24 



fissures. These diabases are the same as those 

 of Bohemia, Saxony, and Franconia* ; and what- 

 ever opinion is entertained on the ancient causes 

 of the oxidation of the Globe at its surface, all 

 those primitive mountains, which contain mix- 

 tures of hornblende and feldspar, either in veins, 

 or in balls with concentric layers, will not, I 

 suppose, be called volcanic formations. Mont 

 Blanc and Mont d'Or will not be ranged in the 

 same class. The partizans of a universal vol- 

 canism, or of the ingenious Huttonian theory, 

 themselves make a distinction between the lavas, 

 which were melted under the simple pressure of 

 the atmosphere at the surface of the Globe, and 

 those layers formed by fire beneath the immense 

 weight of the ocean and superincumbent rocks. 

 They would not confound Auvergne and the gra- 

 nitic valley of Caraccas under the same denomi- 

 nation, that of a country of extinct volcanoes. 



I never could have uttered the opinion, that 

 the Silla and the Cerro de Avila, mountains of 

 gneiss and mica-slate, were a dangerous vicinage 

 for the capital, because they contained a great 

 deal of pyrites in subordinate beds of primitive 

 limestone. But I remember having said, during 

 my stay at Caraccas, that the eastern extremity 



* These gruensteins are found in Bohemia, near Pilsen, in 

 granite ; in Saxony, in the mica-slates of Scheenberg ; in 

 Franconia, between Steeben and Lauenstein, in transit'rm 

 slates. 



