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UNIVERSITY OF CALIFORNIA.
Class
THE SCIENCES
A READING BOOK FOR CHILDREN
ASTRONOMY, PHYSICS HEAT, LIGHT, SOUND,
ELECTRICITY, MAGNETISM CHEMISTRY,
PHYSIOGRAPHY, METEOROLOGY
BY
EDWARD S. HOLDEN
GINN & COMPANY
BOSTON NEW YORK CHICAGO LONDON
ENTERED AT STATIONERS' HALL
COPYRIGHT, 1902, BY
EDWARD S. HOLDEN
ALL RIGHTS RESERVED
68.10
tgftc
GINN & COMPANY PRO-
PRIETORS BOSTON ' U.S.A.
TO
MY YOUNG FRIEND
treble
190795
PREFACE
THE object of the present volume is to present chapters to be
read in school or at home that shall materially widen the outlook
of American school children in the domain of science, and of the
applications of science to the arts and to daily life. It is in no
sense a text-book, although the fundamental principles underlying
the sciences treated are here laid down. Its main object is to help
the child to understand the material world about him.
All natural phenomena are orderly; they are governed by law;
they are not magical. 1)hey are comprehended by some one ; why
not by the child himself ? It is not possible to explain every detail
of a locomotive to a young pupil, but it is perfectly practicable to
explain its principles so that this machine, like others, becomes a
mere special case of certain well-understood general laws.
The general plan of the book is to waken the imagination ; to
convey useful knowledge ; to open the doors towards wisdom. Its
special aim is to stimulate observation and to excite a living and
lasting interest in the world that lies about us. The sciences of
astronomy, physics, chemistry, meteorology, and physiography are
treated as fully and as deeply as the conditions permit ; and the les-
sons that they teach are enforced by examples taken from familiar
and important things. In astronomy, for example, emphasis is laid
upon phenomena that the child himself can observe, and he is
instructed how to go about it. The rising and setting of the stars,
the phases of the moon, the uses of the telescope, are explained in
simple words. The mystery of these and other matters is not magical,
VI PREFACE
as the child at first supposes. It is to deeper mysteries that his
attention is here directed. Mere phenomena are treated as special
cases of very general laws. The same process is followed in the
exposition of the other sciences.
Familiar phenomena, like those of steam, of shadows, of reflected
light, of musical instruments, of echoes, etc., are referred to their
fundamental causes. Whenever it is desirable, simple experiments
are described and fully illustrated, 1 and all such experiments can
very well be repeated in the schoolroom.
Finally, the book has been thrown into the form of a conversation
between children. It is hoped that this has been accomplished
without the pedantry of Sandford and Merton (although it must be
frankly confessed that the principal interlocutor has his knowledge
very well in hand for an undergraduate in vacation time) or the sen-
timentality of other more modern books which need not be named
here. The volume is the result of a sincere belief that much can
be done to aid young children to comprehend the material world
in which they live and of a desire to have a part in a work so very
well worth doing.
EDWARD S. HOLDEN.
THE CENTURY CLUB,
. NEW YORK CITY, January, 1903.
l Illustrations have been reproduced from many well-known books, especially from the
reading books of Finch and Stickney, Frye's geographies, Davis' physical geography and
meteorology, Gage's text-books of physics, Young's text-books of astronomy, etc. To the
authors of these works the writer begs to express his sincere thanks.
CONTENTS
PREFACE
PAGE
V
INTRODUCTORY CHAPTER . . .
BOOK I. ASTRONOMY, The Sci-
ence of the Sun, Moon, and
Stars
The Earth as a Planet ....
Distance of the Moon from the
Earth
Distance of the Sun from the
Earth
The Diameter of the Earth . .
Distance of the Sun from the
Earth .........
The Planets Mercury and Venus
The Planets Mars, Jupiter, Sat-
urn, Uranus, and Neptune
Distances of the Planets from the
Sun
How to make a Map that shows
the Sun and Planets . . .
Scale of the Map
Sizes of the Planets compared to
the Sun
The Solar System; the Sun and
Planets
Relative Sizes of the Planets
The Moons of the Planets . .
The Minor Planets; the Aster-
oids
Comets
The Stars . ....
9
9
ii
ii
12
14
16
16
17
i?
18
25
28
3
32
32
3 2
Distances of the Stars . ... 32
What is a Planet ? 33
Phases of the Moon (New Moon,
Full Moon, etc.) 34
Number of the Stars .... 38
Clusters of Stars 39
The Pleiades 39
The Milky Way 41
Do the Stars have Planets as the
Sun does ? .42
Shooting Stars ; Meteors ; Fire-
balls 44
The Zodiacal Light 46
Nebulae 47
Rising and Setting of the Sun . 48
How the Sun appears to move
from Rising to Setting .
The Celestial Sphere . .
The Northern Stars . . ,
The Great Bear (the Dipper)
The Southern Stars . .
Time and Timekeeping
Telescopes 56
A Meridian Circle 57
The Lick Telescope . . . . 61
The Moon 62
Mountains on the Moon ... 62
Life on the Planets 64
The Planet Mars . . . . . . 64
The Planet Jupiter 64
Appendix (Statistics of the Solar
System) 66-70
49
49
5*
53
54
56
Vlll
CONTENTS
BOOK II. PHYSICS, The Science
that explains Heat, Light,
Sound, Electricity, Magnetism 73
Solids and Liquids 73
Solids, Liquids, and Gases are
made up of Millions of Small
Particles 74
Heat makes Solids, etc., expand 74
Most Gases are Invisible ... 77
The Diving Bell 78
The Earth's Atmosphere ... 78
Balloons 80
Air is Heavy 81
Reservoirs, Fountains, and the
Water Supply of Cities . . 81
The Barometer 83
The Air presses about Fifteen
Pounds on Every Square Inch 84
How to measure the Heights of
Mountains 85
The Barometer is a Weather-
glass 86
United States Weather Bureau
Predictions 88
Thermometers ...... 88
Steam 90
The Steam Engine .... 91
The Locomotive 94
The Steamship 96
Light 96
The Sun's Rays travel in
Straight Lines 96
Shadows 101
Eclipses of the Sun and Moon 102
Reflection of Light . . . .104
Refraction of Light . . . .105
Prism; the Spectrum . . . 105
Lenses 106
Spectacles 107
PAGE
Sound no
Velocity of Sound and Light no
Sound is a Vibration . . .112
Musical Instruments (Bells,
Pianos, Violins, Organs,
Drums) 113
Reflection of Sound . . . .116
Echoes 116
Musical Notes 116
The Phonograph 117
Electricity 119
Apparatus needed . . . .119
Experiments 120
Benjamin Franklin's Kite . .123
Experiments 123
Electric Batteries 124
The Telegraph 125
Telegraphic Alphabet . . .127
Velocity of Electricity . . . 1 28
Magnetism 128
Experiments 129
Magnets 129
Natural Magnets (Lode-
stones) 133
Electro-Magnets . . . .133
Telegraph Instruments . . .133
Electric Bells 134
The Telephone 137
The Mariner's Compass . .138
The Electric Light . . . .140
The Dynamo 142
Electric Railways 143
Appendix 144-147
BOOK III. CHEMISTRY, The Sci-
ence that teaches how to com-
bine Two Substances so as to
produce a Third Substance dif-
ferent from Either . . . .149
CONTENTS
IX
Physical Changes; Solutions . 150
Mixtures 150
Chemical Combinations . . -151
Chemistry (defined) 152
Chemical Affinity 152
Gunpowder 153
Bread Making 1 54
Composition of the Air . . .155
Oxygen 155
Nitrogen 155
Combustion 156
Hydrogen 157
Balloons 157
Water 157
Chemical Elements 158
Metals 158
Non- Metals 158
Chemical Compounds . . . .159
BOOK IV. METEOROLOGY, The
Science of the Weather . .161
The Atmosphere ; the Colors of
Sunset and Sunrise . . . .161
Eruption of Krakatoa (1883) . 162
Twilight 163
Dust in the Atmosphere . . .163
The Rainbow 164
Halos 1 65
Fog and Clouds 165
Dew 167
Height of Clouds 167
Rain 168
Size of Raindrops 168
Hail, Snow, and Sleet . . . .168
The Snow Line (Line of Per-
petual Snow) 1 68
Snow Crystals 169
Uses of Snow 169
Irrigation of Farming Lands . 169
Frost 170
Rainfall 170
Rainfall and Crops 170
Winds 171
Wind Vanes 171
Force of the Wind . . . .171
Hurricanes 171
Causes of the Winds . . . 172
Land and Sea Breezes . . .174
Weather , . 174
The Seasons (Spring, Summer,
Autumn, Winter) . . . .175
Storms 175
Weather Predictions . . .176
United States Weather Bureau 176
Storm and Other Signals . .176
Value of Weather Predictions 178
Summer Thunderstorms . . 179
Lightning 180
Thunder 180
Distance of a Thunderstorm
from the Observer . . . 181
Lightning Rods 182
BOOK V. PHYSIOGRAPHY, The
Science of the Land and of the
Sea 185
The Oceans 185
Depth of the Sea . -.. . . . 186
Soundings 186
The Sea Bottom . . . . .187
Dredging 187
Ooze 187
Fish 188
Phosphorescent Fish . . .188
Deep-Sea Fish . . . . . 189
Icebergs 189
Glaciers 191
Bowlders 191
CONTENTS
Pack-ice 191
Ice- Worn Rocks 192
Rivers and Streams . . . .193
Underground Water . . .193
Meandering Streams . . .194
Habits of Rivers 195
Canons 196
Flood Plains 197
Waterfalls 198
The Land 199
Changes in the Land . . .199
Mountains sculptured by
Rains 200
Sand Dunes 200
Waste of the Land . . . .201
Slow Motions of the Con-
tinents 202
Fossils 203
Sandstones 204
The Interior of the Earth . . 205
Stratified Rocks 205
Formation of Mountain
Ranges 205
The Oldest Mountains in
America 208
The Age of the Earth . . . 209
Age of Different Parts of
America 209
PACK
Age of Man on the Earth . .211
Flint Weapons 211
The Earliest Drawing . . .211
The First Plaything . . . .212
A Geyser 213
The Internal Heat of the Earth 214
Volcanoes 214
Teneriffe 214
Kilauea 215
Vesuvius 215
Herculaneum and Pompeii .215
Volcanoes in the United States 2 18
Old Lava Fields in Idaho,
Oregon, and Washington . 218
Earthquakes 218
Cause of Earthquakes . . . 219
The Charleston Earthquake
(1886) 219
The Mississippi Valley Earth-
quake (1811) 222
What to do during an Earth-
quake 222
Earthquake Detectors how
to make them 222
The Lisbon Earthquake (1755) 223
Sea Waves 224
The United States Ship Wateree
at Iquique (1868) 224
THE SCIENCES
INTRODUCTORY CHAPTER
(To be read by the children who own this book)
LET me tell you how this book came to be written. Once
upon a time, not so very long ago, a lot of children were
spending the summer together in the country. Tom and
Agnes were brother and sister and were together all the day
long ; bicycling or playing golf in the morning, reading or
studying in the afternoon. The people who lived in the vil-
lage used to call them the inseparables because they were
always seen together during their whole vacation from June to
September.
Their cousins Fred and Mary always spent a part of every
summer with them ; and when they came there were four
inseparables, not two. The children liked the same games,
liked to read the same books, to talk about the same kind of
things, and so they got on very well together ; though some-
times the two boys would go off by themselves for a hard day's
tramp in the hills, or to shoot woodchucks, or for a very long
bicycle ride, leaving their sisters at home to play in the garden
with dolls, or to do fancywork and embroidery, or to play
tennis, or to read a book together. Tom was thirteen years
old then, and his sister Agnes was nine ; cousin Fred was ten
and his sister Mary was twelve.
i
2 THE SCIENCES
When the summer afternoons began to get very warm, in
July, a rule was made that the children should spend them in
the house, or on the wide, shady porch, or else under the trees
on the lawn, or in the garden. Golf, tennis, and wheeling had
to be done in the morning ; the afternoons were to be spent in
something different. Tom's father used to say that the proverb
All work and no play
Makes Jack a dull boy
was only half a proverb. It was just as true, he said, that
All play and no work
Makes Jack a sad shirk.
And so a part of every summer afternoon was given up to read-
ing some good book, or to study, or to work of some sort. The
two boys had their guns and wheels to keep thoroughly bright
and clean, and a dozen other things of the sort ; the two girls
had sewing to do ; and all of them, together agreed to keep the
pretty garden free from weeds.
Almost any afternoon you might see the four inseparables
tucked away in a corner of the broad piazza, each one busy
about something, and all talking and laughing except, of
course, when one of them was reading, and the others paying
good attention. Tom's big brother Jack was at home from
college, and in the afternoons he was almost always on the
porch reading, or else on the green lawn lying under the trees ;
and Tom's older sisters, Mabel and Eleanor, were there too,
sewing, or embroidering, or reading, or talking together.
So there were two groups, the four children the insepara-
bles and the three older ones. When the children came to
something in their book that they did not quite understand,
Tom would call out to his big brother Jack to explain it to
INTRODUCTORY CHAPTER 3
them, and Jack would usually get up and come over to where
the children were and tell them what they wanted to know.
Almost every day there were conversations of the sort, and
explanations by some one of the older ones to the four
children. All kinds of questions would come up, like these :
FIG. i . THE PORCH
"Jack, tell us why a 'possum pretends to be dead when
he is only frightened and wants to get away."
"Jack, tell us why a rifle shoots so much straighter than a
shot-gun or a musket."
"Jack, what's the reason that a lobster hasn't red blood?"
or else :
" Eleanor, what is the difference between a fern and a tree ? "
"Is that coral bead made by an animal or an insect?"
"What is amber, anyway?" and so on.
THE SCIENCES
The children had no end of questions to ask, and Jack or
one of the older girls could generally answer them. When
they could not give a complete answer the dictionary was
brought out ; and if that was not enough, a volume of the
encyclopaedia. Sometimes the questions were talked over at
the dinner table and the whole family had something to say.
Tom's father had traveled a great deal and
could almost always tell the children some
real "true" story something that had
happened to himself personally, or that he
had read.
The chapters in this book are conversa-
tions that the children had among them-
selves or with the older people. They are
written down here in fewer words than
those actually spoken, but the meaning is
the same.
When the children were talking about
electric bells, for instance, they actually
strung a wire from one end of the long
It costs about $1.10. The
two wires are to be fastened porch to the other, and put a real bell at
to the two screw posts in one en Q f j t an d a pus h button and a
the picture one at the . .
left-hand side, and one in battery at the other. In this book there
the middle, of the top of i s a picture showing exactly what they
did ; but, after all, you cannot understand
an electric bell half so well by a picture as you can by the
real bell and the real wire. 1 So when one of the children
who is reading this book comes to an experiment he must read
all that the book says about it, and understand it as well as he
1 Children should be careful to read the titles printed under each picture with
attention. The titles explain what the picture means.
FIG. 2. A CELL OF
DRY BATTERY
INTRODUCTORY CHAPTER 5
can. If he can get an electric battery, and a bell, and wire,
and a push button, then the picture in this book will tell him
exactly how to join them together; and when he has done this
and actually tried the experiment and made it succeed he
will know as much about electric bells as he needs to know.
If he cannot get the bell and the wire, and so forth, he can
probably see a bell of the sort somewhere ; and if he keeps his
eyes open and thinks about what he has read, he can certainly
understand how it works. Here is the battery always trying
to send out a stream of electricity along any wires joined to
the two screws at the top. Here is the wire, which is almost
Push
Button
Battery ' ' 1
'Bell
FIG. 3
a complete loop almost but not quite. If the loop were con-
tinuous, if the wire were all in one piece, then the stream
of electricity would flow along the wire from the battery and
would ring the bell.
The use of the push button is to make the wire continuous
to join the two ends of it so that the stream of electricity
can pass along it. When you have done this when you have
joined the ends of the loop of wire the bell rings, and only
then, which is just as it should be.
This book gives the pictures and the explanations. They
can be understood by paying attention ; and when they are
once understood a great number of things will be clear that
THE SCIENCES
all children ought to know, and that have to be learned some-
time. Why not now ? The sooner the better.
If you read what is written in the
book and perfectly understand it, that
is very well. If there is an experi-
ment to be tried, and you can get the
things to try it with, so much the bet-
ter. If you have any trouble in
understanding, ask some one your
father, your mother, your teacher
to explain to you. If you can find
another book a dictionary or an
encyclopaedia that describes the
same experiment, read that too.
Perhaps it will tell you what you
want to know, better, or more simply,
or more fully, or in a different way.
Then, finally, keep your eyes open to
actually see in the world the things
that are talked about in this book.
When you see them try to understand
them. Remember what you have
read here, and you will find that you
understand a good many things that
you see about you every day. Some-
body understands these things,
push buttons, electric lamps, tele-
scopes, and so forth. Why should
FIG. 5. A PUSH BUTTON not you ? You can if you pay
it costs thirty cents. The two attention enough. The world is,
wires are fastened to two screws ' , . T . .
inside the push button. after all, your world. It belongs to
FIG. 4. AN ELECTRIC BELL
It costs seventy-five cents. The
wires are fastened to the two
screws at the bottom of the box.
INTRODUCTORY CHAPTER 7
you as much as it belongs to any one. The things in it can all
be explained and understood. It is everybody's business to
try to understand them at any rate. All these things concern
you. The more you know about them, the better citizen you
can be the more useful to your country, to your friends, and
to yourself.
THE MOON
The moon, from a photograph taken with the great telescope of the Lick Observatory.
BOOK I
ASTRONOMY
THE SCIENCE OF THE SUN, MOON, AND STARS
The Earth as a Planet. The children were looking at a map
of the world one fine afternoon and studying the way the land
and water are distributed, when Agnes said : " I never knew
before how little land there was on the earth. Why, there is
very much more water than land." "Oh, yes," said Tom,
"there's very much more water on the surface; but it's all
land at the bottom of the ocean. The sea is about three miles
deep, you know, and then you come to the ocean bottom, and
that is solid land again. The earth is nearly all rocks and soil ;
only a little of it is water, after all, but that little is on the
surface, of course, and that is why it shows."
Agnes. So the earth is almost all land ; if you dig down deep
enough, you would come to rocks, even below the oceans ?
Tom. Yes, and if you went up high enough, you would
come to nothing. You would come to air first, and then by
and by to no air, and then you would come to just nothing
to empty space.
Agnes. Well, it is n't quite empty, as you call it. There
are other globes in space. There are other planets, and the
sun and the moon, and there are simply thousands of stars.
So space is n't empty ; it is pretty full !
9
FIG. 6. AMERICA
FIG. 7. THE OLD WORLD
10
ASTRONOMY 1 1
Distance of the Moon and of the Sun from the Earth. Here
Tom's big brother Jack looked up from his book and said :
" Well, that depends on what you call full. It is 240,000 miles
from here to the moon, and the moon is the very nearest of all
the heavenly bodies to us. There is a good deal of empty
space between us and the moon, it seems to me."
Agnes. Two hundred and forty thousand miles ! Oh, Jack,
is that right?
Jack. Why, that is n't a beginning ; how far off do you sup-
pose the sun is ? It is 93,000,000 miles millions this time,
FIG. 8
This picture shows the height of land on the earth compared to the depth of the sea. If
you could cut the earth through and through with a knife and look at one part only, it
would look something like the picture. All the shaded part \^\\ is land. The curved
line drawn all across the picture, near the top, is the curve of the surface of the oceans.
Part of one of the oceans is shown by the white space below this curved line and above
the floor of the ocean itself, the shaded land. The curve of the ocean surface is con-
tinued across the picture underneath the mountains. If the surface of the earth were
all water, the bounding line would be this curve. From side to side of the picture is
about 350 miles. If the whole circle of the earth were drawn, it would be about eight
feet in diameter. That is the scale of the drawing.
not thousands ; and some of the planets are much farther off
yet, and every one of the stars is farther off still.
Agnes. Jack, tell us about it, will you ? We don't know,
and you do.
Jack. The very first thing you have to think about is the
size of the earth. How far is it through and through the
earth, Tom ? If you pushed a stick through the earth from
New York to China, how long would the stick be ?
12
THE SCIENCES
The Diameter of the Earth. Tom. The geography says that
the diameter of the earth is 8000 miles ; so the stick would
FIG. 9. A BALLOON
Balloons carrying men have gone up more than five miles, and small balloons carrying
thermometers, etc., have been sent nearly ten miles high. The atmosphere of the earth
extends upwards a hundred miles or so, but beyond this there is no air nothing but
empty space.
have to be 8000 miles long, as long as from Cape Horn to
Hudson Bay, my teacher says.
ASTRONOMY
Jack. That 's about right. Suppose there were a railway
from Hudson Bay to Cape Horn, and express trains run-
ning on it at the rate of 40 miles an hour. Let us see how
long they would take to go the 8000 miles. They would go
FIG. 10. THE FULL MOON RISING IN THE EAST
40 miles in one hour, and 80 miles in two hours, and 960 miles
in a day say 1000 miles a day. Well, they would take eight
days to go the 8000 miles, then. Now, suppose we could
build a railway to the moon. How long would an express train
take to go the distance ? Take your pencil, Tom, and cipher
it out.
THE SCIENCES
Tom. You said the distance from the earth to the moon
was 240,000 miles. If the train goes 1000 miles a day, it
would take 240 days. I don't need any pencil.
Jack. Sure enough ; and 240 days is eight months (8 x 30
= 240). It would take the train eight months to go from the
earth to the moon, then eight whole
months, traveling night and day at forty
miles and more every hour.
Agnes. I should be nearly a year older
when I got there than when I started,
then.
Jack. Yes, and recollect that there are
no stations on the railway to the moon.
The moon is the heavenly body that is
nearest to us, so that space is pretty
nearly empty, after all.
Distance of the Sun from the Earth.
Tom. How far did you say it was from
the earth to the sun 93,000,000 miles ?
Jack. That's right. You will need your
pencil to figure out how long the express train would take to
go from the earth to the sun, Tom.
Tom. Yes, it is like this, is n't it ? The train goes
1000 miles in a day; then it will take 93,000 days to get to
the sun.
30)93000 days
12) 3100 months
258^ years
It would take 3100 months, that is more than 258 years, to
get to the sun. That 's a long journey ! You would have 258
birthdays on the road, Agnes.
FIG. ii. A SCHOOL
GLOBE
ASTRONOMY 15
Jack. Put it this way, Tom : 258 years ago takes you back
to the year 1643 (1901258= 1643). The Pilgrims had been in
New England only twenty-three years in 1643, for they came
in 1620 (1643 1620 = 23). Suppose one of those Pilgrims
FIG. 12. THE PILGRIMS LANDING ON PLYMOUTH ROCK FROM THEIR SHIP,
THE " MAYFLOWER," DEC. 20, 1620
to have stepped on to the train at Plymouth Rock ; he would
have been traveling all these years, and he would only have
arrived at the sun a few years ago ; that is, if he had lived
to make the journey.
Tom. Two hundred and fifty-eight years !
1 6 ,THE SCIENCES
The Planets Mercury and Venus. Jack. Yes, and nearly
all that space is empty too. There are only two planets
between the earth and the sun Mercury and Venus.
Agnes. Venus, the evening star ?
Jack. Yes, Venus is the evening star sometimes. Venus
and Mercury are the only planets that the Pilgrim would pass
on the road from the earth to the sun. Space is rather empty,
is n't it ?
Agnes. Are n't there any stars in between the earth and
the sun, Jack ?
Jack. Not one ; the real stars are thousands and thousands
of times farther off. We call Venus the "evening star," but
Venus is not a star at all, but a planet. Let me tell you, so
that you can make a sort of picture of it all in your minds.
The sun is there in the middle of space and all the planets
move round him, just as the earth does. Nearest to the sun
is the planet Mercury, and then comes the planet Venus, and
then the planet Earth.
Agnes. That sounds queerly " the planet Earth " though
of course we know the Earth is a planet.
The Planets Mars, Jupiter, Saturn, Uranus, 1 and Neptune.
Jack. Yes, exactly so. And then there are other planets
farther away from the sun than the earth ; Mars for one, and
then Jupiter, and then Saturn, and then Uranus, and then
Neptune. That is all we know of ; there may be more of
them. Neptune is thirty times as far from the sun as the
earth is. Here is a little table that I will write down for you
to keep. You need not memorize it, only recollect that
Mercury and Venus are nearer to the sun than we are, and
that all the others are farther away.
1 Pronounced u'ra-nus.
ASTRONOMY 17
DISTANCES OF THE PLANETS FROM THE SUN
The planet Mercury is 36 million miles from the sun
" Venus " 67 " " "
" Earth " 93 " " "
" Mars " 141 " " "
" Jupiter " 483 " " "
" Saturn " 886 " " "
" Uranus " 1782 " " "
" Neptune 2791 " " "
Jupiter is five times, and Neptune is thirty times, as far from
the sun as the earth is.
Tom. Is n't there a map of all these planets that we
can see ?
Jack. No, and there 's a good reason why. Suppose you
tried to make a map of them, and suppose you took the dis-
tance from the Sun to the Earth on the map to be an inch.
Don't you see that the distance from the Sun to Neptune
would have to be thirty times one inch, and the page of your
book thirty inches wide nearly a yard wide ?
Tom. Of course, no book has a page as big as that ; but
you might make little maps.
How to make a Map that shows the Sun and Planets. Jack.
You and Agnes can make a map yourselves to-morrow morn-
ing, if you want to, when you go out for a walk, and I '11 tell
you how to do it.
Suppose you take the large globe in the library, that you
were looking at just now, to stand for the Sun. It is two feet
in diameter. Well, the diameter of the real Sun is 870,000
miles, and your map has to be made all to one scale. Every
step of yours is about two feet long, is n't it, Tom ? Try it.
Tom. Yes, my steps are almost exactly two feet long.
i8
THE SCIENCES
Jack. Well, remember to-morrow that every step you take
along the road to the village is really only two feet long, but
that it stands on the map for 870,000 miles.
Agnes. Are we going to make the map along the road ?
FIG. 13. THE ROAD TO THE VILLAGE
Jack. My dear, you have to do it that way ; your map is
going to be nearly a mile and a quarter long. You have to use
the whole country round to make it.
Agnes. Well, that is a map !
Tom. How shall we make it, Jack ?
Jack. You start, you know, with this globe in the house to
stand for the Sun. The globe is two feet in diameter, and the
real Sun is 870,000 miles in diameter.
Scale of the Map. "So, recollect, every two feet on your
map is 870,000 miles. Every one of your steps, Tom, stands
for 870,000 miles.
ASTRONOMY 19
"You must take with you
a very small grain of canary-bird seed to stand for the planet Mercury ;
a very small green pea to stand for the planet Venus;
a common green pea to stand for the planet Earth;
a rather large pin out of Agnes' work box, and let its round head stand
for the planet Mars;
an orange to stand for the planet Jupiter;
a golf ball to stand for the planet Saturn;
a common marble to stand for the planet Uranus ;
a rather large marble to stand for the planet Neptune.
Sizes of the Planets compared to the Sun. "If this globe,
two feet in diameter, stands for the Sun (which is really 870,000
miles in diameter), then a common green pea is just the right
FIG. 14
The sizes of the planets of the Solar System (the Sun's family) compared with each other.
h = Saturn; T/= Jupiter; tp= Neptune; & = Uranus;
'i-e <
but
,, , .. . ., , n ot to its middle part.
Here are four little piles of saw-
dust, of copper filings, of sand, and of coal dust. Try to pick
them up with your magnets.
Agnes. They do not move ; magnets
do not attract such things as sand.
Jack. No;
FIG. in
FIG. 112
magnets attract
iron and steel
nothing else.
you take a
A horseshoe magnet attracts iron
filings to its ends; but if you
try the curved part of the mag-
net on a needle, there is almost pile of CODDer
no attraction.
filings and iron
filings mixed together, the magnet will
pick up the iron filings and leave the
copper. Try the experiment and see for
yourself.
Tom. So it does. That is a way of FlG - "3- A HORSESHOE
, r MAGNET WITH AN IRON
sorting iron out of a pile. If some one BAR (AN ARMATURE)
told me to pick the iron filings out of ACROSS ITS ENDS
this pile by hand, it would take all day
to do it ; but with a magnet I can do it in five minutes.
Jack. See what the magnet will do through a pane of
glass. Lay a needle on a pane of glass held horizontally and
130
THE SCIENCES
put the magnet under the glass. You will see that the needle
moves over the glass as you move the magnet around.
Tom. So it does ; glass does not stop the attraction.
Jack. Try putting the needle on a sheet of writing paper or
on a piece of silk.
Tom. It is just the same; the needle moves when I move
the magnet.
Jack. So much is clear ; a magnet is made of iron; it attracts
iron and nothing else; it attracts it through silk, or paper,
or glass through any-
thing.
These magnets that
you have been using
are manufactured.
They were made. Let
us make some more.
Agnes, have you got
any needles ?
Agnes. Here are some.
Jack laid the needles
on the table and rubbed
them with the horseshoe
magnet, as if he were
stroking them with it. 1
He tried each needle on
the pile of iron filings,
and every one was able to lift up some filings just as the horse-
shoe magnet did. Then he took two of the needles and tied a
bit of silk about each, near its middle, and hung the silk from
1 Make all the strokes on all the needles in one direction, so as to have the needle
magnets all alike. Stroke all of them from eye end to point, or all from point to eye.
FIG. 114
Iron filings on a horizontal pane of glass will move
into a certain set of curves when yon hold a horse-
shoe magnet underneath the glass. (You must
tap the glass very gently with your finger tip.)
PHYSICS
two pencils (see Fig. 115), so that he had two little magnets,
like pendulums. Next he took the bar magnet a straight
magnet and tried some experiments with needle No. i (the
other needle was laid aside for the moment). The bar magnet
pencil ^^i -^tp pencil
silk
needle
no. i
silk
needle
no. 2
FIG. 115
had two ends of course ; one was the point, and the other
happened to be painted red.
point
red
FIG. 116
By trials with needle No. i he found :
1. That the point of the bar magnet attracted the point end
of needle No. i.
2. That the point of the bar magnet repelled the eye end of
needle No. i.
3. That the red end of the bar magnet repelled the point
end of needle No. i.
4. That the red end of the bar magnet attracted the eye end
of needle No. i.
Then he tried needle No. 2 and found just the same things
for it also.
132 THE SCIENCES
5. The point of the bar magnet attracted the point end of
needle No. 2 ;
6. and repelled the eye end of No. 2.
7. The red end of the bar magnet repelled the point end
of No. 2 ;
8. and attracted the eye end of No. 2.
The next thing was to put aside the bar magnet and to try
the two needles together. He found :
9. That the two points of the needles repelled each other.
10. That their two eye ends repelled each other.
11. and 12. That the point end of either needle attracted the
eye end of the other. 1
Tom. What is the explanation of all these experiments,
Jack ?
Jack. It is like this : just suppose there were two kinds of
magnetism in the bar magnet. We might call them point-end
magnetism and red-end magnetism, for want of better names.
Now when we made magnets out of these needles we put the
two kinds of magnetism into them. We put one kind into the
point ends of both needles and another kind into their eye
ends. Suppose we say that point-end magnetism, where-
ever it is found, will repel point-end magnetism ; and that
red-end magnetism, wherever found, will repel red-end mag-
netism ; and that point-end magnetism will attract red-end
magnetism, and vice versa, wherever they are found. Would not
that explain all that we have seen ?
Taking all the twelve cases one by one, the children found
that the explanation was right. Magnetism of the same name
repels ; magnetism of different name attracts. It is not easy
1 These experiments take some space to describe, but they are so interesting
that they should be tried in the schoolroom.
PHYSICS
133
to explain in simple words why this is so ; but any child who
will pay attention and make these simple experiments can
prove it.
Natural Magnets. "These magnets were artificial; they
were manufactured," said Jack ; "but there are stones that are
magnetic to begin with. They were first found in Magnesia,
a town of Asia Minor, long ago, and the
ancients therefore called them magnets."
Mary. In the Arabian Nights, in " Sind-
bad the Sailor," there is a story of a whole
mountain made of magnets, so that when
a ship came that way the mountain pulled
all its iron nails out, and the ship broke to
pieces and sank.
Agnes. That is n't true, is it Jack ?
Jack. Certainly not, my dear ; it is one
of the big stories told by travelers. But
don't you recollect how they got past the
mountain with their ships ?
Mary. They built their ships with wooden
pins instead of nails and got safely past,
so the story says.
Electro-Magnets. Jack. There is an-
other kind of magnet that I want you to know about. It is
made by a current of electricity from a battery passing through
a wire wrapped round a bar of soft iron. (See Fig. 1 17.)
You see now how a telegraph operator in New York
can make a click on the sounder in Boston. The bat-
tery current is flowing all the time except just at the
moment when the New York man lifts his key and breaks
the circuit.
FIG. 117
If wire be wrapped in a
spiral around a bar of
iron, and if a current of
electricity flow through
the wire, the bar be-
comes a magnet and
stays so as long as the
current is flowing, and
no longer.
134
THE SCIENCES
The electro-magnet of the sounder in Boston is a magnet so
long as the current flows, and stops being a magnet the
FIG. 118
Electro-magnets are often made of a core of soft iron bent into the shape of a horseshoe,
and wound with wire. The two ends of the wire go to the copper and zinc of a battery.
So long as the current flows the iron core is a magnet. When the current stops it is no
longer a magnet.
instant the current stops. Whenever the New York man lifts
his key the Boston sounder makes a click a dot or a dash,
just as he chooses. In that way the message is spelled out.
Key in
New York
Bai
Sou ider
in Boston
tery
FIG. 119
Electric Bells. "Now," said Jack, "it is easy to understand
how electric bells work. It is like a telegraph. In the first place
you must have a battery. We could make a battery by using
PHYSICS
135
several tumblers (like those described on page 124), but it is
more satisfactory to buy one cell of "dry "battery, so called.
FIG. 1 20. A TELEGRAPH KEY
FIG. 121. A REPEATING SOUNDER
FIG. 122. A CELL OF
DRY BATTERY
" We must run our
The coils of its magnets are vertical. Thearma- wire along the walls
tare is fastened to the horizontal ter which from one station to
moves as the armature moves and clicks against
the point of the little screw above it. another like this I "
wire
Push
Button
Battery
Bell
wire
FIG. 123
FIG. 124. A PUSH BUTTON
It is like a very simple telegraph key.
When you push it two ends of the wire
are connected so that the current from
the battery can flow to the bell and ring
it. Until the button is pushed the
circuit is broken and the current can-
not flow. If you should take away
the push button and join the ends of
the wire where it now is, the battery
current would flow continuously and
the bell would ring all the time.
FIG. 125. AN ELECTRIC BELL
When the push button is touched the cur-
rent from the battery flows along the
wire into the box and round the coils
shown in the picture. So long as the
current is flowing the soft iron inside
the coils is a magnet and attracts the
piece of iron which is -the hammer (K)
of the bell (T). But this piece is a vi-
brating spring and it keeps moving to and
fro and sounding the bell. The moment
that the push button is released the cur-
rent stops flowing and the bell stops
sounding.
136
FIG. 126. AN ELECTRIC-BELL OUTFIT
COMPLETE
It can be bought in this form with seventy-five
feet of wire and staples to fasten the wire for
about $2.75.
Grou.ntL Wire,
Line Wire.
FIG. 127. THE TELEPHONE
F is a handle ; turn it and the bell (G) will ring on your
telephone and also at the other end of the line. The
man you wish to talk to will hear it. He has another
instrument just like yours. Take down your tele-
phone (B) and put it to your ear. Speak into your
transmitter (C) and he will hear you in his tele-
phone. When he speaks into his transmitter you
will hear him in your telephone.
to Battery
137
138
THE SCIENCES
The Mariner's Compass. "You know that a magnetized
needle points north and south," said Jack. " A compass needle
will point to the north no matter to what part of the earth you
FIG. 128. THE TELEPHONE
One view shows the telephone as it really is ; the other as it would look if it were split down
the middle so as to show what is inside. A is a long steel magnet wound with fine
wire (B). The ends of the spool of wire (B) are connected to the outside posts (D,D).
Close to the magnet yi(near B) there is a thin iron plate (EE) which vibrates so as to
copy the voice of the person speaking to you. That person speaks into his transmitter.
(See Fig. 127.) The vibrations of his voice make vibrations in the disk of his trans-
mitter ; these vibrations are sent along the telephone wire and come to your telephone ;
there they make the disk (BE ) of your telephone vibrate just ,as his voice vibrated ;
the disk (EE) makes the air in your telephone vibrate like the speaker's voice, and
you hear him speak.
take it. The reason is that a current of electricity is flowing
round and round the earth all the time and that any magnet
will always arrange itself at right angles to a current, if it can.
PHYSICS
139
The fact is so, and I am going to prove it." So Jack took
one of the little magnetized needles (Fig. 1 1 5) and let it
FIG. 129. THE MARINER'S COMPASS
swing freely. It swung so as to point to the north and
rested in that direction, thus :
-> North
FIG. 130
Then Jack took the two ends of the wire from his battery
and made them parallel to the needle, being careful not to
touch the ends together, this way:
> North
AB
Copper
Zinc
'
Battery
FIG. 131
140 THE SCIENCES
No current was flowing, and the needle remained as it was
before. Then he joined the ends A and B. A current flowed
through the wire, and immediately the needle moved round and
pointed west and not north (Fig. 132).
"You see," said Jack, "the needle moves so as to be perpen-
dicular to the direction of the current. A current is always
flowing round and round the earth from east to west. The sun
makes the current. The compass needle is always perpendicular
to the direction of the current, and that is why the mariner's
compass points to the north. It is a good thing for us that it
West
Copp.
er Zinc
Battery
FIG. 132
does so. Sailors can make long voyages and always know
which way is north whether the stars are shining or not.
They do not need the north star any more."
The Electric Light. The first electric light was made about
a hundred years ago by using a battery of 3000 cells. (See
Fig. 105.) The wires from the ends of this immense battery
were brought close together, and the spark between the ends
did not come and go as lightning does, but was steady, like
our electric , street lamps. The current from so many cells
made a great heat as well as a brilliant light. The ends of the
wires were melted off where the light was produced, and they
o-w
'
H -
.
SS'S'.SS 3 ';
^rc 3 ^rc
;s*i
S 3 ; * S
& J
the sea. It is quite likely that the Oconee when they are in flood. The
River will capture more of the Chattahoochee Yellow River in China has
waters in times to come.
drowned a million persons in
a year (1887); the Ganges is nearly as bad; and our own
Mississippi has terrible floods.
Fred. Anyhow they don't mean any harm, and they are
industrious ; they do the best they know how.
Jack. Industrious they certainly are. In the first place, the
water dissolves a great deal of rocky soil (just as water dissolves
sugar) and carries it along to a new place. Then a river carries
a great deal of sand and mud in its stream, and drops that, too,
when it can carry it no longer.
PHYSIOGRAPHY
197
Agnes. When does it drop the mud, Jack; when it gets tired ?
Jack. You might say so. While the river is flowing fast it
can carry a great deal of mud and sand ; as soon as it begins
to move slower some of this mud falls to the bottom.
Tom. If you want to get dirt out of a wash basin, you have
FIG. 178. THE TOWN OF EMS (PRUSSIA) BUILT ON THE NARROW
FLOOD PLAIN OF THE LAHN RIVER
to make the water move quickly. If it moves slowly, the dirt
begins to settle.
Jack. They say that the Mississippi carries mud enough every
year to make a range of hills a mile long, half a mile wide at
the bottom, and five hundred feet high; and the Nile brings
huge quantities of soil into lower Egypt. The flood plains of
such rivers are the most fertile parts of the world.
I 9 8
PHYSIOGRAPHY
199
The Land. "When people talk about the sea," said Jack,
" they speak about it as if it were always changing they call it
* the restless sea ' ; and when they talk about the land they
speak as if the land never changed at all * the everlasting
hills,' they say. Of course it is true that the hills and moun-
tains do not change much in your lifetime or in mine, and of
FIG. 180. A MOUNTAIN RANGE IN CALIFORNIA
The summits are covered with snow which, melting, forms the brooks and rivers ; rains model
the ravines. Every feature of this landscape has been formed by running water.
course it 's true that if you are at the seashore the waves are
never still for a moment ; but really and truly the land changes
more than the sea does, if you take the whole history of it.
The surface of the land is changing all the time."
Mary. I don't quite see how, Jack. I have been here all
summer. What changes have there been?
200 THE SCIENCES
Jack. You have seen the brook to-day. What color was the
water, Mary ?
Mary. Why, it was clear.
Jack. And yesterday, when it was raining so hard, what color
was it ?
Mary. It was muddy. Yes, I see; the rain from the ground
carried off some of the soil to the brook. It was not much,
though.
Jack. No, not much. But suppose you have a hundred
showers every year; in a hundred years there will be ten thou-
sand showers, and every shower will do some work and will carry
away some soil. In a hundred centuries there will be a million
FIG. 181. SAND MOUNTAINS (DUNES) IN THE RAINLESS DESERT OF
THE SAHARA
They are modeled by the wind. Along many seacoasts such dunes are to be found.
showers ; every one of them will do some work, and all of
them together will do a great deal. They will sculpture
mountains and level continents.
Mountains. "Nearly all the mountains of the globe are
modeled by water. Wherever there is frost, too, great pieces
of rock break off and fall. The shapes of mountains in arid
countries like Arizona are modeled by the winds ; and then,
PHYSIOGRAPHY
2OI
you know, there are volcanoes, and they change their shape,
too. Everywhere the form of the land is changing."
Tom. If all this went on long enough, the earth would be flat.
Agnes. You might say more than that, Tom. You might
say that the rains would
make all the mountains flat,
and that the rivers would
carry everything to the sea.
Why does n't that happen,
Jack? Why isn't all the
land carried into the ocean ?
Why is n't the whole world
flat?
Jack. If you gave it time
enough, it would be, Agnes ;
but it would take a great
deal of time ! The books
say that the surface of a
whole continent might be
lowered an inch or so in a
century. North America
is, on the average, about
2000 feet (that is 24,000 inches) above the ocean, so you
see that it would take at least 24,000 centuries to level it
at least 2,400,000 years. But long before that time other
things would happen to prevent. Some of the continents
are slowly rising out of the sea all the time, and it is the
elevation of whole countries that makes up for the washing
away of the land.
Tom. I never heard of that before, and I don't understand
it. What countries are rising now, for instance ?
FIG. 182. A CLIFF OF HARD ROCK
The sloping bank at its foot is made up of rock
that has fallen from the cliff.
2O2
THE SCIENCES
Jack. Well Sweden is rising, slowly rising, two or three feet
in a century. And the northern coast of California is rising, and
many other coasts and regions, too. They say the coasts of
Alaska and of Peru have been raised more than a thousand feet.
Agnes. Aren't some regions sinking?
Jack. Yes, of course. If one region rises, others will sink.
They say the coasts of Massachusetts and of New Jersey are
now sinking about
two feet in a hundred
years; and there are
plenty of other places,
too, but I don't re-
member them now.
Agnes. But, Jack,
how can people pos-
sibly know that a
country is sinking, if
it moves as slowly as
that ? Two feet in
a hundred years
why, how can they
tell ?
Jack. Well, it is not easy, but there are ways to do it. If
the sinking keeps on long enough, it is not hard to observe it.
For instance, there is a part of the German Ocean not far from
the mouth of the Thames where the whole coast has sunk.
They say you can even see the remains of buildings at the
bottom of the sea when the water is clear. Those were
English cities, and the land has sunk within a few hundred
years. We know the history of it, I believe. There is a very
good way to tell, though, what land has risen out of the ocean.
FIG. 183. FOSSIL SHELLS IMBEDDED
IN LIMESTONE
PHYSIOGRAPHY
203
Tom. What way, Jack ?
Jack. By seashells - fossil seashells found on land, even on
mountain tops. Suppose you should find, not one, but thousands
and thousands of seashells on the very top of a hill ; suppose that
the whole rock should be made of them. Well, would n't that
prove that that particular hill had once been under the sea ?
Tom. Yes, you could prove it that way.
Jack. Now suppose that all the hills for hundreds of miles
around were made of shells of shells of animals that we know
FIG. 184. THE UPLAND OF NEW ENGLAND WITH MOUNT MONADNOCK
IN THE DISTANCE
cannot live on land, but absolutely must live in salt water
would not that prove that the region had been under salt water
long ago ?
Tom. Yes, of course. Are there many regions like that?
Jack. Hundreds of them. And in some of them every bit
of the rock is filled with seashells. You know what sandstone
is, of course ?
204
THE SCIENCES
Tom. Yes, there is a lot of it here. Some of our hills are
all sandstone.
Jack. Well, sandstone is nothing but little grains of sand
cemented together to make rock; and many sandstones have
been formed under water under salt water. A large river,
let us say, brings sand from the shore, and drops the sand
FIG. 185. A MOUNTAIN IN UTAH FILLED WITH RAVINES, EVERY ONE OF
WHICH HAS BEEN MODELED BY RUNNING WATER
grains on the sea bottom. In time the grains are cemented
together, and then you have layers of sandstone. By and by
something like a great slow earthquake happens, and the sand-
stone is lifted above the sea. It may be lifted, in time, very
high. Then you have layers of sandstone on land. The rains
come and wear it into ravines, and parts of it crack and fall, and
some of it is covered with soil by the washings of other rivers,
PHYSIOGRAPHY
205
and by and by trees and grass grow there, and you have a
country like the one we live in.
The earth is not solid down to its center, you know. We
live on the outside crust of it. That is solid, of course, and
it is about a hundred miles thick. Inside of that crust great
parts of the globe are red-hot rocks, like melted lava. It is as
if the continents and the oceans were resting on an inside globe
of melted rock. The heaviest parts are always pressing down,
and the crust is always being strained
and bent and cracked. Some parts
of the earth are sinking very slowly,
and other parts are slowly rising.
Wherever the crust moves you have
cracks, and when the cracks are large
you have long valleys and mountain
ridges. (See the picture, Fig. 188.)
Stratified Rocks. " Are all moun-
tains made in that way, Jack ? " said
Tom.
Jack. Not exactly in that way, Tom.
You see it is like this : The crust of
the earth sometimes breaks one way,
and you have mountains like those in
the picture (Fig. 188) ; and sometimes
it does not break at all, but bends ; it may be pressed or
crumpled so slowly that it can yield without much breaking.
There is a way to prove this. Do you know what stratified
rock is ?
Tom. It is rock in layers in strata.
Jack. Yes. Now we know that those layers were, in the first
place, horizontal. They were layers of sand on the bottom of the
FIG. 1 86
The earth's solid crust is about
100 miles thick ; the narrow line
in the picture would be more
than 100 miles thick if the diam-
eter of the circle were 8000
miles. Within the crust the
rocks are very hot melted.
The pressures in the interior are
so great that the rocks, though
melted, do not flow like a liquid,
but are almost rigid, like a solid.
FIG. 187. MODEL TO SHOW HOW MOUNTAINS ARE MADE BY THE
CRACKING OF THE EARTH'S CRUST
FIG. 188. VIEW OF THE MOUNTAINS FORMED BY THE CRACKING OF THE
EARTH'S CRUST. (SEE FIG. 187.)
They are in southern Oregon and northern Nevada and California. The long lakes and
the streams lie in the direction of the cracks.
206
PHYSIOGRAPHY
207
sea, or perhaps they were layers of limestone with fossil shells
scattered through them. In the pictures (Figs. 182 and 189)
FIG. 189. A COLUMN OF STRATIFIED ROCK
The rock is made up of nearly horizontal layers. The softer rock between the column and
the cliff has been worn away by the waves in the course of thousands of years. Fig. 182,
preceding, shows a cliff of stratified rock of rock arranged in layers.
they have been lifted up so as to keep the layers level ; but
there are places, many places, where the layers have been
crumpled like this:
(See also Fig. 190.)
208
THE SCIENCES
The crumpling makes the crust into mountains and valleys,
and you must always remember that just as soon as a moun-
tain is lifted up, it begins to be torn down again by the frosts,
the rains, the earthquakes. The older the mountain is, the
FIG. 190
Strata once horizontal are sometimes elevated and folded so as to make mountain ranges, as
in the picture, which shows such a case in Maryland. The Appalachian ridges in Penn-
sylvania (and the Jura Mountains in Switzerland) were made in this way.
more its first shape has been altered, and you can tell its age
in that way. (See Figs. 180 and 185.)
The oldest mountains in America are the Laurentian Hills,
near the St. Lawrence River, and the Green and Adirondack
mountains. The Green Mountains are about forty or fifty
million years old, the geologists say.
PHYSIOGRAPHY 209
Fred. What are the youngest mountains, Jack ?
Jack. The youngest in America are the Coast Ranges of the
Pacific slope. The books say they are about two or three
millions years old. Two million years is young for a moun-
tain. The Wasatch Mountains in Utah are middle aged.
The Age of the Earth. " Do they know how old the earth
is ? " said Tom.
Jack. It is not known in the way you can say you know how
old a tree is after you have counted the number of rings in its
sawed-off stump ; but it is known in a way. Take these very
stratified rocks, for instance. They were formed under water
by sand which settled down on the ocean floor and slowly
cemented into rock. A layer a foot thick will be formed in
about 10,000 years, the geologists say. Then a layer 100 feet
thick might be formed in about a million years, and a layer
ten miles thick in about 500,000,000 years. There is good
reason to believe that the earth is at least as old as that, and
maybe older. 1
Agnes. Five hundred million years ! I shall never be able
to realize that ! Why, I can't even understand what a million
years is.
Jack. You remember how you children made a model of the
solar system ? 2 It helped you to understand large numbers,
did n't it ? Well, you can do something of the same sort here.
Suppose that the next time you walk to the village you play
that every one of your steps counts for a year. When you
1 There is no part of the earth where we can see horizontal layers, one upon
another, ten miles thick ; but there are places where the layers, once horizontal
( ), have been tilted up (//////), so that we can now see their ends and be
sure that the original layers were at least ten miles in thickness.
2 See Book I (Astronomy), page 20.
210 THE SCIENCES
have taken 125 steps you have gone back 125 years, and that
will take you back to the time of the Revolutionary War
(1901 1776= 125); and when you have taken 1900 steps you
have gone back to the time of Christ. When you have walked
three miles you have gone back to the time when the first
pyramids were built. You would have to walk about twenty
miles, each step counting for a year, before you got back to the
time when human beings first came on the earth; and you would
have to walk two or three times round the earth before you got
back to the time when the first life appeared on the earth, and
much farther yet to get to the time when the earth was first
formed.
Mary. It is puzzling, but I think I understand it a little
better than I did before.
Jack. Well, my dear, suppose you remember what we have
said and think about it by and by. Recollect a step stands
for a year ; you were born twelve years ago twelve steps just
takes you out on to the lawn. The Pilgrims landed 281 years
ago 281 steps down the road. You can put a peg here to
stand for the coming of the Pilgrims. Eight hundred and
thirty-five steps will take you to the landing of William the
Conqueror in England; put in a peg for him. A mile will take
you back to 600 years before Christ ; the city of Rome was
founded about that time. Two miles farther will represent
the time when the pyramids were built in Egypt ; and when
you have gone about twenty miles a year to each step you
will get back to the time that men first appeared on the earth.
That is far enough for now. The world was a very old world
when Man appeared on it ; it had a long history before he came.
There had been life long before his time, as we know by the
fossils, shells, fishes, and animals ; and there was a long time,
PHYSIOGRAPHY 2 1 1
nobody knows how long, before that when the earth had no
life on it at all no men, no animals, not even a plant.
Age of Different Parts of the Earth. "I understand how
you can tell when the oldest seashells came," said Tom,
"because you would find their fossils in the oldest rocks in
the rocks lowest down ; and if you find a fossil rhinoceros
higher up in the rocks than a fossil whale, you would say the
whale came first. But how about men ? Do they find fossil
skeletons of men ? "
Jack. Sometimes ; but more often they find arrowheads that
men have chipped out of flint, along with the fossils of animals.
For instance, there are caves where arrowheads and lanceheads
have been found along with the remains of animals, and where
it is plain that the caves were filled up by some accident soon
after the men had died ; those men and those animals lived at
the same time. Sometimes they find the bones of the animals
split open, so as to get the marrow out, and blackened
with fire.
Age of Man on the Earth. " Well, that would prove that
the men used those very animals for food, would n't it ? "
said Fred.
Jack. Yes, and there is a more wonderful thing still. In one
of the very old caves they found bones carved with pictures of
reindeer. The man first killed the reindeer with his arrows,
and dragged him to his cave and cooked him with fire. Then
there was plenty of food in the house. The man felt secure
and happy; he had leisure to think and to enjoy himself. And
this drawing of a reindeer on a bone made by a half-naked
savage is the beginning of all the beautiful pictures in the world.
The man was, you may say, our ancestor ; and the drawing is
the ancestor of all the paintings of modern times.
212
THE SCIENCES
Tom. Some one ought to put up a monument to that man !
He was, the first artist long before Pheidias and the Greeks.
Agnes. How long before, Jack ?
Jack. I knew you were going to ask me that, Agnes. I
was sure of it ! Well, at a guess, 10,000 years or, it may be,
1 5,000. It is not certain, like the date of the last eclipse, or the
time when Rome was founded. It is twenty miles, Agnes a
year to a step don't you remember ?
Agnes. Yes, I remember ; but I don't see how you can tell,
though.
Tom. Why, Agnes, if a man eats reindeer in order to live,
he must be at least as old as the reindeer, must n't he ?
Agnes. Of course.
Tom. And if the fossil reindeer are found in rocks that it
took 5000 years at least to make, then the man must have
lived at least 5000 years ago. That is the way they find out.
Jack. That is the way
they find out, yes, Tom ;
but you must remember
that just about 5000 years
ago, in Egypt, men were
building palaces and tem-
ples and pyramids, writing
letters to each other, keep-
ing accounts, spinning and
weaving, painting, and
FIG. 191
making statues. You have
to go back at least 100,000
years to find the earliest men. Agnes, there is a place in
the West Idaho or California, I forget which where they
lately found something very like a doll ; it might have been
PHYSIOGRAPHY
213
an idol, but it looked like a doll. Now this doll was buried
in gravel that had been brought down by an old-time river.
No one knows exactly how long it took for the river to
bring down all the gravel that covered the place where the
doll was dropped by the man who had it, but it must have
taken thousands of years. Then,
long afterwards, the volcanoes near
by sent out rivers of lava, and thick
sheets of the lava poured out and
covered the old gravels and dried up
the old river. No one knows exactly
how many thousands of years it took
for the many sheets of lava to form
one above another ; but they were
more than half a mile thick that
we know. Then came a new river
flowing across the lava, and it flowed
for so many thousand years that it
cut a deep groove for its bed in the
hard lava. Scientific men can make
a pretty good guess how long each of
these different things took. Some
men were sinking a deep well in the
valley of the new river the other day,
and in the well, deep down, they found
the doll. You see that we can make
a pretty good guess how long ago the doll was made by adding up
all the years that were required to deposit the gravel, and to make
the lava sheet, and for the river to cut its way in the lava.
Agnes. Yes, I see. I suppose that is certainly the oldest
doll in the whole world, though.
FIG. 192. A GEYSER SPOUT-
ING BOILING WATER WHICH
COMES FROM DEEP DOWN IN
THE EARTH
214
THE SCIENCES
The Internal Heat of the Earth. " You were saying," said
Tom, "that the interior of the earth is made of melted rock.
I suppose you know that by the melted lava which comes from
volcanoes. Lava is melted rock."
Jack. Yes, it is known in that way : volcanoes pour out melted
rock. And then geysers send out hot water boiling water
sometimes ; and in regions where there are no volcanoes we
FIG. 193. THE PEAK OF TENERIFFE IN THE CANARY ISLANDS
The mountain is 12,000 feet high, and its beautiful form has been shaped by the lava streams
flowing down from the crater. Notice that the rocks in the foreground form part of a
very much larger crater that was active in ancient times and is now extinct.
find that the deep wells always send out hot water the
deeper the well, the hotter the water.
Fred. How deep are the deepest wells, Jack ?
Jack. There are some in Europe nearly a mile deep. They
are not dug, you know, but are sunk by boring. There
are deep wells in America, too ; one in St. Louis is 3800 feet
deep more than two thirds of a mile. The water from it has
a temperature of 105. Boiling water is 212, you know.
PHYSIOGRAPHY 215
Volcanoes. " You know there are some splendid volcanoes
in Hawaii," said Jack; "papa' has seen them. One of them
especially is easy to visit Kilauea, 1 they call it. It is a great
lake filled with red-hot boiling lava that comes up from some
reservoir of lava deep in the ground. The lava is liquid rock.
Usually it does not flow over the rim of the crater, but sometimes
it overflows and sends great streams of red-hot lava all over the
country round about and even as far as the sea fifty miles off.
FIG. 194
A volcano is built up somewhat as in the picture. Underneath it are old rocks in layers.
There is a reservoir of lava somewhere underneath them, and a pipe filled with lava
leading to the surface. (The lava is colored black in the picture.) When the lava overflows
it moves down the side of the mountain like a great river and covers up everything that
comes in its way. The upper end of the pipe is the vent, and the lake at the top is the
crater. There is often more than one vent. (See the little black lines in the picture
leading to different cones.)
" Vesuvius, near Naples, is the most famous volcano. You
know it buried two whole cities once Herculaneum and
Pompeii." 2
Agnes. Tell us, Jack.
Jack. Pompeii was a kind of summer resort where the
Romans used to go for pleasure. It was a pretty little town
full of fine houses, temples, shops, and so forth, not far from
1 Pronounced ke'-lou-a'a.
2 Pronounced pom-pa'ye.
216 THE SCIENCES
the volcano of Vesuvius. Seventy-nine years after Christ
(A.D. 79) there was a great eruption, and the ashes began to
fall on the city. At first the people were not very much
frightened, but pretty soon things got worse and worse, and
they began to gather up their movables and to leave the city.
A great many of them got away, but hundreds and hundreds
were buried in the ashes and died there. The ashes kept on
falling for days, and the whole city was covered up. Almost
the same thing happened in Martinique in May, 1902. Just
imagine what might happen if there were a volcano near New
York, and if the city were to be covered up with a thick layer
of ashes and not even found again for more than a thousand
years !
Agnes. Not found for a thousand years !
Jack. Well, Pompeii was buried in A.D. 79, and it was not
until 1748 that people began to dig there and found the whole
city complete, just as it had been left a good deal more than a
thousand years before.
In a baker's shop, for instance, they found loaves of bread
all shriveled up, and perfumes and oil and jewelry in other
shops. The houses were filled with things that the people
used every day ; everything was just as before.
Agnes. But the people, Jack were they found ? Were their
bodies found ?
Jack. Their bodies had mostly wasted away, Agnes ; they
found their skeletons. One man had come back after his
money, and other people after their jewels. The money and
jewels were found, and the bones of the persons near them.
In one place they found a picture of a watchdog with the
sign, Cave canem ; that means what does it mean, Tom, in
English ?
PHYSIOGRAPHY
217
Tom. It means " Beware of the dog !"
Jack. Yes; as we should say "Look out for the dog!" A
very great deal of what we know about ancient pictures and
statues we learned from Pompeii.
Fred. If New York were buried and dug up a thousand years
from now, the people of that time would know how we lived.
FIG. 195
The picture shows the volcano of Vesuvius as it appears to-day, and in the foreground a part
of the city of Herculaneum after the layer of lava has been taken off. Herculaneum
was covered with thick ashy mud and was even better preserved than Pompeii, which
was buried in showers of ashes. Everything in it was found exactly as it was left
shops, houses, temples, jewelry, tools.
Tom. If you went into a house, you would know just what
each room had been used for the kitchen and the dining
2l8 THE SCIENCES
room and the bedrooms and just what pictures we had liked
and hung on our walls, and what books we read, and everything
of that sort.
Mary. And they would know what games we played tennis
and golf ; and they might find Agnes' dolls and mine.
Agnes. Just as we found the doll Jack told us about that
was buried under the lava in California.
Fred. Are there any volcanoes in the United States ?
Jack. There are plenty of mountains that are old worn-out
volcanoes, and a few that are still active. Mount Shasta, for
instance, in California, is an old volcano, and there are active
volcanoes in Alaska, Hawaii, and the Philippines. You children
ought to recollect, every time you look at a map, that a very
large part of three great states Washington, Oregon, and
Idaho is nothing but an old lava field. A good part of the
lava is 3000, even 4000 feet thick, and it covers thousands and
thousands of square miles. All that lava flowed from ancient
volcanoes, though it did not flow all at one time; for they
find the lava in layers with ashes and soil between, and in
some of the soil they find petrified tree trunks.
Tom. That shows the trees had time to grow between one
lava flow and the next one, does n't it ?
Jack. Yes, and it gives you an idea how long it took to
deposit all that thickness of lava. The doll I told Agnes
about was found in this very lava field.
Earthquakes. "Do earthquakes come from volcanoes?" said
Fred.
Jack. There are always earthquakes wherever there are
active volcanoes, Fred. You can see that a volcano in eruption
which has energy enough to throw huge stones thousands of
feet into the air must shake all the ground near it by its
PHYSIOGRAPHY 219
explosions. All volcanoes make earthquakes, but very many
earthquakes are not caused by volcanoes.
Mary. What does cause them then, Jack ?
Jack. Suppose you lay a book flat on its side, Mary, and
imagine that the book is part of a layer of rock that was once
deposited at the bottom of the sea. Now take another book
and lay it flat on the first one. That stands for a second layer
of rock perhaps a different kind of rock lying over the
first layer. Now you know the crust of the earth is moving
slowly all the time, sometimes up, sometimes down. Sup-
pose both those layers of rock were lifted so that one end of
them was higher than the other. Tilt the books, Mary, and
keep tilting them, and see what happens.
Mary. Why, one book slides off the other. 1
Jack. That is exactly what sometimes happens to great beds
of rock. They lie flat in the first place. Then they are slowly
tilted, and by and by one of them slides a little a very little
on the other. Ten million tons sliding only a little way
an inch perhaps will make a terrible shock that can be felt
for hundreds of miles around. The Charleston earthquake
was caused in just that way.
The geologists say that the layers of rock underneath South
Carolina lie one on another like the two books, and the earth-
quake was caused by the sliding of the layers. The rocks I am
talking about were deep underground, you know. When they
moved, the rest of the rocks moved, too, just as a pile of bricks
will slide when you move some of the bottom ones ; all of
them moved. A good part of Charleston was wrecked, you
know, and all the eastern part of the United States was shaken
1 The simple experiment should be tried in the schoolroom, choosing two
books with smooth covers.
22O
THE SCIENCES
more or less. Why, they even felt the shock at Boston, at
Toronto in Canada, at Chicago, at St. Louis, and at New
Orleans. The shock was not severe there, but it was felt.
FIG. 196. THE CHURCH OF SAINT AUGUSTINE IN MANILA, PHILIPPINE
ISLANDS, AFTER THE EARTHQUAKES OF JULY, 1880
Tom. Of course an earthquake is weaker and weaker the
farther you go away from the center of it.
PHYSIOGRAPHY
221
Jack. Yes ; like the little water waves in a pond when you
throw in a stone. That is a " waterquake," you might say.
You know the waves are larger and higher at the center, and
FIG. 197. VIEW OF PART OF CHARLESTON, S.C., WRECKED BY THE
EARTHQUAKE OF AUGUST, 1886
become smaller as they move out. All of South Carolina was
badly shaken, so that chimneys fell. The shocks were strong
enough to frighten people in Georgia, in Ohio, and in
222 THE SCIENCES
Pennsylvania, and they were felt as far as the Mississippi
River, and farther.
Mary. Were many people killed, Jack ?
Jack. Only a few, Mary. They ran out of their houses, and
lived in the parks for several days till the shocks were over.
Agnes. Oh, did the earthquake last for days ?
Jack. There were shocks every now and then for several
days, but only a few really severe ones. You see it took
several days for all those rocks underground to settle down and
be quiet. There was an earthquake in the Mississippi Valley
once (181 1) that lasted nearly a year. The people camped out
of doors for months and months.
Agnes. Might we have an earthquake here, Jack ?
Jack. Certainly, we might ; no one can tell. There are not
many earthquakes in the eastern part of the country, and those
that we have are usually light ; you need not be afraid of
them. If an earthquake comes, go out of doors and keep away
from houses that is all. But there are earthquakes every-
where light ones. You boys can prove it if you want to.
Fred. How can we prove it ?
Jack. Get some pieces of nice wood red cedar, for
instance and make two or three pyramids. (See Fig. 198.)
Then cut off a little of the top of each one of them, and stand
them upside down in a steady place on the mantelpiece of a
room that is not used much, for example. When a slight earth-
quake comes one too slight for you to feel perhaps the
house will be shaken and the mantelpiece, too, and the pyramid
will fall on one of its sides. Try it.
The boys did try it. They made half a dozen pyramids
and cut off a little of the top of each one, and stood them
about in different places in the house and in the barn. They
PHYSIOGRAPHY 223
often would find one of them fallen on its side, and they
usually discovered that the housemaid, in dusting, had caused
that particular earthquake. But every few months they found
all the little pyramids thrown down, and most of them lying in
one direction ;*and then they knew that there had been a light
shock too light for them to feel, but strong enough to over-
turn their " earthquake detectors," as they called them. The
FIG. 198. PYRAMID
direction in which the detectors lay on their sides showed the
direction in which the earthquake wave was moving north
and south, for instance.
The Lisbon Earthquake. "They say the Lisbon earthquake
was one of the very worst," said Tom ; " do you know about
that, Jack?"
Jack. It was one of the worst, certainly, because there was
not only an earthquake, but a great sea wave too. The people
ran out of their houses to take refuge in the churches, and then
the churches fell and crushed them. Many went to the wharves
224 THE SCIENCES
so as to be away from falling walls, and a huge wave from the
sea eighty feet high, they say rolled in and drowned
thousands of people.
Fred. A wave eighty feet high ! What made it, Jack? Was
it a part of the earthquake ?
Jack. No doubt the level of the sea bottom was changed some-
how, and the water rolled in like a great wall. That often occurs
in South American earthquakes. A strange thing happened
to one of our war vessels once. It was the Wateree, and she
was at anchor in the bay of Iquique 1 in Peru (1868). All of
a sudden came a great wave from the sea and tossed the
ships about like boats, and it carried the Wateree far inland
and left her there high and dry. Think of it one of our war
ships with all her guns and men (no one was hurt) high and
dry on land !
Fred. What did they do ? Could they get her off ?
Jack. No ; and so the government took away all her cannon
and everything that was valuable, and sold her to a Spanish
gentleman for a summer house !
Agnes. I think that 's funny. A man-of-war for a summer
house !
Jack. That is not the funniest part of it, Agnes. A few
years later there came another great sea wave, and it lifted up
the Wateree and carried her a long way farther inland, and
there she is now, a summer house for a different family.
1 Pronounced e-ke'ka.
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