Alexander von Humboldt Autograph Letter Signed

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 German, signed “A. v. Humboldt,” one page, 7.25 x 7.5, February 2, 1840. Untranslated handwritten letter by the great naturalist. Professionally inlaid into a slightly larger sheet and in very good condition, with scattered staining and several small repaired edge tears.