HYDROGEAPHY. 



459 



same time it menaces them with terrible irruptions, and continually gnaws at their 

 coasts. 



Incessant are the struggles which the Dutch maintain against the encroach- 

 ments of the ocean and the floods caused by their rivers. So frequent were 

 irruptions of the sea in the eleventh and twelfth centuries, that many of the 

 inhabitants left their homes in despair, and sought an asylum elsewhere. It 

 was about this period that the series of irruptions began wdiich ended in the 

 destruction of the isthmus which formerly connected North Holland with Fries- 

 land, converted Lake Flevo into the Zuider Zee, and broke up a continuous coast- 

 line into a fringe of islands. Terrible were the floods of the thirteenth century. 



Fig. 254. — The Site of the Biesbosch prior to the Spring Tide of St. Elizabeth. 



From a Map in the Archives of Dordrecht. 



Scale 1 : 220,000. 



. 2 ûliles. 



The sea then invaded Friesland, forming the Lauwer Zee, and only spared a shred 

 of land — the island of Schiermonnikoog — to mark the former extent of the coast. 

 In 1421 the fearful spring tide of St, Elizabeth burst through the embankments, 

 and converted a fertile district near Dordrecht into a labyrinth of islands, now 

 known as the Biesbosch (see Figs. 252 and 254). 



Even in the present century the sea has repeatedly invaded the land, not- 

 withstanding the formidable barriers erected to exclude it. In 1825 it overflowed 

 the southern portion of the peninsula of Holland, overwhelming forty villages. 

 When the land had been recovered the putrefying remains of human beings and 

 animals spread a pestilence around them. Marken, an island ofl" that coast, may 

 be likened to a vessel in a stormy sea, defended by a board hardly 3 feet in 



