Humboldt, a small man and intellectual giant, was uncommonly well-connected. Werner taught him geology. Gay-Lussac savaged some of his work, but they became friends and ascended Vesuvius in eruption. He named the brazil-nut tree after Berthollet, travelled in the Low Countries and England with Forster, explored Latin America with Bonpland, and met Jefferson. Felix Mendelssohn, a family friend, dedicated a cantata to him. He wrote to Arago, starting 40 years’ friendship; Faraday was another correspondent. He knew Heine and Darwin, met Meyerbeer frequently, contributed to Schiller’s periodical, and taught Agassiz geology.