152 RAMBLES OF A NATURALIST. 



disappeared under the incessant action of the waves, 

 and the cliffs had retreated at least 150 feet farther 

 inland. The serpentine, from its extreme hardness, 

 had alone been able to resist this continued action of 

 the waters, and it now stood forth in the midst of the 

 beach as an evidence of the destructive power of the 

 waves. M. de Collegno, who had made his obser- 

 vations long before my visit, estimates the annual 

 encroachment of the sea to be about ten feet.* 



This fact, which is observable in a more or less 

 marked degree along the whole length of the coast, 

 depends upon the very nature and structure of the 

 rocks. The cliffs here are generally formed of a 

 marly or sandy limestone, which becomes disintegrated 

 under the action of atmospheric agents. It is almost 

 everywhere divided into laminae, which are occasion- 

 ally separated by layers of clay. This earth on 

 being carried away by the waters becomes changed 

 into a sort of foliaceous crust, which yields to the 

 slightest shock of the waves ; and, indeed, from the 

 Chambre d'Amour as far as the bay of Saint-Jean- 

 de-Luz the whole line of the shore affords ample 

 proof of a gradual and progressive disintegration. 

 On every side deep crevices, crumbling earth, and 



* Bulletin de la Societe geologique de France, 1839. M. de Collegno, 

 being implicated in the political troubles of Piedmont, was obliged 

 to leave his country. He learned, however, to seek consolation for 

 the pains of exile in the pursuits of science, and during his residence 

 in France he was appointed professor in the Faculty of Sciences at 

 Bordeaux. Having been subsequently recalled to his native country, 

 he continued to take an active and earnest part in politics, and he even 

 returned to Paris as the representative of the country from which he 

 had once been banished. 



