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.