GENEEAL FEATUEES, ETC. 



389 



now to fill up altogether. The formidable fortifications of Sluis, which no longer 

 defend anything, the fine municipal buildings of Dannne, and the deserted streets 

 of Bruges clearly result from the great changes which have taken place in 

 Flanders. A canal 13 feet in depth now joins Bruges to Ostend, but has not 

 brought back the commercial activity of former days. 



But whilst the surface currents of the sea transport the sand and mud which 

 form the dunes and fill up the estuaries, the under-currents continue their work of 

 erosion. Peat containing oak-leaves, hazel nuts, and even broom seeds is almost 

 daily cast up on the strand. On the beach of Heyst a fossil shell of eocene age 

 {Cardita planicosta) is found, together with the remains of species still living in 



Fig. 219.— GrKOINS AT Clankenmîerghb 

 Scale 1 : 1 20.000. 



Depth down to ?{■ Fiths. 



iMile. 



Dipth beysnd 2j- Fatllt, 



the North Sea. There can be no doubt that the sea has encroached within 

 historical times upon the coast of Belgian Flanders, as is clearly shown by the 

 evidence collected by the brothers Belpaire. At Ostend there exist abundant traces 

 of marine erosion. The d}ke upon which the old citadel of that town was 

 constructed advances now 600 feet beyond the general contour of the coast, which 

 has been washed away on either side of it. The coast of Belgium, since its bays 

 have become silted up, is singularly rectilinear in its profile, but, to defend it against 

 the encroachments of the sea, it was necessary, in many localities, to construct a 

 large number of groins. Nowhere in Europe are such groins more numerous than 

 between Blankenberghe and Heyst, where they replace Duke John's old dyke. 

 The shore of Belgium is exceedingly poor in shells, owing to the absence of rocks to 



