Among the Forces | Page 8

this higher reservoir down to the bottom of the mine and weigh 25,000
pounds more than a like column that comes from the bottom to the top.
This extra 25,000 pounds is an extra force available to lift itself and the
other water out of the deep well, and they turn the greater force into a
pump and work it in the cylinder as if it were steam. It lifts not only the
water that works the pump, but the other water also out of the mine by
gravitation. So man gets the water out by pouring more water in.

THE HELP OF INERTIA
Since the time of David many boys have swung pebbles by a string, or
sling, and felt the pull of what we call a centrifugal (center-fleeing)
force. David utilized it to one good purpose. Goliath was greatly
surprised; such a thing never entered his head before. Whether a stone
or an idea enters one's head depends on the kind of head he has.
We utilize this force in many ways now. Some boys swing a pail of
milk over their heads, and if swung fast enough the centrifugal force
overcomes the force of gravitation, and the milk does not fall. That is
not utilizing the force. It often terrorizes the careful mother, anxious for
the safety of the milk.
But in the arts of practical life we do utilize this force, which is only
inertia.
Once it took a long time for molasses to drain out of a hogshead of
damp sugar. Now it is put into a great tub, with holes in the side, which
is made to revolve rapidly, and the molasses flies out. In the best
laundries clothes are not wrung out, to the great damage of tender
fabrics, but are put into such a tub and whirled nearly dry. So fifty
yards of woolen cloth just out of the dye vat--who could wring it? It is
coiled in a tub called a wizard, and whirled.
Muddy water is put through a process called clarification. It is the same,
except that there are no holes in the vessel. The heavier particles of dirt,

that would settle in time, take the outside, leaving perfectly clean water
in the middle. A perpendicular perforated pipe, with a faucet below,
drains off all the clear water and leaves all the mud. Milk is brought in
from the milking and put into a separator; whirl it, and the heavier milk
takes the outside of the whirling mass, and the lighter cream can be
drawn off from the middle. It is far more perfectly separated than by
any skimming.
A rotary snowplow slices off two feet of a ten-foot drift at each
revolution, and by centrifugal force flings it out of the cutting with a
speed that a hundred navvies or dagos cannot equal.

ONE PLANT HELP
A thousand acres of land on Cape Cod were once blown away. This
wind excavation was ten feet deep. It was not an extraordinary wind,
but extraordinary land. It was made of rock ground up into fine sand by
the waves on the shore.
In all the deserts of the world the wind blows the itinerant sand on its
far journeys. If the wind is moderate it heaps the sand up into little hills,
some of them six hundred feet high, around any obstruction, and then
blows the sand up the slanting face of the hill and over the top, where it
falls out of the wind on the leeward side. In this way the hill is always
traveling. In North Carolina hills start inland, and travel right on,
burying a house or farm if it be in the way, but resurrecting it again on
the other side as the hill goes on. Anyone may see these hills at the
south end of Lake Michigan, as he approaches Chicago, west of San
Francisco, all along up the Columbia River--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