§ 52. GEOLOGICAL PHENOMENA OF AUVERGNE. 275 



Paris basin to have been elevated above the water during 

 the active state of neighbouring volcanoes, and that succes- 

 sive streams of lava flowed over its sedimentary deposits, 

 we should have a series of phenomena resembling those of 

 Auvergne ; with the exception, that the presence of marine 

 remains would denote that the basin had been filled with 

 salt water, and communicated with the sea. The facts 

 submitted to our notice appear to establish the following 

 sequence of physical events. 



1st. The elevation, after the deposition of the secondary limestones, 

 of the whole area of the primary rocks which form the founda- 

 tion of central France. 



2dly. A period of tranquillity, during which fresh-water lakes occu- 

 pied the irregular hollows of the district ; the neighbouring 

 country being inhabited by palseotheria, anoplotheria, and 

 other extinct mammalia, whose bones, together with the relics 

 of the then existing vegetation, and the shells of mollusca, be- 

 came enveloped in the tranquil depositions that were going 

 on in the lacustrine basins. 



3dly. Another elevation of the district took place, a new system of 

 lakes was established, and the country was again clothed with 

 forests, and was inhabited by deer, oxen, rhinoceroses, and 

 hyenas, many of whose skeletons became imbedded in the sedi- 

 ments of the waters. 



4thly. The volcanoes became active ; explosions took place through 

 hundreds of vents ; trachyte and basalt were ejected, and in 

 some places pierced the fresh-water deposits, while in others 

 they overspread them with sheets of lava. Vegetation still 

 flourished, and the remains of plants were entombed in the 

 volcanic products. 



5thly. Another period of tranquillity — the rivers and other water- 

 courses, dammed up or deranged by the lava currents, formed 

 new channels, and accumulated beds of gravel, sand, and clay. 

 Deer, horses, oxen, &c, with hyenas and other carnivora, in- 

 habited the district ; having for contemporaries terrestrial 

 mammalia of species which exist in Auvergne at the present 

 time. Volcanic eruptions succeeded, and continued till a com- 

 paratively recent period. 



Lastly. Streams and rivers of later date, and which still effect the 

 drainage of the country, began to wear away channels through 

 t2 



