"Meridienne de Sain Port [sic] ou Saint Assise".

Folio, 36 x 23 cm: [6]-31 pp., 20 blank ff. (occ. sm. marg. stains).

Contemp. mottled calf, double gilt-lined border on boards, gilt-orn. spine with raised bands, gilt-titled label.

Unpublished manuscript, not signed but most certainly by the hand of the author, de Mairan (1678-1771), French mathematician, astronomer and geophysicist, member of the "Académie des Sciences", "Académie française" and numerous scientific academies in France, England, Scotland, Sweden, Italy and Russia. He stated indeed that he made scientific observations at Saint-Assise Castle (cf. his "Traité physique et historique de l'aurore boréale", 2nd ed., Paris, 1754, p. 430) and the handwriting is identical to that of the letter from de Mairan preserved at the Paris Observatory. In the present manuscript, he added several marginalia with comments upon his earlier observations. Several pages are left in blank, most probably because he anticipated to add more data. The work contains a precise description of astronomical, geodesical, meteorological and geographical observations made from April 1738 to November 1761, chiefly at Château de Sainte-Assise near Seine-Port (south-east of Paris), here spelled Sain-Port. The castle was owned by Jean-Baptiste Glucq, baron de Saint-Port, a wealthy magistrate, manufacturer and collector, who hosted writers and artists like the painter Watteau, and King Louis XV himself, among other distinguished visitors.