17-Jun-2023 -- Special visit
Méridien de Paris
48°49'52"N 2°20'11"E

Introduction

Before the Greenwich meridian was adopted as the prime meridian, the Paris meridian had been the prime meridian for French cartographers and most seafaring countries since 1668. It started from the Paris observatory, commissioned by Louis XIV, and over the years had been measured and re-measured by triangulation, first from Dunkerque to Barcelona, and later through the Mediteranean and Algeria. By extrapolating these measurements, the distance from pole to equator was calculated, and shortly after the French revolution in 1789, the meter was defined as one ten-millionth of the length of the Paris meridian.

With the dominance of Britain as a seafaring power in the 19th century, the Greenwich meridian became more important, and in 1884, at the International Meridian Conference in Washington DC, the Greenwich meridian was adopted as the prime meridian of the world. This in the vain hope that Britain would accede to the Metre Convention. The French on their part clung to the Paris meridian as a rival to Greenwich until 1911 for timekeeping purposes and 1914 for navigation.

Arago

One of the scientists carrying out the triangulations for the Paris meridian was François Arago. Apart from his geodetic work he also worked in the field of astronomy, civil engineering, meteorology, optics, (electro) magnetism, politics, and he was appointed director of the Paris observatory in 1830. In 1893, 40 years after his death, he got a statue just outside the observatory garden on the Place de l'Île de Sein, located on the Paris meridian, of course! Unfortunately during WW2 the bronze statue was removed by the Germans, and transformed into something they found more useful in wartime. So now only the pedestal with his name is left (picture #3).

But in 1994 the Arago Association and the city of Paris commissioned a Dutch conceptual artist, Jan Dibbets, to create a memorial to Arago. Dibbets came up with the idea of setting 135 bronze medallions into the ground along the Paris meridian: "an imaginary monument on an imaginary line". Each medallion is 12 cm in diameter and marked with the name ARAGO plus N and S pointers. You can find these medallions at random distances from each other, on the sidewalk, on the street, in parcs, and there are even 4 inside the halls of the Louvre and one in the Observatoire.

Tracing the Paris meridian

On june 17th 2023, a hot and sunny day in Paris, I decided to go to the Parc Montsouris in the south of Paris and try to find some of these Arago-medallions, while walking along the meridian to the north of Paris, a distance of about 8 km in a beesline. I got a very useful KML-file from https://chrismolloy.com/arago to locate the medallions. I started at the Mire du Sud (South beacon) at the south side of the Parc Montsouris (picture #4). These beacons (there is also a North beacon) were used to align the astronomical instruments in the observatory. Apparently these instruments were not placed exactly on the Paris meridian, because the Mire du Sud is located about 40 m east of it.

I soon found some medallions on my way north through the park. Their longitude was 2°20'11" East, while most publications, notably Wikipedia, give 2°20'14" East as the longitude of the Paris meridian. I can't figure out this discrepancy, moreover because on maps clearly the longitude of the observatory (where the meridian started, (picture #5)) is also marked around 2°20'11".

In some places only a round hole is left where the medallion was removed. Since 2006 when the medallions appeared in the movie of Dan Brown's Da Vinci Code, quite a few have been removed and taken as a souvenir. Another few have disappeared during road works and never replaced.

In the Rue Emile Dubois I passed a big apartment building called "Méridien de Paris" (picture #1). This large block of flat, designed by Héaume and Persitz, was build in 1968, and consists of 3 wings, radiating from a center point. I checked on the map, and indeed this center is exactly located on the Meridian. I'm making a point of mentioning this building, because I didn't find any mention of this building in other descriptions of the meridian, and I only stumbled upon it by taking a wrong turn, plus: this must be the biggest marker of any meridian by far!

On my walk north through Paris also I found some medallions in the Jardins du Luxembourg, which are beautifully laid out and centered along the Meridian, and across the Seine in the Louvre square, close to the glass pyramids. Finally, on the hill of Montmartre, I wanted to go to the Mire du Nord, the North Beacon, at the foot of the Moulin de la Galette (picture #7). But this is on private property and could not be visited.
Ah well, time to end the walk and have a cold glass of Pastis -avec des glaçons!