--the sand having come on the wings of the wind from the coast.

But to see the whole visible world on a march one needs to go to a
really large desert. The Pyramids and the Sphinx have been partly
buried, and parts of the valley of the Nile threatened, by hordes of
sand hills marching in from the desert; cities have been buried and
harbors filled up. Many of the harbors of the ancient civilizations
are mere miasmatic marshes now. This is partly in consequence of the
silt brought in by the rivers; but where the rivers do not flow in it
is because the sand blows in along the shore. Harbors are especially
endangered when their protection from the waves consists of a bank of
sand, as on Cape Cod and the Sandy Hook below the Narrows of the harbor
of New York.

How can man combat part of the continent on the move, driven by the
ceaseless powers of the air? By a humble plant or two. The movement
of the sand hills that threaten to destroy the marvelous beauty of the
grounds of the Hotel del Monte at Monterey is stopped by planting dwarf
pines. The sand dunes that prevent much of Holland from being
reconquered by the sea are protected with great care by willows, etc.,
and the coast sands of parts of eastern France have been sown with sea
pine and broom.

The tract of a thousand acres on Cape Cod had been protected by humble
beach grass. Some careless herder let the cows eat it in places, and
away went part of a township. It is now a punishable crime on Cape Cod
to destroy beach grass.

GAS HELP

This refers to more than stump speech-making. The old Romans drove
through solid rock numerous tunnels similar to the one for draining
Lago de Celano, fifty miles east of Rome. This one was three and a
half miles long, through solid rock, and every chip cost a blow of a
human arm to dislodge it. Of course the process was very slow.

We do works vastly greater. We drive tunnels three times as long for
double-track railways through rock that is held down by an Alp. We use
common air to drill the holes and a thin gas to break the rock. The
Mont Cenis tunnel required the removal of 900,000 cubic yards of rock.
Near Dover, England, 1,000,000,000 tons of cliff were torn down and
scattered over fifteen acres in an instant. How was it done? By gas.

There are a dozen kinds of solids which can be handled--some of them
frozen, thawed, soaked in water, with impunity--but let a spark of fire
touch them and they break