DYNAMICAL GEOLOGY. . 259 



acquaintance with the mode of occurrence of the volcanic 

 rocks in Rhineland enabled him gradually to form his own 

 judgments, and these were unfavourable to Von Buch's 

 theory. A visit to Auvergne, Mont d'Or, and the Cantal moun- 

 tains still further shook his confidence in it. He examined 

 the basaltic rocks above the Tertiary fresh-water limestone 

 of Limagne, and felt convinced that these could not have 

 been bulged up as solid rock from the ocean-floor, but must 

 have flowed into their present position superficially as a lava. 

 Again, he could see no evidence in favour of Von Buch's 

 hypothesis that the ravines of the Cantal represent eruptive 

 fissures formed during upheaval, but rather believed them 

 to be ordinary erosion valleys. Steininger, however, con- 

 tinued to retain Von Buch's theory of volcanic upheaval as 

 applicable to the particular cases of isolated conical hills 

 composed of domite or trachyte rock. 



The strongest opponents of Von Buch's theory were, however, 

 Poulett-Scrope, 1 Charles Lyell, and Constant Pre'vost. 



In 1816-17, Poulett-Scrope, as a young student, had the 

 opportunity of observing the volcanic surroundings of Naples, 

 and this gave the impulse to his scientific studies. He 

 returned in 1818, 1819, and 1822 to Southern Italy, and 

 visited Vesuvius, Etna, the Lipari Isles, the neighbourhood 

 of Rome, and the Euganian Isles. In 1821 he spent several 

 months in the Auvergne district,' and in 1823 he made him- 

 self acquainted with the Rhineland and Eifel volcanoes 

 described by Steininger. 



In 1825 he published his famous work on Volcanoes, and 

 in 1826 his excellent monograph of the extinct volcanoes in 

 Central France. Poulett-Scrope's works have held their 

 position as the basis of volcanic teaching. Like Hutton and 

 his own contemporary, Charles Lyell, he was a Uniformitarian, 

 and tried to explain the events of past geological ages by the 

 action of forces which exist. 



Observing the enormous expansive force of the aqueous 



1 George Poulett-Scrope was born in 1797 in London, the son of a rich 

 merchant, J. Poulett Thomson ; he studied in Cambridge under Professor 

 Sedgwick, and assumed the name of Scrope after his marriage with the 

 heiress of the old Scrope family. Pie became a Member of Parliament in 

 1833, anc l afterwards devoted himself mainly to political activity, but did 

 not neglect his studies on volcanoes. In 1867 the Geological Society 

 conferred the Wollaston medal on him. He died at Fairlawn, Surrey, in 

 January 1875. 



