43

The Connaissance des temps is the oldest of the astronomical and nautical ephemerides, published under the auspices of the Royal Academy of Sciences, without interruption ever since March 1679. It is the model on which the royal astronomer Nevil Maskelyne built his Nautical Almanac in 1767, the future “best-seller” in ephemeris during the nineteenth century, and the chief competitor of the Connaissance des temps. The astronomer Jérôme Lalande made changes to this publication beginning in 1760, changes that would be felt well into the twentieth century. In 1786, his successor, Pierre Méchain, transformed the ephemeris into a nautical almanac at the request of the Minister of the Navy, who further financed the first use of calculator of the Connaissance des temps under the Academic aegis. Passing through the Revolutionary period without too many difficulties, Lalande ensured the continuity of publication for the Connaissance des temps. In 1795, he was also with Lakanal the co-founder of the Bureau des Longitudes, and the supporter of the Comité d'instruction publique, the Dépôt de la Guerre and the Bureau du Cadastre. With the aid of these funds and various other supporters, Lalande and his various “cooperators” ensured the continuity of this important scientific work, from the end of the Old Regime and the suppression of the academies in August 1793 until the First Empire and the resumption of the production of the ephemeris by the Bureau des Longitudes. The study follows the means of financing of this ephemeris, and thus attempts to understand the motivations of the various personalities of this history.