xii PREFACE. 



of eight distinct treatises, is devoted to the consideration of 

 each department of science into which his investigations ex- 

 tended. Various portraits, published for the first time in this 

 work, afford interesting records of the personal appearance of 

 Humboldt during the three principal stages of his career. 



The prospectus of the work was issued on the centenary 

 anniversary of Humboldt's birth. I was able to present it in 

 person before the Congress of Astronomers at Vienna, convened 

 on that day in honour of Humboldt, upon which occasion I 

 was entrusted with the pleasing duty of presenting a summary 

 of his valuable services in the department of astronomy. 



Upon my return from Vienna I proceeded without delay to 

 the execution of my scheme. The task of narrating the events 

 of Humboldt's youth and of the years he spent in travel was 

 undertaken by Herr Julius Lowenberg, who had been occupied 

 with the subject for many years, and was in possession of nume- 

 rous documents, letters, and other material indispensable for a 

 biography. The history of Humboldt's sojourn in Paris, where 

 he spent many years in scientific labour and in intercourse 

 with the distinguished men there assembled, was confided to 

 Dr. K. Ave-Lallemant, who has himself spent many years amid 

 the scientific circles of the French capital. Finally, in Dr. 

 Alfred Dove I secured the assistance of one who, from his in- 

 timate acquaintance with the safety of Berlin, is peculiarly 

 fitted to depict in an authentic manner, free from every trace 

 of traditionary false colouring, the closing period of Humboldt's 

 life, dating from the time of his settlement at Berlin. I was 

 thus able satisfactorily to complete the arrangements for the 

 compilation of the purely biographical portion of the work. 

 With regard to the scientific part of my undertaking, I have 

 been fortunate enough to obtain the co-operation of Professors 

 H. W. Dove and J. W. Ewald of Berlin, of Professor A. H. E. 

 Grisebach of Gottingen, and of Professors J. W. Carus, 0. 

 Peschel, and Gr. H. Wiedemann of Leipzig. Professor du Bois- 

 Keymond, to whom had been entrusted the analysis of Hum- 

 boldt's achievements in the province of physiology, has, to 



