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Title: The Fairy-Land of Science
Author: Buckley, Arabella Burton (1840-1929)
Illustrator: Cooper, James Davis (1823-1904)
Date of first publication: 1878
Edition used as base for this ebook:
   Philadelphia: J. B. Lippincott, 1888
Date first posted: 19 October 2009
Date last updated: 19 October 2009
Project Gutenberg Canada ebook #403

This ebook was produced by:
Marcia Brooks, woodie4
& the Online Distributed Proofreading Team
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available by the Internet Archive/American Libraries




  FAIRY-LAND
  of
  SCIENCE

  BUCKLEY


  [Illustration: Fig 29.--GLACIER CARRYING DOWN STONES. See p. 119.]


  THE

  FAIRY-LAND OF SCIENCE

  BY

  ARABELLA B. BUCKLEY


  AUTHOR OF 'A SHORT HISTORY OF NATURAL SCIENCE,'
  'BOTANICAL TABLES FOR YOUNG STUDENTS,' ETC.


  ILLUSTRATED


      "For they remember yet the tales we told them
        Around the hearth, of fairies, long ago,
      When they loved still in fancy to behold them
        Quick dancing earthward in the feathery snow.

      "But now the young and fresh imagination
        Finds traces of their presence everywhere,
      And peoples with a new and bright creation
        The clear blue chambers of the sunny air."

                                      _Folk Lore._


  PHILADELPHIA:
  J. B. LIPPINCOTT COMPANY.
  1888.




PREFACE.


The Ten Lectures of which this volume is composed were delivered last
spring, in St. John's Wood, to a large audience of children and their
friends, and at their conclusion I was asked by many of those present to
publish them for a child's reading book.

At first I hesitated, feeling that written words can never produce the
same effect as _viva-voce_ delivery. But the majority of my juvenile
hearers were evidently so deeply interested that I am encouraged to
think that the present work may be a source of pleasure to a wider
circle of young people, and at the same time awaken in them a love of
nature and of the study of science.

The Lectures have been entirely rewritten from the short notes used when
they were delivered. With the exception of the first of the series, none
of them have any pretensions to originality, their object being merely
to explain well-known natural facts in simple and pleasant language.
Throughout the whole book I have availed myself freely of the leading
popular works on science, but have found it impossible to give special
references, as nearly all the matter I have dealt with has long been
the common property of scientific teachers.

I am much indebted to Mr. J. Cooper for the zeal and assiduity he has
shown in carrying out my suggestions for illustrations. All the
engravings, with one exception, were executed under his superintendence.

                                                    ARABELLA B. BUCKLEY.

_Christmas, 1878._




  TABLE OF CONTENTS.


  LECTURE I.
                                                   PAGE
  THE FAIRY-LAND OF SCIENCE: HOW TO ENTER IT;
  HOW TO USE IT; AND HOW TO ENJOY IT                  1


  LECTURE II.

  SUNBEAMS, AND THE WORK THEY DO                     26


  LECTURE III.

  THE AERIAL OCEAN IN WHICH WE LIVE                  50


  LECTURE IV.

  A DROP OF WATER ON ITS TRAVELS                     73


  LECTURE V.

  THE TWO GREAT SCULPTORS--WATER AND ICE             99


  LECTURE VI.

  THE VOICES OF NATURE, AND HOW WE HEAR THEM        124


  LECTURE VII.

  THE LIFE OF A PRIMROSE                            150


  LECTURE VIII.

  THE HISTORY OF A PIECE OF COAL                    171


  LECTURE IX.

  BEES IN THE HIVE                                  193


  LECTURE X.

  BEES AND FLOWERS                                  212




THE

FAIRY-LAND OF SCIENCE.

LECTURE I.

HOW TO ENTER IT; HOW TO USE IT; AND HOW TO ENJOY IT.


[Illustration]

I have promised to introduce you to-day to the fairy-land of science,--a
somewhat bold promise, seeing that most of you probably look upon
science as a bundle of dry facts, while fairy-land is all that is
beautiful, and full of poetry and imagination. But I thoroughly believe
myself, and hope to prove to you, that science is full of beautiful
pictures, of real poetry, and of wonder-working fairies; and what is
more, I promise you they shall be true fairies, whom you will love just
as much when you are old and greyheaded as when you are young; for you
will be able to call them up wherever you wander by land or by sea,
through meadow or through wood, through water or through air; and though
they themselves will always remain invisible, yet you will see their
wonderful power at work everywhere around you.

Let us first see for a moment what kind of tales science has to tell,
and how far they are equal to the old fairy tales we all know so well.
Who does not remember the tale of the "Sleeping Beauty in the Wood," and
how under the spell of the angry fairy the maiden pricked herself with
the spindle and slept a hundred years? How the horses in the stall, the
dogs in the court-yard, the doves on the roof, the cook who was boxing
the scullery boy's ears in the kitchen, and the king and queen with all
their courtiers in the hall remained spell-bound, while a thick hedge
grew up all round the castle and all within was still as death. But when
the hundred years had passed the valiant prince came, the thorny hedge
opened before him bearing beautiful flowers; and he, entering the
castle, reached the room where the princess lay, and with one sweet kiss
raised her and all around her to life again.

Can science bring any tale to match this?

Tell me, is there anything in this world more busy and active than
water, as it rushes along in the swift brook, or dashes over the stones,
or spouts up in the fountain, or trickles down from the roof, or shakes
itself into ripples on the surface of the pond as the wind blows over
it? But have you never seen this water spell-bound and motionless? Look
out of the window some cold frosty morning in winter, at the little
brook which yesterday was flowing gently past the house, and see how
still it lies, with the stones over which it was dashing now held
tightly in its icy grasp. Notice the wind-ripples on the pond; they have
become fixed and motionless. Look up at the roof of the house. There,
instead of living doves merely charmed to sleep, we have running water
caught in the very act of falling and turned into transparent icicles,
decorating the eaves with a beautiful crystal fringe. On every tree and
bush you will catch the water-drops napping, in the form of tiny
crystals; while the fountain looks like a tree of glass with long
down-hanging pointed leaves. Even the damp of your own breath lies rigid
and still on the window-pane frozen into delicate patterns like
fern-leaves of ice.

All this water was yesterday flowing busily, or falling drop by drop, or
floating invisibly in the air; now it is all caught and spell-bound--by
whom? By the enchantments of the frost-giant who holds it fast in his
grip and will not let it go.

But wait awhile, the deliverer is coming. In a few weeks or days, or it
may be in a few hours, the brave sun will shine down; the dull-grey,
leaden sky will melt before him, as the hedge gave way before the
prince in the fairy tale, and when the sun beam gently kisses the frozen
water it will be set free. Then the brook will flow rippling on again;
the frost-drops will be shaken down from the trees, the icicles fall
from the roof, the moisture trickle down the window-pane, and in the
bright, warm sunshine all will be alive again.

Is not this a fairy tale of nature? and such as these it is which
science tells.

Again, who has not heard of Catskin, who came out of a hollow tree,
bringing a walnut containing three beautiful dresses--the first glowing
as the sun, the second pale and beautiful as the moon, the third
spangled like the star-lit sky, and each so fine and delicate that all
three could be packed in a nut? But science can tell of shells so tiny
that a whole group of them will lie on the point of a pin, and many
thousands be packed into a walnut-shell; and each one of these tiny
structures is not the mere dress but the home of a living animal. It is
a tiny, tiny shell-palace made of the most delicate lacework, each
pattern being more beautiful than the last; and what is more, the minute
creature that lives in it has built it out of the foam of the sea,
though he himself appears to be merely a drop of jelly.

Lastly, anyone who has read the 'Wonderful Travellers' must recollect
the man whose sight was so keen that he could hit the eye of a fly
sitting on a tree two miles away. But tell me, can you see gas before it
is lighted, even when it is coming out of the gas-jet close to your
eyes? Yet, if you learn to use that wonderful instrument the
spectroscope, it will enable you to tell one kind of gas from another,
even when they are both ninety-one millions of miles away on the face of
the sun; nay more, it will read for you the nature of the different
gases in the far distant stars, billions of miles away, and actually
tell you whether you could find there any of the same metals which we
have on the earth.

We might find hundreds of such fairy tales in the domain of science, but
these three will serve as examples, and we must pass on to make the
acquaintance of the science-fairies themselves, and see if they are as
real as our old friends.

Tell me, why do you love fairy-land? what is its charm? Is it not that
things happen so suddenly, so mysteriously, and without man having
anything to do with it? In fairy-land, flowers blow, houses spring up
like Aladdin's palace in a single night, and people are carried hundreds
of miles in an instant by the touch of a fairy wand.

And then this land is not some distant country to which _we_ can never
hope to travel. It is here in the midst of us, only our eyes must be
opened or we cannot see it. Ariel and Puck did not live in some unknown
region. On the contrary, Ariel's song is

    "Where the bee sucks, there suck I;
    In a cowslip's bell I lie;
    There I couch when owls do cry.
    On the bat's back I do fly,
    After summer, merrily."

The peasant falls asleep some evening in a wood, and his eyes are opened
by a fairy wand, so that he sees the little goblins and imps dancing
round him on the green sward, sitting on mushrooms, or in the heads of
the flowers, drinking out of acorn-cups, fighting with blades of grass,
and riding on grasshoppers.

So, too, the gallant knight, riding to save some poor oppressed maiden,
dashes across the foaming torrent, and just in the middle, as he is
being swept away, his eyes are opened, and he sees fairy water-nymphs
soothing his terrified horse and guiding him gently to the opposite
shore. They are close at hand, these sprites, to the simple peasant or
the gallant knight, or to anyone who has the gift of the fairies and can
see them. But the man who scoffs at them, and does not believe in them
or care for them, he _never_ sees them. Only now and then they play him
an ugly trick, leading him into some treacherous bog and leaving him to
get out as he may.

       *       *       *       *       *

Now, exactly all this which is true of the fairies of our childhood is
true too of the fairies of science. There are _forces_ around us, and
among us, which I shall ask you to allow me to call _fairies_, and these
are ten thousand times more wonderful, more magical, and more beautiful
in their work, than those of the old fairy tales. They, too, are
invisible, and many people live and die without ever seeing them or
caring to see them. These people go about with their eyes shut, either
because they will not open them, or because no one has taught them how
to see. They fret and worry over their own little work and their own
petty troubles, and do not know how to rest and refresh themselves, by
letting the fairies open their eyes and show them the calm sweet
pictures of nature. They are like Peter Bell of whom Wordsworth wrote:--

    "A primrose by a river's brim
    A yellow primrose was to him,
    And it was nothing more."

But we will not be like these, we will open our eyes, and ask, "What are
these forces or fairies, and how can we see them?"

Just go out into the country, and sit down quietly and watch nature at
work. Listen to the wind as it blows, look at the clouds rolling
overhead, and the waves rippling on the pond at your feet. Hearken to
the brook as it flows by, watch the flower-buds opening one by one, and
then ask yourself, "How all this is done?" Go out in the evening and see
the dew gather drop by drop upon the grass, or trace the delicate
hoar-frost crystals which bespangle every blade on a winter's morning.
Look at the vivid flashes of lightning in a storm, and listen to the
pealing thunder: and then tell me, by what machinery is all this
wonderful work done? Man does none of it, neither could he stop it if he
were to try; for it is all the work of those invisible _forces_ or
_fairies_ whose acquaintance I wish you to make. Day and night, summer
and winter, storm or calm, these fairies are at work, and we may hear
them and know them, and make friends of them if we will.

There is only one gift we must have before we can learn to know them--we
must have _imagination_. I do not mean mere fancy, which creates unreal
images and impossible monsters, but imagination, the power of making
pictures or _images_ in our mind, of that which _is_, though it is
invisible to us. Most children have this glorious gift, and love to
picture to themselves all that is told them, and to hear the same tale
over and over again till they see every bit of it as if it were real.
This is why they are sure to love science if its tales are told them
aright; and I, for one, hope the day may never come when we may lose
that childish clearness of vision, which enables us through the temporal
things which are seen, to realize those eternal truths which are unseen.

If you have this gift of imagination come with me, and in these lectures
we will look for the invisible fairies of nature.

Watch a shower of rain. Where do the drops come from? and why are they
round, or rather slightly oval? In our fourth lecture we shall see that
the little particles of water of which the rain-drops are made, were
held apart and invisible in the air by _heat_, one of the most wonderful
of our forces[1] or fairies, till the cold wind passed by and chilled
the air. Then, when there was no longer so much heat, another invisible
force, _cohesion_, which is always ready and waiting, seized on the tiny
particles at once, and locked them together in a drop, the closest form
in which they could lie. Then as the drops became larger and larger they
fell into the grasp of another invisible force, _gravitation_, which
dragged them down to the earth, drop by drop, till they made a shower
of rain. Pause for a moment and think. You have surely heard of
gravitation, by which the sun holds the earth and the planets, and keeps
them moving round him in regular order? Well, it is this same
gravitation which is at work also whenever a shower of rain falls to the
earth. Who can say that he is not a great invisible giant, always
silently and invisibly toiling in great things and small whether we wake
or sleep?

Now the shower is over, the sun comes out, and the ground is soon as dry
as though no rain had fallen. Tell me, what has become of the
rain-drops? Part no doubt have sunk into the ground, and as for the
rest, why you will say the sun has dried them up. Yes, but how? The sun
is more than ninety-one millions of miles away; how has he touched the
rain-drops? Have you ever heard that invisible waves are travelling
every instant over the space between the sun and us? We shall see in the
next lecture how these waves are the sun's messengers to the earth, and
how they tear asunder the rain-drops on the ground, scattering them in
tiny particles too small for us to see, and bearing them away to the
clouds. Here are more invisible fairies working every moment around you,
and you cannot even look out of the window without seeing the work they
are doing.

If, however, the day is cold and frosty, the water does not fall in a
shower of rain; it comes down in the shape of noiseless snow. Go out
after such a snow-shower, on a calm day, and look at some of the flakes
which have fallen; you will see, if you choose good specimens, that they
are not mere masses of frozen water, but that each one is a beautiful
six-pointed crystal star. How have these crystals been built up? What
power has been at work arranging their delicate forms? In the fourth
lecture we shall see that up in the clouds another of our invisible
fairies, which, for want of a better name, we call the "force of
crystallization," has caught hold of the tiny particles of water before
"cohesion" had made them into round drops, and there silently but
rapidly, has moulded them into those delicate crystal stars known as
"snow-flakes."

And now, suppose that this snow-shower has fallen early in February;
turn aside for a moment from examining the flakes, and clear the
newly-fallen snow from off the flower-bed on the lawn. What is this
little green tip peeping up out of the ground under the snowy covering?
It is a young snowdrop plant. Can you tell me why it grows? where it
finds its food? what makes it spread out its leaves and add to its stalk
day by day? What fairies are at work here?

First there is the hidden fairy "life," and of her even our wisest men
know but little. But they know something of her way of working, and in
Lecture VII. we shall learn how the invisible fairy sunbeams have been
busy here also; how last year's snowdrop plant caught them and stored
them up in its bulb, and how now in the spring, as soon as warmth and
moisture creep down into the earth, these little imprisoned sun-waves
begin to be active, stirring up the matter in the bulb, and making it
swell and burst upwards till it sends out a little shoot through the
surface of the soil. Then the sun-waves above-ground take up the work,
and form green granules in the tiny leaves, helping them to take food
out of the air, while the little rootlets below are drinking water out
of the ground. The invisible life and invisible sunbeams are busy here,
setting actively to work another fairy, the force of "chemical
attraction," and so the little snowdrop plant grows and blossoms,
without any help from you or me.

One picture more, and then I hope you will believe in my fairies. From
the cold garden, you run into the house, and find the fire laid indeed
in the grate, but the wood dead and the coals black, waiting to be
lighted. You strike a match, and soon there is a blazing fire. Where
does the heat come from? Why do the coals burn and give out a glowing
light? Have you not read of gnomes buried down deep in the earth, in
mines, and held fast there till some fairy wand has released them, and
allowed them to come to earth again? Well, thousands and millions of
years ago, those coals were plants; and, like the snowdrop in the garden
of to-day, they caught the sunbeams and worked them into their leaves.
Then the plants died and were buried deep in the earth and the sunbeams
with them; and like the gnomes they lay imprisoned till the coals were
dug out by the miners, and brought to your grate; and just now you
yourself took hold of the fairy wand which was to release them. You
struck a match, and its atoms clashing with atoms of oxygen in the air,
set the invisible fairies "heat" and "chemical attraction" to work, and
they were soon busy within the wood and the coals causing their atoms
too to clash; and the sunbeams, so long imprisoned, leapt into flame.
Then you spread out your hands and cried, "Oh, how nice and warm!" and
little thought that you were warming yourself with the sunbeams of ages
and ages ago.

This is no fancy tale; it is literally true, as we shall see in Lecture
VIII., that the warmth of a coal fire could not exist if the plants of
long ago had not used the sunbeams to make their leaves, holding them
ready to give up their warmth again whenever those crushed leaves are
consumed.

       *       *       *       *       *

Now, do you believe in, and care for, my fairy-land? Can you see in your
imagination fairy _Cohesion_ ever ready to lock atoms together when they
draw very near to each other: or fairy _Gravitation_ dragging rain-drops
down to the earth: or the fairy of _Crystallization_ building up the
snow-flakes in the clouds? Can you picture tiny sunbeam-waves of light
and heat travelling from the sun to the earth? Do you care to know how
another strange fairy, _Electricity_, flings the lightning across the
sky and causes the rumbling thunder? Would you like to learn how the sun
makes pictures of the world on which he shines, so that we can carry
about with us photographs or sun-pictures of all the beautiful scenery
of the earth? And have you any curiosity about _Chemical action_, which
works such wonders in air, and land, and sea? If you have any wish to
know and make friends of these invisible forces, the next question is

How are you to enter the fairy-land of science?

There is but one way. Like the knight or peasant in the fairy tales, you
must open your eyes. There is no lack of objects, everything around you
will tell some history if touched with the fairy wand of imagination. I
have often thought, when seeing some sickly child drawn along the
street, lying on its back while other children romp and play, how much
happiness might be given to sick children at home or in hospitals, if
only they were told the stories which lie hidden in the things around
them. They need not even move from their beds, for sunbeams can fall on
them there, and in a sunbeam there are stories enough to occupy a month.
The fire in the grate, the lamp by the bedside, the water in the
tumbler, the fly on the ceiling above, the flower in the vase on the
table, anything, everything, has its history, and can reveal to us
nature's invisible fairies.

Only you must wish to see them. If you go through the world looking upon
everything only as so much to eat, to drink, and to use, you will never
see the fairies of science. But if you ask yourself why things happen,
and how the great God above us has made and governs this world of ours;
if you listen to the wind, and care to learn why it blows; if you ask
the little flower why it opens in the sunshine and closes in the storm;
and if when you find questions you cannot answer, you will take the
trouble to hunt out in books, or make experiments, to solve your own
questions, then you will learn to know and love those fairies.

Mind, I do not advise you to be constantly asking questions of other
people; for often a question quickly answered is quickly forgotten, but
a difficulty really hunted down is a triumph for ever. For example, if
you ask why the rain dries up from the ground, most likely you will be
answered, "that the sun dries it," and you will rest satisfied with the
sound of the words. But if you hold a wet handkerchief before the fire
and see the damp rising out of it, then you have some real idea how
moisture may be drawn up by heat from the earth.

A little foreign niece of mine, only four years old, who could scarcely
speak English plainly, was standing one morning near the bedroom window
and she noticed the damp trickling down the window-pane. "Auntie," she
said, "what for it rain inside?" It was quite useless to explain to her
in words, how our breath had condensed into drops of water upon the cold
glass; but I wiped the pane clear, and breathed on it several times.
When new drops were formed, I said, "Cissy and auntie have done like
this all night in the room." She nodded her little head and amused
herself for a long time breathing on the window-pane and watching the
tiny drops; and about a month later, when we were travelling back to
Italy, I saw her following the drops on the carriage window with her
little finger, and heard her say quietly to herself, "Cissy and auntie
made you." Had not even this little child some real picture in her mind
of invisible water coming from her mouth, and making drops upon the
window-pane?

       *       *       *       *       *

Then again, you must learn something of the language of science. If you
travel in a country with no knowledge of its language, you can learn
very little about it: and in the same way if you are to go to books to
find answers to your questions, you must know something of the language
they speak. You need not learn hard scientific names, for the best books
have the fewest of these, but you must really understand what is meant
by ordinary words.

For example, how few people can really explain the difference between a
_solid_, such as the wood of the table; a _liquid_, as water; and a
_gas_, such as I can let off from this gas-jet by turning the tap. And
yet any child can make a picture of this in his mind if only it has been
properly put before him.

All matter in the world is made up of minute parts or particles; in a
_solid_ these particles are locked together so tightly that you must
tear them forcibly apart if you wish to alter the shape of the solid
piece. If I break or bend this wood I have to force the particles to
move round each other, and I have great difficulty in doing it. But in a
_liquid_, though the particles are still held together, they do not
cling so tightly, but are able to roll or glide round each other, so
that when you pour water out of a cup on to a table, it loses its
cuplike shape and spreads itself out flat. Lastly, in a _gas_ the
particles are no longer held together at all, but they try to fly away
from each other; and unless you shut a gas in tightly and safely, it
will soon have spread all over the room.

A solid, therefore, will retain the same bulk and shape unless you
forcibly alter it; a liquid will retain the same bulk, but not the same
shape if it be left free; a gas will not retain either the same bulk or
the same shape, but will spread over as large a space as it can find
wherever it can penetrate. Such simple things as these you must learn
from books and by experiment.

Then you must understand what is meant by _chemical attraction_; and
though I can explain this roughly here, you will have to make many
interesting experiments before you will really learn to know this
wonderful fairy power. If I dissolve sugar in water, though it
disappears it still remains sugar, and does not join itself to the
water. I have only to let the cup stand till the water dries, and the
sugar will remain at the bottom. There has been no chemical attraction
here.

But now I will put something else in water which will call up the fairy
power. Here is a little piece of the metal potassium, one of the simple
substances of the earth; that is to say, we cannot split it up into
other substances, wherever we find it, it is always the same. Now if I
put this piece of potassium on the water it does not disappear quietly
like the sugar. See how it rolls round and round, fizzing violently,
with a blue flame burning round it, and at last goes off with a pop.

[Illustration: Fig. 1. Piece of potassium in a basin of water.]

What has been happening here?

You must first know that water is made of two substances, hydrogen and
oxygen, and these are not merely held together, but are joined so
completely that they have lost themselves and have become water; and
each atom of water is made of two atoms of hydrogen and one of oxygen.

Now the metal potassium is devotedly fond of oxygen, and the moment I
threw it on the water it called the fairy "chemical attraction" to help
it, and dragged the atoms of oxygen out of the water and joined them to
itself. In doing this it also caught part of the hydrogen, but only
half, and so the rest was left out in the cold. No, not in the cold! for
the potassium and oxygen made such a great heat in clashing together
that the rest of the hydrogen became very hot indeed, and sprang into
the air to find some other companion to make up for what it had lost.
Here it found some free oxygen in the air, and it seized upon it so
violently, that they made a burning flame, while the potassium with its
newly found oxygen and hydrogen sank down quietly into the water as
_potash_. And so you see we have got quite a new substance _potash_ in
the basin; made with a great deal of fuss by _chemical attraction_
drawing different atoms together.

When you can really picture this power to yourself it will help you very
much to understand what you read and observe about nature.

Next, as plants grow around you on every side, and are of so much
importance in the world, you must also learn something of the names of
the different parts of a flower, so that you may understand those books
which explain how a plant grows and lives and forms its seeds. You must
also know the common names of the parts of an animal, and of your own
body, so that you may be interested in understanding the use of the
different organs; how you breathe, and how your blood flows; how one
animal walks, another flies, and another swims. Then you must learn
something of the various parts of the world, so that you may know what
is meant by a river, a plain, a valley, or a delta. All these things are
not difficult, you can learn them pleasantly from simple books on
physics, chemistry, botany, physiology, and physical geography; and when
you understand a few plain scientific terms, then all by yourself, if
you will open your eyes and ears, you may wander, happily in the
fairy-land of science. Then wherever you go you will find

    "Tongues in trees, books in the running brooks,
    Sermons in stones, and good in everything."

And now we come to the last part of our subject. When you have reached
and entered the gates of science, how are you to use and enjoy this new
and beautiful land?

This is a very important question, for you may make a twofold use of it.
If you are only ambitious to shine in the world, you may use it chiefly
to get prizes, to be at the top of your class, or to pass in
examinations; but if you also enjoy discovering its secrets, and desire
to learn more and more of nature, and to revel in dreams of its beauty,
then you will study science for its own sake as well. Now it is a good
thing to win prizes and be at the top of your class, for it shows that
you are industrious; it is a good thing to pass well in examinations,
for it shows that you are accurate; but if you study science for this
reason _only_, do not complain if you find it dull, and dry, and hard to
master. You may learn a great deal that is useful, and nature will
answer you truthfully if you ask your questions accurately, but she will
give you dry facts, just such as you ask for. If you do not love her for
herself she will never take you to her heart.

This is the reason why so many complain that science is dry and
uninteresting. They forget that though it is necessary to learn
accurately, for so only we can arrive at truth, it is equally necessary
to love knowledge and make it lovely to those who learn, and to do this
we must get at the spirit which lies under the facts. What child which
loves its mother's face is content to know only that she has brown eyes,
a straight nose, a small mouth, and hair arranged in such and such a
manner? No, it knows that its mother has the sweetest smile of any woman
living; that her eyes are loving, her kiss is sweet, and that when she
looks grave, then something is wrong which must be put right. And it is
in this way that those who wish to enjoy the fairy-land of science must
love nature.

It is well to know that when a piece of potassium is thrown on water the
change which takes place is expressed by the formula K + H_{2}O = KHO +
H. But it is better still to have a mental picture of the tiny atoms
clasping each other, and mingling so as to make a new substance, and to
feel how wonderful are the many changing forms of nature. It is useful
to be able to classify a flower and to know that the buttercup belongs
to the Family Ranunculace, with _petals free and definite, stamens
hypogynous and indefinite, pistil apocarpous_. But it is far sweeter to
learn about the life of the little plant, to understand why its peculiar
flower is useful to it, and how it feeds itself, and makes its seed. No
one can love dry facts; we must clothe them with real meaning and love
the truths they tell, if we wish to enjoy science.

[Illustration: Fig. 2. Piece of white coral.]

Let us take an example to show this. I have here a branch of white
coral, a beautiful, delicate piece of nature's work. We will begin by
copying a description of it from one of those class-books which suppose
children to learn words like parrots, and to repeat them with just as
little understanding.

"Coral is formed by an animal belonging to the kingdom of _Radiates_,
sub-kingdom _Polypes_. The soft body of the animal is attached to a
support, the mouth opening upwards in a row of tentacles. The coral is
secreted in the body of the polyp out of the carbonate of lime in the
sea. Thus the coral animalcule rears its polypidom or rocky structure in
warm latitudes, and constructs reefs or barriers round islands. It is
limited in range of depth from 25 to 30 fathoms. Chemically considered,
coral is carbonate of lime; physiologically, it is the skeleton of an
animal; geographically it is characteristic of warm latitudes,
especially of the Pacific Ocean." This description is correct, and even
very fairly complete, if you know enough of the subject to understand
it. But tell me, does it lead you to love my piece of coral? Have you
any picture in your mind of the coral animal, its home, or its manner of
working?

But now, instead of trying to master this dry, hard passage, take Mr.
Huxley's penny lecture on 'Coral and Coral Reefs,'[2] and with the piece
of coral in your hand, try really to learn its history. You will then be
able to picture to yourself the coral animal as a kind of sea-anemone,
something like those which you have often seen, like red, blue, or green
flowers, putting out their feelers in sea-water on our coasts, and
drawing in the tiny sea-animals to digest them in that bag of fluid
which serves the sea-anemone as a stomach. You will learn how this
curious jelly animal can split itself in two, and so form two polyps, or
send a bud out of its side and so grow up into a kind of "tree or bush
of polyps," or how it can hatch little eggs inside it and throw out
young ones from its mouth, provided with little hairs, by means of which
they swim to new resting-places. You will learn the difference between
the animal which builds up the red coral as its skeleton, and the group
of animals which build up the white; and you will look with new interest
on our piece of white coral, as you read that each of those little cups
on its stem with delicate divisions like the spokes of a wheel has been
the home of a separate polyp, and that from the sea-water each little
jelly animal has drunk in carbonate of lime as you drink in sugar
dissolved in water, and then has used it grain by grain to build that
delicate cup and add to the coral tree.

We cannot stop to examine all about coral now, we are only learning how
to learn, but surely our specimen is already beginning to grow
interesting; and when you have followed it out into the great Pacific
Ocean, where the wild waves dash restlessly against the coral trees, and
have seen these tiny drops of jelly conquering the sea and building huge
walls of stone against the rough breakers, you will hardly rest till you
know all their history. Look at that curious circular island in the
picture (Fig. 3), covered with palm trees; it has a large smooth lake in
the middle, and the bottom of this lake is covered with blue, red, and
green jelly animals, spreading out their feelers in the water and
looking like beautiful flowers, and all round the outside of the island
similar animals are to be seen washed by the sea waves. Such islands as
this have been built entirely by the coral animals, and the history of
the way in which the reefs have sunk gradually down, as the tiny
creatures added to them inch by inch, is as fascinating as the story of
the building of any fairy palace in the days of old. Read all this, and
then if you have no coral of your own to examine, go to the British
Museum[3] and see the beautiful specimens in the glass cases there, and
think that they have been built up under the rolling surf by the tiny
jelly animals; and then coral will become a real living thing to you,
and you will love the thoughts it awakens.

[Illustration: Fig. 3. Coral island in the Pacific.]

But people often ask, what is the use of learning all this? If you do
not feel by this time how delightful it is to fill your mind with
beautiful pictures of nature, perhaps it would be useless to say more.
But in this age of ours, when restlessness and love of excitement
pervade so many lives, is it nothing to be taken out of ourselves and
made to look at the wonders of nature going on around us? Do you never
feel tired and "out of sorts," and want to creep away from your
companions, because they are merry and you are not? Then is the time to
read about the stars, and how quietly they keep their course from age to
age; or to visit some little flower, and ask what story it has to tell;
or to watch the clouds, and try to imagine how the winds drive them
across the sky. No person is so independent as he who can find interest
in a bare rock, a drop of water, the foam of the sea, the spider on the
wall, the flower underfoot or the stars overhead. And these interests
are open to everyone who enters the fairy-land of science.

Moreover, we learn from this study to see that there is a law and
purpose in everything in the Universe, and it makes us patient when we
recognize the quiet noiseless working of nature all around us. Study
light, and learn how all colour, beauty, and life depend on the sun's
rays; note the winds and currents of the air, regular even in their
apparent irregularity, as they carry heat and moisture all over the
world. Watch the water flowing in deep quiet streams, or forming the
vast ocean; and then reflect that every drop is guided by invisible
forces working according to fixed laws. See plants springing up under
the sunlight, learn the secrets of plant life, and how their scents and
colours attract the insects. Read how insects cannot live without
plants, nor plants without the flitting butterfly or the busy bee.
Realize that all this is worked by fixed laws, and that out of it (even
if sometimes in suffering and pain) springs the wonderful universe
around us. And then say, can you fear for your own little life, even
though it may have its troubles? Can you help feeling a part of this
guided and governed nature? or doubt that the power which fixed the laws
of the stars and of the tiniest drop of water--that made the plant draw
power from the sun, the tiny coral animal its food from the dashing
waves; that adapted the flower to the insect and the insect to the
flower--is also moulding your life as part of the great machinery of the
universe, so that you have only to work, and to wait, and to love?

We are all groping dimly for the Unseen Power, but no one who loves
nature and studies it can ever feel alone or unloved in the world.
Facts, as mere facts, are dry and barren, but nature is full of life and
love, and her calm unswerving rule is tending to some great though
hidden purpose. You may call this Unseen Power what you will--may lean
on it in loving, trusting faith, or bend in reverent and silent awe; but
even the little child who lives with nature and gazes on her with open
eye, must rise in some sense or other through nature to nature's God.

[Illustration]




LECTURE II.

SUNBEAMS AND THE WORK THEY DO.


[Illustration]

Who does not love the sunbeams, and feel brighter and merrier as he
watches them playing on the wall, sparkling like diamonds on the ripples
of the sea, or making bows of coloured light on the waterfall? Is not
the sunbeam so dear to us that it has become a household word for all
that is merry and gay? and when we want to describe the dearest,
busiest little sprite amongst us, who wakes a smile on all faces
wherever she goes, do we not call her the "sunbeam of the house"?

And yet how little even the wisest among us know about the nature and
work of these bright messengers of the sun as they dart across space!

Did you ever wake quite early in the morning, when it was pitch-dark and
you could see nothing, not even your own hand; and then lie watching as
time went on till the light came gradually creeping in at the window? If
you have done this you will have noticed that you can at first only just
distinguish the dim outline of the furniture; then you can tell the
difference between the white cloth on the table and the dark wardrobe
beside it; then by degrees all the smaller details, the handles of the
drawer, the pattern on the wall, and the different colours of all the
objects in the room become clearer and clearer till at last you see all
distinctly in broad daylight.

What has been happening here? and why have the things in the room become
visible by such slow degrees? We say that the sun is rising, but we know
very well that it is not the sun which moves, but that our earth has
been turning slowly round, and bringing the little spot on which we live
face to face with the great fiery ball, so that his beams can fall upon
us.

Take a small globe, and stick a piece of black plaster over England,
then let a lighted lamp represent the sun, and turn the globe slowly, so
that the spot creeps round from the dark side away from the lamp, until
it catches, first the rays which pass along the side of the globe, then
the more direct rays, and at last stands fully in the blaze of the
light. Just this was happening to our spot of the world as you lay in
bed and saw the light appear; and we have to learn to-day what those
beams are which fall upon us and what they do for us.

First we must learn something about the sun itself, since it is the
starting-place of all the sunbeams. If the sun were a dark mass instead
of a fiery one we should have none of these bright cheering messengers,
and though we were turned face to face with him every day we should
remain in one cold eternal night. Now you will remember we mentioned in
the last lecture that it is heat which shakes apart the little atoms of
water and makes them float up in the air to fall again as rain; and that
if the day is cold they fall as snow, and all the water is turned into
ice. But if the sun were altogether dark, think how bitterly cold it
would be; far colder than the most wintry weather ever known, because in
the bitterest night some warmth comes out of the earth, where it has
been stored from the sunlight which fell during the day. But if we never
received any warmth at all, no water would ever rise up into the sky, no
rain ever fall, no rivers flow, and consequently no plants could grow
and no animals live. All water would be in the form of snow and ice, and
the earth would be one great frozen mass with nothing moving upon it.

So you see it becomes very interesting for us to learn what the sun is,
and how he sends us his beams. How far away from us do you think he is?
On a fine summer's day when we can see him clearly, it looks as if we
had only to get into a balloon and reach him as he sits in the sky, and
yet we know roughly that he is more than ninety-one millions of miles
distant from our earth.

These figures are so enormous that you cannot really grasp them. But
imagine yourself in an express train, travelling at the tremendous rate
of sixty miles an hour and never stopping. At that rate, if you wished
to arrive at the sun to-day you would have been obliged to start 171
years ago. That is, you must have set off in the early part of the reign
of Queen Anne, and you must have gone on, never, never resting, through
the reigns of George I., George II., and the long reign of George III.,
then through those of George IV., William IV., and Victoria, whirling on
day and night at express speed, and at last, to-day, you would have
reached the sun!

And when you arrived there, how large do you think you would find him to
be? Anaxagoras, a learned Greek, was laughed at by all his fellow Greeks
because he said that the sun was as large as the Peloponnesus, that is
about the size of Middlesex. How astonished they would have been if they
could have known that not only is he bigger than the whole of Greece,
but more than a million times bigger than the whole world!

Our world itself is a very large place, so large that our own country
looks only like a tiny speck upon it, and an express train would take
nearly a month to travel round it. Yet even our whole globe is nothing
in size compared to the sun, for it only measures 8000 miles across,
while the sun measures more than 852,000.

[Illustration: Fig. 4. 106 earths laid across the face of the sun.
Each one of these dots represents roughly the size of the earth as
  compared to the size of the sun represented by the large circle.]

Imagine for a moment that you could cut the sun and the earth each in
half as you would cut an apple; then if you were to lay the flat side of
the half-earth on the flat side of the half-sun it would take 106 such
earths to stretch across the face of the sun. One of these 106 round
spots on the diagram represents the size which our earth would look if
placed on the sun; and they are so tiny compared to him that they look
only like a string of minute beads stretched across his face. Only
think, then, how many of these minute dots would be required to fill the
whole of the inside of Fig 4, if it were a globe!

One of the best ways to form an idea of the whole size of the sun is to
imagine it to be hollow, like an air-ball, and then see how many earths
it would take to fill it. You would hardly believe that it would take
one million, three hundred and thirty-one thousand globes the size of
our world squeezed together. Just think, if a huge giant could travel
all over the universe and gather worlds, all as big as ours, and were to
make first a heap of merely ten such worlds, how huge it would be! Then
he must have a hundred such heaps of ten to make a thousand worlds; and
then he must collect again a _thousand times that thousand to make a
million_, and when he had stuffed them all into the sun-ball he would
still have only filled three-quarters of it!

After hearing this you will not be astonished that such a monster should
give out an enormous quantity of light and heat; so enormous that it is
almost impossible to form any idea of it. Sir John Herschel has, indeed,
tried to picture it for us. He found that a ball of lime with a flame of
oxygen and hydrogen playing round it (such as we use in magic lanterns
and call oxy-hydrogen light) becomes so violently hot that it gives the
most brilliant artificial light we can get--such that you cannot put
your eye near it without injury. Yet if you wanted to have a light as
strong as that of our sun, it would not be enough to make such a
lime-ball as big as the sun is. No, you must make it as big as 146 suns,
or more than 146,000,000 times as big as our earth, in order to get the
right amount of light. Then you would have a tolerably good artificial
sun; for we know that the body of the sun gives out an intense white
light, just as the lime-ball does, and that, like it, it has an
atmosphere of glowing gases round it.

But perhaps we get the best idea of the mighty heat and light of the sun
by remembering how few of the rays which dart out on all sides from this
fiery ball can reach our tiny globe, and yet how powerful they are. Look
at the globe of a lamp in the middle of the room, and see how its light
pours out on all sides and into every corner; then take a grain of
mustard-seed, which will very well represent the comparative size of our
earth, and hold it up at a distance from the lamp. How very few of all
those rays which are filling the room fall on the little mustard-seed,
and just so few does our earth catch of the rays which dart out from the
sun. And yet this small quantity (1/2000-millionth part of the whole)
does nearly all the work of our world.[4]

In order to see how powerful the sun's rays are, you have only to take a
magnifying glass and gather them to a point on a piece of brown paper,
for they will set the paper alight. Sir John Herschel tells us that at
the Cape of Good Hope the heat was even so great that he cooked a
beefsteak and roasted some eggs by merely putting them in the sun, in a
box with a glass lid! Indeed, just as we should all be frozen to death
if the sun were cold, so we should all be burnt up with intolerable heat
if his fierce rays fell with all their might upon us. But we have an
invisible veil protecting us, made--of what do you think? Of those tiny
particles of water which the sunbeams draw up and scatter in the air,
and which, as we shall see in Lecture IV., cut off part of the intense
heat and make the air cool and pleasant for us.

       *       *       *       *       *

We have now learnt something of the distance, the size, the light, and
the heat of the sun--the great source of the sunbeams. But we are as yet
no nearer the answer to the question, What is a sunbeam? how does the
sun touch our earth?

Now suppose I wish to touch you from this platform where I stand, I can
do it in two ways. Firstly, I can throw something at you and hit you--in
this case a _thing_ will have passed across the space from me to you.
Or, secondly, if I could make a violent movement so as to shake the
floor of the room, you would feel a quivering motion; and so I should
touch you across the whole distance of the room. But in this case no
_thing_ would have passed from me to you but a movement or _wave_, which
passed along the boards of the floor. Again, if I speak to you, how does
the sound reach your ear? Not by anything being thrown from my mouth to
your ear, but by the motion of the air. When I speak I agitate the air
near my mouth, and that makes a wave in the air beyond, and that one,
another, and another (as we shall see more fully in Lecture VI.), till
the last wave hits the drum of your ear.

Thus we see there are two ways of touching anything at a distance; 1st,
by throwing some _thing_ at it and hitting it; 2nd, by sending a
movement or _wave_ across to it, as in the case of the quivering boards
and the air.

Now the great natural philosopher Newton thought that the sun touched us
in the first of these ways, and that sunbeams were made of very minute
atoms of matter thrown out by the sun, and making a perpetual cannonade
on our eyes. It is easy to understand that this would make us see light
and feel heat, just as a blow in the eye makes us see stars, or on the
body makes it feel hot: and for a long time this explanation was
supposed to be the true one. But we know now that there are many facts
which cannot be explained on this theory, though we cannot go into them
here. What we will do, is to try and understand what now seems to be the
true explanation of a sunbeam.

About the same time that Newton wrote, a Dutchman, named Huyghens,
suggested that light comes from the sun in tiny waves, travelling across
space much in the same way as ripples travel across a pond. The only
difficulty was to explain in what substance these waves could be
travelling: not through water, for we know that there is no water in
space--nor through air, for the air stops at a comparatively short
distance from our earth. There must then be something filling all space
between us and the sun, finer than either water or air.

And now I must ask you to use all your imagination, for I want you to
picture to yourselves something quite as invisible as the Emperor's new
clothes in Andersen's fairy-tale, only with this difference, that our
invisible _something_ is very active; and though we can neither see it
nor touch it we know it by its effects. You must imagine a fine
substance filling all space between us and the sun and the stars. A
substance so very delicate and subtle, that not only is it invisible,
but it can pass through solid bodies such as glass, ice, or even wood or
brick walls. This substance we call "ether." I cannot give you here the
reasons why we must assume that it is throughout all space; you must
take this on the word of such men as Sir John Herschel or Professor
Clerk-Maxwell, until you can study the question for yourselves.

Now if you can imagine this ether filling every corner of space, so that
it is everywhere and passes through everything, ask yourselves, what
must happen when a great commotion is going on in one of the large
bodies which float in it? When the atoms of the gases round the sun are
clashing violently together to make all its light and heat, do you not
think they must shake this ether all around them? And then since the
ether stretches on all sides from the sun to our earth and all other
planets, must not this quivering travel to us, just as the quivering of
the boards would from me to you? Take a basin of water to represent the
ether, and take a piece of potassium like that which we used in our last
lecture, and hold it with a pair of nippers in the middle of the water.
You will see that as the potassium hisses and the flame burns round it,
they will make waves which will travel all over the water to the edge of
the basin and you can imagine how in the same way waves travel over the
ether from the sun to us.

Straight away from the sun on all sides, never stopping, never resting,
but chasing after each other with marvellous quickness, these tiny waves
travel out into space by night and by day. When our spot of the earth
where England lies is turned away from them and they cannot touch us,
then it is night for us, but directly England is turned so as to face
the sun, then they strike on the land, and the water, and warm it; or
upon our eyes, making the nerves quiver so that we see light. Look up at
the sun and picture to yourself that instead of one great blow from a
fist causing you to see stars for a moment, millions of tiny blows from
these sun-waves are striking every instant on your eye; then you will
easily understand that this would cause you to see a constant blaze of
light.

But when the sun is away, if the night is clear we have light from the
stars. Do these then too make waves all across the enormous distance
between them and us? Certainly they do, for they too are suns like our
own, only they are so far off that the waves they send are more feeble,
and so we only notice them when the sun's stronger waves are away.

[Illustration: Fig. 5.
A, Hole in the shutter.
B, Wire placed in the beam of light.
S S, Screen on which the dark and light bands are caught.]

But perhaps you will ask, if no one has ever seen these waves nor the
ether in which they are made, what right have we to say they are there?
Strange as it may seem, though we cannot see them we have measured them
and know how large they are, and how many can go into an inch of space.
For as these tiny waves are running on straight forward through the
room, if we put something in their way, they will have to run round it;
and if you let in a very narrow ray of light through a shutter and put
an upright wire in the sunbeam, you actually make the waves run round
the wire just as water runs round a post in a river; and they meet
behind the wire, just as the water meets in a V shape behind the post.
Now when they meet, they run up against each other, and here it is we
catch them. For if they meet comfortably, both rising up in a good wave,
they run on together and make a bright line of light; but if they meet
higgledy-piggledy, one up and the other down, all in confusion, they
stop each other, and then there is no light, but a line of darkness. And
so behind your piece of wire you can catch the waves on a piece of
paper, and you will find they make dark and light lines one side by side
with the other, and by means of these bands it is possible to find out
how large the waves must be. This question is too difficult for us to
work it out here, but you can see that large waves will make broader
light and dark bands than small ones will, and that in this way the size
of the waves may be measured.

And now how large do you think they turn out to be? So very, very tiny
that about fifty thousand waves are contained in a single inch of space!
I have drawn on the board the length of an inch,[5] and now I will
measure the same space in the air between my finger and thumb. Within
this space at this moment there are fifty thousand tiny waves moving up
and down! I promised you we would find in science things as wonderful as
in fairy tales. Are not these tiny invisible messengers coming
incessantly from the sun as wonderful as any fairies? and still more so
when, as we shall see presently, they are doing nearly all the work of
our world.

We must next try to realize how fast these waves travel. You will
remember that an express train would take 171 years to reach us from the
sun; and even a cannon-ball would take from ten to thirteen years to
come that distance. Well, these tiny waves take only _seven minutes and
a half_ to come the whole 91 millions of miles. The waves which are
hitting your eye at this moment are caused by a movement which began at
the sun only 7-1/2 minutes ago. And remember, this movement is going on
incessantly, and these waves are always following one after the other so
rapidly that they keep up a perpetual cannonade upon the pupil of your
eye. So fast do they come that about 608 billion waves enter your eye in
one single second.[6] I do not ask you to remember these figures; I
only ask you to try and picture to yourselves these infinitely tiny and
active invisible messengers from the sun, and to acknowledge that light
is a fairy thing.

       *       *       *       *       *

[Illustration: Fig. 6.]

[Illustration: Fig. 7. Coloured spectrum thrown by a prism on the wall.
D E, Window-shutter.
F, Round hole in it.
A B C, Glass prism.
M N, Wall.]

But we do not yet know all about our sunbeam. See, I have here a piece
of glass with three sides, called a prism. If I put it in the sunlight
which is streaming through the window, what happens? Look! on the table
there is a line of beautiful colours. I can make it long or short, as I
turn the prism, but the colours always remain arranged in the same way.
Here at my left hand is the red, beyond it orange, then yellow, green,
blue, indigo or deep blue, and violet, shading one into the other all
along the line. We have all seen these colours dancing on the wall when
the sun has been shining brightly on the cut-glass pendants of the
chandelier, and you may see them still more distinctly if you let a ray
of light into a darkened room, and pass it through the prism as in the
diagram (Fig. 7). What are these colours? Do they come from the glass?
No; for you will remember to have seen them in the rainbow, and in the
soap-bubble, and even in a drop of dew or the scum on the top of a pond.
This beautiful coloured line is only our sunbeam again, which has been
split up into many colours by passing through the glass, as it is in the
rain-drops of the rainbow and the bubbles of the scum of the pond.

Till now we have talked of the sunbeam as if it were made of only one
set of waves, but in truth it is made of many sets of waves of different
sizes, all travelling along together from the sun. These various waves
have been measured, and we know that the waves which make up red light
are larger and more lazy than those which make violet light, so that
there are only thirty-nine thousand red waves in an inch, while there
are fifty-seven thousand violet waves in the same space.

How is it then, that if all these different waves, making different
colours, hit on our eye, they do not always make us see coloured light?
Because, unless they are interfered with, they all travel along
together, and you know that all colours, mixed together in proper
proportion, make white.

I have here a round piece of cardboard, painted with the seven colours
in succession several times over. When it is still you can distinguish
them all apart, but when I whirl it quickly round--see!--the cardboard
looks quite white, because we see them all so instantaneously that they
are mingled together. In the same way light looks white to you, because
all the different coloured waves strike on your eye at once. You can
easily make one of these cards for yourselves, only the white will
always look dirty, because you cannot get the colours pure.

[Illustration: Fig. 8.
A, Cardboard painted with the seven colours in
  succession.
B, Same cardboard spun quickly round.]

Now, when the light passes through the three-sided glass or prism, the
waves are spread out, and the slow, heavy, red waves lag behind and
remain at the lower end R of the coloured line on the wall (Fig. 7),
while the rapid little violet waves are bent more out of their road and
run to V at the farther end of the line; and the orange, yellow, green,
blue, and indigo arrange themselves between, according to the size of
their waves.

And now you are very likely eager to ask why the quick waves should make
us see one colour, and the slow waves another. This is a very difficult
question, for we have a great deal still to learn about the effect of
light on the eye. But you can easily imagine that colour is to our eye
much the same as music is to our ear. You know we can distinguish
different notes when the air-waves play slowly or quickly upon the drum
of the ear (as we shall see in Lecture VI.), and somewhat in the same
way the tiny waves of the ether play on the retina or curtain at the
back of our eye, and make the nerves carry different messages to the
brain: and the colour we see depends upon the number of waves which play
upon the retina in a second.

Do you think we have now rightly answered the question--What is a
sunbeam? We have seen that it is really a succession of tiny rapid
waves, travelling from the sun to us across the invisible substance we
call "ether," and keeping up a constant cannonade upon everything which
comes in their way. We have also seen that, tiny as these waves are,
they can still vary in size, so that one single sunbeam is made up of
myriads of different-sized waves, which travel all together and make us
see white light; unless for some reason they are scattered apart, so
that we see them separately as red, green, blue, or yellow. How they are
scattered, and many other secrets of the sun-waves, we cannot stop to
consider now, but must pass on to ask--

_What work do the sunbeams do for us?_

They do two things--they give us light and heat. It is by means of them
alone that we see anything. When the room was dark you could not
distinguish the table, the chairs, or even the walls of the room. Why?
Because they had no light-waves to send to your eye. But as the sunbeams
began to pour in at the window, the waves played upon the things in the
room, and when they hit them they bounded off them back to your eye, as
a wave of the sea bounds back from a rock and strikes against a passing
boat. Then, when they fell upon your eye, they entered it and excited
the retina, and the nerves, and the image of the chair or the table was
carried to your brain. Look around at all the things in this room. Is it
not strange to think that each one of them is sending these invisible
messengers straight to your eye as you look at it; and that you see me,
and distinguish me from the table, entirely by the kind of waves we each
send to you?

Some substances send back hardly any waves of light, but let them all
pass through them, and thus we cannot see them. A pane of clear glass,
for instance, lets nearly all the light-waves pass through it, and
therefore you often cannot see that the glass is there, because no
light-messengers come back to you from it. Thus people have sometimes
walked up against a glass door and broken it, not seeing it was there.
Those substances are transparent which, for some reason unknown to us,
allow the ether waves to pass through them without shaking the atoms of
which the substance is made. In clear glass, for example, all the
light-waves pass through without affecting the substance of the glass;
while in a white wall the larger part of the rays are reflected back to
your eye, and those which pass into the wall, by giving motion to its
atoms lose their own vibrations.

Into polished shining metal the waves hardly enter at all, but are
thrown back from the surface; and so a steel knife or a silver spoon are
very bright, and are clearly seen. Quicksilver is put at the back of
looking-glasses because it reflects so many waves. It not only sends
back those which come from the sun, but those, too, which come from your
face. So, when you see yourself in a looking-glass, the sun-waves have
first played on your face and bounded off from it to the looking-glass;
then, when they strike the looking-glass, they are thrown back again on
to the retina of your eye, and you see your own face by means of the
very waves you threw off from it an instant before.

But the reflected light-waves do more for us than this. They not only
make us see things, but they make us see them in different colours.
What, you will ask, is this too the work of the sunbeams? Certainly; for
if the colour we see depends on the size of the waves which come back to
us, then we must see things coloured differently according to the waves
they send back. For instance, imagine a sunbeam playing on a leaf: part
of its waves bound straight back from it to our eye and make us see the
surface of the leaf, but the rest go right into the leaf itself, and
there some of them are used up and kept prisoners. The red, orange,
yellow, blue, and violet waves are all useful to the leaf, and it does
not let them go again. But it cannot absorb the green waves, and so it
throws them back, and they travel to your eye and make you see a green
colour. So when you say a leaf is green, you mean that the leaf does not
want the green waves of the sunbeam, but sends them back to you. In the
same way the scarlet geranium rejects the red waves; this table sends
back brown waves; a white tablecloth sends back nearly the whole of the
waves, and a black coat scarcely any. This is why, when there is very
little light in the room, you can see a white tablecloth while you would
not be able to distinguish a black object, because the few faint rays
that are there, are all sent back to you from a white surface.

Is it not curious to think that there is really no such thing as colour
in the leaf, the table, the coat, or the geranium flower, but we see
them of different colours because, for some reason, they send back only
certain coloured waves to our eye?

Wherever you look, then, and whatever you see, all the beautiful tints,
colours, lights, and shades around you are the work of the tiny
sun-waves.

Again, light does a great deal of work when it falls upon plants. Those
rays of light which are caught by the leaf are by no means idle; we
shall see in Lecture VII. that the leaf uses them to digest its food and
make the sap on which the plant feeds.

We all know that a plant becomes pale and sickly if it has not sunlight,
and the reason is, that without these light-waves it cannot get food out
of the air, nor make the sap and juices which it needs. When you look at
plants and trees growing in the beautiful meadows; at the fields of
corn, and at the lovely landscape, you are looking on the work of the
tiny waves of light, which never rest all through the day in helping to
give life to every green thing that grows.

So far we have spoken only of light; but hold your hand in the sun and
feel the heat of the sunbeams, and then consider if the waves of heat do
not do work also. There are many waves in a sunbeam which move too
slowly to make us see light when they hit our eye, but we can feel them
as heat, though we cannot see them as light. The simplest way of feeling
heat-waves is to hold a warm iron near your face. You know that no light
comes from it, yet you can feel the heat-waves beating violently against
your face and scorching it. Now there are many of these dark heat-rays
in a sunbeam, and it is they which do most of the work in the world.

In the first place, as they come quivering to the earth, it is they
which shake the water-drops apart, so that these are carried up in the
air, as we shall see in the next lecture. And then remember, it is these
drops, falling again as rain, which make the rivers and all the moving
water on the earth. So also it is the heat-waves which make the air hot
and light, and so cause it to rise and make winds and air-currents, and
these again give rise to ocean-currents. It is these dark rays, again,
which strike upon the land and give it the warmth which enables plants
to grow. It is they also which keep up the warmth in our own bodies,
both by coming to us directly from the sun, and also in a very
roundabout way through plants. You will remember that plants use up rays
of light and heat in growing; then either we eat the plants, or animals
eat the plants and we eat the animals; and when we digest the food, that
heat comes back in our bodies, which the plants first took from the
sunbeam. Breathe upon your hand, and feel how hot your breath is; well,
that heat which you feel, was once in a sunbeam, and has travelled from
it through the food you have eaten, and has now been at work keeping up
the heat of your body.

But there is still another way in which these plants may give out the
heat-waves they have imprisoned. You will remember how we learnt in the
first lecture that coal is made of plants, and that the heat they give
out is the heat these plants once took in. Think how much work is done
by burning coals. Not only are our houses warmed by coal fires and
lighted by coal gas, but our steam-engines and machinery work entirely
by water which has been turned into steam by the heat of coal and coke
fires; and our steamboats travel all over the world by means of the same
power. In the same way the oil of our lamps comes either from olives,
which grow on trees; or from coal and the remains of plants and animals
in the earth. Even our tallow candles are made of mutton fat, and sheep
eat grass; and so, turn which way we will, we find that the light and
heat on our earth, whether they come from fires, or candles, or lamps,
or gas, and whether they move machinery, or drive a train, or propel a
ship, are equally the work of the invisible waves of ether coming from
the sun, which make what we call a sunbeam.

Lastly, there are still some hidden waves which we have not yet
mentioned, which are not useful to us either as light or heat, and yet
they are not idle.

Before I began this lecture, I put a piece of paper, which had been
dipped in nitrate of silver, under a piece of glass; and between it and
the glass I put a piece of lace. Look what the sun has been doing while
I have been speaking. It has been breaking up the nitrate of silver on
the paper and turning it into a deep brown substance; only where the
threads of the lace were, and the sun could not touch the nitrate of
silver, there the paper has remained light-coloured, and by this means I
have a beautiful impression of the lace on the paper. I will now dip the
impression into water in which some hyposulphite of soda is dissolved,
and this-will "fix" the picture, that is, prevent the sun acting upon it
any more; then the picture will remain distinct, and I can pass it round
to you all. Here, again, invisible waves have been at work, and this
time neither as light nor as heat, but as chemical agents, and it is
these waves which give us all our beautiful photographs. In any toyshop
you can buy this prepared paper, and set the chemical waves at work to
make pictures. Only you must remember to fix it in the solution
afterwards, otherwise the chemical rays will go on working after you
have taken the lace away, and all the paper will become brown and your
picture will disappear.

[Illustration: Fig. 9. Piece of lace photographed during the lecture.]

And now, tell me, may we not honestly say, that the invisible waves
which make our sunbeams, are wonderful fairy messengers as they travel
eternally and unceasingly across space, never resting, never tiring in
doing the work of our world? Little as we have been able to learn about
them in one short hour, do they not seem to you worth studying and worth
thinking about, as we look at the beautiful results of their work? The
ancient Greeks worshipped the sun, and condemned to death one of their
greatest philosophers, named Anaxagoras, because he denied that it was a
god. We can scarcely wonder at this when we see what the sun does for
our world; but _we_ know that it is a huge globe made of gases and fiery
matter, and not a god. We are grateful _for_ the sun instead of _to_
him, and surely we shall look at him with new interest, now that we can
picture his tiny messengers, the sunbeams, flitting over all space,
falling upon our earth, giving us light to see with, and beautiful
colours to enjoy, warming the air and the earth, making the refreshing
rain, and, in a word, filling the world with life and gladness.

[Illustration]




LECTURE III.

THE AERIAL OCEAN IN WHICH WE LIVE.


[Illustration]

Did you ever sit on the bank of a river in some quiet spot where the
water was deep and clear, and watch the fishes swimming lazily along?
When I was a child this was one of my favourite occupations in the
summer-time on the banks of the Thames, and there was one question
which often puzzled me greatly, as I watched the minnows and gudgeon
gliding along through the water. Why should fishes live _in_ something
and be often buffeted about by waves and currents, while I and others
lived on the _top_ of the earth and not _in_ anything? I do not remember
ever asking anyone about this; and if I had, in those days people did
not pay much attention to children's questions, and probably nobody
would have told me, what I now tell you, that we do live in something
quite as real and often quite as rough and stormy as the water in which
the fishes swim. The _something_ in which we live is air, and the reason
that we do not perceive it, is that we are in it, and that it is a gas
and invisible to us; while we are above the water in which the fishes
live, and it is a liquid which our eyes can perceive.

But let us suppose for a moment that a being, whose eyes were so made
that he could see gases as we see liquids, was looking down from a
distance upon our earth. He would see an ocean of air, or aerial ocean,
all round the globe, with birds floating about in it, and people walking
along the bottom, just as we see fish gliding along the bottom of a
river. It is true, he would never see even the birds come near to the
surface, for the highest-flying bird, the condor, never soars more than
five miles from the ground, and our atmosphere, as we shall see, is at
least 100 miles high. So he would call us all deep-air creatures, just
as we talk of deep-sea animals; and if we can imagine that he fished in
this air-ocean, and could pull one of us out of it into space, he would
find that we should gasp and die just as fishes do when pulled out of
the water.

He would also observe very curious things going on in our air-ocean; he
would see large streams and currents of air, which we call _winds_, and
which would appear to him as ocean-currents do to us, while near down to
the earth he would see thick mists forming and then disappearing again,
and these would be our clouds. From them he would see rain, hail and
snow falling to the earth, and from time to time bright flashes would
shoot across the air-ocean, which would be our lightning. Nay even the
brilliant rainbow, the northern aurora borealis, and the falling stars,
which seem to us so high up in space, would be seen by him near to our
earth, and all within the aerial ocean.

But as we know of no such being living in space, who can tell us what
takes place in our invisible air, and we cannot see it ourselves, we
must try by experiments to see it with our imagination, though we cannot
with our eyes.

First, then, can we discover what air is? At one time it was thought
that it was a simple gas and could not be separated into more than one
kind. But we are now going to make an experiment by which it has been
shown that air is made of two gases mingled together, and that one of
these gases, called _oxygen_, is used up when anything burns, while the
other _nitrogen_ is not used, and only serves to dilute the minute atoms
of oxygen. I have here a glass bell-jar, with a cork fixed tightly in
the neck, and I place the jar over a pan of water, while on the water
floats a plate with a small piece of phosphorus upon it. You will see
that by putting the bell-jar over the water, I have shut in a certain
quantity of air, and my object now is to use up the oxygen out of this
air and leave only nitrogen behind. To do this I must light the piece of
phosphorus, for you will remember it is in burning that oxygen is used
up. I will take the cork out, light the phosphorus, and cork up the jar
again. See! as the phosphorus burns white fumes fill the jar. These
fumes are phosphoric acid, which is a substance made of phosphorus and
oxygen. Our fairy force "chemical attraction" has been at work here,
joining the phosphorus and the oxygen of the air together.

[Illustration: Fig. 10. Phosphorus burning under a bell-jar (Roscoe).]

Now, phosphoric acid melts in water just as sugar does, and in a few
minutes these fumes will disappear. They are beginning to melt already,
and the water from the pan is rising up in the bell-jar. Why is this?
Consider for a moment what we have done. First, the jar was full of air,
that is, of mixed oxygen and nitrogen; then the phosphorus used up the
oxygen, making white fumes; afterwards, the water sucked up these fumes;
and so, in the jar now nitrogen is the only gas left, and the water has
risen up to fill all the rest of the space that was once taken up with
the oxygen.

We can easily prove that there is no oxygen now in the jar. I take out
the cork and let a lighted taper down into the gas. If there were any
oxygen the taper would burn, but you see it goes out directly, proving
that all the oxygen has been used up by the phosphorus. When this
experiment is made very accurately, we find that for every pint of
oxygen in air there are four pints of nitrogen, so that the active
oxygen-atoms are scattered about, floating in the sleepy, inactive
nitrogen.

It is these oxygen-atoms which we use up when we breathe. If I had put a
mouse under the bell-jar, instead of the phosphorus, the water would
have risen just the same, because the mouse would have breathed in the
oxygen and used it up in its body, joining it to carbon and making a bad
gas, carbonic acid, which would also melt in the water, and when all the
oxygen was used, the mouse would have died.

Do you see now how foolish it is to live in rooms that are closely shut
up, or to hide your head under the bedclothes when you sleep? You use up
all the oxygen-atoms, and then there are none left for you to breathe;
and besides this, you send out of your mouth bad fumes, though you
cannot see them, and these, when you breathe them in again, poison you
and make you ill.

Perhaps you will say, If oxygen is so useful, why is not the air made
entirely of it? But think for a moment. If there was such an immense
quantity of oxygen, how fearfully fast everything would burn! Our bodies
would soon rise above fever heat from the quantity of oxygen we should
take in, and all fires and lights would burn furiously. In fact, a
flame once lighted would spread so rapidly that no power on earth could
stop it, and everything would be destroyed. So the lazy nitrogen is very
useful in keeping the oxygen-atoms apart; and we have time, even when a
fire is very large and powerful, to put it out before it has drawn in
more and more oxygen from the surrounding air. Often, if you can shut a
fire into a closed space, as in a closely-shut room or the hold of a
ship, it will go out, because it has used up all the oxygen in the air.

So, you see, we shall be right in picturing this invisible air all
around us as a mixture of two gases. But when we examine ordinary air
very carefully, we find small quantities of other gases in it, besides
oxygen and nitrogen. First, there is carbonic acid gas. This is the bad
gas which we give out of our mouths after we have burnt up the oxygen
with the carbon of our bodies inside our lungs; and this carbonic acid
is also given out from everything that burns. If only animals lived in
the world, this gas would soon poison the air; but plants get hold of
it, and in the sunshine they break it up again, as we shall see in
Lecture VII., and use up the carbon, throwing the oxygen back into the
air for us to use. Secondly, there are very small quantities in the air
of _ammonia_, or the gas which almost chokes you in smelling-salts, and
which, when liquid, is commonly called "spirits of hartshorn." This
ammonia is useful to plants, as we shall see by and by. Lastly, there is
a great deal of water in the air, floating about as invisible vapour or
water-dust, and this we shall speak of in the next lecture. Still, all
these gases and vapours in the atmosphere are in very small quantities,
and the bulk of the air is composed of oxygen and nitrogen.

       *       *       *       *       *

Having now learned what air is, the next question which presents itself
is, Why does it stay round our earth? You will remember we saw in the
first lecture, that all the little atoms of a gas are trying to fly away
from each other, so that if I turn on this gas-jet the atoms soon leave
it, and reach you at the farther end of the room, and you can smell the
gas. Why, then, do not all the atoms of oxygen and nitrogen fly away
from our earth into space, and leave us without any air?

Ah! here you must look for another of our invisible forces. Have you
forgotten our giant force, "gravitation," which draws things together
from a distance? This force draws together the earth and the atoms of
oxygen and nitrogen; and as the earth is very big and heavy, and the
atoms of air are light and easily moved, they are drawn down to the
earth and held there by gravitation. But for all that, the atmosphere
does not leave off trying to fly away; it is always pressing upwards and
outwards with all its might, while the earth is doing its best to hold
it down.

The effect of this is, that near the earth, where the pull downward is
very strong, the air-atoms are drawn very closely together, because
gravitation gets the best in the struggle. But as we get farther and
farther from the earth, the pull downward becomes weaker, and then the
air-atoms spring farther apart, and the air becomes thinner. Suppose
that the lines in this diagram represent layers of air. Near the earth
we have to represent them as lying closely together, but as they recede
from the earth they are also farther apart.

[Illustration: Fig. 11.]

But the chief reason why the air is thicker or _denser_ nearer the
earth, is because the upper layers press it down. If you have a heap of
papers lying one on the top of the other, you know that those at the
bottom of the heap will be more closely pressed together than those
above, and just the same is the case with the atoms of the air. Only
there is this difference, if the papers have lain for some time, when
you take the top ones off, the under ones remain close together. But it
is not so with the air, because air is elastic, and the atoms are always
trying to fly apart, so that directly you take away the pressure they
spring up again as far as they can.

I have here an ordinary pop-gun. If I push the cork in very tight, and
then force the piston slowly inwards, I can compress the air a good
deal. Now I am forcing the atoms nearer and nearer together, but at
last they rebel so strongly against being more crowded that the cork
cannot resist their pressure. Out it flies, and the atoms spread
themselves out comfortably again in the air all around them. Now, just
as I pressed the air together in the pop-gun, so the atmosphere high up
above the earth presses on the air below and keeps the atoms closely
packed together. And in this case the atoms cannot force back the air
above them as they did the cork in the pop-gun; they are obliged to
submit to be pressed together.

Even a short distance from the earth, however, at the top of a high
mountain, the air becomes lighter, because it has less weight of
atmosphere above it, and people who go up in balloons often have great
difficulty in breathing, because the air is so thin and light. In 1804 a
Frenchman, named Gay-Lussac, went up four miles and a half in a balloon,
and brought down some air; and he found that it was much less heavy than
the same quantity of air taken close down to the earth, showing that it
was much thinner, or _rarer_, as it is called;[7] and when, in 1862, Mr.
Glaisher and Mr. Coxwell went up five miles and a half, Mr. Glaisher's
veins began to swell, and his head grew dizzy, and he fainted. The air
was too thin for him to breathe enough in at a time, and it did not
press heavily enough on the drums of his ears and the veins of his body.
He would have died if Mr. Coxwell had not quickly let off some of the
gas in the balloon, so that it sank down into denser air.

And now comes another very interesting question. If the air gets less
and less dense as it is farther from the earth, where does it stop
altogether? We cannot go up to find out, because we should die long
before we reached the limit; and for a long time we had to guess about
how high the atmosphere probably was, and it was generally supposed not
to be more than fifty miles. But lately, some curious bodies, which we
should have never suspected would be useful to us in this way, have let
us into the secret of the height of the atmosphere. These bodies are the
_meteors_, or _falling stars_.

Most people, at one time or another, have seen what looks like a star
shoot right across the sky, and disappear. On a clear starlight night
you may often see one or more of these bright lights flash through the
air; for one falls on an average in every twenty minutes, and on the
nights of August 9th and November 13th there are numbers in one part of
the sky. These bodies are not really stars; they are simply stones or
lumps of metal flying through the air, and taking fire by clashing
against the atoms of oxygen in it. There are great numbers of these
masses moving round and round the sun, and when our earth comes across
their path, as it does especially in August and November, they dash with
such tremendous force through the atmosphere that they grow white-hot,
and give out light, and then disappear, melted into vapour. Every now
and then one falls to the earth before it is all melted away, and thus
we learn that these stones contain tin, iron, sulphur, phosphorus, and
other substances.

It is while these bodies are burning that they look to us like falling
stars, and when we see them we know that they must be dashing against
our atmosphere. Now if two people stand a certain known distance, say
fifty miles, apart on the earth, and observe these meteors and the
direction in which they each see them fall, they can calculate (by means
of the angle between the two directions) how high they are above them
when they first see them, and at that moment they must have struck
against the atmosphere, and even travelled some way through it, to
become white-hot. In this way we have learnt that meteors burst into
light at least 100 miles above the surface of the earth, and so the
atmosphere must be more than 100 miles high.

       *       *       *       *       *

[Illustration: Fig. 12. A square inch of paper,
  as shown in the lecture.]

Our next question is as to the weight of our aerial ocean. You will
easily understand that all this air weighing down upon the earth must be
very heavy, even though it grows lighter as it ascends. The atmosphere
does, in fact, weigh down upon land at the level of the sea as much as
if a 15-pound weight were put upon every square inch of land. This
little piece of linen paper, which I am holding up, measures exactly a
square inch, and as it lies on the table, it is bearing a weight of 15
lbs. on its surface. But how, then, comes it that I can lift it so
easily? Why am I not conscious of the weight?

To understand this you must give all your attention for it is important
and at first not very easy to grasp. You must remember, in the first
place, that the air is heavy because it is attracted to the earth, and
in the second place, that since air is elastic all the atoms of it are
pushing upwards against this gravitation. And so, at any point in air,
as for instance the place where the paper now is as I hold it up, I feel
no pressure, because exactly as much as gravitation is pulling the air
down, so much elasticity is resisting and pushing it up. So the pressure
is equal upwards, downwards, and on all sides, and I can move the paper
with equal ease any way.

Even if I lay the paper on the table this is still true, because there
is always some air under it. If, however, I could get the air quite away
from one side of the paper, then the pressure on the other side would
show itself. I can do this by simply wetting the paper and letting it
fall on the table, and the water will prevent any air from getting under
it. Now see! if I try to lift it by the thread in the middle, I have
great difficulty, because the whole 15 pounds' weight of the atmosphere
is pressing it down. A still better way of making the experiment is with
a piece of leather, such as the boys often amuse themselves with in the
streets. This piece of leather has been well soaked. I drop it on the
floor, and see! it requires all my strength to pull it up.[8] I now
drop it on this stone weight, and so heavily is it pressed down upon it
by the atmosphere that I can lift the weight without its breaking away
from it.

[Illustration: Fig. 13. Soaked leather lifting a stone paperweight.]

Have you ever tried to pick limpets off a rock? If so, you know how
tight they cling. The limpet clings to the rock just in the same way as
this leather does to the stone; the little animal exhausts the air
inside its shell, and then it is pressed against the rock by the whole
weight of the air above.

Perhaps you will wonder how it is that if we have a weight of 15 lbs.
pressing on every square inch of our bodies, it does not crush us. And,
indeed, it amounts on the whole to a weight of about 15 tons upon the
body of a grown man. It would crush us if it were not that there are
gases and fluids inside our bodies which press outwards and balance the
weight so that we do not feel it at all.

This is why Mr. Glaisher's veins swelled and he grew giddy in thin air.
The gases and fluids inside his body were pressing outwards as much as
when he was below, but the air outside did not press so heavily, and so
all the natural condition of his body was disturbed.

I hope we now realize how heavily the air presses down upon our earth,
but it is equally necessary to understand how, being elastic, it also
presses upwards; and we can prove this by a simple experiment. I fill
this tumbler with water, and keeping a piece of card firmly pressed
against it, I turn the whole upside-down. When I now take my hand away
you would naturally expect the card to fall, and the water to be spilt.
But no! the card remains as if glued to the tumbler, kept there entirely
by the air pressing upwards against it.[9]

[Illustration: Fig. 14. Inverted tumbler of water with card kept against
  it by atmospheric pressure.]

And now we are almost prepared to understand how we can weigh the
invisible air. One more experiment first. I have here (Fig. 15, p. 64)
what is called a U tube, because it is shaped like a large U. I pour
some water in it till it is about half full, and you will notice that
the water stands at the same height in both arms of the tube (A, Fig.
15), because the air presses on both surfaces alike. Putting my thumb on
one end I tilt the tube carefully, so as to make the water run up to the
end of one arm, and then turn it back again (B, Fig. 15). But the water
does not now return to its even position, it remains up in the arm on
which my thumb rests. Why is this? Because my thumb keeps back the air
from pressing at that end, while the whole weight of the atmosphere
rests on the water at _c_. And so we learn that not only has the
atmosphere real weight but we can _see_ the effects of this weight by
making it balance a column of water or any other liquid. In the case of
the wetted leather we _felt_ the weight of the air, here we _see_ its
effects.

[Illustration: Fig. 15.
A, Water in a U tube under natural pressure of air.
B, Water kept in one arm of the tube by pressure of the air being at the
  open end only at _c_.]

Now when we wish to see the weight of the air we consult a _barometer_,
which works really just in the same way as the water in this tube. An
ordinary upright barometer is simply a straight tube of glass filled
with mercury or quicksilver, and turned upside-down in a small cup of
mercury (see B, Fig. 16). The tube is a little more than 30 inches long,
and though it is quite full of mercury before it is turned up (A), yet
directly it stands in the cup the mercury falls, till there is a height
of about 30 inches between the surface of the mercury in the cup C, and
that of the mercury in the tube B. As it falls it leaves an empty space
above the mercury at B which is called a _vacuum_, because it has no air
in it. Now, the mercury is under the same conditions as the water was in
the U tube, there is no pressure upon it at B, while there is a
pressure of 15 lbs. upon it in the bowl, and therefore it remains held
up in the tube.

[Illustration: Fig. 16. Tube of mercury inverted in a basin of mercury.]

But why will it not remain more than 30 inches high in the tube? You
must remember it is only kept up in the tube at all by the air which
presses on the mercury in the cup. And that column of mercury C B now
balances the pressure of the air outside, and presses down on the
mercury in the cup at its mouth just as much as the air does on the
rest. So this cup and tube act exactly like a pair of scales. The air
outside is the thing to be weighed at one end as it presses on the
mercury, the column C B answers to the leaden weight at the other end
which tells you how heavy the air is. Now if the bore of this tube is
made an inch square, then the 30 inches of mercury in it weigh exactly
15 lbs., and so we know that the weight of the air is 15 lbs. upon every
square inch, but if the bore of the tube is only half a square inch, and
therefore the 30 inches of mercury only weigh 7-1/2 lbs. instead of 15
lbs., the pressure of the atmosphere will also be halved, because it
will only act upon half a square inch of surface, and for this reason it
will make no difference to the height of the mercury whether the tube be
broad or narrow. Fig. 17 is a picture of the ordinary upright barometer;
the cup of mercury in which the tube stands is hidden inside the round
piece of wood A, and just at the bottom of this round is a small hole B,
through which the air gets to the cup.

[Illustration: Fig. 17. Ordinary upright barometer.
A, Wood covering cup of mercury.
B, Hole through which air acts.]

But now suppose the atmosphere grows lighter, as it does when it has
much damp in it. The barometer will show this at once, because there
will be less weight on the mercury in the cup, therefore it will not
keep the mercury pushed so high up in the tube. In other words, the
mercury in the tube will fall.

Let us suppose that one day the air is so much lighter that it presses
down only with a weight of 14-1/2 lbs. to the square inch instead of 15
lbs. Then the mercury would fall to 29 inches, because each inch is
equal to the weight of half a pound. Now, when the air is damp and very
full of water-vapour it is much lighter, and so when the barometer falls
we expect rain. Sometimes, however, other causes make the air light, and
then, although the barometer is low, no rain comes.

Again, if the air becomes heavier the mercury is pushed up above 30 to
31 inches, and in this way we are able to weigh the invisible air-ocean
all over the world, and tell when it grows lighter or heavier. This,
then, is the secret of the barometer. We cannot speak of the thermometer
to-day, but I should like to warn you in passing that it has nothing to
do with the weight of the air, but only with heat, and acts in quite a
different way.

       *       *       *       *       *

And now we have been so long hunting out, testing and weighing our
aerial ocean, that scarcely any time is left us to speak of its
movements or the pleasant breezes which it makes for us in our country
walks. Did you ever try to run races on a very windy day? Ah! then you
feel the air strongly enough; how it beats against your face and chest,
and blows down your throat so as to take your breath away; and what hard
work it is to struggle against it! Stop for a moment and rest, and ask
yourself, what is the wind? Why does it blow sometimes one way and
sometimes another, and sometimes not at all?

Wind is nothing more than air moving across the surface of the earth,
which as it passes along bends the tops of the trees, beats against the
houses, pushes the ships along by their sails, turns the windmill,
carries off the smoke from cities, whistles through the keyhole, and
moans as it rushes down the valley. What makes the air restless? why
should it not lie still all round the earth?

It is restless because, as you will remember, its atoms are kept pressed
together near the earth by the weight of the air above, and they take
every opportunity, when they can find more room, to spread out violently
and rush into the vacant space, and this rush we call a wind.

Imagine a great number of active schoolboys all crowded into a room till
they can scarcely move their arms and legs for the crush, and then
suppose all at once a large door is opened. Will they not all come
tumbling out pell-mell, one over the other, into the hall beyond, so
that if you stood in their way you would most likely be knocked down?
Well, just this happens to the air-atoms; when they find a space before
them into which they can rush, they come on helter-skelter, with such
force that you have great difficulty in standing against them, and catch
hold of something to support you for fear you should be blown down.

But how come they to find any empty space to receive them? To answer
this we must go back again to our little active invisible fairies the
sunbeams. When the sun-waves come pouring down upon the earth they pass
through the air almost without heating it. But not so with the ground;
there they pass down only a short distance and then are thrown back
again. And when these sun-waves come quivering back they force the atoms
of the air near the earth apart and make it lighter; so that the air
close to the surface of the heated ground becomes less heavy than the
air above it, and rises just as a cork rises in water. You know that hot
air rises in the chimney; for if you put a piece of lighted paper on the
fire it is carried up by the draught of air, often even before it can
ignite. Now just as the hot air rises from the fire, so it rises from
the heated ground up into higher parts of the atmosphere. And as it
rises it leaves only thin air behind it, and this cannot resist the
strong cold air whose atoms are struggling and trying to get free, and
they rush in and fill the space.

One of the simplest examples of wind is to be found at the seaside.
There in the daytime the land gets hot under the sunshine, and heats the
air, making it grow light and rise. Meanwhile the sunshine on the water
goes down deeper and so does not send back so many heat-waves into the
air; consequently the air on the top of the water is cooler and heavier,
and it rushes in from over the sea to fill up the space on the shore
left by the warm air as it rises. This is why the seaside is so pleasant
in hot weather. During the daytime a light _sea-breeze_ nearly always
sets in from the sea to the land.

When night comes, however, then the land loses its heat very quickly,
because it has not stored it up and the land-air grows cold; but the
sea, which has been hoarding the sun-waves down in its depths, now gives
them up to the atmosphere above it, and the sea-air becomes warm and
rises. For this reason it is now the turn of the cold air from the land
to spread over the sea, and you have a _land-breeze_ blowing off the
shore.

Again, the reason why there are such steady winds, called the _trade
winds_, blowing towards the equator, is that the sun is very hot at the
equator, and hot air is always rising there and making room for colder
air to rush in. We have not time to travel farther with the moving air,
though its journeys are extremely interesting; but if, when you read
about the trade and other winds, you will always picture to yourselves
warm air made light by heat rising up into space and cold air expanding
and rushing in to fill its place, I can promise you that you will not
find the study of aerial currents so dry as many people imagine it to
be.

       *       *       *       *       *

We are now able to form some picture of our aerial ocean. We can imagine
the active atoms of oxygen floating in the sluggish nitrogen, and being
used up in every candle-flame, gas-jet and fire, and in the breath of
all living beings; and coming out again tied fast to atoms of carbon and
making carbonic acid. Then we can turn to trees and plants, and see them
tearing these two apart again, holding the carbon fast and sending the
invisible atoms of oxygen bounding back again into the air, ready to
recommence work. We can picture all these air-atoms, whether of oxygen
or nitrogen, packed close together on the surface of the earth, and
lying gradually further and further apart, as they have less weight
above them, till they become so scattered that we can only detect them
as they rub against the flying meteors which flash into light. We can
feel this great weight of air pressing the limpet on to the rock; and we
can see it pressing up the mercury in the barometer and so enabling us
to measure its weight. Lastly, every breath of wind that blows past us
tells us how this aerial ocean is always moving to and fro on the face
of the earth; and if we think for a moment how much bad air and bad
matter it must carry away, as it goes from crowded cities to be
purified in the country, we can see how, in even this one way alone, it
is a great blessing to us.

Yet even now we have not mentioned many of the beauties of our
atmosphere. It is the tiny particles floating in the air which scatter
the light of the sun so that it spreads over the whole country and into
shady places. The sun's rays always travel straight forward; and in the
moon, where there is no atmosphere, there is no light anywhere except
just where the rays fall. But around our earth the sun-waves hit against
the myriads of particles in the air and glide off them into the corners
of the room or the recesses of a shady lane, and so we have light spread
before us wherever we walk in the daytime, instead of those deep black
shadows which we can see through a telescope on the face of the moon.

Again, it is electricity playing in the air-atoms which gives us the
beautiful lightning and the grand aurora borealis, and even the
twinkling of the stars is produced entirely by minute changes in the
air. If it were not for our aerial ocean the stars would stare at us
sternly, instead of smiling with the pleasant twinkle-twinkle which we
have all learned to love as little children.

All these questions, however, we must leave for the present; only I hope
you will be eager to read about them wherever you can, and open your
eyes to learn their secrets. For the present we must be content if we
can even picture this wonderful ocean of gas spread round our earth, and
some of the work it does for us.

We said in the last lecture that without the sunbeams the earth would
be cold, dark, and frost-ridden. With sunbeams, but without air, it
would indeed have burning heat, side by side with darkness and ice, but
it could have no soft light. Our planet might look beautiful to others,
as the moon does to us, but it could have comparatively few beauties of
its own. With the sunbeams and the air, we see it has much to make it
beautiful. But a third worker is wanted before our planet can revel in
activity and life. This worker is water; and in the next lecture we
shall learn something of the beauty and the usefulness of the "drops of
water" on their travels.

[Illustration]




LECTURE IV.

A DROP OF WATER ON ITS TRAVELS.

[Illustration]


We are going to spend an hour to-day in following a drop of water on its
travels. If I dip my finger in this basin of water and lift it up again,
I bring with it a small glistening drop out of the body of water below,
and hold it before you. Tell me, have you any idea where this drop has
been? what changes it has undergone, and what work it has been doing
during all the long ages that water has lain on the face of the earth?
It is a drop now, but it was not so before I lifted it out of the basin;
then it was part of a sheet of water, and will be so again if I let it
fall. Again, if I were to put this basin on the stove till all the water
had boiled away, where would my drop be then? Where would it go? What
forms will it take before it reappears in the rain-cloud, the river, or
the sparkling dew?

These are questions we are going to try to answer to-day; and first,
before we can in the least understand how water travels, we must call to
mind what we have learnt about the sunbeams and the air. We must have
clearly pictured in our imagination those countless sun-waves which are
for ever crossing space, and especially those larger and slower
undulations, the dark heat-waves; for it is these, you will remember,
which force the air-atoms apart and make the air light, and it is also
these which are most busy in sending water on its travels. But not these
alone. The sun-waves might shake the water-drops as much as they liked,
and turn them into invisible vapour, but they could not carry them over
the earth if it were not for the winds and currents of that aerial ocean
which bears the vapour on its bosom, and wafts it to different regions
of the world.

Let us try to understand how these two invisible workers, the sun-waves
and the air, deal with the drops of water. I have here a kettle (Fig.
18, p. 76) boiling over a spirit-lamp, and I want you to follow minutely
what is going on in it. First, in the flame of the lamp, atoms of the
spirit drawn up from below are clashing with the oxygen-atoms in the
air. This, as you know, causes heat-waves and light-waves to move
rapidly all round the lamp. The light-waves cannot pass through the
kettle, but the heat-waves can, and as they enter the water inside they
agitate it violently. Quickly, and still more quickly, the particles of
water near the bottom of the kettle move to and fro and are shaken
apart; and as they become light they rise through the colder water,
letting another layer come down to be heated in its turn. The motion
grows more and more violent, making the water hotter and hotter, till at
last the particles of which it is composed fly asunder, and escape as
invisible vapour. If this kettle were transparent you would not _see_
any steam above the water, because it is in the form of an invisible
gas. But as the steam comes out of the mouth of the kettle you see a
cloud. Why is this? Because the vapour is chilled by coming out into the
cold air, and its particles are drawn together again into tiny, tiny
drops of water, to which Dr. Tyndall has given the suggestive name of
_water-dust_. If you hold a plate over the steam you can catch these
tiny drops, though they will run into one another almost as you are
catching them.

The clouds you see floating in the sky are made of exactly the same kind
of water-dust as the cloud from the kettle, and I wish to show you that
this is also really the same as the invisible steam within the kettle.
I will do so by an experiment suggested by Dr. Tyndall. Here is another
spirit-lamp, which I will hold under the cloud of steam--see! the cloud
disappears! As soon as the water-dust is heated the heat-waves scatter
it again into invisible particles, which float away into the room. Even
without the spirit-lamp, you can convince yourself that water-vapour may
be invisible; for close to the mouth of the kettle you will see a short
blank space before the cloud begins. In this space there must be steam,
but it is still so hot that you cannot see it; and this proves that
heat-waves can so shake water apart as to carry it away invisibly right
before your eyes.

[Illustration: Fig. 18.]

Now, although we never see any water travelling from our earth up into
the skies, we know that it goes there, for it comes down again in rain,
and so it must go up invisibly. But where does the heat come from which
makes this water invisible? Not from below, as in the case of the
kettle, but from above, pouring down from the sun. Wherever the
sun-waves touch the rivers, ponds, lakes, seas, or fields of ice and
snow upon our earth, they carry off invisible water-vapour. They dart
down through the top layers of the water, and shake the water-particles
forcibly apart; and in this case the drops fly asunder more easily and
before they are so hot, because they are not kept down by a great weight
of water above, as in the kettle, but find plenty of room to spread
themselves out in the gaps between the air-atoms of the atmosphere.

Can you imagine these water-particles, just above any pond or lake,
rising up and getting entangled among the air-atoms? They are very
light, much lighter than the atmosphere; and so, when a great many of
them are spread about in the air which lies just over the pond, they
make it much lighter than the layer of air above, and so help it to
rise, while the heavier layer of air comes down ready to take up more
vapour.

In this way the sun-waves and the air carry off water every day, and all
day long, from the top of lakes, rivers, pools, springs, and seas, and
even from the surface of ice and snow. Without any fuss or noise or sign
of any kind, the water of our earth is being drawn up invisibly into the
sky.

It has been calculated that in the Indian Ocean three-quarters of an
inch of water is carried off from the surface of the sea in one day and
night; so that as much as 22 feet, or a depth of water about twice the
height of an ordinary room, is silently and invisibly lifted up from the
whole surface of the ocean in one year. It is true this is one of the
hottest parts of the earth, where the sun-waves are most active; but
even in our own country many feet of water are drawn up in the
summer-time.

What, then, becomes of all this water? Let us follow it as it struggles
upwards to the sky. We see it in our imagination first carrying layer
after layer of air up with it from the sea till it rises far above our
heads and above the highest mountains. But now, call to mind what
happens to the air as it recedes from the earth. Do you not remember
that the air-atoms are always trying to fly apart, and are only kept
pressed together by the weight of air above them? Well, as this
water-laden air rises up, its particles, no longer so much pressed
together, begin to separate, and in so doing they use up part of the
heat which they carried up from the earth, and thus the air becomes
colder. Then you know at once what must happen to the invisible
vapour,--it will form into tiny water-drops, like the steam from the
kettle. And so, as the air rises and becomes colder, the vapour gathers
into visible masses, and we can see it hanging in the sky, and call it
_clouds_. When these clouds are highest they are about ten miles from
the earth, but when they are made of heavy drops and hang low down, they
sometimes come within a mile of the ground.

Look up at the clouds as you go home, and think that the water of which
they are made has all been drawn up invisibly through the air. Not,
however, necessarily here in London, for we have already seen that air
travels as wind all over the world, rushing in to fill spaces made by
rising air wherever they occur, and so these clouds may be made of
vapour collected in the Mediterranean, or in the Gulf of Mexico off the
coast of America, or even, if the wind is from the north, of chilly
particles gathered from the surface of Greenland ice and snow, and
brought here by the moving currents of air. Only, of one thing we may be
sure, that they come from the water of our earth.

[Illustration: Fig. 19. Clouds formed by ascending vapour as it enters
  cold spaces in the atmosphere.]

Sometimes, if the air is warm, these water-particles may travel a long
way without ever forming into clouds; and on a hot, cloudless day the
air is often very full of invisible vapour. Then, if a cold wind comes
sweeping along, high up in the sky, and chills this vapour, it forms
into great bodies of water-dust clouds, and the sky is overcast. At
other times clouds hang lazily in a bright sky, and these show us that
just where they are (as in Fig. 19) the air is cold and turns the
invisible vapour rising from the ground into visible water-dust, so that
exactly in those spaces we see it as clouds. Such clouds form often on a
warm, still summer's day, and they are shaped like masses of wool,
ending in a straight line below. They are not merely hanging in the sky,
they are really resting upon a tall column of invisible vapour which
stretches right up from the earth; and that straight line under the
clouds marks the place where the air becomes cold enough to turn this
invisible vapour into visible drops of water.

And now, suppose that while these or any other kind of clouds are
overhead, there comes along either a very cold wind, or a wind full of
vapour. As it passes through the clouds, it makes them very full of
water, for, if it chills them, it makes the water-dust draw more closely
together; or, if it brings a new load of water-dust, the air is fuller
than it can hold. In either case a number of water-particles are set
free, and our fairy force "cohesion" seizes upon them at once and forms
them into large water-drops. Then they are much heavier than the air,
and so they can float no longer, but down they come to the earth in a
shower of rain.

There are other ways in which the air may be chilled, and rain made to
fall, as, for example, when a wind laden with moisture strikes against
the cold tops of mountains. Thus the Khasia Hills in India, which face
the Bay of Bengal, chill the air which crosses them on its way from the
Indian Ocean. The wet winds are driven up the sides of the hills, the
air expands, and the vapour is chilled, and forming into drops, falls in
torrents of rain. Sir J. Hooker tells us that as much as 500 inches of
rain fell in these hills in nine months. That is to say, if you could
measure off all the ground over which the rain fell, and spread the
whole nine months' rain over it, it would make a lake 500 inches, or
more than 40 feet deep! You will not be surprised that the country on
the other side of these hills gets hardly any rain, for all the water
has been taken out of the air before it comes there. Again for example
in England, the wind comes to Cumberland and Westmoreland over the
Atlantic, full of vapour, and as it strikes against the Pennine Hills it
shakes off its watery load; so that the lake district is the most rainy
in England, with the exception perhaps of Wales, where the high
mountains have the same effect.

       *       *       *       *       *

In this way, from different causes, the water of which the sun has
robbed our rivers and seas, comes back to us, after it has travelled to
various parts of the world, floating on the bosom of the air. But it
does not always fall straight back into the rivers and seas again, a
large part of it falls on the land, and has to trickle down slopes and
into the earth, in order to get back to its natural home, and it is
often caught on its way before it can reach the great waters.

Go to any piece of ground which is left wild and untouched, you will
find it covered with grass, weeds, and other plants; if you dig up a
small plot you will find innumerable tiny roots creeping through the
ground in every direction. Each of these roots has a sponge-like mouth
by which the plant takes up water. Now, imagine rain-drops falling on
this plot of ground and sinking into the earth. On every side they will
find rootlets thirsting to drink them in, and they will be sucked up as
if by tiny sponges, and drawn into the plants, and up the stems to the
leaves. Here, as we shall see in Lecture VII., they are worked up into
food for the plant, and only if the leaf has more water than it needs,
some drops may escape at the tiny openings under the leaf, and be drawn
up again by the sun-waves as invisible vapour into the air.

Again, much of the rain falls on hard rock and stone, where it cannot
sink in, and then it lies in pools till it is shaken apart again into
vapour and carried off in the air. Nor is it idle here, even before it
is carried up to make clouds. We have to thank this invisible vapour in
the air for protecting us from the burning heat of the sun by day and
intolerable frost by night.

Let us for a moment imagine that we can see all that we know exists
between us and the sun. First, we have the fine _ether_ across which the
sunbeams travel, beating down upon our earth with immense force, so that
in the sandy desert they are like a burning fire. Then we have the
coarser _atmosphere_ of oxygen and nitrogen atoms hanging in this ether,
and bending the minute sun-waves out of their direct path. But they do
very little to hinder them on their way, and this is why in very dry
countries the sun's heat is so intense. The rays beat down mercilessly,
and nothing opposes them. Lastly, in damp countries we have the larger
but still invisible particles of vapour hanging about among the
air-atoms. Now, these watery particles, although they are very few (only
about one twenty-fifth part of the whole atmosphere), _do hinder_ the
sun-waves. For they are very greedy of heat, and though the light-waves
pass easily through them, they catch the heat-waves and use them to help
themselves to expand. And so, when there is invisible vapour in the air,
the sunbeams come to us deprived of some of their heat-waves, and we
can remain in the sunshine without suffering from the heat.

This is how the water-vapour shields us by day, but by night it is still
more useful. During the day our earth and the air near it have been
storing up the heat which has been poured down on them, and at night,
when the sun goes down, all this heat begins to escape again. Now, if
there were no vapour in the air, this heat would rush back into space so
rapidly that the ground would become cold and frozen even on a summer's
night, and all but the most hardy plants would die. But the vapour which
formed a veil against the sun in the day, now forms a still more
powerful veil against the escape of the heat by night. It shuts in the
heat-waves, and only allows them to make their way slowly upwards from
the earth--thus producing for us the soft, balmy nights of summer and
preventing all life being destroyed in the winter.

Perhaps you would scarcely imagine at first that it is this screen of
vapour which determines whether or not we shall have dew upon the
ground. Have you ever thought why dew forms, or what power has been at
work scattering the sparkling drops upon the grass? Picture to yourself
that it has been a very hot summer's day, and the ground and the grass
have been well warmed, and that the sun goes down in a clear sky without
any clouds. At once the heat-waves which have been stored up in the
ground, bound back into the air, and here some are greedily absorbed by
the vapour, while others make their way slowly upwards. The grass,
especially, gives out these heat-waves very quickly, because the blades,
being very thin, are almost all surface. In consequence of this they
part with their heat more quickly than they can draw it up from the
ground, and become cold. Now, the air lying just above the grass is full
of invisible vapour, and the cold of the blades, as it touches them,
chills the water-particles, and they are no longer able to hold apart,
but are drawn together into drops on the surface of the leaves.

We can easily make artificial dew for ourselves. I have here a bottle of
ice which has been kept outside the window. When I bring it into the
warm room a mist forms rapidly outside the bottle. This mist is composed
of water-drops, drawn out of the air of the room, because the cold glass
chilled the air all round it, so that it gave up its invisible water to
form dew-drops. Just in this same way the cold blades of grass chill the
air lying above them, and steal its vapour.

But try the experiment, some night when a heavy dew is expected, of
spreading a thin piece of muslin over some part of the grass, supporting
it at the four corners with pieces of stick so that it forms an awning.
Though there may be plenty of dew on the grass all round, yet under this
awning you will find scarcely any. The reason of this is that the muslin
checks the heat-waves as they rise from the grass, and so the
grass-blades are not chilled enough to draw together the water-drops on
their surface. If you walk out early in the summer mornings and look at
the fine cobwebs flung across the hedges, you will see plenty of drops
on the cobwebs themselves sparkling like diamonds; but underneath on the
leaves there will be none, for even the delicate cobweb has been strong
enough to shut in the heat-waves and keep the leaves warm.

Again, if you walk off the grass on to the gravel path, you find no dew
there. Why is this? Because the stones of the gravel can draw up heat
from the earth below as fast as they give it out, and so they are never
cold enough to chill the air which touches them. On a cloudy night also
you will often find little or no dew even on the grass. The reason of
this is that the clouds give back heat to the earth, and so the grass
does not become chilled enough to draw the water-drops together on its
surface. But after a hot, dry day, when the plants are thirsty and there
is little hope of rain to refresh them, then they are able in the
evening to draw the little drops from the air and drink them in before
the rising sun comes again to carry them away.

       *       *       *       *       *

But our rain-drop undergoes other changes more strange than these. Till
now we have been imagining it to travel only where the temperature is
moderate enough for it to remain in a liquid state as water. But suppose
that when it is drawn up into the air it meets with such a cold blast as
to bring it to the freezing point. If it falls into this blast when it
is already a drop, then it will freeze into a hailstone, and often on a
hot summer's day we may have a severe hailstorm, because the rain-drops
have crossed a bitterly cold wind as they were falling, and have been
frozen into round drops of ice.

But if the water-vapour reaches the freezing air while it is still an
invisible gas, and before it has been drawn into a drop, then its
history is very different. The ordinary force of cohesion has then no
power over the particles to make them into watery globes, but its place
is taken by the fairy process of "crystallization," and they are formed
into beautiful white flakes, to fall in a snow-shower. I want you to
picture this process to yourselves, for if once you can take an interest
in the wonderful power of nature to build up crystals, you will be
astonished how often you will meet with instances of it, and what
pleasure it will add to your life.

[Illustration: Fig. 20. A piece of sugar-candy, photographed of
  the natural size.]

The particles of nearly all substances, when left free and not hurried, can
build themselves into crystal forms. If you melt salt in water and then let
all the water evaporate slowly, you will get salt-crystals;--beautiful
cubes of transparent salt all built on the same pattern. The same is true
of sugar; and if you will look at the spikes of an ordinary stick of
sugar-candy, such as I have here, you will see the kind of crystals which
sugar forms. You may even pick out such shapes as these from the common
crystallized brown sugar in the sugar basin, or see them with a magnifying
glass on a lump of white sugar.

But it is not only easily melted substances such as sugar and salt which
form crystals. The beautiful stalactite grottos are all made of crystals
of lime. Diamonds are crystals of carbon, made inside the earth.
Rock-crystals, which you know probably under the name of Irish diamonds,
are crystallized quartz; and so, with slightly different colourings, are
agates, opals, jasper, onyx, cairngorms, and many other precious stones.
Iron, copper, gold, and sulphur, when melted and cooled slowly build
themselves into crystals, each of their own peculiar form, and we see
that there is here a wonderful order, such as we should never have
dreamt of, if we had not proved it. If you possess a microscope you may
watch the growth of crystals yourself by melting some common powdered
nitre in a little water till you find that no more will melt in it. Then
put a few drops of this water on a warm glass slide and place it under
the microscope. As the drops dry you will see the long transparent
needles of nitre forming on the glass, and notice how regularly these
crystals grow, not by taking food inside like living beings, but by
adding particle to particle on the outside evenly and regularly.

Can we form any idea why the crystals build themselves up so
systematically? Dr. Tyndall says we can, and I hope by the help of these
small bar magnets to show you how he explains it. These little pieces of
steel, which I hope you can see lying on this white cardboard, have
been rubbed along a magnet until they have become magnets themselves,
and I can attract and lift up a needle with any one of them. But if I
try to lift one bar with another, I can only do it by bringing certain
ends together. I have tied a piece of red cotton (_c_, Fig. 21) round
one end of each of the magnets, and if I bring two red ends together
they will not cling together but roll apart.

[Illustration: Fig. 21. Bar magnets attracting and repelling each other.
_c_, Cotton tied round the north pole of the magnet.]

If, on the contrary, I put a red end against an end where there is no
cotton, then the two bars cling together. This is because every magnet
has two poles or points which are exactly opposite in character. One of
these is called the north pole of the magnet, because, if the rod hangs
freely, that end will point to the north, and the other is the south
pole, pointing to the south. Now, when I bring two red ends, that is,
two north poles together, they drive each other away. See! the magnet I
am not holding runs away from the other. The same will happen if I bring
two south poles together. But if I bring a red end and a black end,
that is, a north pole and a south pole together, then they are attracted
and cling. I will make a triangle (A, Fig. 21) in which a black end and
a red end always come together, and you see the triangle holds together.
But now if I take off the lower bar and turn it (B, Fig. 21) so that two
red ends and two black ends come together, then this bar actually rolls
back from the others down the cardboard. If I were to break these bars
into a thousand pieces, each piece would still have two poles, and if
they were scattered about near each other in such a way that they were
quite free to move, they would arrange themselves always so that two
different poles came together.

Now picture to yourselves that all the particles of those substances
which form crystals have poles like our magnets, then you can imagine
that when the heat which held them apart is withdrawn and the particles
come very near together, they will arrange themselves according to the
attraction of their poles and so build up regular and beautiful
patterns.

So, if we could travel up to the clouds where this fairy power of
crystallization is at work, we should find the particles of water-vapour
in a freezing atmosphere being built up into minute solid crystals of
snow. If you go out after a snow-shower and search carefully, you will
see that the snow-flakes are not mere lumps of frozen water, but
beautiful six-pointed crystal stars, so white and pure that when we want
to speak of anything being spotlessly white, you say that it is "white
as snow." Some of these crystals are simply flat slabs with six sides,
others are stars with six rods or spikes springing from the centre,
others with six spikes each formed like a delicate fern. No less than a
thousand different forms of delicate crystals have been found among
snow-flakes, but though there is such a great variety, yet they are all
built on the six-sided and six-pointed plan, and are all rendered
dazzlingly white by the reflection of the light from the faces of the
crystals and the tiny air-bubbles built up within them. This, you see,
is why, when the snow melts, you have only a little dirty water in your
hand; the crystals are gone and there are no more air-bubbles held
prisoners to act as looking-glasses to the light. Hoar-frost is also
made up of tiny water-crystals, and is nothing more than frozen dew
hanging on the blades of grass and from the trees.

[Illustration: Fig. 22. Snow-crystals.]

But how about ice? Here, you will say, is frozen water, and yet we see
no crystals, only a clear transparent mass. Here, again, Dr. Tyndall
helps us. He says (and as I have proved it true, so may you for
yourselves, if you will) that if you take a magnifying glass, and look
down on the surface of ice on a sunny day, you will see a number of
dark, six-sided stars, looking like flattened flowers, and in the centre
of each a bright spot. These flowers, which are seen when the ice is
melting, are our old friends the crystal stars turning into water, and
the bright spot in the middle is a bubble of empty space, left because
the watery flower does not fill up as much room as the ice of the
crystal star did.

[Illustration: Fig. 23. Water-flowers in melting ice.--Tyndall.]

And this leads us to notice that ice always takes up more room than
water, and that this is the reason why our water-pipes burst in severe
frosts; for as the water freezes it expands with great force, and the
pipe is cracked, and then when the thaw comes on, and the water melts
again, it pours through the crack the ice has made.

It is not difficult to understand why ice should take more room; for we
know that if we were to try to arrange bricks end to end in star-like
shapes, we must leave some spaces between, and could not pack them so
closely as if they lay side by side. And so, when this giant force of
crystallization constrains the atoms of frozen water to grow into
star-like forms, the solid mass must fill more room than the liquid
water, and when the star melts, this space reveals itself to us in the
bright spot of the centre.

       *       *       *       *       *

We have now seen our drop of water under all its various forms of
invisible gas, visible steam, cloud, dew, hoar-frost, snow, and ice, and
we have only time shortly to see it on its travels, not merely up and
down, as hitherto, but round the world.

We must first go to the sea as the _distillery_, or the place from which
water is drawn up invisibly, in its purest state, into the air; and we
must go chiefly to the seas of the tropics, because here the sun shines
most directly all the year round, sending heat-waves to shake the
water-particles asunder. It has been found by experiment that, in order
to turn 1 lb. of water into vapour, as much heat must be used as is
required to melt 5 lbs. of iron; and if you consider for a moment how
difficult iron is to melt, and how we can keep an iron poker in a hot
fire and yet it remains solid, this will help you to realize how much
heat the sun must pour down in order to carry off such a constant supply
of vapour from the tropical seas.

Now, when all this vapour is drawn up into the air, we know that some of
it will form into clouds as it gets chilled high up in the sky, and then
it will pour down again in those tremendous floods of rain which occur
in the tropics.

But the sun and air will not let it all fall down at once, and the winds
which are blowing from the equator to the poles carry large masses of it
away with them. Then, as you know, it will depend on many things how
far this vapour is carried. Some of it, chilled by cold blasts, or by
striking on cold mountain tops, as it travels northwards, will fall in
rain in Europe and Asia, while that which travels southwards may fall in
South America, Australia, or New Zealand, or be carried over the sea to
the South Pole. Wherever it falls on the land as rain, and is not used
by plants, it will do one of two things; either it will run down in
streams and form brooks and rivers, and so at last find its way back to
the sea, or it will sink deep in the earth till it comes upon some hard
rock through which it cannot get, and then, being hard pressed by the
water coming on behind, it will rise up again through cracks, and come
to the surface as a spring. These springs, again, feed rivers, sometimes
above-ground, sometimes for long distances underground; but one way or
another at last the whole drains back into the sea.

But if the vapour travels on till it reaches high mountains in cooler
lands, such as the Alps of Switzerland; or is carried to the poles and
to such countries as Greenland or the Antarctic Continent, then it will
come down as snow, forming immense snow-fields. And here a curious
change takes place in it. If you make an ordinary snowball and work it
firmly together, it becomes very hard, and if you then press it forcibly
into a mould you can turn it into transparent ice. And in the same way
the snow which falls in Greenland and on the high mountains of
Switzerland becomes very firmly pressed together, as it slides down into
the valleys. It is like a crowd of people passing from a broad
thoroughfare into a narrow street. As the valley grows narrower and
narrower the great mass of snow in front cannot move down quickly, while
more and more is piled up by the snowfall behind, and the crowd and
crush grow denser and denser. In this way the snow is pressed together
till the air that was hidden in its crystals, and which gave it its
beautiful whiteness, is all pressed out, and the snow-crystals
themselves are squeezed into one solid mass of pure, transparent ice.

Then we have what is called a "glacier," or river of ice, and this solid
river comes creeping down till, in Greenland, it reaches the edge of the
sea. There it is pushed over the brink of the land, and large pieces
snap off, and we have "icebergs." These icebergs--made, remember, of the
same water which was first drawn up from the tropics--float on the wide
sea, and melting in its warm currents, topple over and over[10] till
they disappear and mix with the water, to be carried back again to the
warm ocean from which they first started. In Switzerland the glaciers
cannot reach the sea, but they move down into the valleys till they come
to a warmer region, and there the end of the glacier melts, and flows
away in a stream. The Rhone and many other rivers are fed by the
glaciers of the Alps; and as these rivers flow into the sea, our drop of
water again finds its way back to its home.

But when it joins itself in this way to its companions, from whom it was
parted for a time, does it come back clear and transparent as it left
them? From the iceberg it does indeed return pure and clear; for the
fairy Crystallization will have no impurities, not even salt, in her
ice-crystals, and so as they melt they give back nothing but pure water
to the sea. Yet even icebergs bring down earth and stones frozen into
the bottom of the ice, and so they feed the sea with mud.

But the drops of water in rivers are by no means as pure as when they
rose up into the sky. We shall see in the next lecture how rivers carry
down not only sand and mud all along their course, but even solid matter
such as salt, lime, iron, and flint, dissolved in the clear water, just
as sugar is dissolved, without our being able to see it. The water, too,
which has sunk down into the earth, takes up much matter as it travels
along. You all know that the water you drink from a spring is very
different from rain-water, and you will often find a hard crust at the
bottom of kettles and in boilers, which is formed of the carbonate of
lime which is driven out of the clear water when it is boiled. The water
has become "hard" in consequence of having picked up and dissolved the
carbonate of lime on its way through the earth, just in the same way as
water would become sweet if you poured it through a sugar-cask. You will
also have heard of iron-springs, sulphur-springs, and salt-springs,
which come out of the earth, even if you have never tasted any of them,
and the water of all these springs finds its way back at last to the
sea.

And now, can you understand why sea-water should taste salt and bitter?
Every drop of water which flows from the earth to the sea carries
something with it. Generally, there is so little of any substance in the
water that we cannot taste it, and we call it pure water; but the purest
of spring or river-water has always some solid matter dissolved in it,
and all this goes to the sea. Now, when the sun-waves come to take the
water out of the sea again, they will have nothing but the pure water
itself; and so all these salts and carbonates and other solid substances
are left behind, and we taste them in sea-water.

Some day, when you are at the seaside, take some sea-water and set it on
the hob till a great deal has simmered gently away, and the liquid is
very thick. Then take a drop of this liquid, and examine it under a
microscope. As it dries up gradually, you will see a number of crystals
forming, some square--and these will be crystals of ordinary salt; some
oblong--these will be crystals of gypsum or alabaster; and others of
various shapes. Then, when you see how much matter from the land is
contained in sea-water, you will no longer wonder that the sea is salt;
on the contrary, you will ask, Why does it not grow salter every year?

The answer to this scarcely belongs to our history of a drop of water,
but I must just suggest it to you. In the sea are numbers of soft-bodied
animals, like the jelly animals which form the coral, which require hard
material for their shells or the solid branches on which they live, and
they are greedily watching for these atoms of lime, of flint, of
magnesia, and of other substances brought down into the sea. It is with
lime and magnesia that the tiny chalk-builders form their beautiful
shells, and the coral animals their skeletons, while another class of
builders use the flint; and when these creatures die, their remains go
to form fresh land at the bottom of the sea; and so, though the earth is
being washed away by the rivers and springs it is being built up again,
out of the same materials, in the depths of the great ocean.

And now we have reached the end of the travels of our drop of water. We
have seen it drawn up by the fairy "heat," invisible into the sky; there
fairy "cohesion" seized it, and formed it into water-drops, and the
giant, "gravitation," pulled it down again to the earth. Or, if it rose
to freezing regions, the fairy of "crystallization" built it up into
snow-crystals, again to fall to the earth, and either to be melted back
into water by heat, or to slide down the valleys by force of
gravitation, till it became squeezed into ice. We have detected it, when
invisible, forming a veil round our earth, and keeping off the intense
heat of the sun's rays by day, or shutting it in by night. We have seen
it chilled by the blades of grass, forming sparkling dew-drops or
crystals of hoar-frost, glistening in the early morning sun; and we have
seen it in the dark underground, being drunk up greedily by the roots of
plants. We have started with it from the tropics, and travelled over
land and sea, watching it forming rivers, or flowing underground in
springs, or moving onwards to the high mountains or the poles, and
coming back again in glaciers and icebergs. Through all this, while it
is being carried hither and thither by invisible power, we find no trace
of its becoming worn out, or likely to rest from its labours. Ever
onwards it goes, up and down, and round and round the world, taking many
forms, and performing many wonderful feats. We have seen some of the
work that it does, in refreshing the air, feeding the plants, giving us
clear, sparkling water to drink, and carrying matter to the sea; but
besides this, it does a wonderful work in altering all the face of our
earth. This work we shall consider in the next lecture, on "The two
great Sculptors--Water and Ice."

[Illustration]




LECTURE V.

THE TWO GREAT SCULPTORS--WATER AND ICE.


[Illustration]

In our last lecture we saw that water can exist in three forms:--1st, as
an invisible vapour; 2nd, as liquid water; 3rd, as solid snow and ice.

To-day we are going to take the two last of these forms, water and ice,
and speak of them as sculptors.

To understand why they deserve this name we must first consider what the
work of a sculptor is. If you go into a statuary yard you will find
there large blocks of granite, marble, and other kinds of stone, hewn
roughly into different shapes; but if you pass into the studio, where
the sculptor himself is at work, you will find beautiful statues, more
or less finished; and you will see that out of rough blocks of stone he
has been able to cut images which look like living forms. You can even
see by their faces whether they are intended to be sad, or thoughtful,
or gay, and by their attitude whether they are writhing in pain, or
dancing with joy, or resting peacefully. How has all this history been
worked out from the shapeless stone? It has been done by the sculptor's
chisel. A piece chipped off here, a wrinkle cut there, a smooth surface
rounded off in another place, so as to give a gentle curve; all these
touches gradually shape the figure and mould it out of the rough stone,
first into a rude shape and afterwards, by delicate strokes, into the
form of a living being.

Now, just in the same way as the wrinkles and curves of a statue are cut
by the sculptor's chisel, so the hills and valleys, the steep slopes and
gentle curves on the face of our earth, giving it all its beauty, and
the varied landscapes we love so well, have been cut out by water and
ice passing over them. It is true that some of the greater wrinkles of
the earth, the lofty mountains, and the high masses of land which rise
above the sea, have been caused by earthquakes and shrinking of the
earth. We shall not speak of these to-day, but put them aside as
belonging to the rough work of the statuary yard. But when once these
large masses are put ready for water to work upon, then all the rest of
the rugged wrinkles and gentle slopes which make the country so
beautiful are due to water and ice; and for this reason I have called
them "sculptors."

Go for a walk in the country, or notice the landscape as you travel on a
railway journey. You pass by hills and through valleys, through narrow
steep gorges cut in hard rock, or through wild ravines up the sides of
which you can hardly scramble. Then you come to grassy slopes and to
smooth plains across which you can look for miles without seeing a hill;
or, when you arrive at the seashore, you clamber into caves and grottos,
and along dark narrow passages leading from one bay to another. All
these--hills, valleys, gorges, ravines, slopes, plains, caves, grottos,
and rocky shores--have been cut out by water. Day by day and year by
year, while everything seems to us to remain the same, this industrious
sculptor is chipping away, a few grains here, a corner there, a large
mass in another place, till he gives to the country its own peculiar
scenery, just as the human sculptor gives expression to his statue.

Our work to-day will consist in trying to form some idea of the way in
which water thus carves out the surface of the earth, and we will begin
by seeing how much can be done by our old friends the rain-drops before
they become running streams.

Everyone must have noticed that whenever rain falls on soft ground it
makes small round holes in which it collects, and then sinks into the
ground forcing its way between the grains of earth. But you would hardly
think that the beautiful pillars in Fig. 24 have been made entirely in
this way by rain beating upon and soaking into the ground.

[Illustration: Fig. 24. Earth-pillars near Botzen, in the Tyrol.
  (Adapted from Lyell's 'Principles.')]

Where these pillars stand there was once a solid mass of clay and
stones, into which the rain-drops crept, loosening the earthy particles;
and then when the sun dried the earth again, cracks were formed so that
the next shower loosened it still more, and carried some of the mud down
into the valley below. But here and there large stones were buried in
the clay, and where this happened the rain could not penetrate, and the
stones became the tops of tall pillars of clay, washed into shape by the
rain beating on its sides, but escaping the general destruction of the
rest of the mud. In this way the whole valley has been carved out into
fine pillars, some still having capping-stones, while others have lost
them, and these last will soon be washed away. We have no such valleys
of earth-pillars here in England, but you may sometimes see tiny pillars
under bridges where the drippings have washed away the earth between the
pebbles, and such small examples which you can observe for yourselves
are quite as instructive as more important ones.

Another way in which rain changes the surface of the earth is by sinking
down through loose soil from the top of a cliff to a depth of many feet
till it comes to solid rock, and then lying spread over a wide space.
Here it makes a kind of watery mud, which is a very unsafe foundation
for the hill of earth above it, and so after a time the whole mass slips
down and makes a fresh piece of land at the foot of the cliff. If you
have ever been at the Isle of Wight you will have seen an undulating
strip of ground, called the Undercliff, at Ventnor and other places,
stretching all along the sea below the high cliffs. This land was once
at the top of the cliff, and came down by a succession of landslips such
as we have been describing. A very great landslip of this kind happened
in the memory of living people, at Lyme Regis, in Dorsetshire, in the
year 1839.

       *       *       *       *       *

You will easily see how in forming earth-pillars and causing landslips
rain changes the face of the country, but these are only rare effects
of water. It is when the rain collects in brooks and forms rivers that
it is most busy in sculpturing the land. Look out some day into the road
or the garden where the ground slopes a little, and watch what happens
during a shower of rain. First the rain-drops run together in every
little hollow of the ground, then the water begins to flow along any
ruts or channels it can find, lying here and there in pools, but always
making its way gradually down the slope. Meanwhile from other parts of
the ground little rills are coming, and these all meet in some larger
ruts where the ground is lowest, making one great stream, which at last
empties itself into the gutter or an area, or finds its way down some
grating.

Now just this, which we can watch whenever a heavy shower of rain comes
down on the road, happens also all over the world. Up in the mountains,
where there is always a great deal of rain, little rills gather and fall
over the mountain sides, meeting in some stream below. Then, as this
stream flows on, it is fed by many runnels of water, which come from all
parts of the country, trickling along ruts, and flowing in small brooks
and rivulets down the gentle slope of the land till they reach the big
stream, which at last is important enough to be called a river.
Sometimes this river comes to a large hollow in the land and there the
water gathers and forms a lake; but still at the lower end of this lake
out it comes again, forming a new river, and growing and growing by
receiving fresh streams until at last it reaches the sea.

The River Thames, which you all know, and whose course you will find
clearly described in Mr. Huxley's 'Physiography,' drains in this way no
less than one-seventh of the whole of England. All the rain which falls
in Berkshire, Oxfordshire, Middlesex, Hertfordshire, Surrey, the north
of Wiltshire and north-west of Kent, the south of Buckinghamshire and of
Gloucestershire, finds its way into the Thames; making an area of 6160
square miles over which every little rivulet and brook trickle down to
the one great river, which bears them to the ocean. And so with every
other area of land in the world there is some one channel towards which
the ground on all sides slopes gently down, and into this channel all
the water will run, on its way to the sea.

But what has this to do with sculpture or cutting out of valleys? If you
will only take a glass of water out of any river, and let it stand for
some hours, you will soon answer this question for yourself. For you
will find that even from river water which looks quite clear, a thin
layer of mud will fall to the bottom of the glass, and if you take the
water when the river is swollen and muddy you will get quite a thick
deposit. This shows that the brooks, the streams, and the rivers wash
away the land as they flow over it and carry it from the mountains down
to the valleys, and from the valleys away out into the sea.

But besides earthy matter, which we can see, there is much matter
dissolved in the water of rivers (as we mentioned in the last lecture),
and this we cannot see.

If you use water which comes out of a chalk country you will find that
after a time the kettle in which you have been in the habit of boiling
this water has a hard crust on its bottom and sides, and this crust is
made of chalk or carbonate of lime, which the water took out of the
rocks when it was passing through them. Professor Bischoff has
calculated that the river Rhine carries past Bonn every year enough
carbonate of lime dissolved in its water to make 332,000 million
oyster-shells, and that if all these shells were built into a cube it
would measure 560 feet every way.

Imagine to yourselves the whole of St. Paul's churchyard filled with
oyster-shells, built up in a large square till they reached half as high
again as the top of the cathedral, then you will have some idea of the
amount of chalk carried invisibly past Bonn in the water of the Rhine
every year.

Since all this matter, whether brought down as mud or dissolved, comes
from one part of the land to be carried elsewhere or out to sea, it is
clear that some gaps and hollows must be left in the places from which
it is taken. Let us see how these gaps are made. Have you ever clambered
up the mountain-side, or even up one of those small ravines in the
hill-side, which have generally a little stream trickling through them?
If so, you must have noticed the number of pebbles, large and small,
lying in patches here and there in the stream, and many pieces of broken
rock, which are often scattered along the sides of the ravine; and how,
as you climb, the path grows steeper, and the rocks become rugged and
stick out in strange shapes.

[Illustration: Fig. 25. Ravine worn by water in the side of a hill.]

The history of this ravine will tell us a great deal about the carving
of water. Once it was nothing more than a little furrow in the hill-side
down which the rain found its way in a thin thread-like stream. But by
and by, as the stream carried down some of the earth, and the furrow
grew deeper and wider, the sides began to crumble when the sun dried up
the rain which had soaked in. Then in winter, when the sides of the hill
were moist with the autumn rains, frost came and turned the water to
ice, and so made the cracks still larger, and the swollen stream rushing
down, caught the loose pieces of rock and washed them down into its bed.
Here they were rolled over and over, and grated against each other, and
were ground away till they became rounded pebbles, such as lie in the
foreground of the picture (Fig. 25); while the grit which was rubbed
off them was carried farther down by the stream. And so in time this
became a little valley, and as the stream cut it deeper and deeper,
there was room to clamber along the sides of it, and ferns and mosses
began to cover the naked stone, and small trees rooted themselves along
the banks, and this beautiful little nook sprang up on the hill-side
entirely by the sculpturing of water.

Shall you not feel a fresh interest in all the little valleys, ravines,
and gorges you meet with in the country, if you can picture them being
formed in this way year by year? There are many curious differences in
them which you can study for yourselves. Some will be smooth, broad
valleys, and here the rocks have been soft and easily worn, and water
trickling down the sides of the first valley has cut other channels so
as to make smaller valleys running across it. In other places there will
be narrow ravines, and here the rocks have been hard, so that they did
not wear away gradually, but broke off and fell in blocks, leaving high
cliffs on each side. In some places you will come to a beautiful
waterfall, where the water has tumbled over a steep cliff, and then
eaten its way back, just like a saw cutting through a piece of wood.

There are two things in particular to notice in a waterfall like this.
First, how the water and spray dash against the bottom of the cliff down
which it falls, and grind the small pebbles against the rock. In this
way the bottom of the cliff is undermined, and so great pieces tumble
down from time to time, and keep the fall upright instead of its being
sloped away at the top, and becoming a mere stream. Secondly, you may
often see curious cup-shaped holes, called "pot-holes," in the rocks on
the sides of a waterfall, and these also are concerned in its formation.
In these holes you will generally find two or three small pebbles, and
you have here a beautiful example of how water uses stones to grind away
the face of the earth. These holes are made entirely by the falling
water eddying round and round in a small hollow of the rock, and
grinding the pebbles which it has brought down, against the bottom and
sides of this hollow, just as you grind round a pestle in a mortar. By
degrees the hole grows deeper and deeper, and though the first pebbles
are probably ground down to powder, others fall in, and so in time there
is a great hole perforated right through, helping to make the rock break
and fall away.

In this and other ways the water works its way back in a surprising
manner. The Isle of Wight gives us some good instances of this; Alum Bay
Chine and the celebrated Blackgang Chine have been entirely cut out by
waterfalls. But the best known and most remarkable example is the
Niagara Falls, in America. Here, the River Niagara first wanders through
a flat country, and then reaches the great Lake Erie in a hollow of the
plain. After that, it flows gently down for about fifteen miles, and
then the slope becomes greater and it rushes on to the Falls of Niagara.
These falls are not nearly so high as many people imagine, being only
165 feet, or about half the height of St. Paul's Cathedral, but they are
2700 feet or nearly half-a-mile wide, and no less than 670,000 tons of
water fall over them every minute, making magnificent clouds of spray.

[Illustration: Fig. 26. Bird's-eye view of Lake Erie, Niagara Falls,
  and Queenstown. (Lyell.)]

Sir Charles Lyell, when he was at Niagara, came to the conclusion that,
taking one year with another, these falls eat back the cliff at the rate
of about one foot a year, as you can easily imagine they would do, when
you think with what force the water must dash against the bottom of the
falls. In this way a deep cleft has been cut right back from Queenstown
for a distance of seven miles, to the place where the falls now are.
This helps us a little to understand how very slowly and gradually
water cuts its way; for if a foot a year is about the average of the
waste of the rock, it will have taken more than thirty-five thousand
years for that channel of seven miles to be made.

[Illustration: Fig. 27.--GREAT CAON, COLORADO RIVER.
  (From Lieut. Ives' Report.)]

But even this chasm cut by the falls of Niagara is nothing compared with
the caons of Colorado. Caon is a Spanish word for a rocky gorge, and
these gorges are indeed so grand, that if we had not seen in other
places what water can do, we should never have been able to believe that
it could have cut out these gigantic chasms. For more than three hundred
miles the River Colorado, coming down from the Rocky Mountains, has
eaten its way through a country made of granite and hard beds of
limestone and sandstone, and it has cut down straight through these
rocks, leaving walls from half-a-mile to a mile high, standing straight
up from it. The cliffs of the Great Caon, as it is called, stretch up
for more than a mile above the river which flows in the gorge below!
Fancy yourselves for a moment in a boat on this river, as shown in
Figure 27, and looking up at these gigantic walls of rock towering above
you. Even half-way up them, a man, if he could get there, would be so
small you could not see him without a telescope; while the opening at
the top between the two walls would seem so narrow at such an immense
distance that the sky above would have the appearance of nothing more
than a narrow streak of blue. Yet these huge chasms have not been made
by any violent breaking apart of the rocks or convulsion of an
earthquake. No, they have been gradually, silently, and steadily cut
through by the river which now glides quietly in the wider chasms, or
rushes rapidly through the narrow gorges at their feet.

"No description," says Lieutenant Ives, one of the first explorers of
this river, "can convey the idea of the varied and majestic grandeur of
this peerless water-way. Wherever the river turns, the entire panorama
changes. Stately faades, august cathedrals, amphitheatres, rotundas,
castellated walls, and rows of time-stained ruins, surmounted by every
form of tower, minaret, dome and spire, have been moulded from the
cyclopean masses of rock that form the mighty defile." Who will say,
after this, that water is not the grandest of all sculptors, as it cuts
through hundreds of miles of rock, forming such magnificent granite
groups, not only unsurpassed but unequalled by any of the works of man?

       *       *       *       *       *

But we must not look upon water only as a cutting instrument, for it
does more than merely carve out land in one place, it also carries it
away and lays it down elsewhere; and in this it is more like a modeller
in clay, who smooths off the material from one part of his figure to put
it upon another.

Running water is not only always carrying away mud, but at the same time
laying it down here and there wherever it flows. When a torrent brings
down stones and gravel from the mountains, it will depend on the size
and weight of the pieces how long they will be in falling through the
water. If you take a handful of gravel and throw it into a glass full of
water, you will notice that the stones in it will fall to the bottom at
once, the grit and coarse sand will take longer in sinking, and lastly,
the fine sand will be an hour or two in settling down, so that the water
becomes clear. Now, suppose that this gravel were sinking in the water
of a river. The stones would be buoyed up as long as the river was very
full and flowed very quickly, but they would drop through sooner than
the coarse sand. The coarse sand in its turn would begin to sink as the
river flowed more slowly, and would reach the bottom while the fine sand
was still borne on. Lastly, the fine sand would sink through very, very
slowly, and only settle in comparatively still water.

From this it will happen that stones will generally lie near to the
bottom of torrents at the foot of the banks from which they fall, while
the gravel will be carried on by the stream after it leaves the
mountains. This too, however, will be laid down when the river comes
into a more level country and runs more slowly. Or it may be left
together with the finer mud in a lake, as in the lake of Geneva, into
which the Rhone flows laden with mud and comes out at the other end
clear and pure. But if no lake lies in the way the finer earth will
still travel on, and the river will take up more and more as it flows,
till at last it will leave this too on the plains across which it moves
sluggishly along, or will deposit it at its mouth when it joins the sea.

You all know the history of the Nile; how, when the rains fall very
heavily in March and April in the mountains of Abyssinia, the river
comes rushing down, and brings with it a load of mud which it spreads
out over the Nile valley in Egypt. This annual layer of mud is so thin
that it takes a thousand years for it to become 2 or 3 feet thick; but
besides that which falls in the valley a great deal is taken to the
mouth of the river and there forms new land, making what is called the
"Delta" of the Nile. Alexandria, Rosetta, and Damietta, are towns which
are all built on land made of Nile mud which was carried down ages and
ages ago, and which has now become firm and hard like the rest of the
country. You will easily remember other deltas mentioned in books, and
all these are made of the mud carried down from the land to the sea. The
delta of the Ganges and Brahmapootra in India, is actually as large as
the whole of England and Wales,[11] and the River Mississippi in America
drains such a large tract of country that its delta grows, Mr. Geikie
tells us, at the rate of 86 yards in a year.

All this new land laid down in Egypt, in India, in America, and in other
places, is the work of water. Even on the Thames you may see mud-banks,
as at Gravesend, which are made of earth brought from the interior of
England. But at the mouth of the Thames the sea washes up very strongly
every tide, and so it carries most of the mud away and prevents a delta
growing up there. If you will look about when you are at the seaside,
and notice wherever a stream flows down into the sea, you may even see
little miniature deltas being formed there, though the sea generally
washes them away again in a few hours, unless the place is well
sheltered.

This, then, is what becomes of the earth carried down by rivers. Either
on plains, or in lakes, or in the sea, it falls down to form new land.
But what becomes of the dissolved chalk and other substances? We have
seen that a great deal of it is used by river and sea animals to build
their shells and skeletons, and some of it is left on the surface of the
ground by springs when the water evaporates. It is this carbonate of
lime which forms a hard crust over anything upon which it may happen to
be deposited, and then these things are called "petrified."

But it is in the caves and hollows of the earth that this dissolved
matter is built up into the most beautiful forms. If you have ever been
to Buxton in Derbyshire, you will probably have visited a cavern called
Poole's Cavern, not far from there, which when you enter it looks as if
it were built up entirely of rods of beautiful transparent white glass,
hanging from the ceiling, from the walls, or rising up from the floor.
In this cavern, and many others like it,[12] water comes dripping
through the roof, and as it falls slowly drop by drop it leaves behind a
little of the carbonate of lime it has brought out of the rocks. This
carbonate of lime forms itself into a thin, white film on the roof,
often making a complete circle, and then, as the water drips from it day
by day, it goes on growing and growing till it forms a long
needle-shaped or tube-shaped rod, hanging like an icicle. These rods are
called _stalactites_, and they are so beautiful, as their minute
crystals glisten when a light is taken into the cavern, that one of them
near Tenby is called the "Fairy Chamber." Meanwhile, the water which
drips on to the floor also leaves some carbonate of lime where it
falls, and this forms a pillar, growing up towards the roof, and often
the hanging stalactites and the rising pillars (called _stalagmites_)
meet in the middle and form one column. And thus we see that
underground, as well as above-ground, water moulds beautiful forms in
the crust of the earth. At Adelsberg, near Trieste, there is a
magnificent stalactite grotto made of a number of chambers one following
another, with a river flowing through them; and the famous Mammoth Cave
of Kentucky, more than ten miles long, is another example of these
wonderful limestone caverns.

       *       *       *       *       *

But we have not yet spoken of the sea, and this surely is not idle in
altering the shape of the land. Even the waves themselves in a storm
wash against the cliffs and bring down stones and pieces of rock on to
the shore below. And they help to make cracks and holes in the cliffs,
for as they dash with force against them they compress the air which
lies in the joints of the stone and cause it to force the rock apart,
and so larger cracks are made and the cliff is ready to crumble.

It is, however, the stones and sand and pieces of rock lying at the foot
of the cliff which are most active in wearing it away. Have you never
watched the waves breaking upon a beach in a heavy storm? How they catch
up the stones and hurl them down again, grinding them against each
other! At high tide in such a storm these stones are thrown against the
foot of the cliff, and each blow does something towards knocking away
part of the rock, till at last, after many storms the cliff is
undermined and large pieces fall down. These pieces are in their turn
ground down to pebbles which serve to batter against the remaining rock.

Professor Geikie tells us that the waves beat in a storm against the
Bell Rock Lighthouse with as much force as if you dashed a weight of 3
tons against every square inch of the rock, and Stevenson found stones
of 2 tons' weight which had been thrown during storms right over the
ledge of the lighthouse. Think what force there must be in waves which
can lift up such a rock and throw it, and such force as this beats upon
our sea-coasts and eats away the land.

[Illustration: Fig. 28. Cliffs off Arbroath, showing the waste of
  the shore.]

Fig. 28 is a sketch on the shores of Arbroath which I made some years
ago. You will not find it difficult to picture to yourselves how the
sea has eaten away these cliffs till some of the strongest pieces which
have resisted the waves stand out by themselves in the sea. That cave in
the left-hand corner ends in a narrow dark passage from which you come
out on the other side of the rocks into another bay. Such caves as these
are made chiefly by the force of the waves and the air, bringing down
pieces of rock from under the cliff and so making a cavity, and then as
the waves roll these pieces over and over and grind them against the
sides, the hole is made larger. There are many places on the English
coast where large pieces of the road are destroyed by the crumbling down
of cliffs when they have been undermined by caverns such as these.

Thus, you see, the whole of the beautiful scenery of the sea--the
shores, the steep cliffs, the quiet bays, the creeks and caverns--are
all the work of the "sculptor" water; and he works best where the rocks
are hardest, for there they offer him a good stout wall to batter,
whereas in places where the ground is soft it washes down into a gradual
gentle slope, and so the waves come flowing smoothly in and have no
power to eat away the shore.

       *       *       *       *       *

And now, what has Ice got to do with the sculpturing of the land? First,
we must remember how much the frost does in breaking up the ground. The
farmers know this, and always plough after a frost, because the
moisture, freezing in the ground, has broken up the clods, and done half
their work for them.

But this is not the chief work of ice. You will remember how we learnt
in our last lecture that snow, when it falls on the mountains, gradually
slides down into the valleys, and is pressed together by the gathering
snow behind until it becomes moulded into a solid river of ice (see Fig.
29, Frontispiece). In Greenland and in Norway there are enormous
ice-rivers or glaciers, and even in Switzerland some of them are very
large. The Aletsch glacier, in the Alps, is fifteen miles long, and some
are even longer than this. They move very slowly--on an average about 20
to 27 inches in the centre, and 13 to 19 inches at the sides every
twenty-four hours, in summer and autumn. _How_ they move, we cannot stop
to discuss now; but if you will take a slab of thin ice and rest it upon
its two ends only, you can prove to yourself that ice does bend, for in
a few hours you will find that its own weight has drawn it down in the
centre so as to form a curve. This will help you to picture to
yourselves how glaciers can adapt themselves to the windings of the
valley, creeping slowly onwards until they come down to a point where
the air is warm enough to melt them, and then the ice flows away in a
stream of water. It is very curious to see the number of little rills
running down the great masses of ice at the glacier's mouth, bringing
down with them gravel, and every now and then a large stone, which falls
splashing into the stream below. If you look at the glacier in the
Frontispiece, you will see that these stones come from those long lines
of stones and boulders stretching along the sides and centre of the
glacier. It is easy to understand where the stones at the side come
from; for we have seen that damp and frost cause pieces to break off the
surface of the rocks, and it is natural that these pieces should roll
down the steep sides of the mountains on to the glacier. But the middle
row requires some explanation. Look to the back of the picture, and you
will see that this line of stones is made of two side rows, which come
from the valleys above. Two glaciers, you see, have there joined into
one, and so made a heap of stones all along their line of junction.

These stones are being continually, though slowly, conveyed by the
glacier, from all the mountains along its sides, down to the place where
it melts. Here it lets them fall, and they are gradually piled up till
they form great walls of stone, which are called _moraines_. Some of the
moraines left by the larger glaciers of olden time, in the country near
Turin, form high hills, rising up even to 1500 feet.

Therefore, if ice did no more than carry these stone blocks, it would
alter the face of the country; but it does much more than this. As the
glacier moves along, it often cracks for a considerable way across its
surface, and this crack widens and widens, until at last it becomes a
great gaping chasm, or _crevasse_ as it is called, so that you can look
down it right to the bottom of the glacier. Into these crevasses large
blocks of rock fall, and when the chasm is closed again as the ice
presses on, these masses are frozen firmly into the bottom of the
glacier, much in the same way as a steel cutter is fixed in the bottom
of a plane. And they do just the same kind of work; for as the glacier
slides down the valley, they scratch and grind the rocks underneath
them, rubbing themselves away, it is true, but also scraping away the
ground over which they move. In this way the glacier becomes a cutting
instrument, and carves out the valleys deeper and deeper as it passes
through them.

You may always know where a glacier has been, even if no trace of ice
remains; for you will see rocks with scratches along them which have
been cut by these stones; and even where the rocks have not been ground
away, you will find them rounded like those in the left-hand of the
Frontispiece, showing that the glacier-plane has been over them. These
rounded rocks are called "roches moutonnes," because at the distance
they look like sheep lying down.

You have only to look at the stream flowing from the mouth of a glacier
to see what a quantity of soil it has ground off from the bottom of the
valley; for the water is thick, and coloured a deep yellow by the mud it
carries. This mud soon reaches the rivers into which the streams run;
and such rivers as the Rhone and the Rhine are thick with matter brought
down from the Alps. The Rhone leaves this mud in the Lake of Geneva,
flowing out at the other end quite clear and pure. A mile and a half of
land has been formed at the head of the lake since the time of the
Romans by the mud thus brought down from the mountains.

Thus we see that ice, like water, is always busy carving out the surface
of the earth, and sending down material to make new land elsewhere. We
know that in past ages the glaciers were much larger than they are in
our time; for we find traces of them over large parts of Switzerland
where glaciers do not now exist, and huge blocks which could only have
been carried by ice, and which are called "erratic blocks," some of them
as big as cottages, have been left scattered over all the northern part
of Europe. These blocks were a great puzzle to scientific men till, in
1840, Professor Agassiz showed that they must have been brought by ice
all the way from Norway and Russia.

In those ancient days, there were even glaciers in England; for in
Cumberland and in Wales you may see their work, in scratched and rounded
rocks, and the moraines they have left. Llanberis Pass, so famous for
its beauty, is covered with ice-scratches, and blocks are scattered all
over the sides of the valley. There is one block high up on the
right-hand slope of the valley, as you enter from the Beddgelert side,
which is exactly poised upon another block, so that it rocks to and fro.
It must have been left thus balanced when the ice melted round it. You
may easily see that these blocks were carried by ice, and not by water,
because their edges are sharp, whereas, if they had been rolled in
water, they would have been smoothed down.

We cannot here go into the history of that great Glacial Period long
ago, when large fields of ice covered all the north of England; but when
you read it for yourselves and understand the changes on the earth's
surface which we can see being made by ice now, then such grand scenery
as the rugged valleys of Wales, with large angular stone blocks
scattered over them, will tell you a wonderful story of the ice of
bygone times.

And now we have touched lightly on the chief ways in which water and ice
carve out the surface of the earth. We have seen that rain, rivers,
springs, the waves of the sea, frost, and glaciers all do their part in
chiselling out ravines and valleys, and in producing rugged peaks or
undulating plains--here cutting through rocks so as to form precipitous
cliffs, there laying down new land to add to the flat country--in one
place grinding stones to powder, in others piling them up in gigantic
ridges. We cannot go a step into the country without seeing the work of
water around us; every little gully and ravine tells us that the
sculpture is going on; every stream, with its burden of visible or
invisible matter, reminds us that some earth is being taken away and
carried to a new spot. In our little lives we see indeed but very small
changes, but by these we learn how greater ones have been brought about,
and how we owe the outline of all our beautiful scenery, with its hills
and valleys, its mountains and plains, its cliffs and caverns, its quiet
nooks and its grand rugged precipices, to the work of the "Two great
sculptors, Water and Ice."

[Illustration]




LECTURE VI.

THE VOICES OF NATURE AND HOW WE HEAR THEM.


[Illustration]

We have reached to-day the middle point of our course, and here we will
make a new start. All the wonderful histories which we have been
studying in the last five lectures have had little or nothing to do
with living creatures. The sunbeams would strike on our earth, the air
would move restlessly to and fro, the water-drops would rise and fall,
the valleys and ravines would still be cut out by rivers, if there were
no such thing as life upon the earth. But without living things there
could be none of the beauty which these changes bring about. Without
plants, the sunbeams the air and the water would be quite unable to
clothe the bare rocks, and without animals and man they could not
produce light, or sound, or feeling of any kind.

In the next five lectures, however, we are going to learn something of
the use living creatures make of the earth; and to-day we will begin by
studying one of the ways in which _we_ are affected by the changes of
nature, and hear her voice.

We are all so accustomed to trust to our sight to guide us in most of
our actions, and to think of things as we see them, that we often forget
how very much we owe to _sound_. And yet Nature speaks to us so much by
her gentle, her touching, or her awful sounds, that the life of a deaf
person is even more hard to bear than that of a blind one.

Have you ever amused yourself with trying how many different sounds you
can distinguish if you listen at an open window in a busy street? You
will probably be able to recognize easily the jolting of the heavy
waggon or dray, the rumble of the omnibus, the smooth roll of the
private carriage and the rattle of the light butcher's cart; and even
while you are listening for these, the crack of the carter's whip, the
cry of the costermonger at his stall, and the voices of the passers by
will strike upon your ear. Then if you give still more close attention
you will hear the doors open and shut along the street, the footsteps of
the passengers, the scraping of the shovel of the mud-carts; nay, if he
happen to stand near, you may even hear the jingling of the shoeblack's
pence as he plays pitch and toss upon the pavement. If you think for a
moment, does it not seem wonderful that you should hear all these sounds
so that you can recognize each one distinctly while all the rest are
going on around you?

But suppose you go into the quiet country. Surely there will be silence
_there_. Try some day and prove it for yourself, lie down on the grass
in a sheltered nook and listen attentively. If there be ever so little
wind stirring you will hear it rustling gently through the trees; or
even if there is not this, it will be strange if you do not hear some
wandering gnat buzzing, or some busy bee humming as it moves from flower
to flower. Then a grasshopper will set up a chirp within a few yards of
you, or, if all living creatures are silent, a brook not far off may be
flowing along with a rippling musical sound. These and a hundred other
noises you will hear in the most quiet country spot; the lowing of
cattle, the song of the birds, the squeak of the field-mouse, the croak
of the frog, mingling with the sound of the woodman's axe in the
distance, or the dash of some river torrent. And besides these quiet
sounds, there are still other occasional voices of nature which speak to
us from time to time. The howling of the tempestuous wind, the roar of
the sea-waves in a storm, the crash of thunder, and the mighty noise of
the falling avalanche; such sounds as these tell us how great and
terrible nature can be.

Now, has it ever occurred to you to think what sound is, and how it is
that we hear all these things? Strange as it may seem, if there were no
creature that could hear upon the earth, there would be no such thing as
sound, though all these movements in nature were going on just as they
are now.

Try and grasp this thoroughly, for it is difficult at first to make
people believe it. Suppose you were stone-deaf, there would be no such
thing as sound to you. A heavy hammer falling on an anvil would indeed
shake the air violently, but since this air when it reached your ear
would find a useless instrument, it could not play upon it. _And it is
this play on the drum of your ear and the nerves within it speaking to
your brain which makes sound._ Therefore, if all creatures on or around
the earth were without ears or nerves of hearing, there would be no
instruments on which to play, and consequently there would be no such
thing as sound. This proves that two things are needed in order that we
may hear. First, the outside movement which plays on our hearing
instrument; and, secondly, the hearing instrument itself.

       *       *       *       *       *

First, then, let us try to understand what happens outside our ears.
Take a poker and tie a piece of string to it, and holding the ends of
the string to your ears, strike the poker against the fender. You will
hear a very loud sound, for the blow will set all the particles of the
poker quivering, and this movement will pass right along the string to
the drum of your ear and play upon it.

Now take the string away from your ears, and hold it with your teeth.
Stop your ears tight, and strike the poker once more against the fender.
You will hear the sound quite as loudly and clearly as you did before,
but this time the drum of your ear has not been agitated. How, then, has
the sound been produced? In this case, the quivering movement has passed
through your teeth into the bones of your head, and from them into the
nerves, and so produced sound in your brain. And now, as a final
experiment, fasten the string to the mantelpiece, and hit it again
against the fender. How much feebler the sound is this time, and how
much sooner it stops! Yet still it reaches you, for the movement has
come this time across the air to the drum of your ear.

Here we are back again in the land of invisible workers! We have all
been listening and hearing ever since we were babies, but have we ever
made any picture to ourselves of _how_ sound comes to us right across a
room or a field, when we stand at one end and the person who calls is at
the other?

Since we have studied the "aerial ocean," we know that the air filling
the space between us, though invisible, is something very real, and now
all we have to do is to understand exactly how the movement crosses this
air.

This we shall do most readily by means of an experiment made by Dr.
Tyndall in his lectures on Sound. I have here a number of boxwood balls
resting in a wooden tray which has a bell hung at the end of it. I am
going to take the end ball and roll it sharply against the rest, and
then I want you to notice carefully what happens. See! the ball at the
other end has flown off and hit the bell, so that you hear it ring. Yet
the other balls remain where they were before. Why is this? It is
because each of the balls, as it was knocked forwards, had one in front
of it to stop it and make it bound back again, but the last one was free
to move on. When I threw this ball from my hand against the others, the
one in front of it moved, and hitting the third ball, bounded back
again; the third did the same to the fourth, the fourth to the fifth,
and so on to the end of the line. Each ball thus came back to its place,
but it passed the shock on to the last ball, and the ball to the bell.
If I now put the balls close up to the bell, and repeat the experiment,
you still hear the sound, for the last ball shakes the bell as if it
were a ball in front of it.

[Illustration: Fig. 30.]

Now imagine these balls to be atoms of air, and the bell your ear. If I
clap my hands and so hit the air in front of them, each air-atom hits
the next just as the balls did, and though it comes back to its place,
it passes the shock on along the whole line to the atom touching the
drum of your ear, and so you receive a blow. But a curious thing
happens in the air which you cannot notice in the balls. You must
remember that air is elastic, just as if there were springs between the
atoms as in the diagram, Fig. 31, and so when any shock knocks the atoms
forward, several of them can be crowded together before they push on
those in front. Then, as soon as they have passed the shock on, they
rebound and begin to separate again, and so swing to and fro till they
come to rest. Meanwhile the second set will go through just the same
movements, and will spring apart as soon as they have passed the shock
on to a third set, and so you will have one set of crowded atoms and one
set of separated atoms alternately all along the line, and the same set
will never be crowded two instants together.

[Illustration: Fig. 31.]

You may see an excellent example of this in a luggage train in a railway
station, when the trucks are left to bump each other till they stop. You
will see three or four trucks knock together, then they will pass the
shock on to the four in front, while they themselves bound back and
separate as far as their chains will let them: the next four trucks will
do the same, and so a kind of wave of crowded trucks passes on to the
end of the train, and they bump to and fro till the whole comes to a
standstill. Try to imagine a movement like this going on in the line of
air-atoms, Fig. 31, the drum of your ear being at the end B. Those which
are crowded together at that end will hit on the drum of your ear and
drive the membrane which covers it inwards; then instantly the wave will
change, these atoms will bound back, and the membrane will recover
itself again, but only to receive a second blow as the atoms are driven
forwards again, and so the membrane will be driven in and out till the
air has settled down.

This you see is quite different to the waves of light which move in
crests and hollows. Indeed, it is not what we usually understand by a
wave at all, but a set of crowdings and partings of the atoms of air
which follow each other rapidly across the air. A crowding of atoms is
called a _condensation_, and a parting is called a _rarefaction_, and
when we speak of the length of a wave of sound, we mean the distance
between two condensations, _a a_ Fig. 32, or between two rarefactions,
_b b_.

[Illustration: Fig. 32.]

Although each atom of air moves a very little way forwards and then
back, yet, as a long row of atoms may be crowded together before they
begin to part, a wave is often very long. When a man talks in an
ordinary bass voice, he makes sound-waves from 8 to 12 feet long; a
woman's voice makes shorter waves, from 2 to 4 feet long, and
consequently the tone is higher, as we shall presently explain.

And now I hope that some one is anxious to ask why, when I clap my
hands, anyone behind me or at the side, can hear it as well or nearly as
well as you who are in front. This is because I give a shock to the air
all round my hands, and waves go out on all sides, making as it were
globes of crowdings and partings widening and widening away from the
clap as circles widen on a pond. Thus the waves travel behind me, above
me, and on all sides, until they hit the walls, the ceiling, and the
floor of the room, and wherever you happen to be, they hit upon your
ear.

If you can picture to yourself these waves spreading out in all
directions, you will easily see why sound grows fainter at the distance.
Just close round my hands when I clap them, there is a small quantity of
air, and so the shock I give it is very violent, but as the sound-waves
spread on all sides they have more and more air to move, and so the
air-atoms are shaken less violently and strike with less force on your
ear.

If we can prevent the sound-wave from spreading, then the sound is not
weakened. The Frenchman Biot found that a low whisper could be heard
distinctly for a distance of half a mile through a tube, because the
waves could not spread beyond the small column of air. But unless you
speak into a small space of some kind, you cannot prevent the waves
going out from you in all directions.

Try and imagine that you see these waves spreading all round me now and
hitting on your ears as they pass, then on the ears of those behind you,
and on and on in widening globes till they reach the wall. What will
happen when they get there? If the wall were thin, as a wooden partition
is, they would shake it, and it again would shake the air on the other
side, and so anyone in the next room would have the sound of my voice
brought to their ear.

But something more will happen. In any case the sound-waves hitting
against the wall will bound back from it just as a ball bounds back when
thrown against anything, and so another set of sound-waves reflected
from the wall will come back across the room. If these waves come to
your ear so quickly that they mix with direct waves, they help to make
the sound louder. For instance, if I say "Ha," you hear that sound
louder in this room than you would in the open air, for the "Ha" from my
mouth and a second "Ha" from the wall come to your ear so
instantaneously that they make one sound. This is why you can often hear
better at the far end of a church when you stand against a screen or a
wall, than when you are half-way up the building nearer to the speaker,
because near the wall the reflected waves strike strongly on your ear
and make the sound louder.

Sometimes, when the sound comes from a great explosion, these reflected
waves are so strong that they are able to break glass. In the explosion
of gunpowder in St. John's Wood, many houses in the back streets had
their windows broken; for the sound-waves bounded off at angles from the
walls and struck back upon them.

Now, suppose the wall were so far behind you that the reflected
sound-waves only hit upon your ear after those coming straight from me
had died away; then you would hear the sound twice, "Ha" from me and
"Ha" from the wall, and here you have an echo, "Ha, ha." In order for
this to happen in ordinary air, you must be standing at least 56 feet
away from the point from which the waves are reflected, for then the
second blow will come one-tenth of a second after the first one, and
that is long enough for you to feel them separately.[13] Miss. C. A.
Martineau tells a story of a dog which was terribly frightened by an
echo. Thinking another dog was barking, he ran forward to meet him, and
was very much astonished, when, as he came nearer the wall, the echo
ceased. I myself once knew a case of this kind, and my dog, when he
could find no enemy, ran back barking, till he was a certain distance
off, and then the echo of course began again. He grew so furious at last
that we had great difficulty in preventing him from flying at a strange
man who happened to be passing at the time.

Sometimes, in the mountains, walls of rock rise at some distance one
behind another, and then each one will send back its echo a little later
than the rock before it, so that the "Ha" which you give will come back
as a peal of laughter. There is an echo in Woodstock Park which repeats
the word twenty times. Again sometimes, as in the Alps, the sound-waves
in coming back rebound from mountain to mountain and are driven
backwards and forwards, becoming fainter and fainter till they die away;
these echoes are very beautiful.

If you are now able to picture to yourselves one set of waves going to
the wall, and another set returning and crossing them, you will be ready
to understand something of that very difficult question. How is it that
we can hear many different sounds at one time and tell them apart?

Have you ever watched the sea when its surface is much ruffled, and
noticed how, besides the big waves of the tide, there are numberless
smaller ripples made by the wind blowing the surface of the water, or
the oars of a boat dipping in it, or even rain-drops falling? If you
have done this you will have seen that all these waves and ripples cross
each other, and you can follow any one ripple with your eye as it goes
on its way undisturbed by the rest. Or you may make beautiful crossing
and recrossing ripples on a pond by throwing in two stones at a little
distance from each other, and here too you can follow any one wave on to
the edge of the pond.

Now just in this way the waves of sound, in their manner of moving,
cross and recross each other. You will remember too, that different
sounds make waves of different lengths, just as the tide makes a long
wave and the rain-drops tiny ones. Therefore each sound falls with its
own peculiar wave upon your ear, and you can listen to that particular
wave just as you look at one particular ripple, and then the sound
becomes clear to you.

All this is what is going on outside your ear, but what is happening in
your ear itself? How do these blows of the air speak to your brain? By
means of the following diagram, Fig. 33, we will try to understand
roughly our beautiful hearing instrument, the ear.

[Illustration: Fig. 33.
_a_, Concha, or shell of the ear.
_b c_, Auditory canal.
_c_, Tympanic membrane stretched across the drum of the ear.
E, Eustachian tube.
_d_, _e_, _f_, ear-bones:
_d_, the hammer, _malleus_;
_e_, the anvil, _incus_;
_f_, the stirrup, _stapes_.
L, Labyrinth.
_g_, Cochlea, or internal spiral shell.
_h_, One of the little windows; the other is covered by the stirrup.]

First, I want you to notice how beautifully the outside shell, or
_concha_ as it is called (_a_), is curved round so that any movement of
the air coming to it from the front is caught in it and reflected into
the hole of the ear. Put your finger round your ear and feel how the
gristly part is curved towards the front of your head. This concha
makes a curve much like the curve a deaf man makes with his hand behind
his ear to catch the sound. Animals often have to raise their ears to
catch the sound well, but ours stand always ready. When the air-waves
have passed in at the hole of your ear, they move all the air in the
passage, _b c_, which is called the auditory, or hearing, canal. This
canal is lined with little hairs to keep out insects and dust, and the
wax which collects in it serves the same purpose. But if too much wax
collects, it prevents the air from playing well upon the drum, and
therefore makes you deaf. Across the end of this canal, at _c_, a
membrane or skin called the _tympanum_ is stretched, like the parchment
over the head of a drum, and it is this membrane which moves to and fro
as the air-waves strike on it. A violent box on the ear will sometimes
break this delicate membrane, or injure it, and therefore it is very
wrong to hit a person violently on the ear.

On the other side of this membrane, _inside_ the ear, there is air,
which fills the whole of the inner chamber and the tube E, which runs
down into the throat behind the nose, and is called the Eustachian tube
after the man who discovered it. This tube is closed at the end by a
valve which opens and shuts. If you breathe out strongly, and then shut
your mouth and swallow, you will hear a little "click" in your ear. This
is because in swallowing you draw the air out of the Eustachian tube and
so draw in the membrane _c_, which clicks as it goes back again. But
unless you do this the tube and the whole chamber cavity behind the
membrane remains full of air.

Now, as this membrane is driven to and fro by the sound-waves, it
naturally shakes the air in the cavity behind it, and it also sets
moving three most curious little bones. The first of these bones _d_ is
fastened to the middle of the drumhead so that it moves to and fro every
time this membrane quivers. The head of this bone fits into a hole in
the next bone _e_, the anvil, and is fastened to it by muscles, so as to
drag it along with it; but, the muscles being elastic, it can draw back
a little from the anvil, and so give it a blow each time it comes back.
This anvil, _e_ is in its turn very firmly fixed to the little bone _f_,
shaped like a stirrup, which you see at the end of the chain.

This stirrup rests upon a curious body L, which looks in the diagram
like a snail-shell with tubes coming out of it. This body, which is
called the _labyrinth_, is made of bone, but it has two little windows
in it, one _h_ covered only by a membrane, while the other has the head
of the stirrup _f_ resting upon it.

Now, with a little attention you will understand that when the air in
the canal _b c_ shakes the drumhead _c_ to and fro, this membrane must
drag with it the hammer, the anvil, and the stirrup. Each time the drum
goes in, the hammer will hit the anvil, and drive the stirrup against
the little window; every time it goes out it will draw the hammer, the
anvil, and the stirrup out again, ready for another blow. Thus the
stirrup is always playing upon this little window. Meanwhile, inside the
bony labyrinth L there is a fluid like water, and along the little
passages are very fine hairs, which wave to and fro like reeds; and
whenever the stirrup hits at the little window, the fluid moves these
hairs to and fro, and they irritate the ends of a nerve _i_, and this
nerve carries the message to your brain. There are also some curious
little stones called otoliths, lying in some parts of this fluid, and
they, by their rolling to and fro, probably keep up the motion and
prolong the sound.

You must not imagine we have explained here the many intricacies which
occur in the ear; I can only hope to give you a rough idea of it, so
that you may picture to yourselves the air-waves moving (as in Fig. 32)
backwards and forward in the canal of your ear, then the tympanum
vibrating to and fro, the hammer hitting the anvil, the stirrup knocking
at the little window, the fluid waving the fine hairs and rolling the
tiny stones, the ends of the nerve quivering, and then (_how_ we know
not) the brain hearing the message.

Is not this wonderful, going on as it does at every sound you hear? And
yet this is not all, for inside that curled part of the labyrinth _g_,
which looks like a snail-shell and is called the _cochlea_, there is a
most wonderful apparatus of more than three thousand fine stretched
filaments or threads, and these act like the strings of a harp, and make
you hear different tones. If you go near to a harp or a piano, and sing
any particular note very loudly, you will hear this note sounding in the
instrument, because you will set just that particular string quivering,
which gives the note you sang. The air-waves set going by your voice
touch that string, because it can quiver in time with them, while none
of the other strings can do so. Now, just in the same way the tiny
instrument of three thousand strings in your ear, which is called
Corti's organ, vibrates to the air-waves, one thread to one set of
waves, and another to another, and according to the fibre that quivers,
will be the sound you hear. Here then at last, we see how nature speaks
to us. All the movements going on outside, however violent and varied
they may be, cannot of themselves make sound. But here, in the little
space behind the drum of our ear, the air-waves are sorted and sent on
to our brain, where they speak to us as sound.

       *       *       *       *       *

But why then do we not hear all sounds as music? Why are some mere
noise, and others clear musical notes? This depends entirely upon
whether the sound-waves come quickly and regularly, or by an irregular
succession of shocks. For example, when a load of stones is being shot
out of a cart, you hear only a long continuous noise, because the stones
fall irregularly, some quicker, some slower, here a number together, and
there two or three stragglers by themselves; each of these different
shocks comes to your ear and makes a confused, noisy sound. But if you
run a stick very quickly along a paling, you will hear a sound very like
a musical note. This is because the rods of the paling are all at equal
distances one from the other, and so the shocks fall quickly one after
another at regular intervals upon your ear. Any quick and _regular_
succession of sounds makes a note, even though it may be an ugly one.
The squeak of a slate pencil along a slate, and the shriek of a railway
whistle are not pleasant, but they are real notes which you could copy
on a violin.

I have here a simple apparatus which I have had made to show you that
rapid and regular shocks produce a natural musical note. This wheel
(Fig. 34) is milled at the edge like a shilling, and when I turn it
rapidly so that it strikes against the edge of the card fixed behind it,
the notches strike in rapid succession, and produce a musical sound. We
can also prove by this experiment that the quicker the blows are, the
higher the note will be. I pull the string gently at first, and then
quicker and quicker, and you will notice that the note grows sharper and
sharper, till the movement begins to slacken, when the note goes down
again. This is because the more rapidly the air is hit, the shorter are
the waves it makes, and short waves give a high note.

[Illustration: Fig. 34.]

Let us examine this with two tuning-forks. I strike one, and it sounds
C, the third space in the treble; I strike the other, and it sounds A,
the first leger line, five notes above the C. I have drawn on this
diagram (Fig. 35), an imaginary picture of these two sets of waves. You
see that the A fork makes three waves, while the C fork makes only two.
Why is this? Because the prong of the A fork moves three times backwards
and forwards while the prong of the C fork only moves twice; therefore
the A fork does not crowd so many atoms together before it draws back,
and the waves are shorter. These two notes, C and A, are a fifth apart;
if we had two forks, of which one went twice as fast as the other,
making four waves while the other made two, then the notes of these
forks would be an octave higher.

[Illustration: Fig. 35.]

       *       *       *       *       *

So we see that all the sounds we hear,--the warning noises which keep us
from harm, the beautiful musical notes with all the tunes and harmonies
that delight us, even the power of hearing the voices of those we love,
and learning from one another that which each can tell,--all these
depend upon the invisible waves of air, even as the pleasures of light
depend on the waves of ether. It is by these sound-waves that nature
speaks to us, and in all her movements there is a reason why her voice
is sharp or tender, loud or gentle, awful or loving. Take for instance
the brook we spoke of at the beginning of the lecture. Why does it sing
so sweetly, while the wide deep river makes no noise? Because the little
brook eddies and purls round the stones, hitting them as it passes;
sometimes the water falls down a large stone, and strikes against the
water below; or sometimes it grates the little pebbles together as they
lie in its bed. Each of these blows makes a small globe of sound-waves,
which spread and spread till they fall on your ear, and because they
fall quickly and regularly, they make a low, musical note. We might
almost fancy that the brook wished to show how joyfully it flows along,
recalling Shelley's beautiful lines:--

          "Sometimes it fell
    Among the moss with hollow harmony,
    Dark and profound; now on the polished stones
    It danced: like childhood laughing as it went."

The broad deep river, on the contrary, makes none of these cascades and
commotions. The only places against which it rubs are the banks and the
bottom; and here you can sometimes hear it grating the particles of sand
against each other if you listen very carefully. But there is another
reason why falling water makes a sound, and often even a loud roaring
noise in the cataract and in the breaking waves of the sea. You do not
only hear the water dashing against the rocky ledges or on the beach,
you also hear the bursting of innumerable little bladders of air which
are contained in the water. As each of these bladders is dashed on the
ground, it explodes and sends sound-waves to your ear. Listen to the sea
some day when the waves are high and stormy, and you cannot fail to be
struck by the irregular bursts of sound.

The waves, however, do not only roar as they dash on the ground; have
you never noticed how they seem to scream as they draw back down the
beach? Tennyson calls it,

    "The scream of the madden'd beach dragged down by the wave;"

and it is caused by the stones grating against each other as the waves
drag them down. Dr. Tyndall tells us that it is possible to know the
size of the stones by the kind of noise they make. If they are large, it
is a confused noise; when smaller, a kind of scream; while a gravelly
beach will produce a mere hiss.

Who could be dull by the side of a brook, a waterfall, or the sea, while
he can listen for sounds like these, and picture to himself how they are
being made? You may discover a number of other causes of sound made by
water, if you once pay attention to them.

Nor is it only water that sings to us. Listen to the wind, how sweetly
it sighs among the leaves. There we hear it, because it rubs the leaves
together, and they produce the sound-waves. But walk against the wind
some day and you can hear it whistling in your own ear, striking against
the curved cup, and then setting up a succession of waves in the hearing
canal of the ear itself.

Why should it sound in one particular tone when all kinds of
sound-waves must be surging about in the disturbed air?

[Illustration: Fig. 36.]

This glass jar will answer our question roughly. If I strike my
tuning-fork and hold it over the jar, you cannot hear it, because the
sound is feeble, but if I fill the jar gently with water, when the water
rises to a certain point you will hear a loud clear note, because the
waves of air in the jar are exactly the right length to answer to the
note of the fork. If I now blow across the mouth of the jar you hear the
same note, showing that a cavity of a particular length will only sound
to the waves which fit it. Do you see now the reason why pan-pipes give
different sounds, or even the hole at the end of a common key when you
blow across it? Here is a subject you will find very interesting if you
will read about it, for I can only just suggest it to you here. But now
you will see that the canal of your ear also answers only to certain
waves, and so the wind sings in your ear with a real if not a musical
note.

Again, on a windy night have you not heard the wind sounding a wild, sad
note down a valley? Why do you think it sounds so much louder and more
musical here than when it is blowing across the plain? Because the air
in the valley will only answer to a certain set of waves, and, like the
pan-pipe, gives a particular note as the wind blows across it, and these
waves go up and down the valley in regular pulses, making a wild howl.
You may hear the same in the chimney, or in the keyhole; all these are
waves set up in the hole across which the wind blows. Even the music in
the shell which you hold to your ear is made by the air in the shell
pulsating to and fro. And how do you think it is set going? By the
throbbing of the veins in your own ear, which causes the air in the
shell to vibrate.

Another grand voice of nature is the thunder. People often have a vague
idea that thunder is produced by the clouds knocking together, which is
very absurd, if you remember that clouds are but water-dust. The most
probable explanation of thunder is much more beautiful than this. You
will remember from Lecture III. that heat forces the air-atoms apart.
Now, when a flash of lightning crosses the sky it suddenly expands the
air all round it as it passes, so that globe after globe of sound-waves
is formed at every point across which the lightning travels. Now light,
you remember, travels so wonderfully rapidly (192,000 miles in a second)
that a flash of lightning is seen by us and is over in a second, even
when it is two or three miles long. But sound comes slowly, taking five
seconds to travel a mile, and so all the sound-waves at each point of
the two or three miles fall on our ear one after the other, and make the
rolling thunder. Sometimes the roll is made even longer by the echo, as
the sound-waves are reflected to and fro by the clouds on their road;
and in the mountains we know how the peals echo and re-echo till they
die away.

We might fill up far more than an hour in speaking of those voices which
come to us as nature is at work. Think of the patter of the rain, how
each drop as it hits the pavement sends circles of sound-waves out on
all sides; or the loud report which falls on the ear of the Alpine
traveller as the glacier cracks on its way down the valley; or the
mighty boom of the avalanche as the snow slides in huge masses off the
side of the lofty mountain. Each and all of these create their
sound-waves, large or small, loud or feeble, which make their way to
your ear, and become converted into sound.

We have, however, only time now just to glance at life-sounds, of which
there are so many around us. Do you know why we hear a buzzing, as the
gnat, the bee, or the cockchafer fly past? Not by the beating of their
wings against the air, as many people imagine, and as is really the case
with humming birds, but by the scraping of the under-part of their hard
wings against the edges of their hind-legs, which are toothed like a
saw. The more rapidly their wings move the stronger the grating sound
becomes, and you will now see why in hot, thirsty weather the buzzing of
the gnat is so loud, for the more thirsty and the more eager he becomes,
the wilder his movements will be.

Some insects, like the drone-fly (_Eristalis tenax_), force the air
through the tiny air-passages in their sides, and as these passages are
closed by little plates, the plates vibrate to and fro and make
sound-waves Again, what are those curious sounds you may hear sometimes
if you rest your head on a trunk in the forest? They are made by the
timber-boring beetles, which saw the wood with their jaws and make a
noise in the world, even though they have no voice.

All these life-sounds are made by creatures which do not sing or speak;
but the sweetest sounds of all in the woods are the voices of the birds.
All voice-sounds are made by two elastic bands or cushions, called vocal
chords, stretched across the end of the tube or windpipe through which
we breathe, and as we send the air through them we tighten or loosen
them as we will, and so make them vibrate quickly or slowly and make
sound-waves of different lengths. But if you will try some day in the
woods you will find that a bird can beat you over and over again in the
length of his note; when you are out of breath and forced to stop he
will go on with his merry trill as fresh and clear as if he had only
just begun. This is because birds can draw air into the whole of their
body, and they have a large stock laid up in the folds of their
windpipe, and besides this the air-chamber behind their elastic bands or
vocal chords has two compartments where we have only one, and the second
compartment has special muscles by which they can open and shut it, and
so prolong the trill.

Only think what a rapid succession of waves must quiver through the air
as a tiny lark agitates his little throat and pours forth a volume of
song! The next time you are in the country in the spring, spend half an
hour listening to him, and try and picture to yourself how that little
being is moving all the atmosphere round him. Then dream for a little
while about sound, what it is, how marvellously it works outside in the
world, and inside in your ear and brain; and then, when you go back to
work again, you will hardly deny that it is well worth while to listen
sometimes to the voices of nature and ponder how it is that we hear
them.

[Illustration]




LECTURE VII.

THE LIFE OF A PRIMROSE.

[Illustration]


When the dreary days of winter and the early damp days of spring are
passing away, and the warm bright sunshine has begun to pour down upon
the grassy paths of the wood, who does not love to go out and bring home
posies of violets, and bluebells, and primroses? We wander from one
plant to another, picking a flower here and a bud there, as they nestle
among the green leaves, and we make our rooms sweet and gay with the
tender and lovely blossoms. But tell me, did you ever stop to think, as
you added flower after flower to your nosegay, how the plants which bear
them have been building up their green leaves and their fragile buds
during the last few weeks? If you had visited the same spot a month
before, a few last year's leaves, withered and dead, would have been all
that you would have found. And now the whole wood is carpeted with
delicate green leaves, with nodding bluebells, and pale-yellow
primroses, as if a fairy had touched the ground and covered it with
fresh young life. And our fairies have been at work here; the fairy
"Life," of whom we know so little, though we love her so well and
rejoice in the beautiful forms she can produce; the fairy sunbeams with
their invisible influence kissing the tiny shoots and warming them into
vigour and activity; the gentle rain-drops, the balmy air, all these
have been working, while you or I passed heedlessly by; and now we come
and gather the flowers they have made, and too often forget to wonder
how these lovely forms have sprung up around us.

Our work during the next hour will be to consider this question. You
were asked last week to bring with you to-day a primrose-flower, or a
whole plant if possible, in order the better to follow out with me the
"Life of a Primrose."[14] This is a very different kind of subject from
those of our former lectures. There we took world-wide histories; we
travelled up to the sun, or round the earth, or into the air; now I only
ask you to fix your attention on one little plant, and inquire into its
history.

There is a beautiful little poem by Tennyson, which says--

    "Flower in the crannied wall,
    I pluck you out of the crannies;
    Hold you here, root and all, in my hand,
    Little flower; but if I could understand
    What you are, root and all, and all in all,
    I should know what God and man is."

We cannot learn _all_ about this little flower, but we can learn enough
to understand that it has a real separate life of its own, well worth
knowing. For a plant is born, breathes, sleeps, feeds, and digests just
as truly as an animal does, though in a different way. It works hard
both for itself to get its food, and for others in making the air pure
and fit for animals to breathe. It often lays by provision for the
winter. It sends young plants out, as parents send their children, to
fight for themselves in the world; and then, after living sometimes to a
good old age, it dies, and leaves its place to others.

We will try to follow out something of this life to-day; and first, we
will begin with the seed.

I have here a packet of primrose-seeds, but they are so small that we
cannot examine them; so I have also had given to each one of you an
almond-kernel, which is the seed of the almond-tree, and which has been
soaked, so that it splits in half easily. From this we can learn about
seeds in general, and then apply it to the primrose.

[Illustration: Fig. 37. Half an almond, showing the plantlet.
_a_, rudiment of stem.
_b_, beginning of root.]

If you peel the two skins off your almond-seed (the thick, brown,
outside skin, and the thin, transparent one under it), the two halves of
the almond will slip apart quite easily. One of these halves will have a
small dent at the pointed end, while in the other half you will see a
little lump, which fitted into the dent when the two halves were joined.
This little lump (_a b_, Fig. 37) is a young plant, and the two halves
of the almond are the seed-leaves which hold the plantlet, and feed it
till it can feed itself. The rounded end of the plantlet (_b_) sticking
out of the almond, is the beginning of the root, while the other end
(_a_) will in time become the stem. If you look carefully, you will see
two little points at this end, which are the tips of future leaves. Only
think how minute this plantlet must be in a primrose, where the whole
seed is scarcely larger than a grain of sand! Yet in this tiny plantlet
lies hid the life of the future plant.

When a seed falls into the ground, so long as the earth is cold and dry,
it lies like a person in a trance, as if it were dead; but as soon as
the warm, damp spring comes, and the busy little sun-waves pierce down
into the earth, they wake up the plantlet, and make it bestir itself.
They agitate to and fro the particles of matter in this tiny body, and
cause them to seek out for other particles to seize and join to
themselves.

But these new particles cannot come in at the roots, for the seed has
none; nor through the leaves, for they have not yet grown up; and so the
plantlet begins by helping itself to the store of food laid up in the
thick seed-leaves in which it is buried. Here it finds starch, oils,
sugar, and substances called albuminoids,--the sticky matter which you
notice in wheat-grains when you chew them is one of the albuminoids.
This food is all ready for the plantlet to use, and it sucks it in, and
works itself into a young plant with tiny roots at one end, and a
growing shoot, with leaves, at the other.

[Illustration: Fig. 38. Juicy cells in a piece of orange.]

But how does it grow? What makes it become larger? To answer this, you
must look at the second thing I asked you to bring--a piece of orange.
If you take the skin off a piece of orange, you will see inside a number
of long-shaped transparent bags, full of juice. These we call cells, and
the flesh of all plants and animals is made up of cells like these, only
of various shapes. In the pith of elder they are round, large, and
easily seen (_a_, Fig. 39); in the stalks of plants they are long, and
lap over each other (_b_, Fig. 39), so as to give the stalk strength to
stand upright. Sometimes many cells growing one on the top of the other,
break into one tube and make _vessels_. But whether large or small, they
are all bags growing one against the other.

In the orange-pulp these cells contain only sweet juice, but in other
parts of the orange-tree or any other plant they contain a sticky
substance with little grains in it. This substance is called
"protoplasm," or the _first form_ of life, for it is alive and active,
and under a microscope you may see in a living plant streams of the
little grains moving about in the cells.

[Illustration: Fig. 39. Plant-cells.
_a_, round cells in pith of elder.
_b_, long cells in fibres of a plant.]

Now we are prepared to explain how our plant grows. Imagine the tiny
primrose plantlet to be made up of cells filled with active living
protoplasm, which drinks in starch and other food from the seed-leaves.
In this way each cell will grow too full for its skin, and then the
protoplasm divides into two parts and builds up a wall between them, and
so one cell becomes two. Each of these two cells again breaks up into
two more, and so the plant grows larger and larger, till by the time it
has used up all the food in the seed-leaves, it has sent roots covered
with fine hairs downwards into the earth, and a shoot with beginnings of
leaves up into the air.

Sometimes the seed-leaves themselves come above ground, as in the
mustard-plant, and sometimes they are left empty behind, while the
plantlet shoots through them.

And now the plant can no longer afford to be idle and live on prepared
food. It must work for itself. Until now it has been taking in the same
kind of food that you and I do; for we too find many seeds very pleasant
to eat and useful to nourish us. But now this store is exhausted. Upon
what then is the plant to live? It is cleverer than we are in this, for
while we cannot live unless we have food which has once been alive,
plants can feed upon gases and water and mineral matter only. Think over
the substances you can eat or drink, and you will find they are nearly
all made of things which have been alive: meat, vegetables, bread, beer,
wine, milk; all these are made from living matter, and though you do
take in such things as water and salt, and even iron and phosphorus,
these would be quite useless if you did not eat and drink prepared food
which your body can work up into living matter.

But the plant, as soon as it has roots and leaves, begins to make living
matter out of matter that has never been alive. Through all the little
hairs of its roots it sucks in water, and in this water are dissolved
more or less of the salts of ammonia, phosphorus, sulphur, iron, lime,
magnesia, and even silica, or flint. In all kinds of earth there is some
iron, and we shall see presently that this is very important to the
plant.

Suppose, then, that our primrose has begun to drink in water at its
roots. How is it to get this water up into the stem and leaves, seeing
that the whole plant is made of closed bags or cells? It does it in a
very curious way, which you can prove for yourselves. Whenever two
fluids, one thicker than the other, such as treacle and water for
example, are only separated by a skin or any porous substance, they will
always mix, the thinner one oozing through the skin into the thicker
one. If you tie a piece of bladder over a glass tube, half fill the tube
with treacle, and then let the covered end rest in a bottle of water, in
a few hours the water will get in to the treacle and the mixture will
rise up in the tube till it flows over the top. Now, the saps and juices
of plants are thicker than water, so, directly the water enters the
cells at the root it oozes up into the cells above, and mixes with the
sap. Then the matter in those cells becomes thinner than in the cells
above, so it too oozes up, and in this way cell by cell the water is
pumped up into the leaves.

When it gets there it finds our old friends the sunbeams hard at work.
If you have ever tried to grow a plant in a cellar, you will know that
in the dark its leaves remain white and sickly. It is only in the
sunlight that a beautiful delicate green tint is given to them, and you
will remember from Lecture II. that this green tint shows that the leaf
has used all the sun-waves except those which make you see green; but
why should it do this only when it has grown up in the sunshine?

The reason is this: when the sunbeam darts into the leaf and sets all
its particles quivering, it divides the protoplasm into two kinds,
collected into different cells. One of these remains white, but the
other kind, near the surface, is altered by the sunlight and by the help
of the iron brought in by the water. This particular kind of protoplasm,
which is called "chlorophyll," will have nothing to do with the green
waves and throws them back, so that every little grain of this
protoplasm looks green and gives the leaf its green colour.

It is these little green cells that by the help of the sun-waves digest
the food of the plant and turn the water and gases into useful sap and
juices. We saw in Lecture III. that when we breathe-in air, we use up
the oxygen in it and send back out of our mouths carbonic acid, which is
a gas made of oxygen and carbon.

Now, every living thing wants carbon to feed upon, but plants cannot
take it in by itself, because carbon is solid (the blacklead in your
pencils is pure carbon), and a plant cannot _eat_, it can only drink-in
fluids and gases. Here the little green cells help it out of its
difficulty. They take in or _absorb_ out of the air the carbonic acid
gas which we have given out of our mouths, and then by the help of the
sun-waves they tear the carbon and oxygen apart. Most of the oxygen they
throw back into the air for us to use, but the carbon they keep.

[Illustration: Fig. 40. Oxygen-bubbles rising from
  laurel-leaves in water.]

If you will take some fresh laurel-leaves and put them into a tumbler of
water turned upside-down in a saucer of water, and set the tumbler in
the sunshine, you will soon see little bright bubbles rising up and
clinging to the glass. These are bubbles of oxygen gas, and they tell
you that they have been set free by the green cells which have torn from
them the carbon of the carbonic acid in the water.

But what becomes of the carbon? And what use is made of the water which
we have kept waiting all this time in the leaves? Water, you already
know is made of hydrogen and oxygen; but perhaps you will be surprised
when I tell you that starch, sugar, and oil, which we get from plants,
are nothing more than hydrogen and oxygen in different quantities joined
to carbon.

[Illustration: Fig. 41. Carbon rising up from white sugar.]

It is very difficult at first to picture such a black thing as carbon
making part of delicate leaves and beautiful flowers, and still more of
pure white sugar. But we can make an experiment by which we can draw the
hydrogen and oxygen out of common loaf sugar, and then you will see the
carbon stand out in all its blackness. I have here a plate with a heap
of white sugar in it. I pour upon it first some hot water to melt and
warm it, and then some strong sulphuric acid. This acid does nothing
more than simply draw the hydrogen and oxygen out. See! in a few moments
a black mass of carbon begins to rise, all of which has come out of the
white sugar you saw just now.[15] You see, then, that from the whitest
substance in plants we can get this black carbon; and in truth, one-half
of the dry part of every plant is composed of it.

Now look at my plant again, and tell me if we have not already found a
curious history? Fancy that you see the water creeping in at the roots,
oozing up from cell to cell till it reaches the leaves, and there
meeting the carbon which has just come out of the air, and being worked
up with it by the sun-waves into starch, or sugar, or oils.

But meanwhile, how is new protoplasm to be formed? for without this
active substance none of the work can go on. Here comes into use a lazy
gas we spoke of in Lecture III. There we thought that nitrogen was of no
use except to float oxygen in the air, but here we shall find it very
useful. So far as we know, plants cannot take up nitrogen out of the
air, but they can get it out of the ammonia which the water brings in at
their roots.

Ammonia, you will remember, is a strong-smelling gas, made of hydrogen
and nitrogen, and which is often almost stifling near a manure-heap.
When you manure a plant you help it to get this ammonia, but at any time
it gets some from the soil and also from the rain-drops which bring it
down in the air. Out of this ammonia the plant takes the nitrogen and
works it up with the three elements, carbon, oxygen, and hydrogen, to
make the substances called albuminoids, which form a large part of the
food of the plant, and it is these albuminoids which go to make
protoplasm. You will notice that while the starch and other substances
are only made of three elements, the active protoplasm is made of these
three added to a fourth, nitrogen, and it also contains phosphorus and
sulphur.

And so hour after hour and day after day our primrose goes on pumping up
water and ammonia from its roots to its leaves, drinking in carbonic
acid from the air, and using the sun-waves to work them all up into food
to be sent to all parts of its body. In this way these leaves act, you
see, as the stomach of the plant, and digest its food.

[Illustration: Fig. 42. Stomates of a leaf.]

Sometimes more water is drawn up into the leaves than can be used, and
then the leaf opens thousands of little mouths in the skin of its under
surface, which let the drops out just as drops of perspiration ooze
through our skin when we are over-heated. These little mouths, which are
called stomates (_a_, Fig. 42) are made of two flattened cells, fitting
against each other. When the air is damp and the plant has too much
water these lie open and let it out, but when the air is dry, and the
plant wants to keep as much water as it can, then they are closely shut.
There are as many as a hundred thousand of these mouths under one
apple-leaf, so you may imagine how small they often are.

Plants which only live one year, such as mignonette, the sweet pea, and
the poppy, take in just enough food to supply their daily wants and to
make the seeds we shall speak of presently. Then, as soon as their seeds
are ripe their roots begin to shrivel, and water is no longer carried
up. The green cells can no longer get food to digest, and they
themselves are broken up by the sunbeams and turn yellow, and the plant
dies.

But many plants are more industrious than the stock and mignonette, and
lay by store for another year, and our primrose is one of these. Look at
this thick solid mass below the primrose leaves, out of which the roots
spring.[16] This is really the stem of the primrose hidden underground,
and all the starch, albuminoids, &c., which the plant can spare as it
grows, are sent down into this underground stem and stored up there, to
lie quietly in the ground through the long winter, and then when the
warm spring comes this stem begins to send out leaves for a new plant.

       *       *       *       *       *

We have now seen how a plant springs up, feeds itself, grows, stores up
food, withers, and dies; but we have said nothing yet about its
beautiful flowers or how it forms its seeds. If we look down close to
the bottom of the leaves in a primrose root in spring-time, we shall
always find three or four little green buds nestling in among the
leaves, and day by day we may see the stalk of these buds lengthening
till they reach up into the open sunshine, and then the flower opens and
shows its beautiful pale-yellow crown.

We all know that seeds are formed in the flower, and that the seeds are
necessary to grow into new plants. But do we know the history of how
they are formed, or what is the use of the different parts of the bud?
Let us examine them all, and then I think you will agree with me that
this is not the least wonderful part of the plant.

Remember that the seed is the one important thing, and then notice how
the flower protects it. First, look at the outside green covering, which
we call the _calyx_. See how closely it fits in the bud, so that no
insects can creep in to gnaw the flower, nor any harm come to it from
cold or blight. Then, when the calyx opens, notice that the yellow
leaves which form the crown or _corolla_, are each alternate with one of
the calyx leaves, so that anything which got past the first covering
would be stopped by the second. Lastly, when the delicate corolla has
opened out, look at those curious yellow bags just at the top of the
tube (2 _b_, Fig 43). What is their use?

[Illustration: Fig. 43. The two forms of the Primrose-flower.
_a_, Stigma or sticky head of the seed-vessel.
_b_, Anthers of the stamens.
_c_, Corolla or crown of the flower.
_d_, Calyx or outer covering.
_sv_, Seed-vessel.
_A_, Enlarged pistil, with pollen-grain resting on the stigma and
  growing down to the ovule.
_o_, Ovules.]

But I fancy I see two or three little questioning faces which seem to
say, "I see no yellow bags at the top of the tube." Well, I cannot tell
whether you can or not in the specimen you have in your hand; for one of
the most curious things about primrose flowers is, that some of them
have these yellow bags at the top of the tube and some of them hidden
down right in the middle. But this I can tell you: those of you who have
got no yellow bags at the top will have a round knob there (1 _a_, Fig.
43), and will find the yellow bags (_b_) buried in the tube. Those, on
the other hand, who have the yellow bags (2 _b_, Fig. 43) at the top
will find the knob (_a_) half-way down the tube.

Now for the use of these yellow bags, which are called the _anthers_ of
the stamens, the stalk on which they grow being called the _filament_ or
thread. If you can manage to split them open you will find that they
have a yellow powder in them, called _pollen_, the same as the powder
which sticks to your nose when you put it into a lily; and if you look
with a magnifying glass at the little green knob in the centre of the
flower you will probably see some of this yellow dust sticking on it (A,
Fig. 43). We will leave it there for a time, and examine the body called
the _pistil_, to which the knob belongs. Pull off the yellow corolla
(which will come off quite easily), and turn back the green leaves. You
will then see that the knob stands on the top of a column, and at the
bottom of this column there is a round ball (_s v_), which is a vessel
for holding the seeds. In this diagram (A, Fig. 43) I have drawn the
whole of this curious ball and column as if cut in half, so that we may
see what is in it. In the middle of the ball, in a cluster, there are a
number of round transparent little bodies, looking something like round
green orange-cells full of juice. They are really cells full of
protoplasm, with one little dark spot in each of them, which by-and-by
is to make our little plantlet that we found in the seed.

"These, then, are seeds," you will say. Not yet; they are only _ovules_,
or little bodies which may become seeds. If they were left as they are
they would all wither and die. But those little yellow grains of pollen,
which we saw sticking to the knob at the top, are coming down to help
them. As soon as these yellow grains touch the sticky knob or _stigma_,
as it is called, they throw out tubes, which grow down the column until
they reach the ovules. In each one of these they find a tiny hole, and
into this they creep, and then they pour into the ovule all the
protoplasm from the pollen-grain which is sticking above, and this
enables it to grow into a real seed with a tiny plantlet inside.

This is how the plant forms its seed to bring up new little ones next
year, while the leaves and the roots are at work preparing the necessary
food. Think sometimes when you walk in the woods, how hard at work the
little plants and big trees are, all around you. You breathe in the nice
fresh oxygen they have been throwing out, and little think that it is
they who are making the country so fresh and pleasant, and that while
they look as if they were doing nothing but enjoying the bright
sunshine, they are really fulfilling their part in the world by the help
of this sunshine; earning their food from the ground; working it up;
turning their leaves where they can best get light (and in this it is
chiefly the violet sun-waves that help them), growing, even at night, by
making new cells out of the food they have taken in the day; storing up
for the winter; putting out their flowers and making their seeds, and
all the while smiling so pleasantly in quiet nooks and sunny dells that
it makes us glad to see them.

But why should the primroses have such golden crowns? plain green ones
would protect the seed quite as well. Ah! now we come to a secret well
worth knowing. Look at the two primrose flowers, 1 and 2, Fig. 43, p.
163, and tell me how you think the dust gets on to the top of the sticky
knob or stigma. No. 2 seems easy enough to explain, for it looks as if
the pollen could fall down easily from the stamens on to the knob, but
it cannot fall _up_, as it would have to do in No. 1. Now the curious
truth is, as Mr. Darwin has shown, that neither of these flowers can get
the dust easily for themselves, but of the two No. 1 has the least
difficulty.

Look at a withered primrose, and see how it holds its head down, and
after a little while the yellow crown falls off. It is just about as it
is falling that the _anthers_ or bags of the stamens burst open, and
then, in No. 1 (Fig. 44), they are dragged over the knob and some of the
grains stick there. But in the other form of primrose, No. 2, when the
flower falls off, the stamens do not come near the knob, so it has no
chance of getting any pollen; and while the primrose is upright the tube
is so narrow that the dust does not easily fall. But, as I have said,
neither kind gets it very easily, nor is it good for them if they do.
The seeds are much stronger and better if the dust or pollen of one
flower is carried away and left on the knob or stigma of another flower;
and the only way this can be done is by insects flying from one flower
to another and carrying the dust on their legs and bodies.

[Illustration: Fig. 44. Corolla of Primrose falling off.
1, Primrose with long pistil, and stamens in the tube,
  same as 1 of Fig. 43.
2, Primrose with short pistil, and stamens at mouth of
  tube, 2, Fig. 43.]

If you suck the end of the tube of the primrose flower you will find it
tastes sweet, because a drop of honey has been lying there. When the
insects go in to get this honey, they brush themselves against the
yellow dust-bags, and some of the dust sticks to them, and then when
they go to the next flower they rub it off on to its sticky knob.

Look at No. 1 and No. 2 (Fig. 43) and you will see at once that if an
insect goes into No. 1 and the pollen sticks to him, when he goes into
No. 2 just that part of his body on which the pollen is will touch the
knob; and so the flowers become what we call "crossed," that is, the
pollen-dust of the one feeds the ovule of the other. And just the same
thing will happen if he flies from No. 2 to No. 1. There the dust will
be just in the position to touch the knob which sticks out of the
flower.

Therefore, we can see clearly that it is good for the primrose that bees
and other insects should come to it, and anything it can do to entice
them will be useful. Now, do you not think that when an insect once knew
that the pale-yellow crown showed where honey was to be found, he would
soon spy these crowns out as he flew along? or if they were behind a
hedge, and he could not see them, would not the sweet scent tell him
where to come and look for them? And so we see that the pretty
sweet-scented corolla is not only delightful for us to look at and to
smell, but it is really very useful in helping the primrose to make
strong healthy seeds out of which the young plants are to grow next
year.

       *       *       *       *       *

And now let us see what we have learnt. We began with a tiny seed,
though we did not then know how this seed had been made. We saw the
plantlet buried in it, and learnt how it fed at first on prepared food,
but soon began to make living matter for itself out of gases taken from
the water and the air. How ingeniously it pumped up the water through
the cells to its stomach--the leaves! And how marvellously the sun-waves
entering there formed the little green granules, and then helped them to
make food and living protoplasm! At this point we might have gone
further, and studied how the fibres and all the different vessels of the
plant are formed, and a wondrous history it would have been. But it was
too long for one hour's lecture, and you must read it for yourselves in
books on botany. We had to pass on to the flower, and learn the use of
the covering leaves, the gaily coloured crown attracting the insects,
the dust-bags holding the pollen, the little ovules each with the germ
of a new plantlet, lying hidden in the seed-vessel, waiting for the
pollen-grains to grow down to them. Lastly, when the pollen crept in at
the tiny opening we learnt that the ovule had now all it wanted to grow
into a perfect seed.

And so we came back to a primrose seed, the point from which we started;
and we have a history of our primrose from its birth to the day when its
leaves and flowers wither away and it dies down for the winter.

But what fairies are they which have been at work here? First, the busy
little fairy Life in the active protoplasm; and secondly, the sun-waves.
We have seen that it was by the help of the sunbeams that the green
granules were made, and the water, carbonic acid, and nitrogen worked up
into the living plant. And in doing this work the sun-waves were caught
and their strength used up, so that they could no longer quiver back
into space. But are they gone for ever? So long as the leaves or the
stem or the root of the plant remain they are gone, but when those are
destroyed we can get them back again. Take a handful of dry withered
plants and light them with a match, then as the leaves burn and are
turned back again to carbonic acid, nitrogen, and water, our sunbeams
come back again in the flame and heat.

And the life of the plant? What is it, and why is this protoplasm always
active and busy? I cannot tell you. Study as we may, the life of the
tiny plant is as much a mystery as your life and mine. It came, like all
things, from the bosom of the Great Father, but we cannot tell how it
came nor what it is. We can see the active grains moving under the
microscope, but we cannot see the power that moves them. We only know it
is a power given to the plant, as to you and to me, to enable it to live
its life, and to do its useful work in the world.

[Illustration]




LECTURE VIII.

THE HISTORY OF A PIECE OF COAL.

[Illustration]


I have here a piece of coal (Fig. 45), which, though it has been cut
with some care so as to have a smooth face, is really in no other way
different from any ordinary lump which you can pick for yourself out of
the coal-scuttle. Our work to-day is to relate the history of this black
lump; to learn what it is, what it has been, and what it will be.

[Illustration: Fig. 45. Piece of coal.
_a_, Smooth face, showing lamin or thin layers.]

It looks uninteresting enough at first sight, and yet if we examine it
closely we shall find some questions to ask even about its appearance.
Look at the smooth face of this specimen and see if you can explain
those fine lines which run across so close together as to look like the
edges of the leaves of a book. Try to break a piece of coal, and you
will find that it will split much more easily along those lines than
across the other way of the lump; and if you wish to light a fire
quickly you should always put this lined face downwards so that the heat
can force its way up through these cracks and gradually split up the
block. Then again if you break the coal carefully along one of these
lines you will find a fine film of charcoal lying in the crack, and you
will begin to suspect that this black coal must have been built up in
very thin layers, with a kind of black dust between them.

The next thing you will call to mind is that this coal burns and gives
flame and heat, and that this means that in some way sunbeams are
imprisoned in it; lastly, this will lead you to think of plants, and how
they work up the strength of the sunbeams into their leaves, and hide
black carbon in even the purest and whitest substance they contain.

Is coal made of burnt plants, then? Not burnt ones, for if so it would
not burn again; but you may have read how the makers of charcoal take
wood and bake it without letting it burn, and then it turns black and
will afterwards make a very good fire; and so you will see that it is
probable that our piece of coal is made of plants which have been baked
and altered, but which have still much sunbeam strength bottled up in
them, which can be set free as they burn.

If you will take an imaginary journey with me to a coal-pit near
Newcastle, which I visited many years ago, you will see that we have
very good evidence that coal is made of plants, for in all coal-mines we
find remains of them at every step we take.

[Illustration: Fig. 46. Imaginary section of a coal-mine.]

Let us imagine that we have put on old clothes which will not spoil, and
have stepped into the iron basket (see Fig. 46) called by the miners a
_cage_, and are being let down the shaft to the gallery where the miners
are at work. Most of them will probably be in the gallery _b_, because a
great deal of the coal in _a_ has been already taken out. But we will
stop in _a_ because there we can see a great deal of the roof and the
floor. When we land on the floor of the gallery we shall find ourselves
in a kind of tunnel with railway lines laid along it and trucks laden
with coal coming towards the cage to be drawn up, while empty ones are
running back to be loaded where the miners are at work. Taking lamps in
our hands and keeping out of the way of the trucks, we will first throw
the light on the roof, which is made of shale or hardened clay. We shall
not have gone many yards before we see impressions of plants in the
shale, like those in this specimen (Fig. 47), which was taken out of a
coal-mine at Neath in Glamorganshire, a few days ago, and sent up for
this lecture. You will recognize at once the marks of _ferns_ (_a_), for
they look like those you gather in the hedges of an ordinary country
lane, and that long striped branch (_b_) does not look unlike a reed,
and indeed it is something of this kind, as we shall see by-and-by. You
will find plenty of these impressions of plants as you go along the
gallery and look up at the roof, and with them there will be others with
spotted stems, or with stems having a curious diamond pattern upon them,
and many ferns of various kinds.

[Illustration: Fig. 47. A piece of shale with impressions of ferns
  and Calamite stems.]

[Illustration: Fig. 48. Stigmaria--root or underground stem
  of Sigillaria.]

Next look down at your feet and examine the floor. You will not have to
search long before you will almost certainly find a piece of stone like
that represented in Fig. 48, which has also come from Neath
Colliery.[17] This fossil, which is the cast of a piece of a plant,
puzzled those who found it for a very long time. At last, however, Mr.
Binney found the specimen growing to the bottom of the trunk of one of
the fossil trees with spotted stems, called _Sigillaria_; and so proved
that this curious pitted stone is a piece of fossil root, or rather
underground stem, like that which we found in the primrose, and that the
little pits or dents in it are scars where the rootlets once were given
off.

Whole masses of these root-stems, with ribbon-like roots lying scattered
near them, are found buried in the layer of clay called the _underclay_
which makes the floor of the coal, and they prove to us that this
underclay must have been once the ground in which the roots of the
coal-plants grew. You will feel still more sure of this when you find
that there is not only one straight gallery of coal, but that galleries
branch out right and left, and that everywhere you find the coal lying
like a sandwich between the floor and the roof, showing that quite a
large piece of country must be covered by these remains of plants all
rooted in the _underclay_.

But how about the coal itself? It seems likely, when we find roots below
and leaves and stems above, that the middle is made of plants, but can
we prove it? We shall see presently that it has been so crushed and
altered by being buried deep in the ground that the traces of leaves
have almost been destroyed, though people who are used to examining
with the microscope, can see the crushed remains of plants in thin
slices of coal.

But fortunately for us, perfect pieces of plants have been preserved
even in the coal-bed itself. Do you remember our learning in Lecture IV.
that water with lime in it petrifies things, that is, leaves carbonate
of lime to fill up grain by grain the fibres of an animal or plant as
the living matter decays, and so keeps an exact representation of the
object?

Now, it so happens that in a coal-bed at South Ouram, near Halifax, as
well as in some other places, carbonate of lime trickled in before the
plants were turned into coal, and made some round nodules in the
plant-bed, which look like cannon-balls. Afterwards, when all the rest
of the bed was turned into coal, these round balls remained
crystallized, and by cutting thin transparent slices across the nodule
we can distinctly see the leaves and stems and curious little round
bodies which make up the coal. Several such sections may be seen at the
British Museum, and when we compare these fragments of plants with those
which we find above and below the coal-bed, we find that they agree,
thus proving that coal is made of plants, and of those plants whose
roots grew in the clay floor, while their heads reached up far above
where the roof now is.

[Illustration: Fig. 49. Contents of a coal-ball. (Carruthers.)[18]
_S_, Stem of Sigillaria cut across.
_L_, Stem of Lepidodendron cut across.
_L'_, Stem of Lepidodendron cut lengthways.
_l_, cone of Lepidodendron (Lepidostrobus) cut across.
_C_, Stem of Calamite cut across.
_c, c, c_, Fruit of Calamite lengthways and across.
_f_, Stem of a fern with fragments of fern-leaves scattered round it.
  The small round dots scattered here and there are the larger spores
  which have fallen out of the fruit-cones.]

The next question is, what kind of plants were these? Have we anything
like them living in the world now? You might perhaps think that it would
be impossible to decide this question from mere petrified pieces of
plants. But many men have spent their whole lives in deciphering all
the fragments that could be found, and though the section given in Fig.
49 may look to you quite incomprehensible, yet a botanist can read it as
we read a book. For example, at S and L, where stems are cut across, he
can learn exactly how they were built up inside, and compare them with
the stems of living plants, while the fruits _c c_ and the little round
spores lying near them tell him their history as well as if he had
gathered them from the tree. In this way we have learnt to know very
fairly what the plants of the coal were like, and you will be surprised
when I tell you that the huge trees of the coal-forests, of which we
sometimes find trunks in the coal-mines from ten to fifty feet long, are
only represented on the earth now by small insignificant plants,
scarcely ever more than two feet, and often not many inches high.

[Illustration: Fig. 50. _Selaginella selaginoides._ Species of
  club-moss bearing two kinds of spores.]

Have you ever seen the little club-moss or Lycopodium which grows all
over England, but chiefly in the north, on heaths and mountains? At the
end of each of its branches it bears a cone made of scaly leaves; and
fixed to the inside of each of these leaves is a case called a
sporangium, full of little spores or moss-seeds, as we may call them,
though they are not exactly like true seeds. In one of these club-mosses
called _Selaginella_, the cases B near the bottom of the cone contain
large spores _b_, while those near the top A, contain a powdery dust
_a_. These spores are full of resin, and they are collected on the
Continent for making artificial lightning in the theatres, because they
flare when lighted.

Now this little Selaginella is of all living plants the one most like
some of the gigantic trees of the coal-forests. If you look at this
picture of a coal-forest (Fig. 51), you will find it difficult perhaps
to believe that those great trees, with diamond markings all up the
trunk, hanging over from the right to the left of the picture, and
covering all the top with their boughs, could be in any way relations of
the little Selaginella; yet we find branches of them in the beds above
the coal, bearing cones larger but just like Selaginella cones; and what
is most curious, the spores in these cones are of exactly the same kind
and not any larger than those of the club-moss.

These trees are called by botanists Lepidodendrons, or _scaly trees_;
there are numbers of them in all coal-mines, and one trunk has been
found 49 feet long. Their branches were divided in a curious forked
manner and bore cones at the ends. The spores which fell from these
cones are found flattened in the coal, and they may be seen scattered
about in the coal-ball (Fig. 49).

[Illustration: Fig. 51.--A FOREST OF THE COAL PERIOD.]

Another famous tree which grew in the coal-forests was the one whose
roots we found in the floor or _underclay_ of the coal. It has been
called Sigillaria, because it has marks like seals (_sigillum_, a seal)
all up the trunk, due to the scars left by the leaves when they fell
from the tree. You will see the Sigillarias on the left-hand side of the
coal-forest picture, having those curious tufts of leaves springing out
of them at the top. Their stems make up a great deal of the coal, and
the bark of their trunks is often found in the clays above, squeezed
flat in lengths of 30, 60, or 70 feet. Sometimes, instead of being flat
the bark is still in the shape of a trunk, and the interior is filled
with sand; and then the trunk is very heavy, and if the miners do not
prop the roof up well it falls down and kills those beneath it.
Stigmaria (Fig. 48, page 175) is the root of the Sigillaria, and is
found in the clays below the coal. Botanists are not yet quite certain
about the seed-cases of this tree, but Mr. Carruthers believes that they
grew inside the base of the leaves, as they do in the quillwort, a small
plant which grows at the bottom of our mountain lakes.

[Illustration: Fig. 52. Equisetum or horsetail.]

But what is that curious reed-like stem we found in the piece of shale
(see Fig. 47)? That stem is very important, for it belonged to a plant
called a _Calamite_, which, as we shall see presently, helped to sift
the earth away from the coal and keep it pure. This plant was a near
relation of the "horsetail," or Equisetum, which grows in our marshes;
only, just as in the case of the other trees, it was enormously larger,
being often 20 feet high, whereas the little Equisetum, Fig. 52, is
seldom more than a foot, and never more than 4 feet high in England,
though in tropical South America they are much higher. Still, if you
have ever gathered "horsetails," you will see at once that those trees
in the foreground of the picture (Fig. 51), with leaves arranged in
stars round the branches, are only larger copies of the little
marsh-plants; and the seed-vessels of the two plants are almost exactly
the same.

These great trees, the Lepidodendrons, the Sigillarias, and the
Calamites, together with large tree-ferns and smaller ferns, are the
chief plants that we know of in the coal-forests. It seems very strange
at first that they should have been so large when their descendants are
now so small, but if you look at our chief plants and trees now, you
will find that nearly all of them bear flowers, and this is a great
advantage to them, because it tempts the insects to bring them the
pollen-dust, as we saw in the last lecture.

Now the Lepidodendrons and their companions had no true flowers, but
only these seed-cases which we have mentioned; but as there were no
flowering plants in their time, and they had the ground all to
themselves, they grew fine and large. By-and-by, however, when the
flowering plants came in, these began to crowd out the old giants of the
coal-forests, so that they dwindled and dwindled from century to century
till their great-great-grandchildren, thousands of generations after,
only lift up their tiny heads in marshes and on heaths, and tell us that
they were big once upon a time.

And indeed they must have been magnificent in those olden days, when
they grew thick and tall in the lonely marshes where plants and trees
were the chief inhabitants. We find no traces in the clay-beds of the
coal to lead us to suppose that men lived in those days, nor lions, nor
tigers, nor even birds to fly among the trees; but these grand forests
were almost silent, except when a huge animal something like a gigantic
newt or frog went croaking through the marsh, or a kind of grasshopper
chirruped on the land. But these forms of life were few and far between,
compared to the huge trees and tangled masses of ferns and reeds which
covered the whole ground, or were reflected in the bosom of the large
pools and lakes round about which they grew.

       *       *       *       *       *

And now, if you have some idea of the plants and trees of the coal, it
is time to ask how these plants became buried in the earth and made pure
coal, instead of decaying away and leaving behind only a mixture of
earth and leaves?

To answer this question, I must ask you to take another journey with me
across the Atlantic to the shores of America, and to land at Norfolk in
Virginia, because there we can see a state of things something like the
marshes of the coal-forests. All round about Norfolk the land is low,
flat, and marshy, and to the south of the town, stretching far away into
North Carolina, is a large, desolate swamp, no less than forty miles
long and twenty-five broad. The whole place is one enormous quagmire,
overgrown with water-plants and trees. The soil is as black as ink from
the old, dead leaves, grasses, roots, and stems which lie in it; and so
soft, that everything would sink into it, if it were not for the matted
roots of the mosses, ferns, and other plants which bind it together. You
may dig down for ten or fifteen feet, and find nothing but peat made of
the remains of plants which have lived and died there in succession for
ages and ages, while the black trunks of the fallen trees lie here and
there, gradually being covered up by the dead plants.

The whole place is so still, gloomy, and desolate, that it goes by the
name of the "Great Dismal Swamp," and you see we have here what might
well be the beginning of a bed of coal; for we know that peat when dried
becomes firm and makes an excellent fire, and that if it were pressed
till it was hard and solid it would not be unlike coal. If, then, we can
explain how this peaty bed has been kept pure from earth, we shall be
able to understand how a coal-bed may have been formed, even though the
plants and trees which grow in this swamp are different from those which
grew in the coal-forests.

The explanation is not difficult; streams flow constantly, or rather
ooze into the Great Dismal Swamp from the land that lies to the west,
but instead of bringing mud in with them as rivers bring to the sea,
they bring only clear, pure water, because, as they filter for miles
through the dense jungle of reeds, ferns, and shrubs which grow round
the marsh, all the earth is sifted out and left behind. In this way the
spongy mass of dead plants remains free from earthy grains, while the
water and the shade of the thick forest of trees prevent the leaves,
stems, &c., from being decomposed by the air and sun. And so year after
year as the plants die they leave their remains for other plants to take
root in, and the peaty mass grows thicker and thicker, while tall cedar
trees and evergreens live and die in these vast, swampy forests, and
being in loose ground are easily blown down by the wind, and leave their
trunks to be covered up by the growing moss and weeds.

Now we know that there were plenty of ferns and of large Calamites
growing thickly together in the coal-forests, for we find their remains
everywhere in the clay, so we can easily picture to ourselves how the
dense jungle formed by these plants would fringe the coal-swamp, as the
present plants do the Great Dismal Swamp, and would keep out all earthy
matter, so that year after year the plants would die and form a thick
bed of peat, afterwards to become coal.

The next thing we have to account for is the bed of shale or hardened
clay covering over the coal. Now we know that from time to time land has
gone slowly up and down on our globe so as in some places to carry the
dry ground under the sea, and in others to raise the sea-bed above the
water. Let us suppose, then, that the great Dismal Swamp was gradually
to sink down so that the sea washed over it and killed the reeds and
shrubs. Then the streams from the west would not be sifted any longer
but would bring down mud, and leave it, as in the delta of the Nile or
Mississippi, to make a layer over the dead plants. You will easily
understand that this mud would have many pieces of dead trees and plants
in it, which were stifled and died as it covered them over; and thus
the remains would be preserved like those which we find now in the roof
of the coal-galleries.

But still there are the thick sandstones in the coal-mine to be
explained. How did they come there? To explain them, we must suppose
that the ground went on sinking till the sea covered the whole place
where once the swamp had been, and then sea-sand would be thrown down
over the clay and gradually pressed down by the weight of new sand
above, till it formed solid sandstone and our coal-bed became buried
deeper and deeper in the earth.

At last, after long ages, when the thick mass of sandstones above the
bed _b_ (Fig. 46, p. 174) had been laid down, the sinking must have
stopped and the land have risen a little, so that the sea was driven
back; and then the rivers would bring down earth again and make another
clay-bed. Then a new forest would spring up, the ferns, Calamites,
Lepidodendrons, and Sigillarias would gradually form another jungle, and
many hundreds of feet above the buried coal-bed _b_, a second bed of
peat and vegetable matter would begin to accumulate to form the coal-bed
_a_.

       *       *       *       *       *

Such is the history of how the coal which we now dig out of the depths
of the earth once grew as beautiful plants on the surface. We cannot
tell exactly all the ground over which these forests grew in England,
because some of the coal they made has been carried away since by rivers
and cut down by the waves of the sea, but we _can_ say that wherever
there is coal now, there they must have been.

Try and picture to yourselves that on the east coast of Northumberland
and Durham, where all is now black with coal-dust, and grimy with the
smoke of furnaces and where the noise of hammers and steam-engines, and
of carts and trucks hurrying to and fro, makes the country re-echo with
the sound of labour; there ages ago in the silent swamp shaded with
monster trees, one thin layer of plants after another was formed, year
after year, to become the coal we now value so much. In Lancashire, busy
Lancashire, the same thing was happening, and even in the middle of
Yorkshire and Derbyshire the sea must have come up and washed a silent
shore where a vast forest spread out over at least 700 or 800 square
miles. In Staffordshire, too, which is now almost the middle of England,
another small coal-field tells the same story, while in South Wales the
deep coal-mines and number of coal-seams remind us how for centuries and
centuries forests must have flourished and have disappeared over and
over again under the sand of the sea.

But what is it that has changed these beds of dead plants into hard,
stony coal? In the first place you must remember they have been pressed
down under an enormous weight of rocks above them. We can learn
something about this even from our common lead pencils. At one time the
_graphite_ or pure carbon, of which the blacklead (as we wrongly call
it) of our pencils is made, was dug solid out of the earth. But so much
has now been used that they are obliged to collect the graphite dust,
and press it under a heavy weight, and this makes such solid pieces that
they can cut them into leads for ordinary cedar pencils.

Now the pressure which we can exert by machinery is absolutely nothing
compared to the weight of all those hundreds of feet of solid rock which
lie over the coal-beds, and which has pressed them down for thousands
and perhaps millions of years; and besides this, we know that parts of
the inside of the earth are very hot, and many of the rocks in which
coal is found are altered by heat. So we can picture to ourselves that
the coal was not only squeezed into a solid mass, but often much of the
oil and gas which were in the leaves of the plants was driven out by
heat, and the whole baked, as it were, into one substance. The
difference between coal which flames and coal which burns only with a
red heat, is chiefly that one has been baked and crushed more than the
other. Coal which flames has still got in it the tar and the gas and the
oils which the plant stored up in its leaves, and these when they escape
again give back the sunbeams in a bright flame. The hard stone coal, on
the contrary, has lost a great part of these oils, and only carbon
remains, which seizes hold of the oxygen of the air and burns without
flame. Coke is pure carbon, which we make artificially by driving out
the oils and gases from coal, and the gas we burn is part of what is
driven out.

We can easily make coal-gas here in this room. I have brought a
tobacco-pipe, the bowl of which is filled with a little powdered coal,
and the broad end cemented up with common clay. When we place this bowl
over a spirit-lamp and make it very hot, the gas is driven out at the
narrow end of the pipe and lights easily (see Fig. 53). This is the way
all our gas is made, only that furnaces are used to bake the coal in,
and the gas is passed into large reservoirs till it is wanted for use.

[Illustration: Fig. 53.]

You will find it difficult at first to understand how coal can be so
full of oil and tar and gases, until you have tried to think over how
much of all these there is in plants, and especially in seeds--think of
the oils of almonds, of lavender, of cloves, and of caraways; and the
oils of turpentine which we get from the pines, and out of which tar is
made. When you remember these and many more, and also how the seeds of
the club-moss now are largely charged with oil, you will easily imagine
that the large masses of coal-plants which have been pressed together
and broken and crushed, would give out a great deal of oil which, when
made very hot, rises up as gas. You may often yourself see tar oozing
out of the lumps of coal in a fire, and making little black bubbles
which burst and burn. It is from this tar that James Young first made
the paraffin oil we burn in our lamps, and the spirit benzoline comes
from the same source.

From benzoline, again, we get a liquid called aniline, from which are
made so many of our beautiful dyes--mauve, magenta, and violet; and what
is still more curious, the bitter almonds, pear-drops, and many other
sweets which children like so well, are actually flavoured by essences
which come out of coal-tar. Thus from coal we get not only nearly all
our heat and our light, but beautiful colours and pleasant flavours. We
spoke just now of the plants of the coal as being without beautiful
flowers, and yet we see that long, long after their death they give us
lovely colours and tints as beautiful as any in flower-world now.

       *       *       *       *       *

Think, then, how much we owe to these plants which lived and died so
long ago! If they had been able to reason, perhaps they might have said
that they did not seem of much use in the world. They had no pretty
flowers, and there was no one to admire their beautiful green foliage
except a few croaking reptiles, and little crickets and grasshoppers;
and they lived and died all on one spot, generation after generation,
without seeming to do much good to anything or anybody. Then they were
covered up and put out of sight, and down in the dark earth they were
pressed all out of shape and lost their beauty and became only black,
hard coal. There they lay for centuries and centuries, and thousands and
thousands of years, and still no one seemed to want them.

At last, one day, long, long after man had been living on the earth, and
had been burning wood for fires, and so gradually using up the trees in
the forests, it was discovered that this black stone would burn, and
from that time coal has been becoming every day more and more useful.
Without it not only should we have been without warmth in our houses, or
light in our streets when the stock of forest-wood was used up; but we
could never have melted large quantities of iron-stone and extracted the
iron. We have proof of this in Sussex. The whole country is full of
iron-stone, and the railings of St. Paul's churchyard are made of Sussex
iron. Iron-foundries were at work there as long as there was wood enough
to supply them, but gradually the works fell into disuse, and the last
furnace was put out in the year 1809. So now, because there is no coal
in Sussex, the iron lies idle; while in the North, where the iron-stone
is near the coal-mines, hundreds of tons are melted out every day.

Again, without coal we could have had no engines of any kind, and
consequently no large manufactories of cotton goods, linen goods, or
cutlery. In fact, almost everything we use could only have been made
with difficulty and in small quantities; and even if we could have made
them it would have been impossible to have sent them so quickly all over
the world without coal, for we could have had no railways or steamships,
but must have carried all goods along canals, and by slow sailing
vessels. We ourselves must have taken days to perform journeys now made
in a few hours, and months to reach our colonies.

In consequence of this we should have remained a very poor people.
Without manufactories and industries we should have had to live chiefly
by tilling the ground, and everyone being obliged to toil for their
daily bread, there would have been much less time or opportunity for
anyone to study science, or literature, or history, or to provide
themselves with comforts and refinements of life.

All this then, those plants and trees of the far-off ages, which seemed
to lead such useless lives, have done and are doing for us. There are
many people in the world who complain that life is dull, that they do
not see the use of it, and that there seems no work specially for them
to do. I would advise such people, whether they are grown up or little
children, to read the story of the plants which form the coal. These saw
no results during their own short existences, they only lived and
enjoyed the bright sunshine, and did their work, and were content. And
now thousands, probably millions, of years after they lived and died,
England owes her greatness, and we much of our happiness and comfort, to
the sunbeams which those plants wove into their lives.

They burst forth again in our fires, in our brilliant lights, and in our
engines, and do the greater part of our work; teaching us

    "That nothing walks with aimless feet,
      That not one life shall be destroyed,
      Or cast as rubbish to the void,
    When God hath made the pile complete."

                         _In Memoriam_, liv.

[Illustration]




LECTURE IX.

BEES IN THE HIVE.


[Illustration]

I am going to ask you to visit with me to-day one of the most wonderful
cities in the world. It is a city with no human beings in it, and yet it
is densely populated, for such a city may contain from twenty thousand
to sixty thousand inhabitants. In it you will find streets, but no
pavements, for the inhabitants walk along the walls of the houses;
while in the houses you will see no windows, for each house just fits
its owner, and the door is the only opening in it. Though made without
hands these houses are most evenly and regularly built in tiers one
above the other; and here and there a few royal palaces, larger and more
spacious than the rest, catch the eye conspicuously as they stand out at
the corners of the streets.

Some of the ordinary houses are used to live in, while others serve as
storehouses where food is laid up in the summer to feed the inhabitants
during the winter, when they are not allowed to go outside the walls.
Not that the gates are ever shut: that is not necessary, for in this
wonderful city each citizen follows the laws; going out when it is time
to go out, coming home at proper hours, and staying at home when it is
his or her duty. And in the winter, when it is very cold outside, the
inhabitants, having no fires, keep themselves warm within the city by
clustering together, and never venturing out of doors.

One single queen reigns over the whole of this numerous population, and
you might perhaps fancy that, having so many subjects to work for her
and wait upon her, she would do nothing but amuse herself. On the
contrary, she too obeys the laws laid down for her guidance, and never,
except on one or two state occasions, goes out of the city, but works as
hard as the rest in performing her own royal duties.

From sunrise to sunset, whenever the weather is fine, all is life,
activity, and bustle in this busy city. Though the gates are so narrow
that two inhabitants can only just pass each other on their way through
them, yet thousands go in and out every hour of the day; some bringing
in materials to build new houses, others food and provisions to store up
for the winter; and while all appears confusion and disorder among this
rapidly moving throng, yet in reality each has her own work to do, and
perfect order reigns over the whole.

Even if you did not already know from the title of the lecture what city
this is that I am describing, you would no doubt guess that it is a
beehive. For where in the whole world, except indeed upon an anthill,
can we find so busy, so industrious, or so orderly a community as among
the bees? More than a hundred years ago, a blind naturalist, Franois
Huber, set himself to study the habits of these wonderful insects, and
with the help of his wife and an intelligent man-servant managed to
learn most of their secrets. Before his time all naturalists had failed
in watching bees, because if they put them in hives with glass windows,
the bees, not liking the light, closed up the windows with cement before
they began to work. But Huber invented a hive which he could open and
close at will, putting a glass hive inside it, and by this means he was
able to surprise the bees at their work. Thanks to his studies, and to
those of other naturalists who have followed in his steps, we now know
almost as much about the home of bees as we do about our own; and if we
follow out to-day the building of a bee-city and the life of its
inhabitants, I think you will acknowledge that they are a wonderful
community, and that it is a great compliment to anyone to say that he
or she is "as busy as a bee."

       *       *       *       *       *

In order to begin at the beginning of the story, let us suppose that we
go into a country garden one fine morning in May when the sun is shining
brightly overhead, and that we see hanging from the bough of an old
apple-tree a black object which looks very much like a large
plum-pudding. On approaching it, however, we see that it is a large
cluster or swarm of bees clinging to each other by their legs; each bee
with its two fore-legs clinging to the two hinder legs of the one above
it In this way as many as 20,000 bees may be clinging together, and yet
they hang so freely that a bee, even from quite the centre of the swarm,
can disengage herself from her neighbours and pass through to the
outside of the cluster whenever she wishes.

If these bees were left to themselves, they would find a home after a
time in a hollow tree, or under the roof of a house, or in some other
cavity, and begin to build their honeycomb there. But as we do not wish
to lose their honey we will bring a hive, and, holding it under the
swarm, shake the bough gently so that the bees fall into it, and cling
to the sides as we turn it over on a piece of clean linen, on the stand
where the hive is to be.

And now let us suppose that we are able to watch what is going on in the
hive. Before five minutes are over the industrious little insects have
begun to disperse and to make arrangements in their new home A number
(perhaps about two thousand) of large, lumbering bees of a darker
colour than the rest, will, it is true, wander aimlessly about the hive,
and wait for the others to feed them and house them; but these are the
drones, or male bees (3, Fig. 54), who never do any work except during
one or two days in their whole lives. But the smaller working bees (1,
Fig. 54) begin to be busy at once. Some fly off in search of honey.
Others walk carefully all round the inside of the hive to see if there
are any cracks in it; and if there are, they go off to the
horse-chestnut trees, poplars, hollyhocks, or other plants which have
sticky buds, and gather a kind of gum called "propolis," with which they
cement the cracks and make them air-tight. Others again, cluster round
one bee (2, Fig. 54) blacker than the rest and having a longer body and
shorter wings; for this is the queen-bee, the mother of the hive, and
she must be watched and tended.

[Illustration: Fig. 54.
1. Worker bee.
2. Queen-bee.
3. Drone or male bee.]

But the largest number begin to hang in a cluster from the roof just as
they did from the bough of the apple tree. What are they doing there?
Watch for a little while and you will soon see one bee come out from
among its companions and settle on the top of the inside of the hive,
turning herself round and round, so as to push the other bees back, and
to make a space in which she can work. Then she will begin to pick at
the under part of her body with her fore-legs, and will bring a scale of
wax from a curious sort of pocket under her abdomen. Holding this wax in
her claws, she will bite it with her hard, pointed upper jaws, which
move to and fro sideways like a pair of pincers, then, moistening it
with her tongue into a kind of paste, she will draw it out like a ribbon
and plaster it on the top of the hive.

[Illustration: Fig. 55. Plate of wax with bases of cells,
  hanging from the bar of a hive.]

After that she will take another piece; for she has eight of these
little wax-pockets, and she will go on till they are all exhausted. Then
she will fly away out of the hive, leaving a small wax lump on the hive
ceiling or on the bar stretched across it; then her place will be taken
by another bee who will go through the same manoeuvres. This bee will
be followed by another, and another, till a large wall of wax has been
built, hanging from the bar of the hive as in Fig. 55, only that it will
not yet have cells fashioned in it.

Meanwhile the bees which have been gathering honey out of doors begin to
come back laden. But they cannot store their honey, for there are no
cells made yet to put it in; neither can they build combs with the
rest, for they have no wax in their wax-pockets. So they just go and
hang quietly on to the other bees, and there they remain for twenty-four
hours, during which time they digest the honey they have gathered, and
part of it forms wax and oozes out from the scales under their body.
Then they are prepared to join the others at work and plaster wax on to
the hive.

And now, as soon as a rough lump of wax is ready, another set of bees
come to do their work. These are called the _nursing bees_, because they
prepare the cells and feed the young ones. One of these bees, standing
on the roof of the hive, begins to force her head into the wax, biting
with her jaws and moving her head to and fro. Soon she has made the
beginning of a round hollow, and then she passes on to make another,
while a second bee takes her place and enlarges the first one. As many
as twenty bees will be employed in this way, one after another, upon
each hole before it is large enough for the base of a cell.

Meanwhile another set of nursing bees have been working just in the same
way on the other side of the wax, and so a series of hollows are made
back to back all over the comb. Then the bees form the walls of the
cells, and soon a number of six-sided tubes, about half an inch deep,
stand all along each side of the comb ready to receive honey or
bee-eggs.

You can see the shape of these cells in _c_, _d_, Fig. 56, and notice
how closely they fit into each other. Even the ends are so shaped that,
as they lie back to back, the bottom of one cell (B, Fig. 56) fits into
the space between the ends of three cells meeting it from the opposite
side (A, Fig. 56), while they fit into the spaces around it. Upon this
plan the clever little bees fill every atom of space, use the least
possible quantity of wax, and make the cells lie so closely together
that the whole comb is kept warm when the young bees are in it.

[Illustration: Fig. 56.
B shows in the centre the closed end of a cell which would fit into
  the space in the centre of the three closed cells in A, while the
  ends of these three would fit into the spaces in B.
_c_, _d_, side-view of cells.]

There are some kinds of bees who do not live in hives, but each one
builds a home of its own. These bees--such as the upholsterer bee, which
digs a hole in the earth and lines it with flowers and leaves, and the
mason bee, which builds in walls--do not make six-sided cells, but round
ones, for room is no object to them. But nature has gradually taught the
little hive-bee to build its cells more and more closely, till they fit
perfectly within each other. If you make a number of round holes close
together in a soft substance, and then squeeze the substance evenly from
all sides, the rounds will gradually take a six-sided form, showing that
this is the closest shape into which they can be compressed. Although
the bee does not know this, yet as she gnaws away every bit of wax that
can be spared she brings the holes into this shape.

As soon as one comb is finished, the bees begin another by the side of
it, leaving a narrow lane between, just broad enough for two bees to
pass back to back as they crawl along, and so the work goes on till the
hive is full of combs.

As soon, however, as a length of about five or six inches of the first
comb has been made into cells, the bees which are bringing home honey no
longer hang to make it into wax, but begin to store it in the cells. We
all know where the bees go to fetch their honey, and how, when a bee
settles on a flower, she thrusts into it her small tongue-like
proboscis, which is really a lengthened under-lip, and sucks out the
drop of honey. This she swallows, passing it down her throat into a
honey-bag or first stomach, which lies between her throat and her real
stomach, and when she gets back to the hive she can empty this bag and
pass the honey back through her mouth again into the honey-cells.

But if you watch bees carefully, especially in the spring-time, you will
find that they carry off something else besides honey. Early in the
morning, when the dew is on the ground, or later in the day, in moist,
shady places, you may see a bee rubbing itself against a flower, or
biting those bags of yellow dust or pollen which we mentioned in Lecture
VII. When she has covered herself with pollen, she will brush it off
with her feet, and, bringing it to her mouth, she will moisten and roll
it into a little ball, and then pass it back from the first pair of legs
to the second and so to the third or hinder pair. Here she will pack it
into a little hairy groove called a "basket" in the joint of one of the
hind legs, where you may see it, looking like a swelled joint, as she
hovers among the flowers. She often fills both hind legs in this way,
and when she arrives back at the hive the nursing bees take the lumps
from her, and eat it themselves, or mix it with honey to feed the young
bees; or, when they have any to spare, store it away in old honey-cells
to be used by-and-by. This is the dark, bitter stuff called "bee-bread"
which you often find in a honeycomb, especially in a comb which has been
filled late in the summer.

When the bee has been relieved of the bee-bread she goes off to one of
the clean cells in the new comb, and, standing on the edge, throws up
the honey from the honey-bag into the cell. One cell will hold the
contents of many honey-bags, and so the busy little workers have to work
all day filling cell after cell, in which the honey lies uncovered,
being too thick and sticky to flow out, and is used for daily
food--unless there is any to spare, and then they close up the cells
with wax to keep for the winter.

       *       *       *       *       *

Meanwhile, a day or two after the bees have settled in the hive, the
queen-bee begins to get very restless. She goes outside the hive and
hovers about a little while, and then comes in again, and though
generally the bees all look very closely after her to keep her indoors,
yet now they let her do as she likes. Again she goes out, and again
back, and then, at last, she soars up into the air and flies away. But
she is not allowed to go alone. All the drones of the hive rise up
after her, forming a guard of honour to follow her wherever she goes.

In about half-an-hour she comes back again, and then the working bees
all gather round her, knowing that now she will remain quietly in the
hive and spend all her time in laying eggs: for it is the queen-bee who
lays all the eggs in the hive. This she begins to do about two days
after her flight. There are now many cells ready besides those filled
with honey: and, escorted by several bees, the queen-bee goes to one of
these, and, putting her head into it, remains there a second as if she
were examining whether it would make a good home for the young bee.
Then, coming out, she turns round and lays a small, oval, bluish-white
egg in the cell. After this she takes no more notice of it, but goes on
to the next cell and the next, doing the same thing, and laying eggs in
all the empty cells equally on both sides of the comb. She goes on so
quickly that she sometimes lays as many as 200 eggs in one day.

Then the work of the nursing bees begins. In two or three days each egg
has become a tiny maggot or larva, and the nursing bees put into its
cell a mixture of pollen and honey which they have prepared in their own
mouths, thus making a kind of sweet bath in which the larva lies. In
five or six days the larva grows so fat upon this that it nearly fills
the cell, and then the bees seal up the mouth of the cell with a thin
cover of wax, made of little rings and with a tiny hole in the centre.

As soon as the larva is covered in, it begins to give out from its
under-lip a whitish, silken film, made of two threads of silk glued
together, and with this it spins a covering or cocoon all round itself,
and so it remains for about ten days more. At last, just twenty-one days
after the egg was laid, the young bee is quite perfect, lying in the
cell as in Fig. 57, and she begins to eat her way through the cocoon and
through the waxen lid, and scrambles out of her cell. Then the nurses
come again to her, stroke her wings and feed her for twenty-four hours,
and after that she is quite ready to begin work, and flies out to gather
honey and pollen like the rest of the workers.

[Illustration: Fig. 57.
Brood-comb cut open, with the pup, or young bees, _p_, _p_,
in the cells.
The lower cells contain eggs, afterwards to become bees, _q_,
a royal cell.]

By this time the number of working bees in the hive is becoming very
great, and the storing of honey and pollen-dust goes on very quickly.
Even the empty cells which the young bees have left are cleaned out by
the nurses and filled with honey; and this honey is darker than that
stored in clean cells, and which we always call "virgin honey" because
it is so pure and clear.

At last, after six weeks, the queen leaves off laying worker-eggs, and
begins to lay, in some rather larger cells, eggs from which drones, or
male bees, will grow up in about twenty days. Meanwhile the worker-bees
have been building on the edge of the cones some very curious cells
(_q_, Fig. 57) which look like thimbles hanging with the open side
upwards, and about every three days the queen stops in laying drone-eggs
and goes to put an egg in _one_ of these cells. Notice that she waits
three days between each of these peculiar layings, because we shall see
presently that there is a good reason for her doing so.

The nursing bees take great care of these eggs, and instead of putting
ordinary food into the cell, they fill it with a sweet, pungent jelly,
for this larva is to become a princess and a future queen-bee. Curiously
enough, it seems to be the peculiar food and the size of the cell which
makes the larva grow into a mother-bee which can lay eggs, for if a hive
has the misfortune to lose its queen, they take one of the ordinary
worker-larv and put it into a royal cell and feed it with jelly, and it
becomes a queen-bee. As soon as the princess is shut in like the others,
she begins to spin her cocoon, but she does not quite close it as the
other bees do, but leaves a hole at the top.

At the end of sixteen days after the first royal egg was laid, the
eldest princess begins to try to eat her way out of her cell, and about
this time the old queen becomes very uneasy, and wanders about
distractedly. The reason of this is, that there can never be two
queen-bees in one hive, and the queen knows that her daughter will soon
be coming out of her cradle and will try to turn her off her throne. So,
not wishing to have to fight for her kingdom, she makes up her mind to
seek a new home and take a number of her subjects with her. If you
watch the hive about this time you will notice many of the bees
clustering together after they have brought in their honey, and hanging
patiently, in order to have plenty of wax ready to use when they start,
while the queen keeps a sharp look-out for a bright, sunny day, on which
they can swarm: for bees will never swarm on a wet or doubtful day if
they can possibly help it, and we can easily understand why, when we
consider how the rain would clog their wings and spoil the wax under
their bodies.

Meanwhile the young princess grows very impatient, and tries to get out
of her cell, but the worker-bees drive her back, for they know there
would be a terrible fight if the two queens met. So they close up the
hole she has made with fresh wax after having put in some food for her
to live upon till she is released.

At last a suitable day arrives, and about ten or eleven o'clock in the
morning the old queen leaves the hive, taking with her about 2000 drones
and from 12,000 to 20,000 worker-bees, which fly a little way clustering
round her till she alights on the bough of some tree, and then they form
a compact swarm ready for a new hive or to find a home of their own.

Leaving them to go their way, we will now return to the old hive. Here
the liberated princess is reigning in all her glory; the worker-bees
crowd round her, watch over her, and feed her as though they could not
do enough to show her honour. But still she is not happy. She is
restless, and runs about as if looking for an enemy, and she tries to
get at the remaining royal cells where the other young princesses are
still shut in. But the workers will not let her touch them, and at last
she stands still and begins to beat the air with her wings and to
tremble all over, moving more and more quickly, till she makes quite a
loud, piping noise.

Hark! What is that note answering her? It is a low, hoarse sound, and it
comes from the cell of the next eldest princess. Now we see why the
young queen has been so restless. She knows her sister will soon come
out, and the louder and stronger the sound becomes within the cell, the
sooner she knows the fight will have to begin. And so she makes up her
mind to follow her mother's example and to lead off a second swarm. But
she cannot always stop to choose a fine day, for her sister is growing
very strong and may come out of her cell before she is off. And so the
second, or _after swarm_, gets ready and goes away. And this explains
why princesses' eggs are laid a few days apart, for if they were laid
all on the same day, there would be no time for one princess to go off
with a swarm before the other came out of her cell. Sometimes, when the
workers are not watchful enough, two queens do meet, and then they fight
till one is killed; or sometimes they both go off with the same swarm
without finding each other out. But this only delays the fight till they
get into the new hive; sooner or later one must be killed.

And now a third queen begins to reign in the old hive, and she is just
as restless as the preceding ones, for there are still more princesses
to be born. But this time, if no new swarm wants to start, the workers
do not try to protect the royal cells. The young queen darts at the
first she sees, gnaws a hole with her jaws, and, thrusting in her sting
through the hole in the cocoon, kills the young bee while it is still a
prisoner. She then goes to the next, and the next, and never rests till
all the young princesses are destroyed. Then she is contented, for she
knows no other queen will come to dethrone her. After a few days she
takes her flight in the air with the drones, and comes home to settle
down in the hive for the winter.

Then a very curious scene takes place. The drones are no more use, for
the queen will not fly out again, and these idle bees will never do any
work in the hive. So the worker-bees begin to kill them, falling upon
them, and stinging them to death, and as the drones have no stings they
cannot defend themselves, and in a few days there is not a drone, nor
even a drone-egg, left in the hive. This massacre seems very sad to us,
since the poor drones have never done any harm beyond being hopelessly
idle. But it is less sad when we know that they could not live many
weeks, even if they were not attacked, and, with winter coming, the bees
cannot afford to feed useless mouths, so a quick death is probably
happier for them than starvation.

       *       *       *       *       *

And now all the remaining inhabitants of the hive settle down to feeding
the young bees and laying in the winter's store. It is at this time,
after they have been toiling and saving, that we come and take their
honey; and from a well-stocked hive we may even take 30 lbs. without
starving the industrious little inhabitants. But then we must often feed
them in return, and give them sweet syrup in the late autumn and the
next early spring when they cannot find any flowers.

Although the hive has now become comparatively quiet and the work goes
on without excitement, yet every single bee is employed in some way,
either out of doors or about the hive. Besides the honey collectors and
the nurses, a certain number of bees are told off to ventilate the hive.
You will easily understand that where so many insects are packed closely
together the heat will become very great, and the air impure and
unwholesome. And the bees have no windows that they can open to let in
fresh air, so they are obliged to fan it in from the one opening of the
hive. The way in which they do this is very interesting. Some of the
bees stand close to the entrance, with their faces towards it, and
opening their wings, so as to make them into fans, they wave them to and
fro, producing a current of air. Behind these bees, and all over the
floor of the hive, there stand others, this time with their backs
towards the entrance, and fan in the same manner, and in this way air is
sent into all the passages.

Another set of bees clean out the cells after the young bees are born,
and make them fit to receive honey, while others guard the entrance of
the hive to keep away the destructive wax-moth, which tries to lay its
eggs in the comb so that its young ones may feed on the honey. All
industrious people have to guard their property against thieves and
vagabonds, and the bees have many intruders, such as wasps and snails
and slugs, which creep in whenever they get a chance. If they succeed in
escaping the sentinel bees, then a fight takes place within the hive,
and the invader is stung to death.

Sometimes, however, after they have killed the enemy, the bees cannot
get rid of his body, for a snail or slug is too heavy to be easily
moved, and yet it would make the hive very unhealthy to allow it to
remain. In this dilemma the ingenious little bees fetch the gummy
"propolis" from the plant-buds and cement the intruder all over, thus
embalming his body and preventing it from decaying.

And so the life of this wonderful city goes on. Building, harvesting,
storing, nursing, ventilating and cleaning from morn till night, the
little worker-bee lives for about eight months, and in that time has
done quite her share of work in the world. Only the young bees, born
late in the season, live on till the next year to work in the spring.
The queen-bee lives longer, probably about two years, and then she too
dies, after having had a family of many thousands of children.

We have already pointed out that in our fairy-land of nature all things
work together so as to bring order out of apparent confusion. But though
we should naturally expect winds and currents, rivers and clouds, and
even plants to follow fixed laws, we should scarcely have looked for
such regularity in the life of the active, independent busy bee. Yet we
see that she, too, has her own appointed work to do, and does it
regularly and in an orderly manner. In this lecture we have been
speaking entirely of the bee within the hive, and noticing how
marvellously her instincts guide her in her daily life. But within the
last few years we have learnt that she performs a most curious and
wonderful work in the world outside her home, and that we owe to her not
only the sweet honey we eat, but even in a great degree the beauty and
gay colours of the flowers which she visits when collecting it. This
work will form the subject of our next lecture, and while we love the
little bee for her constant industry, patience, and order within the
hive, we shall, I think, marvel at the wonderful law of nature which
guides her in her unconscious mission of love among the flowers which
grow around it.

[Illustration]




LECTURE X.

BEES AND FLOWERS.

[Illustration]


Whatever thoughts each one of you may have brought to the lecture
to-day, I want you to throw them all aside and fancy yourself to be in a
pretty country garden on a hot summer's morning. Perhaps you have been
walking, or reading, or playing, but it is getting too hot now to do
anything; and so you have chosen the shadiest nook under the old
walnut-tree, close to the flower-bed on the lawn, and would almost like
to go to sleep if it were not too early in the day.

As you lie there thinking of nothing in particular, except how pleasant
it is to be idle now and then, you notice a gentle buzzing close to
you, and you see that on the flower-bed close by, several bees are
working busily among the flowers. They do not seem to mind the heat, nor
to wish to rest; and they fly so lightly and look so happy over their
work that it does not tire you to look at them.

That great humble-bee takes it leisurely enough as she goes lumbering
along, poking her head into the larkspurs, and remaining so long in each
you might almost think she had fallen asleep. The brown hive-bee, on the
other hand, moves busily and quickly among the stocks, sweet peas, and
mignonette. She is evidently out on active duty, and means to get all
she can from each flower, so as to carry a good load back to the hive.
In some blossoms she does not stay a moment, but draws her head back
directly she has popped it in, as if to say, "No honey there." But over
the full blossoms she lingers a little, and then scrambles out again
with her drop of honey, and goes off to seek more in the next flower.

Let us watch her a little more closely. There are plenty of different
plants growing in the flower-bed, but, curiously enough, she does not go
first to one kind and then to another; but keeps to one, perhaps the
mignonette, the whole time, till she flies away. Rouse yourself up to
follow her, and you will see she takes her way back to the hive. She
may perhaps stop to visit a stray plant of mignonette on her way, but no
other flower will tempt her till she has taken her load home.

Then when she comes back again she may perhaps go to another kind of
flower, such as the sweet peas, for instance, and keep to them during
the next journey, but it is more likely that she will be true to her old
friend the mignonette for the whole day.

We all know why she makes so many journeys between the garden and the
hive, and that she is collecting drops of honey from each flower, and
carrying it to be stored up in the honeycomb for winter's food. How she
stores it, and how she also gathers pollen-dust for her bee-bread, we
saw in the last lecture; to-day we will follow her in her work among the
flowers, and see, while they are so useful to her, what she is doing for
them in return.

We have already learnt from the life of a primrose that plants can make
better and stronger seeds when they can get pollen-dust from another
plant, than when they are obliged to use that which grows in the same
flower; but I am sure you will be very much surprised to hear that the
more we study flowers the more we find that their colours, their scent,
and their curious shapes are all so many baits and traps set by nature
to entice insects to come to the flowers, and carry this pollen-dust
from one to the other.

So far as we know, it is entirely for this purpose that the plants form
honey in different parts of the flower, sometimes in little bags or
glands, as in the petals of the buttercup flower, sometimes in clear
drops, as in the tube of the honeysuckle. This food they prepare for the
insects, and then they have all sorts of contrivances to entice them to
come and fetch it.

You will remember that the plants of the coal had no bright or
conspicuous flowers. Now we can understand why this was, for there were
no flying insects at that time to carry the pollen-dust from flower to
flower, and therefore there was no need of coloured flowers to attract
them. But little by little, as flies, butterflies, moths and bees began
to live in the world, flowers too began to appear, and plants hung out
these gay-coloured signs, as much as to say, "Come to me, and I will
give you honey if you will bring me pollen-dust in exchange, so that my
seeds may grow healthy and strong."

We cannot stop to inquire to-day how this all gradually came about, and
how the flowers gradually put on gay colours and curious shapes to tempt
the insects to visit them; but we will learn something about the way
they attract them now, and how you may see it for yourselves if you keep
your eyes open.

For example, if you watch the different kinds of grasses, sedges and
rushes, which have such tiny flowers that you can scarcely see them, you
will find that no insects visit them. Neither will you ever find bees
buzzing round oak-trees, nut-trees, willows, elms or birches. But on the
pretty and sweet-smelling apple-blossoms, or the strongly scented
lime-trees, you will find bees, wasps, and plenty of other insects.

The reason of this is that grasses, sedges, rushes, nut-trees, willows,
and the others we have mentioned, have all of them a great deal of
pollen-dust, and as the wind blows them to and fro, it wafts the dust
from one flower to another, and so these plants do not want the insects,
and it is not worth their while to give out honey, or to have gaudy or
sweet-scented flowers to attract them.

But wherever you see bright or conspicuous flowers you may be quite sure
that the plants want the bees or some other winged insect to come and
carry their pollen for them. Snowdrops hanging their white heads among
their green leaves, crocuses with their violet and yellow flowers, the
gaudy poppy, the large-flowered hollyhock or the sunflower, the
flaunting dandelion, the pretty pink willow-herb, the clustered blossoms
of the mustard and turnip flowers, the bright blue forget-me-not and the
delicate little yellow trefoil, all these are visited by insects, which
easily catch sight of them as they pass by and hasten to sip their
honey.

Sir John Lubbock has shown that bees are not only attracted by bright
colours, but that they even know one colour from another. He put some
honey on slips of glass with coloured papers under them, and when he had
accustomed the bees to find the honey always on the blue glass, he
washed this glass clean, and put the honey on the red glass instead. Now
if the bees had followed only the smell of the honey, they would have
flown to the red glass, but they did not. They went first to the blue
glass, expecting to find the honey on the usual colour, and it was only
when they were disappointed that they went off to the red.

Is it not beautiful to think that the bright pleasant colours we love so
much in flowers, are not only ornamental, but that they are useful and
doing their part in keeping up healthy life in our world?

Neither must we forget what sweet scents can do. Have you never noticed
the delicious smell which comes from beds of mignonette, thyme,
rosemary, mint, or sweet alyssum, from the small hidden bunches of
laurustinus blossom, or from the tiny flowers of the privet? These
plants have found another way of attracting the insects; they have no
need of bright colours, for their scent is quite as true and certain a
guide. You will be surprised if you once begin to count them up, how
many white and dull or dark-looking flowers are sweet-scented, while
gaudy flowers, such as the tulip, foxglove and hollyhock, have little or
no scent. And then, just as in the world we find some people who have
everything to attract others to them, beauty and gentleness, cleverness,
kindliness, and loving sympathy, so we find some flowers, like the
beautiful lily, the lovely rose, and the delicate hyacinth, which have
colour and scent and graceful shapes all combined.

But we are not yet nearly at an end of the contrivances of flowers to
secure the visits of insects. Have you not observed that different
flowers open and close at different times? The daisy receives its name
_day's eye_, because it opens at sunrise and closes at sunset, while
the evening primrose (_OEnothera biennis_) and the night campion
(_Silene noctiflora_) spread out their flowers just as the daisy is
going to bed.

What do you think is the reason of this? If you go near a bed of evening
primroses just when the sun is setting, you will soon be able to guess,
for they will then give out such a sweet scent that you will not doubt
for a moment that they are calling the evening moths to come and visit
them. The daisy opens by day, because it is visited by day insects, but
those particular moths which can carry the pollen-dust of the evening
primrose, fly only by night, and if this flower opened by day other
insects might steal its honey, while they would not be the right size or
shape to touch its pollen-bags and carry the dust.

It is the same if you pass by a honeysuckle in the evening; you will be
surprised how much stronger its scent is than in the daytime. This is
because the sphinx hawk-moth is the favourite visitor of that flower,
and comes at nightfall, guided by the strong scent, to suck out the
honey with its long proboscis, and carry the pollen-dust.

Again, some flowers close whenever rain is coming. The pimpernel
(_Anagallis arvensis_) is one of these, hence its name of the
"Shepherd's Weather-glass." This little flower closes, no doubt, to
prevent its pollen-dust being washed away, for it has no honey; while
other flowers do it to protect the drop of honey at the bottom of their
corolla. Look at the daisies for example when a storm is coming on; as
the sky grows dark and heavy, you will see them shrink up and close till
the sun shines again. They do this because in each of the little yellow
florets in the centre of the flower there is a drop of honey which would
be quite spoiled if it were washed by the rain.

And now you will see why cup-shaped flowers so often droop their
heads--think of the harebell, the snowdrop, the lily-of-the-valley, the
campanula, and a host of others; how pretty they look with their bells
hanging so modestly from the slender stalk! They are bending down to
protect the honey-glands within them, for if the cup became full of rain
or dew the honey would be useless, and the insects would cease to visit
them.

But it is not only necessary that the flowers should keep their honey
for the insects, they also have to take care and keep it for the right
kind of insect. Ants are in many cases great enemies to them, for they
like honey as much as bees and butterflies do, yet you will easily see
that they are so small that if they creep into a flower they pass the
anthers without rubbing against them, and so take the honey without
doing any good to the plant. Therefore we find numberless contrivances
for keeping the ants and other creeping insects away. Look for example
at the hairy stalk of the primrose flower; those little hairs are like a
forest to a tiny ant, and they protect the flower from his visits. The
Spanish catchfly (_Silene otites_), on the other hand, has a smooth, but
very gummy stem, and on this the insects stick, if they try to climb.
Slugs and snails too will often attack and bite flowers, unless they are
kept away by thorns and bristles, such as we find on the teazel and the
burdock. And so we are gradually learning that everything which a plant
does has its meaning, if we can only find it out, and that even every
insignificant hair has its own proper use, and when we are once aware of
this a flower-garden may become quite a new world to us if we open our
eyes to all that is going on in it.

       *       *       *       *       *

But as we cannot wander among many plants to-day, let us take a few
which the bees visit, and see how they contrive not to give up their
honey without getting help in return. We will start with the blue
wood-geranium, because from it we first began to learn the use of
insects to flowers.

More than a hundred years ago a young German botanist, Christian Conrad
Sprengel, noticed some soft hairs growing in the centre of this flower,
just round the stamens, and he was so sure that every part of a plant is
useful, that he set himself to find out what these hairs meant. He soon
discovered that they protected some small honey-bags at the base of the
stamens, and kept the rain from washing the honey away, just as our
eyebrows prevent the perspiration on our faces from running into our
eyes. This led him to notice that plants take great care to keep their
honey for insects, and by degrees he proved that they did this in order
to tempt the insects to visit them and carry off their pollen.

The first thing to notice in this little geranium flower is that the
purple lines which ornament it all point directly to the place where the
honey lies at the bottom of the stamens, and actually serve to lead the
bee to the honey; and this is true of the veins and marking of nearly
all flowers except of those which open by night, _and in these they
would be useless for the insects would not see them_.

[Illustration: Fig. 58. _Geranium sylvaticum_, the Wood Geranium.
In the left-hand flower the stamens are all lying down. In the middle
  flower five stamens clasp the stigma. In the right-hand flower the
  stigma is open after all the stamens have fallen.]

When the geranium first opens, all its ten stamens are lying flat on the
corolla or coloured crown, as in the left-hand flower in Fig. 58, and
then the bee cannot get at the honey. But in a short time five stamens
begin to raise themselves and cling round the stigma or knob at the top
of the seed-vessel, as in the middle flower. Now you would think they
would leave their dust there. But no! the stigma is closed up so tight
that the dust cannot get on to the sticky part. Now, however, the bee
_can_ get at the honey-glands on the outside of the raised stamens; and
as he sucks it, his back touches the anthers or dust-bags, and he
carries off the pollen. Then, as soon as all their dust is gone, these
five stamens fall down, and the other five spring up. Still, however,
the stigma remains closed, and the pollen of these stamens, too, may be
carried away to another flower. At last these five also fall down, and
then, and not till then, the stigma opens and lays out its five sticky
points, as you may see in the right-hand flower, Fig. 58.

But its own pollen is all gone, how then will it get any? It will get it
from some bee who has just taken it from another and younger flower; and
thus you see the blossom is _prevented_ from using its own pollen, and
made to use that of another blossom, so that its seeds may grow healthy
and strong.

The garden nasturtium, into whose blossom we saw the humble-bee poking
his head, takes still more care of its pollen-dust. It hides its honey
down at the end of its long spur, and only sends out one stamen at a
time instead of five like the geranium; and then, when all the stamens
have had their turn, the sticky knob comes out last for pollen from
another flower.

All this you may see for yourselves if you find geraniums[19] in the
hedges, and nasturtiums in your garden. But even if you have not these,
you may learn the history of another flower quite as curious, and which
you can find in any field or lane even near London. The common
dead-nettle (Fig. 59) takes a great deal of trouble in order that the
bee may carry off its pollen. When you have found one of these plants,
take a flower from the ring all round the stalk and tear it gently open,
so that you can see down its throat. There, just at the very bottom, you
will find a thick fringe of hairs (_f_, No. 2, Fig. 59), and you will
guess at once that these are to protect a drop of honey below. Little
insects which would creep into the flower and rob it of its honey
without touching the anthers of the stamens (_a_, Fig. 59) cannot get
past these hairs, and so the drop is kept till the bee comes to fetch
it.

[Illustration: Fig. 59. Flower of the Dead-Nettle (_Lamium album_).
1, Whole.
2, Cut in half.
_f_, Fringe of hairs protecting honey at base.
_s_, Stigma.
_a_, Anthers of stamens.
_l_, Lip of flower.]

Now look for the stamens: there are four of them (_a a_), two long and
two short, and they are quite hidden under the hood which forms the top
of the flower. How will the bee touch them? If you were to watch one,
you would find that when the bee alights on the broad lip _l_, and
thrusts her head down the tube, she first of all knocks her back against
the little forked tip _s_. This is the sticky stigma, and she leaves
there any dust she has brought from another flower; then, as she must
push far in to reach the honey, she rubs the top of her back against the
anthers _a a_, and before she comes out again has carried away the
yellow powder on her back, ready to give it to the next flower.

Do you remember how we noticed at the beginning of the lecture that a
bee always likes to visit the same kind of plant in one journey? You see
now that this is very useful to the flowers. If the bee went from a
dead-nettle to a geranium, the dust would be lost, for it would be of no
use to any other plant but a dead-nettle. But since the bee likes to get
the same kind of honey each journey, she goes to the same kind of
flowers, and places the pollen-dust just where it is wanted.

There is another flower, called the Salvia, which belongs to the same
family as our dead-nettle, and I think you will agree with me that its
way of dusting the bee's back is most clever. The Salvia (Fig. 60) is
shaped just like the dead-nettle, with a hood and a broad lip, but
instead of four stamens it has only two, the other two being shrivelled
up. The two that are left have a very strange shape, for the stalk or
_filament_ of the stamen (1 _f_) is very short, while the anther, which
is in most flowers two little bags stuck together, has here grown out
into a long thread _a b_, with a little dust-bag at one end only. In 1,
Fig. 60, you only see one of these stems, because the flower is cut in
half, but in the whole flower, one stands on each side just within the
lip. Now, when the bee puts her head into the tube to reach the honey,
she passes right between these two swinging anthers, and knocking
against the end _b_ pushes it before her and so brings the dust-bag _a_
plump down on her back, scattering the dust there! You can easily try
this by thrusting a pencil into any Salvia flower, and you will see the
anther fall.

[Illustration: Fig. 60. Flower of the Salvia.
1. Half a flower, showing the filament _f_, the swinging anther _a b_,
  _b' a'_, and the stigma _s_.
2. Bee entering the flower pushes the anther so that it takes the
  position _a' b'_, No. 1, and hits him on the back.
3. Older flower: stigma touching the bee.]

You will notice that all this time the bee does not touch the sticky
stigma which hangs high above her; but after the anthers are empty and
shrivelled the stalk of the stigma grows longer, and it falls lower
down. By-and-by another bee, having pollen on her back, comes to look
for honey, and as she goes into No. 3, she rubs against the stigma and
leaves upon it the dust from another flower.

Tell me, has not the Salvia, while remaining so much the same shape as
the dead-nettle, devised a wonderful contrivance to make use of the
visits of the bee?

The common sweet violet (_Viola odorata_) or the dog violet (_Viola
canina_), which you can gather in any meadow, give up their pollen-dust
in quite a different way from the Salvia, and yet it is equally
ingenious. Everyone has noticed what an irregular shape this flower has,
and that one of its purple petals has a curious spur sticking out
behind. In the tip of this spur and in the spur of the stamen lying in
it the violet hides its honey, and to reach it the bee must press past
the curious ring of orange-tipped bodies in the middle of the flower.
These bodies are the anthers _a a_, Fig. 61, which fit tightly round the
stigma _s_, so that when the pollen-dust _p_, which is very dry, comes
out of the bags, it remains shut in by the tips as if in a box. Two of
these stamens have spurs which lie in the coloured spur of the flower,
and have honey at the end of them. Now, when the bee shakes the end of
the stigma _s_, it parts the ring of anthers, and the fine dust falls
through upon the insect.

[Illustration: Fig. 61. Section of the Dog Violet. Lubbock.
A, Anthers and stigma enlarged.
_a a_, Anthers.
_s_, Stigma.
_p_, Pollen.
_h_, Honey.]

Let us see for a moment how wonderfully this flower is arranged to bring
about the carrying of the pollen, as Sprengel pointed out years ago. In
the first place, it hangs on a thin stalk, and bends its head down so
that the rain cannot come near the honey in the spur, and also so that
the pollen-dust falls forward into the front of the little box made by
the closed anthers. Then the pollen is quite dry, instead of being
sticky as in most plants. This is in order that it may fall easily
through the cracks. Then the _style_ or stalk of the stigma is very thin
and its tip very broad, so that it quivers easily when the bee touches
it, and so shakes the anthers apart, while the anthers themselves fold
over to make the box, and yet not so tightly but that the dust can fall
through when they are shaken. Lastly, if you look at the veins of the
lower, you will find that they all point towards the spur where the
honey is to be found, so that when the sweet smell of the flower has
brought the bee, she cannot fail to go in at the right place.

Two more flowers still I want us to examine together, and then I hope
you will care to look at every flower you meet, to try and see what
insects visit it, and how its pollen-dust is carried. These two flowers
are the common Bird's-foot trefoil (_Lotus corniculatus_), and the Early
Orchis (_Orchis mascula_), which you may find in almost any moist meadow
in the spring and early summer.

The Bird's-foot trefoil, Fig. 62, you will find almost anywhere all
through the summer, and you will know it from other flowers very like it
by its leaf, which is not a true trefoil, for behind the three usual
leaflets of the clover and the shamrock leaf, it has two small leaflets
near the stalk. The flower, you will notice, is shaped very like the
flower of a pea, and indeed it belongs to the same family, called the
_Papilionace_ or butterfly family, because the flowers look something
like an insect flying.

In all these flowers the top petal (_sta_, Fig. 62) stands up like a
flag to catch the eye of the insect, and for this reason botanists call
it the "standard." Below it are two side-petals _w_ called the "wings,"
and if you pick these off you will find that the remaining two petals
_k_ are joined together at the tip in a shape like the keel of a boat
(2, Fig. 62). For this reason they are called the "keel." Notice as we
pass that these two last petals have in them a curious little hollow or
depression _d_, and if you look inside the "wings" you will notice a
little knob that fits into this hollow, and so locks the two together.
We shall see by-and-by that this is important.

[Illustration: Fig. 62. _Lotus corniculatus_, Bird's-foot Trefoil.
1. Full flower:
_sta_, Standard;
_w_, Wings;
_k_, Keel.
2. Keel of flower:
_d_, Depression into which wings fit.
3. Interior of flower:
_s_, Stigma;
_p_, Pollen;
_a_, Anthers;
_h_, Place where honey lies.]

Next let us look at the half-flower when it is cut open, and see what
there is inside. There are ten stamens in all, enclosed with the stigma
in the keel; nine are joined together and one is by itself. The anthers
of five of these stamens burst open while the flower is still a bud, but
the other stamens go on growing, and push the pollen-dust, which is very
moist and sticky, right up into the tip of the keel. Here you see it
lies right round the stigma _s_, but as we saw before in the geranium,
the stigma is not ripe and sticky yet, and so it does not use the
pollen-grains.

Now suppose that a bee comes to the flower. The honey she has to fetch
lies inside the tube at _h_, and the one stamen being loose she is able
to get her proboscis in. But if she is to be of any use to the flower
she must uncover the pollen-dust. See how cunningly the flower has
contrived this. In order to put her head into the tube the bee must
stand upon the wings _w_, and her weight bends them down. But they are
locked to the keel _k_ by the knob fitting in the hole _d_, and so the
keel is pushed down too, and the sticky pollen-dust is uncovered and
comes right against the stomach of the bee and sticks there! As soon as
she has done feeding and flies away, up go the wings and the keel with
them, covering up any pollen that remains ready for next time. Then when
the bee goes to another flower, as she touches the stigma as well as the
pollen, she leaves some of the foreign dust upon it, and the flower uses
that rather than its own, because it is better for its seeds. If however
no bee happens to come to one of these flowers, after a time the stigma
becomes sticky and it uses its own pollen: and this is perhaps one
reason why the bird's-foot trefoil is so very common, because it can do
its own work if the bee does not help it.

Now we come lastly to the Orchis flower. Mr. Darwin has written a whole
book on the many curious and wonderful ways in which orchids tempt bees
and other insects to fertilize them. We can only take the simplest, but
I think you will say that even this blossom is more like a conjuror's
box than you would have supposed it possible that a flower could be.

[Illustration: Fig. 63. _Orchis mascula._
_c c c_, Calyx.
_co_, _co_, _co_, Corolla.
_p_, Pollen-masses.
_r_, Rostellum or lid covering the knob at the end of pollen-masses.
_s s_, Stigmas.
P, a Pollinia or pollen-mass, of which _a_ is the pollen and
  _d_ the sticky gland which adheres to the head of the bee.
_sv_, Seed-vessel.
_sp_, Spur of the flower.]

Let us examine it closely. It has six deep-red covering leaves, three _c
c c_, Fig. 63. belonging to the calyx or outer cup, and three _co_,
_co_, _co_, belonging to the corolla or crown of the flower; but all six
are coloured alike, except that the large one in front, called the
"lip," has spots and lines upon it which will suggest to you at once
that they point to the honey.

But where are the anthers, and where is the stigma? Look just under the
arch made by those three bending flower-leaves, and there you will see
two small slits, and in these some little club-shaped bodies _p p_,
which you can pick out with the point of a needle. One of these enlarged
is shown at P. It is composed of sticky grains of pollen _a_ held
together by fine threads on the top of a thin stalk; and at the bottom
of the stalk there is a little round body _d_. This is all that you will
find to represent the stamens of the flower. When these masses of
pollen, or _pollinia_ as they are called, are within the flower, the
knob at the bottom is covered by a little lid _r_, shutting them in like
the lid of a box, and just below this lid _r_ you will see two yellowish
lumps _s s_, which are very sticky. These are the top of the stigma, and
they are just above the seed-vessel _sv_, which you can see in the
lowest flower in the picture.

Now let us see how this flower gives up its pollen. When a bee comes to
look for honey in the orchis, she alights on the lip, and guided by the
lines makes straight for the opening just in front of the stigmas _s s_.
Putting her head into this opening she pushes down into the spur _sp_,
where by biting the inside skin she gets some juicy sap. Notice that she
has to bite, which takes time.

You will see at once that she must touch the stigmas in going in, and so
give them any pollen she has on her head. But she also touches the
little lid _r_ and it _flies instantly open, bringing the glands d at
the end of the pollen-masses against her head_. These glands are moist
and sticky, and while she is gnawing the inside of the spur they dry a
little and cling to her head and she brings them out with her. Darwin
once caught a bee with as many as sixteen of these pollen-masses
clinging to her head.

But if the bee went into the next flower with these pollinia sticking
upright, she would simply put them into the same slits in the next
flower, she would not touch them against the stigma. Nature, however,
has provided against this. As the bee flies along, the glands sticking
to its head dry more and more, and as they dry they curl up and drag the
pollen-masses down, so that instead of standing upright, as in 1, Fig.
63, they point forwards, as in 2.

And now, when the bee goes into the next flower, she will thrust them
right against the sticky stigmas, and as they cling there the fine
threads which hold the grains together break away, and the flower is
fertilized.

If you will gather some of these orchids during your next spring walk in
the woods, and will put a pencil down the tube to represent the head of
the bee, you may see the little box open, and the two pollen-masses
cling to the pencil. Then if you draw it out you may see them gradually
bend forwards, and by thrusting your pencil into the next flower you may
see the grains of pollen break away, and you will have followed out the
work of the bee.

       *       *       *       *       *

Do not such wonderful contrivances as these make us long to know and
understand all the hidden work that is going on around us among the
flowers, the insects, and all forms of life? I have been able to tell
you but very little, but I can promise you that the more you examine,
the more you will find marvellous histories such as these in simple
field-flowers.

Long as we have known how useful honey was to the bee, and how it could
only get it from flowers, yet it was not till quite lately that we have
learned to follow out Sprengel's suggestion, and to trace the use which
the bee is to the flower. But now that we have once had our eyes opened,
every flower teaches us something new, and we find that each plant
adapts itself in a most wonderful way to the insects which visit it,
both so as to provide them with honey, and at the same time to make them
unconsciously do it good service.

And so we learn that even among insects and flowers, those who do most
for others, receive most in return. The bee and the flower do not either
of them reason about the matter, they only go on living their little
lives as nature guides them, helping and improving each other. Think for
a moment how it would be, if a plant used up all its sap for its own
life, and did not give up any to make the drop of honey in its flower.
The bees would soon find out that these particular flowers were not
worth visiting, and the flower would not get its pollen-dust carried,
and would have to do its own work and grow weakly and small. Or suppose
on the other hand that the bee bit a hole in the bottom of the flower,
and so got at the honey, as indeed they sometimes do; then she would
not carry the pollen-dust, and so would not keep up the healthy strong
flowers which make her daily food.

But this, as you see, is not the rule. On the contrary, the flower feeds
the bee, and the bee quite unconsciously helps the flower to make its
healthy seed. Nay more; when you are able to read all that has been
written on this subject, you will find that we have good reason to think
that the flowerless plants of the Coal Period have gradually put on the
beautiful colours, sweet scent, and graceful shapes of our present
flowers, in consequence of the necessity of attracting insects, and thus
we owe our lovely flowers to the mutual kindliness of plants and
insects.

And is there nothing beyond this? Surely there is. Flowers and insects,
as we have seen, act without thought or knowledge of what they are
doing; but the law of mutual help which guides them is the same which
bids you and me be kind and good to all those around us, if we would
lead useful and happy lives. And when we see that the Great Power which
rules over our universe makes each work for the good of all, even in
such humble things as bees and flowers; and that beauty and loveliness
come out of the struggle and striving of all living things; then, if our
own life be sometimes difficult, and the struggle hard to bear, we learn
from the flowers that the best way to meet our troubles is to lay up our
little drop of honey for others, sure that when they come to sip it they
will, even if unconsciously, give us new vigour and courage in return.

       *       *       *       *       *

And now we have arrived at the end of those subjects which we selected
out of the Fairy-land of Science. You must not for a moment imagine,
however, that we have in any way exhausted our fairy domain; on the
contrary, we have scarcely explored even the outskirts of it. The
"History of a Grain of Salt," "A Butterfly's Life," or "The Labours of
an Ant," would introduce us to fairies and wonders quite as interesting
as those of which we have spoken in these Lectures. While "A Flash of
Lightning," "An Explosion in a Coal-mine," or "The Eruption of a
Volcano," would bring us into the presence of terrible giants known and
dreaded from time immemorial.

But at least we have passed through the gates, and have learnt that
there is a world of wonder which we may visit if we will; and that it
lies quite close to us, hidden in every dewdrop and gust of wind, in
every brook and valley, in every little plant or animal. We have only to
stretch out our hand and touch them with the wand of inquiry, and they
will answer us and reveal the fairy forces which guide and govern them;
and thus pleasant and happy thoughts may be conjured up at any time,
wherever we find ourselves, by simply calling upon nature's fairies and
asking them to speak to us. Is it not strange, then, that people should
pass them by so often without a thought, and be content to grow up
ignorant of all the wonderful powers ever active in the world around
them?

Neither is it pleasure alone which we gain by a study of nature. We
cannot examine even a tiny sunbeam, and picture the minute waves of
which it is composed, travelling incessantly from the sun, without
being filled with wonder and awe at the marvellous activity and power
displayed in the infinitely small as well as in the infinitely great
things of the universe. We cannot become familiar with the facts of
gravitation, cohesion, or crystallization, without realizing that the
laws of nature are fixed, orderly, and constant, and will repay us with
failure or success according as we act ignorantly or wisely; and thus we
shall begin to be afraid of leading careless, useless, and idle lives.
We cannot watch the working of the fairy "life" in the primrose or the
bee, without learning that living beings as well as inanimate things are
governed by these same laws of nature; nor can we contemplate the mutual
adaptation of bees and flowers without acknowledging that it teaches the
truth that those succeed best in life who, whether consciously or
unconsciously, do their best for others.

And so our wanderings in the Fairy-land of Science will have given us
much pleasant knowledge, and taught us in many ways how to regulate our
own lives, while they may also serve a far higher purpose, by showing us
that the forces of nature, whether they are apparently mechanical, as in
gravitation or heat, or intelligent, as in living beings, are one and
all the voice of the Great Creator, and speak to us of His Nature and
His Will.

[Illustration]




INDEX.


ADELSBERG STALACTITE GROTTO, 116

Aerial ocean, 51, 70

Agassiz on "erratic blocks," 122

Air, bad, in close rooms, 54

---- carrying water-vapour, 74, 78, 93

---- elasticity of, 57

---- its pressure on the earth, 60

---- made of two gases, 52

---- rising of hot, 68

---- weight of, 58

Air-atoms forming waves of sound, 130

Air-bubbles bursting in waves, 143

Air-currents, cause of, 67

Albuminoids, 154, 160

Almond-seed, 153

Alum Bay Chine, 109

Ammonia in air, 55

Anaxagoras on size of the son, 29

Antarctic Continent, snow-fields of, 93

Anthers of stamens, 164

---- bursting of, 166

Aqueous vapour, whence it comes, 77

Arbroath, waste of cliffs at, 117

Ariel's song, 5

Atmosphere causing the spread of light, 71

Atmosphere, height of, 59

---- weight of, 60-66

Aurora borealis, 52, 71

Avalanche, noise of, 147


BALLOON ASCENTS, 58

Balls illustrating sound-waves, 129

Barometer and its action, 64-66

Bee-bread, 202

Bee, pollen-masses on head of, 233

Bees and flowers useful to each other, 235

---- and orchids, 231

---- cementing dead bodies, 210

---- feeding of, 203, 205

---- Huber on, 195

---- length of life of, 210

---- nursing, 199

---- sentinel, 209

---- swarming, 196, 206, 207

---- ventilating, 209

---- visit one set of flowers at a time, 214, 224

---- worker, queen, and drone, 197

---- young princess, 205

Beetles, timber-boring, 148

Biot, Professor, on sound in tubes, 132

Bird's-foot trefoil, structure of, 229

Birds, trill of, 148

Bischof, on lime in River Rhine, 106

Blackgang Chine, 109

Bones of the ear, 138

Bonn, solid matter carried past, 106

Breathing and burning, 54

Brood-comb of bees, 204

Brook, song of the, 143

Burning and breathing, 54

Buttercup, honey-glands in, 215

Buxton, Poole's Cavern, near, 115


CALAMITES OF THE COAL, 181

Calyx, use of, 163

Caons of Colorado, 111

Carbon in plants, 158

---- in sugar, 159

Carbonate of lime crystals, 115

Carbonic acid in air, 55

Cardboard of colours, revolving, 41

Carruthers, Mr., cited, 178, 181

Caverns, stalactitic, 115

Caves on seashore, 118

Cells of a plant, 154

---- of bees, 200

Chalk-builders, 4, 97

Chemical action, 12, 16, 53

---- rays, 48

Chlorophyll in leaves, 158

Cissy and the drops, 14

City of the bees, 193

Clerk-Maxwell on ether, 35

Clouds, how formed, 75, 78

Club-moss and coal-plants, 179

Coal, a piece of, 172

---- essences from, 190

---- imprisoned fairies in, 11

---- its growth and purity, 183-185

---- oils, tar, and gas of, 189

---- -ball, contents of a, 178

---- -fields of England, 187

---- -forest, picture of a, 180

---- -gas, making of, 188

---- -mine, section of a, 174

Coal-plants, what they have done for us, 190

Cobwebs and dew-drops, 84

Cochlea of ear, 139

Cocoon of bees, 203, 205

Cohesion and its work, 8, 12, 80

Coke, 188

Colorado caons, 111

Colour, bees distinguish, 216

Colours, cause of, 44

---- revolving disk of, 41

Coral, Huxley on, 21

---- picture of, 20

---- -island, 23

Corolla, use of, 166

Corti's organ, 140

Country, sounds of the, 126

Crevasses, 120

Crystallization, 87, 89

---- a fairy force, 10

Crystals in sugar-candy, 86

---- how they form, 89

---- in many substances, 87

---- of sea-salts, 96

---- of snow, 89

Cumberland, rain in, 81


DAISY, opening of the, 217

---- closing in rain, 218

Darwin, Mr., cited, 231-233

Dead-nettle, structure of the, 223

Deltas, 114

Deposition of mud, 113

Dew, how formed, 83

---- artificial, 84

Distillation of water from seas, 92

Drones, slaughter of, 208


EAR, construction of the, 136

---- stones, 139

Earth, its size compared to the sun, 29

Earth-pillars, picture of, 102

Earth's state if there were no sun, 28

Echoes, 133, 144

Eggs, laying of queen-bee, 205

Enemies of bees, 209

---- of plants, 219

Equisetum, or horsetail, 181

Erratic blocks, 122

Ether, waves of the, 35, 82

Eustachian tube, 137

Evaporation from rivers and seas, 77

Evening primrose, insects visiting, 218

Eye, light-waves entering, 38-41


FAIRIES, or forces of nature, 6-12

Fairy "Life," 169

Fairy-tales and science, 2

Flowers bright to attract insects, 216

---- times of opening of, 217

Food of a plant, 156

Frost bursting water-pipes, 91

---- breaking up the fields, 118


GANGES DELTA, 114

Gas, definition of a, 15

---- in coal, 188

Gay-Lussac's balloon ascent, 58

Geikie, Mr., cited, 117

Geneva, mud in lake of, 121

Geranium, fertilization of, 220

---- sylvaticum, 221

---- of the garden, 222

Glacial Period, 122

Glaciers, 94, 119

---- blocks carried by, 122

Glaisher's balloon ascent, 58, 62

God in nature, 25

Graphite, hardened by pressure, 187

Grass, dew forming on, 83

Gravesend, mud-banks at, 114

Gravitation and its work, 8, 12

Great Dismal Swamp, America, 183

Greenland, glaciers of, 119

---- snow-fields of, 93

---- vapour carried from, 79

Gulf of Mexico, vapour carried up from, 78


HAILSTONES, how formed, 85

Hard water, 95

Hartshorn, spirits of, 55

Heat, a fairy force, 8

---- cut off by water-vapour, 82

---- necessary to turn water into vapour, 92

---- of the sun, 32

---- work done by, 45

---- imprisoned in coal, 46

---- of our bodies, 46

Helpfulness, mutual, of insects and flowers, 235

Herschel, Sir J., on the sun, 32

Hive-bee, forming cells, 200

Hives, ventilation of, 209

---- bees cementing cracks in, 197

Hoar-frost, 90

Honey, carried by bee, 201

---- secreted by flowers for bees, 215

---- use of, to the primrose, 167

Honeysuckle, scent at night, 218

Hooker, Sir J., on rainfall, 80

Horse-tails and calamites, 181

Huber on bees, 195

Huxley, Mr., on coral, 21

---- cited, 104

Huyghens on light, 34


ICE, formed of pressed snow, 93

---- purity of, 95

---- sculpturing power of, 119

---- water-flowers in, 91

Icebergs, 94

Imagination in science, 7

Indian Ocean, vapour carried up from, 77

Insects attracted by scent and colour, 217

---- buzzing of, 147

---- visiting the primrose, 167

Iron, use of in leaves, 157

---- worked in Sussex, 191

Ives, Lieut., on Caons, 112


JAR, resonance in a, 145

Judd, Professor, cited, 176


KENTUCKY, Mammoth Cave of, 116

Kettle, crust in a, 105

---- vapour rising from a, 75

Khasia Hills, rain in, 80


LACE, photographed during lecture, 48

Lake-district, rain in the, 81

Land-breeze and sea-breeze, 69

Landslips, 103

Lamium album, 223

Larva of bees, 203

Laws of nature, 24

Leather wetted, lifting a weight, 62

Leaves, oxygen-bubbles rising from, 158

---- stomates in, 161

---- the stomach of a plant, 161

Lepidodendrons, trees of coal, 178, 180, 182

Life of a plant, 170

Light, coloured spectrum of, 39

---- dark and light bands of, 37

---- of the sun, 31

---- effect of, on plants, 45

---- reflection of, 43

---- scattered by particles in air, 71

Light-waves entering the eye, 38

Light-waves, size of, 38

Lightning, 52, 71

Lime, carbonate of, petrifying, 115

Limpet clinging to a rock, 62

Liquid, definition of a, 15

Lines in flowers, 222

Llanberis Pass, 122

Looking-glass, cause of reflection in, 43

Lotus corniculatus, 229

Lubbock, Sir J., cited, 216, 227

Lycopodium like coal-plants, 179

Lyme Regis, landslip of, 103


MAGNETS, attraction and repulsion of, 88

Martineau, Miss C., on echoes, 134

Mediterranean, vapour carried up from, 78

Mercury, action of, in a barometer, 65

Metal reflecting light, 43

Meteors, height of atmosphere shown by, 59

Mississippi delta, 114

Moraines, 120

Mountains causing rainfall, 80

Mouse breathing in bell-jar, 54

Mud in river-water, 105

Musical notes, 140, 142


NASTURTIUM and the bee, 222

Nature and her laws, 24

---- love of, 19

Neath Colliery, fossils from, 175

Newton on light, 34

Niagara Falls, 109-111

Nile plain and delta, 113

Nitre crystals, how to make, 87

Nitrogen in air, 53

Nodules in coal, 177

Noise and music, 140

Norfolk, Virginia, Dismal Swamp in, 183

Notes of music, 142


OIL, its heat and light, 47

Oils in coal, 188, 189

---- in plants, 154, 159, 189

Orange-cells, 154

Orchis mascula, its structure, 231

Otoliths, or ear-stones, 139

Oxygen in air, 53

Ovules of plants, 163


PAN-PIPES, 145

Paper, pressure of air on square inch of, 60

Paraffin from coal 189

Peat, formation of, 184

Petrifactions, 115

Pelargoniums, 222

Pennine Hills causing rainfall, 81

Peter Bell on a primrose, 7

Phosphoric acid, 53

Phosphorus burning in air, 53

Photography, 47

Pimpernel, closing for rain, 217

Plant-cells, 155

Plant, food of a, 156

---- water rising in a, 157

Plants absorbing rain, 81

---- annual and perennial, 161

---- contrivances for protection in, 219

---- effect of light on, 45

---- fertilized by wind, 215

---- in a coal-mine, 174

---- light and heat imprisoned in, 169

---- remains in coal-nodules, 177

Poker, sound of a vibrating, 128

Pollen-dust carried by bees, 215

---- of flowers, 227, 229

Pollen, gathering of, 201

---- use of, 164

Pollinia of an orchis, 231

Polyps, coral, 21

Poole's Cavern, 115

Popgun, compressing air in, 57

Potash formed, 17

Potassium in water, 16

Pot-holes, 109

Pressure, making coal hard, 187

Primrose, corolla falling off, 167

Protoplasm, 155

---- green granules of, 157

Primrose, the life of a, 150

---- two forms of, 163

Princess-bees, slaughter of, 208

Prism giving coloured light, 39

Propolis, or bee-cement, 297


QUEEN-BEE, flight of, 202

---- laying eggs, 203

Queenstown, cliffs at, 110


RAIN, causes of, 79, 80

---- fairies working in, 8

---- fall of barometer before, 66

Ravine worn by water, 107

Reflection of light, 43

Resonance in a jar, 145

Rhine, amount of lime carried by, 106

Roches moutonnes, 121

Rock hurled by waves, 117


ST. JOHN'S WOOD, explosion in, 133

St Paul's railings of Sussex iron, 191

---- Niagara falls only half the height of, 109

Salvia, bee entering the, 225

Sap of plants, 157

Scent of flowers attracts insects, 217

Science, fairy-tales of, 2

---- how to study, 18

Sculptors, water and ice, 99, 118

Sea-breeze and land-breeze, 69

Sea washing away land, 110

---- why salt, 96

---- what becomes of solid matter in, 97

Seeds, how formed, 165

---- oils in, 189

Selaginella, figure of, 179

Shale, piece of, with plants, 175

Shelley, cited, 143

Shell, music of the, 146

Sigillaria, 176, 180

Snow, cause of whiteness of, 90

---- fairies working in, 9

Snow-crystals, 90

Snow-drop fairies, 10

Snowfields, 93

Snow-flakes, crystallization of, 89

Solid, definition of a, 15

Sound, globes of, 132

---- its nature, 127

---- reflection of, 133

Sounds of town and country, 125-127

Sound-waves, 131

South Ouram, coal-nodules at, 177

Spectrum, coloured, 39

Sphinx hawk-moth visiting honeysuckle, 218

Spores of club-moss, 179

---- in coal, 178, 180

Sprengel on insects and flowers, 220, 226, 234

Springs, 93

---- mineral, 95

Stalactites, 115

Stalagmites, 116

Stamens of a flower, 164

Starch in plants, 154, 159

Stars, light of the, 36

---- twinkling of, 71

Stigma of a flower, 165

Stigmas of orchids, 231

Stigmaria root, 175

Stomates in leaves, 161

Stri made by ice, 121, 122

Sugar, carbon in, 159

---- -candy crystals, 86

Sun, distance of the, 29

---- size of the, 29

---- heat and light of, 32

Sunbeams, 27, 42

---- causing colour, 44

---- causing wind, 68

---- how few reach the earth, 32

---- made of many colours, 40

---- rate at which they travel, 38

---- turning water to vapour, 74, 77

Sunrise, 27

Sussex, iron worked in, 191

Swamp, Great Dismal, 183

Swarming of bees, 196, 206

Switzerland, glaciers of, 119

---- snow and ice in, 93


TAR FROM COAL, 189

Tennyson's 'In Memoriam' cited, 192

---- poem of a flower, 152

Thames, drainage of, 104

---- mud-banks, 114

Thunder, noise of, 146

Trade-winds, 69

Treacle and water mixing through a membrane, 157

Trees of the coal forest, 180

Trefoil, structure of flower of, 229

Tumbler of water inverted, 63

Tuning-forks vibrating, 142

Turin, moraines near, 120

Twinkling of stars, 71

Tympanum of the ear, 137

Tyndall, Dr., cited, 75, 87, 91, 128, 144


UNDERCLAYS of coal, 176

Undercliff, Isle of Wight, 103

Undulatory theory of light, 33-35


VIBRATION OR TUNING-FORKS, 142

Violet, structure of the, 227


WALES, rain in, 81

Water, cutting power of, 105-112

---- "hard," 95

---- heat required to vaporize, 92

---- how it rises in a plant, 157

---- in U tube kept up by pressure, 64

---- solid matter dissolved in, 105

Water-dust, 75

Waterfalls, how formed, 108

Water-flowers in ice, 91

Water-pipes, cause of bursting of, 91

Water-vapour invisible, 75, 77

---- screening the sun's heat, 82

Waves, noise of the, 143, 144

---- of light measured, 37

---- of sound crossing each other, 135

Wave-theory of light, 33-35

Wax, plate of in hive, 198

---- formation of, 199

Weight and pressure of air, 58, 60

---- barometer measuring, 64-66

Wheel revolving to make musical note, 141

Williams, Mr. J., cited, 176

Wind, cause of, 67

---- noise of the, 144-146

---- fertilizing plants, 216

Winds, land and sea, 69

---- trade-, 69

Woodstock Park, echoes in, 134

Work of the sunbeams, 42


YOUNG, Dr., cited, 189




+----------------------------------------------------------------------+
|                                                                      |
| FOOTNOTES:                                                           |
|                                                                      |
| [1] I am quite aware of the danger incurred by using this word       |
| "force," especially in the plural; and how even the most modest      |
| little book may suffer at the hands of scientific purists by         |
| employing it rashly. As, however, the better term "energy" would     |
| not serve here, I hope I may be forgiven for retaining the           |
| much-abused term, especially as I sin in very good company.          |
|                                                                      |
| [2] Manchester Science Lectures,' No. 1, Second Series. John         |
| Heywood, 141, Deansgate, Manchester.                                 |
|                                                                      |
| [3] These specimens are eventually going to South Kensington.        |
|                                                                      |
| [4] These and the preceding numerical statements will be found       |
| worked out in Sir J. Herschel's 'Familiar Lectures on Scientific     |
| Subjects,' 1868, from which many of the facts in the first part      |
| of the lecture are taken.                                            |
|                                                                      |
| [5] The width of an inch may be seen in Fig. 12, p. 60.              |
|                                                                      |
| [6] Light travels at the rate of 192,000 miles, or 12,165,120,000    |
| inches in a second. Taking the average number of wave-lengths in     |
| an inch at 50,000, then 12,165,120,000 x 50,000 =                    |
| 608,256,000,000,000.                                                 |
|                                                                      |
| [7] 100 cubic inches near the earth weighed 31 grains, while the     |
| same quantity taken at four and a half miles up in the air           |
| weighed only 12 grains, or two-fifths of the weight.                 |
|                                                                      |
| [8] In fastening the string to the leather the hole must be very     |
| small and the knot as flat as possible, and it is even well to       |
| put a small piece of kid under the knot. When I first made this      |
| experiment, not having taken these precautions, it did not           |
| succeed well, owing to air getting in through the hole.              |
|                                                                      |
| [9] The engraver has drawn the tumbler only half full of water.      |
| The experiment will succeed quite as well in this way if the         |
| tumbler be turned over quickly, so that part of the air escapes      |
| between the tumbler and the card, and therefore the space above      |
| the water is occupied by air less dense than that outside.           |
|                                                                      |
| [10] A floating iceberg must have about eight times as much ice      |
| under the water as it has above, and therefore, when the lower       |
| part melts in a warm current, the iceberg loses its balance and      |
| tilts over, so as to rearrange itself round the centre of            |
| gravity.                                                             |
|                                                                      |
| [11] 58,311 square miles.                                            |
|                                                                      |
| [12] See the picture at the head of the lecture.                     |
|                                                                      |
| [13] Sound travels 1120 feet in a second, in air of ordinary         |
| temperature, and therefore 112 feet in the tenth of a second.        |
| Therefore the journey of 56 feet beyond you to reach the wall and    |
| 56 feet to return, will occupy the sound-wave one-tenth of a         |
| second and separate the two sounds.                                  |
|                                                                      |
| [14] To enjoy this lecture, the child ought to have, if possible,    |
| a primrose-flower, an almond soaked for a few minutes in hot         |
| water, and a piece of orange.                                        |
|                                                                      |
| [15] The common dilute sulphuric acid of commerce is not strong      |
| enough for this experiment, and any child who wants to get pure      |
| sulphuric acid must take some elder person with him, otherwise       |
| the chemist will not sell it to him. Great care must be taken in     |
| using it, as it burns everything it touches.                         |
|                                                                      |
| [16] See the plant in the foreground of the heading of the           |
| lecture.                                                             |
|                                                                      |
| [17] I am much indebted to Mr. John Williams, of Neath, for          |
| procuring these fossils for me; and also to Professor Judd for       |
| lending me some for an earlier lecture.                              |
|                                                                      |
| [18] I am much indebted to Mr. Carruthers, of the British Museum,    |
| for allowing me to copy this figure from his original diagram of     |
| a coal-ball, and also for giving me much valuable assistance.        |
|                                                                      |
| [19] The scarlet and other bright geraniums of our flower-gardens    |
| are not true geraniums, but pelargoniums. You may, however, watch    |
| all these peculiarities in them if you cannot procure the true       |
| wild geranium.                                                       |
|                                                                      |
|                                                                      |
+----------------------------------------------------------------------+

+----------------------------------------------------------------------+
|                                                                      |
| Transcriber's notes:--                                               |
|                                                                      |
| Page 187: 'bencils' corrected to 'pencils' 'for ordinary             |
|   cedar pencils'.                                                    |
|                                                                      |
| Index: Page number for 'propolis' corrected from 297 to 197.        |
|                                                                      |
| In this text version, italics are represented by underscores.        |
|                                                                      |
+----------------------------------------------------------------------+


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[End of _The Fairy-Land of Science_ by Arabella B. Buckley]
