1885.] SAND-PLAINS OF BELGIUM. 439 



of the whispering gallery. The slightest indentation in the sand is 

 immediately filled up by the fall of the particles above. Moving 

 waves are thus produced by the heavy tramp of a descending party ; 

 and the result of the dry sand is condensed and reverberated by the 

 circular conformation of the rocks around." 



V. — Moveraents in Sand-Buncs and Suhmerged Sand. 



When sand-dunes are not covered with vegetation, they are in a 

 state of constant flux, changing their aspect, changing their contour, 

 both their superficial contour and their linear contour, and their 

 position. 



The encroachment of the sea upon the coast, and the consequent 

 loss of land when the coast does not consist of hard rock, or is 

 protected by sufficient artificial means — by islands, or by its concave 

 outline — is a matter by no means so trifling as to be despised ; it is 

 especially extensive on those islands which often lie like advanced 

 posts i^rbtecting the mainland behind. Near Bruesterert on the 

 mainland of Pomerania, Hagen has lost upon an average a fathom 

 a year. The lighthouse on the island of Wangeroog in the German 

 Ocean, which was first built in the present century, it was found 

 necessary in the year 1850 to abandon and dismantle. The church 

 there, then protected so late as the year 1853 by a natural dune, is 

 at the present time in imminent and manifest danger, and the village 

 which only a few years ago was frecLuented as a bathing-place, stands 

 now in a great measure deserted; in the seventeen years from 1836 

 to 1853, the sea has advanced towards the village about eighty-five 

 feet every year. The fort Cantin in the French Gironde, distant 

 about two hours from Teste, was in 1754 built in a situation about 

 104 fathoms from the sea; so early as 1780 it was washed by the 

 waves. Corduan, in the mouth of the Gironde, belonged formerly 

 to the mainland. It is now an island, and has been long so. 



But there are far more numerous cases of the dunes advancing 

 inland on their landward side ; which advance is effected by a 

 transference of the sand particles from the windward to the land- 

 ward ridge. 



By the study of the sand wastes on the eastern shore of the 

 German Ocean, much may be learned in regard to the natural history 

 of sand drifts and dunes, and the phenomena accompanying their 

 formation and the laws regulating their contour and their move- 

 ments. But more still may be learned on this subject by extending 

 our sphere of observation and following a teacher who has gone 

 over the ground before us, leaving not only his footprints but his 

 observations and the observations of others, to which he has given 



