PEEFACE. xiii 



my great regret, been compelled to withdraw his valued co- 

 operation from the work; but I have been fortunately able 

 to secure in his stead the help of Professor W. "Wundt of 

 Heidelberg. 



Her Majesty the Empress- Queen Augusta has in the most 

 gracious manner placed at the disposal of the Editor many of 

 Humboldt's unpublished letters ; unfortunately, a valuable 

 collection of letters perished in the flames during the year 

 1848. Besides the Journals, Frau von Billow placed in my 

 hands twenty-two valuable letters from Humboldt, nineteen of 

 which were written to his brother during the expedition to 

 Russia, and three are addressed to his sister-in-law. 



A series of more than 80 letters, addressed by Humboldt 

 to the friend of his youth, Freiesleben, subsequently Director 

 of Mines at Freiberg, embracing a period from the time of 

 Humboldt's departure from Freiberg to the year 1845, have 

 been placed in my hands by his son, Herr Freiesleben, of 

 Dresden. From Professor Borchardt of Berlin I have received 

 13 letters addressed to Jacobi, the mathematician; from Pro- 

 fessor Kronecker 80 written to Lejeune-Dirichlet ; 30 addressed 

 to Gauss, through the kindness of Professor Schering of Grottin- 

 gen ; 54 to Schumacher, lent, by his sons at Valparaiso and 

 Altona ; 30 to Karsten, Privy Counsellor of Mines, through his 

 son, Professor Karsten, of 9e>l ; 1 1 to W. Struve and Fuss, 

 through Herr Otto von Struve, Director of the Imperial 

 Observatory at Pulkowa ; and 330 to Encke, which have been 

 lent to me by his heirs. From Dr. Gr. von Boguslawski I have 

 received 28 letters addressed by Humboldt to his father, the 

 late Director of the Observatory at Breslau ; from Herr Carus 

 of Dresden 12, addressed to his father, late surgeon to the king 

 and President of the Academy of Leopold-Charles ; and from 

 Dr. H. Vogel 9, addressed to the late Herr Vogel, Inspector 

 of Schools, the father of the unfortunate African explorer. 

 For a valuable collection of 50 letters I am indebted to Madame 

 Richards-G-agiotti, of Florence, and to Von Madler, formerly 

 Director of the Observatory at Dorpat, I am indebted for 19. 



