Next to Napoleon Bonaparte, Alexander von Humboldt (full name, Friedrich Wilhelm Heinrich Alexander Freiherr von Humboldt, 1769–1859) was largely regarded as the most famous man in Europe in his day. Educated in everything from finance and languages to astronomy, geology, and anatomy, Humboldt had a passion for science and travel. Most notable was his voyage to South America (1799–1804), during which he explored the natural landscape, making observations about the animal and plant life, as well as geological and astronomical observations. From this experience, he originated the idea that species vary depending on the climate, which varies with temperature and elevation. He also correctly surmised volcanoes probably align themselves along geological fissures in the Earth’s crust. Humboldt connected the dots between geology and weather, noting how climate changes with elevation; he also was the first to observe how the Earth’s magnetic field varies with latitude, and made observations that would later contribute to theories on how weather systems are generated with the planet’s middle latitudes. When Humboldt’s expedition reached the Pacific, he discovered the Peru Current, which is now also known as the Humboldt Current. For all his explorations and discoveries, Humboldt became a hero when he arrived back in Europe. He wrote about his journeys in the epic 30-volume work The Voyage of Humboldt and Bonpland (1805–1834) and was even more lauded for his two-volume Cosmos (1845, 1847), in which he attempted to unify many scientific disciplines to describe the complexity of nature as a whole system.