ountains,
and, being soluble in water, they also come down the tiny railroad with
musical laughter. How can we separate them, so that the salt shall be
pure for our tables?

The other minerals are less avaricious of water than salt, so they are
precipitated, or become solid, sooner than salt does. Hence with nice
care the other minerals can be left solid on the bushes, while the salt
brine falls off. Afterward pure water can be turned on and these other
minerals can be washed off in a solution of their own. No fairies
could work better than those of solution and crystallization.

MORE GRAVITATION

At Hutchinson, Kan., there are great beds of solid rock salt four
hundred feet below the surface. Men want to get and use two thousand
barrels a day. How shall they get it to the top of the ground? They
might dig a great well--or, as the miners say, sink a shaft--pump out
the water, go down and blast out the salt, and laboriously haul it up
in defiance of gravitation. No; that is too hard. Better ask this
strong gravitation to bring it up.

But does it work down and up? Did any one ever know of gravitation
raising anything? O yes, many things. A balloon may weigh as much as
a ton, but when inflated it weighs less than so much air; so the
heavier air flows down under and shoulders it up. When a heavy weight
and a light one are hung over a pulley, the light one goes up because
gravity acts more on the other. Water poured down a long tube will
rise if the tube is bent up into a shorter arm.

Exactly. So we bore a four-inch hole down to the salt and put in an
iron tube.

We do not care about the water. It is no bother. Then inside of this
tube we put a two-inch tube that is a few feet higher. Now pour water
down the small longer tube. It saturates itself with salt, and comes
flowing over the top of the shorter tube as easily as water runs down
hill. Multiply the wells, dry out the water, and you have your two
thousand barrels of salt lifted every day--just as easy as thinking!

We want a steady, unswerving force that will pull our clock hands with
an exact motion day and night, year in and year out. We hang up a
string, and ask gravitation to take hold and pull. We put on some lead
or brass for a handle, to take hold of. It takes hold and pulls,
unweariedly, unvaryingly, and ceaselessly.

It turns single water-wheels with a power of more than twelve hundred
horses.

It holds down houses, so