(MAY)
When April steps aside for May,
Like diamonds all the rain-drops glisten;
Fresh violets open every day;
To some new bird each hour we listen.
--_Lucy Larcom._
THE FAIRYLAND OF CHANGE
What a wonderful world it is, this world of green fields and perfume
and blossoms of pink and gold! Where did it come from? How did it get
here out of the white winter? That bleak and barren winter that lay all
around us everywhere only a few short weeks ago?
Just suppose we had never seen apple trees in bloom, as we are now
seeing them everywhere, and somebody should show us a little brown
seed, and a piece of bark, and a piece of root, and a green leaf, and
a blossom, and an apple, and tell us they grew out of each other--were
all made of the very same stuff.
Well, just as sure as anything, you wouldn't believe it. I wouldn't
believe it. We simply couldn't! But we've had this sort of thing all
around us ever since we can remember, and we've got so used to it we
don't see anything wonderful about it. It _is_ wonderful just the same.
The Colossus of Rhodes, and Jupiter of Olympia, and the lighthouse of
Alexandria, and all the other Seven Wonders of the World that people
used to go so far to see, weren't anything to it.
And to this day, how it all comes about is as much of a mystery as
ever. Yet Nature does it right before our eyes, and over and over and
over again! Even I, old as I am, and as much as I know, _I_ don't know
how she does it, but I do know how it all started; how Nature first
began to change one thing into another. It was when she began making
marbles, granites, and other kinds of rock out of other kinds. That
was ages before she changed little brown seeds into big trees with
pink blossoms and red apples on them, or little brown cocoons into big
golden butterflies, or anything like that.
I. In the Fairyland of Change
Ahem! Ahem! (Pebble coughing.)
I caught cold some several million years ago and I haven't got over it
yet. That's why I'm a granite pebble instead of a slate pebble, or a
sandstone pebble, or anything common. It's a part of the story of the
fairyland of change, this cold of mine.
Ahem!
Would you mind getting me a lump of sugar? I don't want it for my
cold--it never does that any good--but because a lump of sugar goes so
well with this part of my story.
You notice the sugar lump is made up of little crystals, little
building blocks just as I am, just as all granites are. And the
crystals in the sugar and in the stone were made in the same way--by
first heating and then cooling the material out of which they are made.
[Illustration: THE CRYSTAL FAIRIES IN THE SUGAR-BOWL]
When the earth's surface first cooled, the melted rock is supposed
to have changed to granite. Melted rock, under the same conditions,
does that to-day. So, for a while, granite must have been all the kind
of rock there was. There was as yet no sandstone, no shells or bones
to make limestone, no pebbles to help make conglomerate or "pudding
stone," no ground-up rock and soil to make slate.
The rocks of the earth have been made over so many times that it is not
probable that any of the granites now "living" (so to speak) are the
same rocks that were made when the earth first cooled, but you can see
that we have a right to say what I was careful to say when I introduced
myself to you in the first chapter, that we belong to one of the _very
oldest families_--we Granites.
Ahem!
There is a variety of rock--a crystallized rock--with bands all through
it, called gneiss (say "nice"). Gneiss is made from all kinds of rock
including, of course, conglomerate; that is to say "pudding stone"[16]
warmed over.
[Footnote 16: "Pudding stone" is a rock with pebbles all through it,
like the plums in a Christmas pudding. Its book name is "conglomerate."]
"And what they did not eat that night, the queen next morning fried!"
DOWN IN THE GREAT MELTING-POT
But how is old rock warmed over and made into new? You might easily
guess that as the heart of the earth is melted rock the rock layers
lying next to it would be melted, too, and so started on their way to
becoming crystallized rock. Crystallization in rock takes place from
the surface down, in the same way that maple syrup turns to sugar, as
it does if allowed to stand undisturbed. So, as the central mass of
rock is cooling from above toward the centre, we may suppose granite is
still being formed away down there, miles under our feet.
But there are other ways in which rocks make their own heat--rocks far
above this central molten heart of the world. One of these ways might
remind you of how the mother hen gets her chickens to come out of the
eggs, for rocks hatch out new rocks by sitting on one another!
[Illustration: THREE CHAPTERS IN THE STORY OF MARBLE
If you're ever in New York City up around 192d Street, you can read
the three chapters in the life of a piece of marble right in the
rocks themselves, for there you'll see this mass of rock with that
granite dike pushing its way through. The rock on either side of
the dike is limestone, and this limestone, owing to the heat of
the lava which afterward hardened and became a "dike," is full of
crystals; that is, began to turn to marble because of the heat. See
how the lava crumpled the limestone as it pushed its way up into
the original crack?
]
The pressure of the upper rocks generates heat in those beneath.
Then when these deeply buried rocks come up into the upper world as
parts of mountain chains, and the covering of the softer rocks is,
by the rivers and by weathering, worn away, we find the granite. The
wrinkling of the rocks which makes mountains also creates immense
pressure, and this is another great source of made-over rock. Such rock
is found almost entirely in mountain regions. Some rocks, as shown
in pebbles stretched out like a piece of gum, are heated by pressure
without being crystallized. Often one of these stretched pebbles is
the only thing in a crystallized rock that shows what kind of rock it
was originally, all the finer material in it has been so changed. The
deeper down in the earth the rocks are the more apt they are to be
crystallized, because the rocks piled above them help to hold in the
heat, just as thick blankets keep you warmest on a cold winter night.
KINDS OF "METAMORPHIC" ROCK
Rock of any kind may be changed to crystallized rock. Where the
conditions are not favorable for crystallization the rock is made more
solid, and material soaked out of the rocks above filters down into it.
The lower layers of sandstone may become almost as solid as glass, and
are then called "quartzite." Clay rocks are hardened into slate. Rocks
changed in any of these ways are called "metamorphic" rock, from two
Greek words meaning "to form over." But by "metamorphic" is usually
meant rock that has been crystallized.
NICE HATCHING TEMPERATURE FOR ROCKS
I compared the hatching of new rocks to the hatching of new chickens,
because it is done by the rocks sitting on one another. But chicken
hatching and rock "hatching" are alike in still another way. The rocks
need heat, but not too much heat. Too much heat melts them. It is only
when they have cooled down a good deal that they begin to crystallize;
and that, you see, wastes time.
A nice hatching temperature for rocks is between 500 and 1000 degrees
Fahrenheit.
But we might also compare Mother Nature's way of changing rocks to the
cooking that goes on in our kitchens. She uses not only heat, but water
and other things, including salt and soda. Both the salt and some of
the water in the rocks comes from--you'd hardly guess it--the seas! Not
the seas of to-day, but the seas of yesterday, when these rocks were
made. Then the pores were filled with water and the water has been kept
shut in down there by the rocks above ever since.
From this sea water comes the salt. The salt in the water, when heated,
helps to dissolve the rocks so that the different materials in them can
separate and come together again in new ways, and so form new rocks.
You know when you go to the lavatory to change your hands from dark to
light what a lot of difference it makes whether the water is hot or
cold and whether you use soap. The soap helps dissolve the dirt on your
hands just as the salt helps dissolve the rocks.
The soda which Nature also uses is particularly good for dissolving
rock that will hardly dissolve without it; silica, for instance, out of
which are made the hardest of the sand grains, the sand in sandstone,
the sharp, glassy edges of grass blades, and the blades of wheat, and
the stalks of corn. Whenever there is a great deal of silica in rock
you find soda mixed right with it. This, having the rocks already
salted and mixed with soda before putting them in the oven, Mother
Nature has always found _so_ convenient!
ONE PEBBLE MAY PLAY MANY PARTS
I, in my time, may have been many kinds of rock. First, heaved up out
of the sea by the earliest wrinkling of the cooling earth as granite;
then weathered away into soil and carried by rivers to the sea, where I
was remade the first time, maybe, as part of the "dough" in a pudding
stone; then up again in an earth wrinkle and again back to sea, this
time to be made into some one of the clay stones, and then back to
granite again.
Anyhow here I am, a little freckled granite pebble talking myself red
in the face because I've got so much to say, such wonderful things to
tell, and only a few hundred pages to tell it in!
II. How Do They Know?
But, after all, how do they know that one rock changes into another? No
one ever caught a rock doing this, did they?
Not quite, but almost. To explain, I must first tell you about the
fossils that are found in stone. Haven't you often noticed in marble
curious figures that reminded you of sea-shells? They were sea-shells
but have been turned to stone, and things similarly changed while still
keeping their original form are called "fossils."
When the plants and the shell creatures of the sea die they fall to the
bottom, and mud and sand settles over them and closes them in, much as
you shut leaves and flowers between the pages of a book. But while the
book presses the leaves of flowers out of shape these bodies of the
water-plants and shell creatures are slowly enclosed in a soft mass of
mud that doesn't change their shapes at all. Then the particles that go
to make up the soft bodies of these buried things are slowly dissolved
away, and the minerals in the water and mud above them soak in and
take their places. It's like passenger after passenger in a car getting
up and other passengers taking the vacant places. Finally this mass of
limey shells becomes buried deep under the sea, is turned to limestone,
and when in course of time this part of the seashore rises--as we know
shores have a way of doing--or is wrinkled up into a mountain, this
limestone becomes a part of the face of the land.
[Illustration:
_From a photograph by the American Museum of Natural History_
STORY OF THE LITTLE JEWEL-BOX
A kind of jewel-box? Yes, the kind geologists call a "geode." It
began as a piece of limestone in which the underground waters had
dissolved a cavity. But these waters had already, in solution,
quartz which they had dissolved from quartz rock, and this quartz,
deposited little by little in the cavity, formed into crystals. The
quartz also made the surrounding walls more solid, so that when the
mass of limestone containing this pocket was cut away by erosion
this jewel-box remained, and, being rolled about in streams or by
the lap and plunge of waves, it was rounded.
]
WOULDN'T WE SAY THE SAME THING?
Now suppose where some great granite rock stood up through layers of
other kinds of rock--looking as if it had pushed itself through like
the great granite boss on which Edinburgh Castle stands--you found
that wherever this intruder touched the other rock that rock was
crystallized. If we had just found all this out for ourselves, as the
geology people found it, we would say, just as they said:
[Illustration: FATHER, GRANDFATHER, AND THE CHILDREN IN THE PORPHYRY
FAMILY
In this piece of porphyry you see three generations, all living
under one roof, as it were. Notice that six-sided crystal near the
centre? Compare it with other good-sized crystals that haven't
any distinctive shape. The reason for the difference is that the
shapeless ones have had some of their substance taken away to form
the smaller crystals. The dark mass is lava. In it the big crystals
formed. Then, from most of the big crystals the lava reabsorbed
material, and this material later turned into little crystals--the
"grandchildren" of the three generations.
]
"I wonder what the granite did to the limestone and the other rocks
around it to make them 'sugar,' or, as we say when speaking of rocks,
'crystallize'? Syrup sugars when it is heated and then cooled without
stirring. I wonder if this intruding mass that is now granite didn't
spout up, in melted form, from down in the earth, and heat the rocks
on either side as it burst its way through. Then both this hot rock and
its neighbors cooled and crystallized. That's it!"
[Illustration: SPLITTING MARBLE ROCKS IN THE QUARRY
This is a scene in a marble-quarry. The men are splitting up a
120-ton block. A writer in _Scribner's Magazine_, in which this
illustration originally appeared, also describes the process. The
wedges, carefully greased, are inserted in the drill-holes which,
for a horizontal split, are neither close together nor very deep,
as that is the natural plane of cleavage between the strata. Two
men with sledges go down the line giving each wedge a blow--not
too hard. Then two more men follow, and in go the wedges a little
farther. You see it wouldn't do to rush matters, or you'd fracture
the marble. The operation is so delicate, indeed, that the foreman
himself gives the final blows. Then the marble cracks from hole to
hole. For the vertical splits the holes, you notice, are closer
together. They are also deeper.
]
In some places you find these granite masses in great bosses, or
domelike rocks; elsewhere in long strips, like an iron bar thrust
through other rocks; in still other places in great slabs between other
rocks, like a warming pan pushed between the bed-sheets on a cold
winter night; but everywhere it touches other rocks these neighbors are
crystallized.
Now, coming back to our friends the fossils, we sometimes find
limestone bordering one of these intrusive marble rocks with fossils in
it, shading off into limestone containing the same kind of fossils. As
you get closer to the granite mass the fossils in the marble gradually
fade away until you come to marble in which there are no fossils at all.
So there we get the whole story of the life, not only of marble but of
granite, and what happened to them in "The Fairyland of Change" and how
it happened:
_Chapter I._--The limestone was made in the sea and the shell creatures
helped to make it.
_Chapter II._--Hot melted rock from the inside of the earth broke its
way up through these limestone beds.
_Chapter III._--Then, as the melted rock cooled, it changed to granite,
and the limestone on either side, being first heated and then cooled,
crystallized and changed to marble.
Men of science have still other ways of working out this problem as to
whether and how and why one kind of rock changes into another.
"But," we might say, "aren't they satisfied? We are. It's all plain
enough to us now that one kind of rock does change into another. Then
why do these geologist people go on getting more evidence when they've
already got enough? It's like a boy learning two lessons when he only
has to recite in one; and whoever _heard_ of such a thing!"
THESE BOYS JUST LOVE TO STUDY
The answer is that this "going on" is one of the many delights of
study, particularly in Nature's books, when once you get the habit.
[Illustration:
_From a photograph by Frith & Co., Ltd., Reigate_
THE MARBLE ROCKS AT JABALPUR
The gorge of the "Marble Rocks," near Jabalpur, India, is a mile
long and of an unearthly beauty of which even this little picture
will give you some idea. The walls gleam white and golden in the
sun. They are not really marble but limestone, which, as you will
learn in this chapter, is the stone that becomes marble in "the
fairyland of change." It looks as if nature had begun the making
of marble columns in those cliffs, doesn't it? This is because the
cliff is cut up by joints. You can also make out in one of the
"pillars" the strata, or horizontal divisions of the rock, as it
was laid down in the sea.
]
Among other things, the scientists search the pockets of the rocks,
so to speak, for further evidence as to whether one kind changes into
another. Chemistry is a great help in doing this, and, of course,
the microscope. They find in this way that rocks that are full of
crystals, such as granite and marble, and that look so different
from the rocks that are not crystallized--such as limestone and
sandstone--have in them the very same substances--silica, lime, potash,
iron, and so on.
And again they put the oysters on the witness stand. (You remember
how, long ago, oysters helped tell that mountains were once a part of
the sea bottom.) They put a piece of limestone in a certain acid, and
it bubbles and gives off a certain kind of gas. Then they do the same
thing to an oyster-shell, and it gives out the same kind of gas. Then
they try it on a piece of marble and out comes that very gas again! So
all three--the limestone, the oyster-shell, and the marble--must be
pretty close relations. Marble is just oyster and other shells warmed
up and then allowed to cool.
But they don't stop here--these students of the rocks. It isn't enough
that all these facts point to one conclusion. They want to actually
_try it out_. So what do they do but change chalk--which is a kind of
very soft limestone--into marble in the laboratory? This they do by
heating the chalk and then cooling it under immense pressure.
III. The Fairies of the Fairyland of Change
If there really are fairies in this deep-down fairyland of change--and
surely there must be--I should say they were the very same fairies we
find in a lump of sugar--the crystals. For it is when these crystals
take different shapes--the very thing fairies are always doing, you
know--that things change into something else, so different you can
hardly believe it. One could easily believe that charcoal and coal are
related, they look so much alike in the face; but who would say that a
piece of charcoal and a diamond were made of the very same stuff? They
are. But diamonds are made of crystals and charcoal is not; and that
must be it. The carbon of the charcoal was never touched by the wand of
the Crystal Fairy.
[Illustration: SIX MEMBERS OF THE CRYSTAL FAMILY
Introducing six interesting members of the crystal family. The crystals
of common salt and of gold, among others, take the form shown at _A_.
Alum and diamonds crystallize as shown at _C_; while _B_ and _F_ belong
to a system of crystals which we find built up into ice and arsenic.
_D_ and _E_ are building-blocks for green vitriol, borax, and sulphate
of soda.]
A strange thing is that big crystals are always made up of little
crystals. So what looks like one crystal is really a United States
of crystals, all like each other and each like all of them put
together, much as our federal government repeats the form of the State
governments, and the State governments duplicate the government at
Washington on a smaller scale.
[Illustration: THE SAND GRAINS AND THE CRYSTAL FAIRIES
The crystal fairies often give battered sand grains a new lease of
life and these pictures show how they do it. Fig. "_a_" is a single
sand grain which has grown into crystal form; "_b_" shows parallel
growths about a grain; "_c_" is a group of neighboring grains that have
crowded each other so in their growth that the crystal facets have been
destroyed. Sounds odd to speak of sand grains "growing," doesn't it?
But they do!]
But why do the little crystals always come together in just such a way
as to make big crystals shaped exactly like themselves?
Goodness knows!
But whatever the how and the why of it may be, not only do the crystal
people stick as closely to the family pattern in dress as the Scotch
Highlanders do to the plaids of their clans, but the crystals are
clannish in another way. When a clay rock, for example, is dissolved
by the heat, moisture, and chemicals down in the land of change,
the particles of the same kind that are scattered through it hunt
each other out, and ever after cling together, like Emmy Lou and her
"nintimate friends." You've noticed how "spotty" granite is, haven't
you? This is because it is made up of different kinds of minerals; but,
although the crystals in all follow the granite pattern, the particles
of each kind of mineral "flock together." The feldspars and the micas
never mix.
JUST TRY IT WITH A PIECE OF PAPER
Now take a piece of writing paper and roll it into a tube and I'll show
you something else. Stand the roll up between your two hands and press
down on the top. It takes a good deal of pressure to bend or break it,
doesn't it? Now lay it on its side and squeeze. It breaks right away.
But how should the crystals in a piece of granite know that a column
of anything will stand so much more weight when the pressure comes on
the ends than when it comes on the sides? They seem to know; for I'll
tell you what they do, away down there in the dark of the earth. The
crystals stand at right angles to the pressure on the rock in which
they are forming. Sometimes, because of the movements of the earth
as it shrinks and cracks, the crystals already formed in granite are
crushed over on their sides. Then, in course of time, they form again,
but _this_ time they stand upright, with their "heads and shoulders"
against the burden--little Atlases supporting the world! And they
not only manage to get up and stand up straight when re-formed under
pressure, but they stand closer together than they did before; they
close up ranks, like soldiers with serious business before them.
A crystal is made up of molecules, that is to say, little parts
of itself. You can't see a molecule; you just have to think it.
Each different thing in the world--as salt and sugar, boys and
bumble-bees, little girls and butterflies--is made up of its own kind
of molecules or little parts of itself. In order to grasp the idea of
certain scientific facts, the men of science thought of the molecules
themselves as being made of little bits of _themselves_, which the
scientists called "atoms." Now they find that it is necessary--in
order to work out still further their ideas of how things are made
and done and changed, in this wonderful mystery we call the world--to
imagine these atoms as made up of what they call "electrons." You
mustn't think, however, that this is all mere fancy. We can, of course,
think of anything as made up of small particles or parts of itself
which we can call "molecules," and that these molecules are made of
still smaller parts which we can call "atoms." But there is reason to
believe that while each different kind of thing is made of its own
kind of molecules and their atoms, all the atoms are made of the same
thing--electrons or little bits of electricity. For reasons which need
not be gone into here, it is known that electrons actually exist. These
electrons are so much smaller than an atom that there is as much room
for them to move around in an atom as there is for the planets to move
around the sun.
And they _do_ move--travelling round and round. There are, even in so
small a thing as a grain of sand, untold numbers of these circling
worlds; systems like the sun with its planets and other vast star
systems of the sky.
And that, it is thought, may be one of the secrets of the continual
change of things; clay rock changing to granite, granite to soil, soil
to fruit, fruit to children, and so on--everything on the move and the
electrons doing the moving--carrying the changes, so to speak--these
wonderful little myriad messenger boys of the universe!
HIDE AND SEEK IN THE LIBRARY
Don't imagine, for all I've talked so long about them, that I've
told you everything there is to know about the crystal fairies. For
example, did you know that if it wasn't for the crystal people we
wouldn't have any ice? (_Ice._)
You will also find that if it wasn't for ice--ice and the
Greeks--we wouldn't have the word "crystal" at all. (_Crystal._)
One of the most striking things in the whole conduct of these
clever crystal folks you will find in reading about ice. If it
wasn't for a peculiar--a very peculiar--habit the ice crystals
have, all the waters of the world that ever freeze at all, would
freeze solid to the bottom and never _would_ thaw out!
I'll tell you this much about it:
While everything else in the world--including boys and
girls--contracts when it gets cold, ice expands, and so becomes
lighter than water, and so floats.
And yet the ice crystals know how to contract as well as expand,
and that's why ice sometimes builds stone walls, as we will see
when we come to study "The Stones of the Field" in July.
Shaking still water that is cold enough to freeze but hasn't frozen
makes the crystal fairies get very busy in their ice factories.
And it looks very much as if the fairies themselves warmed up with
their work; for, after this shaking, the temperature of the water
rises ten degrees at the very same time it is freezing!
You will also find that when the weather is cold enough ice itself
freezes, gets harder and harder with the cold; that ice will melt
ice; that two blocks of ice will grow into one if you give them a
chance; that ice crystals are apt to be born twins; that these twin
crystals are fond of gardening--at least, they raise "ice flowers";
that the ice crystals are so punctual in their coming and going in
water that they are used to help place the markings on thermometers
just right, so that we can tell exactly how cold or hot we are.
All this just about the crystals of the ice, but the work of the
crystal people in making snowflakes is even more wonderful. In
the bound volumes of St. Nicholas for March, 1882, in your Public
Library you will find a most interesting account of a man in
Vermont who began studying snowflakes and taking their pictures
when he was a boy. He's known all over the world as the great
authority on snowflakes. In the Encyclopedia Americana you will
find a long article by him in which he tells the many interesting
things he has learned about the ways of the fairies of the snow And
how many pictures do you suppose he has in his snowflake gallery
now? Over a thousand, and no two alike!
Just to think! Some of these wonderful little people of the
fairyland of change sit at the table with us at every meal--the
sugar crystals. And they are among the most interesting members of
the family. Under the word _Sugar_ you will find that the sugar
crystals themselves eat and grow. But what do you suppose they eat?
Not sugar. (You may easily guess, however, they have a sweet tooth.)
Yes, and at their home table, before they come to _your_ home
table, they have their regular meals, and they are not allowed a
second helping until they have eaten the first!
Answers to Conundrums in H. & S. No. 4
The east and west rivers in California were there before the
mountains rose and so cut their way through; while the north and
south rivers between the ranges owe their origin to the mountains
themselves.
The big twin river referred to is the Euphrates.
The greatest falls in the world are the Victoria Falls on the
Zambesi.