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in a flurry of priestly robes to rebuke noisy tourists disturbing the holiness of the
moment. In front of the chairs where the penitents wait there is a plaque 90 cm
square on the floor at the end of the brass meridian strip. It is engraved:
SOLSTITIUM ÆSTIUM
ANNI MDCC XLV
[P]RO NUTIATIONE AXIOS TERREN
OBLIQUITATE ECLIPTICÆ.
( The summer solstice in the year 1745. To find nutation, the terrestrial axis and the
obliquity of the ecliptic ).
There is a brass protective plate to protect this flagstone, but it has been under repair
for the last 40 years; as a result the writing on the flagstone is becoming worn.
Where the line passes across the center of the church, just inside the altar gates
at the crossing of the nave and the transept, a brass ellipse marks the equinoctial
position of the Sun's image. There used to be a brass ellipse to mark the summer
solstice but it has since been lost.
Though the Church of St. Sulpice is large, the transept is not wide enough to
accommodate the whole of the meridian line on the floor where the image of the
midday Sun moves towards winter solstice. The north end of the meridian contin-
ues up the wall in a vertical brass inlaid line on the bisecting axis of a 10 meter high
stone pillar, or gnomon , made of red, gray and white marble.
Places The Gnomon of St. Sulpice
The instrument of St. Suplice is known in the Church as a “gnomon” or an instrument of
knowledge. We would presently reserve the word for the part of a sundial that casts
a shadow on to a scale to tell time. The meridiana of St. Sulpice has an erect pillar, like a
gnomon, but it does not cast a shadow, it receives one. The gnomon stands against the north
wall of the transept in a gloomy corner ( Fig. 27 ). There is a horizontal arrow and two wavy
lines part way (approx. 6 meters) up the pillar, marking the position of the Sun as it passes
into the zodiacal signs of Aquarius and Sagittarius. Right at the top is the barely visible
sign for Capricorn which marks the position of the solar image at midwinter solstice. The
gnomon tapers upwards above the base pedestal from two brass crocodiles and floral flor-
ishes and is surmounted by a brass orb and cross. It was realized by Jean Nicholas
Servandoni (1695-1766), French decorator, artist and scene-painter. He had designed the
building of the façade of the church, though work on it was suspended after objections to
its design, and it was completed by the architect Jean-François Chalgrin (1739-1811), also
known for the Opéra.
The base ( Fig. 28 ) has a long inscription. On the left (west) half of the base it states:
GNOMON ASTRONOMICUS
Ad Certam Paschalis
Æquinoctii Explorationem
( An astronomical gnomon for the determination of the Easter Equinox ).
There follows an engraving of scientific instruments set on leafy branches: a topic, globe,
dividers, a square, armillary sphere, telescope, protractor, etc. These instruments are those that
would have been used by Le Monnier to lay out the meridiana . There is also a snake curling
through the leaves and around the measuring scale, presumably a warning by Servandoni
against presuming too much with the knowledge being gained by the meridiana.
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