The Prussian naturalist Alexander von Humboldt (1769–1859) was one of the most famous explorers of his generation. Charles Darwin called him 'the greatest scientific traveller who ever lived'. In 1799, Humboldt and the botanist Aimé Bonpland secured permission from the Spanish crown for a voyage to South America. They left from Madrid and spent five years exploring the continent. Humboldt reported his findings in a total of thirty volumes, published in French over a period of more than twenty years beginning in 1805. This English translation by Helen Maria Williams of one important component of Humboldt's account, the Relation historique du voyage (1814–1825), consists of seven volumes and was published in London between 1814 and 1829. Volume 4 (1819) describes an earthquake in Caracas (which Humboldt links to the volcanoes of the West Indies), and mountains, plains, hot springs and river systems observed as the expedition travelled onwards.