German naturalist and explorer (1769–1859) who wrote Kosmos, a massive five-volume study which attempted to unify the various branches of man’s knowledge. ALS in French, signed “Humboldt,” three pages on two adjoining sheets, 4.75 x 4.75, no date [likely circa 1822-23]. Letter to mineralogist Louis-Benjamin Fleuriau de Bellevue, sending his friend Fourier’s book, in part (translated): “In which the problem of heat movement is completely solved. Ridges and edges are special cases only…You will also see in paragraph 52 that the author believes as I do that the heat cannot be compared to any fluid, water in oil…I am asking you to please let me visit you on Wednesday at 11 a.m.” Includes multiple detailed geological sketches and diagrams: first set is four pages on two adjoining sheets, 8 x 12.75, featuring descriptions of earth formations (clay, chalky, and lignite); a large diagram related to the superposition of rocks, with descriptions of each one’s appearance and type; sketches of landscapes; and numerous small sketches of various earth and rock textures, including granite, syenite, gypsum, and limestone; and another sketch of a superposition diagram on an off-white 7 x 9.5 sheet. In overall fine condition. Accompanied by a large print entitled ‘A Proportional and Tabular View of the Superior, Supermedial, and Medial Rocks,’ as well as an export certificate from the French Ministry of Culture.
After his wide travels in Latin America at the turn of the century, Humboldt began work on what would become a 21-year project, describing the lands he explored on his journey for the first time from a modern scientific point of view. He found the intellectual and social stimuli he craved in the vibrant cultural center of Paris, where he mingled with some of science’s greatest minds, including Joseph Fourier. With this letter to noted mineralogist and geologist Louis-Benjamin Fleuriau, Humboldt is most likely passing on Fourier’s Théorie Analytique de la Chaleur (The Analytic Theory of Heat), published in 1822, which reasoned that the flow of heat between two adjacent molecules is proportional to the extremely small difference of their temperatures; the book made major contributions to mathematics and physics, including the law of heat conduction, now known as Fourier's law. Beyond the excellent association to this major scientific figure, Humboldt’s detailed geological sketches hold extraordinary value. Known for his extensive theories on magnetism, volcanicity, seismology, and tectonics, his work on rock formations is incredibly important—and incredibly beautiful, in these hand-sketched pieces.
