148 ALEXANDER VON HUMBOLDT. 



in Leipziger Strasse, about the year 1835, the copper hut was 

 taken down, and re-erected at the new observatory according 

 to the plan suggested by Gauss in 1833. During the Asiatic 

 expedition Humboldt supplemented his c astronomical observa- 

 tions for the geographical determination of places with observa- 

 tions upon terrestrial magnetism.' 1 The suggestion made by 

 Humboldt, upon his return to St. Petersburg, that a connected 

 line of magnetic stations should be established throughout 

 Russia, has been already alluded to in the narrative of the 

 Asiatic expedition : his successful appeal to Great Britain 

 for the extension of the line of observations, so as to encompass 

 the globe, will be found recorded in the following chapter. To 

 Humboldt is also due the institution in 1828 of thermometric 

 observations in the mines of Prussia, with the object of ascer- 

 taining the mean temperature of the earth. 



During the years from 1827 to 1830 Humboldt was as actively 

 engaged as ever in various branches of science. He contributed 

 papers upon meteorology, terrestrial magnetism, and volcanic 

 agency, to Poggendorff s ' Annalen,' and the ' Annales de Chimie 

 t de Physique ; ' for Crell's Journal he prepared a treatise 

 upon the systems of numeration in use among various nations, 

 and upon the value given by position to numerals in the Indian 

 system a subject to which he had given some attention while 

 in Paris ten years previously, and in which, together with every- 

 thing that was connected with the history of discovery, he main- 

 tained a lifelong interest. He sent to the c Hertha ' many im- 

 portant communications on geographical subjects, which he was 

 constantly receiving from all quarters. From this epoch, so 

 productive of results in the annals of science, dates the forma- 

 tion of the Geographical Society of Berlin, which was orga- 

 nised on April 26, 1828, by Baeyer, Berghaus, Oetzel, Klceden, 

 Zeune, and others, and held its first sitting under the presidency 

 of Karl Hitter on June 7, in the same year. 2 Humboldt was never 

 more than an honorary member of the society, and as such 

 regularly attended the commemorative meetings held every four 



1 ' Kosmos,' vol. iv. p. 69 ; a general outline of the history of the obser- 

 vations upon magnetism undertaken during the first half of this century 

 is given in pp. 63-77. 



2 'Karl Eitter, ein Lebensbild/ by G. Kramer, vol. ii. pp. SO, 31. 



