the mid-1500s—the sundials on Eglise Saint-Eustache (Place René-Cassin, Les Halles, 1st) date to the 1530s—and they have been installed in Paris ever since. In 1966, Salvador Dali designed one with a scallop-shaped face and flaming eyes at 27 Rue Saint-Jacques, 5th.
Isabelle complained of a nagging "Arago neck" the next morning, so for the second event of the disks and dials biathlon, I entered the race as a solo competitor. For obvious reasons, the search for sundials is best done on a sunny day. But even amid typical Parisian gloom a fine time can be had snooping around both well-known and quieter streets, churches, museums, now-public mansions (hôtels) and private residences. Les Invalides (seven sundials), the Sorbonne (one), the Grand Galerie of the Louvre (one), Eglise Saint-Sulpice (three), the Cluny Museum (two), Jardin des Plantes (two), Palais Royal (one) and Palais de Justice (one) all offer easy-to-see sundials from the street or gardens and courtyards within.
Others require creative solutions: the gates to the Couvent de la Merci (45 Rue des Archives, 3rd) are typically closed, but from the back-facing window of an adjacent children’s clothing store called C’est Ma Chambre, one of two cadrans solaires pops into view (a magnificent father time with scythe). In search of another sundial, I waited for 20 minutes outside a locked door at number 46 Rue Faubourg-du-Temple (11th) until someone buzzed, allowing me to slip in and discover not only a fine 19th-century vertical sundial but a tranquil country-like lane suffused in greenery. Not that I’d ever advocate trespassing, let alone breaking and entering; when you’re spying on private property, it’s best to ask permission first.
Watches measure time as we would like it to be; sundials measure time as it is. Relying on shadows and motion, not the homogenized intervals of "watch time," sundials mark noon when the sun is highest in the sky. Clocks, on the other hand, will measure noon tomorrow exactly 24 hours later than noon today (although "high noon" actually falls several seconds earlier or later than 24 hours, depending on the time of year). When the telegraph and train arrived, it made no sense for each town in France (and Europe, for that matter) to retain its local time. Thus, time based on a local standard meridian, or Mean Time, was invented, with its artificial construct of identically long 24-hour days. When international standardized time was adopted relative to one meridian (Greenwich), local meridians like Paris’ were phased out and sundials were rendered obsolete.
But clocks weren’t an overnight success. In 1641, Louis XIV (the Sun King, of course) ordained that public clocks be adjusted according to the sun. Why were sundials more reliable" Because the earth rotates uniformly, and the sun appears to move uniformly across the sky. So a rod (called a gnomon) placed parallel to the earth’s axis will cast a shadow that moves through a 15-degree arc in one hour. Most sundials are based on this essential principle. The majority of sundials are "vertical declining," telling time dawn to dusk, but several I noticed, called meridians or meridional sundials, register only from 11am to 1pm and were used by Parisians specifically to calibrate their clocks at noontime.
During a challenge that took me through the 3rd, 4th and 11th one late afternoon, in about two hours I was able to find eight sundials (and would have found more had the Eglise Saint-Gervais-Saint-Protais not been covered in scaffolding). I began my journey near Bastille, where an easily accessible ivy and cobblestone passage at Cour de L’Etoile d’Or (75 Rue du Faubourg-Saint-Antoine, 11th) displays a roughly six-foot-square worn model etched into plaster, its gnomon rusted, amid faded lettering for a furniture business. I headed west across Bastille to the Hôtel de Sully (62 Rue Saint-Antoine, 4th), whose elegant garden is decorated with a simple moon and scrollwork sundial motif, carved directly into the building’s facade, as is typical. From there, it was not too far to 1 Boulevard Henri-IV on the Ile Saint-Louis, and its modern, more ornamental sundial visible from the street.
Once on Ile Saint-Louis, armed with my list, I realized that many of the best sundials remain hidden from public view. Hôtel de Lauzun and Hôtel Lambert, for example, are in private hands, and getting through the wooden doors was impossible. But at Hôtel Chenizot (51 Rue Saint-Louis-en-l’Ile) the door could be opened; within the courtyard was an 18th-century meridional with an unusual tripod gnomon. Even older sundials can be found not far off the island, near Eglise Saint-Gervais: a 17th-century circular sundial barely survives at the old Hôtel Noirat (corner of Rue de l’Hôtel-de-Ville and Rue des Barres).
I ventured into the 3rd arrondissement for my last three of the evening. Looking high on the facade perpendicular to the street, I saw mirror-image sundials mounted on adjacent buildings at 16 and 18 Rue des Quatre-Fils. A few blocks north, you cannot miss the relatively recent sundial at 18 Rue Perrée. Just above Square du Temple, this allegorical relief of flying birds, clouds and nymphs representing twilight and dawn stretches over five stories, proof that during the 20th century, the enshrinement of time reached epic proportions. Having reached the edge of the arrondissement and the end of sunshine, I called it a day.
An equally fulfilling itinerary could be designed for any Paris neighborhood shined upon by sundials (note: the 17th has none and the 2nd, 9th, 12th, 13th, 16th, 18th, 19th and 20th have but one apiece). Logically, clocks were often installed on the sites of old sundials, and experts estimate that as many as 175 of Paris’ oldest sundials have been lost. Unlike Arago disks, only about half of the remaining 109 are easily accessible to the public (the rest require some ingenuity or permission before giving themselves up). But that’s the thrill of the chase, to be taken in stride with the agony of defeat. Luckily, Arago disks and sundials are fairly set in their ways. Leading you into uncommon corners and concourses of Paris, they’ll exist to be checked off your list, this Olympic games or the next.