VI 



volume will, therefore, consist of two parts, of which 

 the first was published in the Grerman original at the 

 commencement of the present year, and is now pre- 

 sented in the English translation; the possibility of 

 publishing the work in English within so short a time 

 of its appearance in German being the result of the 

 early possession of the larger portion of the proof 

 sheets, for which advantage the editor and translator 

 are indebted to the good offices of M. de Humboldt 

 himself, and to the obliging permission of the Grerman 

 publisher, Mr. Cotta. 



The first 224 pages of the original text and notes 

 were printed early in 1854. The long attachment of 

 the illustrious author to the subject of terrestrial mag- 

 netism, which is contained therein, and which in a very 

 large measure owes to him, and to the impulse given by 

 him, the position which it now occupies, rendered him 

 even peculiarly desiious that its treatment should corre- 

 spond fully to the latest progress of our knowledge. 

 That progress has been such as to render the years 

 which have elapsed since 1854 equivalent to a much 

 longer interval in other departments of science. In 

 this view, therefore, besides making himself some brief 

 but important additions in pp. 449 to 452, M. de Hum- 

 boldt has expressed, on several occasions in the course 

 of our correspondence, a desire that I should make in 



