The Adventures of a Grain of Dust Part 4

"Horns and hoofs? You can't. You're a grain-eater!"

See the point? The baron argued that because the monster had horns and hoofs he must be a grain-eater; for all creatures with both horns and hoofs are grain-eaters. This particular creature, to be sure, was an eater of both meat and grain--being one of Cuvier's students who was trying to play a trick on him. But the principle holds good. The scientists, _knowing_ one thing, _infer_ another.

Because animals with both horns and hoofs eat no meat Cuvier knew his visitor couldn't eat _him_, even if he'd been real and not just made up.

For another instance, take our queer old friend that Professor Blackie wrote the funny rhyme about--the Ichthyosaurus "with a saw for a jaw and a big staring eye." The scientists figure, just from looking into the hollow socket where the eye used to be, that he could see at night like a cat--and right through muddy water, too; that he spent most of his time in shallows near the sh.o.r.e; that it didn't make any difference to him whether a fish was near or far, provided it wasn't too far, of course, for he could see it and catch it, just the same. They also said--these learned men, after peering into the dark hollow where that remarkable eye used to be--that Mr.

Ichthyosaurus spent a great deal of time diving and a great deal of time with his homely face just above the surface of the water.

Why they could reason all this from a hollow eye socket and some bony, flexible plates around the outer edge of it, you will see by referring to such books as "Animals of the Past," by F. A. Lucas, director of the American Museum of Natural History; "Creatures of Other Days" and "Extinct Monsters," by Hutchinson; "Extinct Animals," by Lankester; "Mighty Animals," by Mix; the chapter "When the World was Young," in Lang's "Red Book of Animal Stories," and "Restoring Prehistoric Monsters" in "Uncle Sam, Wonder Worker," by Du Puy.

Here are some more conclusions they draw from certain facts. See how near you can come to reasoning them out for yourself before looking them up in the books that tell.

Why it is supposed the Dinosaurs swam like Crocodiles. (Look at the picture of Mr. I., and pay _particular_ attention to his tail.)

Why it is they say that the sea-lizards with long necks must have had small heads.

Why it is argued that because the Mesosaurus had a hinge in his jaw he must have had a big, loose, baggy throat.

"Keeping Up the Soil," in "The Country Life Reader," deals with the subject of the use of fertilizers on the farm--how easy it is to waste them, how easy it is to save them, and how important it is that they should be saved; while the article on "Acid Soils" tells how the lime in the bones of the monsters has helped keep the soil from getting "sour stomach," and also how they unlocked the potash and phosphorus in the soil so that the plants could get at them.

[Ill.u.s.tration: FERTILE FIELDS THAT RODE ON THE WIND

The winds that now help grow the corn and wheat on these broad fields by carrying the pollen from one plant to another, also brought the soil on which they grew. These are the loess plains of Nebraska. There are 42,000 acres of them.]

CHAPTER III

(MARCH)

... the busy winds That kept no intervals of rest.

--_Wordsworth._

Except wind stands as never it stood 'Tis an ill wind turns none to good.

--_Tusser._

THE WINDS AND THE WORLD'S WORK

That saying "idle as the winds" must have started in the days when they didn't know; for if ever there was a busy people, it's the Winds.

Not only do they help plant the trees of the forest, sow the fields with gra.s.s and flowers, and water them with rain, but they make and carry soil all over the world. And, like everything else in Nature, they have a sense of beauty and the picturesque. Rock, for example, weathered away into dust by the help of the winds, as it is, takes on all sorts of picturesque shapes. And, of course, the winds love music; everybody knows that. Before we get through with this chapter we're going to end a happy day outdoors with a grand musical festival in the forest, with light refreshments--spice-laden winds from the sea. There'll be n.o.body there but the trees and the winds and John Muir and us; all nice people.

I. SUCH CLOUDS OF DUST!

March leads the procession of the dusty months because the warming up of the land, as the sun advances from the south, brings the colder and heavier winds down from the north. These winds seem to have a wrestling match with the southern winds and with each other, and among them they kick up a tremendous dust, because there's so much of it lying around loose; for the snows have gone, and the rainy season hasn't begun, and the fields are bare.

ABOUT THE DUST WE GET IN OUR EYES

Most people think these March winds a great nuisance because some of us dust grains are apt to get into their eyes; but dust in the eye is only the right thing in the wrong place. Just think of the amount of dust going about in March that _doesn't_ get into your eye; and how nice and fine it is, and how mixed with all the magic stuff of different kinds of soil, thus brought together from everywhere.

An English writer on farming says he thinks the fact that English farms have done their work so well for so many centuries is due, in no small degree, to the March winds that have brought us world-travelled dust grains from other parts of the globe.

And the wind is a good friend to the good farmer, but no friend to the poor one; for it carries away dust all nicely ground from the fields of the farmer who doesn't protect his soil and carries it to farmers who have wood lots and good pastures and winter wheat, and leaves it there; for woods and pastures and sown fields hold the soil they have, as well as the fresh, new soil the winds bring to them.

Most of the fine prairie soils in our Western States owe not a little of their richness to wind-borne dust. In western Missouri, southwestern Iowa, and southeastern Nebraska are deep deposits of yellowish-brown soil, the gift of the winds. And, my, what apples it raises! It is in this soil that many of the best apple orchards of these States are located. And now, of course, the apple-growers see to it that this soil stays at home.

But there's another kind of dust that deserves special mention, and that's the kind of dust that comes from volcanoes. Volcanoes make a very valuable kind of soil material, often called "volcanic ash." It isn't ashes, really. It's the very fine dust made by the explosion of the steam in the rocks thrown out by the volcano. The pores of the rocks, deep-buried in the earth, are filled with water, and when these rocks get into a volcanic explosion, this water turns to steam, and the steam not only blows out through the crater of the volcano, but the rocks themselves are blown to dust. This dust the winds catch and distribute far and wide. Sometimes the dust of a volcanic explosion is carried around the world. In the eruption of Krakatoa, in 1883, its dust was carried around the earth, not once but many times. The progress of this dust was recorded by the brilliant sunsets it caused. It is probable that every place on the earth has dust brought by the wind from every other place. So you see if you happen to be a grain of dust yourself, and keep your eyes and ears open, you can learn a lot, as I did, just from the other little dust people you meet.

THE WINDS AND VOLCANOES

But that isn't all of this business--this partnership--between the volcanoes and the winds. Did anybody ever tell you how the volcanoes help the winds to help the plants to get their breath? It's curious. And more than that, it's so important--this part of the work--that if it weren't carried on in just the way it is, we'd all of us--all the living world, plants and animals--soon mingle our dust with that of the early settlers we read about in the last chapter. In other words, all the _plant_ world would die for lack of fresh air and all the _animal_ world would die for lack of fresh vegetables. So they say!

According to that fine system--the breath exchange between the people of the plant and animal kingdoms--the plants breathe in the carbon gas that the animals breathe out; you remember about that. But the amount of carbon gas in the air is never very large, and if there were no other supply to draw on except the breath of animals and the release of this same gas when the plants themselves decay, we'd very soon run out.

Now this needed additional supply comes from the volcanoes. Every time a volcano goes off--and they're always going off somewhere along the world's great firing-line--it throws out great quant.i.ties of this gas, and this also the winds distribute widely and mix through the atmosphere.

And another thing: This carbon in the air helps crumble up the rocks already made, and it enters into the manufacture of the limestone in the rock mills of the sea. This limestone will make just as rich soil for the farmers of the future as the limestones of other ages have made for the famous Blue-Gra.s.s region of Kentucky, for example.

All of which only goes to show how first unpleasant impressions about people and things are often wrong. A "dusty March day," you see, isn't just a dusty March day. It's quite an affair!

II. THE DUST MILLS OF THE WIND

But wind is not alone a carrier for other dust-makers; it has dust mills of its own. The greatest of these mills are away off among the mountains and in desert lands, but after making it in these distant factories the winds carry much of this fresh new soil material to lands of orchard and pasture and growing grain.

Not long ago two of the professors at the University of Wisconsin found a good ill.u.s.tration of what an immense amount of soil is distributed in this way, and what long distances it travels. Among the weather freaks of a March day was a fall of colored snow that, it was found, covered an area of 100,000 square miles, probably more. The color on the snow was made by dust blown clear from the dry plains of the Southwestern States, a thousand miles away. The whole of this dust amounted to at least a million tons; and may even have amounted to hundreds of millions of tons, so the professors think.

[Ill.u.s.tration: TYPES OF NATURE'S SCREW PROPELLERS

You can see for yourself (from the picture on the left) that long before man ever thought of driving his ships through the water with screw propellers or pulling his flying machines through the air by the whirligigs on the end of their noses, some flying seeds, such as those of the ash here, had screw propellers of their own. And do you know that Nature also employs the propeller principle, not only in the operation of the wings of birds but in the wing feathers themselves? The two pictures on the right show the action of the wing and the wing feathers when a bird is in flight.]

LITTLE MILLSTONES IN BIG BUSINESS

For grinding rocks to get out ore, or for making cement in cement mills, men use big machines, somewhat on the style of a coffee-mill. These machines are called "crushers." The winds, in their enormous business of soil-grinding, however, stick to the idea you see so much in Nature, that of using _little_ things to do _big_ tasks; as in digging canyons and river beds, and spreading out vast alluvial plains by using raindrops made up into rivers; in working the wonders of the Ice Ages with snowflakes; and building the bones and bodies of those big early settlers, and of all animal life, and the giant trees of the forest out of little cells. For, what do you suppose the winds take for millstones in grinding down the mountains into dust? Little grains of sand!

And with the help of the sun and Jack Frost it makes these fairy millstones for itself. The outside of a big rock grows bigger under the warm sun, in the daytime, and then when the sun goes down and the rock cools off it shrinks, and this spreading and shrinking movement keeps cracking up and chipping off pieces of rock of various sizes. Up on the mountain tops, among the peaks, the change of temperature between night and day is very great, and even in midsummer you can always hear a rattling of stones at sunrise. The heat of the rising sun warms and expands the rock, and so loosens the pieces that Jack Frost has pried off with his ice wedges during the night.

Then also during periods of alternate freezing and thawing in Spring and Fall, the rock is slivered up. These changes in the weather as between one day and another are due to the winds. In January and February, for example, thaws and freezes are common. When the winds blow from the south, the snow melts, water runs into cracks in the rock and fills their pores; then a shift of the winds to the north, a freeze, and the water in the crevices and the pores turns to ice, expands, and breaks off more rock.