498 
DUNES OF PRUSSIA. 
chain is very various, and in some places it consists only of a 
single row of sand hills, while in others, it is more than six 
miles wide. The general rate of eastward movement of the 
drifting dunes is from three to twenty-four feet per annum. 
If we adopt the mean of thirteen feet and a half for the annual 
motion, the 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 unin¬ 
habitable 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 com¬ 
menced not much more than a hundred years ago. The 
Frische Nehrung is separated from the mainland by the 
Frische Haff, and there is but a narrow strip of arable land 
along its eastern borders. Hence its rolling sands have covered 
a comparatively small extent of dry land, but fields and vil¬ 
lages have been buried and valuable forests laid waste by 
them. The loose coast row has drifted over the inland ranges, 
which, as was noticed in the description of these dunes on a 
former page, were protected by a surface of different composi¬ 
tion, and the sand has thus been raised to a height which it 
could not have reached upon level ground. This elevation has 
enabled it to advance upon and overwhelm woods, which, upon 
a plain, would have checked its progress, and, in one instance, 
a forest of many hundred acres of tall pines was destroyed by 
the drifts between 1804 and 1827. 
Control of Dunes by Man. 
There are three principal modes in which the industry of 
* Andresen, Orn Klitformationem , pp. 56, 79, 82. 
