Autograph letters signed (10, one incomplete), and autograph document signed : Paris, to various recipients, including General Calon, M. Le Chevalier, M. Villar, and M. Vallogne, 1780 June 7-1803.

Concerning his cartographical work, his astronomical observations, and his geodetic measurements which determined the metric unit of length. The letter of 1780 June 7 concerns the cartographical position of Danzig and contains an analysis of various astronomical observations of La Hire, Hevelius, Cassini, Thomas Streete, and Halley; the letter of 1783 Sept. 3 contains a detailed account of his observation of a lunar eclipse. Other letters concern his attempts to make geodetic measurements in southern France and Spain in order to establish the length of the meter. With frequent references to his partner Delambre.