862 WOEKS PUBLISHED FROM 1819 TO 1829. 



Humboldt, who was holding a Congress of his own To 

 this few were admitted save himself, and the King of 

 Prussia. It related to his old scheme of travelling in 

 Asia. The king promised to defray the expenses of his 

 preparations, and to allow him twelve thousand thalers a 

 year during the journey, which he purposed to commence 

 at once. His plans, however, were thwarted, as they 

 usually were in such cases, so he returned to Paris. 



The next ten years of his life were prodigal in books. 



In 1819 he published the second volume of his " Yoy- 

 age to the Equinoctial Regions," and "Mimosas and 

 other Leguminous Plants of the New Continent." In 

 1820 appeared a second paper "On the Mountains of 

 India," and the fourth volume of " The New Genera and 

 Species of Plants." The fifth volume of "The New 

 Genera" was published in the ensuing year ; the sixth in 

 1823. To the latter year belongs his " Geological Essay 

 on the bearing of the Rocks of both Hemispheres." In 

 1824 he published a work "On the Structure and Opera- 

 tion of Volcanoes," and in 1825 the seventh volume of 

 " The New Genera," the third volume of his " Voyage 

 to the Equinoctial Regions," and "A Numerical Esti- 

 mate of the Population of the New Continent." In 

 1826 and '27 he published " The TemjDcrature of the Sur- 

 face of the Sea in different parts of the Torrid Zone," 

 "The Principal Causes of the difference of the Tempera- 

 ture of the Globe," and "A Political Essay on the 

 Island of Cuba." The draft of this latter work is to be 

 found in the third volume of " The Voyage to the Equi- 

 noctial Regions." He has expanded the chapter in 

 which it occurred, and enriched it with a Map, and a 

 Supplement, devoted to the Internal Resources and Com- 



