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Saint Sulpice
Paris - France

Saint Sulpice

Saint Sulpice - Paris, France

Pl St Sulpice 75006. Luxembourg Quarter.

Commenced in 1646 and built over 134 years to Daniel Gittard's plans. It has a facade by Italian architect Giovanni Servandori. Completed in 1776.

Meridian Line

A notice nearby reads :

"The meridian line materialized by a brass inlay in the pavement of this church is part of a scientific instrument built here during the 18th century. This was done in full agreement with Church authorities by the astronomers in charge of the newly established Paris Observatory. They used it for defining various parameters of the earth's orbit. Similar arrangements have been made, for the sake of convenience, in other large churches like the Bologna cathedral where Pope Gregory XIII had preparatory studies made for the enactment of the Gregorian calendar.

Contrary to fanciful allegations in a recent best-selling novel, this is not a vestige of pagan temp0le. No such temple ever existed in this place. It was never called a Rose-Line. It does not coincide with the meridian traced through the middle of Paris Observatory which servers as the reference for maps where longitudes are measured in degrees East or West of Paris. No mystical notion can be derived from this instrument of astronomy except to acknowledge that God the Creator is the master of time.

Please also note that the letters P and S in the small round windows at both ends of the transept refer to Peter and Sulpice, the patron saints of the church, not some imaginary Priory of Sion."

The brass line on the floor of the church and continued on the obelisk against the wall forms part of an "astronomical gnomon" built here in 1743.

This scientific instrument comprises :

a - the "meridian" line preciously orientated South/North
b - small aperture in the metal plaque on the right hand upper side of the opposing window

It has never been called a "rose line"

It is not the vestige of an ancient pagan temple. No such edifice ever existed on this site.

It has never been used to define "prime meridian".

Gnomon

Base of Obelisk

How the Gnomon was used

At noon, local solar time, the sun's rays passing through the aperture project a disc of light which crosses the line at a different point everyday.

By studying the movements of this image of the sun, the astronomer P.-Ch. Le Monnier ( 1715-1799 ) was able to :
- ascertain various parameters of the earth's rotation.
- to check the calculations made in the the 16th century, by order or Pope Gregory XIII, to prepare for the adoption of the "Gregorian" calendar so as to ensure the feast of Easter is always celebrated near the date of the first full moon after the Spring equinox.

Originally, the gnomon in the church was also intended to help determine the exact time and to relay it to Paris by the toll of bells.

References :

The Meridian Line - Good website that details the function meridian and the function of the Gnomon in the church.