Geoscience Reference
In-Depth Information
Places
Bourges
The graceful gothic cathedral of Saint-Etienne at Bourges is distinguished by its 13th century
stained glass windows, which rise to the roof among the five tiers of arches along the flanks
of the cathedral. In 1795 Delambre used the pelican-shaped weather vane on the cathedral
tower as a central triangulation site in his survey of the region. The cathedral has a
meridiana,
which was installed in 1757, three years before his death, by a canon of Notre-Dame des
Salles. A thin copper strip on the pavement between the third and fourth side-arches marks
the north-south line. The cathedral has no transept and the
meridiana
cuts across the nave at
an angle of about 80° to the axis of the nave between the third and fourth arches. There are
no markings along the strip except for a circle carved in the stone floor near the south end,
presumably the position of the Sun at midsummer, so the
meridiana
was not very well devel-
oped as an astronomical instrument. Perhaps this is because the installation of the
meridiana
was so close to the death of its rather aged initiator. The aperture of the
meridiana
is a hole
made in one of the high stained glass windows of the south side. The hole is in the elbow of
the figure in green on the left of center, and it is rather surprising that such a hole could be
made in one of these ancient windows. There is also a stone memorial in the floor beside the
meridian strip at the south end commemorating its maker. It reads as follows:
DOM PETRUS ESTERLIN SUBDIAC
CAN. HUI ECCL. OBIIT DIE 2 ^
MARTII. 1760 ÆTAT 72
(Father Pierre Esterlin, sub-deacon and canon of this Church. Died 2 March, 1760 aged 72).
IN ITALY, MÉCHAIN learned of Delambre's fall from favor and concluded from
the fact that he had not heard anything from France that he had been abandoned. In
a way this was a relief because he would not have to explain the error of measure-
ment of the latitude of Montjuïc, but the relief was short-lived when he learned that
the project had been restarted and that he had been appointed to continue his part
in its completion. The large increase in salary he was offered could not erase his
despair at the thought of having to reveal his scientific incompetence to his colleagues.
The disgrace seemed imminent when Méchain was called back to Paris for discus-
sions about the project. No wonder he contemplated the words of refugees from
France who advised about the possibly fatal uncertainties of a return to home;
should he rather accept the less dangerous poverty of exile?
Places
Lieusaint
The meridian passes near to the western boundary of the Seine et Marne department, where
Lieusaint was the northern limit for the 1798 survey from this point to Melun by Jean-
Baptiste Delambre. A stone pillar marks his triangulation point here.
Méchain oscillated between the call of duty and his family as well as the fear of
conspiracy, enmity, exposure, and disgrace. Finally in April 1795 he returned on the
mail boat to Marseille but even though he was back in France, he dithered, staying
in Marseille for five months. Eventually he decided to go, not to Paris, but to
Perpignan to take up the measurements again but he waited too long; the weather
had turned and he could not make the measurements that he needed. Worse,
Delambre, who had been working hard during the summer, was starting to take an
interest in Méchain's measurements, and wanted to combine them into the final
analysis. Delambre arranged with Méchain that they would continue the triangulation
