Now a column of this water one foot square can be
taken from 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.
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