 On their way back to Europe from Mexico on their way to the United States, Humboldt and Bonpland stopped again in Cuba, leaving from the port of Veracruz and arriving in Cuba on 7 January 1804, staying until 29 April 1804.In Cuba, he collected plant material and made extensive notes.During this time, he socialized with his scientific and landowner friends, conducted mineralogical surveys, and finished his vast collection of the island's flora and fauna that he eventually published as "Essai politique sur l'îsle de Cuba".