150 RAMBLES OF A NATURALIST 



formed the central axis of these mountains, uplifted 

 the chalk strata of which we have just spoken. On 

 either side of this chain we find that the strata are 

 inclined in a direction parallel to this axis, and they 

 constitute all the littoral rocks of the Basque pro- 

 vinces. 



If the geological phenomena that occurred round 

 the Bay of Biscay had stopped at this epoch, their 

 explanation would have presented very slight diffi- 

 culties; but such is by np means the case. The 

 chalk strata which have been raised and thrust to 

 the south by the appearance of the Pyrenees, and 

 retained towards the north by the ancient formations 

 on which they rested, had been bent in the middle, 

 and hollowed into a vast depression, which had been 

 immediately filled up by the waves. The Pyrenees 

 were thus separated from France by a broad arm of 

 the sea, which extended to the west from Biarritz to 

 La Gironde, and to the east from Carcassonne to the 

 mouth of the Rhone. Tertiary strata were suc- 

 cessively deposited in this basin, and many distin- 

 guished geologists, guided principally by the study of 

 the fossils of the district, have referred the neigh- 

 bourhood of Biarritz from the Chambre d'Amour to 



upheaval. M. de Beaumont admits that the Alps, such as we see 

 them in the present day, have been as it were modelled by at least 

 five upheavals, and the Vosges by as many as twelve. According 

 to M. Durocher we find in the Pyrenees superposed traces of seven 

 successive cataclysms. Often, in a somewhat limited space, different 

 systems of mountains, differing in age and direction, appear to have 

 been accumulated, as it were at will. Thus MM. Boblaye and 

 Virlet recognised in the More a as many as nine distinct upheavals. 

 Article SYSTEMES DE MONTACNES. 



