Melvyn Bragg and guests discuss the Prussian naturalist and explorer Alexander Von Humboldt. He was possibly the greatest and certainly one of the most famous scientists of the 19th century. Darwin described him as 'the greatest scientific traveller who ever lived'. Goethe declared that one learned more from an hour in his company than eight days of studying books and even Napoleon was reputed to be envious of his celebrity.A friend of Goethe and an influence on Coleridge and Shelly, when Darwin went voyaging on the Beagle it was Humboldt's works he took for inspiration and guidance. At the time of his death in 1859, the year Darwin published On the Origin of Species, Humboldt was probably the most famous scientist in Europe. Add to this shipwrecks, homosexuality and Spanish American revolutionary politics and you have the ingredients for one of the more extraordinary lives lived in Europe (and elsewhere) in the 18th and 19th centuries. But what is Humboldt's true position in the history of science? How did he lose the fame and celebrity he once enjoyed and why is he now, perhaps, more important than he has ever been? With Jason Wilson, Professor of Latin American Literature at University College London, Patricia Fara, Affiliated Lecturer in the Department of History and Philosophy of Science at the University of Cambridge, Jim Secord, Professor in the Department of History and Philosophy of Science at the University of Cambridge and Director of the Darwin Correspondence Project.