Friedrich Wilhelm Karl Heinrich Alexander von Humboldt, one of the most famous men of his time, a polymath and Renaissance man in an age of genius, perhaps the greatest naturalist and explorer of the nineteenth century, was born in Berlin on 14 September 1769. He was the second son of the royal chamberlain Alexander Georg von Humboldt and Maria Elisabeth Colomb von Humboldt. His older brother, Karl Wilhelm, was to achieve European fame in his own right as politician, philologist, and philosopher.

After their father's death in 1779 the brothers were educated by energetic and demanding private tutors, under the supervision of their mother, at the family estate in Tegel, near Berlin. They studied the classics--concentrating, as was still the custom, on Virgil and Horace; French, the obligatory language of instruction and discourse and the scientific lingua franca; mathematics; drawing; and later, philosophy, law, and political science.

The tutors had given...