148 RAMBLES OF A NATURALIST. 



It is well known that our globe has only gradually 

 attained its present configuration. Before it pre- 

 sented the elevations and depressions which are now 

 figured on our geographical maps, its surface under- 

 went numerous convulsions which were separated 

 from one another by long intervals of repose. During 

 these periods of rest, whole tracts of land were 

 heaped up upon one another, and strata superposed on 

 other strata at the bottom of the vast seas of those 

 geological periods, but when the moment of a new 

 cataclysm arrived, the forces which had been tem- 

 porarily dormant in the centre of the globe were 

 again awakened, and thrusting the subjacent rocks 

 through more recent deposits, caused hitherto sub- 

 merged continents and new chains of mountains to 

 be upheaved. Vast dislocations, twistings, ruptures, 

 and disturbances of strata accompanied each of these 

 upheavals, and it is from these disturbed masses, and 

 the relations by which they are connected, that 

 modern science has succeeded in tracing, with an 

 almost incredible degree of certainty, the history of 

 these vast revolutions. 



At the period when the land surrounding the 

 Bay of Biscay first appeared, Europe generally, 

 and France more especially, bore no resemblance to 

 their present condition. Twelve upheavals or cata- 

 clysms had already taken place.* Auvergne, the 



accompanied by a magnificent atlas, has become a standard work 011 

 the subject to which it refers. 



* These numbers have been given by M. Elie de Beaumont in one 

 of his recent publications on the subject. Article SYSTEMES DE 

 MONTAGNES in the Dictionnaire Universel (THistoire Naturelle. 



We ought however, to observe that the author himself merely 



