496 
DUNES OF GASCONY. 
conies in the dunes is, in this way, not unfrequently a cause of 
their destruction and of great inj ury to the fields behind them. 
Drifts, and even inland sand hills, sometimes result from break¬ 
ing the surface of more level sand deposits, far within the 
range of the coast dunes. Thus we learn from Staring, that 
one of the highest inland dunes in Friesland owes its origin to 
the opening of the drift sand by the uprooting of a large oak.* 
Great as are the ravages produced by the encroachment of 
the sea upon the western shores of continental Europe, they 
have been in some degree compensated by spontaneous marine 
deposits at other points of the coast, and we have seen in a 
former chapter that the industry of man has reclaimed a large 
territory from the bosom of the ocean. These latter triumphs 
are not of recent origin, and the incipient victories which paved 
the way for them date back perhaps as far as ten centuries. 
In the mean time, the dunes had been left to the operation of 
the laws of nature, or rather freed, by human imprudence, 
from the fetters with which nature had bound them, and it is 
scarcely three generations since man first attempted to check 
their destructive movements. As they advanced, he unresist¬ 
ingly yielded and retreated before them, and they have buried 
under their sandy billows many hundreds of square miles of 
luxuriant cornfields and vineyards and forests. 
Dunes of Gascony. 
On the west coast of France, a belt of dunes, varying in 
width from a quarter of a mile to five miles, extends from the 
Adour to the estuary of the Gironde, and covers an area of 
three hundred and seventy-five square miles. When not fixed 
by vegetable growths, they advance eastward at a mean rate 
of about one rod, or sixteen and a half feet, a year. We do 
not know historically when they began to drift, but if we sup¬ 
pose their motion to have been always the same as at present, 
they would have passed over the space between the sea coast 
* De Bodem van Nederland , i, p. 425. 
