driven soil, gathered from the sides of bare hills and mountains,
fills many valleys of China with a fine, hard-packed material called
"loess." In some places it is hundreds of feet deep. The people dig into
the side of a hill of this loess and carry out the diggings, making
themselves homes, of many rooms, with windows, doors, and solid walls
and floors, all in one solid piece, like the chambered house a mole
makes underground in the middle of a field. So compact is the loess that
there is no danger of a cave-in.

The hills of sand piled up on the southern shore of Lake Michigan, and
at Provincetown, at the toe of Cape Cod, are the work of the wind. On
almost any sandy shore these "dunes" are common. The long slope is
toward the beach that furnishes the sand. The wind does the building. Up
the slope it climbs, then drops its burden, which slides to the bottom
of an abrupt landward steep. There is a gradual movement inland if the
strongest winds come from the water. The shifting of the dunes threatens
to cover fertile land near them. In the desert regions, the border-land
is always in danger of being taken back again, even though it has been
reclaimed from the desert and cultivated for long years.

Besides tearing down, carrying away, and building up again the fragments
of the earth's crust, the wind does much that makes the earth a pleasant
planet to live on. It drives the clouds over the land, bringing rains
and snows and scattering them where they will bless the thirsty ground
and feed the springs and brooks and rivers. It scatters the seeds of
plants, and thus plants forests and prairies and lovely mountain slopes,
making the wonderful wild gardens that men find when they first enter
and explore a new region. The trade winds blow the warm air of the
Tropics north and south, making the climate of the northern countries
milder than it would otherwise be. Sea winds blow coolness over the land
in summer, and cool lake breezes temper the inland regions. From the
snow-capped mountains come the winds that refresh the hot, tired worker
in the valleys.

Everywhere the wind blows, the life-giving oxygen is carried. This is
what we mean when we speak of fresh air. Stagnant air is as unwholesome
as stagnant water. Constant moving purifies both. So we must give the
wind credit for some of the greatest blessings that come into our lives.
Light and warmth come from the sun. Pure water and pure air are gifts
the bountiful earth p