The mirror., 1919-12-18
MI 81 Combating Ocean Sands

1t is calculated that nine-tenths of
the coasts of the world are covered
with sand. What is the origin of
this sand and to what circumstances
is its abundance due? Men of science
Rave explained this in part by saying
|that it is due to the erosive effect of
/ the waves upon the rocks, but it is
generally admitted that this is not suf-
fcent to account for the vast quantity
of sand that borders our beaches. I'm
doubtedly very considerable portion
represents the material carried to and
toward the ocean by the storms and
glaciers of the Ice Age.
The distribution of sand on the
coast depends, in the first place, on
marine currents and the Topographic
cal aspects of the coasts themselves.
Where there is no protection in the
shape of cliffs the coasts are covered
with enormous quantities of sand, but
its advance is checked by plants and
vegetable growths. Sprouts, trailing
vines, or dragging roots serve the pur
pose of Keeping the sand in place and
giving consistency to the appearance
of the average beach. Of these vege-
table growths, those are calculated tc
serve the purpose best which are most
abundant and whose resisting power
is strongest. In the time of Eliza
beth law was passed prohibiting the
destruction of such beach plants, as
| they tended to keep back the sand
otherwise carried by wind and rain to
the detriment of crops.
1t was thus early recognized that
! plant life had an influence not to be
despised in the formation of sand hills
such as one sees in such plenty on the
coasts of England and Flanders.
These banks, called "dunes," are
either stationary or moving, as the
case may be. When the sand de-
posted on the coast by the waves is
not excessive and the wind blows in
termittently one may see behind the
sand hill the vegetable growth that is
giving solidity to the mass from its
roots up. In this way are formed the
stationary dunes. When the vegeta-
ton is extended as far as the sea the
dune grows in this direction and the
curious spectacle is presented of the
ocean receding before the advance of
the coast.
A well-known building in South
port, England, was built on a beach
formed in just this way. The NOV
ing dunes, although the same in origin
as the stationary ones, owe their spe-
cial characteristic to their great mass
and the direction and constancy of
the wind, which prevents their find
ing base strong enough to constitute
hold on the earth. These dunes are
tossed about, often advancing into the
interior over cultivated ground to the
despair of farmers.
On the coasts of Gascony there are
points where the dunes push forward
more than four yards annually. In
1880 the advance of sand upon the
land of Bordeaux was the occasion of
despair to horticulturists and crop
growers, and the engineer, Bremontier,
made himself famous by converting
movable dunes into stationary ones.
The task was undertaken to form a
wall against the sand invasion by
making a palisade of the dunes lit
tie more than a meter high and put
ting planks between each pair. When
the sand swept over the boards it
had to break up its volume in the ef-
fort, and little by little a stationary
dune would form with an inclination
of from seven to twelve degrees in
the direction of the sea. Behind this
palisade was conveniently disposed a
| wide zone of the harder shrubs.
France is by no means the only
country that has undertaken to con-
test the advance of sand. In Holland
and also in Denmark the problem has
been studied for centuries.-Selected.