CASSINI fils (J.D.). LE ROY, Pierre. - Lot 17

CASSINI fils (J.D.). LE ROY, Pierre. Voyage fait par ordre du roi en 1768, Pour éprouver les montres marines inventées par M. Le Roy (...) Avec le mémoire sur la meilleure manière de mesurer le tems en mer, qui a remporté le prix double au jugement de l'Académie royale des sciences... par M. Le Roy l'aîné. A Paris, chez Charles-Antoine Jombert, 1770. In-4 (25 x 19 cm), IV-VIII-144-XXIV-60-(2) pp. 10 folding plates including a map, in-text tables. Old fawn calf, spine ribbed and decorated (spine and upper cover faded, worm work not serious). Very rare first edition. Account of the voyage undertaken to test the marine clock of Pierre Le Roy (1717-1785), then watchmaker to Louis XV, in order to solve the problem of determining longitude. Only one entry in the CCFr (BnF). Following the success of Harrison's marine watches, this question aroused a great deal of scientific interest in Europe. By order of the Duc de Praslin, Minister of the Navy, an official expedition was organized aboard L'Enjouée, commanded by Captain de Tronjoly, with Jean-Dominique Cassini (1748-1845), astronomer and last of the Cassini line, as second-in-command. Comprising title page, table and foreword, 144 pp. for the Voyage à l'île Saint-Pierre proche de Terre-Neuve, et aux côtes d'Afrique et d'Espagne, 24 pp. of tables of times, 60 pp. of the Mémoire sur la meilleure manière de mesurer le temps en mer and finally the errata, extract from the registers of the Académie and the privilege. The illustration includes 10 black copper-engraved plates (6 by Gardette): 3 views (Vue de Chapeau Rouge, Vue la Rade de l'isle de St Pierre proche de Terre neuve and Vue depuis la mer de Salé et Rabath au Maroc); 6 plans and sections detailing the mechanism, including a large illustration of the watch itself and a nautical chart tracing the frigate's route in 1768. Provenance: Paul Harscouet de Saint-George (1807-1870) with his ex libris with arms, engraved by Antoine-François Ollivault probably around 1810-1815 in Rennes. Sabin, 11372.