RICHER, Jean

Observations astronomiques et physiques faites en l'Isle de Caienne

Paris: Imprimerie Royale, 1679

First edition.

Folio, 71 pp.

Contemporary mottled calf, arms of Louis XIV on both covers, bookplate and stamp of the Marquis de Courtanvaux.

An important early work in precision astrometry. It provided the basis for the first geodetic verification of Newton's law of gravitation (the measurements reported in this book, which gave the first evidence that the earth is flattened at the poles, are referenced in the Principia), provided the first accurate measurement of the distance from the sun to the earth (the coordinated measurements by Cassini at Paris are given in Divers Ouvrages d'astronomie, par M. Cassini , and gave the first precision measurement of a longitude in the western hemisphere. Also on this voyage Richer carried a pendulum clock made by Huygens to measure longitude. The clock stopped, which angered Huygens, but Richer was not to blame.

Thus the book figures prominently at the starting point for the three great enterprises of eighteenth century astronomy - determining the figure of the earth, measuring the size of the solar system, and finding a means for the precise measurement of longitude. This copy was presented by Richer to the Marquis de Courtanvaux. The association with the Courtanvaux family is significant, as Francois Cesar Le Tellier, Marquis de Courtanvaux in the mid 18th century, was active in astronomy and in the testing of marine chronometers at sea. Journal du Voyage de M. le Marquis de Courtanvaux, sur la fregate l'Aurore, pour essayer par ordre de l'Academie, plusieurs instruments relatifs a la longitude .