EEOSION OF CLIFFS. 147 



' The Straits of Dover are being continually enlarged by tbe action 

 of atmospheric influences, the waves, and the current which flows 

 from the Channel into the North Sea. The patient researches of 

 M. Thome de Gamond, an engineer to whom we owe the fine 

 project of the international tunnel between France and England, 

 have proved that the clifl* of Grris-Nez, the nearest point of the 

 French coast to Great Britain, loses on an average more than 27 

 yards per century. If in former ages the progress of erosion was 

 not more rapid, it would be about 60,000 years before the present 

 epoch that the isthmus connecting England with the continent was 

 broken by the pressure of the waves. Nevertheless, it is impossible 

 to indicate any date^ since at this place the ground has sunk and 

 risen at various intervals ; ancient beaches four or five yards above 

 the present level of the sea, as well as submerged forests, testify to 

 these successive oscillations.* 



Along the coast of France^ to the east of Cape Antifer, the 

 pebbles resulting from the denudation of the clifls are continually 

 advancing towards the mouth of the Somme. Arrested at about 6 

 miles beyond these last flinty clifls, by the promontory of Hourdel, 

 so named from the dash (Jieurt, Fr.) of the waves, they are subse- 

 quently taken up by the current which runs towards the Strait. 

 Triturated more and more, they travel from sand-bank to sand-bank, 

 and after having passed the Strait, are deposited in beds of mud either 

 on the surface of the innumerable banks of the North Sea_, or on the 

 coasts of Flanders, Holland, and eastern England. It is these deposits, 

 which are called by the expressive name of gain de flot (' winnings 

 from the waves ') in the neighbourhood of the Channel. The 10 millions 

 of cubic yards of fragments taken annually from the cliff's of Sussex 

 and Kent, as well as from those of Calvados and the Pays de Caux, 

 are carried back to the coasts of the northern countries, and it is at the 

 expense of the shores of the Channel that the polders of Holland and 

 the fens of Norfolk and Lincolnshire are formed. In consequence 

 of this double work of erosion at one point and deposit on another, 

 the shores situated to the north of the Straits present a perfect con- 

 trast with the coasts of the Channel. While the cliffs of France and 

 England, on the borders of this sea, are cut into concave bays, the 

 beaches which stretch to the north of the Straits of Dover uniformly 

 exhibit a convex arrangement. The waves give back in sand and 

 mud what they have taken in rocks and boulders, t 



* Day, Geological Magazine^ 1866. 



t Marclial, Annales des Fonts et Chausees, ler sem. p. 204. 



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