Among the Forces - Henry White Warren (books for 8th graders TXT) 📗

down into great pans, needing only a little evaporation by boiling to become beautiful salt again, white as the snows of December.

There are other minerals besides salt in the beds in the mountains, 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 that they are not blown away. It was made to serve man, and it works without a grumble.

Thus the higher force in nature always prevails over the lower, and the greater amount over the less amount of the same force. What is the highest force?


THE FAIRY PULLS GREAT LOADS

Far back in the hills west of Mauch Chunk, Pa., lie great beds of coal. They were made under the sea long ages ago, raised up, roofed over by the Allegheny Mountains, and kept waiting as great reservoirs of power for the use of man.

But how can these mountains be gotten to the distant cities by the sea? Faith in what power can say to these mountains, "Be thou removed far hence, and cast into the sea?" It is easy.

Along the winding sides of the mountains have been laid two rails like steel ribbons for a dozen miles, from the coal beds to water and railroad transportation. Put a half dozen loaded cars on the track, and with one man at the brake, lest gravitation should prove too willing a helper, away they go, through the springtime freshness or the autumn glory, spinning and singing down to the point of universal distribution.

On one occasion the brake for some reason would not work. The cars just flew like an arrow. The man's hair stood up from fright and the wind. Coming to a curve the cars kept straight on, ran down a bank, dashed right into the end of a house and spilled their whole load in the cellar. Probably no man ever laid in a winter's supply of coal so quickly or so undesirably.

But how do we get the cars back? It is pleasant sliding down hill on a rail, but who pulls the sled back? Gravitation. It is just as willing to work both ways as one way.

Think of a great letter X a dozen miles long.

Lay it down on the side against three or four rough hills. Bend the X till it will fit the curves and precipices of these hills. That is the double track. Now when loaded cars have come down one bar of the X by gravity, draw them up by a sharp incline to the upper end of the other bar, and away they go by gravity to the other end. Draw them up one more incline, and they are ready to take a new load and buzz down to the bottom again.

I have been riding round the glorious mountain sides in a horseless, steamless, electricityless carriage, and been delighted to find hundreds of tons of coal shooting over my head at the crossings of the X, and both cars were drawn in opposite directions by the same force of gravity in the heart of the earth.

If you do not take off your hat and cheer for the superb force of gravitation, the wind is very apt to take it off for you.


THE FAIRY DRAWS GREATER LOADS

Pittsburg has 5,000,000 tons of coal every year that it wishes to send South, much of it as far as New Orleans--2,050 miles. What force is sufficient for moving such great mountains so far? Any boy may find it.

Tie a stone to the end of a string, whirl it around the finger and feel it pull. How much is the pull? That depends on the weight of the stone, the length of the string, and the swiftness of the whirl. In the case of David's sling it pulled away hard enough to crash into the head of Goliath. Suppose the stone to be as big as the earth (8,000 miles in diameter), the length of the string to be its distance from the sun (92,500,000 miles), and the swiftness of flight the speed of the earth in its orbit (1,000 miles a minute). The pull represents the power of gravitation that holds the earth to the sun.

If we use steel wires instead of gravitation for this purpose, each strong enough to support half a score of people (1,500 pounds), how many would it take? We would need to distribute them over the whole earth: from pole to pole, from side to side, over all the land and sea. Then they would need to be so near together that a mouse could not run around among them.

Here is a measureless power. Can it be gotten to take Pittsburgh coal to New Orleans? Certainly; it was made to serve man. So the coal is put on great flatboats, 36 x 176 feet, a thousand tons to a boat, and gravitation takes the mighty burden down the long toboggan slide of the Ohio and Mississippi Rivers to the journey's end. How easy!

One load sent down was 43,000 tons. The flatboats were lashed together as one solid boat covering six and one half acres, more space than a whole block of houses in a city, with one little steamboat to steer. There is always plenty of power; just belt on for anything you want done. This is only one thing that gravitation does for man on these rivers. And there are many rivers. They serve the savage on his log and the scientist in his palace steamer with equal readiness.


THE FAIRY WORKS A PUMP HANDLE

The Slave of the Ring could take Aladdin into a cave of wealth, and by speaking the words, "Open Sesame," Ali Baba was admitted into the cave that held the treasures of the forty thieves. But that is very little. I have just come from a cave in Virginia City, Nev., from which men took $120,000,000.

In following the veins of silver the miners went down 3,500 feet--more than three fifths of a mile. There it was fearfully hot, but the main trouble was water. They had dug a deep, deep well. How could they get the water out? Pumps were of no use. A column of water one foot square of that height weighs 218,242 pounds. Who could work the other end of the pump handle?

They thought of evaporating the water and sending it up as steam. But it was found that it would take an incredible amount of coal. They thought of separating it into oxygen and hydrogen, and then its own lightness would carry it up very quickly. But they had no power that would resolve even quarts into their ultimate elements, where tons would be required.

So they asked gravitation to help them. It readily offered to do so. It could not let go its hold of the water in the mine, nor anywhere else, for fear everything would go to pieces, but it offered to overcome force with greater force. So it sent the men twenty miles away in the mountains to dig a ditch all the way to the mine, and then gravitation brought water to a reservoir four hundred feet above the mouth of the mine. 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