Follow the imaginary line

I noticed the first one on the rue de Vaugirard, right in front of the Snat. A bronze disc about five inches in diameter embedded in the paving stones, embossed with the single word Arago and, above and below it, the letters N and S.

When I spotted a second one behind the Louvre's glass pyramid, I was intrigued. And a little research sent me off on a most enjoyable Parisian treasure hunt, following the Paris Meridian.

Centuries before the international conference that established Greenwich as prime meridian, the Paris Meridian was serving French navigators as zero degree longitude. Franois Arago, who traced part of its route, was honored for his achievements with a statue in front of the Paris Observatory.

When that monument was melted down during World War II, an empty pedestal was all that remained until the early 1990s, when Dutch artist Jan Dibbets won a competition for a new memorial. His unconventional "monument" consists of 135 circular bronze plaques sunk into the sidewalks, courtyards, and floors of the north-south axis of Paris.

Fired by a desire to follow its route, I set out, starting where the meridian had, at the observatory. A handsome building with parklike lawns and a famous fountain, it is open to the public only for guided tours. But Arago's statue had stood just south of it, and there on the Place de l'Ile-de-Sein, I found its pedestal, now adorned with a plaque.

Several more plaques dotted the sidewalk near it, and when I turned toward the observatory I saw the meridian itself - in the form of a line of marked stones cutting across the south lawn and straight into the building. The meridian, in fact, bisects the observatory, whose walls are oriented to the four points of the compass.

The institution was built in 1667 to improve France's sailing charts, navigational prowess, and sea power. The astronomers' first task was to establish the Paris Meridian, an imaginary line they projected from the center of the observatory toward the north and south poles. Once its trajectory was determined, first through Paris, then France and beyond, cartographers could refer to it as zero-degree longitude.

An ambitious walker could follow the meridian through Paris in one lengthy hike - the city limits are roughly formed by the circular Priphrique highway, and within that boundary the meridian stretches 5-1/2 miles.

Starting from the north, the route climbs the hill of Montmartre, descends into Place Pigalle, crosses the heart of Paris through the Louvre and Luxembourg Garden, and ends just south of the Parc Montsouris.

I preferred to do it in several leisurely walks, rather than one day, discovering new areas of Paris and revisiting familiar ones along the way. It wasn't easy - the meridian may be straight but the streets are anything but.

And I didn't find them all. Some are on private property, many have been stolen, and others are inaccessible because of construction.

One of my favorite treks was plaque-hunting on the steep streets of Montmartre, through quiet, lace-curtained residential areas I would never have seen otherwise. The "Butte," a tangle of trees and wisteria-draped terraces, is still crowned with two of the 30 windmills it once supported. One of them, the Moulin de la Galette, is located near the Mire du Nord, an obelisk used as the northern bearing during the meridian's creation. Although the Mire is off-limits to the public, several plaques are visible nearby, at 45/47 avenue Junot, 15 rue Simon-Dereure, and 79 rue Lepic.

You can see the Mire du Nord's counterpart, the Mire du Sud, in the Parc Montsouris, a park filled with young mothers and babies, elders in berets, and students lounging on sunny lawns. The Mire, at the park's southern edge, is a 13-foot stone obelisk dated 1806, with a partially obliterated inscription meaning "In the reign of" (Napoleon's name has been removed).

I found three plaques among the pink and white chestnut blossoms scattered on the park's paths, two more a few steps away on boulevard Jourdan, and five on the university campus across the street.

In upscale St.-Germain, the meridian cuts through the colorful rue de Buci street market. Tempted by creamy Camemberts, tiny fraises des bois (wild strawberries), and the aroma of chickens sizzling on rosemary-garnished spits, I strayed from my path. But I eventually rejoined it to find two plaques on boulevard St.-Germain, at numbers 125/127 and 152, and another on the corner of the rue de Seine and rue des Beaux-Arts.

Across the river near rue St.-Honor, the Palais Royal shelters seven plaques under its arcades, where the meridian slices through a corner of the Comdie Franaise. Addresses can't help you here, but once you spot a plaque in the passage between the Caf de Nemours and the theater, line yourself up with its north and south indicators, draw an imaginary line, and follow it to the others.

Like any worthwhile quest, mine was full of the unexpected. While I searched for a plaque in a largely immigrant northern quartier, a woman laden with shopping bags insisted on helping me find what I'd "lost."

Covering the whole length of Paris, I realized how brilliant Jan Dibbet's design was. By creating a monument that uses the entire city as its scale, he not only gave me a new perspective on Paris, but showed me the meaning of a meridian. Arago would have been proud.

(c) Copyright 2000. The Christian Science Publishing Society