ENCROACHMENTS OF THE SEA. 
493 
bers of Mytilus edulis. Could we obtain a deep section of tlie 
bottom, we should find beds of Ostrea edulis and Cardium 
edule , then a layer of Zostera marina with fresh-water fish, 
and then a bed of Mytilus edulis. If, in course of time, the 
new channel should be closed, the brooks would fill the lagoon 
again with fresh water; fresh-water fish and shell fish would 
reappear, and thus we should have a repeated alternation 
of organic inhabitants of the sea and of the waters of the 
land. 
u These events have been accompanied with but a com¬ 
paratively insignificant change of land surface, while the for¬ 
mations in the bed of this inland sea have been totally revo¬ 
lutionized in character.” * 
Coasts of Schleswig-Holstein , Holland , and France. 
On the islands on the coast of Schleswig-Holstein, the ad¬ 
vance of the sea has been more unequivocal and more rapid. 
Near the beginning of the last century, the dunes which had 
protected the western coast of the island of Sylt began to roll 
to the east, and the sea followed closely as they retired. In 
1757, the church of Han turn, a village upon that island, was 
obliged to be taken down in consequence of the advance of the 
sand hills; in 1791, these hills had passed beyond its site, the 
waves had swallowed up its foundations, and the sea gained so 
rapidly, that, fifty years later, the spot where they lay was 
seven hundred feet from the shore, f 
The most prominent geological landmark on the coast of 
Holland is the Huis te Britten, Arx Britannica , a fortress 
built by the Homans, in the time of Caligula, on the main 
land near the mouth of the Rhine. At the close of the seven¬ 
teenth century, the sea had advanced sixteen hundred paces 
beyond it. The older Dutch annalists record, with much pa¬ 
rade of numerical accuracy, frequent encroachments of the sea 
* Foeohhammee, Geognostische Studien am Meeres-Ufer. Leonhard und 
Bbonn, Jahrbuch , 1841, pp. 11, 13. 
f Andresen, Om Klitformationen , pp. 68, 72. 
