590 DUNES OF PRUSSIA. 
A range of dunes extends along the whole western coast of 
Jutland and Schleswig-Holstein, and the movement of these 
sand-hills was formerly, and at some points still is, very de- 
structive. The rate of eastward movement of the drifting 
dunes varies from three to twenty-four feet per annum. If we 
adopt the mean of thirteen feet and a half for the annual mo- 
tion, these dunes have traversed the widest part of the belt in 
about twenty-five hundred years. Historical data are wanting 
as to the period of the formation of these dunes and of the 
commencement of their drifting; but there is recorded evi- 
dence that they have buried a vast extent of valuable land 
within three or four centuries, and further proof is found in 
the fact that the movement of the sands is constantly uncover- 
ing ruins of ancient buildings, and other evidences of human 
occupation, at points far within the present limits of the 
uninhabitable desert. Andresen estimates the average depth 
of the sand deposited over this area at thirty feet, which would 
give a cubic mile and a half for the total quantity.* 
The drifting of the dunes on the coast of Prussia commenced 
not much more thana hundred years ago. The Frische Neh- 
rung is separated from the mainland by the Frische Haff, and 
there is but a narrow strip of arable land along its eastern bor- 
ders. Hence its rolling sands have covered a comparatively 
small extent of dry land, but fields and villages have been 
buried and valuable forests laid waste by them. The loose 
conforming nearly to the slope of the dunes, while on the north-east and 
south the inclination of their beds is very gradual. The greatest depth of 
these pools corresponds to that of the sea ten miles from the shore. Is it 
possible that the weight of the sands has pressed together the soil on which 
they rest, and thus occasioned a subsidence of the surface extending beyond 
their base ? 
A more probable explanation of the fact stated in the note is suggested 
by Elisée Reclus, in an article entitled Le Littoral de la France, in the Revue 
des Deux Mondes for September 1, 1864, pp. 193, 194. This able writer be- 
lieves such pools to be the remains of ancient maritime bays, which haye been 
cut off from the ocean by gradually accumulated sand banks raised by the 
waves and winds to the character of dunes. 
* ANDRESEN, Om Klitformationen, pp. 56, 79, 82. 
