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246 The Mediterranean of Louis XV
Despite Fontenelle’s rhetoric, Delisle could not claim sole
credit for the shrinking of the Mediterranean Sea: the first
significant attempt to correct representations of its coasts
based on astronomical observations of longitude was carried
out by the Provençal scholar Nicolas-Claude Fabri de Peiresc
(1580–1637). In 1635, he coordinated observations of a lunar
eclipse made by a number of travellers stationed at different
points around the Mediterranean, and thereby determined that
the length of the sea was around 200 leagues shorter than was
commonly believed. 25 Due to the complexity of the operations
involved in such an enterprise, Delisle’s work was evidently
impossible without the backing and resources of the French
administration. Delisle himself never travelled, and he based
his work on the researches of a number of engineers working for
the Royal Navy and astronomers connected to the Académie
des Sciences. Beginning in 1678, Colbert sponsored a number
of cartographic missions in the Mediterranean as part of his
larger agenda of encouraging maritime commerce and protecting
French navigation. According to Colbert, the best way to
assure the glory of the king and the prosperity of France was to
obtain control of the Mediterranean Sea, admonishing his son
and successor Jean-Baptiste, marquis de Seignelay (1651–90) to
do everything in his power to further this enterprise. 26
Following on work by members of the Académie des Sciences
to rectify the coasts of France in the 1670s and 80s, the first
rigorous observations of the longitude of sites in the Levant by
an operative of the French administration were made by the
astronomer Jean-Mathieu de Chazelles (1657–1710). Like
Delisle, Chazelles received his astronomical training from Cassini
at the Paris observatory. In 1685, he was appointed professor
of hydrography in Marseilles and participated in
cartographic campaigns in the Mediterranean between 1686
and 1688 sponsored by Seignelay. In 1693, Seignelay’s successor,
Louis Phélypeaux, comte de Pontchartrain (1643–1727)
appointed Chazelles to travel to Egypt, Greece, Syria, and
25 H. Brown, Scientific Organizations in Seventeenth-Century France
(1620–1680) (New York, 1934), 4–5; Broc, La Géographie, 17.
26 P. Clément, L’Italie en 1671: Relation d’un Voyage du marquis de Seignelay.
(Paris, 1867), 38. Seignelay served as Secrétaire d’Etat à la Maison du Roi,
chargé de la Marine from 1683–90.