Geoscience Reference
In-Depth Information
Places
The obelisks at Juvisy and Villejuif
The southern end of the baseline at Juvisy-sur-Orges is commemorated by a stone obelisk
(
Fig. 9
), called La Pyramide, next to Route Nationale 7 and lying on the east side of the road
at the intersection of the D25 to Athis. It was built in 1740, and the tapered column is set on
a square plinth that stands on a small mound. The plinth carries a modern geodesic marker
of iron; the whole monument is made of layers of a soft, yellow stone that have weathered
to gray and reaches some 8 meters high at an ornamental stud. It carries this inscription:
PYRAMIDE DE JUVISY
EXTREMITE SUD DE LA BASE GEODESIQUE
DE VILLEJUIF A JUVISY
1670 (PICARD)
1740 (J. CASSINI ET LACAILLE)
-
PROPRIETE DE L'ACADEMIE DES SCIENCES
(Pyramid of Juvisy, southern end of the geodesic base from Villejuif to Juvisy. 1670
(Picard), 1740 (J. Cassini and Lacaille). Property of the Academy of Sciences.)
The Pyramid is surrounded by a suburban Paris of North African culture with the
Boulangerie (Bakery) de la Pyramide, Garage de la Pyramide, etc, adjacent to it and cheap
stores and run-down apartment buildings crowding onto the surrounding streets. This sub-
urb was a location in Virginie Dispentes' notorious film
Baise-Moi
(2000) in which a drug
dealer is murdered during inter-gang warfare. Today it is not easy to recognize in this
blighted area the scene painted by J. Cassini in his description of the triangulation point he
used nearby: “Juvisy: It is the first tree of the avenue that is to the left in going from Paris
to Fontainebleau, after the gate of the park of Juvisy.”
Further south along RN 7 is a curious castle-like building that was the observatory of
Camille Flammarion (1842-1925), a well-known, popular writer of astronomy and founder
of the Astronomical Society of France.
The northern end of the baseline is commemorated by a similar obelisk at Villejuif, smaller
and more slender than Juvisy, surmounted by a vertical iron rod and without an inscription
(
Fig. 10
). It stands in the garden of 157 bis Avenue de Paris, which can be reached from
RN 7 just north of the intersection with D61. The obelisk stands on a knoll high above the
level of the road from where it can be readily seen. It can be approached more closely by
a flight of stone stairs marked “Privé” and can be viewed over the garden fence. There is a
marker for the Méridienne Verte at the obelisk's foot, and some saplings were planted
nearby in 2000 as part of the Millennium celebrations.
To lay the rods in a straight line along the chosen route from Villejuif to Juvisy
Picard must have established a new, or straightened a pre-existing track through the
area's woodlands. This route must have been useful for communication from the
south into Paris, and the track was evidently maintained and developed by Frenchmen
who came through the area after Picard left. His track became the Avenue de Paris
in Villejuif and, eventually, Route Nationale 7 through Orly to Juvisy. Picard would
have been baffled and astounded if he had known his track would one day become
a four or six lane highway tunneling under the airplane taxiways of an airport.
Having laid out his measured baseline, Picard triangulated from its ends to land-
marks in the surrounding landscape. From those landmarks he triangulated to others
ultimately heading right across Paris to the north and a little towards Bourges to the
south. Of course not all potential landmarks were equally useful - to measure a triangu-
lation triangle it must be possible from any one trig point to see each of the other two.
To establish this it is necessary to check out the potential landmarks and check
