(APRIL)
Now the noisy winds are still;
April's coming up the hill!
All the spring is in her train,
Led by shining ranks of rain.
--_Mary Mapes Dodge._
THE APRIL RAINS AND THE WORK OF THE RIVERS
I always liked the little boy's definition of a river system. "Rivers
that empty into other rivers that empty into other rivers that empty
into the sea."
What is still more interesting, the sea at the same time is emptying
into the rivers; for the waters of all the lands and the waters of all
the seas, are one, and what the rivers give to the sea the sea returns
in the rain clouds that are blown landward by the winds. The Earth's
waters are thus always in circulation like the blood in our bodies. In
making this endless circuit they do an immense amount of useful and
beautiful work, and have many strange and curious ways of doing it.
It's a great family affair of the Waters people. Everybody has a hand
in it, from the baby rill that toddles across the country road, the
brook it meets in the meadow, the creek that runs through the wood,
and the river into which it flows, to the greater river which carries
forward these mingled waters to the sea.
[Illustration: THE MISSISSIPPI RIVER SYSTEM]
I. What I Brought Back from the Creek
I met a rain-drop once that had followed the thing through, starting
where a little creek began, and got such a load of information I could
hardly carry it, about the wonderful part the rivers take and have
taken in the making and remaking of the world.
We see the April rains carve fairy canyons in the soft clay of the
roadside or the creek, but it is hard to realize, as we stand on some
pinnacle of the Alps and look out over the deep and wide valleys, the
gorges, the cliffs, and mountains cut in two, that all are but the
handiwork of the rain-drops banded together as flowing waters. For
a long time this was questioned by scientific men, because the idea
so upset the old theory that great changes in this world of ours came
about all of a sudden and from causes not at work in these days. Now,
however, nobody doubts that the big things are done by the little
people, working together over long periods of time; little snowflakes,
little rain-drops, little cells in plants. As a result, the Alps, so
far as the expression of their faces is concerned, are as little like
the Alps of the past as the face of the old farm of to-day is like the
farm of those ancient yesterdays, when the brontosaurus browsed where
old Dobbin is nipping the meadow grass and the mammoth ate the leaves
of trees that stood where White Face is thoughtfully chewing her cud in
the shade.
[Illustration: HOW THEY STUDY GEOGRAPHY IN BOSTON
This is what, in the Boston schools, they call an "umbrella party."
"Umbrella party" sounds much more attractive than "geography
lesson," but as a matter of fact it is a geography lesson and a
fine one. As soon as they get off that brick pavement the boys and
girls will see those rain-drops cutting out little Mississippi
River systems, filling little Great Lakes, plunging over Niagaras
two inches high!
]
Right where you sit reading, perhaps, the land used to be buried two
miles deep beneath rocks which have been worn away by wind and rain and
by rivers which vanished long ago. Everything has been so changed that
if the old scenery should be put back you would be lost right on the
home farm.
WHERE YOU CAN JUMP ACROSS THE MISSISSIPPI
Wrinkles in the earth and in the mountainsides make the first troughs
for the streamlets and the rivers, and then the running water itself
digs these natural channels deeper. Many rivers begin as streamlets
flowing out of springs. The great Mississippi began as a baby, just
like the rest of us. You can jump across it still if you go up to
its source. Springs not only start rivers in life but go on feeding
them. Most large river systems get secret gifts in this way, as they
flow along, from thousands of springs that empty into them or their
tributaries.
So springs start and feed the rivers. Now what do you suppose starts
the springs? Rain-drops stored away in big stone "safes," much as a
small boy stores away pennies in his tin bank! The water of rains and
melting snows, passing down through the soil, soaks into the little
chambers or pores in such rocks as sandstone and limestone, and keeps
going on down until it comes to a bed of hard stone, such as slate or
granite, into which it cannot soak.
[Illustration: THE SPRING WHEN EMPTY]
[Illustration: THE SPRING WHEN FULL]
THIS SPRING PLAYS IT'S A TOWN PUMP
These two pictures show an intermittent spring about five miles
from Singer Glenn, Virginia, and there called the "Tide Spring."
You can see where the idea of the tide comes in, but can you think
why the spring seems to have a tide system all its own? You know
what a siphon is. Well, think how a kind of siphon might be formed
in rock, dissolved out by water flowing underground. Then look at
the picture on the next page.
Now rock-beds, as you know, have a slope--some more, some less--owing
to the wrinkling of the earth's crust. So the water, slowly trickling
through the porous rock, forms a steady stream which runs down along
the hard rock, as rain runs down a roof, and finally gushes out at some
lower level.
[Illustration: HOW THE LITTLE SPRING WORKS ITS PUMP
This is how the pump of an intermittent spring is worked. Some
portions of rock are dissolved by underground waters more readily
than others and so cavities are sometimes formed, as shown. As
long as the water in the reservoir is below the arch of the
siphon-shaped outlet no water escapes, but as soon as it rises to
the level of the arch the whole of the water is drawn off. Then
the spring ceases to flow until the reservoir fills up again. You
can empty water in the same way by using a bent tube of any kind.
Can you tell why the water flows up-hill in this way? Remember
what you know about air-pressure and then look up "siphon" in your
encyclopædia.
]
You can be sure these companies of rain-drops, hurrying back to the
light, don't fail to notice any cracks in the rocks along the way, and
at such places they come gushing up with sparkle and dance; and the
greater the dip of the rock beds the higher they dance, of course.
But it takes any one rain-drop so long to get back into the sunshine
after it starts on its underground journey that you'd think it would
forget how to dance at all! It isn't just the same rain-drop, to be
sure, that goes into the ground and comes out again, because the
rain-drops get all mixed up with each other as they move along, but
just imagine some one rain-drop that fell, say, on a hilltop on the day
a baby was born in a valley five miles away, where there was a spring
in a shady hollow near the baby's home. By the time that rain-drop got
down to the spring the baby would be old enough to vote!
Yet this is a very good thing for the rivers and the rest of us--this
slow travel of the underground water, whether it comes out in springs
or simply seeps through the soil as most of that which supplies the
rivers does. Otherwise, if all the water of the rains went directly
into the rivers we would have floods after every wet spell and empty
river beds between times.
Here's another river rebus. How do rivers grow longer at the top? All
rivers grow at their source because their headwaters eat back into the
rocks and the soil, just as the rain wears away the head of any gully.
Where the rock is soft they eat back faster. The Mohawk River in New
York State probably wouldn't have amounted to anything if it hadn't
done this very thing. From Albany westward past Utica runs a belt of
shale, a weak stone, but here so soft that the surface of it crumbles
back to clay in every winter's frost. Into this the Mohawk, which in
past ages was only a little stream, has eaten back its way until now it
is over a hundred miles long.
But sometimes rivers are so big the very first day they come into the
world that you may say they are born half grown. You find them, among
other places, in the mountains of California. Nearly all the water
from the melting snows on Mount Shasta sinks at once into the porous
lava fields of the mountain slopes, and after wandering about in the
hidden veins comes out, filtered and cool, in the form of large springs
which make rivers that set out on their life journeys without ever
having been babies at all so far as you can see. The Shasta River is
one of these. The McCloud is another. It gushes forth suddenly from a
lava bluff in a roaring spring seventy-five yards across, two-thirds of
the width of the river in its widest part. The River Jordan in the Holy
Land begins in one of these great springs at the foot of Mount Hermon.
[Illustration:
_From Norton's "Elements of Geology." By permission of Ginn and
Company_
HOW MOST OF EUROPE'S RIVERS GET THEIR START
Most of the important rivers of Europe start as streams of
ice-water, flowing out of glaciers. Notice the boulders along the
side of the stream. They also came out of the body of the glacier,
where, as we shall see when we take up "The Stones of the Field"
in Chapter VII, the boulders that rode south with the glaciers got
most of their roundness.
]
We know already what a hand the glaciers had in the Ice Age in shaping
the course and conduct of rivers, and you may be sure they have
something to do with the making of rivers to-day. The under side of a
glacier gets warmed from three sources: (1) its own pressure; (2) the
friction as it moves; and (3) the heat from the inside of the earth
which, on account of this thick ice blanket, can't get away into the
air as it does elsewhere. This heat melts the ice and, as we know,
there is water melting also on the surface of glaciers and in the
crevasses. Beside all this the water of rains falls upon the glacier
so that there is plenty of water to make rivers, and we always find
streams of water running from a glacier's front. Most of the rivers of
Central Europe start in this way.
THE BEAUTY OF THE BRIDAL VEIL
And, although they didn't make the rivers themselves, the Ice Age
Glaciers are held responsible for the fact that many little rivers
always have to jump to catch the train. That is to say, they come
tumbling over falls to join the larger streams into which they empty.
The reason of this is that when, in the Ice Age, the glaciers filled
the river valleys the larger glaciers in a main valley dug below the
tributary valleys and so left the mouths of the tributary rivers high
up on the main valley's walls. The famous "Bridal Veil" in the Yosemite
is one of these side valley falls. The fall--900 feet--is so great
that the water widens to a fleecy foam and waves back and forth in the
wind like a gauzy veil and, instead of a roar like Niagara, it makes a
rustling sound like silk.
While some rivers come hurrying down like that--as if they really were
afraid the larger river would go off and leave them--others, like the
Amazon, roll on as stately as a Lord Mayor's procession. But the
waters of all are on their way to the sea. The rock layers, owing to
the wrinkling of the earth as it shrinks, are nowhere level, so flowing
water is always on a down grade, sloping toward the sea or toward other
land that does slope toward the sea. Then remember too as the sea
bottom keeps sinking the continents keep rising, which increases the
pitch of the land.
[Illustration: JUMPING TO CATCH THE TRAIN
See the famous Bridal Veil Falls in the Yosemite Valley hurrying
down to reach the river below. As the stream descends, it broadens
into a beautiful, filmy veil.
]
All very simple, but none the less grand and impressive. Ruskin, in one
of the noblest of his passages, says:
"[All water courses], from the inch-deep streamlet that crosses the
village land in trembling clearness to the massy and silent march of
the Amazon and the Ganges, owe their play and power to the ordained
elevations of the earth; [to] paths prepared for them by which at
some appointed rate of journey they must evermore descend, sometimes
slow and sometimes swift, but never pausing, the gateways of guarding
mountains opened for them in cleft and chasm, and from afar off the
great heart of the sea calling them to itself."
That's a poetic way of putting it, but it's a fact nevertheless.
II. The Human Nature in Rivers
There's a lot of human nature in rivers. To begin with, as we might
suppose, they do the most playing and the least work when they are
young. Brooks will be brooks, you know!
What pretty ways they have in babyhood! Kissing the pebbles, crooning,
bubbling, chattering, playing, they are big Mississippis or great
oceans that, like Homer's ocean river, flow around the world. Their
bubbles are ships, sometimes wrecked on dreadful headlands along the
shores.
THE CHANT OF THE WATERFALLS
Waterfalls are found only in young streams and more often as you near
the source. Older streams have worn down their beds more nearly to
a level and, as we all know, more rivers begin among the mountains
and highlands than in the lower lands. In the mountain regions there
are plenty of rocks and cliffs to jump from, and the rivers, you may
be sure, make the most of their opportunities. At such falls as the
Bridal Veil they jump so far they are turned into white cascades, and
as you climb the cliff beside them and feel the wind wafting spray in
your face you hear the music of their songs. The more or less regular
dash of the water as it swings back and forth in the wind gives that
chanting sound described in waterfall poetry.
[Illustration: "BROOKS WILL BE BROOKS, YOU KNOW!"
Our baby river of the meadow seems to be playing it has a Niagara
Falls of its own, "Rock of Ages" and all! See the "huge mass" of
rock at the foot of the falls; and the rapids?
]
Like children these dancing, singing rivers love pictures and color.
You see that in the rainbow tints of the spray as the sunlight strikes
the air bubbles the waterfall "blows"; in the green of its waters
turned to gray in the foam; in the reflections of mountain, sky, and
cloud in the smooth stretches below the falls.
And, like pebbles and other little people, rivers love to play in the
rain. My! What a time! In a storm, with a gray flood pouring from the
sky, you hear, mingled with the voice of wind and rain, the swash and
gurgle of the eddies as the river goes along in its dance, wild with
the joy of it all. In a mountain stream during a heavy rain, with wind,
you can also hear the waves dashing against the rocks along the shore
or in the stream, and the smothered, bumping, rumbling made by the
boulders on the bottom knocking against each other.
STORM CHORUS OF THE MOUNTAIN TORRENTS
From any high place during a mountain storm you can see twenty, yes,
often a hundred torrents, and the noise of the water and the moving
stones makes a wonderful storm chorus. Reclus compares the sound made
by the stones to dull thunder.
WHERE TO LOOK FOR HIDING RIVERS
Rivers, both young and old, play hide and seek. Possibly the older
rivers get to dreaming of their infancy when they were springs, and
want to play they are springs again; anyhow, they disappear in the
ground in one place and then come out laughing in another as if they
really _were_ springs! And how they must chuckle to themselves when
they fool people into thinking they are brand new rivers! This happens
sometimes, and so the river gets a different name at the place where it
comes out from the name it bears up to the point where it disappears.
Such hide-and-seek rivers are found in regions where it doesn't often
rain. The Tujunga, which you cross in going from Los Angeles to San
Francisco, is such a river. At one place in its course it comes out of
a canyon, looks around a minute, and then disappears in the pebbles,
sand and gravel of the plain. Down it goes until it reaches a bed of
hard rock. Along this underground bed it runs until it gets to a place
north of Cahuenga Peak, where it comes up in springs and flows into the
Los Angeles River.
[Illustration: THE LOST RIVERS AND THE THOUSAND SPRINGS
These are the waters of some hidden tributaries of the Snake
River gushing out as springs from its beautiful banks. The group
is called "The Thousand Springs," and is supposed to be the
reappearance of two "Lost Rivers" that disappeared back in the sand
wastes.
]
Mountain lakes are where the lively little torrents stop to sleep. "The
sea," says Ruskin, "seems only to pause; the mountain lake to sleep and
to dream."
But after this sleep how they laugh and play--those baby rivers--as
they go dancing over the pebbles and down the falls; for in these lakes
they gather themselves together into a larger volume of water, and so,
of course, flow on with increased energy.
"As soon as a stream is fairly over the lake lip it breaks into
cascades, never for a moment halting, and scarce abating one jot of its
glad energy until it reaches the next basin. Then swirling and curving
drowsily (dropping off to sleep again!) through meadow and grove it
breaks forth anew into gray rapids and falls, leaping and gliding in
glorious exuberance of wild bound and dance down into another and yet
another lake basin."[12]
[Footnote 12: Muir, "The Sierra Nevada Mountains."]
Just as it is with human beings, a river seems to grow more thoughtful
and thrifty as it grows older; and, best of all, this thought and
thrift is for others--for the people of the plant world along its banks
and for its old parent, the sea. With the help of pebbles it puts money
in its savings bank and pays it out from time to time.
In seasons of flood it carries loads and loads of pebbles along. As the
flood goes down these pebbles are dropped and covered with the sediment
that settles along its banks. Then these pebbles begin to decay and so
enrich the soil. Later along comes another flood, takes the pebbles
out of the bank, carries them farther along, and, as the waters go
down, puts them back in the bank again. In course of time this kind of
fresh food from the decaying pebbles gets carried into the sea, where
it helps to furnish food and shell material for the shell-fish and raw
material to be worked up by the sea's rock mills.
[Illustration: WAYS OF A WANDERING RIVER]
III. The Machinery of the Rivers
To do all their great part in the world's work the rivers need only
time, enthusiasm, patience, machinery, and tools. All these the rivers
have, and the machinery they use and the engineering methods they
follow are much more modern than we would suppose. Take, for example,
the way in which rivers widen their banks. The current cuts with the
greatest force on the outside of bends, and the motion and effect is
practically that of a circular saw. This sawing is done on the largest
scale where the current meanders. Swinging from side to side it cuts
away both banks.
And what it cuts away it spreads over the valley by its back-and-forth
motion, much as men spread dirt with scrapers when they are grading a
road.
That's how crooked rivers make broad valleys. But they have to have the
help of us pebbles, too. We're hard to get along without! Notice, the
next time the river or the creek is up, the rolling, hopping motion of
the pebbles as they are carried along by the rushing water. It is these
pebbles grinding on the bottom and sides of the river's bed that help
most in this kind of valley deepening and widening. In the same way we
pebbles helped dig those grand affairs, the gorges and the canyons in
the mountains. The Grand Canyon of the Colorado is a part of our work.
In the widening of valleys the circular saws of crooked streams are
very useful, but there are other things at work. The rains dissolve
the soil and wash the banks away and slope them down; Jack Frost, with
his wedges, pries out both soil and rock; the little farmers with many
feet--the burrowing animals and insects--and the famous farmer with no
feet at all--the angleworm--loosen soil, and so help the river to carry
it away; and the ice, when the river breaks up in the spring, chisels
off the banks as it passes.
[Illustration: HOW RIVERS BUILD STONE BRIDGES
Natural bridges are made by the same agency that forms the
intermittent springs--the dissolving power of water--and, like the
springs, are characteristic of limestone regions because limestone
is readily dissolved in water. In the little model of a limestone
region "a" and "a" are "sink-holes"--saucer-shaped hollows
dissolved and washed into funnels through which the surface water
joins underground streams such as you see flowing beneath the two
"bs," which are natural bridges in the making.
The lower picture shows just how one of the bridge-builders looks
while at work, dissolving and wearing down the rock. The next two
pictures will help tell you two other ways in which rivers make
their own bridges.
]
If you have ever been in a machine-shop you must have noticed how a
planing-mill works away on a job it has been set to do, without anybody
watching it at all; and when it gets done with its job it stops, all
by itself. Such machinery is called "automatic," because, to a certain
extent, it runs its own affairs. A river, in planing down and reshaping
valley scenery, has an automatic stop. When it has cut its valley down
to sea level it stops, because, being then no higher than the sea, it
can no longer flow toward it.
[Illustration: AFTER A FEW CUPS OF TEA
When winding rivers get a few cups of tea--that is, are in
flood--they rush straight ahead and, while much of the water may
for a time still go on around the bend, some of it is forced
through openings in the rock and in time carves out a bridge. How
they do this is shown in the upper diagram on page 83.
]
But before this automatic stop shuts off their machinery the work that
rivers do is immense. The Mississippi River carries enough solid matter
to the Gulf every year to make a mountain a mile square and 268 feet
high.
[Illustration: YOU KNOW THIS BRIDGE, OF COURSE
The Natural Bridge of Virginia is an example of still another style
of river bridge-building. This bridge used to be part of the roof
of a cave and remained after the rest of the roof fell in.
]
When ordinary people want to cross a mountain they have to climb over
it. But do you know what a river does? It cuts its way right through
and makes what is called a water-gap--a great gate of stone that is
always open and through which the stream forever flows. All the river
used was tools and time. The tools were the sand and pebbles it swept
along. So in the course of ages, running like a band saw, the Potomac
made the water-gap at Harper's Ferry, the Delaware River the Delaware
Water-Gap.
HOW MOUNTAINS HELP MAKE THE WATER GATES
But how could a river do this? It couldn't flow up one side of the
mountain and down the other, could it? No, certainly not. What then?
Wherever you find a river cutting through a mountain range you may
be sure the river was there before the mountains rose, and that the
mountains rose so slowly the river kept right on in its old channel and
wore down the rock under that channel as fast as the mountains rose;
while, on either side, they could rise as high as they wanted to for
all the river cared!
GROWING MOUNTAINS AND THE EARTHQUAKES
But suppose, before I had explained how water-gaps are made I had told
you I could show you a mountain growing. You wouldn't have believed
it. Regions in which mountains are still rising, as on our Pacific
Coast, are liable to earthquakes. The reason is that as mountains rise
the rock layers of which they are made are strained dreadfully. Every
once in a while they crack and the rocks on either side of this crack
grind against each other. This makes the earth shake, much as the house
shakes when a heavy table is pushed across a bare floor.
If you want to see a job of river engineering that will make you catch
your breath, look over into some of the river canyons and gorges of the
West.
[Illustration: THE GREAT CUMBERLAND WATER-GAP
Here is the famous Cumberland Gap that the river cut through the
mountains; so cutting a great figure in United States history,
also, you remember. The picture shows the region as it looked in
early days.
]
A mile isn't much straight ahead, but a mile straight down and you on
your stomach, with your eyes just over the edge--it's an _awful_ long
way! Imagine yourself looking down a wall of rock like that, and the
bottom of the abyss so far off that it looks blue--that's a canyon!
AND YET THAT LITTLE RIVER DID IT ALL!
And now we are going down into the vastest canyon in the world, a
canyon so vast that it has already swallowed practically all the
words in the dictionary suitable to such scenery and still remains
undescribed--so all the skilled writers say who have tried their hands
at it. This is the Grand Canyon of the Colorado. Do you remember how
in "Alice in Wonderland" the cat disappeared and left nothing but its
smile? Well, the first time you see the Grand Canyon you feel as if it
had swallowed you and left nothing but your eyes! And when they tell
you that it was all done by that little river that you can just make
out threading its way along the bottom, you can't believe it! The total
length of the river's gorge--a canyon is just a long gorge--is some 400
miles. The part of it known as the Grand Canyon is a yawning abyss of
stone into which the river walls widen for a distance of 42 miles. The
Lower Colorado River, that dug this chasm in the rock, flows through a
vast table-land where rain seldom falls. But the river, which rises in
the Rocky Mountains, has a constant supply of water from the mountain
rains and the melting snow. The canyons you see branching from the main
gorge in our picture were cut by the Colorado's tributaries. Working
together on different sides, they carved out those rock masses that
look like oriental temples and have been named accordingly--the temples
of Brahma, Osiris, Zoroaster, and so on.
And here in this canyon is a splendid example of how the rivers, in
addition to all their other labors, write history. They helped to lay
down on the borders of the ancient sea the material out of which the
rocks were made. It is in the leaves in such books of stone that the
geologist reads the great events of world-making history. Moreover, the
rivers may be said to cut the leaves of the book when they dig down
through them, as in this immense library of the Grand Canyon.
[Illustration:
_From a photograph copyrighted by Fred Harvey_
AND WE PEBBLES HELPED DIG THE GRAND CANYON, TOO!
River water alone couldn't cut those canyons--the Grand Canyon and
the rest. The Colorado and its tributaries had to have grinding
tools and the tools were the pebbles they dragged over their
rock-beds; and thus, in the course of ages, wore them down and down
and down.
]
Busy, busy all the time--these rivers. But although they are always at
work they not only never forget to look beautiful but they beautify
everything they touch. At the outset the lines of a river valley are
rather straight and angular, as if the scenery were just being blocked
out by an artist, but as the valley grows older its slopes become more
gentle, the angles disappear into rounded forms, and the river itself
winds along in graceful lines, exactly reproducing what the great
English artist Hogarth called "the line of beauty."
[Illustration: THAT MIGHTY RIVER IN THE MEADOWS
Yon stream, whose sources run,
Turned by a pebble's edge,
Is Athabasca, rolling towards the sun,
Through the cleft mountain ledge.
The slender rill had strayed,
But for the slanting stone,
To evening's ocean, with the tangled braid
Of foam-flecked Oregon.
--Holmes.
]
Back of all the work of the rivers from year to year and age to age,
there seems always the thought of beauty as well as the thought of use.
They are evidently under an eternal law of service, of beauty, and of
change.
"The hills are shadows, and they flow
From form to form and nothing stands.
They melt like mists the solid lands;
Like clouds they shape themselves and go."
HIDE AND SEEK IN THE LIBRARY
Isn't Tennyson's "Brook" a beautiful title picture of a baby river
and its ways?
Speaking of human nature in rivers and apparent differences in
disposition, why is it that some of the rivers of California run
right through the mountain ranges from east to west--have evidently
cut their way--while others run along, meekly enough, between the
ranges? I'm sure from what we have learned about rivers that you
can tell how this happened as well as if you had been there when
the rivers were made; but if you can't think--after trying real
hard--you will find the answer in the Hide and Seek at the end of
the next chapter.
Beside being so prominent in the literature of the Bible and
so famous in history, the River Jordan is a most curious and
interesting stream, and every child should know about it. Here are
some of the things you will find: Why it is born partly grown, and
doesn't begin as a little stream, like the Mississippi; why it may
be said to be in both the tropical and temperate zones[13]; about
its two valleys, both of which it uses at the same time.[14]
[Footnote 13: Britannica.]
[Footnote 14: International.]
Another famous river over in that part of the world--it's the
biggest river in Western Asia, in fact--was born twins. See if you
can find such a river on the map. (The name of it is at the end of
the next chapter.) In the days of Alexander the Great these twin
rivers, which now unite in one after travelling along independently
for a while, were a good day's journey apart clear to the end. In
the article on this river in the Britannica, and in books of travel
you will find how, by a quaint and ingenious device, the river is
made to pump itself up hill and irrigate the fields; how history,
clear back to the beginning of civilization, is written in the
ruins of cities along its banks; how it used to put in part of its
time bounding the Roman empire, and how nowadays it is forced to
help support Arab river pirates and wild pigs.
Now let's go over into Africa with Doctor Livingstone and see how
a river can grind out a big, deep stone jar in solid rock.[15]
Rivers grind out these _pot-holes_ much as Indian women and the
American pioneers used to grind wheat and corn. (The river, you'll
find, uses pebbles for millstones.)
[Footnote 15: "The Expedition to the Zambesi," page 63. One of these
natural water-jars that Doctor Livingstone found was as wide as a well
and so deep it kept the water cool even under the broiling African sun.]
And what do you think of a waterfall big enough to swallow two
Niagaras? (It's the greatest waterfall in the world; so you must
have learned its name in your geography.) It's described on page
268 of Doctor Livingstone's book referred to in the foot-note. The
natives call it "The Fall of the Thundering Smoke." They wonder how
water can smoke, and so that you can see the "smoke" twenty miles
away. You'll wonder, too, until you learn the reason.