§ 59. RETROSPECT. 



287 



tions of Mont Dome. The succeeding period of tranquillity 

 is recorded in characters alike intelligible. The slow 

 deposition of calcareous mud — the incrustation of successive 

 generations of aquatic insects, Crustacea, mollusca, and 

 infusoria — the imbedding of the bones of mammalia, birds, 

 and reptiles — the accumulation of lignite and other vegeta- 

 ble matter — are data from which we may restore the ancient 

 country of Central France. 



It was a region encircled by a chain of granite moun- 

 tains, watered by numerous streams and rivulets, and 

 possessing lakes of vast extent. Its soil was covered with 

 luxuriant vegetation, and peopled by palaeotheria, anoplo- 

 theria, and other terrestrial mammalia ; the crocodile and 

 turtle found shelter in its marshes and rivers ; aquatic 

 birds frequented its fens, and sported over the surface of 

 its lakes ; while myriads of insects swarmed in the air, and 

 passed through their wonderful metamorphoses in the 

 waters. In a neighbouring region,* herds of ruminants 

 and other herbivora, of species and genera now no more, 

 with birds and reptiles, were the undisturbed occupants of 

 a country abounding in palms and tree-ferns, and having 

 rivers and lakes, with gulfs which teemed with the inhabi- 

 tants of the sea ; but to this district the fiery torrents of 

 the volcano did not extend. But to return to Auvergne ; 

 a change came over the scene — violent eruptions burst 

 forth from craters long silent — the whole country was laid 

 desolate — its living population was swept away — all was 

 one vast waste, and sterility succeeded to the former 

 luxuriance of life and beauty. Ages rolled by — the mists 

 of the mountains and the rains produced new springs, tor- 

 rents, and rivers — a fertile soil gradually accumulated over 

 the cooled lava currents and the beds of scoriae, to which 

 the sediments of the ancient lakes, borne down by the 

 streams, largely contributed. Another vegetation sprang 

 * The Paris basin. 



