Humboldt, Friedrich Heinrich Alexander, Freiherr von (1769–1859) A German naturalist, physical geographer, biogeographer, geologist, vulcanologist, and mining engineer, who began travelling extensively after the death of his mother in 1796. Accompanied by the French surgeon and botanist Aimé Bonpland, he set out to join Napoleon in Egypt, but their plans changed and they went instead to Madrid. Their experiences in Spain made them decide to explore Spanish America. They embarked in 1799 and spent 5 years in the South American tropics, exploring the drainage basins of the Amazon and Orinoco, investigating the properties of guano, measuring the temperature of the ocean current that bears his name, and studying the flora and fauna of the forests and savannah, returning with more than 30 cases of botanical specimens. He wrote on many subjects, his most important botanical work being the 7-volume Nova genera et species plantarum (1815–25), written in collaboration with A. J. A. Bonpland and C. S. Kunth as part six of the 30-volume Voyage de Humboldt et Bonpland (1805–34). In Ideen zu einer Physiognomik der Gewächse (Ideas on a physiognomy of plants, 1806) he proposed the concept of biogeography.

Humboldt, Friedrich Heinrich Alexander, Baron von (1769–1859) German naturalist and explorer. He explored (1799–1804) South America, studying volcanoes, tropical storms and the increase in magnetic intensity from the Equator towards the poles. His five-volume Kosmos (1845–62) describes the physical universe.