LALANDE, J.J.Le FRANCOIS & LEONHARD EULER.

Memoire sur la determination de la Parallaxe de la Lune et de la Coubure de la Terre entreprise au Cap de Bonne Esperence et a Berlin par Ordre de S.M.T. Chret. avec le Observations, faites depuis le 25. Nov. 1751. jusqu'au 20. Avril 1752. à L'Observatoire Royal de Berlin. (And same author:) Second Mémoire, sur la Détermination de la Parallaxe de la Lune...1752. (And withbound Euler:) Reflexions sur les Divers Dégrés de Lumiere du Soleil et des autres Corps Celeste.

(Berlin, Haude et Spener, 1752). 4to. Without wrappers extracted from "Mémoires de l'Academie Royale des Sciences et Belles-Lettres", tome VI, pp. 236-279 and 1 engraved plate, pp. 379-411 - pp. 280-310 and 1 engraved plate. The plate showing Le Monnier's quadrant.

Both papers first edition. The famous Lalande-paper describing the measurement of the Moon's distance from the earth, which was accomplished by measuring the parallax from the different places of observation, and thus, by using triangulation methods, he found a Moon-Earth distance of about 60 times the earth's radius, and thus provided a more exact value of the estimates known since antiquity. - "In 1751 Abbé Nicolas de la Caille departed on an expedition to Cape of Good Hope, one of the main purposes of which was to measure the lunar parallax.It was importent that simultaneous measurements be made in Europe at some points on the same meridian.The most advantageous site was Berlin, which unfortunately lacked an adequate instrument, Le Monnier permitted Lalande to go to his place, entrusting him to his quadrant, whic was generally considered to be the best in France. At Berlin, Lalande was admitted to the Prussian cademy, where he enjoied the company of Maupertois, Euler and others..."(DSB).
Euler in his paper (Reflexions of the different degrees of sunlight on other celestial bodies" considers the possibillity of combining distances with degrees of reflected sunlight. - Enestrom: E 178.

Order-nr.: 39088