66 HISTORY OF GEOLOGY AND PALEONTOLOGY. 



menced the publication of his great work, Travels in the 

 Equinoctial Regions on the New Continent. This work com- 

 prises twenty volumes ; but although there were several 

 collaborators, the work was never quite completed, and the 

 expenses in connection with it swallowed up the remainder of 

 Von Humboldt's means. In the spring of 1805 he visited 

 Italy, and with his friends, Gay Lussac and Leopold von 

 Buch, saw an eruption of Vesuvius. 



Humboldt's best contributions to geology were his investiga- 

 tion of volcanoes and earthquakes, and the broad generalisations 

 which he drew regarding volcanic action. He concluded 

 his description of American volcanoes with a review of all 

 the volcanic phenomena known to have transpired on the 

 face of the earth, and tried to demonstrate, from a large number 

 of observations, that the subterranean centres of volcanic action 

 are in direct communication with one another. He placed 

 great importance upon the connection of volcanoes and earth- 

 quakes on the coasts of the Gulf of Mexico and in the Antilles, 

 where subterranean disturbances were felt almost simultaneously 

 over a district several thousand square miles in extent. Hum- 

 boldt's account of the catastrophe in the year 1759, which gave 

 birth to the Jorulla and five other mountains, and covered an 

 area, of four square miles with a mass of lava, sand, and slag 

 five hundred feet high, still ranks as one of the most note- 

 worthy contributions in the whole literature of volcanoes. 



Widespread interest in scientific circles was also attracted by 

 Humboldt's demonstration of an eruptive fissure one hundred 

 and fifty miles from east to west across Central America, upon 

 which stand the volcanic cones of Tuxtla, Orizaba, Puebla, 

 Toluca, Tancitaro, and Colima. 



Through the generosity of the King of Prussia, Humboldt 

 was enabled to devote his energies to science. During nearly 

 twenty years' residence in Paris (1808-27) he published the 

 series of papers which form the groundwork of his Views of 

 Nature, and also a special geological work entitled Geognostic 

 Essay on the Trend of the Rocks in the Tivo Hemispheres ( Paris, 

 1822). This work practically marked the conclusion of Hum- 

 boldt's literary activity in geology. Upon his return to his 

 native city of Berlin in 1827, Humboldt embarked upon his 

 gigantic plan of producing a physical description of the world. 

 Twenty years passed before this plan was realised and his 

 famous work, The Cosmos, appeared. While the work was in 



