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

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 York.

How can man combat part of the continent on the move, driven by the ceaseless powers of the air? By a humble plant or two. The movement of the sand hills that threaten to destroy the marvelous beauty of the grounds of the Hotel del Monte at Monterey is stopped by planting dwarf pines. The sand dunes that prevent much of Holland from being reconquered by the sea are protected with great care by willows, etc., and the coast sands of parts of eastern France have been sown with sea pine and broom.

The tract of a thousand acres on Cape Cod had been protected by humble beach grass. Some careless herder let the cows eat it in places, and away went part of a township. It is now a punishable crime on Cape Cod to destroy beach grass.


GAS HELP

This refers to more than stump speech-making. The old Romans drove through solid rock numerous tunnels similar to the one for draining Lago de Celano, fifty miles east of Rome. This one was three and a half miles long, through solid rock, and every chip cost a blow of a human arm to dislodge it. Of course the process was very slow.

We do works vastly greater. We drive tunnels three times as long for double-track railways through rock that is held down by an Alp. We use common air to drill the holes and a thin gas to break the rock. The Mont Cenis tunnel required the removal of 900,000 cubic yards of rock. Near Dover, England, 1,000,000,000 tons of cliff were torn down and scattered over fifteen acres in an instant. How was it done? By gas.

There are a dozen kinds of solids which can be handled--some of them frozen, thawed, soaked in water, with impunity--but let a spark of fire touch them and they break into vast volumes of uncontrollable gas that will rend the heart out of a mountain in order to expand.

Gunpowder was first used in 1350; so the old Romans knew nothing of its power. They flung javelins a few rods by the strength of the arm; we throw great iron shells, starting with an initial velocity of fifteen hundred feet a second and going ten miles. The air pressure against the front of a fifteen-inch shell going at that speed is 2,865 pounds. That ton and a half of resistance of gas in front must be much more than overcome by gas behind.

But the least use of explosives is in war; not over ten per cent is so used. The Mont Cenis tunnel took enough for 200,000,000 musket cartridges. As much as 2,000 kegs have been fired at once in California to loosen up gravel for mining, and 23 tons were exploded at once under Hell Gate, at New York.

How strong is this gas? As strong as you please. Steam is sometimes worked at a pressure of 400 pounds to the inch, but not usually over 100 pounds. It would be no use to turn steam into a hole drilled in rock. The ordinary pressure of exploded gas is 80,000 pounds to the square inch. It can be made many times more forceful. It works as well in water, under the sea, or makes earthquakes in oil wells 2,000 feet deep, as under mountains.

The wildest imagination of Scheherezade never dreamed in _Arabian Nights_ of genii that had a tithe of the power of these real forces. Her genii shut up in bottles had to wait centuries for some fisherman to let them out.


NATURAL AFFECTION OF METALS

"Sacra fames auri." The hunger for gold, which in men is called accursed, in metals is justly called sacred.

In all the water of the sea there is gold--about 400 tons in a cubic mile--in very much of the soil, some in all Philadelphia clay, in the Pactolian sands of every river where Midas has bathed, and in many rocks of the earth. But it is so fine and so mixed with other substances that in many cases it cannot be seen. Look at the ore from a mine that is giving its owners millions of dollars. Not a speck of gold can be seen. How can it be secured? Set a trap for it. Put down something that has an affinity--voracious appetite, unslakable thirst, metallic affection--for gold, and they will come together.

We have heard of potable gold--"_potabile aurum_." There are metals to which all gold is drinkable. Mercury is one of them. Cut transverse channels, or nail little cleats across a wooden chute for carrying water. Put mercury in the grooves or before the cleats, and shovel auriferous gravel and sand into the rushing water. The mercury will bibulously drink into itself all the fine invisible gold, while the unaffectionate sand goes on, bereaved of its wealth.

Put gold-bearing quartz under an upright log shod with iron. Lift and drop the log a few hundred times on the rock, until it is crushed so fine that it flows over the edge of the trough with constantly going water, and an amalgam of mercury spread over the inclined way down which the endusted water flows will drink up all the gold by force of natural affection therefor.

Neither can the gold be seen in the mercury. But it is there. Squeeze the mercury through chamois skin. An amalgam, mostly gold, refuses to go through. Or apply heat. The mercury flies away as vapor and the gold remains.

If thou seekest for wisdom as for silver, and searchest for her as for hid treasure, thou shalt find.


NATURAL AFFECTION BETWEEN METAL AND LIQUID

A little boy had a silver mug that he prized very highly, as it was the gift of his grandfather. The boy was not born with a silver spoon in his mouth, but, what was much better, he had a mug often filled with what he needed.

One day he dipped it into a glass jar of what seemed to him water, and letting go of it saw it go to the bottom. He went to find his father to fish it out for him. When he came back his heavy solid mug looked as if it were made of the skeleton leaves of the forest when the green chlorophyll has decayed away in the winter and left only the gauzy veins and veinlets through which the leaves were made. Soon even this fretwork was gone, and there was no sign of it to be seen. The liquid had eaten or drank the solid metal up, particle by particle. The liquid was nitric acid.

The poor little boy had often seen salt, and especially sugar, absorbed in water, but never his precious solid silver mug, and the bright tears rolled down his cheeks freely.

But his father thought of two things: First, that the blue tint told him that the jeweler had sold for silver to the grandfather a mug that was part copper; and secondly, that he would put some common salt into the nitric acid--which it liked so much better than silver that it dropped the silver, just as a boy might drop bread when he sought to fill his hands with cake.

So the father recovered the invisible silver and made it into a precious mug again.


NATURAL AFFECTION OP METAL AND GAS

A man was waked up one night in a strange house by a noise he could not understand. He wanted a light, and wanted it very much, but he had no matches that would take fire by the heat of friction. He knew of many other ways of starting a fire. If water gets to the cargo of lime in a vessel it sets the ship on fire.