Take a glance at the extent and geographical situation of this family of rocks. Everywhere among the Andes and Cordilleras, there are evidences of the elevation of large mountain-tracts, through the agency of volcanoes now extinct, and probably of the age in question. A volcanic region in the north of Spain, extending over twenty square leagues, from Amer to Massanet in Catalonia, is situated among the lower beds of the system, penetrating a nummulitic limestone and other strata, conjectured to belong to the age of our green sand and chalk. The Drachenfels on the Rhine and the Eifel chain of hills near Bonn, are likewise referable to this class of volcanic ejections. The Katakekaumene tract of mountains, in Asia-Minor, is composed of comparatively recent volcanoes, where Mr. Hamilton conceives the great cones of Mont Dore, the Cantal, and Mont Mezen in central France are represented by Ak Dàgh, Morad Dàgh, the trachytic hills east of Takmak, Hassan Dàgh, and Mount Argæus. Similar eruptive indications have been traced by Mr. Grant in the district of Cutch, situated near the eastern branch of the Indus, and consisting of large tracts of tertiary deposits. The elevated regions of the Tyrol, the flanks of the Bernese and Swiss Alps, have been the scene of violent disturbance, during and since the deposition of the tertiary formations; and, in the peninsula of Italy, there are numerous groups of volcanic origin, as in Tuscany the igneous rocks of Radicofani, Viterbo, and Aquapendente, and those of the Campagna di Roma, which are of the same chronological series, or probably not later than the pleiocene period. The West India Islands, the Azores, Iceland, Owhyhee where the peaks of Mauna-Roa and Mouna-Kaa rise to the height of between 15,000 and 16,000 feet above the sea, belong to the same class of phenomena. Thus in every quarter of the globe there have existed Phlegræan fields of ancient as well as of modern date, whose convulsions anterior to all historic records are still traceable in the submergence and closing up of lakes, the drainage of large tracts of land, the upheaval of mountains, and the reduction of the earth to existing superficial arrangements.