376 SPECIAL GEOLOGY. 



mastodon, hippopotamus, rhinoceros, tapir, horse, deer, ox, 

 boar, hyaena, bear, dog, castor, cat, and hare. 



The Abbe Croizet, some years since, formed an extensive 

 collection of the fossils of this district, which was pur- 

 chased by the French Government ; and pursuing the same 

 researches he has succeeded in forming a second assemblage 

 of similar remains, which are now in the British Museum. 



EROSIVE FORCE or STREAMS. The power of running 

 water to erode solid rocks, and to produce valleys by their 

 currents, is most strikingly exemplified throughout the whole 

 of this remarkable region. The erosive power of the water 

 has been aided by the proneness of the volcanic rocks to 

 decomposition. In some instances beds of lava have been 

 corroded by the water, which has worn through a mass of 

 rock 150 'feet in height, and formed a channel in the granite 

 beneath, since the lava first flowed into the valley. In 

 another spot, a bed of basalt 160 feet high has been cut 

 through by a mountain- stream. In the valley of Monpezat, 

 the basalt has been similarly worn in more than one direc- 

 tion, by the powerful action of the rivers whose channels 

 it had usurped ; an idea of its present disposition, and the 

 beautiful columnar ranges discovered by this excavation, 

 may be formed from the following sketch, fig. 266.* 



TERTIARY STRATA or OTHER KEGIOKS. Similar extinct 

 volcanoes exist in Hungary, Spain, and other parts of 

 Europe, which, with the salt mines of Gallicia, are referred 

 to this epoch. Tertiary strata are found in North and South 

 America, in India and Australia, and M. Boue has lately 

 discovered a district in Asia Minor, in the vicinity of 

 Smyrna, called the KaraKCKavpevri, or Burnt-up region, com- 

 prising the ancient Sardis and Philadelphia, which presents 

 a close resemblance to Auvergne. In each country are 

 extensive lacustrine formations, cones of scoriae, with currents 

 of lava, and occasionally continuous streams and thick beds 

 of that substance, worn through by the action of running- 

 water. 



FOSSIL INFUSORIA. In strata of this period occurs the 

 siliceous stone called Tripoli, which is also found at Biliii 

 in Bohemia. This rock is almost entirely composed of the 



* From Mr. Scrope's Central France. 



