VU1 PREFACE TO THE SECOND AND THIRD EDITIONS. 



tact with chemically different substances, often gave a more specific 

 and graver turn to our discourse. The "Rhodian Genius" was 

 written at this time: it appeared first in Schiller's "Horen," a 

 periodical journal; and it was his partiality for this little work 

 which encouraged me to allow it to be reprinted. My brother, in 

 a letter forming part of a collection which has recently been given 

 to the public (Wilhelm von Humboldt's Briefe an eine Freundin, 

 th. ii. s. 39), touches tenderly on the subject of the memoir in 

 question, but adds at the same time a very just remark: "The de- 

 velopment of a physiological idea is the object of the entire treatise; 

 men were fonder at that time than they would now be of such semi- 

 poetic clothing of severe scientific truths." 



In my eightieth year, I am still enabled to enjoy the satisfaction 

 of completing a third edition of my work, remoulding it entirely 

 afresh to meet the requirements of the present time. Almost all 

 the scientific Elucidations or Annotations have been either enlarged 

 or replaced by new and more comprehensive ones. I have hoped 

 that these volumes might tend to inspire and cherish a love for the 

 study of Nature, by bringing together in a small space the results 

 of careful observation on the most varied subjects; by showing the 

 importance of exact numerical data, and the use to be made of them 

 by well-considered arrangement and comparison; and by opposing 

 the dogmatic half-knowledge and arrogant skepticism which have 

 long too much prevailed in what are called the higher circles of 

 society. 



The expedition made by Ehrenberg, Gustav Rose, and myself, 

 by the command of the Emperor of Russia, in 1829, to Northern 

 Asia (in the Ural and Altai Mountains, and on the shores of the 

 Caspian Sea), falls between the period of publication of the second 

 and third editions. This expedition has contributed materially to 

 the enlargement of iny views in all that regards the form of the 

 surface of the earth, the direction of mountain-chains, the connection 

 of Steppes and Deserts with each other, and the geographical distri- 

 bution of plants in relation to ascertained conditions of temperature. 

 The long subsisting want of any accurate knowledge on the subject 

 of the great snow-covered mountain-chains which are situated be- 

 tween the Altai and the Himalaya (i. e. the Thian-schan and the 



