358 ON ALLUVIAL FORMATIONS. 



marsch and surrounded with dikes, the most considerable 

 are Pellworm and Nord Strand ; and among the Hal- 

 ligs, or those inhabited without dikes, the chief are Olant, 

 Nord-marsh, Langne, Groode, and Hooge. 



Such are the islands on this coast, in their present 

 state, now rendered permanent by the degree of perfec- 

 tion at which the art of dike-making is arrived. But, in 

 former times, though the original land was never attack- 

 ed by the sea, which, by adding to it new lands, soon 

 formed a barrier against its own encroachments, the lat- 

 ter, and the islands composed of the same materials, were 

 subject to great and sudden changes, very fatal to those 

 who were engaged to settle on them by the richness of 

 their soil, comparatively with the continental. The inha- 

 bitants, who continued to multiply on them during seve- 

 ral generations, were taught, indeed, by experience, that 

 they might at last be invaded by the element which was 

 incessantly threatening them ; but having as yet no know- 

 ledge of natural causes, they blindly considered those 

 that endangered them as supernatural, and for a long 

 time used no precautions for their own security. They 

 were ignorant of the dreadful effects of a certain associa- 

 tion of circumstances, rare indeed, but, when occurring, 

 absolutely destructive of these marsches. This associa- 

 tion consists of an extraordinary elevation of the level of 

 the North Sea, from the long continuance of certain 

 winds in the Atlantic, with a violent storm occurring 

 during the tides of the new or full moon ; for then the 

 sea rises above the level of all the marsches ; and before 

 they were secured against such attacks, the waves rolling 

 over them, .and tearing away the grass which had bound 

 their surface, they were reduced to the state of mere 



