(APRIL)
The higher Nilus swells
The more it promises; as it ebbs, the seedsman
Upon the slime and ooze scatters his grain,
And shortly comes the harvest.
--_Shakespere: "Antony and Cleopatra."_
THE BOTTOM-LANDS
All that wind was bound to blow up rain. I said so at the time. And,
sure enough, here it is; right where we want it, at the beginning of
April, a month famous for its rains.
The work of the rains is going to make one of the most interesting
chapters in the long story of the dust. At least I hope so. But don't
think I intend to tell it all. Why, it would make a whole book in
itself. But you can believe every single thing I do tell, no matter how
it makes you open your eyes; for, if I've helped it rain once I've
helped it rain a million times!
I. THE MARCH DUST AND THE APRIL RAINS
HOW RAIN GOES UP BEFORE IT COMES DOWN
It's this way: You remember how you can "see your breath," as we say, on
a cold morning? Well, that's because the moisture in your breath is
condensed by the cold. Now as the waters of the earth--the seas, lakes,
rivers, ponds, and so on--are warmed by the sun, the air above them is
filled with moisture, for the heating of the air causes it to expand and
draw in moisture from the water like a sponge. Expansion makes it
lighter also, and it rises. Rising, it turns cooler, and the moisture
condenses and comes down as rain. Mountains usually have clouds around
them because moist air striking the mountainside is driven up the slope,
cooling as it rises. So rain and snow fall often in mountain regions,
and that's why so many rivers rise in mountains. The moist air is also
condensed when it meets other and cooler air currents. But right here is
where the work of the dust comes in. For to make rain you've got to have
clouds, and clouds are due to this moisture collecting around the little
particles of dust of which the air is full. When these little motes of
matter become cooler than the air that touches them the moisture in the
air condenses into a film of water around them. Fairy worlds with fairy
oceans floating in the sky!
Each of these baby worlds is falling toward the big world below. But
very slowly; only a few feet a day, so that even if nothing happened it
might be months--yes, years--before it would come to the ground, even in
still air. But when air is very thick with moisture the water films on
these dust particles grow rapidly, and thus increasing in weight, they
fall faster and faster, and finally strike the earth as raindrops.
But here's another thing that helps. On the way down two or more
raindrops, falling in with each other, will go into partnership--melt
into one--and then they hurry down so much the faster. That's why the
sky grows darker and darker just before a rain, and why the lower part
of a rain-cloud is the darkest: the little raindrops are forming into
bigger raindrops as they fall.
THE LITTLE ARTISTS THAT SHAPE THE CLOUDS
But the shapes of clouds are supposed to be due to another thing, the
mysterious force we call electricity, and that other mysterious force we
call gravity. Just as the worlds attract each other by gravity so these
raindrops--or dust grains growing into raindrops--are drawn toward one
another. Here's where Electricity steps in. These rain particles are
full of electricity and when two of these electrified particles meet in
the air--unless they strike one another in falling, in which case, as I
said a moment ago, they blend into one--they get very close together and
yet keep dancing around one another without touching! It is this dancing
about that makes all those strange and beautiful and ever-changing
forms in the vast picture-gallery of the sky.
Of course the wind currents help to change these shapes, but I'm talking
about the original designs.
II. THE RAINDROPS AND THE RIVER MILLS
So much for the dust that helps make raindrops; now for the raindrops
that help make dust. This the raindrops do in several ways. Falling on
big rocks or decaying pebbles, for example, they pound loose with their
patter, patter, patter, any little bits of soil and grains of sand that
have been made by the other soil makers--the sun, the wind, the lichens,
the chemists of the air, and so on. This soil and these sand particles,
if there is already any depth of earth there, they carry down into the
ground. Some of this soil, with various stops and mixings with other
soils on the way, finally reaches the sea, where it helps to make the
rich limestone soils for the Kentuckies of millenniums yet to be, by
supplying food for sea creatures and lime for their shells. For these
shells become limestone when the shell-fish are through with them.
Mother Nature, in addition to feeding her big, hungry families of to-day
in the plant and animal world, is always laying by something for the
future. But before it gets back to the sea, by far the greatest part of
the ground-up soil the rivers carry is spread out in the lowlands in
those "alluvial plains" your geography tells about and that make a large
proportion of the fertile farms of the world. If the raindrops fall on
comparatively barren rock--in the mountains, say--they carry some of
this fresh soil to the mountain valleys below, and some of it they may
spread in bottom-lands a thousand miles away, where the new soil helps
feed the plants. The sand grains in it not only help the soil to get its
breath by making little air spaces, but these sand grains themselves
slowly decay and so make more soil.
[Illustration: WHAT IRRIGATION DOES FOR DESERTS
It is such land as this, in the arid regions of the West, that
irrigation converts from a desert to a garden of abundance. The soil is
rich in all the substances that plant life needs.]
But it isn't alone that they carry away the soil already made and bury
the sand grains. Some of the raindrops soak into cracks in stones and
dissolve the material that binds the rock particles together, and so get
them ready to give way under the fairy hammers of the next shower that
comes along.
After Nature finally gets an original waste of barren rock all nicely
set with grass and flowers and trees and things, the raindrops help to
make soil in still another way. Soaking through the decaying leaves,
they pick up acids which are just the thing for eating into rock and
crumbling it into soil. To be sure, the water soaking into the soil and
coming out of springs carries some plant food away with it; but it takes
it to lands farther down the river valleys, and more than makes up for
what it carries away by the new soil made by its acids from the rocks,
as it soaks into their pores and runs among the cracks.
HOW RAINDROPS MANAGE TO GRIND UP THE ROCKS
Moreover, raindrops actually grind up rocks. In order to do this a lot
of raindrops have to get together, to be sure, and become rivers; but
after all it's the raindrops that do it. There'd never be any rivers if
it weren't for the rains and, of course, the snows.
Well, anyhow, the rivers, besides running other people's mills, have
mills of their own; and millstones. Most of these stones originally came
from mountains and were brought into the milling business by mountain
streams, with the help of Jack Frost. For the frost not only pries
stones from the mountains and so sends them tumbling down the slopes,
but it keeps edging them along and edging them along, farther down,
after they have fallen. You'd hardly think that, would you? Yet it's
simple enough. The water in the pores of the rock expands when it
freezes and that makes the whole rock expand, for the time being. Then
when the frozen water in the rock pores thaws out, the rock contracts,
and this spreading out and pulling together, small as it is, causes the
rock to keep hitching along down the incline; oh, say a fraction of an
inch a year. But still, in the course of the ages, these inches foot up,
and after a while this tortoise-like gait lands the stone--lands tens of
thousands of such stones--in the beds of the mountain torrents that run
along at the bottom of these inclines. There they get ground together
and so grind out more soil material, particularly when the floods are
on, with the melting of the snows in spring and the falling of the heavy
and frequent rains.
[Illustration: AN OLD RIVER MILL
It used to do a lot of business--this old river mill. Its grist was
ground-up rock that helped make fine farming land in the bottoms along
the river's course. Such mills, called "pot holes," are found in the
rocky floors of rapid streams, where the eddying current or the water of
a waterfall wears depressions in the bed. Into these depressions stones
are washed, and then by the whirl of the flowing water kept going round
and round, grinding themselves away and grinding out the sides and
bottom of the mill.]
Another curious thing is how the river mills help themselves to new
millstones when they need them. If a river hasn't enough for its work,
it has a way of drawing on its banks for more. Whenever the stones in
its bed get scarce, so that it can make comparatively little new
soil--having so few stones to grind together--it proceeds to dig its own
bed deeper, since this bed is no longer protected by a rock pavement in
the bottom. This, of course, deepens its channel, and so adds to the
steepness of the slope of its banks. Then, owing to this increase in the
incline of the slope, more rocks tumble in, and the "milling business"
picks up again.
THE GOVERNOR IN THE RIVER MILL
But there may be too much of a good thing; the rocks may come in faster
than the river mill can take care of them. Then the river bottom becomes
so completely paved over that the channel stops wearing down at all, to
speak of, and the river remains at the same level until the rains and
the wind and other workers have worn the banks down and lessened the
incline. Then, with fewer and fewer fresh stones tumbling in, the river
gets a chance to catch up with its work.
It is this ground-up rock stuff of the mountain river mills, made by the
grinding of the running streams all the way down, that has helped form
the rich bottom-lands of the Mississippi Valley. For uncounted ages, the
water of the Mississippi and its tributaries have been at work, and by
the time you get down into southern Louisiana you come to the delta
where this rich soil has been piled up for more than 1,000 feet above
the bottom of the old Mediterranean Sea, that used to reach north and
south across the country.
You remember the lines, don't you:
"Little drops of water, little grains of sand
Make the mighty ocean and the pleasant land."
Well, this is how they do it; all this that I've been telling you.
[Illustration: _Courtesy of the Scientific American._
THOUSANDS OF FARMS POURED INTO THE GULF
The Father of Waters is a good farmer in some respects but needs
training in others. The Mississippi's floods, like those of Father Nile,
enrich the bottom lands, but the river is apt to break all bounds and do
a lot of damage. Moreover, every year it carries away thousands of acres
of good soil and pours it into the Gulf. How to teach the Mississippi to
work in harness, as the Nile has been taught to do in recent years, is
one of the problems which will require all of Uncle Sam's ingenuity and
skill to solve. A good deal of the yearly waste could be prevented,
however, by the various means employed by good farmers.]
III. HOW THE RIVERS ACT AS BANKERS FOR THE FARMERS AND THE SEA
We speak of river banks and the kind of banks that handle those
promissory notes our arithmetics tell about as if they were entirely
different; and so they are, I suppose, if one just looks at the surface
of the thing. But if we dig into the subject a little we shall see that
they are much alike in the fact that one of the principal businesses of
both kinds of banks is to make loans at interest. Men's banks loan
money, to be sure, while the river banks loan pebbles, but if it were
not for these pebble loans there would be a mighty sight less money for
the banks to loan, or the farmer to borrow; and the way both banks do
business ought to be a good lesson to certain farmers I know, who seem
to think they can always be cashing checks on their banks--the farm
lands--by hauling away the crops without ever putting anything back.
[Illustration: WHERE THE RIVERS ACT AS BANKERS
Here is a fine piece of bottom land, one of those "banks" where the
rivers keep "checking accounts" for the farmers and the sea; using
pebbles for currency, as explained in this chapter.]
HOW THE RIVERS PLACE PEBBLES ON DEPOSIT
The rivers make loans to the soil by depositing pebbles in the broad
bottom-lands along their banks, and then draw interest by carrying along
to other lands, from time to time, some of the fine rich soil these
pebbles help make by their decay. And the river does this in regular
banking style, "checking out" the pebbles from time to time, and then
depositing other pebbles in their places. Take the banks and
bottom-lands of the Mississippi River, for example. It has been
estimated that it requires about 40,000 years for a pebble to make the
journey to the Gulf from the mountains of a tributary stream where it
was first broken from the rock as a sharp fragment.
The first part of the journey in the mountains is over steep down
grades, and so is comparatively fast, but as the river gets farther from
the mountains, the slope of its bed becomes less and less, the onward
movement is slower and slower, and more of the pebbles stop to rest. In
times of flood they are carried far away from the regular channel and
spread over the wide flood-plain of the river. Then, as the flood goes
down, they are left buried there under a coating of mud. So buried, they
decay and enrich the soil. Then the next flood that comes along sweeps
the pebbles with it--checks them out of the bank--but at the same time
carries away not only some of the soil richness which these pebbles
helped to make but the soil material made by the decay of the vegetation
these pebbles thus helped to grow, such as the roots and blades of wheat
and corn and stubble and chaff left in the fields. That's the interest
on the loan. Then, when the flood subsides, the pebbles are again
deposited farther along in the river's course, but meanwhile the same
flood has brought fresh deposits of pebbles from up-stream, and these
are left in place of those taken away.
RIVER BANKING AND HUMAN CIVILIZATION
This banking business has been going on for ages and is a very important
part of the history of civilization. Here and there along the sides of
the older and larger river valleys are found the remains of ancient
plains. These plains are now, many of them, quite a distance above the
level of the stream. This means that they were at one time the
bottom-lands of that same stream, but the stream, as it dug deeper and
deeper into its bed, grew narrower, and so abandoned its old
flood-plains. As savage man gradually settled down and took to farming,
he found these bottom-lands, with their rich, mellow soil, just the
thing for his crooked-sticks and stone hoes--the only kinds of ploughs
and hoes there were in those days. With such crude farming tools he
couldn't have managed to scratch a living on any other kind of soil.
When the river floods came along, all these crooked-stick farmers had to
do was to keep out of the way until the floods went down, and there were
their fields all fertilized for them, as good as new, and they could go
on for thousands of years working the same fields without ever bothering
their heads as to whether they needed any lime or potash or nitrogen, or
anything; for they didn't. The river floods attended to all that.
[Illustration: FATHER NILE AND THE MAKING OF EGYPT
"Egypt," said Herodotus, "is the gift of the Nile"; and it is true so
far as her fertile lands are concerned. The ancients attributed the
annual floods to the god of the Nile, as shown in that statue of Father
Nile in the Vatican. Below is a threshing scene in Egypt painted by
Gerome. The last picture, from a carving in the tomb of an Egyptian
noble, shows how they ploughed and sowed in the Pyramid age.]
So, in course of time, civilizations such as those of Egypt and India
and Persia grew up, and in further course of time these civilizations
spread into Europe, and finally to the New World.
HOW RIVER BANKS GO BANKRUPT
Now all this is very well, this leaving it to Nature to fertilize the
fields, where everything is just right for it, as it is along the Nile,
but in most lands it won't do it all. The trouble is that, in raising
the grain foods, the ground must be kept free of grass and weeds, and
well ploughed during the rainy season. But the same rains that water the
fields wash more or less good soil into the streams; much more than
Nature alone can put back. For instance, down in Italy where, if the old
forests were still there, the rains wouldn't wash away more than a foot
of soil in 5,000 years, this soil is being carried into the Po, and by
the Po emptied into the sea so fast--a foot in less than 1,000
years--that if you visit Italy to-day, say, and then go back in ten
years, you'll see bare rocks on many a hillside that is now clothed in
green. On such rocks the soil is already thin, and in ten years more it
is all gone; all washed away! This thing is going on all around the
shores of the Mediterranean. You are constantly coming on sections of
country that used to be covered with great forests and prosperous
farming communities where the soil has vanished, and many stretches of
barren, rocky land where hardly a weed can find a foothold.
[Illustration: WHAT HAPPENS TO THE LAND WHEN THE TREES ARE GONE
Could anything be more desolate? You can see from this example how vital
to our national life is the forest conservation work of our government.
Trees, by the network of their roots, keep the soil from washing away,
retain moisture by their shade, and absorb the water of the rains and
the melting snows so that it reaches the rivers and the creeks
gradually. But when the trees are gone the water, unchecked, rushes down
the slopes in floods, washing away the precious soil and leaving them as
barren as a desert.]
"But, what are you going to do about it?" you say. "You can't change the
slope of the hills, can you? And the farmer has _got_ to plough his
land--you just said so yourself."
Yes, he's got to plough his land, to be sure; but so has he got to have
pasture for his live stock. If he hasn't any live stock, that just shows
what kind of a farmer he is. Every farmer ought to have live stock. Corn
always brings a great deal more when it goes to market "on four feet,"
as the saying is; and, besides, the live stock give back to the fields,
in the shape of manure, a large part of what they eat. Now, if you have
live stock you must have pasture, and all land with a slope of more than
one foot in thirty should be used partly for pasture and partly to grow
wood for the kitchen stove, and hickory-nuts and walnuts for winter
firesides. Although the land slopes, the mat made by the grass roots
will keep it from washing away.
"But suppose you lived where there wasn't any land to speak of that
didn't tip up; in New England, say--what would you do then?"
Leave the upper part of the slopes in the woods. Then the water that
carries off the soil will not run entirely away, as it does in ploughed
fields, but will creep down slowly, and, charged with the decay of the
woods, help fertilize the lower lands and change the rocks beneath them
into soil--the acids from the decaying vegetable matter eating into
them.
"But still," you say, "there are farm lands that must be ploughed even
if they do wash away; they're all the land a man has, sometimes. What
then?"
Plough deep. Then the soil soaks up more of the rain and lets the water
pass away in clear springs. This not only saves soil but, as we have
just said, helps to decompose the subsoil and the bed rock.
Then there's another thing that good farmers do in such cases. They
plough ditches along the hillside leading by a gentle slope to the
natural watercourses; so the water of the rains, instead of going down
the hills with a rush, and going faster the farther it runs--like a boy
on a toboggan--is caught and checked in these sloping ditches, and much
of the soil it contains deposited before it reaches the streams.
[Illustration: HOW THE FRENCH PROTECT THEIR HILLSIDE FARMS
This is how the French peasant keeps the mountain torrents from carrying
off his precious soil.]
The best way of all, of course, is to build terraces, as they do in the
thickly settled parts of Europe. But this is only profitable for the
more valuable crops and not for ordinary grains.
SUCH SPENDTHRIFTS OF GOD'S GOOD SOIL!
My, but it's a shame the way we've wasted soil in this country. What
spendthrifts! To start with--when the country was first settled--there
seemed no end to the fine land, and every one could have a good farm for
the asking. All he had to do was to make his wants known to Uncle Sam
and then go out and help himself. What happened then? Why, what always
happens? Easy come, easy go. These pioneer farmers worked their farms
for all there was in them; didn't bother, many of them, even to haul the
barn manure into the fields. Then when the old farm was exhausted they
moved off to new lands and did the same thing over again.
[Illustration: A HOME IN THE DESERT
Doesn't look much like a home in the desert, does it? But it is--a
lovely home in what the old geographies called "The Great American
Desert." In the Sahara oases are few and far between, but modern
irrigation engineering makes oases to order--thousands and thousands of
acres of them!]
They ploughed on steep hillsides; they allowed gulches to form, as they
will quickly do on sloping ploughed land, if you don't watch out; they
cut away the timber. It's easy in a hill country like the eastern part
of the United States to have all the good top-soil washed away in
twenty years after the forests have been destroyed; the good soil that
it probably took 2,000 years to make.
Doctor Shaler[8] estimated that in the States south of the Ohio and the
James Rivers more than 8,000 square miles of originally fertile land
had, by this shiftless and thoughtless way of doing things, been put
into such a state that it wouldn't grow anything; and over 1,500 square
miles of this, actually worn down to the subsoil, and even to the bed
rock, so that it may never be profitable to farm again--at least not in
our time--no matter what they do!
[8] "Outlines of Earth's History."
I knew a farmer with a small son to whom he intended to leave the farm
when he grew up, who did things like that for twenty years. By the time
the little boy was old enough to vote, there was no farm to leave; all
the good part of it was gone.
Serious thing for that little boy, wasn't it?
HIDE AND SEEK IN THE LIBRARY
What have burrowing animals to do with the drainage system of the
land? (Keffer's "Nature Studies on the Farm.")
How do angleworms help drain the soil?
How do the forests help make good use of the rain that falls, not
only for themselves but for the rest of us?
How do the rains help to warm the ground in the spring? The heat
they carry into the soil is produced in two ways. The book
mentioned above tells of one of these ways, and Russell's little
book, "The Story of the Soil," tells of another.
Beale's "Seed Dispersal" tells how the raindrops (working together,
of course) help plant maple, elm, sycamore, willow, and other trees
that grow by the waterside, to scatter their seeds.
You'd be surprised what a series of adventures the seeds of a
bladderwort have before they get planted on some new shore, after
having left the parent shrub. First, they float down-stream, as you
know, but when autumn comes on, what do you suppose they do? They
go to bed. Where? Right in the bottom of the stream. Then how do
they ever get up and get planted on the shore? Well, you just look
it up in that Beale book and see.
Do you know how the rains help to get the mineral food up into the
plant?
And why swamps are such poor producers?
And how the sun acts as a pump for the plant world?
You will find answers to all these questions in Shaler's "Outlines
of Earth's History" and in your books on botany and agriculture.
Russell's book on the soil tells how the ancient Gauls and Britons
used to fertilize their land with marl, and how the tides help to
fertilize England. It's just the reverse of the way Father Nile
looks after Egypt, as you will see.
If you want to read an interesting description of the difficulties
of farming on wet lands, you will find it in this meaty little
book.
If you don't know how serious a thing it is to let gullies form in
land, look it up in Shaler's "Man and the Earth" and you will see.
How do you suppose deserts that get so little rain themselves could
_help make it rain_ in other places? For example, the desert of
Thibet is the chief cause of the monsoon rains that do so much for
India. That part of your geography that explains the circulation of
the air will help you figure this out; particularly with a map
under your eye that shows the relative location of the desert and
the Indian Ocean, over which the monsoon winds blow.
[Illustration: AN EXAMPLE OF MAN'S DEBT TO THE EARTHWORM
Much of the earth's Maytime bloom and beauty is due to the labor of our
humble little brother of the dust, the earthworm; a striking fact which
was never recognized until the great Charles Darwin looked into the
matter and wrote a book about him. This picture by Millet is called
"Springtime" and hangs in the Louvre, in Paris.]