242 ALEXANDEK VON HUMBOLDT. 



in the Mediterranean. To this elevated land Spain owes her 

 existence, but to this also is due the severity of the climate 

 and the sterility of the soil everywhere excepting along the 

 coast line. Near Madrid the olive trees are often injured by 

 the cold, and oranges are rarely to be seen growing in the open 

 air. . . . But I am beginning to write descriptions, which I 

 never intend to do, as I should then be sending you a book 

 instead of a letter. 



4 If, dearest friend, I have not sent you a line since I left 

 Marseilles, I have not the less been occupied on your behalf 

 and for your gratification. I am just now despatching you a 

 box containing 400 plants, and when you look them through, 

 you will be convinced that in all my wanderings, whether amid 

 woods, over plains, or along the sea-shore, scarcely a day has 

 passed in which you have not been vividly before me. Wher- 

 ever I have been I have made collections for you, and only 

 for you ; for I do not intend to begin collecting for my own 

 herbarium till I have reached the other side of the ocean.' 



A letter to Von Zach, from Madrid, dated the 23rd Floreal, 

 year VII. (May 12, 1799), is not less full of detail, though 

 embracing a very different class of subjects. 1 



In this letter Humboldt mentions that the Paris Board of 

 Longitude had lent him a compass constructed by Lenoir on 

 Borda's plan for registering the dip of the needle, and that a 

 similar instrument was in the possession of Nouet, who, it 

 will be remembered, had been attached to Bonaparte's expedi- 

 tion. Humboldt goes on to remark, that but for the un- 

 fortunate circumstances which had prevented his journey to 

 Africa, it would have been possible, by comparing the results of 

 the two instruments, to have ascertained within the space of 

 eight months the magnetic constants for the whole length of 

 the Mediterranean, from the Straits of Gibraltar to the 

 Isthmus of Suez. He then proceeds to give details of various 

 methods of observation, and magnetic results obtained at Paris, 

 Nismes, Montpellier, Marseilles, Perpignan, Grironne, Barce- 

 lona, Cambrils, Valencia, Madrid, and other places ; he further 

 appends a series of meteorological observations with determina- 



1 ' Allgemeine geographische Ephemeriden,' vol. iv. p. 14(3. 



