Autograph letter signed ("A Humboldt").
1 p. on folded double leaf, approx. 130 x 200 mm. Addressed on another side in Humboldt's hand with his wax seal and post cancel-stamp.
To "Herr Boguslawski", i. e. the meteorologist Georg von Boguslawski (1827-1884), on an appointment.
Folded for mailing, torn where unsealed, a bit marked, pencil notations by a previous owner on one blank portion, and with some denting.