BONPLAND'S CAPTIVITY. 351 



sessed of a mind riot less characterized by activity 

 than the vastness of its acquirements, Humboldt in 

 the mean while engaged in various investigations, 

 which he has partly published in the foreign jour- 

 nals. In concert with M. Gay Lussac, with whom 

 he lived for several years in the most intimate 

 friendship, he has made numerous magnetic experi- 

 ments, and verified Biot's theory respecting the po- 

 sition of the magnetic equator. They have found 

 that the great mountain-chains, and even the active 

 volcanoes, have no appreciable influence on the mag- 

 netic power ; and have established the fact, that it 

 gradually diminishes as we recede from the equator. 



On the return of the philosophers from America, 

 Bonpland was appointed by Bonaparte to the office 

 of superintending the gardens at Malmaison, where 

 the Empress Josephine, who was passionately fond 

 of flowers, had formed a splendid collection of ex- 

 otics. His amiable disposition, not less than his ac- 

 quirements, procured for him the esteem of all who 

 knew him. In 1818 he went to Buenos Ayres as 

 professor of natural history. In 1820 he under- 

 took an excursion to the interior of Paraguay ; but 

 when he arrived at St. Anne, on the eastern bank of 

 the Parana, where he had established a colony of In- 

 dians, he was unexpectedly surrounded by a large 

 body of soldiers, who destroyed the plantation and 

 carried him off a prisoner. This was done by the 

 orders of Dr. Francia, the ruler of Paraguay ; and 

 the only reason assigned was his having planted the 

 tea-tree peculiar to that country, and which forms a 

 valuable article of exportation. He was confined 

 chiefly in Santa Martha, but was allowed to practise 

 as a physician. Humboldt applied in vain for the 

 liberation of his friend, for whom he appears to have 

 cherished a sincere affection. According to a late 

 report, however, he has obtained his liberty, and re- 

 turned to Buenos Ayres. 



In October, 1818, our author was in London, 



