THE TERTIARY SYSTEM. 747 



rounding country, it would inevitably have been transported into the lakes, and deposited 

 at their bottom, with the other detritus of the adjoining land. But long before the 

 depositions from the lakes were completed, and their waters ceased to distinguish the 

 physical geography of Auvergne, the subterranean forces came into action, and masses 

 of lava and tufa were erupted, whose material intermingles with some of the newer sub- 

 divisions of the lacustrine deposits. Mr. Lyell remarks that, in the gravelly and sandy 

 beds of Lake Superior, no pebbles of modern volcanic rocks can be included, since there 

 are none of these at present in the district ; but, if igneous action should break out in 

 that country, and produce masses of lava and scoriae, the deposition of gravel and sand 

 might still continue as before, but, in addition, there would be an intermixture of the 

 volcanic ejections carried down into the bed of the lake by the numerous rivers and 

 torrents that pour into it. We may conclude, therefore, that though we know not the 

 era when the craters of Auvergne ceased their eruptions, the period of their activity goes 

 back to an interval ages before the present epoch, when central France was a region of 

 lakes, the site of Paris an arm of the sea, and the palaeotherium inhabited the contiguous 

 lands. To alterations produced in the general level of the country by the long-continued 

 play of the subterranean fires, we are probably to attribute the drainage of the lakes. 



2. Miocene period) or Median Tertiary Strata. The deposits included in this division 

 are characterised by their fossil contents presenting a greater admixture of extant with 

 extinct species than the eocene beds, and, by their overlying position when the latter 

 are present, denoting their later accumulation. They are far more extensive, likewise, 

 occupying an immense space of the area of Europe. In the ancient province of Touraine, 

 what are provincially called the " Faluns," or marls of the Loire, are miocene tertiaries. 

 They occur in the basin of that river, and consist of an extensive formation of marl 

 beds, a series of marine strata, resting upon the upper fresh-water group of the Paris 

 basin. Nearly four hundred species of shells found in this district have been compared 

 with those common to the deposits around the capital, and scarcely more than twenty are 

 identical, a sufficient evidence of the entire distinctness of the two tertiary groups. The 

 Touraine marls contain terrestrial and river shells, as well as marine, with the remains 

 of land quadrupeds, and vertebrated inhabitants of the ocean, intimating that here 

 anciently, the waters of a river encountered the sea in an estuary, the one drifting down 

 the fluviatile and land organisms, and the other washing up the oceanic forms, to be 

 entombed in the strata deposited by the estuary, which passed away with the elevation 

 of its bed. The bones of the mastodon, an extinct genus, the hippopotamus, rhino- 

 ceros, tapir, and horse of extinct species, intermingle with those of whales, and other 

 cetaceous animals. The former evince considerable fracture, and rolling, as if by a long 

 drift along a river course, and in connection with the latter are coated with marine 

 polypi, from which it may be inferred that, for a lengthened interval, they were covered 

 with a tranquil and stationary sea. A notice of the above fossil mammalia will be more 

 appropriate on a subsequent page. 



Tertiary deposits containing shells analogous to or identical with those of Touraine, 

 referable, therefore, to the same age, are much more extensive in the south of France, 

 in the basin of the Garonne, and in the country intervening between that river and the 

 Pyrenees. They occur, also, in the neighbourhood of Turin, in the low country of Switzer- 

 land, along the course of the Rhine, and occupy a large part of the basins of Vienna and 

 Styria, the plains of Bohemia and Hungary, with the plateaus of Volhynia, and Podolia. 



Besides an immense number of shells, belonging to 1418 species, according to the 

 catalogues of M. Deshayes, by far the greater portion of which are extinct, the strata of 

 the miocene period present many vegetable remains, the silicified stems, fruits, and 

 leaves of palms, often of great beauty, and very perfectly preserved. A shell, and 



