CALDAS, Francisco José de (1768-1816). Autograph letter signed ('Caldas') to his close friend Antonio Arboleda Arraechea, R[ea]l Observ[atorio] de S[an] Carlos [Bogotá], 28 February 1806, relating how José Celestino Mutis chose him to succeed as Director of the first Observatory to be built in America, quoting from his mentor's petition to the Virrey of Colombia ('many envy my luck in Santa Fe, especially after 9 February of this year, a memorable date for me, the day of my glory'); Caldas also discusses Christianity, the Graham pendulum and the works of Madame de Gerlis, 6½ pages, 4to. Provenance: Sotheby's sale, 9 June 2005; the Albin Schram Collection. The first recorded letter by the Colombian scientist to be written from the newly-built Observatory in San Carlos.