 The fundamental method employed was the exact measurement of distances from which was obtained the longitude and latitude of places; this, supplemented and controlled by the observations of the meridians of the sun and the polar stars, directly gave the latitude.The missionaries were sometimes assisted by the observation of eclipses of the moon and the satellites of Jupiter, of which more perfect process they desired to make use to obtain longitudes, but conditions did not permit.In reply to a criticism of Féret, the learned secretary of the Académie des Inscriptions et Belles-Lettres, Antoine Gaubil wrote (5 November 1736)