Seven autograph letters, of which six signed (‘D’ortous de Mairan’), to [the mathematician Gabriel Cramer] (6) and to [Jean-Henri-Nicolas Bouillet], Paris, Clichy and n.p., 26 July 1744 - 8 August 1760 and n.d.

Jean-Jacques d'Ortous de Mairan (1678-1771)
Seven autograph letters, of which six signed (‘D’ortous de Mairan’), to [the mathematician Gabriel Cramer] (6) and to [Jean-Henri-Nicolas Bouillet], Paris, Clichy and n.p., 26 July 1744 - 8 August 1760 and n.d.

In French, 20 pages, various sizes (187 x 150mm to 226 x 186mm), on bifolia, 5 with integral address leaves and 4 preserving Mairan’s seal. Provenance: Sotheby’s, 16 May 1978.

Reporting on the French Geodesic Mission to the Equator led by La Condamine, Bouguer and Godin, and mentioning Euler and Newton. Mairan describes the mission and the routes taken in his letter of 26 July 1744: ‘These men all took different routes to increase their observations. M. Bouguer followed the Magdalena river which brought him to Cartagena and then Saint Domingue. M de La Condamine navigated the Amazon river which took him to Pará. I believe M. Godin must have reached Portobelo […] I do not doubt they shall give us a thousand other equally curious observations’. In the letter of 2 September 1750, he discusses Euler, writing that he intends to compose a response to a letter he received from the German mathematician: ‘… his system hardly seemed different to my own. Certainly we agree on several things, but we differ substantially on others, and especially on our principles. However, this is all the better as the basis of my defensive critique.’

Mairan was a natural philosopher who made discoveries in the fields of astronomy, biology and palaeography. His protégé was Pierre Bouguer, one of the leaders of the French Geodesic Mission, which brought back observations on longitudinal observations at the equator. Gabriel Cramer (1704-1752) was a Genevan mathematician and physicist. See lots 346 and 358 for a document signed by the three expedition leaders and a letter by La Condamine about the expedition.