Scarce map of the United States, showing the distribution of Gold (red) and Silver (blue) in the United States.
Jules Marcou was perhaps the most famous geologist of his time. He worked in early years with Jules Thurmann (1804-1855) on the geology of the Jura Mountains. In 1847 he went to North America as travelling geologist for the Jardin des Plantes, and in the following year in Boston he joined Agassiz, whom he had met in Switzerland, and accompanied him to the Lake Superior region. Marcou spent two years in studying the geology of various parts of the United States and Canada, and returned to Europe for a short time in 1850. In 1853 he published a Geological Map of the United States, and the British Provinces of North America. In 1855 he became professor of geology and palaeontology at the polytechnic school of Zürich, but relinquished this office in 1859, and in 1861 again returned to the United States, when be assisted Louis Agassiz in founding the Museum of Comparative Zoology.