Excavation of Valleys. 45 



species of the genera Mastodon, Elephant, Rhinoceros, Hippo- 

 potamus, Tapir, Bear, Hyaena, Stag, and others.* These qua- 

 drupeds, therefore, inhabited this district long before the more 

 recent volcanic cones and lavas of Auvergne were in existence, 

 ere yet the valleys had attained their present depth, and even 

 before the fires of the ancient volcanoes of Mont Dor had be- 

 come extinguished. 



In concluding this article, we may observe, that Auvergne, 

 Velay, and the Vivarais, throw peculiar light on the theory of 

 valleys, because the volcanic rocks having been introduced upon 

 the surface successively, and sometimes at intervals immensely 

 distant from each other, have preserved portions of the surface 

 in the state in which it existed at those several periods. Hence 

 it becomes impossible to confound the effects of erosive action 

 of one epoch with those of another. But for this circumstance, 

 events the most remote in point of time, — the waste of floods or 

 violent torrents of most distinct eras, would have been regarded 

 as simultaneous. Thus the conglomerates, several hundred feet 

 thick, on which rests nearly the whole series of alternating beds 

 of trachyte, basalt, and scorias of Mont Dor, would have re- 

 mained without any distinct line of separation from the latest 

 alluvions ; and the same would, in many cases, have happened 

 in Cantal, although we have now reason to conceive that the 

 oldest lava of Etna is not more ancient, as compared with the 

 latest, than are the several masses of transported materials last 

 alluded to. If the debris of all these various periods were now 

 strewed over the country at the various elevations where they 

 are at present observed, and if we possessed not the means, 

 which we now have, of pointing out their different ages, they 

 would present the appearance of having been the result of one 

 sudden and dreadful catastrophe, whereby rocks of different 



" About forty species of quadrupeds will be described by MM. Croizet 

 and Jobert, when their splendid and valuable work is completed, from the al- 

 luvions of Mont Perrier alone. Similar remains are not wanting, it appears, 

 near Puy en Velay ; for M. Bertrand Roux has just informed us, that he has 

 obtained from a locality first pointed out by Dr Hibbert of Edinburgh, fossil 

 bones and teeth belonging to the genera Rhinoceros, Hyaena, Stag and 

 others, plates of which will shortly be published. Their geological position 

 is very interesting, since they were found in volcanic scoriae, covered by one 

 of the most modern lava-currents of that district. 



