DYNAMICAL GEOLOGY. 255 



von Buch from the ranks of extreme Wernerians. Nowhere 

 was the re-action in favour of accurate investigation of vol- 

 canoes keener than in Germany, where Werner's remarkable 

 influence had so long retarded progress in this important 

 branch of teaching. Von Humboldt's works (p. 66) gave 

 the first broad conceptions of the arrangement and distribution 

 of volcanoes on the earth's surface. From the characteristic 

 arrangement of volcanoes either as groups or in long series, 

 from their occurrence in all parts of the globe, and from their 

 frequent association with earthquakes, Humboldt concluded 

 that the cause of volcanic phenomena could not be local, 

 but must bear some relation to the constitution of the earth's 

 interior. The serial arrangement of volcanoes led him to 

 believe that the volcanic vents were disposed upon crust- 

 fractures which extended to very great depths. 



Leopold von Buch's visit to Auvergne in 1802 convinced 

 this geologist that the volcanic phenomena of that neigh- 

 bourhood could only have been produced by some general 

 cause associated with the earth's internal heat. It was on 

 this occasion also that Leopold von Buch formed his first 

 crude conception of the theory which, under the name of 

 "Elevation-Crater" theory, was destined to become notorious 

 in geological controversy of the nineteenth century. At this 

 time, however, Buch merely mentioned a central elevation of 

 the Mont d'Or range caused by subterranean forces. 



Von Buch's treatise, On the Geognostic Relations of the Trap 

 Porphyry (1813), contains a careful account of the occurrence 

 and mineral constitution of rocks belonging to the trachyte 

 series. The central elevation, which he had assumed for the 

 Mont d'Or and Cantal area, is in this work applied to other 

 volcanic regions, for example to the Santorin Island, to the 

 trachyte mountains of Hungary, and to the South American 

 Cordilleras, and a distinction is drawn between true volcanoes 

 and mountain-systems representing dome-like crust elevations 

 pushed up by subterranean forces. 



Accompanied by the Norwegian botanist, Christian Smith, 

 in the summer and autumn of 1815, Von Buch explored the 

 Canary Islands, the Palma Islands, and on the return voyage 

 visited the Lancerote Island. The result of this journey was 

 published independently by Buch, as Christian Smith died in 

 the following year on the Congo river, where he had gone with 

 Tuckey's Expedition. Von Buch's descriptive monograph of 



