fflMWMMMMlii
THE MARCH
•g-
From the collection of the
z n m
o PreTinger
Jjibrary
San Francisco, California
2006
Photo by Warren Boyer, Westport, Conn .
It is a great thing to have a hobby. These boys have formed a field club and
are off on a collecting trip.
THE MARCH OF SCIENCE
MY OWN
SCIENCE PROBLEMS
GEORGE W. HUNTER, Ph. D.
Lecturer in Methods of Education in Science
Claremont Colleges, California
Formerly head of the Department of Biology,
De Witt Clinton High School, New York
AND
WALTER G. WHITMAN, A. M.
Department of Physical Science, State Teachers College
Salem, Massachusetts
Foundei and Editor of General Science Quarterly
now Science Education
AMERICAN BOOK COMPANY
NEW YORK CINCINNATI CHICAGO BOSTON ATLANTA
COPYRIGHT, 1935, BY
AMERICAN BOOK COMPANY
All rights reserved
MY OWN SCIENCE PROBLEMS. H. & W.
W. P. 6
MADE IN U.S.A.
FOREWORD TO THE TEACHER
Education in a Changing World. Great changes in
educational methods and objectives have recently taken
place. The growth of the junior high school is an experi-
ment in education brought about through a desire on the
part of educators to integrate the work of the elementary
school with that of the high school. The growing empha-
sis on secondary education has forced these changes in
organization. Along with this has come a new psychology
of learning which emphasizes individual learning rather
than group teaching. As a result of these changes in
ideals and objectives, the curriculum has come into the
limelight. Much recent work has been done in curriculum
making, and while some has been scientifically made some
is of little value. There is much evidence that the newer
curricula in science are being made with objectives that
are attainable. Changes in the world of today have been
brought about by means of science, and some seventh
grade pupils of today know more about some of the
applications of science than their fathers do. There is
need for interpretation of these changes in terms of the
child's activities, especially in terms of his leisure-time
activities. The modern science curriculum recognizes
this.
If we consider what has just been said, it would seem
that the underlying philosophy of the course should be
based on the relationship of the environment to the child ;
first as an individual, and later as a growing citizen in the
environment of school, community, and nation. Into
such a course the materials of science should be integrated
with the curricular materials of geography, history, civics,
vi FOREWORD TO THE TEACHER
and especially health education. At the earlier levels
the ultimate outcomes from the child should be the organ-
ization of the integrated knowledges in such a way as will
make for some first-hand experiences with the factors of his
environment and an understanding of the part played by
such factors in his life activities — a desire to know more
about and to help in the improvement of his environment ;
while at the highest grade level of the junior high school
understanding of control and usage of the factors of the
environment might well be the ultimate aim. This
integration, especially of positive health materials, has
been made in the pages which follow.
To properly present learning elements in an integrated
science curriculum at different grade levels, it is obvious
that the mental age, and especially the point of view of
the pupil, must be carefully considered. A terraced plan
of attack must be used in which the capacities, interests,
and science backgrounds of the seventh grade child must
be considered as a distinct level in the development of the
concepts treated in the course. Children grow much in
capacity between the seventh and ninth grade levels. At
the seventh grade level the teacher must use simple
language. The science vocabulary should be restricted
to the use of relatively simple terms. The experiments
and demonstrations should be easy to understand and to
perform. The teaching techniques should all be adjusted
to the levels of the immature youngster of this group.
At the eighth grade level, after a year of exposure to the
junior high school activities, our boy or girl comes back to
school in the fall with a perspective much enlarged and
with a social viewpoint quite different from that held in
the previous year. The instruction at this level and the
quality of work will therefore be not only at a higher
terrace of difficulty but should be given from quite a
different social point of view.
FOREWORD TO THE TEACHER vii
Classroom psychology and teaching procedures have
shown that while the pupil in seventh grade is an individ-
ualist, the same pupil at the eighth or ninth grade level
has a quite different outlook on school life. He has be-
come a school citizen with the responsibilities of citizen-
ship as a part of his mental outlook. It would seem very
logical therefore to make our seventh grade science center
on the individual and his personal reactions to his envi-
ronment by integrating his science interests, leisure-time
activities, and health education material with the science
concepts fundamental to an exploratory knowledge of his
environment. On the other hand, as the ideals of citizen-
ship and co-operation are developed at the eighth grade
level, it would seem logical to make science concepts lead
to a better understanding of such problems as are con-
cerned with the purity of water supplies, the protection
of food supplies, the control and prevention of disease in
the community, and such other science topics which show
the need for co-operative effort for environmental improve-
ment on the part of school children. As the outlook of
the child broadens in the third year of the junior high
school, a third cycle of science activities will develop at
a still higher terrace of difficulty. At this age level the
child might well transfer his science interests to the wider
field of the nation and the world.
The underlying theme for junior high school science
should be first, at the lowest level, simple knowledges
about the interesting and useful science in the immediate
environment of the individual. In the second year under-
standing is more the goal, while in the last year interpre-
tation and application of science are the desired outcomes.
The philosophy of presentation should result in the ulti-
mate generalization that man of all the animals is the
only one who can control and artificially change his
environment. As such he has dominion over the earth.
viii FOREWORD TO THE TEACHER
Emphasis in science teaching is coming, more and more,
to be placed on method, on problem solving, and on the use
of science facts in the solution of such simple problems as
are within the pupils' comprehension. Although generali-
zations and fundamental concepts are teachers' goals, they
are not so evident to the pupils. Therefore science courses
must lead the child to see and later to understand the
reasons for many simple demonstrations and experiments
to the end that these understandings will lead to the goal
of forming correct generalizations. Mature generaliza-
tions are not the immediate goal ; it is the forming of
these generalizations through science experiences gained
through the usage of science materials that makes for the
best teaching of science. Moreover, these generalizations
should be so mastered that they may be used by the
student in explaining new science experiences with which
he is continually coming in contact. Thus his knowledge
is made usable and applicable. Science teaching will
never function with the mere learning of generalizations;
they must be used and applied intelligently in other science
situations.
Our coming social group is bound to have more leisure
time, as the economic conditions in the future will doubtless
make for a substantially shorter working day and more
and more time for avocations. The place of science in
the junior high school points primarily to adjustment of
the pupil to his environment so that he may best use
these leisure hours. Science can do much for him in
awakening interests and making hobbies worth while.
Hobbies are important, both for young people and for
older ones : collecting, fishing, hiking, keeping pets,
gardening, anything that makes for intelligent interpre-
tation and use of the environment.
This series of texts has been prepared keeping in mind
not only the recommendations of the most scientific
FOREWORD TO THE TEACHER ix
workers in the junior high school curriculum, but also
such experimental work as is available. Interest studies,
controlled classroom experiments, research studies in the
use of science material, the pooled experiences of teachers,
the work of the Science Committee of the National Edu-
cation Association, and the outstanding recommendations
of the Thirty-first Yearbook have all been used in an
attempt to make this series educationally as well as
scientifically sound.
Certain unique features in the series stand out. In
the first place the texts are written from the pupil view-
point and great care has been taken to present the material
so that it may fit the age level of the pupil. Concepts
grow and what may be meaningful to the ninth grade pupil
could not be understood clearly by the pupil in the seventh
grade, therefore a cyclic plan of treatment is used which is
believed to be psychologically sound. Young people are
interested in the science of the world around them, not in
blocks of a given part of science. As Cox so well says :
" A child of the junior high school age lives in a world of
things, forces, phenomena, and people. He does not live
in a plant and animal world in the seventh year, and in a
health world his eighth year, and a physical science world
his ninth year." l
Emphasis throughout the series is placed on thinking
rather than on the reproduction of facts. Factual mate-
rial is necessary. In this series of texts the factual material
is used in a purposeful way to the end that simple science
problems may be solved. These problems are fitted to
the age level of the pupil so that even in the seventh grade
he may become habituated in the methods used by the
scientist. A conscious effort has been made to give the
pupils reasons why the method of the scientist is useful
1 Cox, P. W. L., The Junior High School Curriculum, Scribner, 1929. By
permission of the publishers.
x FOREWORD TO THE TEACHER
in daily life to the end that a transfer of training may take
place.
The psychology of the unit with its social aspect is a
force which makes for pupil interest and learning. The
Morrison techniques, with modifications which have been
found desirable, are used throughout the series. Empha-
sis has been placed upon learning devices, and a conscious
attempt is made to show the pupil reasons for doing
because of the desirable outcomes in transfer of training.
Cuts and diagrams are presented as learning devices.
The Chinese saying, " A picture is worth 10,000 words,"
showed a deep pedagogical insight. In this text many
pictures are used and thought questions are so worded
that the child will use the text as well as the picture
in trying to answer the questions in the legends. While
the value of the child's recognition of the big ideas and
generalizations in science is seen, the greater impor-
tance of properly arriving at these generalizations has
been stressed in this series. Numerous devices are used
to this end : The Review Summary outline, with its
suggestions to the pupil for the proper method of pre-
paring for the recitation; the practice in problem solv-
ing by means of the presentation of the textual material
in problematic form ; the various types of self-testing
exercises and the many thought questions at the ends of
the units are examples of such aids. In the so-called
" Story Tests" more factual material than appears in the
text is often given, to the end that teacher and pupil
discussion will be stimulated and reading encouraged.
In addition constant use is made of the motivation which
comes through desirable activities such as those obtained
by science clubs and excursions. Leisure-time activities
are also used as a means of stressing interest in learning
science.
ACKNOWLEDGMENTS
It would be impossible to write a series of science text-
books for the Junior High School without mentioning the
many pioneers in curriculum making such as Barber,
Briggs, Carpenter, Charters, Cureton, Cox, Curtis, Frank,
Harap, Pieper, Powers, and many others, including the
committee who were responsible for the curriculum find-
ings in the Twenty-sixth and the Thirty-first Yearbooks
of the National Society for the Study of Education. The
establishment of courses in science at this age level is still
in the experimental stage. But successful courses must
be based on the findings of interest studies as well as suc-
cessful practice of teachers who are practical and pragmatic
in their philosophy of teaching.
The writers of this text have frankly belonged to this
latter school, and the pages which follow are the results of
practical work in the classroom, together with the accept-
ance of such findings in experimental teaching as best
illustrate these objectives. It would be impossible to name
all the teachers who have given help and inspiration to
the writers, but the mention of the following must be
made because of the personal contacts involved : Dr.
Edna Bailey and Dr. Anita Layton of the University of
California ; Dr. Otis T. Caldwell of Columbia University ;
Professor W. L. Eikenberry, State Teachers College, Tren-
ton, New Jersey ; Miss Winifred Perry, Roosevelt Junior
High School, San Diego, California ; Dr. Frank M. Wheat,
Head Department of Biology, George Washington High
School, New York City ; and Professor Herbert E. Walter,
Department of Zoology, Brown University, Providence,
Rhode Island. From each of the above, the writers have
had help and inspiration.
xi
xii ACKNOWLEDGMENTS
The following have read the manuscripts either com-
pletely or in part and have given valuable constructive
criticisms : Edith H. Bourne, the Fannie H. Smith Train-
ing School, Bridgeport, Connecticut ; Francis R. Hunter,
Assistant in Biology, Princeton University; George W.
Hunter, III, Assistant Professor of Biology, Wesleyan Uni-
versity ; Roy A. Knapp, Principal Antelope Valley Joint
Union High School, Lancaster, California; and Frank
M. Wheat, Chairman of Department of Biology, George
Washington High School. In addition Dr. Wheat has
added much to the teaching effectiveness of these books
by his excellent diagrams and skillful cartoons. Wright
Pierce has also added much to the attractiveness of the
text with his illuminating photographs. Professor Francis
B. Sumner has kindly allowed the use of photographs from
an original experiment. Miss Florence E. Wall, F.A.I.C.,
has given valuable suggestions on the hygiene of the skin.
Dean Collins P. Bliss of the School of Engineering of New
York University has offered much technical advice in
certain parts of the text. To all of the above is given the
sincere thanks of the authors.
TABLE OF CONTENTS
PAGE
UNIT I. GETTING ACQUAINTED WITH THINGS. 1
PROBLEM
I. How Do WE GET ACQUAINTED WITH THINGS? ... 3
II. WHAT Is OUR ENVIRONMENT AND How Do WE USE IT? . 11
UNIT II. LIFE DEPENDS ON ADAPTATIONS . 25
I. WHAT ARE ADAPTATIONS AND WHAT Do THEY Do? . . 26
II. How ARE WE FITTED TO LIVE IN OUR ENVIRONMENT? . 33
UNIT III. LIVING IN AN OCEAN OF AIR . 43
I. WHAT MAKES THE AIR USEFUL TO MAN? .... 45
II. OF WHAT IMPORTANCE Is ATMOSPHERIC PRESSURE? . . 52
III. How Do WE USE AIR? 59
IV. How Do WE BREATHE? 67
UNIT IV. WATER AND ITS EVERY-DAY USES . 79
I. WHAT Is WATER? .82
II. WHAT USES Do WE MAKE OF WATER? .... 88
UNIT V. HOW WE USE HEAT . . .103
I. How Is HEAT PRODUCED? . . . . . . . 105
II. WHAT ARE SOME OF THE CHARACTERISTICS OF HEAT? . 109
III. How DOES CLOTHING AFFECT THE HEAT OF THE BODY? . 117
UNIT VI. HOW WE USE LIGHT . . 127
I. How Do I USE LIGHT? 129
II. WHAT ARE SOME OF THE PROPERTIES OF LIGHT? . . 134
III. How ARE PHOTOGRAPHS MADE? 142
IV. How DOES THE EYE RESEMBLE THE CAMERA? . . . 149
V. WHAT Is COLOR? .154
UNIT VII. HOW WE MAY PRODUCE ELECTRICITY
AND MAGNETISM .... 165
I. WHAT CAN MAGNETS Do? 167
II. WHAT ARE SOME WAYS OF PRODUCING ELECTRICITY? . 173
xiii
xiv TABLE OF CONTENTS
UNIT VIII. GETTING ACQUAINTED WITH THE
STARS 187
PROBLEM
I. How FAR AWAY ARE THE STARS? 189
II. WHY Do THE STARS APPEAR TO MOVE? .... 196
III. How TO GET ACQUAINTED WITH THE CONSTELLATIONS . 200
UNIT IX. ROCKS AND SOIL . . . 213
I. How WERE THE ROCKS FORMED? 216
II. WHAT Is THE STORY OF THE FOSSILS? . . ... 220
III. How Is SOIL MADE? 228
IV. WHAT SOILS ARE BEST FOR AGRICULTURE? .... 236
UNIT X. LIVING THINGS IN THEIR ENVIRONMENT . 249
I. WHAT Is BEING ALIVE? 252
II. How Do GREEN PLANTS SOLVE THEIR LIFE PROBLEMS? . 257
III. How Do ANIMALS PERFORM THE BUSINESS OF LIFE? . 266
IV. WHAT LIVING THINGS ARE FOUND IN MY YARD OR GARDEN ? 270
V. LIFE IN STREAM AND POND 281
VI. LIFE IN FOREST AND ON THE MOUNTAINS .... 288
VII. LIFE ON THE SEASHORE 294
UNIT XL THE FOODS WE EAT . . 307
I. WHAT ARE FOODS AND WHERE Do THEY COME FROM? . 309
II. How Do WE USE FOODS? 313
III. SHOULD EVERYBODY EAT THE SAME KINDS AND AMOUNTS OF
FOOD? 326
IV. WHY Do FOODS SPOIL? 333
V. How MAY WE KEEP FOODS FROM SPOILING? . . . 339
UNIT XII. THE HUMAN MACHINE AND HOW TO
CARE FOR IT 351
I. How DOES THE HUMAN MACHINE OIFFER FROM AN AUTO-
MOBILE? 354
II. How Is THE HUMAN MACHINE PROTECTED? . . 359
III. How DOES THE BODY MOVE? 368
IV. How DOES THE HUMAN MACHINE MAKE USE OF FOOD? . 375
V. How Do WE CONTROL THE HUMAN MACHINE? . . . 384
VI. ALCOHOL, NARCOTICS, AND THE HUMAN MACHINE . . 392
VII. WHAT Is THE IMPORTANCE OF SAFETY EDUCATION AND FIRST
AID? 399
GLOSSARY 417
INDEX 425
SURVEY QUESTIONS
How do we get acquainted with
things around us ?
Do you know what is meant by a
scientific habit of mind ?
What does open-mindedness
mean?
Do you know of anyone who is
superstitious or who has beliefs
not founded on facts ?
Why are our sense impressions not
always reliable ?
Do you know the meaning of the
word environment?
What is the difference between a
physical and a chemical change?
Armstrong Roberts
UNIT I
GETTING ACQUAINTED WITH THINGS
PREVIEW
Have you ever climbed a high hill and looked off over
the countryside ? What a lot of things you could see —
trees and open fields, brooks and lakes, hills and valleys —
with perhaps homes scattered here and there through the
landscape. If you looked more carefully, you could see
many other smaller things : the leaves on the trees, birds
flying, insects buzzing through the air, stones on the
ground. You could count hundreds of different things
that you could see from that one hill.
But how were you able to know that all these different
things existed. You could see them, touch them, perceive
that some things had a pleasing odor and that some tasted
good or bad. It was different from seeing a picture. You
could tell these different things existed and were real
because of your ability to see, touch, smell, or taste
them — in other words, you became acquainted with them
through your senses.
A good many years ago before science was used very
much in people's thinking, it was the custom for some
philosopher to write a book, and then his pupils and all
who believed with him would follow exactly what was
said in the book without using their senses for themselves.
It is said that John Hunter, a famous Scottish physician
and surgeon, was once present at a meeting of scientists
when they were discussing the structure of birds. The dif-
ferent men present quoted from various books the sayings
H. & W. SCI. I — 2 1
GETTING ACQUAINTED WITH THINGS
of the old philosophers, Aristotle,1 Galen,2 and Hippoc-
rates,3 concerning the structure of the bird. One philoso-
pher said one thing and
another something else.
They did not seem to
be in agreement. Natu-
rally this set up a great
discussion in the group,
for some believed what
one philosopher said and
others took sides with
another statement. But
John Hunter got a bird,
killed it, and cut it open
and showed the position
of the various organs to
the group. Naturally
they had nothing to say
because John Hunter
had used the method of
the scientist; he had
used his senses in ob-
taining evidence ; something real that could be seen and
touched, not just read about.
Have you ever tried to discover all the different forces
and things that go to make up your surroundings ? There
is first of all the air, which seems to be necessary for all
living things. Then there is water and fire and sunlight,
all essential to our existence. The soil or the earth's
surface with its living inhabitants might be considered
as another part or factor of our surroundings. Scientists
also consider such forces as electricity and radio activity,
Aristotle (ar'fe-t6t'l) . A Greek philosopher who lived 384-322 B. c.
2 Galen (ga'len). A physician of ancient Greece.
3 Hippocrates (hl-p6k'rd-tez) . A Greek physician born about 400 B.C.
Culver Service
John Hunter. After reading this unit de-
cide if he showed the method of the scientist
in his actions.
HOW DO WE GET ACQUAINTED WITH THINGS? 3
forces which act upon living things. All of these forces
and things we collectively call our environment, and each
one by itself is a factor of the environment.
This unit is intended, first of all, to show us the way
that we get acquainted with our surroundings and how we
may use the method of the scientist in learning something
about this wonderful world that surrounds us, what our
surroundings are composed of; and, finally, how we as
living creatures use this environment in which we are
placed.
PROBLEM I. HOW DO WE GET ACQUAINTED
WITH THINGS?
Indians Were Keen Observers. Those of you who
have read The Last of the Mohicans remember Uncas,
Wright Pierce
The next time you are in the forest look on one side of the tree trunk for a green
mosslike growth. This is not moss, but algae or lichens, low forms of plant life.
GETTING ACQUAINTED WITH THINGS
the Indian brave, who was able to find his way through the
trackless forest because he observed and remembered
all the things in the
forest that might serve
as guide posts. The
green growth on the
trunks of the trees, a
mark on a rock or tree
trunk, a broken twig, or
unusual sound, each had
its message to the keen-
sensed Indian. We
think this was very
wonderful, but a boy or
girl who uses his senses
carefully and makes ob-
servations that are accu-
rate will soon find that
these signs, which might
be unnoticed by the
poor observer, have a
real story to tell.
More Than Observa-
tion Necessary. But
observation alone will
not take us far. The
Indian saw accurately
but he also said to him-
self that this green
growth on a tree means
"north side," and that
broken twig means
"some one has passed
this way." So it is
with any one who
Turn book so that top of cut a is at bottom.
Slowly turn book while watching the stairs.
Result? Are the two horizontal lines in b
parallel? Do the two horizontal lines in c
appear the same length? Measure them.
Is the line cut diagonally by the two oblong
blocks a straight line ? Which of the three
figures in d appears tallest ? Measure.
HOW DO WE GET ACQUAINTED WITH THINGS? 5
studies science. His observations may be good, but,
unless he relates his observations to something that he
wants to know, he will not get very far with his study.
Sense Impressions Are Not Always Reliable. If you
look carefully at the picture on page 4, you are quite
sure that the man in the picture is taller than the little
girl shown in the foreground. But if you draw lines
touching the tops of the heads of the three figures and
the bottoms of the feet of the three, you will be surprised
at what you find. Try it and see for yourself. This
shows us that sense impressions, even when carefully
made, cannot always be relied upon.
We Need to Know Where We Are Going. Uncas, in
his -wanderings through the forest, made his observations
with some object in mind. If he was stalking deer, it
was signs of deer that he looked for. If going through
a hostile country, it was signs of enemy that he sought.
So it is with any one who studies science — or indeed
any school subject. He must know where he is going and
what he is after. Our observations must be directed
toward one goal and we must know just what this goal is.
In science we call it a problem and we say we are trying to
solve a problem. This interesting old world in which we
live has so many interesting problems for us to solve -
secrets which can only be discovered when the observa-
tions we make are directed to a goal in which we are
interested. Remember this in your science work and it
will always seem worth while.
Life Is a Continual Solving of Problems. But, you say,
this isn't true. We are not solving problems when we
are at play. Think a moment — tag, or swimming,
or football. In tag, you must dodge ; but does quick
dodging just happen — or do we learn to dodge skillfully ?
Did we ever have to learn to swim? Ask the football
player about the successful plays that win the game.
GETTING ACQUAINTED WITH THINGS
Wide World
Tennis tactics require problem solving. The couple at the net have been suc-
cessful in solving theirs.
You will find that most things in life that are worth while
involve thinking, and thinking ought to mean problem
solving.
The Scientist Has a Way of Looking at His Problem.
One of the most characteristic things about a scientist
is that he is open-minded. He never makes his mind up
until the evidence is all in. Some people say, "I make
up my mind and keep it made up." Such people are not
open-minded. They are not willing to accept new evi-
dence that might oppose what they think. The scientist,
on the other hand, is always lobking for new evidence.
He is always open-minded. He may have a theory, but
he will give it up if his experiments give him answers
which do not agree with it. Charles Darwin is said to
have experimented with certain animals in hopes that
they would do something that would prove a theory he
then held, but when they didn't, he would say in an ad-
miring way, "The perverse little beggars, they will do it
their way."
HOW DO WE GET ACQUAINTED WITH THINGS? 7
How Do We Form Habits ? A habit is said to be an
act or attitude which is learned through practice. Habits
are of many kinds. Some are concerned with our way of
looking at life. We may be habitually happy or grouchy,
kind or cross, scatter-brained or able to concentrate,
depending on the habits we form when young.
A good many rules have been made to aid us in habit
formation. Here are some worth remembering :
1. Know what habits you want to form and then act
on every opportunity.
2. Make a strong start. No half-hearted effort was
ever successful in forming new habits.
3. Allow no exceptions. Habits are only established
by keeping right at it. One misstep means we start all
over again.
4. In place of bad habits establish good ones. Habits
always have opposites.
5. Use every effort of will. Never say, "I can't," and
you will one day wake up to the fact that you have estab-
lished your new habit. Straight thinking is really a habit
of mind. If we can only get the habit of making our
decisions on evidence which is real and not on hearsay, we
would be saved much trouble in later life.
The Scientist's Method of Thinking in Everyday Life.
You can see from what has just been said that the scientist
looks at things fairly and squarely, and that he always
tries to find out the truth by means of the evidence ob-
tained from asking questions of nature. He is not satisfied
with anything but the truth. How much it would mean
to each one of us in daily life if we could take the scientist's
method of thinking and refuse to be satisfied with propa-
ganda or newspaper stories which tell half truths. We
would be less likely to believe many of the superstitions
which many people have faith in. What evidence have
you that bad luck is associated with number 13? What
How many of these beliefs do you hold? Can you find any reason for holding
these beliefs? Do you believe that the ground hog can foretell the weather?
Or that you will have good luck if yoti see the new moon over your left shoulder
with money in your pocket ? If you do you are not scientific in your attitudes.
HOW DO WE GET ACQUAINTED WITH THINGS? 9
evidence have you that breaking a mirror carries bad
luck with it, or that a black cat crossing your path means
bad luck, or that walking under a ladder will be harmful ?
A moment's thought will show you that there is no
evidence for the truth of these superstitions. Every
boy or girl who studies science should determine that he
will carry over into his daily life this way of looking at
science problems. You may be sure it will mean much
to your peace of mind now as well as make you a more
intelligent and thoughtful citizen.
Use of Workbooks. Every pupil should keep a note-
book in which are recorded observations and facts noticed
and learned demonstrations, statements made by the
teacher, and notes from supplementary readings. Outline
drawings of the apparatus used in some of the experi-
ments, and of the machines, animals, or plants, which he
wishes to remember, should be in this book which we will
call a workbook. When the work of each unit is organized
for review, an outline form of the unit should be recorded,
as well as brief but clear reports of special projects, ex-
periments, labeled diagrams, and figures which are neces-
sary for a clear understanding of the various problems of
the unit. Finally, the workbook may contain a collection
of clippings, pictures, and photographs, related to the vari-
ous topics. Your workbook will be something that you
can keep after your course is finished. It will not only be
a memento of a worth-while bit of individual work, but it
also will serve as a reference book to be used if you go on
with the subject of science.
How to Use the Self-Testing Exercise. In the pages
that follow we shall find at the end of each problem a self-
testing exercise ; the object of this exercise is to help you
master the problem which it closes. To make the best
use of this exercise, you should place the numbers of the
blank spaces in columns on a sheet of paper. Then read-
10 GETTING ACQUAINTED WITH THINGS
ing the self-testing exercise carefully, try to see how many
of the blanks you can fill in. After you have done all you
can, go to your teacher and see how many words you have
missed. Then go back to your text and your notes in
your workbook and study again the part you missed.
After a short time try the test again and see if you now
can fill in all the blanks. Do not give up until you can
fill in every blank correctly without looking at your text.
If you can do this after an interval of say half an hour
after you looked at the book, you should have mastered
the facts contained in the problem.
How to Use the Story Test. Next try the story test.
This may contain some misstatements and is supposed
to help you get some of the big ideas or generalizations
contained in the problem. Use this test as you did the
self-testing exercise, checking up with your teacher to
see where you are wrong. Then go back to the text and
see what it is that you did not understand. These tests
should help you greatly if you use them in the manner
just suggested.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank
spaces in the sentences below, and arrange them in proper numerical
order. A word may be used more than once.
problem
impressions
method
characteristic
problems
determination
play
concentrate
open
work
observer
goal
closed
learn
experiment
success
thought
study
judgment
weighing
scientific
signs
will
solving
propaganda
attacks
constantly
evidence
sane
reliable
unnoticed
sense
Perhaps the Indian could not repeat many science principles,
but he learned to become a keen (1) His watchful eye noted
many (2) which had a meaning to him, but which might pass
(3) by you or me. One must (4) to recognize illusions
OUR ENVIRONMENT AND HOW WE USE IT 11
because not all sense (5) are (6) Throughout life one
(7) has (8) to solve, not only in his (9) but also
in his (10) In science one learns a (11) of solving
(12) The scientist (13) problems with an (14)
mind. It needs strong (15) power and (16) to change
a habit. The habit of (17) (18) before forming a con-
clusion is (19) of the (20) method.
STORY TEST
GEORGE WRITES ON THE METHOD OF THE SCIENTIST
Read carefully and critically. List all the errors and suggest
corrections.
I want to be a scientist when I grow up so I have decided to
form the habit of thinking like a scientist. First of all, a scientist
always makes his mind up as to whether a thing is so or not and
never changes it. That is the way to successfully solve problems.
You must try to see the end or reason for doing certain things. It
is not wise to have an open mind and listen to everybody's views.
It is much better to have a mind of your own and not allow your
ideas to be changed by anyone. The scientist may find out the
truth by means of evidence, but the easiest way to be sure to have
the right evidence is to ask someone rather than to depend upon
your own experiments or experience. If the Indians had only
made some practical use of their ability to observe accurately,
we might credit them with using reason. The scientist always
tries experiments and asks questions of nature to see if he is right
in his problem. I would never study books in science for you
cannot learn anything from books. I would always make experi-
ments, and if they came out the way I thought they ought to come
out, then I would believe them. In other words, a scientist always
believes his senses.
PROBLEM II. WHAT IS OUR ENVIRONMENT AND HOW
DO WE USE IT?
What Are the Factors of Our Environment ? Just what
do living things need in order to live ? Growing boys and
girls use air in breathing, drink water, eat food, are com-
fortable at a certain temperature, need light, and also
need something to live on, the earth. With our present
GETTING ACQUAINTED WITH THINGS
Photo by U. S. Forest Service Orient and Occident Photo
What factors of the environment are alike in these pictures? Which are different?
N. Y. Times and St. Louis
Post Dispatch
knowledge it would be difficult to prove that plants and
animals use in one way or another all of these forces and
things which surround them, but such is the case. The
bird in the air, the fish in the water, the tree in the ground
- all living things — use some part of the air, water, a
favorable temperature, light, and some kind of supporting
substance, as the soil, in order to live. Hence we call
these the factors or parts of the environment.
Living things depend upon the factors of the environ-
ment. We could easily prove that these factors of the
environment were necessary for life by simple experiments.
A fish will die out of water, and no animal or plant will live
long without this important substance. If the plant or
animal were placed in a jar from which it could exhaust
the air, we would find that it woujd die as soon as the air
supply was cut off. Light is essential to most living
things, for all green plants and most animals prefer light.
Some require much heat ; others, like the polar bear, pre-
fer a cold climate. Some plants can exist in temperature
which would mean death to others. And all living things
find some support necessary for their bodies, usually either
water or soil. We know that living things need and use
factors of their environment, but how they use these
factors is much more difficult to understand.
OUR ENVIRONMENT AND HOW WE USE IT 13
The Nature of Matter. The person who considers
only plants or animals in relation to their environment
might be satisfied to stop with the factors mentioned
above. But the scientist wants to know more about the
environment. He is not content to know what things
do ; he wants to know how they are made. He will tell
you that all these factors of the environment as well as
the living things found in these are made up of something
he calls matter. Matter, according to the scientist of
yesterday, was anything that had weight or filled space.
But the scientist in our changing world is not content
to stop with this definition. He says experiments show
him that matter behaves as if it were made up of tiny
particles separated by spaces. He can take a hollow iron
ball filled with water, which looks quite solid to the human
eye, and by subjecting it to great pressure, can squeeze
water right through it. This, he says, could not be done
unless the iron were built of particles which are not con-
tinuous but are separated from each other by spaces.
The scientist calls these particles molecules. But he does
not stop there. He says that the molecules can be broken
a molecule
of voter
Read the paragraph on " The Nature of Matter " carefully. The electrons are repre-
sented by dots and the protons by small circles. Can you explain this diagram ?
14 GETTING ACQUAINTED WITH THINGS
down into still smaller particles called atoms and those
into still tinier bits of matter which he calls electrons and
protons. We see a good deal in the papers and magazines
about these tiny electrons, which the physicist says are a
form of electrical energy, but nobody has ever seen one.
Our present idea of the nature of matter is only a theory,
but so sure is the scientist of his experiments that the
modern world has come to accept this theory as a basis
on which we build all our knowledge of matter.
Elements and Compounds. In order to understand
a little about what goes on in the world we must know
something about how changes in matter are brought
about. To do this we can make a little excursion into
the field of chemistry. The chemist says that all matter
is compounded of simple substances called elements.
The entire universe is made up of these substances, of
which there are about 90, and he says that these elements
can combine to form compounds which are so numerous
that everything, living or dead, is made up of these sub-
stances. Some elements we know : oxygen, for example,
is the gas we need if we are to breathe. You have per-
haps seen the experiment made in which a red powder,
red oxide of mercury, is heated in a test tube. As the
substance gets hot, we see the red substance change to
glistening drops of mercury such as you see in the bulb of
a thermometer. If you insert a glowing match into the
test tube, it bursts into flame, showing the presence there
of a gas which supports the flame. This is oxygen, a gas
which helps things to burn. This experiment shows that
we can break down a compound into its original elements,
which in this case are the elements oxygen and mercury.
Energy. A lighted match gives out heat and light.
Exploding gasoline can move an automobile. A thrown
stone may break a window. When matter is in a con-
dition of motion it can exert a force it does not have when
OUR ENVIRONMENT AND HOW WE USE IT 15
it is at rest. When wood burns it produces factors of our
environment that did not exist before. These new factors,
such as light, heat, chemical action, electricity, and
mechanical action, are forms of energy. Matter without
energy would make a very different world from ours.
Energy is just as useful as matter and the two always are
to be found together and they are present in everything
in the universe as far as we can tell.
What Is a Chemical Change ? When we burn a strip
of magnesium metal, we get a bright flame, and there is
left a white brittle compound called magnesium oxide.
Here we have combined oxygen from the air with the
magnesium and have an example of a chemical change
called oxidation.
When magnesium is burned, oxygen combines with it
and a single new product results. The change is chemical.
The chemist expresses this change as follows :
2 atoms of
Magnesium
2Mg.
2 atoms of
Oxygen
02
2 molecules of
Magnesium oxide
2MgO
When iron rusts, we have a similar chemical change taking
place : oxygen of the air unites with the iron, forming iron
oxide. Such changes are continually taking place in
nature. We shall see later that life itself depends upon
this process of oxidation.
Physical Changes. When your knife gets dull and you
have to sharpen it, you do not change the composition
Which of these changes are chemical and which physical? How many similar
changes can you list for your workbook ?
16 GETTING ACQUAINTED WITH THINGS
of the blade. Some of the molecules are scraped off by
mechanical means, but they are still iron molecules.
Such a change is physical. Physical changes are illus-
trated by writing on paper, boiling water, bending a wire,
grinding corn, and plowing soil. The composition of the
molecules is not changed by a physical change, but is
changed by a chemical change.
We Use the Factors of the Environment. What do
these facts about chemistry and physics have to do with
us? What is the meaning of chemical and physical
changes in the world about us? All we need to know
now is that such changes are continually going on and
as a result of such chemical and physical changes we are
able to use our environment. Take, for example, the
burning of coal. Energy or power to do work is locked
up in the coal. It is unused until the coal is burned, then
heat is released and this heat may make water boil, turn
the wheels of a locomotive, draw cars and passengers,
and cook our food. How does this energy get out? It
gets out simply because the elements, hydrogen and
carbon, in the coal unite chemically with the oxygen of
the air, forming new substances and releasing the heat
which may be transformed by machines into work.
Chemical changes of this sort are constantly going on in
nature ; rocks are crumbling and breaking down into
soil ; the soil itself is uniting with oxygen and breaking
into still finer pieces ; foods in the bodies of plants and
animals are being combined with oxygen or oxidized to
release energy.
Life Is a Series of Physical and Chemical Changes.
And physical changes are going on as well. Wind and
water break down and wear away solid rocks, and water
turns wheels to transform their energy into power, perhaps
in the form of electricity. Ice is formed from water. We
may see it in the form of a glacier moving slowly down a
OUR ENVIRONMENT AND HOW WE USE IT 17
mountain side or it may fall from the clouds as snow or
hail.
In our own bodies hundreds of chemical and physical
changes are taking place every minute as the human
machine changes its position in walking, running, swim-
ming, driving, and even sitting or resting. Our mus-
cles are always at work, — contracting, relaxing, — thus
showing physical changes. And inside the body com-
plicated chemical changes are taking place : food is being
digested ; we breathe and the oxygen of the air unites with
the digested foods as we do work. Work done by the
muscles involves still more chemical changes. All life as
seen from the standpoint of the chemist and physicist is a
series of chemical and physical changes. And in the com-
plex environment of today more and new physical and
chemical changes are found as man makes use of new and
different helps in his everyday life.
Man's Environment Much More Complex Than It Used
to Be. If we were to compare the life of Uncas, the
Compare the living conditions of the Indian with those in a modern city,
what ways do they differ ? In what ways are they alike ?
H. & w. sci. 1 — 3
In
18 GETTING ACQUAINTED WITH THINGS
Indian, with the life of the average boy or girl of today,
we would find a vast difference in the environment. The
Indian lived simply on natural foods ; if he had a fire,
it was rarely used for anything but cooking ; his shelter
was primitive and his methods of transportation and
communication even more so. Contrast his life with
that of the boy or girl who reads these lines — paved
streets ; rail, motor, and air transportation ; the telegraph,
telephone, and radio; the elaborate homes and great
apartment houses of the cities ; the systems of water
supply, lighting, and heating that are now a part of
our lives would seem very strange to the Indian who
occupied this land not so many years ago. Man has
greatly changed his original environment and made this
world a pretty complicated place in which to live. This
book will help us to understand better how to enjoy and
control our environment.
SELF-TESTING EXERCISE
Select from the following list the words that best fill the blank spaces
in the sentences below and arrange the words in proper numerical
order. A word may be used more than once.
chemical continuous particles electrons
compound physical elements factors
molecules largest oxide magnesium
atoms electricity protons oxygen
masses smallest * pressure separated
united microscope rust inanimate
composition environment electron weight
Water, air, and light are three of a group of things which are
called (1) of the (2) Matter which appears (3) is
really made up of minute (4) called (5) which are (6)
by spaces. These (7) are made up of atoms, and according to
the latest theories, all matter is composed of still smaller electrically
charged bodies called (8) and (9) When the element
magnesium is burnt, it combines with the element (10) and
produces the (11) magnesium (12) . Chemical changes
OUR ENVIRONMENT AND HOW WE USE IT 19
always involve a change in the (13) of the molecules ; all other
changes are (14) Boiling water is a (15) change, and
burning a match illustrates a (16) change.
STORY TEST
MARY TELLS How WE USE THE ENVIRONMENT
Read carefully and critically. List all the errors and suggest
corrections.
The environment is everything around us. It may be natural
or artificial. The factors of the artificial environment are air,
light, water, temperature, and something to rest on, or grow from,
such as rocks, soil, or the ocean. I have a little garden where I
put seeds into the dry earth and the warm sunshine makes the
plants develop and grow. It certainly is like magic. Air, water,
food, and soil are factors of our environment, but heat, light, and
gravity, while we make use of them on occasion, are not really
factors of the environment because they are not substances.
They are mere creations of the imagination. Fish can live with-
out light. We do not need to burn coal to get heat, we can move
south where we shall not need it, and gravity is harmful as well
as beneficial. It is gravity that makes the disastrous land-slides
and causes us to fall down.
THE REVIEW SUMMARY
You have now come to the point where you want to find out
how much you really understand of the unit you have just studied.
To do this best you should be prepared to get up before the other
members of your class and, with a brief outline of the unit in your
hand, explain to the class any or all of the problems, as your
teacher may wish. Perhaps you will be asked to make a recitation
on only a single brief topic, or you may be asked to discuss an entire
problem. In any event, you will want to prepare an outline from
which to recite so that you will not miss any important parts of
the unit. In this first unit a suggested outline will be given ; but
in the later units you must make your own outline. If you wish
to change them, you may do so. These outlines should be based
upon what you have read, learned, and done, and upon the big
20 GETTING ACQUAINTED WITH THINGS
ideas or generalizations that are found in each unit. In this first
unit, for example, those placed below are examples. Perhaps you
will want to add or subtract from this list.
1. The scientist observes carefully and uses his observations
to form conclusions.
2. The scientist is open-minded. He will base his conclusions
only on evidence.
3. The scientist's way of thinking becomes habitual if practiced
in daily life.
4. People who are influenced by superstitions are not using
the method of the scientist.
5. The environment is everything that surrounds us.
6. Living and lifeless things are made up of matter.
7. Matter is not continuous but is made up of very small
particles.
8. All we know about matter has been learned through the
method of the scientist.
Your outline should be based on all the facts that you have
learned plus the generalizations formed as the result of applying
these facts in your daily thinking. If you follow this method,
it will help you in preparing your outline because you will thus
focus on the most important things in the unit. A suggested out-
line follows. Perhaps you can improve upon it.
How we get acquainted with things :
By sense impressions
These not always reliable
The method of the scientist is :
Problem solving
Open-mindedness necessary
Habits :
How formed ,
Habits necessary for scientist
What is environment
What are its factors
What is matter :
Theories of composition
molecule
atom
electron — proton
Chemical and physical changes :
in matter
in living things
Man has changed his environment by applying scientific facts,
OUR ENVIRONMENT AND HOW WE USE IT 21
TEST ON FUNDAMENTAL CONCEPTS
Make two vertical columns in your workbook. Head one CORRECT,
the other INCORRECT. Under the first place the numbers of all statements
you believe to be correct. Under the second place the numbers of all state-
ments you believe to be incorrect. Your grade = right answers X 2.
I. We get first-hand knowledge of our environment through :
(1) our minds; (2) our senses; (3) our sense organs; (4) the
nerves which cause movement of muscles ; (5) talking with our
friends.
II. The factors of the environment are : (6) water ; (7) clouds ;
(8) the things inside of a house; (9) air; (10) degrees of heat.
III. The method of the scientist: (11) uses the experiment;
(12) means having a decided point of view and holding to it ;
(13) uses the senses ; (14) is essentially problem solving ; (15) uses
the facts in order to draw conclusions from them.
IV. Green plants use from their environment: (16) water;
(17) dissolved minerals; (18) sunlight; (19) insects; (20) milk.
V. The following things are made of matter: (21) water;
(22) a feather ; (23) a thought ; (24) a person's brain ; (25) light.
VI. There is energy used when: (26) we chew our food;
(27) a balloon rises ; (28) a falling balloon hits the ground ;
(29) water freezes ; (30) lightning strikes a tree.
VII. Animals use the following from their environment :
(31) plants; (32) nitrogen of the air; (33) water; (34) oxygen
from the air; (35) sound.
VIII. The following are chemical changes : (36) cooking meat ;
(37) soldering two pieces of tin together ; (38) freezing ice cream ;
(39) sharpening a knife on a stone ; (40) digesting food.
IX. An example of a physical change is : (41) throwing a stone ;
(42) lighting a fire ; (43) putting out a fire ; (44) dissolving salt
in water ; (45) writing these words.
X. The use of the scientific method helps (46) to dispel
superstitions ; (47) to tell which horse will win every time ; (48) one
to think straight ; (49) to make discoveries ; (50) to apply facts
in useful inventions.
THOUGHT QUESTIONS
1. What are two things which everything contains and neither
of which would be of any use without the other ?
2. Can you usually tell by observation whether a change in
body is a physical or chemical change? Explain.
22 GETTING ACQUAINTED WITH THINGS
3. Which of the following actions are chemical changes and
which are physical changes? Why?
a. Melting of lead d. Boiling of water
6. Burning of wood e. Rusting of iron
c. Making a pencil mark on paper /. Souring of milk
4. How can you train yourself in observation?
REPORTS ON OUTSIDE THINGS I HAVE READ,
DONE, OR SEEN
1. Report upon an article related to some topic discussed in
this unit. The article may be from a current number of a science
magazine or from some popular science book you have read.
2. My home environment (in one of the following localities :
a farm, a city, a mining town).
3. Compare the environments of the American Indian and the
early cliff dwellers.
4. What superstitions do your friends have that actually
influence their behavior in any degree?
5. How some important elements are obtained from compounds.
SCIENCE RECREATION
1. Chemical and Physical Changes. Making a smoked sun
glass with which one may safely look at the sun to view sun spots
(through a telescope) or at an eclipse.
When a candle is lighted, notice the melting of the wax — some
wax runs down the sides and hardens. Bring the glass down over
the flame. Keep it moving so that the glass will not break. Try
to get an even deposit of black carbon over the surface of the glass.
The molecules of the wax of the candle contain hydrogen and
carbon. When the flame is cooled, the hydrogen burns, but all the
carbon does not burn. This unburned carbon is deposited over
the surface of the glass. List the kinds of changes — melting
wax, solidifying wax, burning wax, separation of carbon, deposit
of carbon on the glass.
2. Are You Superstitious? Make a list of superstitions that
have to do with the number 13, broken mirrors, salt, black cats,
ladders, posts, moon, umbrellas, warts, etc. Tell how you could
subject some one of these superstitions to a scientific test to see
if they have any foundation of truth.
3. How Is Your Second Sight? Place 10 pairs of objects on
a table. They may be of the following nature : a pair of scissors
OUR ENVIRONMENT AND HOW WE USE IT M
cutting cloth, a knife cutting an apple, thread in a needle, pencil
on a pad of paper, pen in an ink bottle, stamp and an envelope,
cup and saucer, cracker and cheese, soap and water, baseball and
player's glove. If you have a party of 12, invite six at a time
into the room to look the things over on the table. After two
minutes (perhaps one minute) send them back. Give each a pencil
and paper — warn them not to talk — and have them write out a
list of the pairs of objects seen. Have each check their answers
when you read the correct list. Have a simple prize for the winner.
To make the game more difficult, separate the paired articles on
the table so that no two things to be paired will be together, but
ask them to make their list of pairs of things which commonly are
used together.
SCIENCE CLUB ACTIVITIES
1. A field trip to discover as many kinds of environment as
possible.
2. To make a list of superstitions of your locality and find out
how many members of the science classes are influenced by any of
them.
3. Visit a factory or a hospital to see some of the recent results
of science in these places.
4. PHYSICAL VERSUS CHEMICAL
Divide the club into two teams. One team will bring to the
meeting a list of important common physical changes. The
other team will bring in a list of important common chemical
changes. Have the two teams present in turn a change and argue
why it is important. Give a point for each important change and
see which team runs up the largest score. Choose some dis-
interested party to act as umpire to decide questionable points.
REFERENCE READING
Darrow, F. L., Boys' Own Book of Science. Macmillan, 1923.
Darrow, F. L., The Story of Chemistry. Bobbs-Merrill, 1930.
Harrow, Benjamin, Romance of the Atom. Boni and Liveright,
1927.
Heyl, P. R., New Frontiers of Physics. Appleton, 1930.
Hunter, G. W., and Whitford, R. C., Readings in Science. Mac-
millan, 1931.
Yates, R. F., Boys' Playbook of Chemistry. Century, 1923.
SURVEY QUESTIONS
Do you know what the term adap-
tation means ?
Do you know why these plants are
able to live in the desert?
Do you know how a bird is able to
fly?
Can you mention any ways in which
your own body is fitted to live ?
How does your way of solving a
problem differ from that of a fish ?
Of a bird?
Would you say it is true that man is
the only animal that can success-
fully change his environment ?
•
Wright Pierce
UNIT II
LIFE DEPENDS ON ADAPTATIONS
PREVIEW
Every boy or girl who reads these lines has at one time
or another kept a pet. Perhaps it was a dog or cat or a
bird. Some of us enjoy watching goldfish or the brightly
colored tropical fish that are so much seen in the home
aquariums today. Some boys keep turtles and find them
very interesting pets. We might take a census of animal
pets kept by pupils taking science and add many new
animals to the list.
Some of us prefer gardening or the keeping of plants at
home. Hyacinths, jonquils, or other bulbs make a fine
showing in the spring, while geraniums are always pretty
and easy to grow. We may even have collections of
strange spiny-covered cactus plants or a "burl" from a
giant redwood. But no matter whether you had plants or
animals to care for, you must have noticed that each
particular living thing seemed to be fitted to live under
certain conditions and only under those conditions. Our
desert plants grow best in sand and when it is hot and
dry like the deserts from which they originally came.
Our goldfish would certainly be very unhappy if they
were taken out of the water and it would not be long
before they were dead. Our pet canary would be equally
unhappy if we tried to keep it in a screened tub of water.
Even our pet dog or cat would resent a change of living
from the conditions to which it was used.
Wherever we go, we are constantly seeing examples of
the fitness of living things to succeed in the places where
25
26 LIFE DEPENDS ON ADAPTATIONS
Wright fierce
This gentleman has a hobby. How many of his pets can you find ?
they are found. Biologists call these fitnesses adaptations.
They are still uncertain just how these adaptations are
handed down to new generations of plants and animals
or just how it is that some plants and animals can adjust
themselves to new conditions of life. We may learn
more about this when we come ,to our study of biology.
For the present all we are concerned with is to learn a
little about adaptations in living things and to try to
understand how we, as living things, are fitted or adapted
to live in our surroundings.
PROBLEM I. WHAT ARE ADAPTATIONS AND
WHAT DO THEY DO?
What Are Adaptations ? Probably every boy and girl
who reads these lines has seen a porcupine, if not alive,
WHAT ARE ADAPTATIONS?
then in a museum. At first sight you might wonder how
in the world he uses his spiny covering. But if you had
been out hunting and had your dog come in whining with
his nose full of quills, you would not have to ask this
question. Evidently the spiny covering gives protection
to the otherwise defenseless animal. Or perhaps you
have wondered how it was that some plants could stand
severe drying while others wilted at once if they became
dry. When you examined the leaves of the first plants,
you probably found them either covered with tiny hairs
or having thickened waterproof surfaces, which prevented
rapid evaporation of water, while the plants that wilted
quickly might have large, thin leaves with much surface
from which to evaporate water. You may have wondered
what the elephant did with its long trunk until you saw
it use it for getting food or water. When we find in plants
and animals structures which are fitted for some definite,
useful purpose, we
call that structure an
adaptation and say it
helps to fit or adapt
the living thing to do
some particular work.
But plants and
animals do not stop
there. Often we find,
in order to adjust
themselves better to
their surroundings,
they do certain
things. Some plants
may twist or twine
around objects, thus
rising above other plants and so place their leaves in the
light where they can make food. Animals hide in the
American Museum of Natural History
When the porcupine becomes angry or fright-
ened the quills stand out so that no enemy can
touch him without getting hurt.
28 LIFE DEPENDS ON ADAPTATIONS
grass like the grasshopper, or burrow in the ground like
the gopher, or withdraw into a protective shell like the
snail or turtle, and in hundreds of ways perform actions
that result in getting protection from their enemies or
food for themselves. In shallow water at the seashore
you may have caught little hermit crabs which protect
their defenseless bodies by thrusting them into the cast-
off shell of a sea snail, and retreating into it in time of
danger. Such adjustive actions we also call adaptive, for
they result in some good to the animal or plant.
Some animals are even adapting themselves like man
to the changed conditions of modern life. The English
sparrow, which used to subsist in our cities very largely
on the partially digested seeds in horse and other manure,
began to disappear in the cities when automobiles took
the place of horses. Now we occasionally see the sparrows
perched on the radiators of cars picking out insects which
have been caught in these radiators as the cars went
through the country highways.
Adaptations, then, may be structures which help the
animal or plant to live, or acts performed by the animal
or plant which result in better living conditions.
The Problems of Living Things. If you will think for
a moment, you will see that living things, both plants
and animals, have two big problems in life. The first
is the care of themselves, the Second the reproduction
of young. The business of living means adjusting them-
selves to their surroundings so that they may get food,
grow strong, and be able to protect themselves from their
enemies. No matter what the living thing, be it a fish,
a bird, a snail, a tree, or a weed, the problems of living are
the same in the end.
Some Ways in Which a Bird Is Fitted for Its Life Work.
Let us take, for example, a robin. You say such a bird
is well fitted for its life. It has its legs provided with flexi-
WHAT ARE ADAPTATIONS?
ble toes which lock around the branch on which it perches.
Study the wing of a chicken and you will see that the
feathers with the wing
form a light but effi-
cient structure which
offers resistance to
the air when pushed
against it. The
feathers are so con-
structed that the tiny
barbs which grow out
from the quill to form
the vane of the
feather are all locked
together by tiny
hooks, thus making a
strong, wind-resisting
surface. Beebe1 esti-
mates that a single
feather may have as
many as 990,000 of wngM pierce
these tiny hooks. You A magnified view of a feather- Can y°u **A
" the place where the barbs are hooked together ?
will also find that
strong muscles are attached to the wing and fastened
to the breastbone so that the wings can be moved
rapidly. The bones of the robin are very light and it
has a large heart and large lungs ; all these things together
help to make it an efficient flying machine.
But we have just begun to mention the ways in which
our robin is fitted to do his work. Think of the food he
eats, then look at the beak and claws and see how effi-
ciently they are built for the work they have to do. Think
of the nest of the robin, of the fact that its eggs are hatched
there and protected by the mother bird, that the little
1 William Beebe, living naturalist, explorer, and writer.
30
LIFE DEPENDS ON ADAPTATIONS
ones are fed by the mother until they are able "to go on
their own," and we see that in very many ways the robin
is fitted or adapted to
meet these big problems
of living.
How a Green Plant
Meets the Problems of
Living. It is not so easy
for us to understand how
a green plant meets its
problems of life, for at
first they seem so differ-
ent from those of an
animal. But are they
very different? An ani-
mal has to have food in
order to live ; so does a
green plant, only a green
plant makes its food out
of substances from the
air and soil and the water
it takes in. We must
remember that both plants and animals have to breathe.
They therefore need oxygen from the air. They both
need a certain amount of heat and light, some more, some
less. They must be protected* and they must produce
offspring if they are to be successful. The cactus is an
example of a plant that has been successful in spite of
unfavorable conditions. What special fitnesses or adap-
tations do we find which help it solve its problems of life ?
In the first place, instead of green leaves, we find spines.
Leaves would wilt in the hot desert air, because they
have large surfaces which allow water to evaporate from
the plant. The cactus conserves its water by having a
soft pithy stem which holds water and by having this
Wright Pierce
What kind of food does this bird eat ?
WHAT ARE ADAPTATIONS?
31
stem covered with a hard and corky covering which
keeps the water in. By doing away with leaves entirely,
the green stem instead of the leaves takes on the work
of food manufacture. The plant is protected by its spines.
No animal will eat it and it produces its young either by
seeds or by means of buds from the parent plant. The
cactus has solved its problems of life by means of its
adaptations.
Success for Plants and Animals Comes through Adap-
tations. You all know how difficult it is to get rid of
weeds in a garden. It seems as if they come up over
night and that as soon as you pull one up, another takes
its place. Weeds are successful plants, but why? If
you examine a full-grown weed carefully, you will soon
see why. Usually they produce very many seeds, and
they have excellent means of scattering them. Look at
the tumble weed as it rolls along, dropping seeds as it
goes. Look at the dandelion or thistle with its seeds
sailing through the
air — or the stick-
tight or cocklebur,
with its fruits get-
ting a ride by stick-
ing to animals.
Then weeds produce
many more seeds
than other plants.
Sometimes a single
plant forms hun-
dreds of thousands
of seeds. The seeds
sprout under con- wngm pierce
ditions Unfavorable This cactus has been cut so as to show the watery
for ntViPr rJnnta pulp which is held inside the hard skin. What
plants takes the place of the leaves in this plant? Why
With which they are there no leaves?
LIFE DEPENDS ON ADAPTATIONS
compete and they grow very quickly. They usually
have deep, tough roots which help them to crowd out
other plants by steal-
ing their water sup-
ply. Choose some
weed and note all the
adaptations you can
find. You will soon
see why it is so suc-
cessful in life.
We can also show
that animal success is
due to adaptations.
Take any animal you
know and name over
the ways it is fitted
for the life it leads.
Hoofs, claws, furry or
hairy coats, feathers or
shells, wings, fins, flip-
pers or legs, different
types of teeth, all these and many more you might name
as adaptive structures.
Wright Pierce
What devices can you find for scattering seeds
in this thistle ?
SELF-TESTING EXERCISE
»
Select from the following list those words which best fill the blank
spaces in the sentences below and arrange the words in proper numerical
order. A word may be used more than once.
life
adjustment
animals
rearing
acts
nature
death
leaves
structures
protection
plants
fitted
survive
fear
stems
make
care
similar
food
species
break
roots
elephant
spines
Adaptations are found everywhere in (1) and by means of
them (2) and (3) are (4) to meet their problems of
LIVING IN OUR ENVIRONMENT 33
living. These consist of getting (5) , (6) from enemies,
(7) to surroundings and the (8) and (9) of their
young. Both plants and animals have the same (10) prob-
lems and have to meet them in (11) ways, although green
plants have to (12) their food as well as use it. Adaptations
may be (13) such as the proboscis of an (14) or the
(15) in a cactus, or they may be (16) which help the plant
or animal to (17) in its struggle for life.
STORY TEST
JOHN WRITES ABOUT ADAPTATIONS
Read carefully and critically. List all the errors and suggest cor-
rections.
Our teacher has asked me to tell you about the adaptations I
found in my pet turtle. In the first place my turtle can live either
on land or in water and has adaptations that fit him for both kinds
of life. His claws, for example, are useful in swimming and the
heavy shell helps him to sink when he goes under water. I think
my turtle breathes under water, for he lets up a little stream of
bubbles when he is under the surface and can stay under for a
long time. But he always comes to the surface after a while,
and I notice at night he stays on land and seems to sleep there.
He has horny jaws which seem to be fitted for chewing his food.
I have watched him eat an earthworm. He grabs it with his jaws,
he tears it in two with his claws and then swallows the piece whole.
My turtle can swim, although his toes are not webbed. I guess
from this he is a water turtle.
PROBLEM II. HOW ARE WE FITTED TO LIVE
IN OUR ENVIRONMENT?
Man Is a Bundle of Adaptations. It is a common say-
ing that man is a bundle of adaptations. Did you ever
try to prove it true or false? Think of your own life
and the wonderful ways in which your body is fitted
for the work you do. You walk and run and jump
and swim without giving much thought to the mech-
anism of the human machine. But if you examine any
part of the body at all carefully, you will be amazed to
find the numerous adaptations that exist in it. Take,
H. & W. SCI. 1 — 4
34 LIFE DEPENDS ON ADAPTATIONS
for example, such a simple act as walking. Simple, but
is it ? So many parts of the body act together — muscles,
bones, nerves, heart, lungs, sense organs, and the master
of them all, the brain — that what seems a simple act
is found to be very complicated. You cannot with the
little knowledge you have at this time explain such an
act. But take something you can see and try to find
adaptations there. Have you ever thought how wonder-
fully your hand is adapted to the work of holding ob-
jects, such as a pen or pencil? You know in a general
way that it is a complicated mechanism, but do you know
how it is built ? For example, we have a bony framework,
in which the individual bones are held loosely together
in order to allow movement. But these bones are also
bound together tightly enough so that they cannot get
out of place. Not only are they held together, but each
is separated from its next neighbor by a pad of soft elastic
cartilage which gives a certain amount of play to the
whole hand skeleton. Then each bone has attached to
it scores of small, elastic bundles of muscles, some thirty-
one in number, which will expand and contract. These
muscles work in pairs, one relaxing as its partner con-
tracts, and since they are attached to the bones, they give
movement to them. But think of the numbers of muscles,
guu
What kinds of food would you think these birds eat ? Can you describe the kind
of feet each of the above birds would have ?
LIVING IN OUR ENVIRONMENT
35
some large, some small, that go into this work of moving
the hand and wrist. The muscles are attached to bones
by means of cords called tendons. You can feel these
cords in your wrist and you may have
found that movement of the fingers is
controlled by them. Study of the
figure will show that these tendons are
attached to muscles of the forearm so
that movement of the hand is controlled
by them. But we have again only
begun to find the adaptations in the
hand. All of the muscles must act
together and must be directed by
means of our nervous system. They
must be supplied with blood contain-
ing food and oxygen (see page 376) if
they are to do work. The skin must study this carefuiiy
be sensitive so we may know when we and then explain how
touch anything. If we see the thing
we touch, the eye plays a part. And
now that we have mentioned all of these structures, we
do not begin to understand how each part acts in grasping
the pencil, let alone how we make the complicated and
delicate actions which occur when we write our names.
The human body is full of adaptations, most of which
are far more wonderful than those just described. To
understand them thoroughly we must study physiology,
a subject to be taken up in the senior high school. But
we can see that the human body is a very complicated
machine and that our job in life is to learn to run it effi-
ciently.
Adaptations May Be Acts as Well as Structures. But
animals often have ways of doing things which are adap-
tations. Certain tropical ants, for example, cut leaves
from trees, carry the pieces to their nests, and there use
you
can move your
fingers.
Dr. Francis B. Sumner
The photographs above show the results of experiments made by Dr. Francis
B. Sumner of the University of California. He first photographed flounders in
aquariums in which the flounders rested on different natural backgrounds of sand,
mud, and stones. The fish always changed their color markings to blend with
their background, as we see in figures 1 and 2. What advantage would this be
to the fish ? He then changed the fish into aquariums having artificial back-
grounds like figures 3 and 4. What happened ? Can you account for these
changes ?
36
LIVING IN OUR ENVIRONMENT 37
them on which to grow tiny fungi ; colorless plants that
cannot make their own food. The fungi, not the leaves,
are used as food by the ants. The habit some animals
have of feigning death is one method of protection.
Many birds which look like their surroundings will keep
absolutely quiet on the approach of an enemy, thus
escaping notice. Some animals can even change their
colors or the markings on their bodies to blend with
their surroundings. Man himself shows many examples
of such adaptive acts. Have you ever thought that if
babies did not instinctively suck soon after they are born,
they could not live ? Our lives depend on this one adap-
tive act. Can you think of any others ?
Man, the Only Animal That Can Adapt His Environment
to Suit Himself. We can find many examples of adapta-
tion to the environment in plants and animals, but man
alone seems able to change his environment to suit him-
self. We know that desert plants will not live long in the
water and water-loving plants will soon die if placed in a
hot, dry place. Sheep having long wool when transferred
to a hot country like Cuba soon die, because the long wool
unfits them for life in the hot, moist climate. But if man
has to change his place of living from a cool to a hot
climate, he dresses differently. In other words, he adapts
himself to the new conditions. Some animals and plants
can do this to a degree if the changes are gradually made ;
thus they may become slowly accustomed to changes in
environment. But man is constantly changing his envi-
ronment for the better. Look at what science has done
to make living conditions more comfortable. We move
from cold climates to warm ones by means of automobiles,
railroads, steamships, or airplanes. We have fruits and
vegetables at all times during the year because of refrigera-
tion and cold storage. We are able to eat foods which
were grown thousands of miles away because of rapid
38 LIFE DEPENDS ON ADAPTATIONS
transportation and refrigeration. We have learned to
control disease so well that we have increased the number
of years man can live. In other words, man is a thinking
animal and as such has learned to control and improve
his environment.
How We Make Adaptations. Have you learned to
swim? You soon will if you have not already done so.
You may remember how hard it was at first to keep your
head above water and not to be frightened. You found
that as you learned the different motions, you gradually
improved, and then all at once you were able to swim.
You will never lose this adaptation so long as you live.
You have mastered this problem. When any one has
completely mastered anything, like learning to swim,
skate, read, or write, he has made an adaptation. So in
this book we have given you a number of helps so that
when you finish a unit of work, you may be sure that you
have complete mastery of the subject. You have, for
example, at the end of each problem, self -testing exercises
which will help you find out if you have mastered the
information in the pages just preceding. If you cannot
fill in the blanks correctly, you should study those facts
in the problem that you do not remember and then try the
test again. Keep at it until you have mastered the prob-
lem. Then there are other tests which help you apply
the information you have gained. You may know all
the facts in the unit, but if you cannot apply these facts
in the solving of simple problems, then you will not get
very far in the mastery of the subject. Let us try to use
these helps to gain the mastery which means success.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank
spaces in the sentences below and arrange the words in proper numer-
ical order. A word may be used more than once.
LIVING IN OUR ENVIRONMENT 39
change improve nervous framework
adaptations blood structure muscles
doing friend adapted successful
cartilage adapt endocrine efficiently
movement muscle food drink
enemy tendons adaptation unsuccessful
The human body has numerous complicated (1) which
enable us to live (2) The hand is an example of an organ
(3) for grasping or writing. It has a (4) of bones, loosely
jointed with pads of elastic (5) between. Thirty-one (6)
help to give (7) to these bones. Each (8) is attached
to one or more bones by tough cords called (9) The whole
apparatus is controlled by the (10) system. Adaptations are
not always (11) , they may be (12) ways of (13) things,
such as getting (14) or escaping from an (15) Man is
the only living thing that can successfully (16) the environ-
ment to himself. He can (17) it or (18) it, making an
(19) in that way.
STORY TEST
WALTER WRITES ABOUT ADAPTATIONS IN MAN
Read carefully and critically. List all the errors and suggest cor-
rections.
Animals and plants seem to be able to get along by means of
adaptations. These are usually structures which make it possible
for the plant or animal to live successfully where it happens to be.
But man, who is able to travel and to change his place of living,
does not have any such structures. He is the master of his sur-
roundings and can change them to suit himself. If, for example,
he is cold, he can put on more clothes or go where it is warmer.
Of course a man has arms and legs, but they are in no way like the
front and hind legs of a cat or dog. Since man can adjust himself
so well to new conditions, he does not need adaptations.
THE REVIEW SUMMARY
In preparing a summary of what you have learned in this unit,
you will want to place emphasis on the big ideas which have come
out of the applications of the facts you have learned and the demon-
40 LIFE DEPENDS ON ADAPTATIONS
strations you have seen. These big ideas we call generalizations.
For this unit they are as follows :
1. Adaptations are fitnesses for living in a given environment.
2. There are adaptive acts as well as adaptive structures.
3. Life depends upon adaptations.
4. Man shows many adaptations.
5. Man is the only living thing that can adapt the environment
to himself.
Before making your review summary, test your knowledge of
the facts of the unit by checking over the text so as to be sure you
know the facts underlying the generalizations. Then, using the
generalizations, the material in the text and everything you have
read, seen, or done yourself, make a summary outline for your
notebook. This outline you may use when you make a recitation.
TEST ON FUNDAMENTAL CONCEPTS
Make two vertical columns in your workbook. Head one CORRECT
and the other INCORRECT. Under the first place the numbers of all state-
ments you believe to be correct. Under the second place all the numbers
of all statements you believe to be incorrect. Your grade = right answer
X4.
I. Adaptations: (1) make it possible for plants or animals to
exist under certain conditions favorable to the adaptation ;
(2) make it possible for a plant or animal to live under any condi-
tion; (3) are adjustments; (4) are never found in the young but
appear late in life ; (5) are always structures.
II. Adaptations make it possible: (6) to obtain food; (7) to
protect the offspring successfully ; (8) to obtain money and fame ;
(9) to escape from one's enemies; (10) to adjust oneself to his
surroundings.
III. Some adaptations for life in the water are: (11) claws;
(12) gills; (13) fins; (14) slimy body; (15) heavy bones.
IV. Some adaptations for life in a hot, dry climate are : (16) elec-
tric fans; (17) spines instead of leaves; (18) in animals, thick
hair to keep off the heat ; (19) in plants, a thin body covering which
easily allows the escape of heat; (20) sweating, which gets heat
out of the body.
V. Man can control or change his environment: (21) by means
of clothes; (22) because he can solve problems and thus adapt
the environment to his needs ; (23) through scientific discoveries ;
(24) because he has a nervous system ; (25) because he is a " bundle
of adaptations."
LIVING IN OUR ENVIRONMENT 41
THOUGHT QUESTIONS
1. The trees near a smelter are found to be dying, although the
condition of water supply, soil, light, etc., seem unchanged. Is
this due to a lack of adaptation on the part of the tree?
2. Your pet goldfish is found dead in the aquarium which has
just been cleaned and from which you removed all of the green
plants ? Is this due to a poor adaptation on the part of the fish ?
3. A frog is green with dark spots on the upper surface and white
underneath. Are these colors adaptations? If so, how?
REPORTS ON OUTSIDE THINGS I HAVE READ,
DONE, OR SEEN
1. Report upon an article related to some topic discussed in this
unit. The article may be from a current number of a science
magazine or from some popular science book you have read.
2. Adaptations of a boy or a girl for work in the classroom.
3. Compare the adaptations of the elephant and the giraffe.
4. Discuss adaptations in " Teeth of Animals."
5. How plant seeds are adapted for scattering.
SCIENCE RECREATION
1. Make a list of all the adaptations found in a pet dog or cat.
2. Make a list of strange or uncommon adaptations in plants.
3. Prove that success in the life of some plant or animal depends
upon adaptations.
SCIENCE CLUB ACTIVITIES
1. Visit a museum to study adaptations.
2. Make a field trip to list adaptations in plants and animals.
3. Divide up an area between members of the club and see
which member can give the longest list of adaptations for his area.
REFERENCE READING
Borradaile, L. A., The Animal and Its Environment. Oxford, 1923.
Du Puy, W. A., Our Animal Friends and Foes. Winston, 1925.
Metcalf, C. L., and Flint, W. P., Insects, Man's Chief Competitors.
Williams and Wilkins, 1932.
Guyer, M. F., Animal Biology. Harper, 1931. Chapter IV.
Jordan, D. S., and Kellogg, V. L., Evolution and Animal Life. Apple-
ton, 1907. Chapter XVI.
...
SURVEY QUESTIONS
How do you know that air is all
around you?
Why is air needed for fire ?
Can air be weighed ?
Can you prove that an " empty "
glass is really full ?
How dots air on a tall mountain
differ from air at sea level ?
Do you understand how the barom-
eter is used ?
How does the atmosphere hold
things together?
How do we breathe?
Do you know how much air you
need every day?
How much is " one atmosphere " ?
© Wright Pierce
UNIT III
LIVING IN AN OCEAN OF AIR
PREVIEW
It is commonly said that " we live in an ocean of air."
But you never see air as you do water and there is certainly
no appearance of an ocean when you are in a room con-
taining air, or even when you go for a hike in the open.
What do we mean by this statement ? We know that air
exists, for we feel it when the wind blows ; it holds up our
kites, sails our boats, cools us when we are warm, and when
it is heated, warms us when we are cold. In tires it holds
up our automobiles. It works our compressed-air devices ;
turns wind-mills, stops trains by air brakes, and allows
people to live and work under water in the caisson and
diving bell, Sometimes in storms it blows down houses
and wrecks ships. And, although we may not know just
how we use it, air is necessary for life because living
things breathe it. Have not Piccard and other high
altitude explorers taken oxygen of the air with them into
the stratosphere, and has not Beebe taken it into the
ocean depths in order to exist there?
It has taken a good many people a long, long time to
find out much about air. While the Greek philosophers
knew something about it and even invented some devices
that made use of the fact that air had weight, it was not
until the time of Galileo1 (1564-1642) that it was proved
that air had weight. Galileo did this by first weighing a
hollow copper ball and then forcing air into it until the
air was compressed in the ball. He weighed it a second
Galileo (gal'I-le'o).
43
44
LIVING IN AN OCEAN OF AIR
© National Geographic Society
The start of the stratosphere flight above Rapid City, South Dakota. Do you
know the use of any of the instruments contained in the gondola under the balloon ?
time and found it weighed more. He concluded this
greater weight must be due to the extra air in the ball.
Our knowledge about what the air is dates back a little
more than a century, when Priestley, an Englishman,
separated oxygen out of the air, thus showing it to be a
mixture of gases. Then the Frenchman, Lavoisier,1 dis-
covered that oxygen causes things to burn and an English-
man named Cavendish shortly after found that carbon
dioxide was a gas formed when things burned. Priestley
discovered the gas that made up almost four-fifths of the
atmosphere and Lavoisier named it nitrogen. Recently
small quantities of other gases have been found to be
a part of the air mixture.
As discoveries in pure science are followed by applica-
tions of science useful to man, so the discovery that air
pressure could be measured by an instrument called the
1 Lavoisier (la'vwa'zya').
WHAT MAKES THE AIR USEFUL TO MAN? 45
barometer started a long line of applications in the use of
this instrument. The heights of mountains can be meas-
ured and weather changes can be foretold. The air pilot's
altimeter is a type of barometer with a scale marked off in
distances above sea level. The various things that scien-
tists have found out about the air have been used in thou-
sands of ways to make life more efficient and comfortable.
air*
PROBLEM I. WHAT MAKES THE AIR USEFUL TO MAN?
Demonstration 1. Does Air Occupy Space?
Cut the bottom from a narrow-necked pint bottle.1 Stretch the
open end of a rubber balloon over the mouth of the bottle. Close
the clamp over the neck of the bal-
loon near the neck of the bottle.
Thrust the large open end of the
bottle down into a quart jar half full
of water.
a. Does water enter the bottle?
b. Does the level of water change
in the jar?
c. Explain.
Open the clamp on the rubber
balloon. Notice three things that
happen as a result.
d. Record these three changes.
e. If you find any evidence to
prove that air occupies space, ex-
plain what it is.
Air Is All about Us. Air
makes an envelope for the earth
that extends high above us.
Those of us who have climbed a 10,000-foot mountain
know how hard it is to breathe as we near the summit.
We say that the air has become thin. As a matter of
fact if one could rise above sea level at will, he would
eventually pass out of the atmosphere into space where
1 Process explained on page 77.
46
LIVING IN AN OCEAN OF AIR
f 9ou.-nd.Tng balloons
t
tnati has
,»~
ac
f
clouds ^ highest airplane
A A^iS^k
there is no air. Air is found in water, as can easily be
shown by bringing a glass flask of water nearly " to a
boil." Bubbles of air will be seen to form on the inside
of the flask. Air is also
found in the soil, as can
be seen by packing a
tumbler about half full
of soil and then adding
water. Notice what hap-
pens when the water
soaks into the soil. We
can easily show that air
fills the space in a vessel
we call "empty." The
simplest experiment is to
push an inverted glass
into a vessel of water and
see if anything keeps the
water from filling the
glass. A more interesting
way of showing the same
principle is used in the
demonstration on page 45.
How our atmosphere tapers off. It is 30 Xhe Atmosphere Ex-
times as dense at sea level as it is 15 ^ rm
miles above. » erts Pressure. The
atmosphere is the entire
body of air which surrounds the earth; the term "air"
is commonly used when we refer to any small part of
the atmosphere. Since the atmosphere gets thinner and
thinner as one rises in it, a cubic foot of space at the
earth's surface must have more air in it than a cubic
foot of space several miles above the surface. While
some people say that the air reaches a distance of 200 miles
or more above the earth, about half of it is below the tops
of mountains 3^ miles high. But wherever we are, the
Sea level
WHAT MAKES THE AIR USEFUL TO MAN? 47
atmosphere is always pressing upon us and upon every-
thing it touches.
Air Is a Mixture. In the latter part of the eighteenth
century several men of science, working in their labora-
tories, proved that air consists of several gases, the most
important of which are oxygen, nitrogen, carbon dioxide,
and water vapor. Among other substances in the air are
the gases, argon, neon, and helium. Besides this, there
is a variable quantity of dust, consisting of pollen, soot,
soil, and many other tiny particles of matter. Oxygen
forms about one fifth and nitrogen nearly four fifths of
the air near the earth.
What Causes Rust. You have all seen examples of
rusting : the brown flakes and yellow dust on unpainted
iron fences, unused rails, your knife on a fishing trip, on a
tin can left for a time in a damp place.
Since unprotected iron surfaces are so easily acted upon
by the oxygen in moist air, exposed surfaces of iron are
covered with material which keeps the air from them. A
"tin" can is iron with a thin wash of tin on the surface.
But you know that a tin can will rust. This is because
there are microscopic openings in the tin covering through
which air reaches the iron. A "tin" roof again is tin-
coated iron. To protect it, various paints may be applied.
Steel bridges costing millions of dollars are preserved
for many years by
painting at proper in-
tervals. When iron
is dipped into molten
zinc and withdrawn,
a coat of zinc clings
to the iron, making
What is Called gal-
iron. This
What is rust and what causes rusting? How
could the screen have been protected from rust?
protects the iron even better than the coat of tin.
48
LIVING IN AN OCEAN OF AIR
I
f
Oxygen — a Harmful and Useful Agent. There are
few useful things in this world which cannot at the same
time be harmful or objection-
able. The air is no exception
to this general statement.
Man makes iron fences, iron
bridges, iron mosquito netting,
and sheet iron for cans, dishes,
covering for boats and roofs
of dwellings. Sooner or later
the oxygen of the air may
combine with the iron, making
a worthless mass of iron oxide,
without even strength enough
to hold itself up.
What Substance in the Air
Aids Burning? If one were
to place three lighted candles
on the table and at the same
instant cover them with three
jars of different sizes, would
the candles all burn for the same length of time? You
know what will happen : the candle in the largest jar
burns the longest. The largest jar has the most air, and
there is something in the air that helps things to burn.
Demonstration 2. What Gas Helps Things to Burn?
Fill two wide-mouth bottles, one with oxygen and the other
with nitrogen.1 Place them mouth up, but cover with a small
glass plate.
1. Plunge a flaming wooden splint into the nitrogen. Result?
Plunge a glowing coal on the end of the splint in the nitrogen.
Result?
1 Prepare nitrogen by the following method :
Put bundle of wet steel wool in wide-mouth bottle, put mouth down in
jar of water. Next day remove wool while under water. Close mouth of
bottle, remove from water, and set right side up. The gas in the bottle will
be practically all nitrogen.
Wright Pierce
Why are iron pipes sometimes
unreliable carriers of water ?
WHAT MAKES THE AIR, USEFUL TO MAN? 49
2. Plunge the glowing end of a splint into oxygen. Remove
instantly and cover the jar. Result? Twist a wire around a
small bundle of steel wool. Heat the
steel wool in a flame and immediately
plunge it into the oxygen. Result ?
The results are so striking that
there is no doubt what it is that
helps things to burn. The two
gases, nitrogen and oxygen, appear
to have opposite properties. Nitro-
gen quenches a fire just as water
would, but oxygen causes it to burn
with greater force. Air supports a
flame because of the oxygen in it.
But things do not burn as fiercely in air as in pure oxygen
because of the large amount of nitrogen in the air.
What Is Oxidation ? When a substance combines with
oxygen, the process is called oxidation. When this com-
bination of a substance with oxygen results in a flame,
the process is called combustion. Iron combines with
oxygen when it rusts, but there is no flame ; therefore
this process is oxidation but not combustion.
What Is a Flame ? Flame is defined as a burning gas.
It is easy to understand this in the case of burning manu-
factured or natural gas. When oil burns, it must first be
changed to a gas by heat before there can be any flame.
Have you ever noticed when a candle burns that the wax
melts and is taken by the wick up to the flame ? There
it is changed to a gas which burns, and in doing so, pro-
duces the candle flame. If you hold one end of a glass
tube in the center of a candle flame so as to conduct gas
through it, the gas will burn with a flame at the other end.
Demonstration 3. What Substances Result When a Candle Burns ?
1. Bring a dry pint jar down on a burning candle. When the
candle goes out, remove the jar and quickly close with a glass plate
or cardboard. What appears to be on the inside surface?
H. & W. SCI. I — 5
LIVING IN AN OCEAN OP AIR
2. Pour 50 cc. (about 2 oz.) of limewater into the jar. Close
and shake. There is only one common gas, carbon dioxide, that
causes limewater to become milky.1 If we find a change from
clear to a milky liquid, what does it prove?
What substances does this demonstration suggest are produced
when oxygen of the air combines with the candle?
It may seem strange to you to find that water comes
from the burning of a candle. But if you know that
oxygen in the air is a gas that supports
the burning of the candle, then it is
easily understood. The candle con-
tains hydrogen and carbon. Both of
these elements will burn. The hydro-
gen unites with oxygen and forms
I water (H20). The carbon unites with
oxygen to form carbon dioxide (CC^).
These two compounds also result from
the burning of other substances con-
Where will water appear taining hydrogen and carbon, such as
in the jar after the candle & J
bums for a short time? gasoline, oil, coal, and wood. They
HOW do we know it comes are therefore, always present in the
from the candle ? , . ' , .
smoke coming from chimneys.
The Air Is Useful in Many Ways. The air of the at-
mosphere was just as useful to Columbus as was the
water of the ocean, for while the ocean buoyed up his
1 To show that it is carbon dioxide that turns limewater milky, generate
the gas by adding hydrochloric acid to marble chips in a test tube and
conduct the gas through a delivery tube, making it bubble through lime-
water in another test tube.
WHAT MAKES THE AIR USEFUL TO MAN? 51
vessels, it was moving currents of air, or winds, that
carried him to a new and unknown land. Today the air
buoys up airships,
and propellers push-
ing against the air
can make the airships
move without the aid
of a wind. It is not
merely in mechanical
ways that air is im-
portant. There are
many vital chemical
processes dependent
upon it. Breathing
animals take oxygen
from the air. If the
water were all driven
out of plants, by far
the greater part of the
material left would
be carbon taken out
of the air by the
plant. Since plants
are essential for ani- what causes this boat to move ?
mal life, we can truly
say the air is no less important, for without air there
would be no plants ; nor would there be animals.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank
spaces in the sentences below and arrange the words in proper numer-
ical order. A word may be used more than once.
oxidation
oxygen
out
air
heat
rust
extinguish
combustion
nitrogen
fire
dioxide
oxide
52 LIVING IN AN OCEAN OF AIR
carbon acids kindled cold
water weak chemical put
vapor light action carbon
melt germs hydrogen dark
It is fortunate for us that (1) constantly surrounds us.
If there were no (2) in water, fish would die. The part of
the air that helps things to burn is (3) and (4) which makes
up four fifths of the (5) will (6) a flame. Moist air causes
iron to (7) in a process called (8) Combustion is (9)
in which both (10) . and (11) are produced. Two impor-
tant compounds produced when a candle burns are (12) and
(13) (14) Limewater is used to test for the presence
of (15) (16)
STORY TEST
RUTH TELLS WHY AIR Is USEFUL TO MAN
Read carefully and critically. List all the errors and suggest cor-
rections.
Air is the medium which extends far out into space from the
earth, and if man ever reaches the moon, it will be by sailing
through the air which connects the two bodies. Two bodies of
matter cannot occupy the same space at the same time. It is
for this reason that there is no air in soil or in water. Air is a
mixture. Oxygen and hydrogen make up about 97 per cent of
the air. If there were no carbon dioxide in the air, fires once
started could not be extinguished. A burning candle adds oxygen
and water to the air. Iron can be burned in oxygen. The com-
bustion oi iron is called rusting, and the burning of coal is rapid
oxidation. Paint is used on iron bridges because air hardens the
paint and makes a tough coating, which increases the strength of
the bridge. Limestone is used as a test for carbon dioxide. Air
supplies man with helium for airships, and carbon dioxide for
charging soda water. The most important use of air is for air-
planes and airships.
PROBLEM H. OF WHAT IMPORTANCE IS
ATMOSPHERIC PRESSURE?
Why Air Can Exert Pressure. Have you ever noticed
how dust and other light objects, as loose papers, will rush
ATMOSPHERIC PRESSURE 53
into the space immediately behind a swiftly moving train ?
It is the pressure of the atmosphere that causes air to
Galloway
Why does this rapidly moving train pick up dust and papers directly behind the
observation car?
move into a place from which any object has been re-
moved, and moving air can move other bodies with it.
If we remove the air from a closed space, the air will try
to get back in, and failing, will perhaps push the walls
together. When the air is pumped out of an ordinary
rubber tube which has one end closed, the tube is pressed
until it is flat, just as if a heavy weight had been laid upon
it. A ten-pound block of stone resting on the table presses
down upon the table because the force called gravity is
pulling on the stone. Any body of matter which has
weight will in a similar way exert force upon anything
that is under it. This leads us to ask, "Does air have
weight ?"
Many years ago Galileo, who was the first man in the
world to make extensive use of experiments to answer his
questions, was the first to weigh air. While he used a
copper globe as a container, you could do it in your own
GALILEO GALILEI, 1564 1642.
A S a boy, Galileo, as he liked to be called, showed great promise.
-^- He was a keen observer and a straight thinker, as his com-
panions soon learned. We all know the story of how in the Cathe-
dral of Pisa he noticed that as the great lamp which hung from the
arched roof swung back and forth it always took the same length of
time for its journey. This gave him the discovery of the laws of the
pendulum.
Later he worked out the law of falling bodies by letting two balls
of unequal weight fall from the top of the leaning tower of Pisa.
They reached the bottom at the same time, thus disproving the
belief of Aristotle held for over 2000 years, that heavier bodies fall
faster than lighter ones. He also made the first thermometer and
learned many new facts about light, heat, and air pressure.
But we remember him best for his improvement of the telescope
and his discoveries in astronomy. He was the first to see that
there were moons revolving around Jupiter, to discover the rings of
Saturn, and to observe the rotation of the sun. The movement of
sun spots across the sun's disk proved to him that the sun revolved.
Galileo weighed air and started his pupil Torricelli upon many
experiments involving air pressure and vacuums. It was while
engaged in this work that Torricelli produced the first mercury
barometer.
Galileo was one of the first men to make use of the scientific
method and to apply the test of the experiment in order to learn
new facts and to prove the unchangeable relation between cause
and effect.
ATMOSPHERIC PRESSURE
55
home with a football or a basket ball. Suspend a yard-
stick at its middle point. Hang a fully inflated football
from one arm about twelve inches from the center. The
rubber tube should extend and be closed with a clamp.
Balance the ball exactly with weights on the other arm.
Open the clamp to allow the excess of air to escape. The
ball will rise, showing that it is lighter and has lost weight.
If it has lost air and weight, what is your conclusion about
whether air has weight or not ?
Atmospheric Pressure. Since air has weight, it must
exert force upon the objects upon
which it rests like all other matter.
Torricelli (tor're-chel'le), a pupil
of that great Italian scientist, Gali-
leo, proved that air exerts pressure
by means of the following experi-
ment.
He took a glass tube about three
feet long, closed at one end, and
filled it with mercury. Then hold-*
ing his thumb over the end, he in-
verted it in a cup of mercury. The
column of mercury dropped until
the height was about thirty inches
above the mercury in the cup. This
showed that the pressure of air on
the mercury in the cup was sufficient
to balance a thirty-inch column of
mercury. Torricelli called the in-
strument he used for measuring air
pressure a barometer. Later, when why does the column of
the barometer Was Carried to the top mercury remain at a height
. . . , , , T i /« of 30 inches ?
of a mountain three thousand feet
high, the mercury column dropped about three inches.
Can you explain why?
56
LIVING IN AN OCEAN OF AIR
If you had seven bricks piled one upon the other, how
will the pressure under the third brick from the top com-
pare with the pressure under the bottom brick? Just
lib.
lib.
lib.
lib 1
1 >b.
lib.
lib
lib.
lib.
lib.
Observe that the matter in the pillows at the bottom of the pile is crowded into a
smaller space, thus making it denser. In this respect which is more like the
conditions in the atmosphere, the bricks or the pillows ?
as seven bricks exert more pressure than three bricks be-
cause they have more weight, for that same reason air at
the level of the ocean will exert more pressure than air on
top of a mountain. We would then expect the pressure
at a seaport like New York to be greater than at a moun-
tain city like Denver. The pressure at seaport towns is
14.7 pounds per square inch, or enough to hold a column of
mercury 29.92 inches. It is common practice to regard
30 inches for the barometer or 15 pounds per square inch
as standard atmospheric pressure at sea level.
How the Atmos-
Imile phere Holds Things
Together. If you lay
one square of glass
upon a second glass,
you can easily pick
the first one off from
the second. But if
you wet the two pieces
of glass and place
them together, the
Does the air press down with as much force at Watei> takeS the PlaCG
the top of this mountain as it does at the bottom ? of the air between the
4 mile/
ATMOSPHERIC PRESSURE
57
pieces of glass and fills the entire space. When there is
no air between the pieces of glass, there is no air pressure
tending to sepa-
rate them, and it
is with great dif-
ficulty that you
can pull apart the
two pieces. This
is because the air
on the outside is
E atmospheric
pressure
•glass-
, v • i i Explain this diagram. Can you mention any other
W 1 1 n a devices that make use of this same principle ?
pressing them to-
a
force of about
fifteen pounds to the square inch. After you fill a bottle
with water, put a small piece of wet paper on top and
invert it, what happens? Why? Application of this
principle is made in the disks used for coat hangers,
supports for shelves in display windows, and the ash tray
that clings to the wind shield of the automobile.
A very famous experiment was tried in Magdeburg
(mag'de-boorK), Germany, in 1650. Two metal hemi-
Eiplain this renowned experiment with the Magdeburg hemispheres.
58 LIVING IN AN OCEAN OF AIR
spheres, about two feet in diameter, were placed together,
making a hollow ball, and the air was pumped out of
them. The atmosphere held these two hemispheres to-
gether so tightly that eight horses on each side were
unable to pull the hemispheres apart.
Importance of Atmospheric Pressure. The common
uses of atmospheric pressure are varied and numerous.
From the act of breathing to the measurement of the
height of mountains there are thousands of ways in which
man makes use of atmospheric pressure. It assists in
the pumping of water. The barometer tells how high air-
craft rise, and assists in foretelling weather. Variations
in atmospheric pressure make our winds and storms and
cause droughts and floods. The success of farmers' crops
or of curing foodstuffs in the open may depend upon atmos-
pheric pressure. In the development of life from the
beginning, animals and plants on the earth have been
accustomed to a certain atmospheric pressure, as can be
seen when deep-sea fish are rapidly brought to the surface.
Such fish sometimes actually explode when they are drawn
suddenly to the surface of the water, where atmospheric
pressure is much less than that to which they are accus-
tomed. People who go to the tops of very high mountains
fail to get enough oxygen, and the decrease in air pressure
causes bleeding from blood vessels which break under the
lessened pressure.
SELF-TESTING EXERCISE
Select from the following list of words those which best fill the blank
spaces in the sentences below and arrange the words in proper numerical
order. A word may be used more than once.
weight Aristotle water space
support vacuum push speed
height pounds pressure Torricelli
sea atmospheric weather mercury
ounces square height mountain
cubic force vacant Galileo
HOW DO WE USE AIR? 59
Air can exert pressure because of its (1) At (2) level
the pressure is 14.7 (3) per (4) inch. (5) was the
first to measure the (6) of the atmosphere. He did this by
finding how tall a column of (7) the atmosphere would (8)
Atmospheric (9) decreases as we go up from the surface of the
earth. The barometer, by measuring (10) (11) , is useful
in (12) forecasting, in measuring the (13) of (14) and
to tell the (15) of an airplane.
STORY TEST
ARTHUR TELLS ABOUT THE PRESSURE OF THE ATMOSPHERE
Read carefully and critically. List all the errors and suggest cor-
rections.
Classmates : I have been reading about the pressure of the
atmosphere. Pressure is the force exerted by any body on one
unit area. We speak of anything as being "light as air" because
air has no weight. However, when I hold my open hand out
horizontally, the air or atmosphere is pressing down on my hand
with a force of more than 100 pounds. Galileo made the first
barometer with a long glass tube and mercury. He found that
the air pressure was about 15 pounds on every square foot of area
at sea level. As one goes higher into the air, the pressure increases
roughly in proportion to the elevation. A barometer can be used
to measure the height of a mountain, but an altimeter is used to
tell how high an airplane is above sea level. A barometer could
be used to tell the altitude of an airplane, but the altimeter could
not be used to measure the height of a mountain. When a glass
of water is inverted so that the water runs out, the glass has
nothing in it and is said to be "empty." A space that contains
no matter is a vacuum. When you drink soda water through a
straw, you pull the liquid up by suction. The air is denser in
Death Valley, which is below sea level, than at sea level, but less
dense than on a high mountain. When an automobile moves, it
must push the air away to make a space to move into. The air
pressure on the front of a moving auto is balanced by an equal air
pressure on the rear surfaces.
PROBLEM III. HOW DO WE USE AIR?
How Is the Air Used? Most boys and girls would
not think very long over this question, but what answers
would they give. For breathing, most would say, but not
60
LIVING IN AN OCEAN OF AIR
many could tell how the air was used. It might be easier
to answer the statement that air helps us fly our kites,
sail our boats, hold up toy balloons, and turn toy wind-
mills. Practical boys will at once think of air in bicycle
What holds a kite up ? How do you get a kite up in the air ? Why does the boy
run with his kite?
and auto tires, while a girl might think of a cool breeze
produced by means of an electric fan. Perhaps someone
knows how the air helps fill a fountain pen or a medicine
dropper or at least how it helps you to drink soda water
through a straw. Let us look into some of these uses of
the air and see if we can explain them scientifically.
What Is a Vacuum? Air not only fills what we call
"empty" bottles, but it fills our houses and all outdoor
space. The Greeks had a saying, "Nature abhors a
vacuum," which was handed down from generation to
generation. They knew, as we know, that it is difficult
to keep air out of any space. If air is pumped out of a
jar so that there is nothing in it, we say a vacuum is
HOW DO WE USE AIR?
61
formed. Actually we do not produce a complete vacuum,
for there is always a little air left. It is practically im-
possible to remove all matter from a space, hence we call
any space from which nearly all the
air has been removed a vacuum.
Demonstration 4. Making a Vacuum by
Condensing Steam in a Glass Flask.
Stretch the neck of a rubber balloon over
the neck of a flask which is filled with steam.
As the steam condenses, a partial vacuum is
formed. Explain the action.
A Useful Vacuum Maker. The
demonstration shows how the atmos-
phere presses towards a vacuum.
There are simpler ways of making a
vacuum than by condensing steam.
The rubber bulb is a common and
useful device for making a vacuum.
After a vacuum has been made, it is a
simple matter to get the atmosphere
to work for you. Take the medicine
dropper. Place the open end under water ; squeeze the
bulb. Did anything come out? Release the bulb. The
elasticity of the rubber makes it spring back to its original
size. The air that was squeezed out has left some room in
the tube so that the atmospheric pressure on the water
outside the tube can push water up into the tube. A
fountain pen has a rubber bulb which is squeezed by a
lever to make the vacuum, after which atmospheric pres-
sure lifts the ink into the reservoir of your pen.
The Atomizer. Another use of the rubber bulb in
producing movement of a liquid is in the atomizer used
for perfume or for spraying your throat. This bulb has
a valve so that it can send a series of puffs of air through.
As each puff of air is forced across the open end of the
62 LIVING IN AN OCEAN OF AIR
tube B some of the liquid comes out of B; as the pressure
is decreased inside the tube, atmospheric pressure on the
surface of the liquid inside the container pushes it up
through C. When this liquid meets the current of air
from the bulb, it is caught and separated into a spray of
finely divided particles which are carried along with the
How does the liquid rise from C to B? What causes the fine spray above A?
What is the use of the valve y ?
current of air. Many spray-guns for spraying liquids to
kill garden insects and house moths work on this same
principle, but use a cylinder and piston instead of the
rubber bulb to produce the current of air.
The Air Pump. The hand air pump used to fill bicycle
and auto tires has a piston with a leather facing so
arranged that when the cylinder is full of air and the piston
is pushed in, the air inside is compressed and pushes the
leather against the cylinder wall so tightly that none can
escape there. The outlet pipe is coupled to the tire stem.
There is a valve in the tire stem which allows air to go
into the tire but prevents it from coming out. When the
air in the cylinder is under greater pressure than the air
in the tire, it will pass from the cylinder of the pump
into the tire. A basket-ball or a football pump must
have a valve because there is no valve in the tube of
the ball.
HOW DO WE USE AIR?
63
Why Air in a Tire Will Support a Load. What can
be more useless than a flat tire ? And how different the
tire becomes after it is pumped up. Let us see what
holds the tire out after more air is forced into it. You
laboratory pump
bicycle pump
Explain the movement in the valves A and B during the upstroke and the down-
stroke of the piston. What serves as an inlet valve in the bicycle pump ?
remember that all matter consists of molecules in motion.
Study diagram 1. Here the dots represent molecules of
air, which are constantly moving. They bump into each
other and against the wall of the inner tube. As each
molecule hits the tube
it gives a push. As
a stream of the mole-
cules are pumped into
the tube, they are
squeezed in close to-
gether and in conse- Explain what happens in a flat
quence more and more the tire stay up?
why does
64
LIVING IN AN OCEAN OF AIR
of them hit against the tube (see diagram 2), thus increas-
ing pressure against it. Thus air pressure causes the tube
to bulge out and we say "the tire is up." The tire stays
up as long as it holds these gas molecules, and it goes down
when the number of the molecules decreases so that there
are too few to strike enough blows to maintain the pressure.
A Household Use of the Vacuum. Recall the demon-
stration in which steam drove the air from a flask. When
the steam condensed, the pressure in the flask was less
than that of the atmosphere. In canning fruit and
vegetables, the heat used produces three important re-
sults. It cooks the food, it kills the bacteria that might
cause it to spoil, and it produces steam that drives all the
air out. If the cover is put on before the water present
cools, after the cooling and condensing of the steam a
vacuum is formed. Out-
side atmospheric pressure,
being so much greater
than the pressure inside,
presses the cover on so
tightly that no germs
(bacteria) can get in to
harm the food.
How to Empty a Liquid
from a Vessel with a
Small Opening. Many
people make no use of
their science outside the
classroom because it is
difficult for them to apply
scientific facts and prin-
ciples to new situations.
Did you ever try to suck water out of a bottle that is full
of water having a glass tube passing into it through a
tightly fitting stopper ? Try it if you think you can do it.
.cork
Try sucking water from each of these bot-
tles. Which gives the better result ?
HOW DO WE USE AIR?
65
You can make a vacuum in the tube, but there is no
force to push the water up. If you loosen the stopper,
air can get in and
with its force of
fifteen pounds to
the square inch lifts
the water out as air
replaces it in the
bottle.
Have you seen
anyone pour oil,
sirUD Or Other Rea<* the paragraph and explain the diagram.
liquids out of a gallon tin can having a flat top? They
usually tip the can so that the opening is at the lowest
part of the top surface. Study the diagram. Do you see
that air must enter and push upward through the liquid in
order to displace it ? The flow is jerky and irregular, often
spattering. When the can is lifted up, the liquid runs over
the top of the can. How can one prevent the bubbling of
air up through the liquid and so make a more even flow ?
This is done very simply. Hold the can with the outlet
at the highest level in pouring. The liquid will then flow
out and the air will pass in above the liquid. Some people
prefer to punch a hole through the top at the corner op-
posite the outlet and then the liquid passes out without
interference just as it does from the evaporated milk can
when two holes have been made in the top. If you do
not understand why this helps to make an even flow, ask
to have it explained.
Man's Use of the Air. The most important use of the
air is for breathing. We may go without food for weeks,
without water for days, but we cannot go without air for
much more than a minute. Try to see how long you can
hold your breath. It is said that divers for pearls have
been known to remain under water for two or three
H. & W. SCI. 1 — 6
66 LIVING IN AN OCEAN OF AIR
minutes without breathing, but this is the limit of human
endurance. Incidentally the air all around us presses
upon every square inch of our surface with a force of
nearly fifteen pounds to the square inch. This great
force is necessary to hold us together because the fluids
within us are pressing outward with an equal force. Can
you imagine what would happen to a person who was
suddenly thrust into a vacuum ? Would he die in a short
time because of lack of air for breathing or would some-
thing startling happen quickly? Discuss this with your
classmates and your teacher.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
fan coals piston air atmosphere
bulb reduce sail mass greater
into winds less pushed breathing
cools pressure pump walls vacuum
refrigerator row more valve volume
heats tube increase weight space
Air in motion is useful in many ways. The electric (1)
cools us on hot days. A fan in the automobile (2) the radiator.
Natural air movements as (3) may move (4) boats and
kites. Artificial conditions to make the (5) work for us are
found in devices which are capable of making a (6) For
example, squeezing the (7) of a medicine dropper and then
releasing it produces a (8) If this space containing the
(9) is open to a liquid, the pressure inside the tube over the
liquid is (10) than the pressure of the (11) on the liquid
outside the tube; as a result the liquid is (12) (13) the
tube. Another common device to (14) the pressure and so
make a (15) is the cylinder having a (16) which can be
moved back and forth in it. The bicycle or tire (17) is an
example of this. Air molecules always are pushing against each
other and against the (18) of whatever is holding them, so the
more air we pump into a tire, the (19) the load it can hold
up. The most important use of air is for (20)
HOW DO WE BREATHE? 67
STORY TEST
RALPH EXPLAINS How HE USES AIR
Read carefully and critically. List all the errors and suggest cor-
rections.
I began the day with a sneeze. I used air for that. I did not
use air during the night: I never do. I opened the -faucet to get
water for washing, the atmospheric pressure made the water run
out. I pressed the tube to get tooth paste upon my tooth brush,
air pressure made the paste come out. I squeezed the bulb of a
sprayer to use an antiseptic for my sore throat, pressure of the air
lifted the liquid out of the bottle. Coffee was made for the older
folks for breakfast ; in the coffee percolater pressure of the air
made the liquid spurt out over the coffee. After breakfast I had
target practice with an air rifle and with vacuum-tipped arrows,
both of which make use of atmospheric pressure. I tried to fly my
kite but the atmospheric pressure was too great and I had to give
that up. It was a sunshiny day with absolutely no wind ; the
water was calm — just the time to have a safe trip in my sail boat.
I took a friend across the lake but had to tack coming back. We
pumped up an inner tube to take in with us while bathing. We
made use of the air in the tube, but atmospheric pressure was not
needed as we forced the air into the tube by means of a piston
pump. We went home in an automobile. I noticed a fan under
the hood and I think it drew air into the cylinders so the gasoline
could burn. James and I had a race today. We had gallon jugs
just alike, both filled with water. We were to see who could empty
the water out first. I tipped mine upside down and held it still.
James tipped his as I did but gave it a whirling motion at first to
make the water whirl. I won. I started writing this by electric
light, but the lights went out and I am finishing by candle light,
but the wind blows the flame out every little while. If it were
not for the difficulty of lighting, the candles could be sealed in a
glass bulb just as the wires of the electric lamp are. They would
not blow out so easily then.
PROBLEM IV. HOW DO WE BREATHE?
A Day's Air Supply. Did you ever stop to think how
much air you take into the body in 24 hours? At the
smallest estimate it is over 60 barrels. This seems a lot
of air, for most of us could get inside of a single barrel.
68
LIVING IN AN OCEAN OF AIR
It is possible for you to find out roughly the amount of air
you use by the following home experiment : Count the
number of times you
breathe per minute.
It will likely be some-
where from 12 to 16.
The average breath is
30 cubic inches. Con-
sidering your own size,
about how many cubic
inches of air do you
think you take in at
a single breath ? Find
the amount for one
day by multiplying the
number of breaths per
minute by the volume
of each breath and
then by the number of
minutes in an hour and
by 24, the number of
hours in a day. A
barrel holds about 31^ gallons and there are 231 cubic
inches in a gallon. You take much more air when you
are exercising, since you breathe more rapidly and take
deeper breaths. Then, on the other hand, you breathe
much slower when you are asleep. 4 You must remember,
of course, that your estimate will be only approximately
correct because of these differences.
Why We Breathe. We must think of the human body
as any engine. Just as an automobile engine releases
energy by burning fuel, so the human body likewise burns
or oxidizes fuel to release the energy for daily work. But
our work is done not in any one part of the body, but in
the little units or cells which go to make it up. Evidently
Why can this small boy use so many barrels of
air?
HOW DO WE BREATHE?
69
then, if work is done in the cells, oxygen must get to
all parts of the body in order to release energy there.
To get oxygen there, it is first necessary to get it in-
side the body. Here is where the process of breathing
comes in.
How Do We Breathe? Study carefully the diagram
below. You will notice that the air passage leads from
the mouth down into the chest, where it divides into
two branches and finally breaks up into small branches
which end in a mass of tiny air sacs in the lungs. The
lungs are really spongy masses of air sacs and connecting
tubes. The walls of these little clusters of sacs are lined
with blood vessels, and
when air passes into
them from the outside
when we take a breath,
oxygen gets through
these thin walls of the
blood vessels into the
blood. While this is
happening, another gas,
carbon dioxide, passes
out from the blood into
the air in the little
sacs. Thus we see an
exchange of gases takes
place in the lungs. But
this does not get the
air into the cells ; that
is accounted for by the
circulation of b,lood,
which, as we shall see
later, carries the oxygen to all parts of the body by
means of the red corpuscles and unloads it where it will
be used in the cells.
The breathing apparatus of man. Read the
text and explain how and where oxygen might
get into the blood.
70
LIVING IN AN OCEAN OF AIR
air enter-s
Demonstration 5. To Show How We Breathe.
a. Take a bell jar, insert in the upper end a Y-shaped glass tube,
and fasten over the lower ends of the Y two small rubber balloons.
Over the lower open end of the jar tie a piece of sheet rubber.
Pull on the rubber so that the
cavity inside of the jar is made
larger. What happens to the
rubber balloons?
b. Allow the rubber to go
back to its former position
and press it upward into the
jar. What happens to the
Walloons
fill \vlth,
>i~rS Y>
space s
mcrea-sect.
balloons ?
c. Cover the open tube in
the cork with your finger and
pull down the rubber as before.
What happens?
Explanation. Try to explain from the movements you
have observed why the rubber balloons fill with air when
the sheet rubber is pulled down.
In the experiment let us suppose the rubber balloons
represent the lungs, and the Y-tube corresponds to the
air passages connecting the lungs with the mouth. We
move our ribs outward when we take air into the lungs.
This action is not shown in our experiment. At the same
time we pull down a thin wall of muscle (called the dia-
phragm), which in the experiment is represented by the
rubber sheet. This makes the chest cavity bigger and
pressure of the air in the lungs becomes less than that of
the atmosphere outside. The lungs fill with air, because
it is pushed in by the greater pressure outside. The
higher we raise the ribs, the more the diaphragm stretches
and the larger the space in the chest cavity. So deep
breathing brings in more air than ordinary shallow breath-
ing does.
When the ribs go back into place, the diaphragm is
curved upward into the chest cavity, which is thus made
smaller. The air in the lungs is now under greater than
HOW DO WE BREATHE? 71
atmospheric pressure : in other words, the air is com-
pressed and forced out of the lungs. The process by
which the lungs are enlarged and air is taken into the
lungs is called inspiration; and the process by which
the lungs are compressed into smaller space, forcing out
the air, is called expiration.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
exhaled air compressed pulled
inhaled oxygen upward more
decreases hydrogen cells greater
increases water tissues less
liquid curved blood pressure
dioxide organs lungs lowering
atmospheric carbon atmosphere pushed
Oxygen from the (1) enters the (2) in the (3) and
is then sent to the (4) in every part of the body. Here it gives
up (5) , takes on (6) (7) __, and is returned to the (8)
to be (9) (10) air has more carbon dioxide and less
(11) than normal air. Muscular action expanding the ribs
and (12) the diaphragm (13) the chest cavity, making
the air pressure in the lungs (14) The greater (15)
(16) outside forces air into the lungs. When we exhale, the
air in the lungs is (17) , and having (18) pressure than
that of the outside (19) , it is (20) out.
STORY TEST
FRANK EXPLAINS BREATHING
Read carefully and critically. List all the errors and suggest cor-
rections.
The human lungs are the largest organs in the body. Together
they hold 31^ gallons. When we make the space in the lungs
larger by lowering the diaphragm and expanding the ribs, air from
outside is pushed in under greater than atmospheric pressure.
Pressure on the air in the lungs is never more than 14.7 pounds
72 LIVING IN AN OCEAN OF AIR
per square inch at sea level and decreases as one goes to the top
of a high mountain. One breathes much easier on top of a very
high mountain because the atmospheric pressure is less. In the
lungs the blood takes oxygen and water vapor from the air. None
of the nitrogen taken into the lungs is used by the body. The air
sacs are those small cavities in which the air is never changed. One
generally takes deeper breaths when awake than when asleep. The
lungs become empty after making an expiration so that there is no
air at all in the pleural cavity. This is why we gasp for breath after
running a hard race.
THE REVIEW SUMMARY
In preparing a summary of what you have learned in this unit,
you will want to place emphasis on the big ideas which have come
out of the applications of the facts you have learned and the
demonstrations you have seen. These big ideas we call generaliza-
tions. For this unit they are as follows :
1. The gaseous envelope of the earth, called the atmosphere,
extends upward for many miles, rapidly becoming less dense at
high altitudes.
2. The air contains elements essential both to plants and
animals.
3. Air can be removed from a closed vessel.
4. Atmospheric pressure is of great value to man.
5. The breathing and hence the life of many living things
depend upon both the composition and the pressure of the air.
Before making your review summary, test your knowledge of
the facts of the unit by checking over the text so as to be sure
you know the facts underlying the generalizations. Then, using
the generalizations, the material in the text, and everything you
have read, seen, or done yourself, make a summary outline for your
notebook. This outline you may use when you make a recitation.
TESTS ON FUNDAMENTAL CONCEPTS
Make two vertical columns in your workbook. Head one CORRECT
and the other INCORRECT. Under the first place the numbers of all state-
ments you believe to be correct. Under the second place all the numbers of
the statements you believe to be incorrect. Your grade = right answers X 2,
HOW DO WE BREATHE? 73
I. Air: (1) fills " empty " glasses; (2) is dissolved in water of
falling raindrops ; (3) is a factor in winds ; (4) is present in most
soils ; (5) brings us light and heat from the sun.
II. The air is useful because it supplies us with : (6) oxygen ;
(7) carbon; (8) hydrogen; (9) argon; (10) water for clouds.
III. Exhaled breath contains some: (11) oxygen; (12) nitro-
gen; (13) carbon dioxide ; (14) water vapor ; (15) sulphur dioxide.
IV. Oxygen from the air is used in : (16) rusting iron ; (17) tar-
nishing silver ; (18) fires; (19) electric lamps; (20) making a gas
flame.
V. The following assists one in taking air into the lungs :
(21) muscular action in chest wall; (22) the larynx; (23) the
upward curving of the diaphragm ; (24) atmospheric pressure ;
(25) the movement of blood through the tissues of the lungs.
VI. The pressure of the atmosphere : (26) depends upon the
fact that air has weight ; (27) can be measured with a thermometer ;
(28) will hold up a column of mercury nearly 34 feet high at sea
level ; (29) can be removed from a surface ; (30) is greater at the
top of a mountain than at sea level.
VII. A vacuum: (31) has only air in it; (32) does not contain
any matter ; (33) is useful in making the atmosphere do work ;
(34) is used to make balloons rise; (35) can be made by blowing
all the air out of a bottle.
VIII. Canned molasses and evaporated milk are easily poured
out : (36) from a hole in the center of the top of the can ; (37) when
two holes at opposite edges of the top are made ; (38) from a single
small hole near one edge of top ; (39) from two small holes close
together ; (40) when the entire top of can is cut out.
IX. Expiration in the process of breathing is : (41) to stop
breathing; (42) to die; (43) to exhale air; (44) to inhale air;
(45) to force all air from the lungs.
X. A vacuum can be made in a vessel by (46) condensing
steam in it ; (47) filling with water to get rid of air and then pouring
the water out ; (48) pumping air into it ; (49) blowing through
a tube into a bottle ; (50) by squeezing an atomizer bulb and then
releasing it.
THOUGHT QUESTIONS
1. Oxygen, carbon dioxide, water vapor, nitrogen, and dust
are constantly being taken from the air and they are constantly
being returned to the air. Make a diagram to show the " cycles "
of these substances ; that is, show all the ways by which they are
removed from the air,
74 LIVING IN AN OCEAN OF AIR
2. John wishes to devise an apparatus to measure the air
capacity of his lungs. How can he make it?
3. Gerald has his wind knocked out while playing football.
What are his team mates likely to do for him? Is this the most
effective remedy?
4. Find out and explain why it is so difficult to remove the glass
cover on a jar of canned fruit.
REPORTS UPON OUTSIDE THINGS I HAVE
READ, DONE, OR SEEN
1. Report upon an article related to some topic discussed in this
unit. The article may be from a current number of a science
magazine or from some popular science book you have read.
2. Galileo, an experimental scientist.
3. Trips made by man into the stratosphere.
4. Uses that boys and girls make of air.
5. Rare gases of the atmosphere.
SCIENCE RECREATION
1. If the tube is inverted, what evidence will indicate that air
cupies Fpace?
2. What will happen when the clamp C is
flp-__~wi~~ occupies
____ Ctr"
opened? Explain why.
• »«t JiMffl (MHW\\T\>CZX<^nt'H~» ^fcw_ *.
-deflated:
balloon
3. MAKE A FOUNTAIN-IN- VACUUM
Procure an 8-oz. bottle, a 1-hole stopper to fit it, and a glass tube
12 inches long. Soften the glass tube in the middle in the flame.
Draw it out to a fine thread. Break off the fine thread so there
is only a small opening leading out of the glass tube. These tubes
are called jet tubes. Wet one of the tubes and place it in the
stopper, so that a jet end (small opening) will be inside. Never
push a glass tube into a stopper when the stopper is in the bottle.
Hold the bottle in a towel over the nose of a steaming teakettle
for a few minutes. WJien the steam has driver; the ajr out. cork
HOW DO WE BREATHE?
quickly and tightly. Immediately dip the glass tube into a glass
of water. As the steam cools, what condition results in the bottle?
Explain why the water rushes in and forms a fountain.
A
Voter.., flf-
., ^balloon.
air-
4. What will happen when A blows through the tube? Explain
why.
5. What will happen if one sucks air from the large bottle
through A? Explain reasons for two results which you can see.
6. Make a booklet of clippings, " Air and Its Uses." Use
pictures and articles.
SCIENCE CLUB ACTIVITIES
1. ATMOSPHERIC PRESSURE AND VACUUM DEVICES
Ask every club member to bring to the club meeting something
which uses vacuum or atmospheric pressure, or both, in its opera-
tion. He should be expected to demonstrate or explain to the
group just how his device works.
2. GALILEO AND TORRICELLI
Reports on the scientific works of these early scientists.
3. FOUNTAINS: A GOOD WAY TO MAKE A FOUNTAIN
A. Gravity Pressure
The tin can has a tight- fitting stopper with a tube passing through
it. This is joined by a rubber tube to the jet tube in the glass
76
LIVING IN AN OCEAN OF AIR
bottle. A hole is punched through the can
near the bottom to allow air to enter the
fountain. Water may run out. The higher
the reservoir is placed above F, the greater
the force in the fountain.
4. EXPLORING IN THE UPPER ATMOSPHERE
Read up on this topic in books and
periodicals. Find out what people have
explored the atmosphere higher than the
highest point of land and how they have
done it. What do they expect to achieve by
these adventures? What are the dangers?
Have different members of the science club
report upon different achievements.
5. How TO SHOW THE CRUSHING POWER OF
THE ATMOSPHERE
Use an empty gallon oil or sirup can which
has a small opening that can easily be closed
air tight with a cork. Put about one half inch
of water in it. Place it over a fire, and boil
the water. When the steam has driven out
all the air (two minutes of boiling), shut off
the gas and put the stopper in air tight. Place
the can in the sink and pour cold water upon
it. Do you understand the reasons for the re-
sult? How many square inches of surf ace has the can ? What is the
pressure of the atmosphere on 1 sq. in.? On the total surface?
6. How TO SHOW THE CHANGES THAT TAKE PLACE IN THE CHEST
CAVITY WHEN WE BREATHE
Have some member of the club make a large chart of the diagram
shown on this page and
a large model of the me-
chanical device shown
on the opposite page.
Have the club members
study the chart carefully
and then have the dem-
onstrator work the model
while asking the follow-
ing questions :
(1) What happens to
the human diaphragm
when the ribs are raised ?
„
HOW DO WE BREATHE?
77
(2) What happens to
the human diaphragm
when the ribs are lowered ?
(3) What causes air to
come into the lungs?
(4) What causes air to
pass out of the lungs?
The chart and appara-
tus should be presented to
the science department of
the school for class use
after the meeting. It will
be valuable for class dem-
onstrations.
..cardbooret
-brass -fastener
atrctboccrcC strip
...papci
7. How TO MAKE A BATTERY JAR FROM A BOTTLE
Cut the top off a large glass bottle or jar — one quart or one
gallon — the larger better. Make a deep file scratch where you
wish to cut it. Heat a heavy metal — soldering iron or curling
tongs — red hot and press upon the scratched glass. After a crack
is started, keep applying the red hot metal just a little ahead of
the crack and it will follow it around. Another method is to wet
a cotton string with kerosene. Wind two or three layers around
the bottle and tie. Set fire to the string, holding the bottle hori-
zontally and turning slowly. When fire goes out, wet the bottle.
This jar will be very useful in many experiments.
REFERENCE READING
Archibald, D., The Story of the Earth's Atmosphere. Appleton,
1915.
Compton's Pictured Encyclopedia.
Houston, E. T., The Wonderbook of the Atmosphere. Stokes Co.
Meister, M., Water and Air. Scribner's, 1930.
Talman, C. F., The Realm of the Air. Bobbs-Merrill, 1931.
SURVEY QUESTIONS
Why is water so important to man?
Is water in nature always pure ?
Do you know which is hotter, boiling
water or steam ?
What is the water cycle in nature ?
How does water get to oceans,
rivers, clouds?
How can water be made safe for
drinking purposes ?
What is water made of?
How is the purest water produced
artificially on a large scale?
Do you know what makes water rise
in the soil ?
Dawn Mist Falls. Photo by Hileman
UNIT IV
WATER AND ITS EVERYDAY USES
PREVIEW
Did you ever think what the world would be like with-
out water? There could be no rainy days, no snow
storms, no coasting or skating, no bathing, swimming, or
sailing, and no water to drink. Without water there could
be no plants, hence no vegetables or fruits, no animals
and no food for man. You can readily see that without
water on the earth there could be no life, not even man.
The nearest thing to a waterless earth is found in the
desert, but even in this parched and dry area there may
be a few springs or pools of water left after a desert storm.
Mile after mile of shifting sand, no plants except
an occasional cactus, and a few dried-up bushes ; perhaps
a snake, a lizard, or a desert mouse, and once in a while
a bird is all the life that we see. But visit this same spot
after the spring rains have swept down from the moun-
tains, and we find the whole desert floor covered, as if by
magic, with little plants having many bright-colored,
red, magenta, blue, and violet blossoms. Even the
dried-up desert bushes have put on leaves and are in
flower. All these changes have come because of the
temporary presence of water. Some deserts, such as
the Sahara, however, are so unfavorably situated that
they do not receive enough water to sustain life at any
time of year. Such places are a barren wilderness and
sometimes so extensive that it is with great hazard that
man attempts to cross them.
79
80
WATER AND ITS EVERYDAY USES
The desert in California before the rainy season. Note the dry sandy foreground.
Water is one of the most important factors of our
environment. While there are some living things like
earthworms and some fish that can get on without light,
and while there are some animals and plants that can
live in a very low or a very high temperature, none of
them can get on without water. We even know of some
plants that can live without air, but these plants, tiny
bacteria, get oxygen from their foods and must have
water in order to grow. Living things need water be-
cause they are largely composed of this substance.
Pure water is one of man's most desired possessions.
It comes from the clouds and after a long or short stay
with us goes back again. The adventure of a drop of
water would make an interesting story. Dropped from
the clouds as rain, it might fall into a river and from there
pass into a large body of water, where it would stay until
THE WATER CYCLE
81
The same spot after the winter rains. Compare the trees in the background in
both pictures and you will see the photographs are taken at the same place. How
do you account for the difference?
the hot sun caused it to evaporate into vapor and pass
again into the clouds. Its next trip might take it to a
forest, where it would fall into the ground, remain there
for a time, be absorbed by the roots of the tree, and pass
up through the stem to the leaves, where perhaps it could
be used by the green leaves of the tree in the manufacture
of food. Or perhaps it might be evaporated through the
holes in the leaf as the tree made food in the sunlight.
Again in the air it might be condensed as dew and
then get into the soil again. Eventually, however, our
drop of water would become a part of the vapor of the
air, would become condensed, and again come back to
the earth as rain, or snow, or hail. This continual round
of water is known as the water cycle.
H. & w. sci. i — 7
WATER AND ITS EVERYDAY USES
PROBLEM I. WHAT IS WATER?
Those of you who live where snow falls in winter have
had the experience of a cold rain changing first to sleet
and then to snow.
You have at some
time brought ice and
snow into the house
and seen it change
back to water. Per-
haps you have placed
it in a vessel over
the fire and watched
it pass off into the
air as steam. You
What kind of changes are taking place here? have all seen water
How do you know ? . ,-, ,,
in the three states
— solid, liquid, and gas. But in all of these conditions,
its molecules are still made up of the same elements.
How Scientists Found Out the Composition of Water.
Water is so common it seems absurd at first to ask, " What
is water?" And yet if any one asked you the question,
what would you answer? Is water an element? Is
it a compound? Does it contain several things mixed
together? The chemist has at his command several
methods by which he can solve such a problem as this.
As long ago as 1784, Henry Cavendish burned hydrogen
in oxygen and produced a liquid. This liquid he found
had all the properties of water and in fact was water.
Sixteen years later, two chemists, Nicholson and Carlisle,
reversed the process of Cavendish. They began with
water, and by using electrical energy tore the molecules
apart and produced hydrogen and oxygen. This process
is reproduced now in thousands of schoolrooms every
year. The process is called electrolysis of water and is
WHAT IS WATER?
83
carried out as follows : The jar has two coils or plates
of platinum (A and B) extending upward into some
water which has been made acid by having about a table-
spoonful of strong sulphuric acid added to half a pint
of water. The test tubes are each filled with this water
\*y
cell
drx
cell
drx
cell
dry
cell
• switch.
Electrolysis of water. What does this experiment show about the composition
of water ?
and placed over the platinum wires. The acid is used
to make the water conduct the electric current When
the current from four dry cells is sent through the water,
small bubbles rise from the platinum wires and collect
in the tops of the tubes. One gas forms twice as fast
as the other. If this gas is removed and lighted, it burns
or pops with a slight explosion. This gas has been proved
by experiment to be the element hydrogen. When the
other tube of gas is tested with the glowing end of a splint,
it causes the splint to burst into flame. The gas is the
element oxygen. These two elements have come from
the water because the chemist finds that there is the same
quantity of sulphuric acid left as he used at the beginning.
We may now conclude that pure water is a compound
made up of hydrogen (2 parts) and oxygen (1 part).
This is expressed in the familiar formula H2O.
What Is Pure Water? Water in its purest natural
state is rain water. It comes from the clouds, where it is
84 WATER AND ITS EVERYDAY USES
made from pure water vapor which was condensed high
in the air, therefore having little opportunity to get any
impurities into it. We can make any water pure by
distilling it, because this process forms water in much
the same way that it is made in the clouds.
Demonstration 1. To Show How Water May Be Purified.
Place a Florence flask on a ring stand, and bend a tube as shown
in the illustration. Pass it through a perforated cork which will
fit in the mouth of the flask.
Fill the flask half full of water
colored with red ink and add
one teaspoonful of salt and two
of sugar. Place a lighted Bunsen
burner under the flask and put
a test tube at the lower end of
the tube. Allow the tube to
stand in cold water to keep it
cool.
Observation. Soon after the
water boils, notice what happens.
Where do the drops of water
appear? Why do they appear
more frequently here? What is
the color of the water in the
test tube? Taste it. Result?
What substances put into the
flask do you find in the test tube ? This process of obtaining water
is called distillation. How does distillation purify water?
Distillation. Distillation of water is very important.
It involves two distinct processes : vaporization, in which
the water is changed to steam, and condensation, in which
the steam is changed back to water. Natural waters,
which contain some impurities, if put into the storage
battery of the automobile would soon ruin the battery.
When large quantities of artificial ice are made, unless
the water is very pure it is first distilled before freezing.
When a large can of dirty water is freezing, the im-
purities separate and move to the center of the can
where the water is frozen last.
WHAT IS WATER?
85
What Is Evaporation ? When ice is left in a hot kitchen
uncovered, it absorbs heat and soon changes its state
from solid to liquid, and if it is left exposed to the air for
a short time, some of it will pass off into the air. Evap-
oration is the changing of water to a gas when the change
is at the surface of
the liquid. Some
water evaporates
into the air when-
ever air and water
are in contact. The
warmer it is, the
faster it evaporates.
The Water Cycle
in Nature. Air, soil,
and living , things
play an important
part in the ceaseless
changes of water on
our earth. The at-
mosphere receives
water in the form of water vapor and gives it back in a
variety of ways. Evaporation of water from all surface
bodies of water, from wet rocks and soil, and even from
snow and ice charge the air with moisture. To this must
be added the moisture given off from the burning of fuels,
by the breathing of animals, and from trees and other
plants. A single tree sometimes gives off almost half a
ton of water in a day. This water vapor in the air is an
invisible gas. When air that has become saturated with
moisture is cooled, some of the water separates out into
minute particles. Continued cooling increases the size
of the particles. The particles may make dew drops, fog,
clouds, and rain, or if the temperature is very low, frost
or snow will result. The great bulk of this condensed
Read the text and then explain this diagram of the
water cycle.
86 WATER AND ITS EVERYDAY USES
Galloway
Is the sun really drawing water? Explain the picture after reading the text.
water will come back to the earth from the atmosphere
in the form of snow and rain. This return of the water
makes the earth moist ; fills the rivers and ponds ; and
supplies animals and plants with the necessary water.
Evaporation then starts another cycle and the process is
continued. Thus there is on the earth a never-ending cycle
of water from solid or liquid to gas and back again from
gas to liquid or solid. This is the water cycle in nature.
Sometimes there are many tiny particles of moisture in
the air. They are too few to form a cloud but sufficient
to reflect and show rays of sunlight. This phenomenon
is responsible for the saying, "The sun is drawing water."
Clouds at a higher level often have "holes" in them and
sunshine passes through. If small particles of water or
dust are in the air lower down, the beams of light become
visible just as they do when shining into a dark attic or
barn chamber through a knot hole or other small opening.
WHAT IS WATER? 87
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
nitrogen evaporation impure mixture
composition boiling cheap electrons
compound union hydrogen oxygen
elements twice oxygen separated
rain costly water method
pure molecules gas solution
purifying distillation distilled stream
Water is a (1) formed by the (2) of the elements
(3) and (4) When water is separated into its (5) ,
it is found that there is (6) as much hydrogen as (7)
When solids are dissolved in water, the water can be (8) from
them if heat is applied. Heat causes some of the (9) of pure
water to change to a (10) which leaves the (11) This
process of (12) a liquid is called (13) The purest water
that we make artificially is (14) water. When hydrogen
burns (15) results which is also (16) , but this (17) ,
of producing (18) would be very (19) When distilled
water is not available, the next purest water we can get is (20)
water.
STORY TEST
CATHERINE REPORTS ON "WHAT Is WATER?"
Read carefully and critically. List all the errors and suggest cor-
rections.
It seems almost too commonplace to tell you what water is.
How can one ever be in doubt ? A glass of milk is white, ginger ale
is amber and has bubbles in it, sulphuric acid is very heavy, and
gasoline has an odor. If I can see, lift, and smell a liquid in a glass,
I can tell if it is water. Some may say a glass of lye (caustic soda
in water) or potassium cyanide solution would look the same as
water and could not easily be told by weight or odor. Even if this
is true, you could tell the difference after you drank them, so what
does it matter? The chemist tells us that water is made of hydro-
gen and nitrogen and that the amount of hydrogen is double that
of the other compound. When water is boiled, it goes off in two
separate gases, one of which will burn. Natural water is always
pure water, but the artificial water made by vaporization and
condensation is almost always impure. We have read a lot about
heavy water recently. That is water that has lead in it.
88
WATER AND ITS EVERYDAY USES
PROBLEM II. WHAT USES DO WE MAKE
OF WATER?
Uses of Water. If you were to make a list of all the
ways in which you use water, you would doubtless think of
its first uses in the morning for washing your body, clean-
ing the teeth, and then drinking at breakfast. Keeping
clean is certainly important. If a Roman Emperor
wished to become popular with his people, he caused a
bathhouse to be built. The Romans took their bathing
seriously. They had magnificent bathhouses with hot
and cold showers or tubs, and the wealthy Roman lounged
away a good part of the day enjoying the various steps
of his complicated bath. It was the place where a Roman
gentleman sat and gossiped and swapped the day's news,
for there were no newspapers. They knew the value
of a clean skin, and knew the feeling of exhilaration that
came from a cold bath following a warm one.
A Roman bath in Bath, England. When the Romans invaded England they built
baths like the ones they had in Rome.
WHAT USES DO WE MAKE OF WATER? 89
Why Keep Clean? There are two reasons why we
should keep ourselves and our clothing clean. First
because we wish to be decent and attractive to others,
and second because good health demands that we keep
our clothing and bodies free from dirt and germs.
What Makes Water So Useful? The uses of any kind
of matter are determined very largely by its properties.
Water is no exception. The form in which water exists,
whether solid, liquid, or gas, determines some of its uses.
We cannot wash clothes in ice nor can we skate on steam.
What do you suppose makes water sometimes liquid,
sometimes solid, and at other times a gas ? After a little
thought you will say correctly that heat determines the
state in which water exists.
In general it is true that the warmer the water the more
solid the water can dissolve, but at any given temperature
there is a limit to the amount that it can hold. When
water has dissolved all that it can at a given temperature
it is said to be saturated. If a saturated solution is
cooled or if it loses water by evaporation some of the dis-
solved solid will separate from solution. With gases the
temperature effect is just the reverse. The warmer the
water the less gas it can hold in solution. Boiling the
water will remove all gases which are in solution.
Demonstration 2. Water as a Solvent.
Arrange six test tubes half full of water in a test-tube rack.
Add a gram of each of the following substances, each one in a
separate tube: (1) salt; (2) sugar; (3) oil or grease; (4) charcoal
or ashes ; (5) soap chips ; (6) baking soda. * Shake to see if each
substance will dissolve in the water. Tabulate the results.
Practical Application. Why will water clean some dirt spots
more readily than it will others?
When a small portion of salt or sugar is put into water
and stirred, the salt or sugar disappears. Water has
dissolved the solid. Neither an iron nail nor a silver
90
WATER AND ITS EVERYDAY USES
spoon will dissolve in water. Water has the property
of dissolving some substances which are called soluble ;
• lilll
Wright Pierce
Try an experiment like this and see what results you get.
those substances which will not dissolve are insoluble.
A liquid which will dissolve a substance is called a solvent
of that substance. Every part of a breakfast cereal
can be salted evenly if the salt is
dissolved in the water before the
cereal is added to the water.
How to Make Oil and Water Mix.
You often hear the saying that
" water and oil do not mix." You
can prove it if you wish and then
you can disprove it. Suppose you
put half a cup of water into an 8-oz.
bottle and add a tablespoonful of
kerosene Or fuel oil to it. Close
the ^^ and shake it vigorously,
shaking. Upon standing, the oil quiekly
WHAT USES DO WE MAKE OF WATER? 91
separates. You have proved that water and oil under
ordinary conditions do not mix. Now start again, but put
a few shavings of soap in the water. Shake to make
a soapy solution. Add the oil and shake vigorously
as before. This time the oil does not separate from the
water. Shaking divides the oil into many exceedingly
fine droplets. 'In water alone they quickly combine and
separate out from the water, but when coated with soap
which is in the water, they keep their finely divided state
and remain mixed with the water for a very long time.
Thus you have shown that when soap is present to lend
its aid, water and oil will mix. This mixture is different
from solution and is called an emulsion. A kerosene
emulsion is an insect spray used to kill aphids. Milk
is an emulsion. It has oil in the form of butter fat dis-
tributed in very fine particles. These rise very slowly,
and when they form a layer on top of the milk, they are
known as cream.
Value of Soap in Cleaning. It is largely the grease and
oils that hold the dirt particles to the hands and clothing.
Water alone has little cleaning value because it cannot
remove the oil. But when soap is added to the water
it forms an emulsion with it and this loosens the dirt.
For this reason soap is a valuable cleaning aid. When one
lives where the water is hard, containing minerals like
calcium compounds in the water, the soap is destroyed.
Such water must be softened sometimes by boiling, some-
times by adding washing powder or other chemicals
before using soap. Otherwise a great deal of soap will be
wasted.
Why We Need Water. Do you know that your body
is over 65 per cent water, and that some animals such
as the jellyfish are 99 per cent water? Have you thought
that the plants we eat, stems like celery, roots like
radishes, all contain a large per cent of water, and that
92 WATER AND ITS EVERYDAY USES
most foods, even though they seem dry, contain quite
a good deal of water? Our doctors tell us we should
drink from six to eight glasses of water a day, some of
which may be taken in the form of milk. We can see
a reason for this now that we know that all foods and
our own body contain so much water. Water is also
used not only to carry foods from one part of the body to
another, for foods have to be dissolved in the blood before
Do all living things contain water? Mention something that
does not.
they can be used, but it is used in the growth and repair
of the cells of our body. If we examine a young growing
shoot of a plant, we will find that the rapidly growing
part is much softer and juicier than the older parts. This
is because it contains more water. Not only is water
used in the body to transfer foods, but it is also necessary
to get rid of wastes. Some of the most poisonous body
wastes are passed off in the urine and in perspiration.
How We May Make Water Safe for Drinking. Many
of us have visited friends in the country and remember
with pleasure the cold water from the wells or springs
near their homes. But a glance at the picture will show
WHAT USES DO WE MAKE OF WATER?
93
that such water might be very unsafe. If water is taken
from a well, the well should be protected by a cap of
cement, as shown in the diagram, and it should be so
located that drainage cannot enter it. Well water should
be tested frequently
for germs by town
or state Boards of
Health. A well in
ordinary sandy soil
situated above and at
least 100 feet from
any cesspool is safe.
You may go camp-
ing and be in doubt
about the safety of
your water supply.
Boiling it for 20 min-
utes will kill prac-
Compare the conditions of these two wells.
Under what conditions might the water in B be
safe ? When unsafe ?
tically all harmful
germs and will make
it safe for drinking.
Unfortunately, boiling drives off the free oxygen and
gives it a flat and unpleasant taste. The oxygen can
be put back into the water by violently shaking it for a
short time in a bottle partly full of air.
Water Used in Cooking. Water is also used to cook
foods in. We make our bread by mixing flour with water
to form dough. We make our tea and coffee because of
the solvent action of water which extracts the flavor
from the tea leaves or the ground coffee so that the liquid
has the flavor instead of the original tea and coffee. We
can also transfer heat by means of water or steam, as you
see when you cook a cereal in a double boiler.
Other Uses of Water. We have seen that both plants
and animals are made up very largely of water. This
94
WATER AND ITS EVERYDAY USES
A miniature yacht race. Do you know how to sail a boat into the wind ?
accounts for the fact that our gardens, lawns, and plants
kept in the house need constant watering. We know
that they wilt when they do not have sufficient water.
Moisture evaporates from bodies of water into the air.
We have all had the experience of sitting in the draft of
an electric fan in order to cool off. Nature adds moisture
to the air in a large way when breezes blow over large
bodies of water, or when great forests send off into the
air large amounts of moisture. Water helps us to keep
more comfortable, and communities near large bodies of
water have usually a pleasanter climate than those far
away from sources of water. Finally, water is used in our
recreation. Every boy and girl ought to know how to
swim and sail a boat. Rowing, canoeing, and fishing
are all recreations that depend upon water.
Life in the Ocean. In addition to all the other uses
of water, we can add perhaps the most important of all,
the fact that water is the home of vast numbers of living
things. Think of the amount of the earth's surface
WHAT USES DO WE MAKE OF WATER?
95
covered by water — three fourths of it. Think of the
thousands of forms of fish life that dwell in our oceans.
Go to a museum and see the groups showing underwater
life — sponges, corals, sea anemones, jellyfish, sea fans,
and sea feathers, hundreds of kinds of worms — flat,
round, or jointed. And besides these there are millions
of tiny one-celled animals, sometimes so plentiful that
although microscopic in size, they give color to the ocean
and furnish food for hundreds of kinds of bigger animals.
Variety of Life in Ponds. In addition to the larger
bodies of water our brooks and ponds swarm with life,
both plant and animal. All kinds of life may be found
there. Frogs, turtles, salamanders, and snakes are in
Wright Pierce
Have you ever gone fishing ? There are bass and trout in this lake. What else
do you think you could find on the shores or in the water ?
96 WATER AND ITS EVERYDAY USES
the water or on the banks, while snails, mussels, clams,
slugs, and worms of various kinds may be found on the
mud of the bottom. Then there are fresh-water sponges
which look like plants ; little green or gray hydras, and
thousands of tiny water fleas which form the food of fish
and other inhabitants of the pond. It is true that there
are many animals which can live in water or in air, but
many of these begin their life in water. Mosquitoes, flies,
and dragon flies live in water in the earlier stages of their
existence, emerging into the air only for their adult life.
The mud at the bottom of the pond will disclose numerous
insect larvae. The surface film, the water, and the
muddy bottom will all reveal interesting forms of life.
Over 70 different forms of life have been found in one
eighth of a cubic inch of water when examined with a
compound microscope. The water is more densely
inhabited than the air or the land.
American Museum of Natural History
This is a glimpse of pond life as seen under a magnifying glass.
Can you name any of the things you see in the glass ?
WHAT USES DO WE MAKE OF WATER? 97
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
salt bluing solution 56 steam acid
liquid solid ice boil gas boiling
solvent dissolve form heat evaporation fuels
mix soap emulsion mixture washing dissolves
oils water boiling oil 65 freezing
Water is ordinarily a (1) , but in very cold regions it is a
(2) called (3) When heated strongly on the stove,
water will (4) , but if left in the open air, it changes to a (5)
in the process of (6) When salt is stirred in water, it disap-
pears because water is an excellent (7) Water will not
(8) insoluble substances. The (9) or condition of water
is determined by the amount of (10) it contains. Oils which
do not readily (11) with water are made to do so by the
addition of (12) The result is called an (13) In the
process of cleaning, water is aided greatly by the addition of
(14) Much of the dirt we try to remove in the process of
(15) is held by fats or grease or (16) Soap in (17)
forms an (18) with the fat or (19) and so loosens the dirt.
People need to drink much water because it helps carry foods
and remove waste and because the body itself is (20) per cent
water.
STORY TEST
ALTON RELATES His EXPERIENCES ON SOLUBILITY
Read carefully and critically. List all the errors and suggest corrections.
I will tell you of my experiment on testing solubility of substances
in water which I did at home. I found that water will dissolve
salt and " absorbent " cotton. I presume this kind of cotton is
called " absorbent " because the water absorbs it and makes a
solution of it. Water will not dissolve ashes or soap chips. I
found that oil would not dissolve in water alone, but if I put soap
in the water with the oil and shook or stirred vigorously, the oil
did not separate. This is because it had dissolved in the water. I
boiled some water from a deep well until the water disappeared ;
a small amount of solid was left. I put coffee grounds into water
and boiled it. I poured the liquid off and the grounds were left,
therefore there is no solution formed when one " makes coffee."
H. & W. SCI. I — 8
98 WATER AND ITS EVERYDAY USES
One reason you do not notice the adulteration of sugar with sand
is that the particles look alike and they are all completely dis-
solved in water.
THE REVIEW SUMMARY
In preparing a summary of what you have learned in this unit,
you will want to place emphasis on the big ideas which have come
out of the applications of the facts you have learned and the
demonstrations you have seen. These big ideas we call generaliza-
tions. For this unit they are as follows :
1. Water in all its three states, solid, liquid, and gas, produces
important changes on the earth.
2. Water is a compound that can be separated into its elements.
3. Through a variety of changes in state, water passes through
a cycle in nature.
Before making your review summary, test your knowledge of
the facts of the unit by checking over the text so as to be sure you
know the facts underlying the generalizations. Then, using the
generalizations, the material in the text, and everything you have
read, seen, or done yourself, make a summary outline for your note-
book. This outline you may use when you make a recitation.
TEST ON FUNDAMENTAL CONCEPTS
Make two vertical columns in your workbook. Head one CORRECT
and the other INCORRECT. Under the first place the numbers of all state-
ments you believe to be correct. Under the second place all the numbers
of the statements you believe to be incorrect. Your grade = right answers
X 3£.
I. The air receives water from : (1) the ocean ; (2) breathing
animals ; (3) condensation of moisture ; (4) living plants ; (5) deep-
sea fish.
II. When common salt is dropped slowly into boiling water:
(6) it forms crystals on the bottom of the dish ; (7) a solution
results ; (8) an emulsion is formed ; (9) the water becomes a
solvent ; (10) the salt is a solvent.
III. Water is a compound whose molecules are composed of :
(11) two atoms of hydrogen; (12) like atoms; (13) oxygen and
WHAT USES DO WE MAKE OF WATER? 99
nitrogen ; (14) two electrons and one proton ; (15) one part oxygen
and two parts hydrogen.
IV. In the process of making distilled water : (16) two changes
of state are required; (17) a source of heat is required; (18) a
source of cold is required to remove heat; (19) pure water must
be used to start with ; (20) sea water cannot be used.
V. A water is safe to drink if it has been: (21) formed by
melting glacier ice ; (22) freshly distilled ; (23) filtered through
five layers of cloth ; (24) taken from a river ; (25) boiled 20 minutes.
VI. Living things in water : (26) may be more numerous than
in an equal sized volume of land ; (27) are all microscopic in size ;
(28) are all animals, no plants being found there ; (29) often only
pass part of their lives there ; (30) all have to come to the surface
to breathe as there is no oxygen in the water.
THOUGHT QUESTIONS
1. Why will water clean some dirt spots better than others?
2. What is a solvent? Find the names of three solvents and
name one important use of each.
3. Does milk hold cream in solution? What makes cream rise ?
4. If hydrogen will burn in the presence of oxygen, why doesn't
the hydrogen burn in water when water is composed of one atom
of oxygen and two atoms of hydrogen?
REPORTS UPON OUTSIDE THINGS I HAVE
READ, DONE, OR SEEN
1. Report upon an article related to some topic discussed in
this unit. The article may be from a current number of a science
magazine or from some popular science book you have read.
2. The waters of the earth.
3. Trips made by man down into the ocean.
4. Uses boys and girls make of water.
5. Water : in and out of the air.
SCIENCE RECREATION
1. MAKE HYDROGEN BALLOONS
Prepare hydrogen gas from dilute hydrochloric acid by action
on zinc scraps. Carry the gas through water to wash it. The
hydrogen is discharged from the end of a fire polished glass tube
100
WATER AND ITS EVERYDAY USES
or a clay pipe. Dip the end of the glass tube into the soap solution.
Remove quickly. When the bubble is an inch or two in diameter,
tutfck
4.
basket/
shake it off and watch its movement. Do not have any flame
near the hydrogen generator. When mixed with air, hydrogen
will explode violently upon the application of a flame.
2. MAKE DISTILLED WATER
Devise an apparatus using things
you have at home and make distilled
water for the automobile battery.
3. CRYSTAL MAKING
Make crystals by allowing saturated
solutions of salts to evaporate slowly.
Suspend strings in the liquid for the
crystals to cling to. They will also
form on the vessel holding the solution.
Salts that are good for this are : com-
mon table salt, alum, potassium dichro-
mate, and copper sulphate. If you
start with a hot saturated solution,
crystals will start to form as the solu-
tion cools. Make a basket form of
cotton-insulated wire #20. Suspend this
in a hot saturated solution of potassium
dichromate. A beautiful crystal orna-
ment will be produced by allowing
crystals to grow upon this for 24 hours.
\\idC- -
£ concentrated
f salt. ^
I -Solution
SCIENCE CLUB ACTIVITIES
1. TOY RIVER BARGES
Materials needed: Three half walnut shells; three small cork
stoppers ; stick of wood about size of pencil ; paraffin.
Preparation: Cut the corks into halves and fasten them with
paraffin to the ends of the shells so that there will be a smooth
WHAT USES DO WE MAKE OF WATER? 101
vertical surface when the shells float in water. Have the top of
the cork come just level with the top of the shells. Liquid solder
may be used in place of paraffin.
There is a film over the surface of water like stretched rubber.
The force of this film on water is great enough to hold the toy river
barges together if they are brought end to end. The whole line
of them can be drawn along by holding one end of the stick in the
water just in front of one and pulling slowly.
By pinning a small piece of soap to one end of the stick and
holding that in the water just back of the boat, you can apparently
repel a single boat. The soap weakens the surface film so that the
boat is pulled in the opposite direction by the film on the other
side of the boat. By using soap on one end to repel and the oppo-
site end to attract, you can make the boats maneuver in a manner
which appears mysterious to one who does not know the secret.
2. POND LIFE AQUARIUM
Procure several large glass jars. Have the club members divide
into several groups and visit different small pools and ponds on
a field trip. Bring back both plant and animal specimens. Ar-
range several aquariums and watch development in them.
3. PREPARE A SCRAPBOOK ON WATER
Classify the uses of water under : solid, liquid, and gaseous
form. Each member report upon the uses. A contest may be
arranged by dividing into three groups, the ice group, the water
group, and the steam group. An important use named wins a
point.
REFERENCE READING
Innes, W. T., The Modern Aquarium. Innes, 1931.
Meister, M., Water and Air. Scribners, 1930.
Thompson, J. M., Water Wonders Every Child Should Know. Grosset.
Whitman, W. G., Household Physics. Wiley, 1932.
•
SURVEY QUESTIONS
Does all fire produce heat and all
heat produce fire ?
What must be done to set a com-
bustible substance on fire ?
Why does a fire sometimes go out
by itself?
What is our greatest natural source
of heat?
Do you know how heat travels from
one place to another?
Do you know the scientific differ-
ence between heat and cold ?
What instrument measures temper-
ature and how does this instru-
ment work?
Galloway
UNIT V
HOW WE USE HEAT
PREVIEW
Have you ever thought how important a part heat plays
in your life? Ancient peoples, Babylonians, Aztecs, and
our American Indians, worshiped the sun because it gave
them heat and warmth in winter and provided for their
crops in summer. Probably fire has been more wor-
shiped than any other element in nature. The use of fire
must have been a great discovery to ancient people. No-
body knows how man first got it. The first fire may have
come from lightning striking a tree, it may have come from
a chance focusing of the sun's rays through a rounded
quartz pebble, it may have come from an eruption of hot
lava from a volcano, it may even have come as the boy
The artist has shown some primitive people worshiping fire. What do you know
about fire worshipers ? From a mural in the Library of Congress.
103
104
HOW WE USE HEAT
Wright Pierce
Is this girl scout going to make a fire correctly? Could you do better? If so,
how would you go to work ?
scouts make it today, from friction by means of rubbing
things together, or it may have come from a chance strik-
ing of two hard stones so as to make a spark. But with
it came comfort. Think of what home would be without
any heating apparatus, or without fire to cook with.
Think of the fun you have popping corn or making candy,
or getting warm around a bonfire. Think of how heat
is used in melting substances such as solder, and how it
can be used for casting lead toys. These are only a few
of the cases in which we use heat. Our uses of heat
depend upon our ability to control it. To control it we
must learn how it acts. Heat can make things larger,
can make gases from liquids and solids, and can change
the flavor of foods. Heat can be transported by water
or steam from a furnace in the cellar to our rooms, where
HOW IS HEAT PRODUCED?
105
it gives us warmth and comfort. It means warm rooms
in winter ; it makes possible the cooking of raw foods ; it
gives us hot water, hot air, and hot foods. Today fire
has come to be used in hundreds of ways that the ancients
never dreamed of.
PROBLEM I. HOW IS HEAT PRODUCED?
If you are a boy or girl scout, you know how to build a
fire. First you get some paper or dry leaves, cover with
some shavings or thin kindlings, and then place larger
sticks at an angle over the other materials so as to make
a good circulation of air. When the fire has started, you
fan it or blow on it to keep it burning. Evidently a fire
must have something that will burn, a good supply of
air which contains oxygen, and enough heat to warm the
material to what is called its kindling temperature.
Demonstration 1. Kindling Temperatures.
Break off and discard the heads of two matches, place the sticks
on an asbestos mat. Two inches away from them put a piece of
sulphur or brimstone the size of a grain of rice. Melt about
20 grams of lead in an iron spoon supported on a stand as shown
in the diagram. Do not use
more heat than is needed
just barely to melt the lead.
When the lead melts, pour
half of it on the asbestos so
that it touches the sulphur,
and pour the rest of it so that
it covers the end of the sticks.
Does either substance take
fire? Remelt the lead in the
spoon. When it is just melted,
turn the gas under it low and
stick the end of a match stem
into the lead. Does it take
fire ? Rub the end of one of the sticks in the sulphur so that some
of it clings to the stick, and touch it to the lead. Look closely,
for sulphur burns with a pale blue flame. Which has the lower
kindling point, the sulphur or the wood ?
106 HOW WE USE HEAT
Kindling Temperature. This shows that different sub-
stances take fire at different intensities of heat. The
intensity or degree of heat is called temperature. In
making matches, the match head contains a compound
of phosphorus which ignites at a very low temperature,
and a compound that gives off oxygen easily, also pow-
dered glass or sand, and glue. By rubbing the match head
against a rough surface, enough heat is developed to ignite
the phosphorus. In the safety match, the head is made of
a substance which burns at a low temperature, while red
phosphorus mixed with sand or powdered glass is placed
on the box to give it a rubbing surface. The head of the
match will not ignite unless it is helped by the phosphorus
on the box.
What Causes Fire ? Many substances like phosphorus,
sulphur, and wood when heated to their respective kindling
temperatures in the presence of air or oxygen will burn
and produce fire. Such materials if burned to give useful
heat are called fuels. As we shall see later, gas, coal, oil,
and wood are fuels. When
fuels burn, heat is produced
by oxidation. In order to
keep a fire burning, we must
have oxygen and keep the
temperature at or above the
kindling temperature. You
can easily show the effect of
cooling below the kindling temperature. Copper is a
good conductor of heat. Wind a piece of copper wire into
a spiral coil ^ of an inch in height, making it large enough
to slip easily over the wick of a candle. Light the candle
and bring the cold wire down on the wick, the light will
go out. But if you light the candle again, then heat the
copper coil to red heat and bring it down over the wick,
the candle will continue to burn. This shows us that to
HOW IS HEAT PRODUCED?
107
Explain how the candle was lighted by the flint
and steel method.
keep a fire burning we must not cool it too much. Heat
is transferred to the cold copper wire. This transfer of
heat from one place to another and from one body to
another will be discussed in our next problem.
The Use of Tinder in Colonial Days. In colonial
days they caught sparks in tinder and produced fire in a
much more uncertain way than we do with our modern
matches. If you wish
to make tinder, get
some white cloth -
old sheeting or worn
handkerchief; cut sev-
eral pieces about five
inches square. Hold
each one separately
with a wire or tongs
and set on fire. As
the flame begins to die down, lay the charred cloth
upon a smooth flat piece of tin or other metal and
quickly cover with another metal. This cools and pre-
vents the tinder from burning up. Lay two sheets of
tinder upon some tissue paper and strike a rough edge
of hard rock, such as flint or granite, against the sharp
edge of the rod of steel so that sparks will fall upon the
tinder. When a spark has ignited the tinder, gather up
the paper and fold up about the sides to make a ball
with a small opening, blow gently to increase the burning,
and when it smokes strongly, blow harder. If the paper
then bursts into flame, you will have had the experience
of making fire by a method that was common a little over
a hundred years ago. Our forefathers tried to keep a fire
but would sometimes go to the neighbors to " borrow" live
coals when their fire was all out. They kept tinder on
hand so that in case of emergency they could produce
fire by the " flint and steel" method, which is the method
108 HOW WE USE HEAT
just described. But even the'flint and steel was a big ad-
vance over the many centuries-old friction method with
the bow and drill. Your great-grandparents doubtless
thought of the wonderful way they had of making fire
compared to the people of early times, just as you now
think of the match as a wonderful device when compared
to the flint and steel of former days. Friction with a
match makes fire in a fraction of a second, but friction
with the bow and drill under the best of conditions re-
quired minutes to make fire.
SELF-TESTING EXERCISE
Select from the following list those words which best fit the blank spaces
in the sentences below. Arrange the words in proper numerical order.
A word may be used more than once.
kindling go fire same
temperature temperatures stops burns
helps burn out better
different combustible match incombustible
below lower higher friction
same chemical action fuel
physical air (oxygen) stoves goes
Fanning the kindlings placed on the glowing coals in a fireplace
makes the fire (1) (2) Fanning a candle flame makes
the fire (3) (4) In the first case there is much heat ;
fanning brings in more (5) and so (6) the burning. In
the second case there is little heat; fanning brings in so much
air that the (7) is reduced (8) the (9) temperature
and so (10) the burning. There can be no burning or com-
bustion unless a (11) substance is heated to its (12)
(13) and supplied with (14) A common useful article
making use of a combination of substances with different kindling
temperatures is the (15) In early days of fire making
(16) generated the heat. Today we have many devices using
friction, but our ability to get fire so easily lies in the use of
materials with (17) kindling (18) Sulphur takes (19)
at a (20) temperature than wood.
WHAT ARE THE CHARACTERISTICS OF HEAT? 109
STORY TEST
DOES JANE KNOW How TO PRODUCE HEAT?
Read carefully and critically. List all the errors and suggest corrections.
This is the way I learned to start a fire when I was a scout:
Get a lot of dry leaves and lay them on some sticks of dry wood.
If you have paper with you, crumple it and use it with the leaves.
Lay large logs loosely over the mass o£ burning leaves. Substances
with a low kindling point like phosphorus will take fire at such a
low temperature that it is unsafe to hold them with the bare fingers.
You can set fire to a thin shaving of pine easier than you can to
a dry pine log because the shaving has a lower kindling temperature.
A cold metal may extinguish a candle flame because it radiates
heat so fast it cools the candle wax below its kindling point. In
lighting a match, the first energy used is chemical, then heat and
finally light result. There are only three changes of energy
involved.
PROBLEM II. WHAT ARE SOME OF THE
CHARACTERISTICS OF HEAT?
When we have a bonfire, we see that fresh air comes in
to the fire, while smoke and gases rise from the fire. Such
currents of air are called convection
currents.
cold- -Vater-
Demonstration 2. Convection.
Fill a battery jar with cold water. Fill a small
bottle with hot water colored with red ink ; place
in it a perforated cork containing two tubes, as
shown in the diagram. Lower the small bottle
of hot water to the bottom of the jar of water.
What happens? Put in your workbook a dia-
gram showing the movement of the water.
The movement of the liquid shown in this experiment
is called convection. We thus see that convection takes
place in liquids, and a bonfire shows that it takes place
in gases. Since rising air or water is hot, heat is carried
by it. What makes the heated water rise? This rise is
caused by the fact that warm water is lighter than cold
110 HOW WE USE HEAT
water. Gravity therefore pulls with greater force on a
given volume of cold water than it does on the same vol-
ume of warm water. Because of this greater pull, the cold
liquid is drawn under the lighter one and pushes it up,
thus causing a convection current. A similar explana-
tion accounts for convection in gases.
Demonstration 3. To See if Peat Will Travel Along a Metal Rod.
Take a metal rod ; attach it to a stand, as shown in the diagram.
Tie threads to each of six tacks. Attach to the rod each of the
threads about two inches apart
by means of melted wax. Now
apply heat to the end of the
rod. What happens?
/!/
tacks 4
fastenecC
Conduction. This dem-
-i ^ onstration shows that heat
travels from one end of the
rod to the other. The flame
•\viU2 "\vax. heats the tiny molecules of
iron, causing them to vi-
brate or move faster. They
hit neighboring molecules
harder blows and thus cause
them to move. In this way, from molecule to molecule,
heat travels by conduction. Most metals are very good
conductors of heat. Substances like glass, water, and
many rocks are fair conductors ; while air, paper, linen,
silk, and wool carry heat so poorly that they are called
nonconductors. ' Poor conductors of heat are sometimes
called heat insulators. Metals are the best and gases the
poorest conductors of heat.
Radiation. The sun is 93,000,000 miles away from us,
and we know there is very little matter in all of this space.
Yet heat comes from the sun to us. This method of heat
transfer is known as radiation. Experiments show that
rough, black, dull substances absorb heat better than
WHAT ARE THE CHARACTERISTICS OF HEAT? Ill
smooth, light, or shiny substances. Substances which
absorb heat give it up easily by radiation.
Demonstration 4. Heat Causes Expansion.
Gas. A glass flask filled with air having a balloon attached to
one end is heated. What happens to the balloon? Let the flask
cool. Result?
Liquid. Fill a 500 cc. flask full of colored water. Place a
stopper carrying a long glass tube so that the colored water rises
in the tube. Mark the level of the water carefully on the tube.
Now warm the flask by placing in a dish of hot water. What
happens ? Remove from the hot water and allow the flask to cool.
Result?
Solid. Support a copper rod or tube two or three feet long on
a block, as shown in the illustration. End A is not movable;
TO*
-move burner-
back Q*ul
end B can roll over a wire bent so the end hangs vertically in front
of the block. Hang a weight near B to hold the rod firmly upon
the wire. Heat the rod by moving the gas flame back and forth
along the rod. Watch the position of the wire pointer. Explain
result. Let the rod cool. Explain the observed result.
112 HOW WE USE HEAT
This demonstration shows very clearly that heat causes expan-
sion. Contraction of substances is brought about when heat is
withdrawn from them. On a hot day a metal drawbridge after
being opened refused to come together again. Why? The draw-
bridge tender squirted a stream of cold water upon the bridge and
it went back into place. Why?
How Temperature Is Measured. We have seen that
heat makes things warmer, and the higher the tempera-
ture of a body, the more heat it contains. But heat and
temperature are not the same thing. Temperature
is the intensity of heat and is measured in units called
degrees. This measurement makes use of the principle
that matter when heated expands, and when cooled
contracts. The thermometer is made of a glass tube
having a very fine bore. A bulb at one end of the tube
is filled with mercury or colored alcohol. Since heat
makes the liquid expand, it will rise in the small bore in
the tube as it gets warm and thus indicates the degree of
heat which is marked on the scale.
Thermometer Scales. There are two thermometer
scales, the Fahrenheit marked F., used by the weather
bureaus and in everyday life, and the Centigrade marked
C., used in scientific work and most foreign countries.
The freezing point of water is 32° on the Fahrenheit scale
and zero on the Centigrade, while the boiling point of
water at sea level is 212° on the Fahrenheit scale and
100° on the Centigrade.
Heat Causes Changes in the State of Matter. Another
thing that heat does is to change the form of different
substances. The quantity of heat energy possessed by
the molecules of water determines whether water is in the
solid, liquid, or gaseous state. The molecules in ice have
the least energy. Since heat is taken from warmer objects
to change ice to water, ice is used in our refrigerators.
Molecules of liquid water have more energy than molecules
WHAT ARE THE CHARACTERISTICS OF HEAT? 113
8o1
7o°
<5C>
50*
30°
do"
-10°
-17.751
2oo° °f water
1 180°
170' '
160°
1150°
140°
130*
120°
.110°
|-l°.0lT7ormal
90°
[So'
of ice. A tub of water on
a cold night gives up heat
to the air. Fruits and
vegetables do not freeze
until the temperature is
as low as 28° F. ; and
so tubs of water placed
in farmers' cellars have
many times kept fruits
and vegetables from freez-
ing. In changing water
to steam at 212° F. a large
amount of heat is stored
in the molecules of steam.
This energy may be used
in cooking, in heating,
and in the production
of mechanical energy by
means of the steam en-
gine. When steam con-
denses to a liquid, all
this stored heat is given
off. That is why a burn
by steam is so much
worse than a burn by
boiling water. Both are
the same temperature,
but the steam has more
heat in it.
Freezing and Boiling Temperatures. Water freezes
and ice melts at 32° F. It seems strange at first to
think of water and
ice at the same
temperature. But
How are clinical thermometers used ? when just enough
H. & w. sci. i — 9
room
temperature
poiTZ.1,
of water
I lo°
0°
If butter melts at 93° F. it will melt at what
temperature Centigrade ?
114
HOW WE USE HEAT
In how many ways is heat energy used in the kitchen ?
heat is added to ice at 32° to melt it, the resulting water
also is at 32° F. There is no change in temperature when
ice melts or when water freezes. Water boils and steam
condenses at sea level at 212° F. During this change of
state there is no change in tem-
perature.
Demonstration 5. Boiling Water.
1. Constant Temperature of Steam
and Boiling Water in Open Vessel.
Heat water in a flask. Have two
thermometers, one placed so that the
bulb is in water and the other so
that it will be in the steam above
the water. After the water is boil-
ing, read the thermometers at inter-
vals of one minute for five minutes.
Tabulate your results. What are your conclusions?
2. Boiling Water at Reduced Pressure. A ring-neck, heavy-
walled, round-bottom flask is filled half full of water. Boil the
WHAT ARE THE CHARACTERISTICS OF HEAT? 115
water until the air has been driven out. Remove the heat. Close
the flask with a stopper holding a thermometer. As the steam
condenses, the pressure on the water is reduced. After the bubbling
has stopped, condense more steam by placing a cold wet cloth or ice
around the upper half of the flask. Does the water boil again?
At what temperature did you boil water? After the temperature
gets below 90° C. or 190° F. and there is no boiling, place the heat
under the flask for a moment. Result?
Why Pressure Cookers Are Useful. At sea level water
under average atmospheric pressure boils at 212° F.
Both water and steam have the same temperature.
People who live on .
high mountains find
that water boils be-
fore it reaches 212° F.
This is because the
pressure of the air is
less and the boiling
point of water de-
pends upon the pres-
sure on its surface.
On some high moun-
tains boiling water is
not hot enough to
cook vegetables, so
they must use some
other method or in-
close the water in a
vessel to prevent the
escape of steam. The
increased pressure
raises the boiling point
and makes cooking possible. In the pressure cooker where
steam is not allowed to escape, the pressure increases and
the temperature rises with the rise in pressure. This ac-
counts for the more rapid and thorough cooking of foods
Wright Pierce
In what ways is a pressure cooker useful?
Why would it be useful at high altitudes ? What
scientific principle underlies this value?
116 HOW WE USE HEAT
cooked in such vessels. Pressure cookers are commonly
used in high altitudes, but are also used advantageously
at low levels chiefly to save time in cooking, to save fuel,
and to make tough cuts of meat more tender.
SELF-TESTING EXERCISE
Select from the following list those words which best Jill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
matter state heat hot
cold temperature under thermometer
pushes particle increases contract
larger weight decreases change
conduction force expand substance
more conductors radiation reduction
Gravity pulls on one cubic inch of cold water with (1) force
than it does on one cubic inch of (2) water. As a result, the
(3) water flows in (4) the (5) water and (6) it
upward. Heat is transferred from particle to (7) in (&)
by a process called (9) Metals are better (10) of heat
than clothing. (11) is not always required to carry heat;
in the transfer by (12) heat can pass through empty space.
When most substances are heated, they become (13) or wo
say they (14) The measurement of (15) by means of a
(16) takes advantage of the (17) in size of bodies when
heated to a higher temperature and of its (18) in size when
it is cooled. Many substances like ice and lead, when heated, may
(19) their (20) and become liquids.
STORY TEST
FRED Is AT THE MICROPHONE TODAY TELLING
"WHAT HEAT CAN Do"
Read carefully and critically. List all the errors and suggest correc-
tions.
Fellow science students : From my study of heat I have come to
the conclusion that heat is a sort of circus trickster. He can get
aboard the molecules of air coming from the throat of a trumpeting
THE HEAT OF THE BODY 117
elephant and rise to the top of the big tent with no apparent support
in a process called conduction. He also can walk a tight wire.
You recall how when you hold one end of a metal in the flame, heat
comes over and tells you to let go. This method of travel is called
radiation. Heat is an austere master; when he gets inside a vessel
of water and cracks his whip the molecules of water cower and
crowd together making the volume smaller. Heat is a fickle
fellow and changes partners often. Believe it or not, he likes ice
cream. I was called away from dinner last night when half
through my ice cream dessert and when I came back just a pasty
liquid was left. Why? Because heat had left the air and gone
into the ice cream. They call this a change of state but I call it
meddling. There is an instrument called the barometer which is
used to tell how hot or cold a body is. I had one under my tongue
once. Heat went into it from me and made me feel a lot cooler.
PROBLEM III. HOW DOES CLOTHING AFFECT
THE HEAT OF THE BODY?
What Keeps the Body Warm? We have already
learned that the heat of the body is caused by the oxida-
tion of food which we eat. The circulation of the blood
assists in keeping all parts of the body at about the same
temperature. But we know that on a cold day the out-
side of the body gets cold. We use clothes, bedclothes,
hot-water bottles, or electric pads to keep warm. Evi-
dently clothes should be worn not only for their good
looks but for their practical value. In hot climates
little clothing is needed, while in very cold parts of the
world furs and skins act as insulating materials against
the cold. In a temperate climate where changes are
frequent clothing ought to be adjusted to fit the tem-
perature.
What Materials Are Used in Clothing? We know that
most of our clothing comes from five sources. Outside
of leather and rubber, our clothing is made from fibers of
wool, cotton, flax, silk, and rayon. Wool and silk are
of animal origin ; cotton and linen (from flax) are of
HOW WE USE HEAT
Two extremes in clothing. Give scientific reasons for the two conditions in
clothing shown here.
vegetable origin. Rayon is a chemical product made
from vegetable matter such as wood pulp and low-grade
cotton.
Demonstration 6. Fibers and Tests for Fibers.
Physical Appearance of Fibers. Examine under the microscope,
slides of wool, cotton, flax, silk, and rayon. Wool fibers have
little scales projecting from the surface. Cotton fibers look twisted.
Flax fibers are never twisted, vary in size, and have small transverse
markings. Silk fibers have no markings, are smaller in diameter
than flax. Rayon fibers are smooth like silk but much longer.
Place in your workbook sketch drawings showing the appearance
of the different fibers.
Absorption-of-Water Test. Place small equal-sized samples of
cloth made of the different fibers in saucers containing equal
amounts of water. Which absorbs the most water? Which the
least?
Chemical Test. Boil each of the five different kinds of cloth in
a lye solution (5 per cent sodium hydroxide). Wash carefully in
THE HEAT OF THE BODY
119
water before handling. Test the strength of each cloth. Which
cloth holds together the best?
Burning Test. Using the five kinds of cloth, light each piece
separately. Notice the odor and rapidity of burning. Repeat
the test, holding strip
of moist blue litmus
paper in the smoke
given off by the cloth.
What happens? Do
the same with moist
red litmus paper. What
happens? Sum up all
your observations in
your workbook.
\\ool fibers
Cottoia fibers
flax fibers
silk fibers-
What These Ex-
periments Show.
Wool fiber because of
its scales gives gar-
ments their rough
texture. When such
fibers shrink, as they
may when passing
from hot to cold
water or to water
containing such a substance as lye, the scales cause the
fibers to stick close together. Wool undergarments ab-
sorb moisture and allow it to evaporate slowly. This
prevents rapid loss of body heat. Cotton underwear
leaves an excess of moisture on the skin and the mois-
ture may evaporate rapidly, thus chilling the body. The
twist in the cotton fibers serves the same purpose as the
scales on the wool : it gives spring and elasticity to
the material. Cotton fabrics are harder than wool, and
there are fewer air spaces in cotton materials than in wool,
hence cotton garments permit heat to escape more rapidly
from the body. Linen fibers have little elasticity and
hence the fabrics manufactured from them do not shape
120 HOW WE USE HEAT
themselves to the body. Linen can be washed in hot
water without injury, but it is costly and so is not used
as much as cotton. Silk both absorbs and loses water
rapidly, but it is expensive and hard to wash. Rayon
which is made largely from wood pulp is used extensively
for underwear. It absorbs water readily and loses it
rapidly, and consequently makes good undergarments.
Clothing for Winter and Summer. The human body is
a self-regulating machine in which the body temperature is
normally kept at 98.6° F. Underneath the skin is a fine
network of blood vessels from which heat is passed off
through perspiration. When we do hard work, the blood
becomes heated and circulates more rapidly. The blood
vessels of the skin get larger, and give heat off to the sweat
glands, which pour out perspiration. This in turn evapo-
rates, cooling the skin, and this cools the blood ; thus our
temperature is kept constant. Evidently, then, in winter
we need underclothes which will not let heat out. Under-
clothes which do not hold moisture are best because wet,
sticky undergarments cool us by conduction if it is cold,
and keep us uncomfortably hot by preventing evapora-
tion if it is warm. It does not make very much differ-
ence what kind of materials are used, provided the under-
clothes are porous. Woolen underclothes are best for
winter, because the curly fibers make them porous, and
because they absorb moisture and give it up slowly, thus
preventing the skin from being cooled too rapidly. We
have seen that dark substances absorb heat and light-
colored substances reflect heat ; therefore, to wear dark
clothes in winter and light clothes in summer is scien-
tifically correct as well as more comfortable. If you take
two test tubes, place a thermometer in each tube, then wrap
a piece of white cloth around one and a piece of dark cloth
of the same weave around the other, leave both tubes in
the sun side by side for a few minutes, and then read the
THE HEAT OF THE BODY
121
.-thermometer
temperatures, you will find that the tube surrounded by
the dark cloth shows a higher temperature than the other
tube. Evidently ab-
sorption of radiant en-
ergy has been the cause
of this difference in
temperature. In the
winter we wish to put
a nonconductor be-
tween the body and
the outside cold air.
For this reason fur
coats and other dense
materials are used.
We sometimes place
a newspaper over our
chest when going into
a cold wind. Can you
explain Scientifically In which tabe ^ the thermometer register
the reasons for this? higher? why?
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
reduces
98.6
loss
silk
scales
76.4
warmth
heat
wool
shrink
rayon
air
rubber
nodes
light
fibers
absorbs
elasticity
dark
stretch
cold
replaced
heats
smoothness
evaporates
silky
hot
wool
of
In cold regions clothing is very useful to prevent (1)_
(2) from the body. Of the animal fibers (3) and (4) ,
(5) is the more common while (6) make more beautiful
fabrics. In recent years (7) has to a large extent (8)
silk because of its low cost. The rough texture of wool is due to
HOW WE USE HEAT
(9) which when a garment is rubbed, especially in hot water,
cling together, causing the garment to (10) Much of the
warmth of any garment is due to the (11) held within the
meshes of the cloth. The normal temperature of the body is
(12) F. Evaporation of water from the surface of the body
(13) the temperature. In winter (14) colored clothing is
warmer than (15) colored clothing because it (16) more
heat.
STORY TEST
ELISE GIVES Us SOME IMPORTANT FACTS ABOUT CLOTHING
Read carefully and critically. List all the errors and suggest corrections.
Ever since it was found that fibers could be spun into thread
and then woven into cloth, man has had many different kinds of
materials from which he can make his clothes. Whether it is the
silky rayon made by the silk worm or the linen fibers taken from
the seed of plants, it is possible to weave it into many pretty pat-
terns. You can tell true rayon from animal silk because it burns
with odor of burning feathers and shows nodes along a smooth rod
when viewed under a microscope. Cotton can be told from wool
because it burns faster and dissolves in alkali. Yesterday I had a
temperature of 94.7° F. and Mother kept me in saying I had a fever
because the normal temperature is 89.6° F. When we work hard,
we increase the body heat and perspiration. Evaporation of the
perspiration is a cooling process and so helps to keep the body
temperature down to normal. We should choose clothing which
checks evaporation in winter and aids it in summer.
THE REVIEW SUMMARY
In preparing a summary of what you have learned in this unit,
you will want to place emphasis on the big ideas which have come
out of the applications of the facts you have learned and the
demonstrations you have seen. In this unit look carefully for
other generalizations than those which follow :
1. Heat is present to some degree in all matter.
2. Our greatest source of natural heat is the sun.
3. Heat is produced from other forms of energy.
4. Heat can be transferred through matter or by radiation.
5. Heat causes many changes in matter.
6. Heat is essential to the human body.
THE HEAT OF THE BODY 123
Before making your review summary, test your knowledge of
the facts of the unit by checking over the text so as to be sure to
know the facts underlying the generalizations. Then, using the
generalizations, the material in the text, and everything you have
read, seen, or done yourself, make a summary outline for your
notebook. This outline you may use when you make a recitation.
TEST ON FUNDAMENTAL CONCEPTS
Make two vertical columns in your workbook. Head one CORRECT and
the other INCORRECT. Under the first place the numbers of all the state-
ments you believe to be correct. Under the second place all the numbers
you believe to be incorrect. Your grade = right answers X 2.
I. Before we can start a fire we must have : (1) heat ; (2) nitro-
gen ; (3) oxygen ; (4) an incombustible substance ; (5) inflam-
mable material.
II. Heat travels from : (6) the sun to the earth by conduction;
(7) a flat iron to clothes being ironed by conduction ; (8) hot coals
to a kettle above by radiation ; (9) a soldering iron to the solder
by convection ; (10) a fireplace to objects in the room by conduction.
III. When heat is applied to water, it may change its : (11) tem-
perature; (12) state to a solid; (13) size; (14) weight; (15) com-
position.
IV. The temperature of boiling water is: (16) 32° F. at sea
level; (17) less on tall mountains than at sea level; (18) greater
in a partial vacuum; (19) never over 212° F. in a pressure cooker ;
(20) always the same 98.6° F.
V. There is a change in temperature when: (21) water cools;
(22) water at 32° F. changes to water at the boiling point;
(23) steam at the boiling point condenses ; (24) ice melts ; (25) a
hot iron is put into cold water.
VI. The principle of heat insulation is used when we use :
(26) storm windows; (27) the pressure cooker; (28) hot-water
bottle ; (29) asbestos mats on the table ; (30) copper for hot-water
pipes.
VII. Wool fiber: (31) is a fine, flattened, and twisted fiber;
(32) will dissolve in a 5 per cent sodium hydroxide solution ; (33) ab-
sorbs water more freely than cotton; (34) conducts heat well;
(35) burns faster than linen.
VIII. Cotton fiber : (36) gives the odor of burning feathers
when burned ; (37) will dissolve in a 5 per cent sodium hydroxide
solution ; (38) is a thick, lustrous fiber ; (39) has the same chemical
composition as the material from which rayon is made; (40) is
a vegetable fiber.
124 HOW WE USE HEAT
IX. Silk fiber: (41) is of animal origin; (42) has a more
brilliant luster than any other fiber except rayon; (43) has little
scales projecting from its surfaces; (44) is composed of cellulose;
(45) is stronger than artificial silk when both are wet.
X. In washing woolens it is well to use : (46) boiling water ;
(47) soap containing free alkali ; (48) little soap but much washing
soda; (49) water below boiling point; (50) a small amount of
bleaching powder.
THOUGHT QUESTIONS
1. Make a list of materials which have a low kindling temper-
ature; a high kindling temperature. Which of these would be
best to build a fire with?
2. Find ten ways in which heat insulators are used in your home.
3. Why is the outside of a teakettle kept bright and smooth
while the bottom is dull, black, and rough?
4. Why does a bicycle tire register greater pressure on a hot
day than on a cold day?
5. Why is it when you fill the radiator of your car full to the
brim on a cold day that it begins to run over shortly after you start
the car?
6. You are going to Duluth for your Christmas vacation.
What clothes would you take with you, and why?
7. You are driving from New York City to Florida in March.
What clothes would you wear on the trip? Give your reasons.
REPORTS ON THINGS I HAVE READ,
DONE, OR SEEN
1. Report upon an article related to some topic discussed in
this unit. The article may be from a current number of a science
magazine or from some popular science book you have read.
2. Everyday activities involving expansion.
3. An account of the work of Bunsen or of Fahrenheit which
is related to heat.
4. Uses of heat insulators.
5. How man's activities and habits vary at different latitudes
on the earth.
SCIENCE RECREATION
1. Pressure of ice. Fill a small bottle with water. Put a
cork in tightly. Be sure there is no air space left inside. Put
this either in the ice-cube pan and put into the cooling coil of the
refrigerator, or place it outdoors on a day when the temperature
THE HEAT OF THE BODY
125
is under 25° F., or pack it in a mixture of crushed ice and coarse salt.
Examine after two hours. Account for the result.
2. Cast lead weights. Make exactly 1 oz., 2 oz. to use on a
letter scale. Cast lead toys.
3. Make a study of heat-conducting materials used in your
home and write a report upon them.
4. Make a study of heat-insulating materials used in your home
and write a report upon them.
SCIENCE CLUB ACTIVITIES
1. THE FORCE OF STEAM
Put a cupful of hot water into a half-liter flask. Stretch the
open neck of a rubber balloon over the opening of the flask. Fasten
the flask to ringstand with a clamp. Boil the water, being very
careful not to allow the flame to come near any part of the rubber
balloon. Continue the heating until the steam escapes into the
room. Have the club members stand
several feet away until the climax is over.
2. BOIL WATER IN A PIECE OF PAPER ^ hot Voter
Get a piece of stout paper of medium
thickness about 5" or 6" square. Fold
this to make a conical cup. Have the
fold come inside the dish so that outside
there is only one thickness of paper be-
tween the water inside and the flame
outside. Place the cup in a ring on the
ringstand. Trim off the paper that is
more than -J-" above the top of the iron
ring when the cup is filled with water.
Put hot water in the cup to start with, and place a low flame under
the cup. Heat until you see the water boil.
REFERENCE READING
Carpenter, F. G., and Carpenter, F., The Clothes We Wear. American
Book Company, 1926.
Collins, A. F., Experimental Science. Appleton, 1929.
Collins, A. F., The Boys' Book of Experiments. Crowell, 1927.
Tower, S. F., and Lunt, J. R., The Science of Common Things. Heath,
1922. A study of fire, page 146.
Whitman, W. G., Household Physics. Wiley, 1932. Heat, pages 24-
30; Thermometers, pages 55-65; Pressure Cooker, pages 105-114.
SURVEY QUESTIONS
What makes it possible for you to
see some objects in the room ?
Do you know why you cannot see
the air?
If it were not for mirrors, how could
you tell how you looked?
Do you know where the sky, the
moon, and the electric lamp get
their light?
Why is good light needed in taking
pictures ?
What causes a rainbow ?
Can you define color and tell what
causes it ?
Why are not all the lenses in eye-
glasses alike ?
Publishers' Photo Service
UNIT VI
HOW WE USE LIGHT
PREVIEW
Have you ever awakened from sleep on a dark night to
find yourself in utter darkness? How glad you were to
have an electric light close at hand! What a sense of
helplessness we get when we are without any light ! We
certainly enjoy light, for it gives us so much : our ability
to see views and pictures, to read, to see wonderful sun-
sets, the colors of birds and flowers, or the gray vastness
of the desert. It gives us our food, for we know green
plants depend upon it.
Sir Isaac Newton, a great English scientist of the seven-
teenth century, believed that light consisted of very small
particles given off at great speed by all luminous bodies.
He thought that when these particles struck the eye, they
produced the sensation of light. This theory was accepted
by scientists for over a hundred years, and then discarded
in favor of a theory suggested by a Dutch physicist,
Huygens.1 This theory stated that all luminous bodies
caused the ether, which was supposed to fill all space, to
vibrate. When these vibrations reach the eye, they give
the sensation of light. Recently a new discovery by a
German and an Indian professor give other ideas. This
is the so-called Quantum theory which is based on the
belief that light proceeds in little gusts or packets of energy
instead of continuous waves. Still another theory goes
back to that of Newton and says that light travels in the
1 Christian Huygens (hl'genz), Dutch astronomer and physicist, 1629-
1695.
127
SIR
Bausch & Lonib Optical Co.
ISAAC NEWTON, 1642 1727.
IVTEWTON must have been a clever boy, for although he did not do
*• ^ well in school he was very ingenious. He made a clock which
ran by water, a sun dial, and a windmill which actually ground corn.
At the university he specialized in mathematics and science and
soon showed his genius. He improved methods of calculation in
mathematics and applied them in physics; he invented the reflect-
ing'telescope; he made navigation safer by making certain the
positions of the heavenly bodies; and he proved the pull of gravity
was a universal law.
Newton's experiments with a glass prism and a beam of sunlight
were the beginnings of spectrum analysis, which is now a useful
tool of the scientist. The spectroscope, making use of the prism
principles, is particularly useful to the astronomer.
After over 40 years of service in Cambridge University he died,
one of the most honored men of his time.
HOW DO I USE LIGHT?
form of tiny balls, each of which is spinning very rapidly
in space. In this book we will agree with the theory that
light is a form of radiant energy and that it passes through
space by means of very rapid vibrations. Light travels at
the astonishing rate of over 186,000 miles a second. When
a candle is lighted, there are changes in the material of
which it is made, which produces light energy. This radi-
ates through space in all directions. Heat is also radiated
from hot bodies, and the disturbances in the aerial of a
broadcasting station send out electrical radiations. Evi-
dently, then, light, heat, and electricity may travel as
forms of radiant energy. It will be the purpose of this
unit to learn something about the ways in which light is
used in our everyday life.
PROBLEM I. HOW DO I USE LIGHT?
If you were ever up to see the sunrise, you know that as
daylight approaches, objects begin to change from hazy
gray outlines and become more and more distinct as light
falls on them, till, in the early sunlight, they appear in all
the colors of nature. We have just read that light is a
form of radiant energy. We know that light is frequently
associated with heat, and that plants in the garden get
heat energy as well as light energy from the sun. Recent
discoveries have shown that we, ourselves, are getting
good out of the light that a few years ago we had no idea
of. The ultra-violet ray in the sunlight aids us to keep
well and prevents certain diseases, while the hardness of
our bones and our freedom from certain diseases is due to
its effect. We know that light makes it possible to read,
to see things in their natural colors, as well as to take pic-
tures and make light signals. From times of earliest
civilization people used light for signaling. The Greeks
and Romans as well as our American Indians all had
elaborate light signals, just as we are warned today by our
H. & W. SCI. I — 10
130
HOW WE USE LIGHT
I
lighthouses, airplane beacons, and the more common
traffic lights. Heliograph signals, made by reflecting a
beam of sunlight on
a mirror, have been
sent nearly 200 miles.
Light-Using De-
vices. Let us think
over the things we
\\ I ~^--,
may find at home
whose use depends
upon light. There is
the camera, the opera-
glass, the reading
glass, and, of course,
the mirror and win-
By fanning dows. Perhaps there
is a magnifying glass,
an enlarging mirror, or a bull's-eye flash lamp. Among
the toys there might be a kaleidoscope and possibly a
stereoscope. If there is a nature lover in the family,
you may find bird glasses or field glasses.
How an Image Is Made by a Pinhole. If you let a
small beam of light enter a dark room in which there is
The Indians used smoke signals.
the fire puffs of smoke were given off.
dusty air, you can see that the light travels in a straight
line. If a small hole is made in the window shutter on
the first floor of a building and the room is dark, people
HOW DO I USE LIGHT?
131
who walk by the window outside will reflect rays of light
so that images of them appear on the wall opposite the
window. A curious thing about the image is that it is
upside down. If we make a pinhole in one end of a small
fround
glass-
How many devices can you name that involve the principle shown here ?
box and have a shaded frosted glass in the opposite end,
we can see on the frosted glass an inverted image of a
bright object that is in front of the pinhole.
The diagram will help us to understand this. A is seen
by light that comes from A. The light that goes through
the pinhole will fall at A'. The light from B will reach the
frosted glass at B'. Light from all points between A and
B will fall somewhere between A' and B'. The image is
inverted because the rays which come from the object
cross where they pass through the pinhole. If the hole
were not very small and other light was not kept out,
there would be such overlapping of light from different
parts of the object that no clear image could be seen.
This principle of image formation is used in our eyes when-
ever we look at any object. There is one difference.
There is a lens at the opening of the eye. This allows
more light to come in and gives a brighter image. The
132
HOW WE USE LIGHT
Galloway
How many different kinds of stop lights have you seen ? It would be a good thing
to have these signals uniform for all parts of the country. Can you see why ?
image in the back of the eye excites the proper nerve end-
ings so that the brain can interpret the image and in this
way we see objects.
Colored Signal Lights. The engineer depends upon
colored lights to tell him if there is a clear track ahead.
Where other trains use the same track and where switches
may lead to branch tracks, a green light is a signal that
the track is clear and safe. A red light is the signal for
danger. On boats you see green lights on the starboard
or right side and red lights on the port or left side. If we
travel by train or water, our safety depends greatly upon
the watchfulness of the pilot or engineer and his care in
heeding signals. Our most common use of signal lights is
the traffic signal and automobile tail light. Here again
red is the danger sign and green the signal to pass. In
HOW DO I USE LIGHT? 133
many places the use of an orange light for pedestrians to
pass while auto traffic remains at rest is a very helpful
aid to safety. Our use of colored lights and following the
messages they bring to us make possible the rapid clearing
of traffic jams and greater freedom from accidents.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
radiation radiant orange
chemical mechanical red
electricity image blue
lights cross inverted
heat green object
colored straight light
Light is a form of (1) energy just as (2) and (3)
are. (4) is used whenever we read or see an object. Since
light travels in (5) lines, whenever light from an object passes
through a small opening, the rays (6) and produce an (7)
image. When (8) signal (9) are used, it is common to
use (10) for danger and (11) for safety.
STORY TEST
FLORENCE WRITES AN ESSAY ON LIGHT
Read carefully and critically. List all the errors and suggest cor-
rections.
There are two kinds of light, black and white. This has been
proven by pictures taken of lightning. Some streaks are black
and are produced by black lightning. We cannot see objects by
black light ; we use the white light. If a candle is behind a block
of wood, we cannot see it because light travels in straight lines.
If light radiates from a red hot iron, the light goes in all directions
and then may go around corners, in curved lines. If light rays
from two objects were to meet, they would destroy each other, and
where they come together, the two bodies would be invisible.
The reason automobiles have red headlights is because it is danger-
ous to be in front of a car. The green tail light indicates safety.
134
HOW WE USE LIGHT
c£i/fcr;Se
PROBLEM II. WHAT ARE SOME OF THE
PROPERTIES OF LIGHT?
What Happens When Light Meets a Body ? It is inter-
esting to play with a beam of light. In a dark room allow
a small beam of light
to pass across the
table from a lantern.
Make this beam visi-
ble by means of dust,
smoke, or ammonium
chloride fumes. Hold
a piece of window
glass at right angles
to the beam. You
can see the beam al-
most as brightly back
of the glass as in front.
This light that comes
through is transmitted
light. Tilt the glass
and you will see a
faint beam sent off
from the surface.
This is reflected light.
A still smaller part of
the beam is neither
transmitted nor re-
flected, but is absorbed
and changed to heat.
Three things happen
when a beam of light
/reflected
absorbed
cccrcCboccra
Explain why the frosted glass has a different
effect on the light than the window glass does.
What happens to most of the light that falls upon
a black body?
comes to a body that allows light to pass through, but
only two things happen when the body does not permit
the light to pass through. Can you tell what happens
to the light when it meets the latter body ?
WHAT ARE SOME OF THE PROPERTIES OF LIGHT? 135
Bodies Vary in Ability to Transmit Light. Have you
ever noticed how the " steaming7' of a window at home or
on the train changes your vision of objects on the other
side? If you wear glasses, perhaps you have noticed
that when you come into a warm, damp atmosphere
from the cold outdoors the moisture gathered upon your
glasses so that you could not see anything distinctly.
When you wiped off the moisture or it disappeared after
the glasses were warmed you could see clearly again.
Clear glass lets light go through without much change in
Explain the terms transparent, translucent, and opaque by reference to the
diagram.
direction. All bodies like glass, cellophane, quartz, air,
and water which permit light to pass through so that we
can see objects through them clearly are called transpar-
ent. Making the surface of glass rough causes a scatter-
ing of light that passes through. Frosted glass, con-
densed vapor on glass, oiled paper, and very thin paper,
gauze, or window shades may allow enough light to pass
through to show the presence of objects without their
being seen distinctly. These bodies are translucent.
Objects that cut off all light are called opaque.
A Shadow. If you darken a room and allow a beam of
light to enter, you will notice that it travels in a straight
136
HOW WE USE LIGHT
line, and that if you put an opaque object in front of
the source of light, it will cut off the light and pro-
duce a shadow. A shadow is that space from which
light is cut off. The dark outline we cast on the pave-
ment when we stand
near a street lamp we
often call a shadow.
But remember a shadow
is not just a dark sur-
face, it is all the dark-
ened space back of
the object which cuts
off the light. Were
this not so, we could
not enjoy the shade
(shadow) of a tree hav-
ing dense foliage on a
Where is the shadow? Is the word "shadow" bright hot day in the
put in the correct place in this cut ? 011™™^*.
o Ulillllcl .
Reflection of Light. Light, such as a candle flame, a
red hot iron, a burning match, or the stars may come to
our eyes direct from its source. Bodies which give off
light of their own are luminous bodies. Very few of the
objects we see in the course of the day are bodies that have
light of their own, but we cannot see any object unless
light comes from it into our eyes. All nonluminous
bodies which we see receive light from some other source
and reflect it. That which is reflected into our eyes makes
the object visible to us. Do you realize how important
reflection of light is ? Without it you could not read, see
pictures, nor recognize friends by sight. You could not
see the moon nor yourself in a mirror. Sunlight which
enters your room may be reflected from one surface to
another many times before it is reflected by the particular
object you may be looking at.
WHAT ARE SOME OF THE PROPERTIES OF LIGHT? 137
Demonstration 1. Law of Reflection.
Hold a plane mirror in a narrow beam of light in a dark room.
The light is bent or reflected from the mirror. We call the incom-
ing ray the incident ray and the outgoing ray the reflected ray. A
line at right angles to the sur-
face where the ray of light meets
it is called a normal. Hold a
ruler at right angles to the
mirror at the point where the
beam strikes the mirror, com-
pare the angle between the ruler
and the beam coming to the
mirror (angle of incidence) and
the angle between the ruler and
the beam going from the mirror (angle of reflection). Turn the
mirror slightly to change the angles. Compare the angles as
before. What do you notice with reference to the angle of in-
cidence and the angle of reflection? When light is reflected from
a plane surface, how does the size of the angle of reflection com-
pare with the size of the angle of incidence?
How We See in a Mirror. When you look into a mirror,
the image appears to be behind it. If you step close to
the mirror, the image comes close ; if you step away, the
image goes away. If you examine the diagram, you will
see that light goes to the eye in the direction it would if
the object were really where the image is, but in reality
it goes from the object to the mirror, which reflects it to
If the image is behind the mirror why can you see it ?
the eye. How does the distance ON compare with the
distance O'N f How does the angle / compare with the
angle R at N ? AiSf At Tf The image we see is an
138
HOW WE USE LIGHT
Does this convex mirror give a real or an
unreal image ?
unreal image because there is no light that really goes to
the place where we appear to see the image. When a real
image is formed, as in a camera, rays of light actually form
the image where the
image is seen.
Curved Mirrors.
You have probably
seen a crystal globe.
This is a spherical
mirror. A small por-
tion of the spherical
surface would also be
called a spherical mirror. It is also a convex mirror.
Sometimes a convex mirror is placed on the fender or
on an arm projecting to the left of the wind shield of a
truck or automobile. The curved surface makes a larger
area visible, and an image is seen just as in a plane
mirror except that it is smaller. Perhaps you have
looked into the convex cylindrical mirrors at some
amusement park and have seen yourself tall and thin
or short and fat.
The inside of a
spherical surface is
concave. A con-
cave mirror will
focus rays of light
from a distant ob-
ject and make a
real and enlarged
image. Large
mirrors of this type
are used in the re-
How to look stout or thin. Why do some mirrors
change your appearance ?
fleeting telescopes for viewing the stars. Enlarging
mirrors are useful and can readily be obtained. The
dentist uses a small enlarging mirror to see your teeth
WHAT ARE SOME OF THE PROPERTIES OF LIGHT? 139
when filling them. A point equally distant from all
points on the surface of a curved mirror is the center of
curvature C. The point where parallel rays are brought
image
image
Where must an object be located with respect to F (focus) and C (center of
curvature) of a concave mirror to produce an enlarged real image ? An enlarged
unreal image ?
together after reflection is the principal focus F. This
focal point is about half way from the mirror to the
center of curvature. The position of the image depends
upon the position of the object. In science the unreal
image is usually called a virtual image. A concave mirror
is used for auto and locomotive headlights and for search-
lights. When a light is placed at a certain point in front
of the mirror, it sends out a powerful beam of nearly
parallel rays.
Diffused Light. When a beam of parallel light rays
strikes a smooth surface, it will be reflected in a beam of
parallel rays from the surface ; but if it strikes a rough
Why does a rough surface diffuse light ? Does the same law of reflection hold
in the two cases ?
surface, the light will be thrown off in different directions
and scattered. Such light is diffused. Light from the sky
140
HOW WE USE LIGHT
is diffused, because air is filled with countless millions of
tiny irregular dust particles. These particles divert the
rays of the sun out of their straight course and give diffused
light. Without the atmosphere to diffuse the sun's light,
the earth would look very different because contrasts
would be much greater than they are now. The whole
sky would appear black in the daytime except for the
luminous disk of the sun and the points of light made
by the stars. In winter our north windows would receive
no light at all. It is fortunate for us that the atmos-
phere with its particles of dust and moisture diffuses light.
Refraction of Light. A famous English philosopher
once noticed that if he put a coin in a cup and then stood
away from it so that he could just not see it, when he
poured water
into the cup,
the coin came
into view. This
curious happen-
ing is brought
about by the
fact that light
travels more
slowly in a dense
than in a less
dense material. When light enters the water, it slows up
and is bent from its course. There is one exception : a ray
of light passing into another medium of different density
at right angles (90°) to the surface between them is not
bent, but continues on in the same straight line. But
when any oblique ray of light passes from air into water,
it will be bent toward the perpendicular ; and when it goes
from water to air, it will be bent away from the perpendicu-
lar. The bending of light rays when they pass from one
transparent body to another of different density is called
Which is the real and which the apparent position of the
coin?
WHAT ARE SOME OF THE PROPERTIES OF LIGHT? 141
refraction. We appear to see objects in the direction in
which the light enters our eyes. Consequently if the rays
of light are bent before reaching our eyes, there is an
apparent displace-
ment of the body.
For this reason water
in a pond appears to
be more shallow than
it really is. In other
words, the earth at
the bottom of the
pond looks to be
nearer the surface
and has often de-
ceived adventurous
boys and girls who
could not swim. Fish in the water may not be in the
exact position in which you are looking when you see
them. It is refraction that bends the rays of sunlight
in a burning glass or lens and that makes letters look
larger in a reading glass.
§
plate glass
\l
c
2>
G,
\\
J\ \K
Passage of light through plate glass. Why is
only one of the rays bent ?
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
reflection
refraction
reflected
bent
send
bend
left
right
opaque
transparent
luminous
light
dark
equals
translucent
diffused
same
front
back
inside
outside
convex
concave
plane
smooth
directions
angle
image
angle,
When a beam of light comes to a window at a (1)_
some of the light is (2) back in the direction from which the
light comes. An (3) body does not transmit light. Frosted
142 HOW WE USE LIGHT
glass is called a (4) body because some light can get through
it. (5) bodies give out (6) of their own but most bodies
are seen by (7) light. When a smooth body reflects light, the
angle of (8) (9) the (10) of incidence. The (11)
in a mirror is always the (12) distance (13) of the mirror
as the object is in (14) of the mirror. Rough surfaces give a
soft (15) light, while (16) surfaces tend to produce a glare
if looked at from some (17) (18) mirrors can produce a
real image. The slowing up of light after it passes into a more
dense medium may cause it to (19) in a process called (20)
STORY TEST
MORRIS HAS SOME PRACTICAL EXPERIENCES WITH LIGHT
Read carefully and critically. List all the errors and suggest corrections.
Last night about an hour before sunset I looked across a vacant
lot to a greenhouse. At first I thought the place was on fire
because there was such a glare of light. I decided however that
I was seeing an image of the sun in each of the glass panes. Com-
ing at the angle that it did, all the light was reflected and the glass
acted like mirrors. After the sun had gone down, thunder clouds
quickly shut off the twilight and it became very dark outside. 1
turned on the lights in the room. I turned to the window and
looked in the direction of the greenhouse. I saw only objects that
were in the room around me. The glass that had been trans-
parent in the daylight had become opaque in the night and now
acted as a perfect mirror. Out of doors everything was dark
because it was in the shadow cast by the earth. A flash of light
from my aquarium called my attention to my one gold fish I had
put in the water a week before. As I neared the tank, I could
see through the top surface and through one side. Imagine my
surprise to see two gold fish, and stranger still, every time one
moved the other one moved. I then looked straight down through
the top surface but could find only one fish. I decided the optical
illusion had been caused by the reflection of the fish by the surface
of the water. So I had seen the real fish and his image in a mirror.
PROBLEM III. HOW ARE PHOTOGRAPHS MADE?
Have you ever seen among your family heirlooms a
daguerreotype : an old-fashioned picture on a piece of tin
set in a gilded frame? This old-type picture was the
HOW ARE PHOTOGRAPHS MADE?
143
forerunner of the great photographic industries of today.
Think of the persistence of a man working on the idea that
sunlight with the aid of a few chemicals could make a per-
manent picture. It took Daguerre fourteen years to work
out his idea. Some
others had devised
processes by which a
picture could be made
if exposed for hours
in a dazzling bright
light. But that was
not practical for
photographing people .
In 1839, Daguerre had
perfected his process
so that an exposure of
a few minutes was
sufficient to take the
picture. These were
made on a metal base
and no duplicates
could be printed from
it. Today a fraction
of a second only is
In the first portraits made with a camera the
face had to be covered with white powder to
reflect as much light as possible. The sub-
ject was then exposed to direct sunlight before
the open camera for 30 minutes.
needed to expose a plate or film and from the negatives
any number of pictures can be printed. Such are the
strides made by science in a few years. Today photog-
raphy has become a leisure time activity for all, and
the pages that follow will help you to enjoy this scientific
pastime.
The Camera. We think of a camera as a light-tight
box having a lens at one end and a place at the opposite
end for a prepared photographic plate or film. But there
is a simpler camera than that because pictures can be
taken without a lens. In such a camera there is only a
144
HOW WE USE LIGHT
pinhole in the front end of a small box. Brightly lighted
objects in front of the pinhole send light through it and
an image is formed at the
back of the box. If a film
coated with chemicals
sensitive to light is there
to receive the image, the
start of a photograph is
made. The advantage of
having a lens instead of
the pinhole is that it pro-
duces a sharp image when
the opening is large, thus
permitting more light to
enter. This shortens the
time of exposure. With
a pinhole camera any
opening larger than a
small pinhole l will make
a blurred image. With a hole small enough to give a
good sharp image, it will take from 10 to 20 minutes to
make the exposure.
The Diaphragm and
Shutter. The lens camera
has a diaphragm, the ad-
justment of which makes
possible different sizes of
opening through which
light may enter. There
is a shutter controlled to
allow an exposure of a
fraction of a second for a
"snap shot" exposure or
r , Can you tell the use of each of the parts
for a time exposure when Of the camera named in the diagram ?
1 See page 162 for directions.
Eastman Kodak Co.
The camera used by amateur photogra-
phers.
lens
HOW ARE PHOTOGRAPHS MADE? 145
over a second is needed. The shutter and diaphragm are
controls for the amount of light which is allowed to pass
through the lens to produce the image on the film.
Lenses. If you can get two lenses of the same diame-
ter but one thicker through the center than the other, you
will be able to make an interesting experiment. If you
are in a partly darkened room, light a lamp and hold the
thick lens five or six feet from the lamp. Move a sheet
of white paper back and forth on the side of the lens away
from the light. You will soon find a place where a sharp
image of the lamp appears on the paper. Now if you
place another lamp a foot forward or back of the first and
keep the paper still, you will see that objects at different
distances give a fairly sharp image. If you repeat this
with the thin lens, you will not be able to produce a sharp
image of the two lamps when they are very far apart.
The thick lens is a short-focus lens, and this is the type
used in the box camera. You do not have to change the
position of the lens or "focus" the camera because this is
a " fixed focus" lens, that is, all objects in front of the
lens and more than six feet distant will produce an image
which is fairly sharp. Other cameras — the focusing type
-use the long focus lens. For photographing near-by
objects with such a lens the distance from the film must
be adjusted according to the distance scale on the camera,
but all objects over 100 feet away will give a sharp image
when the lens is set at the 100 mark on the scale.
What Makes Some Cameras Expensive? You may
have wondered why some people pay $50 to $100 for a
special lens for a camera. They are paying for the speed
of the lens. Only the central portion of the cheap lens
can be used to give a sharp image. If the diaphragm is
closed so that light enters through the center only, a longer
time must be used for exposing the plate. The expensive
lens is ground so carefully that the diaphragm may be
H. & W. SCI. I — 11
146 HOW WE USE LIGHT
opened much wider and still give a sharp image. This
lets more light in and shortens the exposure, and the lens
is called "rapid." The cheap lens may give just as good
a picture if you can give it sufficient time with the small
opening.
Making a Negative. Many of you take pictures but
give the films to a photographer to develop. If you do
this, you lose half the fun. Why not learn to develop the
films yourself? Most junior high schools have camera
clubs and dark rooms, so you will have no difficulty in
doing your own work. The plate or film is coated with
gelatin containing silver bromide, a substance sensitive to
light. When light from an object in front of the lens is
focused on the film, it makes an image upon it which does
not become visible until after the film is developed. De-
velopment takes place in a dark room which has only a
red or ruby light in it. This light does not act upon the
film during the short time required to change it into a
negative. The film is first treated with a "developer,"
a chemical solution which causes a deposit of dark particles
on the film. No dark deposit is made on those parts of
the film not reached by the light. The differences of
light and dark at any point is in proportion to the amount
of light which acted upon the silver bromide. When
development is complete, some silver bromide which was
not acted upon by the light and which is still sensitive to
it remains on the film. Before the film can be exposed
safely to ordinary light, this silver bromide must be re-
moved. A chemical salt, hyposulphite of soda, called
"hypo," will dissolve the silver bromide and remove it
from the film. This is used as a "fixing bath," because
it makes the image permanent. After the film has been
fixed, washed, and dried, the light and dark areas in it are
just the reverse of those in the original picture and for
this reason it is called a negative.
HOW ARE PHOTOGRAPHS MADE?
147
Which is the positive and which is the negative ? How do the lights and shades
in the negative compare with the lights and shades in the positive ?
Making a Positive. The print is made by allowing
white light to pass through the negative to a paper which
is sensitive to light. Since less light will pass through the
dark parts than through the light parts of the negative,
the print will be just the reverse of the negative, or a
positive, which has the same value of light and dark as the
original objects photographed. Home printing is easy
and is a fascinating pastime. Papers are of two types,
those printed by artificial light and those printed by sun-
light; the former require more time. Blueprint paper
is one form of sun-printing paper ; it is cheap and easy
to handle since it can be developed in water without the
use of chemicals.
Demonstration 2. Making a Print from a Negative.
Darken the room until you can barely see objects. Make up a
developing bath by dissolving the powders in a tube of developer
in water according to directions on the tube. Make a hypo
(" fixing ") bath by dissolving a tablespoonful of hypo (hypo-
sulphite of soda) in half a pint of water. Arrange three trays or
plates as follows :
148 HOW WE USE LIGHT
Tray 1. Developer Tray 2. Cold water Tray 3. Hypo
You will need two squares of glass and two clothespins. Lay the
negative dull side up on one piece of glass. Upon this lay a sheet
of sensitized paper, smooth or coated side down upon the negative.
Cover with the other piece of glass. Hold the two pieces of glass
tightly together with the clothespins. Light a 100-watt lamp
and hold the glass film side towards the light and 3 feet from
it for 10 to 15 seconds. Extinguish the lamp. Remove the paper.
Immerse the paper in the developer. If it comes up too black
within 30 seconds, it had too much light; if it does not come up
dark enough in 30 seconds, it needs longer exposure. A little
experience will help you judge the time of exposure. After the
picture has developed to the point you wish it, rinse quickly in
water and place in the hypo. Move it around occasionally.
After, 15 minutes remove from the hypo and wash an hour in run-
ning cold water. Lay face down on a piece of cheesecloth stretched
over a frame to dry.
With the directions just given you should soon become an expert
amateur photographer. Why not organize a camera club if your
school does not have one? You will be surprised how much this
photography will help you in your science work, besides giving you
and your friends a lot of fun.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order
A word may be used more than once.
chemical positive fixed camera
visible negative focus image
diaphragm neutral opening black
shutter hypo closed light
developer acid dark lens
results recorded red sensitive
There are chemicals which are (1) to light. When these
chemicals are held on the surface of a film or glass plate in a little
gelatin and an (2) is thrown upon the film, a latent image is
(3) When the film is developed, a picture with (4) and
(5) parts reversed from what they were in the original view
(6) After development, the film is (7) or made perma-
nent in the (8) bath. The resulting film is called a (9) ;
from this a (10) print is made. The (11) excludes (12)
except when the (13) is open. The size of (14) to control
the amount of light is regulated by the (15)
HOW DOES THE EYE RESEMBLE THE CAMERA? 149
STORY TEST
ALBERT TELLS ABOUT His PINHOLE CAMERA
Read carefully and critically. List all the errors and suggest corrections.
This box I hold before you is a " pinhole " camera. I made a
large hole in the front end of the box. Then I made a small hole
in a piece of tinfoil with a needle and fastened this so-called pin-
hole over the hole in front of my box. I fastened a film in the back
end of the box in a dark room, put the cover on, held my hand over
the pinhole, and came out into the light. I placed the camera six
feet from a bouquet of flowers which were in the sunlight. All
of the rays of light given off by the flowers went through that tiny
pinhole. They were bent as they went through and then made
an image on the film. After covering the hole and returning to
the dark room, I found the film had a picture of the flowers on it.
To make this remain on the film, I developed the film in a solution
called the developer. I washed the film and dried it in a lighted
room because light cannot hurt it after development. After the
film was dry, no picture was visible on it, but by printing on sensi-
tive paper I could make a beautiful picture of the flowers. I
haven't done this yet, but I know just how to do it. Place the
paper on the film, coated sides together. Hold film towards the
light. Then put paper into a hypo solution to fix it and to make
the print permanent. Wash and dry.
PROBLEM IV. HOW DOES THE EYE RESEMBLE
THE CAMERA?
We all know that the camera in its simplest form is a
black, light-tight box containing a lens at one end and a
place for a sensitive film at the other. Light is allowed
to pass through the lens and is brought to a focus on the
film. Here the picture is recorded on the film, which may
be taken to a dark room and developed and made per-
manent. The human eye is like a camera in many ways,
but it is much more delicate and complex. If we were
to take a section through the human eye at right angles
to the front of the face, we would see its likeness to the
camera. Near the front of the eye is a transparent lens
which throws a picture on a surface called the retina, at
150
HOW WE USE LIGHT
the rear. The retina is connected to the brain by the
optic nerve. The lens is capable of changing its shape,
-lens
film...
What parts of the camera correspond to the parts of the eye ?
thus making it possible to focus the light and so make a
real image of near or distant objects on the retina. This
change of focus is called accommodation. A colorless fluid
fills the space between the lens and the retina. The
retina is the most wonderful part of the eye because it
transfers the sensations produced by light in the eye to
the brain by way of the optic nerve.
How the Eye Adapts Itself to Different Intensities of
Light. The diaphragm in the camera changes the size
of opening through which light may enter. The eye has
a similar device, but it is called the iris. The black spot
you see as the pupil of the eye is the opening through
which light passes to the lens. If you go to the window
when there is bright
sunlight and look
steadily at the sky
for a moment, and
then bring a mirror
before your eye you
will see that the size
of the pupil or black
hole in the colored
iris is extremely small. If you turn quickly to a dark
part of the room and look in the mirror, you will see
the pupil grow larger as the iris adjusts itself to the
How does the eye adjust itself to different
intensities of light? Which of the two eyes is
looking into a bright light ? How do you know ?
HOW DOES THE EYE RESEMBLE THE CAMERA? 151
smaller amount of light. This change in the size of
the pupil is automatic. The eye cannot stand looking
into very strong light, nor into a glare, in spite of
this adjustment. The iris cannot contract enough to
shut out the intense light without also making it
difficult to see objects or printed matter. We should
therefore avoid straining the eyes by trying to work or
read with a bright or glaring light within our field of
vision.
Some Eye Defects. In spite of the wonderful mechan-
ism that it is, the eye often has slight defects. The most
use a Conclave lens to correct.
1135
use a convex lews to Correct. fansigktecCness
common one is astigmatism, due to a slight uneven cur-
vature of the lens or the cornea. This difficulty is a fre-
quent cause of headaches, and should be attended to by
an oculist.
Another defect is nearsightedness. In this case the
eyeball is too long from front to back or the lens too thick,
so that the image of distant objects is brought to a focus
before reaching the retina. If you have to hold your book
close to your eyes, and if you squint when looking at
things, you should go to an oculist and have your eyes
tested for glasses, as nearsightedness can quickly be cor-
rected by this means.
152
HOW WE USE LIGHT
What can you say about the light here? Have you any suggestions to offer?
Farsightedness is a defect in which the eyeball is too
short or the lens too thin and the image of near objects
is focused behind the retina. This defect is more
difficult to detect and is also the cause of many head-
aches. Properly shaped lenses will remedy both
nearsightedness and farsightedness by bending the
light rays so that they focus properly by means of
refraction.
Care of the Eyes. Some good rules for care of the eyes
are these :
1. Avoid direct glare or reflection from paper, books,
or highly polished surfaces.
2. Do not sit facing strong light.
3. Do not sit so that your shadow falls on your
work.
4. Do not read or work by a flickering light.
5. Do not read on trains or motor cars.
6. Adjust the intensity of light to your needs. Strong
light is needed for fine print.
HOW DOES THE EYE RESEMBLE THE CAMERA? 153
7. Do not use the eyes when they ache or when you are
fatigued. Remember that your eyes are the most valu-
able asset you have. Never abuse them. If tired, a
wash of boric acid will help. Do not use any patented
drops as they may contain dangerous poisons, and usually
you buy only boric acid and salt, which you could mix
yourself. Above all, consult a reliable oculist or eye
specialist in case your eyes need attention.
SELF-TESTING EXERCISE
Select from the following list those words which best Jill the blank spaces
in the sentences below and arrange them in proper numerical order. A
word may be used more than once.
front reading image automatically
back cornea bend accommodation
side iris decreases glasses
lens retina increases shaped
mirror pupil curvature astigmatism
harmful light focus enters
beneficial diaphragm inverted farsightedness
It is the (1) of the eye that produces an (2) on the
(3) The amount of light which (4) the eye is regulated
by the (5) which (6) and (7) the size of the
(8) It is very (9) to have light directly in (10) of
one when (11) Uneven (12) of the (13) or of the
(14) may cause (15) In nearsightedness the image is in
(16) and in farsightedness the image is in (17) of the retina.
(18) to correct these defects may be (19) , so that they
bend the rays of light to make them (20) properly.
STORY TEST
BEULAH'S FATHER Is AN OCULIST
Read carefully and critically. List all the errors and suggest corrections.
My father is an oculist and fits people with glasses. I have
an uncle who is an optometrist; he treats diseases of the eye.
So you see I am just the one to talk to you about the human eye.
In the first place the eye is rounded or ball-shaped ; this makes it
154 HOW WE USE LIGHT
act upon light like a lens. When light from an object passes
through the eye, it forms an unreal or virtual image on the cornea.
The position where an image is formed depends upon the distance
the object is from the eye. However, the eyeball can change its
shape and move the back surface of the eye nearer or farther away
from the pupil. This is taken care of automatically so that in the
normal eye there will always be a clear image formed. This
adjustment is called accommodation. Father says most people
wear glasses to remedy eye defects but some wear them for " looks."
PROBLEM V. WHAT IS COLOR?
What Is White Light ? If you pass sunlight through a
triangular piece of glass called a prism, the white light
is separated into the following colors : red, orange,
yellow, green, blue, and violet. The waves of all these
colors differ in length. The longest wave affecting sight
gives us the color red, the shortest, violet. Color, then,
is a property of light which depends upon its wave length.
When light is refracted, the blue rays are bent more than
the red rays, or the shorter the wave length, the more it is
bent. The prism bends the beam of light twice in the
same direction, once as it enters the glass and again as
it leaves the glass and enters the air. Both times it
separates the colors and so produces a band of colors on
a screen. This band of colors is called the "solar spec-
trum." The rainbow is caused by light being broken up
into these colors by
bending or refrac-
tion in falling rain-
drops. When all
the different wave
lengths from the sun
Why does a prism separate sunlight into colors ? . -, , ,-,
are mixed together,
white light is produced. White substances are those which
reflect all wave lengths, hence all colors, while black sub-
stances are those which absorb all wave lengths of light.
WHAT IS COLOR?
155
Colored Objects. A red body absorbs all the wave
lengths except those producing the sensation of red. A
•\vkite
light.
green
fight.
White peeper- gV-eerj. -peeper
Why is such a small part of the light falling upon the green paper reflected?
blue body absorbs all the wave lengths except those pro-
ducing a sensation of blue. Make a blue spot on white
paper and an orange spot a few inches from it and then
look at the two colors
by means of a glass
plate held vertically
between them so that
one spot is seen by
transmitted light and
the other by reflected
light. A grayish
white spot will re-
sult. Any two colors which when mixed give a sensa-
tion of white or gray are complementary colors. Red
glass absorbs all rays except those producing red, hence
a blue dress if viewed in a room having red window glass
would appear black. This
is due to the fact that
no blue comes in to be
reflected and the dress
absorbs the red. Every
color except red would
appear black when viewed
What is the color of the piece of glass? in a red light.
What is the color of this leaf?
o a
156
HOW WE USE LIGHT
Mixing Pigments. Mixing pigments such as paints
or dyes is quite a different matter from mixing colored
lights or light rays. If you mix blue and yellow paint,
\
Why do only yellow rays appear at the right of this diagram ?
green will result. A yellow pigment absorbs all the spec-
trum colors except yellow and green, while blue pigments
absorb all the spectrum colors except blue and green.
Green is the only color reflected by both pigments, and is
therefore the only color seen when the two are mixed.
Color Blindness. In order to drive a locomotive, the
engineer must be tested for color blindness. There are
about three to four per cent of boys and about one per
cent of girls who cannot distinguish certain colors. They
are color blind. The most common form of color blind-
less is the inability to distinguish between red and green.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
wave
waves
reflects
light
colors
complementary
darkness
red
green
blue
property
refracts
neutral
normal
violet
white
black
length
absorbs
yellow
pigments
sensations
supplementary
length
Color is a (1) of (2)_
length. The shortest (4).
which is determined by its (3)_
(5) gives the sensation
of
WHAT IS COLOR? 157
(6) and the longest produces the sensation of (7) All
(8) produced in the sun mixed together give (9) Any two
colors which when mixed produce white are (10) colors. Blue
and yellow (11) when mixed produce (12) If you look at
a red book through blue glass, it will appear (13) because the
glass transmits only (14) and the book (15) blue.
STORY TEST
HARRIET REPORTS UPON HER EXPERIMENTS
Read carefully and critically. List all the errors and suggest corrections.
Having an uncle who is a glass maker, I teased him to make me
three prisms ; one of white glass, one red, and the third green. I
used these in a dark room into which a beam of sunlight came
through a small hole in the shutter. I had a screen of white paper,
one of black paper, one of green, and wore a red dress. When I
held the white glass in the beam of sunlight to form the solar
spectrum, the colors could be seen upon the white screen. When
thrown upon my red dress, the whole beam was changed to red.
When thrown upon the green screen, I saw only a small green band
of color. I then took the red prism and made a spectrum of all
colors on the white screen. When thrown on the red dress, the red
was absorbed and all the other colors were seen. Then I used the
green glass. When the black paper was held in position, there
was just a narrow green band of color upon it, but it showed a red
band when the beam was directed to the red dress. The green
screen showed a green color and the white screen showed all the
spectrum colors.
THE REVIEW SUMMARY
In preparing a summary of what you have learned in this unit,
you will want to place emphasis on the big ideas which have come
out of the applications of the facts you have learned and the demon-
strations you have seen. The generalizations that can be made
on this unit are numerous. You may change the list that follows
if you so desire, as this is only giving you a partial list of those
that you might make for your review summary.
158 HOW WE USE LIGHT
1. Light travels with greater speed than anything else.
2. Light travels in straight lines.
3. Light rays may be bent by reflection or by refraction.
4. Light produces chemical changes of much value to man.
Before making your review summary, test your knowledge of
the facts of the unit by checking over the text so as to be sure you
know the facts underlying the generalizations. Then, using the
generalizations, the material in the text, and everything you have
read, seen, or done yourself, make a summary outline for your
notebook. This outline you may use when you make a recitation.
TEST ON FUNDAMENTAL CONCEPTS
Make two vertical columns in your workbook. Head one CORRECT
and the other INCORRECT. Under the first place the numbers of all state-
ments you believe to be correct. Under the second place all the numbers
of the statements you believe to be incorrect. Your grade = right
answers X 2^.
I. Light travels : (1) in straight lines ; (2) through translucent
bodies; (3) 1100 feet per second; (4) more slowly through water
than through air.
II. A real image may be produced: (5) by a plane mirror;
(6) by a piece of plate glass; (7) by a pinhole camera; (8) by a
concave mirror.
III. A beam of light will be bent (refracted) when it goes from :
(9) air into glass at a 90° angle to the surface ; (10) air to glass at a
30° angle; (11) water into air at right angles to the surface;
(12) water into air at an angle of 60° between the ray and the
surface of the water.
IV. The ordinary camera lens produces a real image on the film
because the lens : (13) reflects the light from the object; (14) re-
fracts the light coming into it; (15) sifts or filters out the objec-
tionable rays of light which would mar the image; (16) permits
light from the object to reach the film.
V. When a beam of light from candle flame comes to a piece of
plate glass at right angles to the surface, some of the light : (17) is
refracted; (18) is reflected; (19) is changed to a gas; (20) is
transmitted.
VI. The image of an object in a plane mirror is : (21) larger
than the object ; (22) unreal ; (23) the same distance back of the
mirror that the object is in front of the mirror; (24) inverted.
VII. Concave mirrors: (25) may produce real images; (26)
are used in some telescopes ; (27) are used in cameras ; (28) are
used in automobiles to watch traffic in the rear.
WHAT IS COLOR? 159
VIII. You are on one side of a stream of quiet water and see a
large oak tree on the other side. The sun shines brightly and
lights up the side of a tree towards you : (29) you see a real image
of the tree in the water ; (30) there is also a shadow of the tree on
the water; (31) as you see the image, the tree appears upside
down ; (32) the image is unreal.
IX. The eye " focuses " or makes the image on the retina
clear by : (33) changing the distance between the retina and lens ;
(34) changing the thickness of the lens ; (35) changing the size of
the pupil; (36) by a process called "accommodation."
X. A blue dress appears blue in daylight because : (37) the
material absorbs only blue light from the sunlight ; (38) the
material absorbs all the sunlight except blue; (39) its own color
added to sunlight gives blue ; (40) it gives out blue color of its
own which is stronger than the white of sunlight.
THOUGHT QUESTIONS
1. Why are lamp shades made of opal glass?
2. Why are electric light bulbs frosted ?
3. Why are offices in large buildings often inclosed in trans-
lucent glass?
4. Make a list of the objects you saw on your way to school
that showed regular reflection.
5. How would you point a stick to a given point at the bottom of
a dish of water if your stick has to enter the water at an acute
angle ?
6. Compare a real and an unreal image and show how you
would make each.
7. Why do the re-
flectors used for auto-
mobile headlights have
the shape shown in the
illustration ?
8. Why is the image
seen in the back of a
camera inverted but that
seen in the finder up-
right? »
9. What happens to a beam of bright sunlight by which you
see the white sand on the beach: first without glasses and later
through amber sun glasses ?
10. Why is it difficult for you to write your name while looking
at your hand, pencil, and paper only in the mirror ?
160
HOW WE USE LIGHT
11. How can you adjust your desk study light to give you
efficient lighting ?
REPORTS UPON WHAT I HAVE READ, DONE, OR SEEN
1. Report upon an article related to some topic discussed in
this unit. The article may be from a current number of a science
magazine or from some popular science book you have read.
a. The importance of transparent glass.
6. Colors in the sky.
c. An automobile headlight.
d. The eyes of man and of insects.
SCIENCE RECREATION
1. FUN WITH SHADOWS
Hang a sheet to cover a doorway. Have the audience in a
darkened room. In the other room have one very strong light.
'
1 ctttcCievice
1 i
v
\
actors-
reflector
stroi
Make pantomime shadow pictures by acting between the light
and the screen. Plan a shadow play.
2. AN "ANGLESCOPE"
Sometimes you like to watch a person without his suspecting
it. You can apparently be looking through a tube in one direction,
mirror-
but really see what is going on at one side.
The diagram will suggest how to place a mirror
in a mailing tube having a hole cut in the side.
3. MAKE A PERISCOPE
Secure a long mailing tube about 2 inches in
diameter and two small mirrors (2 for a nickel
.Mirer
WHAT IS COLOR?
161
Cover one end halfway across,
-IBS.
at the 5 and 10). Cut holes near the ends of mailing tube but
on opposite sides. Fasten the mirrors back of these openings
facing and parallel to each other but at angles of 45° to the
long axis of the tube. Then objects in front of the top opening
can be seen by looking into the lower opening.
4. A HOME-MADE KALEIDOSCOPE
Fasten two strips of mirrors about 2" X 1" or 8" together with
the mirror fronts facing each other at an angle of 45°. A tin frame
can be bent so it will hold there,
leaving a peep hole where the
two glasses meet. Cover the
wide open space two inches from
the end. Support this vertically
with the peep hole at the top
above a block of wood, leaving a
space under it where a disc can
be placed so it can be revolved
under the two mirrors. By plac-
ing colored chips of glass and
other objects upon the disc,
different patterns and designs
may readily be produced.
5. MAKE A SCRAPBOOK ON LIGHT
Collect pictures and clippings from newspapers and magazines.
Group the clippings according to subject matter.
mirrors— v
'revolving
^
SCIENCE CLUB ACTIVITIES
1. TEST FOR COLOR BLINDNESS
Buy or borrow a set of Holmgren's woolens for testing color
blindness. Test the eyes of each member of the club.
2. MAKING A PICTURE
Get some one who knows how to demonstrate the use of a camera
with a ground-glass back, also how to print and finish a picture
from a negative.
3. BURNING A CANDLE IN A JAR OF WATER
Arrange your apparatus as in the diagram on page 162. The
plate glass should be 15 to 24 inches by 3 to 4 feet. Double-
thickness glass may be substituted. The jar of water is seen by
transmitted light, and the candle by reflected light. Have the
H. & w. sci. i — 12
162
HOW WE USE LIGHT
candle burning and jar empty at the start. Pour water slowly
into the jar. Your audience expects the candle to burn until the
water reaches the wick,
but it continues to burn
until they see the water
well above the top of
the flame. If the jar of
water is shown by re-
flection, hold the candle
where the audience can
see it. Have the match
ready. Have the cur-
tain closed while you
" place the candle in the
jar of water and light it."
You have the proper spot
marked on the table
where you place the
candle. After lighting
it, have the curtain
drawn aside and the
audience sees the candle
burning in the jar of
water. Test the posi-
tions before the audience
arrives.
4. MAKE A PINHOLE CAMERA AND TAKE A PHOTOGRAPH WITH IT
A small prize may be offered for the best picture made by a
member of the club. A pinhole camera may be made in the follow-
ing way. Use a box about five inches square and three inches deep.
It must have a cover which slides down over the box for a depth of
at least one inch. The interior must be painted black and made
light-tight. Cut a hole one half inch in diameter in the middle of
one side or end of the box. Paste a piece of tinfoil on the inside of
the box over the hole. Make a pinhole in the center of this tinfoil.
The success of your picture depends on the care with which you
make this hole. The best results are obtained when the diameter of
the pinhole is in proportion to the square root of the distance from
the pinhole to the plate.1
1 Use the following formula :
Diameter of pinhole = # ^Distance of plate from pinhole
K = .0008
This diameter may be measured by some machinist or science in-
WHAT IS COLOR? 163
Paste cardboard strips on the inside of cover to hold the sensitized
plate.
The picture is made on a glass plate which is held in place by
narrow strips of cardboard glued in along the vertical edges of the
plate. This plate is to be put into the camera while in a dark room.
Of course, the pinhole should be kept covered until you reach the
object you wish to photograph and covered again after the picture is
taken. The exposure, depending on the light, should be from ten to
twenty minutes.
REFERENCE READING
Comptoris Pictured Encyclopedia.
Bragg, Sir William, The Universe of Light. Macmillan, 1933.
Dull, C. E., Modern Physics. Holt, 1929. Page 404-498.
Houston, E. J., The Wonder Book of Light. W. and R. Chambers, Ltd.
Luckiesh, M., Artificial Light. Century, 1920.
Meister, M., Energy and Power. Scribner's, 1930.
Whitman, W. G., Household Physics. Wiley and Sons, 1932. Prin-
ciples of Light, pages 272-290 ; Natural Light, pages 292-308 ; Arti-
ficial Light, pages 310-321 ; Illumination, pages 322-342.
structor who has a micrometer caliper, with which to measure the needle
so you can make the hole just the right diameter.
Having obtained a needle of the right diameter, do not force it all
at once into the tinfoil, but push it in slowly, first on the one side, and
then on the other so as not to tear the foil. When you have made the
hole, be sure to smooth off the edges, as a clear picture cannot be made
unless you have a clean cut hole.
SURVEY QUESTIONS
Do you know what magnets are and
what they are made of ?
What are some uses of magnets ?
How does a compass tell direction ?
Can a person become charged with
electricity?
Do you know what electricity is ?
Can you produce electricity ?
Can you name a good conductor and
tell how it is used ?
Can you name a good insulator and
show how you would use it ?
V
Edwin Levtck
UNIT VII
HOW WE MAY PRODUCE ELECTRICITY
AND MAGNETISM
PREVIEW
Long before the birth of Christ, it was known that a
certain kind of iron ore which came from Magnesia in
Asia Minor had the property of attracting other small bits
of iron. To this ore, the name of magnetite was given,
from which we get our word " magnet." Early peoples
called these stones "lodestones" or leading stones, and
thought they had magical powers. Although these
magical stones were known to the Greeks 600 years before
Christ, the Chinese are credited with having made the
first practical use of magnets, for they discovered that a
lodestone if it floated on a block of wood in water always
pointed in a north-south direction. This discovery paved
the way for the development of the mariner's compass
in Europe in about the eleventh century. Thus it was
that the magical lodestone enabled adventurous sailors
and explorers like Columbus to sail away out of sight of
land to discover new lands. In 1576 it was discovered
that a compass needle properly supported would dip
toward the poles of the earth unless one were on tne equa-
tor. This caused William Gilbert in 1600 to conclude
that the earth acts as a great magnet and attracts com-
pass needles more strongly in some places than in others.
Later still, in 1831, the arctic explorer, Ross, discovered a
magnetic pole 1200 miles south of the north pole of the
earth.
165
166
HOW WE PRODUCE ELECTRICITY
The influence of the earth's magnetism extends far out
into space, and may be one cause of the displays of " north-
ern lights" or aurora seen in the sky of the northern and
southern hemispheres. You have all heard of "sun
spots." While we do not know just what they are, scien-
tists find that the activity of sun spots is closely asso-
ciated with the magnetic
activity on the earth.
There are many interest-
ing facts which we can piece
together in telling the story
of how electricity has been
harnessed and has become
the most powerful of man's
servants. The Greeks
learned of one property of
electricity when they
rubbed amber, which they
called electron, and found
that it would pick up small
particles. When Franklin
sailed his kite in a thunder-
storm and discovered that
lightning was a form of
electricity, another step was
taken. rAnd when Galvani,
the Italian scientist, found
that the legs of dead frogs
twitched when he brought
them into a circuit with iron and copper, still another
important fact about electricity was discovered. Then
came Volta with his discovery that electricity could be
generated by chemical means. We might go through a
long list of discoveries, each of which gave us more and
more knowledge about electricity.
Franklin took chances with his kite, but
he discovered that electricity could be
conducted through the wet kite string.
What danger did he expose himself to ?
WHAT CAN MAGNETS DO?
167
PROBLEM I. WHAT CAN MAGNETS DO?
People have not always depended on lodestones for
magnets. It was discovered long ago that magnets could
be made out of
steel by rub-
bing the steel
with another
Ar How will this change the properties of the knife blade?
magnet. You
can make a small magnet yourself. If you stroke a
needle from the middle to the point several times with
one end of a magnet and then, using the other end of
the magnet, stroke it from the middle to the opposite
end, you will make a magnet of the needle. You can
make a magnet of any piece of steel in the same way.
Large powerful magnets are made by passing a current
of electricity through wires
which surround iron or steel
cores.
What Will a Magnet At-
tract ? If we lay steel needles,
pins, tacks, gold pins, silver
pins, pure nickel, a nickel
coin, a copper coin, and a
brass key on the table and
move a bar magnet slowly
over them, will anything hap-
pen? What substances are
the
placed
near- all
objects
n««<€le
iron nail
What substances will a magnet pick
up?
picked up ? We see as a re-
sult of this experiment that a
magnet will not pick up all metals. It has been found that
magnets will attract iron, steel, pure nickel, and cobalt,
but will not attract any other common substances.
Permanent and Temporary Magnets. If you place a
powerful bar magnet over a dish of iron nails, you will
168
HOW WE PRODUCE ELECTRICITY
find that they cling to each other as well as to the magnet.
If you separate the magnet from the nails which are
touching it, all the nails will immediately cease clinging
to each other. Magnetized nails may cause other objects
such as soft iron or tacks to become magnetized for a
time, but as soon as they are loosened from the perma-
nent magnet, they lose their magnetic properties. Even
permanent magnets may lose their power after a while,
especially if they are
heated. Permanent
magnets are made
of steel or of some
alloys of steel ; tem-
porary magnets are
made of soft iron.
What Happens to
a Suspended Mag-
net? Take a long bar
magnet and suspend
it by an untwisted
Can a bar magnet be substituted for a compass? gtrmg g() that it
swing in a horizontal plane. It will take a position in a
north-south line. We may check this with a compass.
That end of the magnet pointing north is called the north-
seeking or north pole, and the other end is called the
south-seeking or south pole of the magnet. Since all
magnets have this property, a magnetic needle is used in
the mariner's compass.
How to Make a Compass. Magnetize a needle by rub-
bing it on a bar magnet. Cut off a thin sheet of cork and
float the cork in a dish of water. Lay this magnetized
needle on the cork. What position does it take? Put
a needle that is not magnetized on the cork. Does it
act in the same way ? How could you find east and west
if you had a compass ?
WHAT CAN MAGNETS DO?
169
How to Use a Compass. In the pocket compass the
needle is free to move over a disk on which the points of
the compass are printed. If the compass is put down flat,
the needle of the compass will move to and fro until it
finally points to the magnetic north. If now the disk of
the compass is shifted so that the N on the disk is just
under the needle, all compass directions will be shown
approximately correct.
Demonstration 1. To Determine the Laws of Magnetic Poles.
(a) Do both poles of a magnet attract magnetic substances? Bring
the north pole of a bar magnet into a pile of iron tacks. Test the
south pole in the same way. Test the center of the bar. Compare
results. Do both poles of the magnet attract a magnetic substance?
Does the equator of the magnet show strong attraction?
(6) Relation of magnetic poles to each other. Suspend a bar magnet
vertically, N-pole down. Bring the south pole of a bar magnet near
the north pole of the suspended magnet. Bring the north pole of
the bar magnet near the north pole ; then near the south pole.
What are the results in each case? Make a statement concerning
the attraction and repulsion of magnetic poles.
Demonstration 2. To Magnetize a Steel Sewing Needle.
Drop the magnetized needle (p. 167) into iron filings on a sheet of paper.
Move the needle around and pick it up. Where do the filings cling?
170 HOW WE PRODUCE ELECTRICITY
Are there many at the ends or in the middle ? Clean off the filings
and break the needle into two parts. Place these in the filings.
What happens?
How the Magnetic Poles Act. These experiments show
us that not only do magnets attract certain metals, but
that if a magnet is cut in two parts, it will continue to be
magnetized. We notice that the greatest attractive force
is nearest the ends of the magnet. If we bring the north
pole of one magnet near the north pole of a suspended
magnet, the north pole of the latter moves away. If we
bring the south pole of a fixed magnet to the north pole of
a movable one, the south pole is drawn toward the north.
This always occurs when two magnets are brought to-
gether and gives a law which we may state as follows :
Like magnetic poles always repel, and unlike magnetic
poles always altract each other.
Demonstration 3. To Show the Magnetic Field.
Place a bar magnet under a piece of white paper with a strip of
board of the same thickness on each side of it. Now shake iron
filings evenly over the paper. Tap the paper gently. Notice
what happens to the filings. Where are they most numerous?
How can you describe their arrangement on the paper? Make
a diagram of the magnet and of the lines of filings. How do they
compare with the illustration on page 171?
A Magnet Influences Space around It. Tacks or iron
filings will jump across the air space to a strong magnet.
A compass needle will turn when several feet away from
a strong magnet. These facts indicate that the influ-
ence of the magnet extends in all directions from the mag-
net. This force decreases as the distance increases. The
space about the magnet in which this magnetic influence
exists is called a magnetic field. If a compass is placed in
a magnetic field, the needle will take the direction of the
lines of magnetic force. These lines are considered as
WHAT CAN MAGNETS DO? 171
The magnetic field around a bar magnet.
coming out of the north pole, circling around, and enter-
ing the south pole of the magnet. The magnetic field is
seen clearly in the illustration above.
The Earth as a Magnet. If you had a magnet mounted
on a horizontal axis and you traveled with it from New
York over Canada toward Hudson Bay, you would find
that the compass needle pointed a little west of north, and,
as you went farther north, it would dip more and more
toward the perpendicular. If you were explorers, you would
find a place north of Hudson Bay where the compass would
point down toward the center of the earth. This is the
magnetic pole in our northern hemisphere. A similar
magnetic pole exists in the southern hemisphere. These
magnetic poles are each a good many hundred miles away
from the geographic pole where the earth rotates on its
axis. The earth, being a magnet, is surrounded by mag-
netic lines of force. It is because of these lines of force
that the compass acts as it does.
Value of the Compass. We only have to think of the
pilot on sailing vessels or steamers shut in by a dense fog,
or of aviators flying blind, to realize the great value of
the compass in modern life. For many years the great
steamships depended largely upon the magnetic compass.
172
HOW WE PRODUCE ELECTRICITY
Now they use a gyro-compass which is not magnetic and
which is superior to the old type. When Lindbergh made
his astonishing solo flight, he was able to put his ship
down on the field near Paris because he had worked out
his course exactly and had used the magnetic compass in
doing this.
Can you tell why a dipping compass needle would turn completely over if carried
around the earth through the poles ?
SELF-TESTING EXERCISE
Select from the following list of words those which best fill the spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
brass magnetic
iron magnetized
steel wood
silver non-magnetic
hard lines
soft surfaces
center (middle) opposite
surrounded
field
filled
earth
poles
water
equator
through
attract
repel
force
plane
passes
compass
SOME WAYS OF PRODUCING ELECTRICITY 173
Magnets made of (1) keep their strength much longer than
those made of (2) iron. A knife blade can be (3) by
stroking each half from the (4) with the (5) ends of a
strong magnet. Every magnet is (6) by a magnetic (7)
which is filled with (8) of magnetic (9) Like magnetic
(10) (11) but unlike (12) poles (13) each other.
The needle of the magnetic compass takes the direction of the
(14) lines of (15) of the (16) Magnetism (17)
through (18) which are (19) , such as glass, copper, and
wood. A magnet will attract only (20) substances.
STORY TEST
RALPH GIVES His OBSERVATIONS ON MAGNETS
Read carefully and critically. List all the errors and suggest corrections.
They make very powerful magnets out of an alloy of steel, nickel,
and cobalt. Nickel is not a magnetic substance because when I
tried to lift a 5^ piece with a magnet it was not attracted. I saw
two of these powerful magnets demonstrated. When the two
magnets were laid on the table with unlike poles together and
released they pushed apart because like poles repel. One magnet
would hold the other in the air above it when guides were placed
so that the top magnet could move only vertically and the north
pole of one was placed on the south pole of the other. The mag-
netic field was so strong that when a compass was placed 8 inches
away from the middle of the magnet the needle took a position parallel
to the magnet with its poles pointing in the same direction as those
of the magnet. When one end of a bar of copper was placed in
iron filings and the upper end of the copper touched with the magnet
the copper became a temporary magnet and when lifted iron filings
clung to it. I saw a magnet held horizontally, lowered into a pan
of iron filings and lifted. The largest mass of iron filings was near
the middle of the magnet because that is the place where the
magnetic force is concentrated. If a magnet is cut in two at its
center, the lines of force within the magnet will be cut off and all
the magnetism destroyed.
PROBLEM II. WHAT ARE SOME WAYS OF PRODUCING
ELECTRICITY?
You have sometimes made an electric spark when you
" scuffed" your feet over the carpet in winter or rubbed
the cat's fur the wrong way, or when your hair stood up
LUIGI GALVANI, 1737-1798.
Galvani was a native of Bologna, Italy. Born of good
' family, he was early destined for the church, but changed to
the profession of medicine. Later he became a professor in the
University of Bologna, where he became famous for his research
work. He had always been interested in the nervous system and
wondered why nerves responded to stimulation. A chance twitch-
ing of the leg of a frog he was experimenting with gave him the clew
for which he was looking. He found that when a moist frog's leg
was touched by two unlike metals it would twitch. Until the time
of Galvani no one had ever suspected the presence of a current of
electricity, although many experiments had been made with static
or frictional electricity, and people knew a good deal about magnets.
Galvani thought the movement of the frog's leg was due to an
electric fluid in this muscle, but a little later Volta, a professor in
the near-by University of Padua, proved that Galvani was wrong.
He showed that the electric current was due to chemical action
taking place between the two unlike metals connected by the moist
frog muscle. This made electricity on the same principle as it is
made in our galvanic batteries today, and made possible the flash-
light, our electric doorbells, and the hundreds of devices we use
today that depend upon the electric battery.
SOME WAYS OF PRODUCING ELECTRICITY 175
in an astonishing manner when you brushed it. When
the air is cold and dry, a hard rubber fountain pen or a
rubber comb rubbed briskly with flannel will attract
small bits of paper or a pith ball supported by a thread.
If the ball or the bits of paper become electrified, as they
sometimes will after clinging to the rubber for a moment,
they will be repelled and fly away from it. The hard rub-
ber was charged with electricity by friction. The objects
which touched the charged rod were electrified by contact.
Demonstration 4. Properties of Electrified Bodies.
You will need these materials : two large rubber balloons, string,
silk cloth, fur, glass rod, and a hard rubber rod. Fasten a string
across the room near the ceiling. Blow up two large rubber bal-
loons until they are tight. Fasten them on strings looped over the
ceiling string. Make them at a height level with your head and
six inches apart.
A. Rub one of the balloons with fur. Is there any action now
between the two balloons ? Between the balloon rubbed and your
hand held near it?
B. Arrange the balloons so that when neither is charged, they
hang just touching each other. Rub both the balloons with fur.
After you rub one do not let it touch anything until the second one
is rubbed. Release the two. What happens? Compare this
result with the one when only
one was rubbed.
C. Separate the two balloons
so that you can use one with-
out interference from the other.
Charge the balloon by rubbing it
with fur. Rub the hard rubber
rod with fur. Bring rod near the
balloon. Rub the glass rod with
silk. Bring the glass rod near
the balloon. What was the ac- ndt choked & rotor
tion between the hard rubber
rod and the balloon? Between the glass rod and the balloon?
Conclusion and Explanation. At first the bodies were neutral.
After being rubbed they were charged with electricity. Does a
charged body attract an uncharged or neutral body? Do two
of the charged bodies attract each other ? Repel each other ? Do
all charged bodies have the same properties ?
176 HOW WE PRODUCE ELECTRICITY
Charged Bodies. In this experiment we learned that
when a hard rubber rod is rubbed with fur, the rod repels
a rubber balloon which had previously been rubbed with
fur. But a glass rod rubbed with silk attracted the
balloon. Evidently there are two kinds of electric
charges. According to our present theory of matter,
each neutral atom is composed of a positive nucleus or
central portion. The particles which make it positive
are called protons. Negative particles of electricity
called electrons are believed to revolve around the nucleus.
The atom is normally made up of equal numbers of protons
and electrons, the former
being entirely inside the
nucleus . There is a strong
attraction between the
protons in the nucleus
and the electrons, but
some of the electrons can
be separated from the
Where did the electrons shown on the silk outer t of the atom
come from?
Protons never leave the
atom to go into another body. When we rubbed the glass
and silk together, some of the electrons were transferred
from the glass to the silk. This makes the silk negative.
The glass rubbed with silk having lost electrons now has
more protons than electrons and so it is positively electri-
fied. When hard rubber is rubbed with fur, electrons go
from the fur into the hard rubber, making the fur posi-
tively electrified and the hard rubber negatively electrified.
Whenever electrification is produced by friction between
two bodies, the positive charge produced in one equals in
amount the negative produced in the other. It was Ben-
jamin Franklin who first suggested the names positive and
negative for these two kinds of electrification. From
these experiments we can make the general statement
SOME WAYS OF PRODUCING ELECTRICITY 177
that two bodies with like charges repel each other, while two
bodies with unlike charges attract each other and a body
with either charge will attract a neutral body.
Conductors and Insulators. Soon after 1600, men
tried to electrify many substances. They decided that
metals could not be
electrified. In trying
to electrify a metal,
they held it in one
hand and rubbed it
with fur, silk, or flan-
nel, and in no case did
they get any result.
It was not until after
1700 that some one
held a stick of dry
wood which had a
metal on its end and
rubbed the metal with
fur. The metal re-
ceived a charge of electricity which was easily detected.
In earlier trials all the electricity produced in the metal by
rubbing was given off or conducted from the metal to the
hand which in turn conducted it away. This experiment
showed that in relation to electricity, bodies are separated
into two classes, conductors and nonconductors or insulators.
It was this property of some materials to conduct electric-
ity that gave Benjamin Franklin the opportunity to get
sparks from his kite string during the thunderstorm, and
suggested to him that lightning rods would protect build-
ings by carrying up streams of electricity from the earth
to the cloud above, or from the cloud down to the earth.
The charge on the cloud may be so reduced in this way
that the possibility of a huge flash to the earth through
the building is greatly reduced.
H. & W. SCI. I — 13
U. S. Forest Service
Lightning results from a discharge of electricity
between two oppositely charged bodies. Do
electrons play any part in lightning ?
178
HOW WE PRODUCE ELECTRICITY
Current Electricity. If we rub wax rapidly with a dry
piece of woolen cloth, we can electrify it. The wax is
then said to be charged with electricity. A charged body
such as this is one in which electricity is at rest. To be
sure, the amount in the wax is very, very small, but if we
were to connect two oppositely charged bodies, negative
and positive, with a good conductor, such as a metal wire,
electricity would flow for just an instant from one body
to the other. Electricity in motion, as this is, is called
current electricity, and this means nothing more than a
flow of electrons. This is the kind of electricity which
we use in ringing our doorbells, in running our motors,
and in lighting our homes.
Electric Cells. You may have heard the terms "dry
cell" and "wet cell," and doubtless some of you have
seen them in your
.pitch homes, as these
5anct two kinds of cells
are used to ring
electric doorbells.
The wet cell is
made by nearly
filling a quart jar
with a saturated
solution of ammo-
nium chloride. In
this jar a large
carbon plate and
a zinc rod are
suspended side by
side, but not touching each other. When the ends or
poles of these elements are joined with a wire electricity
results through the release of chemical energy. The zinc
rod and the ammonium chloride are gradually destroyed
and must be replaced from time to time.
mixture
In both the wet cell and the dry cell it is the chemical
action between the zinc and ammonium chloride that
produces the electric current. Why is the dry cell used
more than the wet cell ?
SOME WAYS OF PRODUCING ELECTRICITY 179
In the dry cell, the zinc used is placed on the outside
of the cell, making a container for the other materials,
while the carbon is a large rod in the center. Between
these are the chemicals, a paste of ammonium chloride
being placed next the zinc and a layer of manganese
dioxide around the carbon. The carbon pole is called
the positive (+) pole, while the zinc is called the negative
( — ) pole. A current of electricity will flow through a
wire which connects these poles. Dry cells have come
to replace the wet cells in our homes to a large extent
because they are more convenient to handle.
What Produces the Light in a Flashlight? When an
electric cell has been used for a long time, it may fail to
produce any more current. In the case of the wet cell,
you will very likely find that one of the plates in it has
been used up. This suggests that some vigorous chemical
action has taken place in the cell between the solution
and the plates. This is true. The cell is really a device
by which energy resulting from this chemical action in
the cell changed into electrical energy. This electrical
energy can be changed to heat energy and light energy
as it passes through the tiny bulb of the flashlight.
SELF-TESTING EXERCISE
Select from the following list those words which best fit the blank spaces
in the sentences below and arrange them in proper numerical order. A
word may be used more than once.
attract neutral ammonium conduction
silver brass nickel chemical
repel negative electrons insulators
nucleus silk line conductor
attracts friction gold metal
repels contact protons charge
positive induction wool current
copper electricity sodium cotton
Every (1) body contains equal amounts of (2) and
(3) electricity. (4) between two unlike substances as
180 HOW WE PRODUCE ELECTRICITY
sealing wax and wool will produce two unlike charges of (5)
The nucleus of every atom of matter contains positive particles
called (6) Around this (7) revolve. When glass is
rubbed with silk, (8) go from the glass to the silk, making the
glass (9) because of the excess of (10) in it and the silk
(11) because of the excess of (12) in it. Electrons (13)
electrons and protons (14) protons, but protons (15) elec-
trons. Current electricity is merely a flow of (16) along a
(17) (18) are materials which do not allow electricity
to pass readily. In electric cells, electricity results from an
expenditure of (19) energy. The common dry cell has two
plates, zinc and carbon, and the active chemical (20) chloride.
STORY TEST
WENDELL EXPERIMENTS AT HOME
Read carefully and critically. List all the errors and suggest corrections.
I know that friction produces heat, but I have been puzzled to
know why it is only in cold weather that I can get enough heat
by rubbing the fur on my cat's back to make sparks of fire. Last
night I rubbed a comb with flannel and the comb received elec-
trons from the flannel. I touched small bits of paper with the
comb. They clung to it at first but soon jumped off. Since they
were attracted at first I think they must have had a positive charge,
and when they jumped off we know they were positive because
they were repelled. A positive charge is easily produced by
rubbing glass with silk. The protons go into the glass, making it
positive. This morning I got a dry cell at the store. I connected
it through a button with wire to an electric bell. In connecting
to the battery I was careful to have the string or cloth covering
of the wire kept in place when I screwed the nuts over the wire on
the binding posts because if the bare wire touched them it would
make a short circuit and ruin the battery. When I pressed the
button the bell did not ring. This shows that the battery was old.
I shall take it back to the store and exchange it for a fresh battery.
THE REVIEW SUMMARY
In this unit we have only begun to find out some of the fact?
about electricity, therefore you will not be able to give all the
generalizations that you would give later on. See if you can add
any to the ones that follow :
SOME WAYS OF PRODUCING ELECTRICITY 181
1. There are only a few metals that can be magnetized or that
can be attracted by a magnet.
2. Electric charges can be given to bodies of matter. Non-
conducting bodies hold these charges for a time.
3. Electricity is believed to consist of negative particles called
electrons and positive particles called protons.
4. Electrical energy is produced only at the expense of some
other kind of energy.
Before making your review summary, test your knowledge of
the facts of the unit by checking over the text so as to be sure you
know the facts underlying the generalizations. Then, using the
generalizations, the material in the text, and everything you have
read, seen, or done yourself, make a summary outline for your
notebook. This outline you may use when you make a recitation.
TEST ON FUNDAMENTAL CONCEPTS
Make two vertical columns in your workbook. Head one CORRECT and
the other INCORRECT. Under the first place the numbers of all statements
you believe to be correct. Under the second place all the numbers of the
statements you believe to be incorrect. Your grade = right answers X 5.
I. When glass is rubbed with silk : (1) the silk takes a negative
charge and the glass a positive charge ; (2) the glass is electrified
but not the silk ; (3) the amount of electricity produced is the same
in both bodies ; (4) the glass and silk will repel each other.
II. Electricity may be produced by : (5) friction between paper
and cloth ; (6) putting rods of aluminum and iron into a salt solu-
tion and letting the outside ends touch each other ; (7) chemical
action in a storage battery ; (8) an electric motor.
III. Every magnet has: (9) two poles which attract iron;
(10) two unlike poles; (11) a magnetic field; (12) an electric
current surrounding it.
IV. A dry cell : (13) produces electricity from chemical energy;
(14) contains no water ; (15) has two poles, north and south ;
(16) produces no current on a closed circuit.
V. The needle of a magnetic compass: (17) is a temporary
magnet ; (18) points to the earth's geographic north pole ; (19) takes
the direction of the earth's lines of magnetic force ; (20) always
points in an east to west direction.
THOUGHT QUESTIONS
1. What are some objections to the use of the magnetic compass
to direct the course of a ship?
182
HOW WE PRODUCE ELECTRICITY
2. How can you take electrons away from a glass rod? How
can you add electrons to an insulated piece of metal?
3. Why does a person become charged with electricity when
scuffing over a carpet on a day when the air is dry?
4. Why is a spark sometimes produced when one rubs the cat's
fur backwards?
REPORTS ON OUTSIDE THINGS I HAVE READ, DONE,
OR SEEN
1. Report upon an article related to some topic discussed in
this unit. The article may be from a current number of a science
magazine or from some popular science book you have read.
2. The story of Galvani and Volta.
3. What Benjamin Franklin did for electricity.
4. The use of lightning rods.
5. The passing of the magnetic compass on ships.
SCIENCE RECREATION
1. THE OBEDIENT ARROW
Procure a dry fish globe. Cut a cover for it from cardboard.
Cut an arrow from stiff letter paper. Suspend the arrow, carefully
cctrctboarcC
balanced, in the middle of the
globe by a very fine thread.
Fasten to the center of the card-
board cover. Tell the arrow to
turn to the point on the jar
which you rub. Rub the outside
of the glass up and down at a
place about two inches to the
right or left of the place where
the arrow points, then rub another
Place a few inches away. Rub
your hand over the place elec-
trified if you wish to take the
electricity away and let the arrow go back to its original position.
2. A BALLOON WELCOME
Blow up a rubber balloon until it is about eight inches to ten
inches in diameter. Tie tightly. Suspend by a string about
three feet from the wall and nearly in the path of a person who
comes through the door into the room. It should be shoulder
high. On a day when the air is very dry (a cold winter day is best)
SOME WAYS OF PRODUCING ELECTRICITY 183
rub it briskly all over with a piece of fur or wool. Call some
people into the room and if they pass close to the balloon, they
will be surprised at the result.
3. MAKE AN ELECTROSCOPE
Fasten a piece of silk thread to a celluloid ping-pong ball or to
small pieces of cork. Hang this eight inches below a support.
Use this to see if objects like sealing wax, fountain pens, and combs
when rubbed with fur, wool, or silk are electrified.
4. A TASTE OF ELECTRICITY
Get a strip of copper and a strip of zinc about ^ inch wide and
two or three inches long. Fasten a copper wire to one end of each.
Touch the tongue with the two free ends of the copper wires.
Hold the ends of the wires not more than ^ inch apart. Dip the
ends of the metal strips (must not touch each other) into a salt
solution. Take off the copper wire, and bring the ends of the two
strips to the tongue quite near each other. Can you detect a
difference in taste when the current flows and when it does not?
5. ELECTRICITY FROM A LEMON
Use the zinc and copper strips in Demonstration 4. Cut two
slits in a lemon -|- inch apart. Work the knife around in each to
cut the tissue. Push the two strips of copper and zinc into the
slits but do not let them touch each other either inside or outside
the lemon. Test by taste to see if an electric current is produced.
Test with a compass.
SCIENCE CLUB ACTIVITIES
1. ELECTROSTATIC RACE
Make your preliminary tests at home. What can you find that
will give you the strongest electric charge — wax, comb, fountain
pen, rod of ebonite, hard rubber, or glass? Which gives you the
best results — wool, fur, or silk? When satisfied with your results,
enter your science club contest which will be held on a named
future date. Pieces of paper of graded sizes will be provided, and
the contest is to see whose equipment, which he brings from home,
can lift the largest piece of paper clear from the table.
2. A MAGNETIC BOAT
Build your boat upon any design you may devise. The fol-
lowing suggestions may be useful to you : For the magnet use a
184
HOW WE PRODUCE ELECTRICITY
darning needle, or a piece of watch spring about 3 inches long.
Make a paper boat about 4 inches long. Paraffin the outside
and seams if made from
magnetic, boat float- . ,-, ,, (-111
pieces rather than folded.
After magnetizing the
steel, lay it in the boat
and cover with a thin
layer of melted paraffin.
Two such magnets may
be used if desired. On
the club race day have a
tub of water. Anchor 3
or 4 cork floats to mark
off the course. Boats
must go around the course
outside these floats. The
same magnet is to be used
by each contestant. This
should have a wire exten-
sion so that the magnet
can never be brought
nearer than 6 inches to the boat. A stop watch is needed to time
each boat, because each boat must be
taken around the course by itself. The
winner will be the one that makes it in
the shortest time.
3. How TO PRODUCE A MAGNET USING
ELECTRICITY
(A) Connect a cell and push button
as shown in diagram. Bring a portion
of the wire down over and parallel to the
compass needle. Press the button to
cause an electric current to flow through
the wire. Result ?
(B) Diagram B represents a wire
brought down over and parallel to the
compass needle. Complete the wiring
connections so that when the current
flows it will make the north pole of the
needle turn towards the west, as is rep-
resented by the dotted arrow.
(C) Wind an insulated copper wire
in close layers around a soft iron rod,
remove the rod, connect the ends of the
H button
lie-
B
SOME WAYS OF PRODUCING ELECTRICITY 185
coil into the electric circuit. Hold one end of the coil near the north
pole of the compass needle. Press the button to pass an electric cur-
rent. Result ? Hold the other end of the coil near the north end of
the compass. Result? Make a similar test with the iron core inside
the coil. Compare strength of magnetism. Complete diagram C.
Label poles of the electromagnet correctly.
REFERENCE READING
Lunt, J. R., Everyday Electricity. Macmillan, 1927.
Meister, M., Magnetism and Electricity. Scribner's, 1929.
Parker, B. M., The Book of Electricity. Houghton, Mifflin, 1928.
Wade, H. T., Everyday Electricity. Little, Brown & Co., 1924.
SURVEY QUESTIONS
Have you ever tried to count the
stars? How many can you
name?
What is the Milky Way?
Why is the North Star so called?
Are stars all the same color ? What
do the differences in color mean ?
What is a constellation?
What is the astronomer's "yard-
stick"?
Are all stars the same distance
away?
UNIT VIII
GETTING ACQUAINTED WITH THE
STARS
PREVIEW
We have looked into the sky on a dark clear night and
have seen multitudes of twinkling stars, some large and
some small. If we look closely, we notice that some of the
stars are of a different color, some bright red, deep blue,
or white. Boys and girls who are scouts can pick out
the North Star and some of the easier constellations.
Doubtless boys and girls during the past ages have done
the same thing. They have wondered about the stars
and how far away they were. The ancients thought the
sky was an inverted bowl and that the stars were holes
through which light shone. Primitive man worshiped
light because he was so much dependent on it. Ancient
people studied the stars and used them as guides to help
find their way about at night. It is little wonder that the
ancients with so much leisure time should find the heavens
interesting. Shepherds who watched the flocks by day
also watched the stars by night. It is not strange that
these imaginative and superstitious people of the olden
times saw figures of people and animals in the stars, and
created stories about their origin in the sky. Nor is it
strange that they made a universe with the earth as a
center, and believed that the stars in the heavens revolved
around it. They knew that the sun and the moon and
the stars helped them to keep time, and they also came,
in time, to be more familiar with some stars than with
187
NICHOLAS COPERNICUS, 1473-1543.
COPERNICUS, as a Polish boy, studied Latin, Greek, and mathe-
^-^ matics. It was believed at that time by every one that the
earth was an immovable body suspended in space, and that the sun,
planets, and stars moved around it. The lad studied medicine but
was so interested in mathematics and astronomy that when an
opportunity arose he became a professor. Later he became a canon,
or priest, at the Cathedral of Frauenburg, in Germany. Here he
had much leisure and devoted himself to the study of astronomy.
Although he had no telescope, he cut slits in the walls of his home
and timed the movements of the planets in that way. He came to
the conclusion that the sun was the center of our solar system and
that the earth and other planets revolved around it. This was a
theory then, but we know it to be a fact today.
HOW FAR AWAY ARE THE STARS? 189
others. Some of the better informed men became astrol-
ogers. These men believed that the stars exercised magic
influence over people, and that such people must do the
things that the stars ordered them to do. Even today
we see ignorant people believing in the predictions of
fortune tellers who say that they live under a lucky or an
unlucky star. Some of our superstitions of today have
been handed down from very ancient times.
But the early astrologers knew a great deal about some
of the stars. They could tell several planets and gave
them names. The name " planet" itself comes from the
Greek word meaning to wander, for they saw that these
heavenly bodies moved about. The old astronomers
could predict with a good deal of accuracy the movement
of some stars, although they did not know what caused
them to be seen in different positions in the sky. The
old idea was that the earth was fixed, and it was not until
the 16th century that Copernicus,1 a Polish clergyman,
proved that a number of planets were revolving in space
around the sun. He believed our own earth was one of
these and that the earth rotated on its axis, making it
appear as if the stars moved about the earth. In the
units that follow, we shall build on the experiences we
have had in our geography and try to get a little more
knowledge about some of our neighbors in space.
PROBLEM I. HOW FAR AWAY ARE THE STARS?
When we look up into the sky, we may think that we
see myriads of stars, but if we try to count them, we are
surprised to find that we rarely see more than 2000 or
3000 at one time. If we were to look through a big tele-
scope, such as they have at the Mount Wilson Observatory
in California, we could see thousands of stars where we
saw only one with the naked eye. This is so because the
1 Copernicus (ko-pur'ni-kws).
190 GETTING ACQUAINTED WITH THE STARS
telescope shows us bodies whose light is too dim to be seen
with the unaided eye. But if we were to expose a photo-
graphic plate behind a telescope lens for several hours
under the same space in the sky, we would be amazed
to find when the plate is developed that not thousands
but hundreds of thousands of stars will appear where we
saw only a few with our naked eye. The reason for this
is that the chemicals on the plate are sensitive to rays
of light too weak to register in the human eye, even when
we look through the telescope.
The Astronomer's Yardstick. When we look up at
the stars, we realize that some are much larger and some
much brighter than others, but all look to be very far
away. As a matter of fact, some are very much farther
away than others. Some appear nearer because they
are more brilliant. Astronomers tell us that the nearest
fixed star 1 is over 25,000,000,000,000 miles away. Light
travels a little over 186,000 miles a second. In a year
Solbelman Syndicate
This shows a portion of the sky as seen through a large telescope. How many
of these stars do you think you could see with the naked eye ?
1 Proxima Centauri.
HOW FAR AWAY ARE THE STARS? 191
The light by which we see Aldebaran today left that star 44 years ago, and we
apparently see it as the upper star. But in that time the star has moved many
miles and it is really at a point 55 billion miles away from the place where we
appear to see it.
it travels about 6,000,000,000,000 miles, so that it takes
a little over 4 years for light from the nearest star to reach
us. The distance light travels in one year is called a
light year. This is the astronomer's yardstick or a way
of measuring distances. When the astronomer tells
us that there are probably many hundred thousands of
light years separating us from some of the more distant
stars, we can see that the distance of the stars from the
earth varies greatly.
Distances to the Stars Are Enormous. There have
been many comparisons devised to make the enormous
distances to the stars understood. None of them help
very much, but that of Dr. Brashear, at one time a famous
lens maker of Pittsburgh, is at least interesting. In the
eyepiece of many telescopes a "cross hair" is used. This
had to be finer than any thread. Even the fiber of the
ordinary spider web is too coarse, but the mother spider
spins a very fine and delicate fiber to make the cocoon
which protects the young. These fibers were used by
Dr. Brashear in his telescope, and he became interested
in calculating how far so thin a fiber could reach. A pound
of it would circle the earth at the equator and ten pounds
would make enough fiber to reach the moon. How much
of this fine fiber would be required to go to the nearest
star 4£ light years away? By Dr. Brashear's calculation
192 GETTING ACQUAINTED WITH THE STARS
By Burton Holmes. From Ewing Galloway
Here, in the Court of Honor in front of the science building, light from Arcturus,
which had left the star forty years ago, set off the lights of the Century of
Progress. The illuminated board which secured the starlight from one of the
co-operating observatories is seen in the center of the picture.
it would require 500,000 tons to reach the nearest star,
and to reach the North Star, it would take over 55,000,000
tons.
How Starlight Opened the Century of Progress Exposi-
tion. In 1933 the World's Fair in Chicago was opened
officially by an electric current set up by light from the
star Arcturus. The light from this star, which reached
the earth in 1933, left Arcturus 40 years earlier, or about
the same time that the previous World's Fair had been
held in Chicago. It is interesting to know how this
starlight was used. Light from the star was collected
by a large telescope and focused on the interior of a
photoelectric cell. Photoelectric cells are capable of
transforming light energy into electrical energy, and this
cell transformed the light from Arcturus into a current
of electricity which was amplified and sent by wire from
HOW FAR AWAY ARE THE STARS?
193
the observatory to Chicago. Here it operated machinery
which turned on the lights and opened the Fair. Each
night the great batteries of electric lights at the Century
of Progress Exposition were turned on by means of the
light from this same star sent from one or more of the
observatories which co-operated in this interesting service.
If the distance to Arcturus were expressed in miles, it
would be about forty times six million million. Can
you express this in figures ?
Star Magnitudes. Any one who has seen the heavens on
a clear night knows that the brightness of the stars varies
greatly. The faintest star visible to the unaided eye is
called a sixth magnitude star. This furnishes the basis
of classifying them. The table which follows gives a
rough comparison of magnitudes or brightness.
MAGNITUDE
TIMES BRIGHTNESS OF
SIXTH MAGNITUDE
STARS
APPROXIMATE NUMBER OF
STARS OF THIS MAGNITUDE
IN THE WHOLE HEAVENS
6
1
5000
5
2i
1500
4
6
500
3
16
200
2
40
60
1
100
20
The apparent brightness of a star depends upon its
temperature, size, and distance. Other things being
equal, the nearer the star to us, the brighter it seems.
The North Star is about as bright as Betelgeuse, but it
appears much dimmer because it is more than twice as
far away from us, and yet it appears brighter than some
nearer stars which are smaller and cooler.
What the Color of Stars Tells Us. The unaided eye can
easily notice a difference in color of some of the stars.
When an iron rod is heated in the furnace, the first
H. & W. SCI. I — 14
194 GETTING ACQUAINTED WITH THE STARS
Wright Pierce
This picture shows how the spectroscope is used. By means of this instrument
the materials burned in the flame at the right are known by the patterns or bands
they make in the spectrum of the instrument.
indication of its becoming luminous is shown by a dull red
color, which, as it is heated longer, may change to orange
or yellow. If it is placed in a very hot furnace, it finally
becomes " white hot" and gives a brilliant whitish light.
Evidently, then, the color of a luminous body differs
with its temperature. This experiment gives us some
evidence on the temperature of stars. Our sun is believed
to have a surface temperature of about 11,000° F., and
gives a yellowish light. Some stars have exactly the
same color as the sun, and when seen through an instru-
ment called the spectroscope, they have the same spectrum
as the sun and so are believed to have about the same
temperature as the sun. Betelgeuse is a red star and
hence is not as hot as our sun, while Sirius, the Dog Star,
shines with a bluish-white light which indicates that it is
hotter than the sun. Half of the stars are white, while
most of the others are yellow. Some bodies that were
HOW FAR AWAY ARE THE STARS? 195
stars once now have so little light and heat that they do
not even glow. They have become cold bodies like our
earth and our moon. The color band and its position as
seen in the spectroscope help astronomers to tell whether
the star is moving away from us or coming toward us.
SELF-TESTING EXERCISE
Select from the following list the words that best fill the blank spaces in
the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
million years red color
tenth month black photography
first century white periscope
thousand Heavens light telescope
100 orange dark sixth
year yellow stars fourth
More stars in the (1) are discerned by (2) than can be
seen through a (3) (4) . travels faster than any other
known thing. In astronomy the unit of measure for distance is
the (5) (6) , which equals six (7) (8) miles. The
nearest star is about 4^ (9) (10) away. The faintest
star we can see is a (11) magnitude star. A first magnitude
star is (12) times as bright as this. The age of a star is told
by its (13) Young stars are (14) , while old stars are
(15) or (16)
STORY TEST
URSULA VISITS A GREAT OBSERVATORY
Read carefully and critically. List all the errors and suggest corrections.
I recently enjoyed a rare privilege. It was open night at the
Harvard Astronomical Observatory. Through a 10 in. tele-
scope I saw the red Rigel and red Mars. Rigel is ever and ever
so much hotter than our sun and the other stars. As I looked at
it I could feel the intense heat coming through the telescope, and
no wonder, because it is 25,000 times as hot as the sun. I asked if
I might see the astronomer's "yard stick" with which they meas-
ured the distance to the stars. I wonder why they laughed, but
anyway they said that they never let the public see it. On one
of the roofs without any telescope we were shown constellations
196 GETTING ACQUAINTED WITH THE STARS
made up of stars of varying brightness. We could see stars varying
from the 1st to the 10th magnitude. I must have counted at least
30 first magnitude stars, the brightest of them all was Betelgeuse.
PROBLEM II. WHY DO THE STARS APPEAR TO MOVE?
The Earth Is Moving through Space. We must go back
to our geography to answer this question. The earth is a
nearly spherical body which rotates on its axis once in every
24 hours. We also know that it revolves around the sun
once every year. If we think of the size of the earth and
remember that it is about 25,000 miles in circumference
at the equator, we may imagine a city there whirling
around the earth's center at a rate many times as fast as
the fastest mail plane can travel. If we bear in mind
the rotation of the earth on its axis, we can understand
The fact that the earth is revolving is shown in this photograph. The fixed stars
make trails on the plate. Can you locate the position of the polar star ? In what
hemisphere must this photograph have been taken ?
WHY DO THE STARS APPEAR TO MOVE? 197
why it is that the sun, moon, and stars appear to rise
and set. The earth also rushes through space around the
sun at a rate of about 1100 miles a minute. If we also
remember that we are moving rapidly through space, we
can see why constellations do not always appear to be in
the same place in the heavens. Those of us who are
scouts know that certain groups of stars called constella-
tions are visible in the winter and that six months later
others have come above the horizon and occupy the places
held by those we saw in the winter. The reason for this
is evident when we recollect that in the summer our
earth is in quite a different place in space than it is in
winter. We have moved along to the other side of the
sun in a circular path whose diameter is 186,000,000 miles.
Demonstration 1. How the Rotation of the Earth Causes Stars to
Appear to Move.
Hang a large round umbrella in the room so that the supporting
rod is in direct line pointing to the North Star. A compass will
show you north. There are 90° from the equator to the north
GETTING ACQUAINTED WITH THE STARS
pole. Paste a paper star around the umbrella rod where it passes
through the cover of the umbrella. As you look up into the
umbrella, you see this star where the North Star would be. Place
other paper stars in positions to represent the Big Dipper and one
or two other constellations. Make holes at the poles of a small
globe, place it on the umbrella rod so that it will rotate under the
umbrella. The North Star is now directly in line with the axis
of the earth represented by the rod of the umbrella. In place of
a globe, a ball, an apple, or an orange may be used. The latitude
of the place where you live equals the number of degrees it is north
of the equator. Mark the spot on the globe where you live. Now
imagine you are on the earth. Hold the umbrella still. Rotate
the globe and observe the direction in which you would look to see
the North Star at different times. Observe the direction in which
you see the end star in the Big Dipper. Rotate the globe from
west to east far enough to represent six hours' time, or one-fourth
of a revolution. Now observe the direction in which you would
look to see the same star. In what direction would the star appear
to have moved?
Why Do Stars Rise and Set ? Suppose we are standing
at a certain place on the surface of the earth as it rotates
on its axis. After a complete revolution on its axis during
a period of 24 hours, we are brought back to the same
place. This turning as we look at the stars gives them
the appearance of rising and setting. If you walk up a
Explain by means of this diagram why stars appear to rise and set.
long hill behind which is a factory with a tall chimney,
the higher up the slope you go, the more you see of the
chimney. It appears to rise. If you go backwards down
the hill, you see the chimney gradually disappearing be-
WHY DO THE STARS APPEAR TO MOVE? 199
hind the hill. We may think of it as setting. When
the moon comes up or sets, it just means that we have
traveled past it as we dash by objects on a railroad train.
It is in the same way that we move past stars of the
constellations. Stars seem to move across the sky from
east to west, but the earth is really rotating from west
to east. Consequently they appear to rise and set.
There is one star, however, that does not appear to move.
This is Polaris, the North Star. The reason for this is
that it is in line with the axis of the earth, as is shown in
the demonstration we just performed. Now, because the
earth rotates, the stars appear to describe circles around
the earth. If the earth is held still while the umbrella
is rotated east to west, and you imagine yourself at a
fixed spot on the earth, you will readily see the apparent
motion of the stars.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
always north move spherical
never south motion earth
hallucination east movement star
illusion west rotates equator
near sun speeds axis
distant moon revolves poles
latitude
The earth in form is a (1) body. It (2) on its (3)
and (4) around the (5) The axis of the earth points
towards the (6) (7) which (8) appears to move. All
the other stars appear to (9) from (10) to (11) during
the night. But this (12) is really due to the (13) of the
(14) The fact that we do not see the same stars at different
seasons is explained by the (15) of the earth to (16) parts
of the heavens as it revolves around the sun.
200 GETTING ACQUAINTED WITH THE STARS
STORY TEST
SYBIL HAS A UNIQUE WAY OF EXPLAINING WHY THE STARS
APPEAR TO MOVE
Read car ef ally and critically. List all the errors and suggest corrections.
I play that I am the earth and my eye is a person on the earth.
I stand near one end of the room. I name different objects in the
room " stars." Directly over my head is the North Star. Un-
fortunately my eye does not extend out from the surface of my face
as people stand out above the surface of the earth, and so my eye
cannot see the North Star. I play it is sunset in September. I
rotate slowly. When halfway around it is sunrise and the night is
over. The objects representing stars passed before my sight just
as if they had been moving and I had been still. I then move
to the opposite end of the room. It is now sunrise in March.
I rotate halfway to represent the night. I see some of the stars
(objects) that I saw before and some different ones. But the
positions in which I see them appear quite different. After this
experiment it is quite easy to understand how the two movements
of the earth can produce the common illusions of the movements
of the stars.
PROBLEM III. HOW TO GET ACQUAINTED
WITH THE CONSTELLATIONS
If you live in the northern hemisphere and look towards
the north on any clear night, you will find the Big Dipper.
The two stars on the side of the dipper away from the
handle are called "the pointers.7' If you use these for
direction and follow this line from the bottom of the dipper
into space, you will presently come to a star not quite so
bright as those forming the bowl of the dipper. This is
Polaris, the polar or North Star. It is the star that has
guided travelers since ancient times. When we see it, we
should remember that the light which enters our eyes is
believed to have left that star more than 450 years ago.
The light by which you see the North Star left it before
Columbus, guided by that same star, discovered America.
That starlight has been traveling at the rate of 6,000,000,-
000,000 miles a year all these long years. Since the North
HOW TO GET ACQUAINTED WITH CONSTELLATIONS 201
Star is practically in line with the axis of the earth and all
other stars keep the same relative position to the North
Star, there is ap-
parent rotation of
all the other stars
about Polaris in
the center.
How the Stars
Got Their Names.
Many boy and girl
scouts may have
studied the stars
enough to know the
names of some of
the constellations.
Ancient peoples in
their study of the
i ^ „ Star map of the region about the North Star (pole
heavens saw many star)> If you face north at 8 PM and hold this map
Wonderful Crea- in front of you with the name of the present month at
+IIT-OG tViorP rlrao- the bottom, you will find these five constellations in
ie, i i d&- the relatiye positions indicated on the map.
ons, horses, lions,
dogs, as well as many mythological characters. These
groups of stars have been called constellations. There
are 48 constellations named by ancients and about 40
more have been added in later times. Some are called by
very ordinary names such as the Big Dipper and the
Little Dipper, which you have all seen. But these same
constellations have also been given other names, the
Great Bear and the Little Bear. Many of the star groups
have Greek or Roman names which have come down from
the ancient times because of the stories that the ancient
peoples told about these figures in the sky. It is interesting
to know that certain constellations known to the Egyptians,
Chinese, the Greeks, and our American Indians had the
same names given them by these different peoples. For
202 GETTING ACQUAINTED WITH THE STARS
example, the constellation we call the Great Bear was so
named by the Chaldeans, Greeks, and American Indians :
Is this a modern or an ancient map of a portion of the heavens ? Give the reason
for your answer.
groups of people who had no connection with each other
at any time during their existence.
The Big Dipper. One of the most conspicuous star
groups or constellations is the Big Dipper. From it you
can find the North Star and then work out to other groups.
Polaris, also a second-magnitude star, is at the end of the
handle of the Little Dipper. The two second-magnitude
stars in the end of the bowl away from the handle are
HOW TO GET ACQUAINTED WITH CONSTELLATIONS 203
called " pointers." They point to the polar star, Polaris.
The position of these and other constellations differs with
the season. As the earth moves along its orbit to new
positions in the heavens, the stars overhead at 8 P.M. will
vary greatly at different times of the year. If you observe
the Big Dipper in early evening as soon as visible, and
again the same evening three or four hours later, you can
see that its position in the heavens changes.
How to Tell Some of the Constellations. We can
easily find a number of the constellations if we know the
position of the Big Dipper and the Little Dipper. A
study of any good star map will show you that if you
follow the pointer of the Big Dipper to the North Star
and then continue about an equal distance beyond,
you will see a little to the right a constellation whose
bright stars roughly form the letter W. This is the
constellation Cassiopeia. If you go from the pointer
to Polaris and turn at right angles and travel nearly twice
the distance, you will come to a very bright red star, called
Capella. From the pointer at the open end of the bowl
draw a straight line to the handle side of the bowl one-
third of the distance down from the rim of the bowl and
continue in the same direction to a bright star which
is twice as far from the North Star as the bowl of the
Dipper is. This is Arcturus in the constellation Bootes.
Arcturus is a first-magnitude star 500 times as large as our
sun and gives a white light. We have already seen that it
takes about 40 years for its light to reach the earth.
By studying the star maps shown on pages 204 and 205,
you can locate a number of the more common constella-
tions such as Orion, with its three-starred belt, and the
bright stars Rigel and Betelgeuse ; the Twins ; the Great
Dog Star, Sirius, which is the brightest star in the sky;
and many others. Remember that the maps made for
use here show you the situation in the sky during the
JANUARY
FEBRUARY
204
JUL.V
AUGUST
NOVEMBER.
SEPTEMBER
DECEMBER
205
206 GETTING ACQUAINTED WITH THE STARS
months of November, January, March, and June in the
northern hemisphere, and that if you see the same heavens
six months from these dates, the constellations will have
quite a different position in the the sky, as can be seen by
comparing the maps on pages 204 and 205.
What Is the Milky Way? If you look up into the sky
on a clear moonless night, you will see an irregular belt-like
luminous cloud extending clear across the sky which varies
in brightness in different places. It seems like a pathway
in the heavens, and for this reason has been called the
Milky Way. This is best seen in September. In ancient
times the Milky Way was thought of as a pathway to
heaven over which those who died had to travel. It has
also been called by such names as Jacob's Ladder and the
Pathway of the Souls. Of late years our powerful tele-
scopes have revealed much more about the true nature of
the Milky Way. It is made up of millions of stars, masses
of incandescent matter, and perhaps bodies like our planets,
moons, and material out of which comets are made. All
the stars that we see through telescopes are luminous
bodies like our own sun. This great system of stars that
we see in the Milky Way is called a galaxy, and since
our own sun is a member of this galaxy, we belong to it
also. Many other galaxies have been discovered in the
very distant heavens, of which we will learn something
later.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
earth north Big first handle cloud
northwest south Little second bowl Polaris
sun east medium third dipper Cassiopeia
stars west Great thousands trillions pointers
planets up Small millions northeast constellation
galaxy down magnitude billions fourth luminous
HOW TO GET ACQUAINTED WITH CONSTELLATIONS 207
The two second (1) stars on the side of the (2) (3)
opposite the handle are called the (4) They show the direc-
tion to (5) Almost opposite the Big Dipper on the other
side of the North Star is the (6) called (7) Polaris is
the star at the end of the (8) of the (9) (10) If the
handle to the Big Dipper points southeast at 6 P.M., it will point
(11) at 9 P.M. and (12) . at 12 midnight. Polaris is a
(13) magnitude star and Sirius and Arcturus are (14)
magnitude stars. The Milky Way seems like a (15) (16)
but in reality is chiefly a cluster composed of (17) of (18) .
and is called a (19) of which our own (20) is a member.
STORY TEST
EVELYN LIKES TO STUDY THE STARS. HAS SHE PROFITED
BY HER STUDY?
Read carefully and critically. List all the errors and suggest cor-
rections.
The heavens are just full of stars grouped together in consterna-
tions. The largest of these is the Milky Way. Last night I saw
Orion. I recognized it by the 3-star belt and the 2 bright stars,
Altair and Arcturus. I also saw Procyon in the Little Bear, and
the brightest of all stars, Sirius, in the Great Bear. In the early
evening the pointers in the Big Dipper pointed northwest and
towards Polaris, but six hours later they pointed northeast and
away from Polaris. Cassiopeia appears to travel a complete circle
around the North Star every 12 hours, but stars farther from the
polar star like Sirius require 24 hours to make the circuit because
of the greater distance the star has to travel. If we stood over the
north pole in winter, Polaris would be directly overhead, but in
summer it would be 23^ degrees farther south.
THE REVIEW SUMMARY
We might study astronomy all our life and still know very little
about the stars. However, scientists have agreed that there are a
few general facts or generalizations that almost any one can learn
about these wonderful neighbors of ours in space. These gen-
eralizations are :
208 GETTING ACQUAINTED WITH THE STARS
1. There are many more stars than we can see.
2. The stars are so far away it takes light from them many
years to reach us.
3. The rotation of the earth on its axis causes an apparent daily
rotation of the stars.
4. Stars vary greatly in size, brightness, and distance.
5. All the stars we ever see with the unaided eye make up a
small part of a huge group called a galaxy.
Before making your review summary, test your knowledge of
the facts of the unit by checking over the text so as to be sure you
know the facts underlying the generalizations. Then, using the
generalizations, the material in the text, and everything you have
read, seen, or done yourself, make a summary outline for your
notebook. This outline you may use when you make a recitation.
TEST ON FUNDAMENTAL CONCEPTS
Make two vertical columns in your workbook. Head one CORRECT
and the other INCORRECT. Under the first place the numbers of all state-
ments you believe to be correct. Under the second place all the numbers
of the statements you believe to be incorrect. Your grade = right answer
X2i
I. The process which discloses the largest number of stars is :
(1) counting them on a very clear night ; (2) looking through a
powerful telescope ; (3) by photography ; (4) by using an enlarging
camera.
II. By the magnitude of a star is meant : (5) its distance away ;
(6) its size ; (7) its apparent brightness ; (8) its real brightness
compared to the sun.
III. When a star gives a white or bluish white color, it is evidence
that the star is : (9) very hot ; (10) very near ; (11) a young star ;
(12) hot, but not so hot as our sun.
IV. The stars in the sky: (13) keep their positions almost
unchanged year after year; (14) really move across the sky daily ;
(15) would not appear to move if the earth were still; (16) con-
stantly change their relative positions as do the drops of water
in the ocean.
V. The Big Dipper: (17) is a galaxy; (18) contains "the
pointers" for locating Polaris; (19) revolves around the sun;
(20) appears to revolve around the North Star every 24 hours.
VI. There are stars so far away that: (21) their discovery
awaits the building of more powerful telescopes ; (22) the light
leaving them today will not reach the earth for a hundred thousand
HOW TO GET ACQUAINTED WITH CONSTELLATIONS 209
years; (23) follow different physical laws from those of our own
system ; (24) they must be cold bodies.
VII. When we look into the sky at 8 P.M. in December, we do not
see the same constellations that we do at 8 P.M. in June because :
(25) it is colder weather ; (26) the nights are longer ; (27) the
earth has moved halfway around the sun, changing the heavens
which we see at night ; (28) the stars have rotated halfway around
the North Star.
VIII. The North Star is : (29) about vertically over the north
pole of the earth ; (30) visible to all people on the earth, because
of its great distance above the earth; (31) more than two million
billion miles from the earth ; (32) also called the Little Bear.
IX. The light year is : (33) the time it takes light to come to
earth from the sun ; (34) the unit of measuring distances of
heavenly bodies ; (35) the distance light travels in a year ; (36) about
six million million miles.
X. The Milky Way is: (37) a constellation; (38) a galaxy;
(39) a solid heavenly body ; (40) is seen by reflected light just as
the moon is.
THOUGHT QUESTIONS
1. Why do stars appear to move in a certain direction during
the night ?
2. Why do certain stars appear to change their positions from
month to month?
3. Calculate how long it will take the light from a star selected
by yourself to reach the earth ?
4. Compare an atom of matter and our own solar system.
Show how you will use facts, theories, and imagination in making
this comparison.
5. How would you say that future discoveries in astronomy
will be made ?
6. How can we tell the age of a given star?
7. We say that the axis of the earth points very nearly towards
the North Star. Can you explain how, in reality, this statement
is very far from the actual fact ?
REPORTS ON OUTSIDE THINGS THAT I HAVE READ,
DONE, OR SEEN
1. Report upon an article related to some topic discussed in
this unit. The article may be from a current number of a science
magazine or from some popular science book you have read.
H. & w. sci. i — 15
210 GETTING ACQUAINTED WITH THE STARS
2. The value of Galileo's telescope.
3. Ideas of ancient peoples about the heavens.
4. Kinds of telescopes.
5. Famous observatories.
SCIENCE RECREATION
1. WHAT PROGRESS HAS SCIENCE MADE ON THE EARTH SINCE THE
BEAM OF LIGHT BY WHICH You MAY SEE ARCTURUS LEFT IT?
Ask your grandparents about the wonders of science 40 years
ago. Write up the story of scientific progress that has been made
on the earth during the time that beam of light traveled through
space.
2. MAKE A LUMINOUS STAR CHART.
Fit a box approximately four inches on a side over the end of a
hand flash lamp. The side of the box opposite the lamp bulb is
open to hold the star charts. These are cut out of black paper
a trifle larger than the opening in the box. The center of the
box cover is cut out nearly to the edge. When this is put on the
box over the star chart, it will hold it securely in place. Consult
a good star map. Mark on the black paper the relative positions
of the principal stars in a constellation. Prick holes through.
When in place on the box, the light shines through and shows
you just what to look for in the sky. Make as many constellation
charts on separate sheets of paper as you desire to locate. The
following constellations are suggested as interesting groups to
locate : The two dippers, Cassiopeia, Orion, the Northern Cross,
Pegasus, Sickle, Lyra, and the Pleiades (Seven Sisters).
SCIENCE CLUB ACTIVITIES
1. MAKING STAR TRAILS
Have the club meet in the evening. If in the city, get permis-
sion to use the roof of some tall building, but it is better to go out
into the country where no artificial lights will cast a haze, and so
dim the light of the stars. Have at least two cameras loaded with
very fast film, such as supersensitive phenachrome. Open the
diaphragms wide, and set the lever for time exposures. Point
one camera directly at Polaris and the other at the brightest star
nearly overhead. Fix the cameras so that they cannot move.
Open the shutters and allow them to stay open one and one-half
to two hours. You can go away and have an indoor meeting and
HOW TO GET ACQUAINTED WITH CONSTELLATIONS 211
make a luminous star chart, or study the star groups with your
chart, if you have one already made. When your film has been
developed and printed, you will find curved paths circling part
way around the polar star but nearly straight paths in the picture
taken overhead. You should be able to explain why these trails
are not alike.
2. WHAT Is YOUR SPEED AND WHERE ARE You GOING?
In addition to considering and making the calculations sug-
gested here, ask members to look up and report to the club any
information — facts or theories — that has to do with our move-
ments in space.
a. If you were at the equator, how far would the rotation of the
earth on its axis carry you in twenty-four hours?
6. If you were right over the North Pole of the earth, how far
would the rotation of the earth carry you in twenty-four hours ?
c. If you live about halfway from the North Pole to the equator,
how far will you travel in twenty-four hours?
d. If you are moving at the rate of eighteen and one-half miles
per second, along the orbit of the earth around the sun, how many
miles do you travel in a day of twenty-four hours ?
3. Make a star map for the present month.
4. Make a simple telescope.
5. Report on the beginnings of astronomy.
6. Report on a modern astronomical observatory.
REFERENCE READING
Baker, R. H., The Universe Unfolding, Williams and Wilkins, 1932.
Barton, S. G., and Barton, W. H., A Guide to the Constellations. Mc-
Graw-Hill, 1928.
Book of Popular Science. Universe, page 453 ; Motion, page 871 ;
Worlds, page 1305 ; Star Land, page 4167 ; Milky Way, page 4767.
Chant, C. A., Our Wonderful Universe. World Book, 1929.
Moseley, E. L., Other Worlds. Appleton-Century, 1933.
Washburne, H., and Reed, F., The Story of Earth and Sky. Appleton-
Century, 1933.
SURVEY QUESTIONS
If the earth was once all molten
rock, how can you account for the
soil and water now formed on its
surface ?
Did you ever find a fossil ? How do
you think it was made ?
What are some evidences of the
force of water ?
How are the active forces of nature
of vital importance to a farmer?
Do you know what kinds of soil hold
water ? What kinds are porous ?
What kinds make the best soil for
growing crops ?
Wliy are fertilizers added to soil?
Photo by E. S. Shipp. Courtesy U. S. Forest Service
UNIT IX
ROCKS AND SOIL
PREVIEW
How many of you have ever been to the top of a high
mountain ? You remember how it looked — a great
mass of solid rock with perhaps a few trees clinging here
and there in places where there was a little soil. If you
worked your way down the mountainside, you would
probably follow the course of a tiny brook which, as you
descended, you would notice had cut its way deeper and
deeper between rocky walls and slopes of broken particles
of rock. Look at those rocks carefully. They all seem
to be angular bits, not rounded like the pebbles you find
in the valley at the foot of the mountain or on the beach.
The rocks on the mountainside look as though they might
have been cracked off and broken up by some force,
perhaps great heat or cold. Let us scramble down a lit-
tle lower. Trees, shrubs, and plants begin to be more
numerous, the rocks are giving place to soil, some of it
black and rich. You find more inhabitants of the forest
- birds, squirrels, and other small animals. If you dig
in the ground, you may find earthworms, beetle larvae,
and other living things. The brook is inhabited, too :
insect larvae in the water, flies and mosquitoes hovering
over its surface, and perhaps small fish, even trout, lurking
in its pools. And now the rocks and pebbles over which
the brook rushes show the familiar rounded look of those
stones which we know were polished by the action of
water. At the foot of the mountain we may find the
213
214
ROCKS AND SOIL
forests giving place to fertile farms instead of rocky
slopes.
The story of soil making goes back a long, long way
into the past history of the earth. We must look back
millions upon millions
of years to an earth
with no life, no soil,
nothing but water
and masses of rock.
It would be too long
a story to tell how
all the different kinds
of rocks were formed,
for soil was made
gradually from the
rocks. Frost and
heat chipped the
rocks, winds blew
particles against
them, glaciers gouged
them out and de-
posited the ground-
\\Tigntfierce j. . ,-.
A mountain stream. Why are the rocks rounded ? UP Sediment in the
streams formed from
their melting ice. Streams of water tore their way
down mountainsides and ground up particles of rock as
they went. All these forces slowly but effectively did
their work and helped make the first soil. Then after
plants appeared on the earth, their dead bodies decayed
and went to help form soil. Thus two kinds of soil
could be found : that made from the original rocks
and that containing the decayed bodies of plants and
animals.
But under the layers of humus or decayed organic
matter and the various layers of loam, clay, or gravel, we
THE STORY TOLD BY FOSSILS
215
come at last to bed rock, the material out of which the
original soil was made. All of these changes on the earth
have taken a very long time. Nature works slowly,
but Nature is always working. Everywhere the forces
of running water, the wind, ice, heat, and cold, are at work
changing the rocks into soil, just as they have been at
work in past ages. The earth's surface is constantly
changing, and some of the changes take place within our
own life span.
One very interesting evidence of these changes on the
earth comes from the story told by fossils, or remains of
former life found imbedded in some rocks. Not only do
these remains show us that very different plants and
animals once lived on the earth, but they also show us
that great changes in life have been brought about through
the changes in climate and the alteration of the earth's
surface. The purpose of this unit is to tell the story of
Wright Pierce
Which of these pebbles was taken from the brook? Which from rocks on the
mountainside ?
how the earth became a place fit for living things to grow
on, how the living things have changed, and how and why
the earth has become fitted for life today.
216 ROCKS AND SOIL
The great mass of rock below the mountain jutting out into the forest is a lava flow
Once it was molten lava, now it forms what kind of rock ?
PROBLEM I. HOW WERE THE ROCKS FORMED?
Three Ways in Which Rocks Were Formed. Let us go
out into the field to answer this question. You will find,
depending upon where you happen to look, various kinds
of rock. Rocks of one kind appear to be made up of
pieces of different kinds of substance, all mixed up to-
gether as if a giant had stirred them all up while hot and
they had cooled quickly. Probably the original rocks
of the earth were formed as molten masses of semifluid
material, like lava that flows from a volcano during an
eruption. Such rocks are called igneous, of which granite
is an example.
Others look as if they were formed in layers. Such
rocks, like sandstone, shale, or limestone, were actually
formed from particles of ground-up rock being deposited
under water. Layers upon layers were made ; the lower
layer may have been carried down miles below the surface
of the earth, and when subjected to heat, pressure, and
chemical action the particles were cemented into solid
HOW WERE THE ROCKS FORMED?
217
rock. Perhaps a million years later this part of the earth
rose, the surface layers were worn off, and this layer of
material is back at the earth's surface once more, but
now solid sandstone and not loose particles. Such rocks
are called sedimentary.
Another kind of rock seems to be in layers, but these
layers are greatly curved or folded, like the rock shown
in the picture. These look as if they might have been
made like sedimentary rocks and then pressed together
by some great force. Possibly they might have been the
igneous rocks partly remeltetl, and pressure caused a
movement so that particles appear in bands somewhat
resembling layers. People who have made a study of
rocks believe both of these processes have been in action
and have caused these rocks to be changed from the
original condition. They are called metamorphic rocks.
Examples of such rocks are gneiss, marble, and slate.
Rocks and Minerals. Geologists call the material out
of which the solid part of the earth is formed rock. But
if you look at some rocks carefully, you will see they are
Geographical Survey, G. K. Gilbert Negative
Geographical Survey, T. N. Dale Negative
Sedimentary and metamorphic rock. How does the right-hand picture differ
from the left-hand one ? What seems to have happened to the metamorphic rock ?
218
ROCKS AND SOIL
made up of particles, some large, some tiny. Each of
these substances out of which rock is formed has a different
chemical composition and is called a mineral. Sulphur
is a mineral containing a single chemical element, while
table salt or a grain of white sand is a mineral each made
of two elements combined in compounds. Granite, on
the other hand, is made up of several minerals in which
quartz and feldspar are always present. Rocks usually
contain several minerals, but some, like the rock salt, are
single minerals. The name of the mineral, salt, is halite,
and when freed from impurities, we use it to season our
food. Mica is an interesting mineral. Some mica is
white and some is black in color. It has the remarkable
quality of splitting off in very thin almost transparent
sheets. It is often incorrectly called isinglass. It is used
as an insulator in electric devices and for windows in
doors of stoves.
Rocks and Minerals Are of Different Hardness. If
you take a number of different minerals, such as quartz,
feldspar, mica, rock salt, talc, gypsum, and others, you
Wright Pierce
This shows how the hardest rocks (granite) may be weathered to form soil,
has probably caused this rock to break down ?
What
HOW WERE THE ROCKS FORMED? 219
will find that your knife blade will scratch some and not
others. You can scratch your knife blade with quartz,
while the blade will easily scratch such a mineral as talc
or rock salt. Minerals, evidently, differ in hardness.
They also differ in other respects, such as color, chemical
composition, the kind of crystals they form, and other
ways. Because of these differences, the rocks out of
which they are made also greatly differ. Some are hard,
others relatively soft ; some strong, others brittle.
Rocks Change to Soil. If what has just been said is
true, then the change from rock to soil must go on much
faster in some rocks than in others. Soils also vary in differ-
ent places, depending on the kind of rock they are made
from. Quartz, for example, is harder than feldspar.
When granite breaks down to form soil, the quartz par-
ticles, being harder, grind the rest of the rock to fine
powder, while they remain as grains of pure quartz.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
hard heat sedimentary ice
soft cold durability clouds
softer igneous loose metamorphic
rock cut quartz scratch
solid molten soil melting
mineral vaporized water chemical
mud solidified air layers
Granite is an example of an (1) rock which formed from a
(2) condition. Sandstone is a (3) rock and was once
(4) particles which eventually were brought into (5) ,
probably through the action of (6) After being buried deep
in the earth loose material may under the action of (7) ,
pressure, and cementing by (8) action be changed into solid
(9) Both sedimentary and (10) rocks may undergo a
partial (11) and be changed greatly in form. This class of rock
resulting is called (12) Most rocks are made up of two or more
220
ROCKS AND SOIL
minerals. Rock salt is both a (13)_
is a very (15) mineral. It will even (16)
and a (14) Quartz
. steel. Rocks
vary greatly in (17) The brittleness of rock determines in
large measure how quickly it is changed to (18) In many
places the beach sand is almost wholly (19) because the
(20) rock has been ground to a powder.
STORY TEST
RALSTON HAS A FINE COLLECTION OF ROCKS AND MINERALS
Read carefully and critically. List all the errors and suggest corrections.
It has been great fun to make this collection, and I never tire
of showing them. First, I'll show you the minerals. This glass-
like stone is quartz. It is quite hard but you see I can just scratch
it with my knife blade. Here is a white mineral feldspar, easily
scratched by quartz. It breaks with more even surface than
quartz. See this beautiful specimen of isinglass. I put my
knife point under a thin edge and peel off a large transparent sheet.
These minerals that I have shown you all came from sedimentary
rocks. This piece of marble is an igneous rock because heat helped
to form it. Granite is a typical mineral that has been formed by
the slow cooling of molten rock; the more slowly it cooled, the
larger the crystals in it. Here is a piece of gypsum ; you can
scratch it with your thumb nail. This smooth pebble is found in
the bed of a brook. This
chip was probably broken
off by ice. The colored
streaks in this rock are prob-
ably due to the light which
reached it while the rest
was covered with soil.
PROBLEM II. WHAT IS
THE STORY OF THE
FOSSILS ?
What Are Fossils ?
Someone has likened
the earth to a book
whose pages tell its life
story. The leaves of
this book are the layers
A fossil fern-like plant. In what kind of
rock would you look for such a fossil?
WHAT IS THE STORY OF THE FOSSILS?
This fossil fish lived in recent geological time.
Wright P
How do we know this ?
of rock, and the characters we read are the imprints left
by the living things that inhabited the earth in past
ages. Moving water deposited sediments in oceans,
ponds, and pools of streams. Plants and animals living
near these places were often buried in these sediments
and as time went on and the sediment became rock, the
remains of the living things were preserved. Sometimes
they were the undecayed parts of plants and animals,
sometimes the skeleton, often only an impression, such
as a footprint or a space once occupied by the soft body.
Any such trace or remains of former life is called a fossil.
The story told us by these fossil remains is not very
complete, but it is plain enough to show us a number of
very interesting things. The first is that the earth has
been inhabited by living things for a very, very long time.
Geologists used to think it was millions of years, but they
now believe it a much longer period. New ways of esti-
mating the age of the earth have been found, one by
222 ROCKS AND SOIL
National Park Service
A fossil tree of the Arizona desert. These trees are found by the hundreds in some
parts of the west, in some cases having been changed to agate or other semi-
precious stones. This one is now held up by a concrete base.
figuring the amount of time it took to carry salt to the
oceans to give them their present saltiness. This estimate
is about 500,000,000 years. Another and newer estimate
has just been completed by a group of scientists appointed
by the National Research Council in Washington, and
they, basing their calculations on radio activity of certain
rocks, have estimated the age of the earth at the incredible
figure of over 2,000,000,000 years.
Of course life did not exist on the earth at first, and
nobody knows how the first life came. But we do get this
much evidence from the fossils. The very oldest igneous
rocks, which we have learned were formed when the earth
was very young, do not contain any fossils. The earliest
evidences of life come from bacteria, and following them we
find tiny plants and animals, all of which lived in water.
What Fossils Tell. The character of the fossil tells
whether it was deposited in salt sea water or fresh lake
WHAT IS THE STORY OF THE FOSSILS?
water. Land animals and the stems and leaves of plants
could only be deposited close to the shore. Corals could
only be buried in deposits in warm water. Plants which
grow only in arctic regions indicate cold water. Thus
fossils can tell something of the climate of regions of the
earth millions of years ago. Fossils of salt-water life dis-
close the fact that there have been seas where now it is land.
The relative positions of different layers of rock often tell
the relative ages of the different kinds of life on the earth.
In some parts of Arizona and other places, you can visit
petrified forests. Great trees which have been changed
to solid rock lie here and there. Some are formed of
beautiful agate or other precious materials. These trees
were buried by volcanic material, and the mineral matter
dissolved in the water replaced the woody fiber and pre-
served the form of the tree. In many parts of the
country, various animal remains, such as corals, shell, and
These animals were trapped in the famous tar pits of La Brea, near Los Angeles.
An elephant and wolves have been caught in the soft tar and the saber-toothed
tiger will soon suffer the same fate.
ROCKS AND SOIL
This huge reptile-like Brontosaurus lived on plants and grew to be 60 feet long.
It must have weighed 30 to 40 tons. Notice the skeleton of the man in the upper
picture.
bones, are found in the rock. In the far west, great
skeletons of extinct animals have been dug up. One of
these is that of a huge vegetarian called the Brontosaurus,
which was 60 feet long and weighed 30 tons. But skeletons
of still larger animals have been uncovered ; for example,
a great elephant-like creature, the Atlantosaurus, 100
feet long and weighing 100 tons. In some parts of the
world the fossils of flying reptiles and even ancient insects
have been discovered. Some of the dragon flies found
had a wing spread of two feet.
Changes in Life on the Earth. One very evident thing
comes from the study of these fossils. That is, that the
earliest forms of animals were very simple. Then the earth
became peopled with many water-living forms, mostly
>t took to duz.v/eAop cKo.rcxc.tee-ist.ic.
•modern -forms of lif
YictveWk oiztlze
f nom, 5 to 5 million.
forerunners
o modern.
5 to lo
"million ears
to
ancient/
ancestors
of plants'
ancC animals
took 15-25
million years
to develop ,
naost forms
are nov"<s*.tinct
amph ibictns
\
andi
verv simple
of living"
simple plcmts
and • r -
.
miuioyi y®ars
YZO
many many
yearns*
tnillion
"no
What are a few million years in the history of this old earth ?
H. & w. sci. 1—16
225
226 ROCKS AND SOIL
invertebrates. Then came vertebrate animals, all water
forms at first, followed by huge reptiles such as those
shown in the picture. Later still we find forms of mam-
mals much like those of recent times. Such is the wonder-
ful collection of animals which were caught in the tar
pits of La Brea, in Los Angeles, some 20,000 or 30,000
years ago. This collection includes tigers, sloths, mam-
moths, and many tropical forms not very different from
those living today. When man came is all a guess, but
it was probably a million or so years ago, a very recent
time measured in the earth's history.
Plant life also has shown great changes. After the
first plants appeared on land there must have been a period
very favorable for plant growth. Evidently the earth
had a moist, hot atmosphere, and perhaps the sun was
more powerful than it now is. At any rate, there was a
time, during which our coal beds were formed, that the
earth must have had a growth of great fern-like and
palm-like plants, which grew as tall as our modern trees.
In more recent times the plants had many of the charac-
teristics of our modern trees, and the flowering plants ap-
peared. In general, the same story is told by both plant
and animal fossils : first, that there has been continual
change in the forms of life ; second, that simpler forms
of life came first on the earth ; third, that the oldest forms
of life are found in the oldest rocks which are buried
deeper than the more recent forms ; fourth, that great
changes in climate and surface conditions have taken
place ; and fifth, that we can construct a very good picture
of past life on the earth by piecing together all the evidence
as we see in the picture on page 225.
It is pretty evident that life began in the water ; that
bacteria and simple plants were the first living things ;
that many forms which once existed have disappeared,
and that our present forms of life are still changing.
WHAT IS THE STORY OF THE FOSSILS? 227
SELF-TESTING EXERCISE
Select from the following list the words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
2,000,000,000 oldest not history
sediments youngest inhabit very
500,000 does animals rock
sand do marble mud
dead often plants fossil
living sandstone plant water
lived never petrified earth
Sedimentary rocks originated from (1) deposited in (2)
After (3) things came to (4) the earth, it (5) hap-
pened that plants or (6) would be buried in the (7)
After the (8) hardened into (9) it might preserve evidence
of the (10) or animal. Any evidence of a living thing pre-
served in this way in (11) is called a (12) It is believed
the earth is at least (13) years old, but living things have
not always (14) here. Igneous rocks which are the type of
the (15) rocks on the earth (16) (17) contain fossils.
Sedimentary rocks (18) (19) contain fossils from which we
read the (20) of life on the earth.
STORY TEST
HERBERT HAS HAD FINE OPPORTUNITIES FOR FIELD OBSERVATION
Read carefully and critically. List all the errors and suggest corrections.
Last summer I was lucky enough to be invited on an auto camp-
ing trip with my chum. His father, a science teacher, was one of
the party. In the Connecticut valley in Massachusetts we saw
great 3-toe footprints in beds of sandstone. There were no bones
of the animal but it was a fossil just the same. In Barre, Vermont,
we visited the world-famous granite quarries. We saw toads
there that the men said jumped out of hollow places when they
split blocks of granite out of the ledges. The toads must have
been living fossils. In northern New York we saw smoothed rocks
with scratches and grooves all running in the same direction.
These scratches were made by the glacier thousands of years ago,
and since they are records of what happened long ago, they are
fossils. In western Pennsylvania we broke off slabs of limestone
and found many excellent fossil shells. In a coal deposit we found
the imprint of a tree showing clearly the markings on the bark.
228
ROCKS AND SOIL
In one of the Indiana marble quarries we found splendid shells of
water animals and the skeleton of a fish. You doubtless remember
that marble is a metamorphic variety of limestone and so shows
the same fossils that limestone would.
PROBLEM III. HOW IS SOIL MADE?
Soil Is Rock. From what we have learned, we can
see that soil is formed from rock. There are many
agents at work, and this work is going on right under our
eyes. Take a rocky ledge such as is shown in the cut.
Beneath this ledge is a slope of broken pieces of rock,
some of which are small enough to make a coarse soil.
The rock breaks down to form this slope of fragments,
called a talus. But what causes it to do this ? Evidently
the forces of air, heat, cold, water, and gravity are at
work. Any changes in rocks brought about by changes
in weather or the
atmosphere are
called weathering.
Mechanical
Weathering. Some
rocks are broken by
the action of frost
and the sun's heat.
We know that frozen
water occupies al-
most 10 per cent
more space than in
a liquid state. Try
the experiment of
freezing a corked
bottle full of water
and see what hap-
pens. When water
inclosed in a crack
What kind of rock is shown here ? Find the talus
slope. How would you say rocks form soil ?
HOW IS SOIL MADE?
Amer. Mus. of Nat. Hist.
This tree started in a crack in a granite rock and has
exerted force enough to split it.
in rock freezes, the ice formed presses with a force of
2000 pounds per square inch on the rock surrounding it.
No wonder the
rock chips off !
When we add the
heat of the sun to
the action of frost,
and remember
that on the desert
there may be dif-
ferences of 100°
between the day
and night tem-
perature, we can
see why the out-
side of the rock becomes larger than the inside and strain
results which causes it to crack and break.
The tree in the picture has split the rock just as a wedge
will split a block of wood. As trees grow, their roots
press the rock apart more and more and thus allow the
other agents of weathering to act upon it. Burrowing
animals, earthworms, ground squirrels, gophers, and
woodchucks break up the soil into finer particles. Wind
and rain also help to break down rocky soil and distribute
it so that other agencies will also act on it.
Chemical Weathering. We do not realize that rocks
decay, but such is the case. Pure water will not have
much effect upon rock, but add to it a little acid and it
will soon eat away limestone rock. Plants give off acid
through their roots, thus causing certain kinds of rock
to break down. Then oxygen and carbon dioxide in rain
water cause rocks to oxidize and decay, or the rock may
dissolve. The beautiful red and brown coloring of rocks,
such as at Bryce, Zion, or in the Grand Canyon of the Colo-
rado River, is caused by the action of oxygen and water.
230
ROCKS AND SOIL
Demonstration 1. Solution of Limestone.
Pass carbon dioxide into a jar of limewater. What happens?
This substance has the same composition as limestone. Now
continue to pass the car-
bon dioxide into the jar,
and you will see the white
substance disappear. It
has been dissolved by the
extra carbon dioxide in
the water and has passed
into solution.
Erosion. You have
all seen gullies cut in
the bank of the river
after a heavy shower,
and have noticed that
soil is carried down
by the water and dis-
tributed in a layer at
the foot of the gulley. A mountain stream shows the
same effect on a large scale. This wearing away and
carrying off of material is called erosion. Our mountains
Streams play an important part in changing the
surface of the land. Explain how they do this.
Wright Pierce
Wind has caused these holes in the rock. How could it do this ? Read page 231.
HOW IS SOIL MADE?
231
are being leveled, our river valleys cut deeper, and soil
is being deposited far from where it was originally made
from rock — all by this force of erosion. Erosion is a
leveler which is carrying mountains into the oceans, and
producing many other changes in land forms over the
surface of the earth.
Erosion in its broad-
est meaning includes
weathering.
Erosion by Water.
The mountains of
Switzerland and many
of our western peaks
are huge rock masses
which are being worn
slowly away by water.
The force of the water
loosens the big bowl-
ders, rolls rocks down-
stream, rubbing one
against another, and
causing them to be
ground into powder.
In many a mountain
Stream today ,We may A view in the Carlsbad Caverns. Notice the
866 this powdered ma- stalactites and stalagmites formed from min-
. erals once held in solution in water.
tenal going down with
the turbid water to be deposited at the river's mouth in
the form of a delta.
Erosion by Wind. In many parts of the world, the
wind has an important part in soil making. In some
parts of western United States, the wind drives millions
of particles of sand against the sandstone cliffs with such
force that they are worn down and hollowed out by this
natural "sand blast."
Carlsbad Chamber of Commerce
232
ROCKS AND SOIL
Erosion by Solution. You know that sugar placed in
lemonade soon dissolves in it and disappears, but the
sugar may be tasted in all parts of the glass of lemonade.
The sugar passes from the solid to the liquid state by a
physical process known as solution. If a substance dis-
solves in a liquid completely, we say the substance is
soluble and that we have a solution. Rain water, although
perfectly pure as it starts to fall from the clouds, dissolves
air in falling and after soaking into the ground may soon
take up mineral matter into solution. As we have seen,
certain minerals, particularly the compounds of calcium
and magnesium, are slightly soluble in water which con-
tains CO2. In some parts of the country, great gaps and
caves have been
formed underground
where limestone has
been dissolved and
removed by running
water.
Hot Springs and
Geysers. Under-
ground water which
comes to the surface
in springs may con-
tain mineral matter
in solution. The
mineral springs of the
United States are
valued at millions of
dollars. Many of
these waters are
claimed to have me-
dicinal properties.
In regions where vol-
Old Faithful is so called because it always erupts . .
on time. Can you find out what causes this action? CaniC action has been
HOW IS SOIL MADE?
233
The Chisana Glacier, Alaska. Glaciers carry with them ground-up rocks and stones,
which may be deposited far from where they were eroded. Explain the meaning
of the dark line running up the right-hand side of this glacier.
recent, underground waters may be heated by beds of
lava which are still hot. Here we find hot springs. If
the water, instead of flowing regularly, is erupted inter-
mittently, the spring is called a geyser. Since hot water
dissolves mineral matter more readily than cold water,
much matter is brought by hot springs to the surface
and deposited as the water cools. Hot springs are found
in several parts of the world, most of them being in
Yellowstone National Park. Here there are about 3000
geysers, of which Old Faithful deserves its name, for it
erupts about once every hour, when it throws up about
700,000 gallons of water.
Erosion by Glaciers. A great ice sheet covers Green-
land today. The pressure from the continued accumu-
lation of snow causes a slow movement of this vast sheet
of ice into the ocean, and from time to time fragments on
the edges break off and form icebergs. It is believed
that many thousands of years ago a great sheet of ice
moved down from the north and covered a large part of
234
ROCKS AND SOIL
The Delaware Water Gap. Are these mountains old or young? How do you
know?
northern United States as far as the Missouri and Ohio
rivers. The tremendous weight of ice, thousands of
feet deep, scoured and broke off projecting hilltops and
mountain peaks. The stone fragments moving along
under the ice were efficient cutting tools for grinding
other rocks underneath. At the front of the ice sheet
streams of water poured out, carrying dirt and rocks,
which were deposited in layers, just as material transported
by our rivers is being deposited today.
How We Can Use Our Knowledge about Erosion. If you
were fortunate enough to take a trip across our continent,
you would be able to see some of the results of the various
agents and to interpret them as you went along. In the
far West you would pass through deep, rocky canyons
having steep, jagged sides. We recognize these and the
sharp rugged mountains of the West as the results of
quite recent erosion, as geological time goes. We would
see great deserts of wind-blown earth and sand and many
groups of fantastic rocks carved and etched by the
HOW IS SOIL MADE? 235
blowing sand. We might even have a sandstorm and have
the windshield of our car etched and pitted by the wind-
driven grains. And as we got near the eastern coast, we
would find mountains again wooded to their summits,
mountains with smooth rounded outlines which the
geologists tell us show that they are very, very old and
have had time to lose their angular steep sides so char-
acteristic of the younger bare mountains of the far West.
In some places we would find soil just where the forces
of weathering had produced it. This is called residual
soil. In other places the soil has been brought by moving
ice, water, or wind and is called transported soil.
SELF-TESTING EXERCISE
Select from the following list the words which best fill the spaces in the
sentences below and arrange the words in proper numerical order. A
word may be used more than once.
springs more ice colder transported
wells less steam outside geysers
rivers greatest water inside weathered
expand mechanical cooling soil residual
contract chemical heating rocks erosion
move air hotter lava weathering
iron oxygen separation dissolved dioxide
Ice occupies (1) , space than the water from which it is
formed. Freezing (2) is an important (3) agent in break-
ing down rocks in the process of (4) formation. When the
sun's rays beat down upon a rock, the (5) layers become
(6) than those below and as they (7) they tend to loosen.
Alternate heating and (8) finally results in the (9) of
fragments. Limestone rock is (10) by water containing
carbon (11) Rocks that contain only a minute quantity of
iron remain unchanged deep in the earth, but when exposed to the
air, turn brown and rusty because the (12) of the (13) has
combined with the (14) of the rock. Such (15) rock
crumbles easily, producing (16) The wearing down of rocks
and transportation of the material is called (17) Water is
a powerful agent of (18) Underground waters in some parts
236 ROCKS AND SOIL
of the earth are heated by subterranean (19) beds. These
waters bring mineral matter to the surface in boiling (20) and
(21) (22) soil is that which remains in the place where
it was produced. Soil moved to other localities by moving ice or
water is called a (23) soil.
STORY TEST
AN EXTRACT FROM ANNETTE'S NOTEBOOK ON SOILS
Read carefully and critically. List all the errors and suggest corrections.
Soil has not always existed on the earth ; it is therefore not an
essential factor of our environment. Before soil was formed, the
solid part of the earth was entirely sedimentary rock. Rocks
decay, crumble, and are reduced to soil through the agencies of
weathering but also through mechanical action of wind, water,
and ice. Perhaps you have seen how granite steps wear away
more quickly than marble steps. Our finest buildings quite often
have marble floors because of their durability. When water
contains nitrogen from the air in solution, it will dissolve limestone
and marble. Much soil in northern United States is transported
soil brought by running water and ice. Rocks on mountains are
more exposed than elsewhere, and for that reason the soil is deeper
on mountains than in valleys. Many rocks are eroded just by
the action of the oxygen of the air combining with the iron in the
rocks. There is still heat in the interior of the earth and in some
places underground water is made to boil, causing hot springs and
geysers. These waters have nothing to do with soil formation,
however ; the water may spout out and flow back, or it may flow
continually as in any cold-water spring.
PROBLEM IV. WHAT SOILS ARE BEST FOR
AGRICULTURE ?
Differences in Soils. We have seen that soil is weathered
rock, that either remains in place, or is carried away by
erosion. When water transports soil, it tends to sort out
and distribute different-sized particles to different places.
But if the volume and speed of the water change, a layer
of fine material may be placed upon a layer of coarse
material, or a fine-grained sediment may be laid upon a
WHAT SOILS ARE BEST FOR AGRICULTURE? 237
coarse one. The layers of sediment, too, may vary in
composition, depending upon the kind of rock from which
they are made. We know that sandstone forms sandy
soils, but we may not know that clayey soils come from
the breaking down of shales and feldspars. Igneous
and metamorphic rocks may yield both clay and sand.
Sand by itself makes a barren soil because there is not much
in it except glass-like silica or quartz. Plants need a
large variety of elements. Limestone produces a lime-
stone soil which is usually very fertile. The soils from
feldspar furnish potassium, sodium, calcium, magnesium,
and iron, making a rich soil. But if it makes a compact
clay, it is too wet and lacks air for good crops. Mixed
with sand, it makes a good soil for crops. Soils, there-
fore, differ in different parts of the country, depending
upon the rocks found there, or transported there. The
lower Mississippi region is very fertile because of the
rich soil brought down in floods and deposited where
the river overflows its banks.
Kinds of Soils. Those of us who have gardens know
that the fertility of our plot depends largely on the soil
which makes it up. Most soils may be divided into the
following general groups : Gravel, composed of a mixture
of coarse sand and pebbles ; sand, largely made of quartz,
produced from granite or sandstone ; clay, rock ground
up so fine that it is not gritty when rubbed between the
fingers, feels sticky, molds rather easily with water, and
becomes hard when dry; silt, particles too fine to class
as sand and too coarse to be a clay ; loam, a combination
50 per cent of sand and 50 per cent clay and silt together ;
humus, largely decayed plant and animal matter. For
gardens the latter material is considered quite necessary.
Demonstration 2. Water in Soil.
Materials. Four student-lamp chimneys ; equal volumes of
dry sand, clay, loam, and humus. Tie two or three thicknesses of
238
ROCKS AND SOIL
cheesecloth over the lower end of each chimney. Invert them and
pour in -J- pint of water on the soil in each. Catch the liquid that
passes through and measure it. Which soil holds water best?
Water and Air in the Soil. You are all familiar with
the fact that coffee creeps up on a lump of sugar placed
partly in it, and that oil rises in a lamp wick. You may
wish to try the experiment on capillarity described below.
Have four very fine tubes,
each having a different
hole of different diameter
running through them.
These are placed side by
side in a dish of water.
The smaller the diameter
of the tube, the higher
the water will rise in it.
This rise of fluids against
the force of gravity is
called capillarity. Soil,
if examined under a mag-
nifying glass, is found to
be made up of many par-
ticles of different sizes,
each particle holding
around it a film of water,
as shown in the diagram.
Water rises through the
Each particle of soil is surrounded by a
film of water and air spaces are found
between the particles. The artist has ex-
aggerated these to show how air and water
are held in the soil.
WHAT SOILS ARE BEST FOR AGRICULTURE? 239
narrow spaces between the soil particles by capillary
action, and thus it is found in the soil not far from the
surface.
The loose, porous structure of the soil allows a certain
amount of air to remain in the spaces. Plants breathe,
since they need the oxygen of the air just as much as we
do. And since the delicate roots of plants absorb air
as well as water, porosity of soil is very necessary for the
garden.
Demonstration 3. What Types of Soil Favor Capillary Action?
Materials. Lamp chimneys, four types of soil as in last experi-
ment, large shallow pan.
Methods. Place equal amounts of different types of dry soil
in different chimneys. Pack the soil fairly tight. Set each chim-
ney in a pan filled with water to a depth of an inch. Notice the
water rising in the different soils. In which soil does it rise fastest?
Highest?
Conclusion. Which soil do you think is best adapted to carry
moisture?
Effects of Cultivation on Soil. In order to keep the soil
from being packed too firm and hard, and thus prevent air
from passing into it readily, we cultivate, or break up, the
top layer of the soil either by hoeing, raking, and harrow-
ing, or by means of a cultivator. Cultivation crumbles
the soil and allows the plant roots to creep through it
more easily. It breaks up the soil particles so that water
can dissolve out the materials which the plants use for
240
ROCKS AND SOIL
food and allows air to pass through the soil. By either
a loose surface mulch or by a paper mulch as seen below
water is more easily kept in the garden soil.
Mulches. Farmers have learned by experience the
value of cultivating the surface of the ground to a depth
of three or four
inches, making a so-
called dust mulch
over the surface. If
the surface becomes
hard and cracks, the
water will evaporate
very quickly. By
placing a finely pow-
dered layer of soil
over the top of the
field, water will be
held in it for a much
longer period. In
some parts of the
West where rain is
very infrequent,
farmers practice
what is known as
dry farming. To do
this they must first
plow the ground deep
so that when the rain comes the ground will be ready to
soak it up and retain it. Then the surface layer of the
ground must be constantly worked and turned over to
form a surface mulch. This is done by making a layer
of very finely pulverized soil on top. The latest method
of keeping water in the soil is seen in the picture.
Here a layer of heavy paper is placed over the soil in
which the plants are growing and this prevents the water
U. S. Dept. of Agr.
Paper mulch. Experiments have shown that
moisture is best kept in the ground by means of
a paper mulch such as is seen in this picture.
Are there any evidences of its use shown here ?
WHAT SOILS ARE BEST FOR AGRICULTURE?
in the soil from passing out by evaporation. In some
places farmers can only grow one crop every other year
because of the small amount of water. In such cases,
the farmer keeps half of his land under cultivation, and
the other half covered with straw or a surface mulch so
as to allow it to accumulate water. Thus a crop is raised
every two years without the addition of more moisture
than the soil holds by reason of its mulch.
Demonstration 4. To Show That Certain Mineral Substances Are
Needed for Plant Life.
For this experiment use five wide-mouth bottles : one con-
taining a nutrient solution with all the necessary minerals, and
each of the other four containing a nutrient solution l lacking
start tkef experiment) vi£h younfe
all about I the same
either iron, calcium, potassium, or nitrogen. In these bottles
place young seedlings, and allow them to grow for several weeks.
Note the results. What mineral substances are necessary for
the growth of green plants?
1 The control nutrient solution is made up as follows :
Distilled water 1000 to 1500 grams
Potassium nitrate 1.0 gram
Magnesium sulphate 0.5 gram
Calcium sulphate 0.5 gram
Calcium or potassium phosphate . . . 0.5 gram
To this solution a trace of some iron salt, as ferric phosphate, should be
added.
If you do not have the facilities for making the solutions needed, have
a druggist weigh out the required amounts of the several different substances
and add to distilled water, as suggested in the experiment.
H. & w. sci. i — 17
242
ROCKS AND SOIL
Elements Used by Plants. There are a number of
elements that are found necessary for the growth of plants.
Three of these, carbon, nitrogen, and oxygen, are found
in the air, while phosphorus, potassium, magnesium,
calcium, iron, and sulphur are found in soils. In order
for plants to grow, these elements must be in the form
of soluble compounds so that they can be absorbed
through the roots of the plants. Iron aids in making
the leaves green. Potassium helps the plant to make
food substances. Phosphorus helps the root to grow
and seed to ripen. Calcium aids the roots by separating
the substances in the soil from other materials so that
they can be readily absorbed. Nitrogen is necessary
because of the relatively large amount used in the living
matter of plants.
Acid and Alkaline Soil. In the far West, alkali soil is
often found, especially in desert regions. If such regions
get water through irrigation and are used for agriculture,
as much as possible of the alkali must be removed from
Wright Pierce
This is a dried-up lake bed which is impregnated with alkali. In the rainy season
this is a lake so impregnated with alkali that the water is not fit for use.
WHAT SOILS ARE BEST FOR AGRICULTURE? 243
the soil or crops will not grow. This is done by flooding
and then draining the land, thus washing out some of the
alkali. In some parts of the country the soil becomes
acid and this prevents the growth of crops. In such cases
lime is used to neutralize the acid and thus sweeten the
soil.
SELF-TESTING EXERCISE
Select from the following list the words which best fill the spaces in the
sentences below and arrange the words in proper numerical order. A
word may be used more than once.
gravel black decreases fertilizers
loam dry increases capillary
clay wet enrich lime
humus air ability acid
sand scarce checked water
silt evaporates abundant mulch
red condenses dissolves conserve?
A good garden soil contains (1) , composed largely of fine
grains of quartz, (2) , which is extremely fine, and (3)
which contains organic compounds and gives the (4) color
to a rich soil. A compact soil neither allows (5) .to pass up
or down readily nor does it allow space for (6) which is neces-
sary for the roots of most plants. Water creeps up through minute
crevices by (7) action. The movement of water is (8) by
cultivation. Packing a porous soil (9) the loss of water from
the surface where it (10) and passes into the (11) Loos-
ening the particles and increasing the air spaces within the soil
(12) the loss of water which (13) if it reaches the surface.
Cultivation of the surface produces a (14) that (15) mois-
ture. Soils long used lose their (16) to produce (17)
crops unless (18) are added to (19) them. Acid soils are
sweetened by the addition of (20)
STORY TEST
WILL ARCHIE HAVE A GOOD INDOOR GARDEN?
Read carefully and critically. List all the errors and suggest corrections.
I plan to have an indoor garden. I have a large flat pan to
hold the soil. It was a problem to know what soil to select. I
went to a sand pit where there were all kinds. The sand was
244 ROCKS AND SOIL
gritty, had sharp edges, and I was afraid it would injure the seeds
so I discarded that. There was some " leaf mold," as the man
there called it, at the very top under some shrubs. He recom-
mended that, but I didn't want the mold on my seeds. The black
earth extending down a foot from the top looked too dirty so I
discarded that. There was a streak of gravel, but I knew tiny
roots couldn't penetrate the pebbles. Then I saw two more kinds
of soil. One was a yellowish sand that looked good to me, but
our experiment showed it was porous and so when I watered the
plants the water would run through. The last was a bed of clay.
I could see that this was fine grained. It was in such lumps I
could hardly get it out. I could easily see that if I watered it that
the water would have hard work to get out, so I chose the clay.
I also knew that it was richer in food value for plants than sand is.
THE REVIEW SUMMARY
In preparing a summary of what you have learned in this unit,
you will want to place emphasis on the big ideas which have
come out of the applications of the facts you have learned and the
demonstrations you have seen. These big ideas we call general-
izations. For this unit they are as follows :
1. The surface of the earth is being constantly changed by the
forces of water, wind, heat, cold, and other agents.
2. These changes are always going on night and day, winter
and summer.
3. We can recognize whether these changes are recent or very
old by the appearance of the earth's surface.
4. We know that different forms of life once inhabited the
earth because of remains in the rocks called fossils.
5. Soil has been formed and now is being formed by the weather-
ing and erosion of rocks.
6. Plants use the elements of the soil in order to live.
Before making your review summary, test your knowledge of
the facts of the unit by checking over the text so as to be sure you
know the facts underlying the generalizations ; then, using the
generalization, the material in the text, and in addition everything
you have read, seen, or done yourself, make a summary outline
for your workbook. This outline you may use when you make
a recitation.
WHAT SOILS ARE BEST FOR AGRICULTURE? 245
TEST ON FUNDAMENTAL CONCEPTS
Make two vertical columns in your workbook. Head one CORRECT
and the other INCORRECT. Under the first place the numbers of the state-
ments you believe to be correct. Under the second place all the numbers
you believe to be incorrect. Your grade — right answers X 2-^-.
I. A rock should always be classified as igneous if it: (1) will
scratch glass ; (2) is made of crystalline minerals ; (3) is made up
of hard layers ; (4) is made of granite ; (5) contains quartz and
feldspar.
II. The following rocks were formed by cooling from a molten
state : (6) limestone ; (7) sandstone ; (8) granite ; (9) marble ;
(10) fossil-bearing rock.
III. The land surface of the earth is being leveled by many
agents, among them are : (11) ice ; (12) running water ; (13) grav-
ity ; (14) the changing phases of the moon; (15) wind.
IV. The presence of fossils in the rocks: (16) makes it pos-
sible to tell the age of the earth; (17) shows when granite was
first formed; (18) gives a record of much of the early plant and
animal life; (19) shows that there was life on the earth before
there was soil; (20) shows that the size of animals on the earth
became larger and larger with the passing of time.
V. Soils which are able to retain moisture are : (21) composed
of much coarse gravel ; (22) mixtures of sand and clay with surface
freshly rolled; (23) mixtures of sand and clay with the surface
layer cultivated; (24) those having the surface covered with
thick paper ; (25) those on which commercial fertilizers are used.
VI. These things contribute to soil-making: (26) heat and
cold; (27) solution by water; (28) mechanical action of water;
(29) movement of glaciers ; (30) icebergs.
VII. A good soil for the garden must : (31) contain 90 per cent
quartz sand ; (32) have a large variety of metals in it ; (33) contain
both moisture and air ; (34) be porous ; (35) be compact like clay.
VIII. Water may cause erosion by : (36) mechanical grinding
action ; (37) evaporation from rivers ; (38) solution aided by carbon
dioxide ; (39) hot water in geysers ; (40) wave action.
THOUGHT QUESTIONS
1. What agencies have been at work in your locality to produce
soil? How have they done their work?
2. You live in a limestone region and one day find a small cave
in a limestone ledge. How would you account for its presence
there?
246 ROCKS AND SOIL
3. You find a small bed of fossil clam shells near your home.
What kind of rocks do you expect to find above and below
them?
4. Classify the following agents as chemical, or mechanical :
frost, wind, lightning, oxidation, rain, acids in soil, plants, carbon
dioxide.
5. If you were to study your locality to find evidence of the
action of glaciers, what would you look for?
6. How do the farmers in your locality aid nature in the pro-
duction of crops?
7. What forces and agencies in your locality make plant life
possible?
REPORTS UPON OUTSIDE THINGS I HAVE READ,
DONE, OR SEEN
1. Report upon an article related to some topic discussed in
this unit. The article may be from a current number of a science
magazine or from some popular science book you have read.
2. Present-day glaciers of the world.
3. How a river makes soil.
4. The varieties of rock in my state.
5. My visit to the museum to study minerals.
SCIENCE RECREATION
1. Make a collection of minerals and arrange them according
to their hardness ; try the scratch test. The scale of hardness for
minerals is :
1. Talc — easily scratched by fingernail. 2. Gypsum —
scratched by fingernail, but not easily. 3. Calcite — scratched
easily with knife point, but not with fingernail. 4. Fluorite —
scratched with knife, but not easily. Does not scratch glass.
5. Apatite — scratched with knife. Scratches glass with difficulty.
6. Felspar — will scratch glass easily. Can be scratched with
knife with difficulty. 7. Quartz — • will scratch glass easily. Can-
not be scratched with knife. 8. Topaz — harder than quartz.
Is scratched by corundum and diamond. 9. Corundum — harder
than topaz. Is scratched by diamond. 10. Diamond — hardest
mineral. Is scratched by none, but will scratch all others.
2. Make a collection of pictures taken from travel folders
illustrating some of the work of erosion in this country.
3. If you live in a glaciated region, make a report on the effect
of glaciers on your township.
WHAT SOILS ARE BEST FOR AGRICULTURE? 247
4. (a) Make a trip into the country to study the effect of water
erosion. How do gullies which have recently been made differ
from the older ones in shape? Make two cross-sections on graph
paper for your notebook to show this difference. If you live in
a hilly country, try to see if all you noted in the gully can be applied
to the valleys cut by streams between the hills.
(6) Make several excursions into the surrounding country and
try to find as many effects of weathering as you can. Write up
your findings in your notebook.
5. Show in any way you can that soil is a mixture and not a
chemical compound.
SCIENCE CLUB ACTIVITIES
1. Have a meeting devoted to a field trip. Collect different
specimens of rock found in your community. Bring them, and
any other specimens of rocks which you may have, to school for
laboratory study. Record in your notebook where each specimen
was found. If you live in a part of the country where rocks are
abundant, note where they come out of the ground. Do they
lie in layers? If so, look for the remains of impressions of plants
and animals in them.
2. Organize a collecting trip to get rocks and minerals for the
school museum. Label and classify them.
3. If you live in a region containing sand dunes, make a field
trip out there and report back to the club on how dunes are built,
4. Plan a meeting at which the program will consist of reports
made by teachers or pupils who have visited some of the National
Parks.
REFERENCE READING
Bradley, J. H., Earth and Its History. Ginn, 1928. Surface destruc-
tion, page 36 ; Rocks, page 176 ; Fossils, page 270.
Cole, G. A. J., Rocks and Their Origins. Macmillan, 1923.
Fairbanks, H. W., Stories of Rocks and Minerals. Educational Pub.
Co., 1926. Origin of rocks, pages 9-19 ; Erosion, pages 23-27 ;
Fossils, pages 76-87.
Hawkeworth, H., Adventures of a Grain of Dust. Scribner's, 1922.
Hawkeworth, H., Strange Adventures of a Pebble. Scribner's, 1921.
Hotchkiss, W. 0., The Story of a Billion Years. Williams and Wilkins,
1932.
Reed, W. M., The Earth for Sam. Harcourt, Brace, 1930. Chapters
V and X.
Washburne, H., and Reed, F., The Story of the Earth and Sky. Century,
1933. Parti.
SURVEY QUESTIONS
Do you know how living things differ
from those which have no life ?
Do you know why we find different
living things in different places ?
Do you know the names of the most
common plants and animals found
in your own yard ?
Do you know ten birds common to
your locality?
Do you know the best places to find
frogs, small fish, and turtles in
your neighborhood ?
Do you know the name of the large
groups of plants and animals and
how to place living things you find
in those different rous ?
Central R. R. of N. J.
UNIT X
LIVING THINGS IN THEIR ENVIRONMENT
PREVIEW
What is being alive ? You know what your dog or cat
does and what you do every day. You eat, sleep, move
about, and play. But when it comes to really knowing
what life is, we cannot tell very much about it. You know
that you and your pet eat food, digest it, use it somehow
to release energy and to grow, and that you are able to
get rid of harmful wastes. You know that animals and
plants are able to form new living things like themselves.
But it is hard for a beginner in science to know much
about what life really is, for that is a problem that has
been troubling scientists for a good many years.
Scientists say that everything living or nonliving is in
the long run a manifestation of electricity ; that the matter
out of which all living or nonliving stuff is composed is
made up of unlike units, electrons and protons ; and that
every change in nature is due to the action and inter-
action of these particles. But when you have heard this
statement and even seen demonstrations which show it
to be true, you still cannot understand what it means.
So it is with life. We may talk very learnedly about it
and have all kinds of theories concerning it, but we really
have to go back to its manifestations — to what it does
rather than to what it is — if we are to try to understand
much about it. About all we can say is this : that living
things show their aliveness, first, by being sensitive. They
respond or react to the stimuli of their environment. You
249
250 LIVING THINGS IN THEIR ENVIRONMENT
can think of hundreds of ways in which living things re-
spond to stimuli. Roots grow towards water, leaves and
stems turn to the light,
earthworms seek dark-
ness, and moths fly
toward a bright light.
All the forces of the
environment influence
us and we make re-
sponses. See how
many of your own
daily acts are actual
responses to stimuli.
Think of a pickle and
see what happens. Do
you know why your
mouth watered ? Ask
your teacher to ex-
plain or read about it
in some physiology.
Did you ever think
of the many kinds of
living things every-
where around us ? Life is everywhere — birds and in-
sects in the air, fish and frogs in the water, animals and
plants on the land, and even in the soil. A careful sur-
vey of a square foot of earth will show it teeming with life,
most of it microscopic. You also must have wondered
why certain plants and animals are found living in swamps
or ponds, while others, quite different, are found in the
woods or fields. Why do we find polar bears and seals in
the arctic regions and lions and tigers in the tropics?
Why is it that there are no trees on the tops of the moun-
tains and plenty of trees further down the slopes ? Why
is it that the desert plants and animals differ so greatly
Wright Pierce
This plant was photographed after having been
placed in bright sunlight for six hours. Are
green plants sensitive 7
ADAPTATION TO THE ENVIRONMENT
251
from those that live in the water? Why do we find such
different animals along the coast of the seashore from
those we find on the
shores of inland lakes ?
If you really think
about this, you can-
not escape realizing
that this living of dif-
ferent things in differ-
ent places must have
something to do with
fitness or adaptation.
If a fish has gills in-
stead of lungs, it will
live in the water, and
if a bird has wings in-
stead of front legs, it
can fly. Well, you
are "warm," as they
say in guessing games.
American Museum of Natural History
What adaptations can you find that fit these
animals to live in different environments? In
what respect are their environments similar ?
But there is more to
the problem than this. We would have to ask how these
adaptations were brought about and why certain plants
and animals were always found living together in certain
localities and not in others. We would find that most of
our answers depend upon that characteristic which living
things have of reacting to stimuli.
Another thing that boys and girls want to know about
living things is the names of some of the plants and ani-
mals that are found in certain localities that they are
likely to visit. We want to know what animals we will
find in the ponds near at home, what plants and animals
we are likely to see in a field trip to the mountains or the
shore, what plants we can best use in our home gardens,
what common birds can be persuaded to nest in our home
LIVING THINGS IN THEIR ENVIRONMENT
A field trip to the shore. After you have finished this unit come back to this
picture and tell what forms of life the group will probably find in this place.
grounds, and how we can best attract them. All these
and many other questions come into the minds of boys
and girls when they think about the living things that are
their neighbors.
PROBLEM 1. WHAT IS BEING ALIVE?
Some Beliefs about How Life Originated. On the
other hand, we know a good deal about what living things
do and how they differ from things that are not alive.
For thousands of years people thought that living things,
such as flies, bees, or other insects, were formed out of the
rotting flesh of animals. The Bible quotes such a belief
when it gives Samson's riddle : "Out of the eater came
forth meat and out of the strong came forth sweetness."
WHAT IS BEING ALIVE?
253
Samson saw some little flies coming out of the decaying
carcass of a lion. He thought the flies were bees and that
they arose spontaneously from the lion's body — hence
the riddle. This belief that living things arose spon-
taneously was held for many centuries, and it was not until
the time of Louis Pasteur, l the great French scientist, who
knew so much about bacteria, that this belief was finally
proved false by a series of experiments. Now we know
that for a thing to be alive it must come from another
thing of its own kind that was alive. Life comes from life.
We all know that chickens lay eggs from which little
chicks are hatched and that plants form seeds which
under favorable conditions grow into plants like those
which formed the seeds. Life is like a stream, it flows
on and on.
Living Things Grow. You may have perhaps made
rock candy and noticed that as the sugar solution dried
out, crystals formed on the string. These were formed
from the sugar in the solution. The crystals grew by
J. C. Allen
Life comes from life.
1 Pasteur (pa'ster'), Louis (1822-1895), French biologist and chemist.
I
254 LIVING THINGS IN THEIR ENVIRONMENT
adding sugar from the outside. Living things grow —
not from the outside, like crystals of sugar or ice, or the
beautiful stalactites in a cave, but from the inside. As we
shall see later, living things have the power to take in food
and change it to the living stuff out of which they are
made.
Living Things Are Built out of Cells. Another charac-
teristic of living things is that they are made up of tiny
J ,, units of material
called cells. If very
thin slices of a plant
stem or bits of onion
skin be examined un-
der a microscope,
they will be seen to
be made up of tiny
structures such as
you see in the dia-
. gram. These cells
The cells of onion skin seen under a compound
microscope. The oval structures in the cells are have Various charac-
the nuclei. How many nuclei (singular, nucleus) to teristic shapes in an-
eachcell? • i j i u
imals and plants, but
they are always very small. They grow by dividing,
forming groups of like cells, to which we give the name
tissues. In the stem of a plant we find several different
forms of cells, some with heavy walls, so that they may
support the stem, some lengthened out to form tubes
through which the sap may pass, still others soft and
dividing rapidly. The stem is growing fast in the region
where these soft, rapidly dividing cells are formed, for
living things grow in size by the increase in the number
of their cells.
Living Things Are Responsive. Then living things are
responsive to conditions outside of themselves. A dog
comes when you call him, a plant turns toward the source
WHAT IS BEING ALIVE?
255
of light, we hear the sound of the gong that marks the
passing of classes and respond to its stimulus by going
to the next class. Life is said to be a series of responses
to stimuli. But nonliving things do not show this ability.
You could talk all day to a stone and it would never move.
•Sound waves
enter th« «ar
Living things are responsive. Prove it from this diagram.
Life Depends on the Environment. Life seems to
depend upon certain factors of our environment. We
have already seen that both plants and animals need the
air, water, light, soil, and a favorable temperature in order
to live. Even man, with all his ability to change and con-
trol his environment, cannot go beyond the narrow bound-
ary of the sea and air that surrounds our earth's surface
Even if, like the modern aviator, he carries oxygen with
him, he is limited to the supply he can take, or if, like
Beebe, he penetrates the ocean depths, he is limited by
the strength of his bathosphere and the amount of oxygen
he can take with him.
Living Things Respond to the Environment. Almost all
of us have kept pets and think we know pretty well what
256 LIVING THINGS IN THEIR ENVIRONMENT
" being alive" is. Our dog or cat exhibits his liveness in
running to meet us, in frisking about, in barking or mew-
ing, in eating and sleeping, and in any one of the various
things that a live dog or kitten will do.
We can say what living things will do and predict pretty
well what they will do under certain conditions. We
know our dog will come to us when we call him, will growl
or bite when annoyed, will eat when hungry, and drink
when thirsty. He will retreat to his kennel to get out of
the sun and will whine to get in the house when he is cold.
And if we compare a boy or girl with a dog, we find them
very much alike in the way they act under similar con-
ditions. These conditions which, in the case of the dog,
the boy, or the girl, affect the organs of sight, hearing,
taste, touch, or some other sense, are called stimuli and
they all are said to react to stimuli of its environment.
Living things react to stimuli and things that are not
alive do not.
SELF-TESTING EXERCISE
Select from the following list those words that best fill the blank spaces
in the sentences below and arrange the words in proper numerical
order. A word may be used more than once.
divisors dividing food characteristic
factors substance creations animals
plants , living kind environment
life drink subtracting parts
same responsive dead different
stimuli inside turn multiplying
middle outside respond similar
cells other grow adding
Living things differ from nonliving things in several definite
ways. Living things always come from (1) similar (2)
Reproduction is a (3) of both (4) and (5) Then
living things (6) , not from the (7) like a crystal, but
from the (8) Living things are always made up of tiny
GREEN PLANTS SOLVE LIFE PROBLEMS 257
units of (9) material called (10) These have (11) .
sizes and shapes, according to the (12)_: of structures they form.
But they are always very tiny and grow by (13) into more
(14) like themselves. Living things use (15) for this
purpose. Then things that are alive (16) to (17) from
outside themselves. They are thus said to be (18) They are
also dependent upon the (19) of their (20) and if any of
these are changed, it may mean the death of the living things there.
STORY TEST
MARY WRITES ON BEING ALIVE
Read carefully and critically. List all the errors and suggest corrections.
I know that I am alive. How do I differ from something that
has no life? Well, that isn't hard to say. I can jump about and
play and move and a dead thing can do none of these things.
However, I haven't told what being alive is.
People used to think that living things came from dead things,
like flies from dead horses or snakes from horsehairs. Some
people still believe such things. But Louis Pasteur, the French
scientist, proved they were wrong hundreds of years ago.
A living thing always thinks. A living thing has a special
shape, both legs and arms. It hears, it moves, and it has weight.
Oh, yes, and a living thing grows and uses food for this purpose.
But I do not know what life is any more than do the scientists.
PROBLEM II. HOW DO GREEN PLANTS SOLVE
THEIR LIFE PROBLEMS?
Green Plants Make the Food of the World. There
have been sun worshipers among men since earliest
times. But there has never been a more ardent sun
worshiper than a green plant. And there has never been
an engine that has done more or better work than the
mills that are found within the green leaves of plants.
These mills get their power from the sun and can run
only in the sunlight. It is a wonderful story — that of
how the green plant does its work. And it is all the more
wonderful because without this work you and I could not
H. & W. SCI. I — 18
258 LIVING THINGS IN THEIR ENVIRONMENT
live. If you think for a moment, you will see why this
statement is true. Try to think of some animal that
lives on flesh alone — such as a lion or tiger. But it
preys on cattle, deer, antelope, and other grass-eating
animals. Or take a big trout that lives upon smaller
•meat
zesting
animals
kUl and
eat-
eater®
plants
make fooctfw-
all the earth.
The food cycle. Follow it through and try to prove that green plants make
the food of the world.
fishes, insects, and insect larvae. In every case the food
of the smaller animals can be traced to the green plants.
Everywhere in nature we find that green plants form the
basis of the world's food. The great flour mills merely
change the raw food materials made by the wheat plant
into a form that we prefer to eat. Other animals like
cattle eat the food as the plant makes it. See if you can
find any cases of animals that do not depend on plants for
their food, and bring the case up before the class for dis-
cussion.
How Are Plants Fitted to Do Their Work? Everyone
is familiar with a green plant. We all know it has roots
which hold it in the ground, an upright stem which bears
the green leaves, and sometimes flowers which form fruits
GREEN PLANTS SOLVE LIFE PROBLEMS
259
containing seeds. We remember that the two big prob-
lems of living things are food getting and continuing their
kind. Let us see if we
have any clews as to
how a plant may do
these things. We will
take the production of
young plants first, be-
cause it is easier to see
and understand.
The Use of the
Seed. If you split
open a soaked bean
seed and remove the
tough coat, you will
find a tiny plant be-
t ween the two
" halves" or cotyle-
dons. Such a baby
plant is called an em-
bryo and is found in
all kinds of seeds.
Evidently seeds pro-
vide plants with a
means of reproducing
their kind. The young plant which grows is called a
seedling. If you plant bean seeds in sawdust, you will
be able to see just how the embryo within the seed de-
velops into a plant.
What the Roots Do. Plants always have roots. These
anchor the plant, but they do more than that. Later,
when we study biology, we shall find that they are pro-
vided with millions of tiny absorbing organs which receive
water from the ground and pass it into the inside of
the root. Here it passes into woody tubes, which run
An entire plant. How many structures can you
name ? Can you give the use of each structure ?
260 LIVING THINGS IN THEIR ENVIRONMENT
from the root up into the stem and on into the leaves
themselves.
How the Leaves Are Placed. Since the main work of
a green plant is food getting and since it has to make its
ovule
C0OOOCF
-stigma:
^-.-pollen
/;-• stamen
parts of a pea f lover-
-scar- left
the seed, is torn,
from tbe poet
seed Covering
or fr-ixitx
/^j/itb. -SeeoCs
Can you explain where and how seeds are formed after studying this diagram
carefully ?
own food out of substances in its environment, we shall
want to see how this is done. We have already said that
the sun gives the power to run this food factory. And
when we are told that it is the green substance inside the
leaf that does the work of manufacturing food, we shall
naturally look for adaptations in the plant which result
in getting just as much sunlight as possible on the green
leaves. Look carefully at almost any tree and you will find
that not only are most of the leaves placed so that their
flat green surfaces get as much direct sunlight as possible,
GREEN PLANTS SOLVE LIFE PROBLEMS 261
Water film
-Soilparticle
The prolongation is called a root hair. Each
rootlet is provided with thousands of these tiny
absorbing organs.
but you will also find
the leaves are so placed
that if you could look
down in them, they
would form a contin-
uous pavement of flat
leaves, each crowded in
between its neighbor
and each getting all
the light possible.
Green Leaves Make
Food. Green plants
almost always have leaves. These flat green structures are
of various shapes and the soft green tissues are supported
by veins. The veins are really
bundles of tiny woody tubes
which carry water up from the
roots to the leaves and food
down from the leaves to other
parts of the plant. The sur-
face of the leaf, usually its un-
der surface, is filled with tiny
breathing holes called stomata.
The leaf is a complicated food
factory in which the power to
do work is provided by the
sun, the raw materials sup-
plied from the air through the
stomata and from the roots by
the veins. The work is done
to cW<y<ru:f in the green part of the leaf.
Carbon dioxide from the air
and soil water from the roots
are combined into food in the
tenais to make food. green parts of the plant, while
part of air-,
carbon. cCLoxi.de
is taken, in by
side/ <5 leaf
262 LIVING THINGS IN THEIR ENVIRONMENT
Wright Pierce
Will all of these flowers produce fruit? Read
your text carefully before you give a reason for
your answer.
This is a simple flower of the lily family. Its parts
are in 3's. Do you find any evidence of this?
oxygen is given off as
a waste product dur-
ing the process. We
shall learn more of the
details of this process
in our later study of
plants and animals.
How Plants Grow.
Green plants grow
larger and produce
more leaves and
branches because the
buds, which you can
find in the winter on
the sides and tips of
the branches, burst
open and grow either
into branches with
their leaves, or into
flowers. You have all
seen an apple, apricot,
or other fruit tree in
bloom. The flowers
come in the spring so
that there is plenty
of time for the seeds
to ripen before cold
weather. The food
and water necessary
for growth is trans-
ported through the
tubes in the leaves
and stems to the
places where rapid
growth is taking place.
GREEN PLANTS SOLVE LIFE PROBLEMS
263
Thus we may have very rapid growth of some parts.
Of What Use Are Flowers? If you will study the
picture of the flower on the opposite page, you will find
certain structures called stamens. They contain pollen
grains of which we will learn more later. In the center
of the flower we see another structure called the pistil.
The enlarged base of the pistil, called the ovary, holds
the structures which will later become seeds. If you cut
open an ovary, you will find the future seeds, called
ovules, fastened to the inner walls of the ovary.
What Results from Pollination. If you have ever
visited a garden, you could not help but notice bees
visiting flowers. If you watch one
carefully to see what it is after, it
will be seen to poke its long tongue
down into the flower. It is after
nectar, the sweet secretion out of
which bees make honey. But bees
also gather pollen, the yellow tiny
grains which are made in the tiny
boxlike anther of the stamens. So
it often happens that the bees, in
their quest for food, transfer pollen
from the stamen of one flower to
the pistil of another flower of the
same kind. This process is called cross-pollination and
results in the growth of the pollen grains which light on
the end of the pistil. These grains grow a long tube down-
ward into the lower part of the pistil, called the ovary.
This tube carries with it several cells, one of which, a very
tiny body, is called the sperm cell, which unites with a
larger egg cell hidden in the ovary. This process is called
fertilization and results in the growth of the fertilized egg
into an embryo or baby plant. Only seeds with live
embryos will grow into young plants. It is thus seen
Explain how a bee might carry
pollen from one of these flowers
to another.
264 LIVING THINGS IN THEIR ENVIRONMENT
'Pollen grain
that fertilization of the egg is about the most important
thing that can happen, so far as the future of the plant is
concerned, because it makes possible the growth of a new
plant after the parent
plant is dead. You may
have noticed in shelling
peas that some pods have
only a few full sized peas
in them, the places where
the other peas should have
grown containing only
little green knobs. These
are the ovules that did
not get the eggs in them
fertilized.
How Plants Scatter
Their Seeds. One other
thing must happen if a
plant is to be successful.
It must be able to scat-
ter its seeds. Plants, like
weeds, which produce many seeds and which have good
devices for getting them placed far from the parent plant
are the most successful ones. In the case of some of the
fruits which are good to eat, birds, animals, or even man
may eat the fruit and pass out the undigested seeds with
the wastes, thus giving the seeds a start in life. In some
parts of the country birds have planted rows of trees
along fences where they roosted after eating and it is no
uncommon thing for squirrels to plant pine or other trees
as they carry off the seeds to store for the winter.
SELF-TESTING EXERCISE
From the following list select those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
CccllecU
errvbrvo
•Sac, 'bears
Several
nuclei- oi\e
rwaacrest end.
o/'pollen. t,ube.=
gg cell
This is a section cut vertically through a
flower and magnified under the compound
microscope.
GREEN PLANTS SOLVE LIFE PROBLEMS 265
stars minerals water seeds
reproduce sound food air
world right blue baby
food factory holes seed roots
flowers round green right
sunlight embryo moon oblong
make sun left angular
flat stem yellow red
Like other living things plants have two big problems for
existence. They must get (1) and (2) their kind. But
green plants do not get (3) ; they (4) it. And they make
not only their own (5) , but also supply the (6) with it.
To do this they must have (7) coloring matter in their leaves
and must have a good supply of (8) for the (9) supplies
the energy to run the (10) In order to get much (11)
surface exposed to the (12) we find leaves are (13) and
placed so that usually this surface is at (14) angles to the sun's
rays. The leaf uses raw materials to make food, part of it, (15) ,
coming up from the soil by way of the (16) and (17) while
another part, carbon dioxide, gets into the leaf from the (18)
through its breathing (19)
Plants solve the problem of continuing their kind by forming
(20) These are formed in the (21) Each (22)
contains a tiny (23) or (24) plant which under favorable
conditions will grow into a new plant.
STORY TEST
HARRY TELLS How SEEDS ARE FORMED IN PLANTS
Read carefully and critically. List all the errors and suggest corrections.
Most plants have flowers, although some of them are so small
you don't notice them. These flowers form fruits which contain
seeds, some just one or two and others a lot. The queer thing is
that seeds have in them baby plants and if you plant a seed it
always forms a new plant, no matter where it is placed. But only
one seed from a fruit will grow, all the others must die.
These baby plants get into the seeds in a queer way. Flowers
have two kinds of things growing in them, surrounded by the
colored petals and green sepals. These are the stamens, little
knobby things which hold pollen and another thing in the very
center called the pistil. This holds the ovaries that later will be-
come eggs. When pollen gets on a pistil it grows a tube and then
part of the tube unites with the pistil and we have an embryo.
266 LIVING THINGS IN THEIR ENVIRONMENT
Martin Johnson
What kinds of foods do each of these animals eat ?
PROBLEM III. HOW DO ANIMALS PERFORM
THE BUSINESS OF LIFE?
What are the chief problems of animals? Unlike the
green plants they cannot make food, but must get it.
This, then, is the big problem of living. To be successful
animals must know where and how to get food. Have
you ever tried to find out the different ways in which
animals you have seen get food? Grazing animals like
sheep or cows cut the grass for their fodder and then chew
it over and over again. They do not seem to have very
hard work to get their food. But how different it is with
a bird or a fish. Have you ever watched big trout or
bass feed? They sometimes jump clear out of the water
after insects or they may make a rush at a school of
minnows and snatch one or two before they can get away.
They are hunters and have to be very active if they are
not to go hungry. A bird, like a robin, must be quick
when it sees an insect or an earthworm. A flash of the
bill and the insect or worm is gone. Watch the big yellow
and black spider as it lies in wait in its circular web.
When a fly or other insect touches the web, the spider is
awake in an instant and soon throws out sticky threads of
silk that hold the victim fast until the spider can paralyze
it with its poison fangs and then suck its body juices at
ANIMALS PERFORM THE BUSINESS OF LIFE 267
leisure. These few examples only serve to illustrate the
hundreds of ways in which animals are fitted to catch and
eat their food. The grass or plant eaters are called
herbivorous animals, while the flesh eaters are called car-
nivorous.
How Animals Are Adapted for Getting Food. If you
were to go to a museum, it would not be hard to answer
this question. You could see the lions and tigers, with
their sharp claws and teeth fitted for holding and tearing
their prey once it was caught, or an elephant, with its
curious long nose or proboscis, by means of which it seizes
its food or perhaps sucks up water for a drink or a bath,
or a snake coiled up ready to strike might fascinate you.
Birds with beaks and feet fitted for various kinds of hunt-
ing or fishing might next be seen or we might find a case
showing how insects of various sorts get their food. There
are many strange ways that marine animals get their
food which we have not even mentioned — stinging ten-
tacles by which some jellyfish or sea anemones paralyze
their prey, currents of water set up by clams or oysters
by means of which tiny plants and animals are carried to
the mouth of the creature, claws or pincers of lobsters
or crabs which seize the prey, or even in the case of the
simplest of animals the whole body wraps itself around
the food and takes it in. Wherever we go in the animal
world, the most important adaptations are those which
give the animal its chance to secure food and eat it.
Animals Are Like Machines. As we shall see later, the
food which is taken by the animal is used to enable it to do
work and to grow. Food, like coal in an engine, is burned in
the body to release the energy it contains. So the business
of living consists in changing the food after it is procured
into a form in which it can be used. This we call diges-
tion. Other activities are necessary : The digested food
must be carried to the parts of the body where it can be
268 LIVING THINGS IN THEIR ENVIRONMENT
Martin Johnson
N. Y. Zoological Society
In each of the four animals give all the
adaptations you can for food getting, pro-
tection, and locomotion.
used ; wastes must be passed
off ; and finally the food
must either be built into the
body to make new living
stuff, or else oxidized to re-
lease energy. We shall hear
more of this in a later unit.
Animals Must Repro-
duce Their Kind. If ani-
mals are to be successful,
they must leave some of
their kind behind them to
carry on after they are
dead. Eggs must be pro-
duced, and when the young
emerge, they must be pro-
tected until they can take
care of themselves. Protec-
tion of young is necessary if
animals are to be successful
in life. Birds often lay only
one Qr twQ eggg ag against
-n- /• i • i i
™&™S of CggS laid by C6r-
tain fish. But because the
ANIMALS PERFORM THE BUSINESS OF LIFE 269
bird protects and feeds its young, chances for growth
to adult life of an equal number are as good, if not better,
than in the case of the fish which leaves the young to look
after themselves. In the mammals, animals which suckle
their young, such as the cow, dog, cat, or man, the mother
not only carries the young in the body until it is ready
to be born, but also cares for it during babyhood — thus
making its chances of growing to adult life much better.
In our own case we are cared for, not only during our life
as a baby, but also for a long time afterward. Animals
which are most successful in life are those which have best
solved the big problem of food-getting, protection from
their enemies, and rearing of young.
SELF-TESTING EXERCISE
Select from the following list those words which best fill in the blank
spaces in the sentences below and arrange the words in proper numerical
order. A word may be used more than once.
swallow getting cutting
food teeth tearing
eggs nests protection
care beak claws
piercing catch suckled
grinding holding people
heads continuing adaptations
kind homes releasing
The two great problems of animals are the (1) of (2)
and that of (3) their (4) on the earth. Food (5)
largely depends upon the (6) that the animal has which enables
it to (7) and (8) its food. The (9) tell just what
kind of food an animal eats. An herbivorous animal will have teeth
for (10) and (11) while a carnivorous animal has teeth
for (12) the prey and then (13) it with teeth and claws.
You can tell from the (14) or (15) of a bird the kind of
food it eats. Adaptations for the (16) and (17) of the
young are numerous. Some build (18) , some animals hide
their (19) in places where they will be hatched by the warmth
of the sun, while in animals when the young are born alive they
arc (20) by the mother.
270 LIVING THINGS IN THEIR ENVIRONMENT
STORY TEST
JOHN SHOWS How FIDO Is FITTED TO OBTAIN FOOD
Read carefully and critically. List all the errors and suggest corrections.
Fido is my cocker spaniel. I do not think he is very well fitted
to get food, for his legs are short and he is not very fast or quick
in getting about. But I know he makes up in wisdom what he
lacks in agility. His teeth are all sharp and all pointed and some
are curved so he can hold fast to his meat. He likes meat best
of all, but he will drink milk. He laps the milk with his long
tongue. I have taught him to beg and to speak for food and I
think these are adaptations for he gets food by means of them.
His feet are rather flat and padded and his claws do not stick out
much, another adaptation so that he can steal up on his prey.
PROBLEM IV. WHAT LIVING THINGS ARE FOUND
IN MY YARD OR GARDEN?
What a Survey Would Show. If you were to make a
survey of a part of the school grounds or your own home
surroundings, you would notice that plants and animals
could be placed in two groups, those that are native to the
place and those that have been introduced from some
other places. Some weeds, grass, many trees, earth-
worms, most birds, toads, and insects would come under
the first heading, while many other trees, most of our
shrubs and flowers, and our garden vegetables would come
under the head of introduced plants.
Common Shade Trees Differ in Various Parts of the
Country. Most shade trees lose their leaves in winter and
so are called deciduous (from the Latin meaning to fade
away). In New England the elm, maple, birch, and oaks
are the most common shade trees ; in the central West
other varieties of maple and oak would be found along
with the poplars, beeches, hickories, sweet gum, and ash.
When we get beyond the Mississippi Valley the cotton-
woods, poplars, and sycamores become more prominent,
LIVING THINGS IN MY YARD 271
while in southern California we rarely find native trees in
the yard, for most of them have been introduced from
other localities. In addition, many kinds of ornamental
shrubs or bushes may be found. These plants are usually
quite low and have several stems instead of one long trunk
like a tree.
Evergreens. Most yards contain evergreens which
are often introduced because of their beauty. The term
" evergreen " means that such trees do not shed their
leaves all at once as do our deciduous trees. The ever-
greens, such as spruces or balsam firs, may usually be told
by their small needle-like leaves. The pines have straight,
tall stems and the needles come out in groups of from two
to five in a cluster. The hemlocks and balsams have
needles which come out singly but are arranged on oppo-
site sides of the twig, while the needles of the spruce come
out singly but all over the branch, like bristles on a brush.
The evergreens produce their seeds in cones and so are
called conifers.
Deciduous Trees. It would be impossible to give more
than a few hints as to how to know the common deciduous
trees. You must go to one of the reference books for
that. But some different trees can be told from their
leaves and bark. For example, the maples have their
branches opposite on the trunk and leaves sharply pointed
and deeply notched. Maple fruits are winged seeds held
together in pairs. The birches and poplars have easily dis-
tinguished outer bark, which is yellow green on the poplar
and light colored and easily peeling in the birches. The
elms are known by their graceful shape and leaves, shown
on the next page. The oaks we recognize by their fruit,
the acorn, and their much-lobed leaf. This paragraph
will give you a start. Get a good book and see how many
trees you can identify. There may be a few trees and a
good many shrubs and cultivated flowers that you cannot
The upper picture shows an oak forest with its leaves and fruit; the middle
picture shows an elm with leaves and fruit ; the lower, conifers with fruit. Which
of these are deciduous trees ? How many deciduous trees do you know ?
LIVING THINGS IN MY YARD
273
find in your book of reference. Go to a garden catalogue
for them.
Animals in the Home Grounds. You will say at first
that there are no animals in your home grounds, unless
it be your pets, dogs, cats, or birds. Occasionally you
will have a rabbit that feeds upon your lettuce, and in the
far West the gophers and ground squirrels may become
How many animals can you find in this picture ? How many can you add that are
found in your home grounds ?
pests. But if you have trees and shrubs, there are almost
certainly birds to be found nesting. You are quite sure
to find a toad or two living in the garden. A good many
more insects than are desirable are also likely to be found
feeding on the plants or shrubs. Snails and slugs feed on
your flowering plants, while earthworms, ants, and several
kinds of insect larvae may be found in the earth. Let us
see what we can learn about some of these friends and
enemies of our trees and gardens.
H. & W. SCI. 1—19
274 LIVING THINGS IN THEIR ENVIRONMENT
Spiracle
Antenna
Animals Which Harm Our Gardens. There are many
kinds of insects, mostly in the young stages, which destroy
our plants. Adult in-
sects can easily be
distinguished because
they have three divi-
sions of the body and
three pairs of legs, but
the young stages, or
larvae, harmful grubs,
or caterpillars, are not
so easy to recognize as
4 insects because they
Study this diagram carefully and then compare it
with some animal you think is an insect. Tell how have f alse legs.
you would identify an insect. The insects most
likely to be found in the home yard are crickets and grass-
hoppers, insects with chewing mouth parts and strong hind
legs used for jumping ; winged butterflies and moths, the
latter usually flying at night, both distinguished by the fact
that the wings are covered with dust-like scales ; hungry
caterpillars which are the young stages of moths and
butterflies ; beetles, heavy set insects with hard wing
covers, bees, wasps, and ants ; and the destructive bugs,
the latter distinguished by their snout-like beaks, through
which they suck the
juices of plants. ^HIHH&r-.^ell
Another group of
animals that do harm
are snails and slugs.
These animals belong
to the Same group as Snails are very destructive in gardens. The
Clams, Oysters, and mouth» on the underside, is not shown.
mussels. They are called mollusks (Latin mollis — soft)
because they have soft bodies. Most mollusks have shells,
but others, like the slug, do not have one. Some snails
LIVING THINGS IN MY YARD
275
move by means of a muscular foot, which can be seen in
action if the snail is allowed to crawl on a glass plate. The
mouth, with its sharp teeth, can be seen on the underside
of the foot. You can also see the head with its tentacles
and stalked eyes when the snail is moving about.
Friendly Animals. — Fortunately there are some
friendly animals that live in the garden. One of the best
friends is the toad. Toads are not often found in the
bright sunshine, but at dusk or on rainy days they may be
found squatted un-
der the leaves of
some plant, on the
lookout for insects.
Watch one and see
if you can find out
how he catches
them. His slimy
tongue is the
weapon and his use
of it is very accu-
rate. Toads are
vertebrates because Toads are useful neighbors. Did you ever see one
,i_ -i 11 catch an insect ?
they have back-
bones. They belong to the group called amphibia
(Latin amphi — both), so called because they pass their
lives both on land and in water. We should always
protect the toads, for they eat cutworms and other
garden pests. Occasionally harmless snakes are found
which live upon the rodents like field mice, gophers, or
rabbits. So we see even in our garden there is a continual
struggle for existence.
Some Animals Found on or in the Ground. There are
several different kinds of animals that live under boards or
stones or in the ground. Pull up a board that has lain
on the ground for some time and you will be surprised to
276 LIVING THINGS IN THEIR ENVIRONMENT
How many animals can you find and name ?
see the numbers of tiny animals there. Ants go hurrying
away, a spider or two may be found, and perhaps the
round cocoon or egg case containing a number of baby
spiders. Other near relatives of the insects are the
" thousand leggers" or millipeds, worm-like creatures with
many legs. The pill bugs are wood lice that roll up into
a ball, from which they get their name. The sow bugs
are also wood lice, but cannot roll themselves into a ball.
These are closely allied to the lobster and crayfish. They
have jointed bodies and jointed legs and belong to the
group called crustaceans.
The earthworm often makes part of the burrow under
boards and will withdraw quickly if disturbed. Earth-
worm burrows are interesting to follow, and if care is
taken in digging, you will sooner or later find its owner.
Earthworms differ from the crustaceans in not having
jointed legs, although the body is segmented or jointed.
LIVING THINGS IN MY YARD 277
Although earthworms have no eyes, ears, or feelers, they are
very sensitive to light, touch, and odors. If you do not
believe this, try some experiments with living worms and
see for yourself.
Why Birds Are Important Neighbors. Have you ever
tried to take a census of the birds in your locality ? You
must first know which birds are residents, or stay all year,
and those which are migrants and go somewhere else
part of the year. The latter usually come in the spring
and stay with us for a time.
Nests and Their Uses. Nests are indications of the
habits of the birds that build them and are interesting as
pieces of adaptive work. Some are simply loose masses of
sticks made like a platform on which the eggs are laid.
Such nests are made by crows, hawks, and the brown
thrasher. The birds which live near homes usually
make nests that are carefully lined with down, grass, or
other fibrous materials to make them more comfortable.
Most birds do not use their nests a second year, so a
collection of nests for the school museum can be made
without harm to their makers if taken in the late summer
or fall.
Wright Pierce
What can you tell about the habits of the birds that made these nests ?
JOHN JAMES AUDUBON, 1780-1851.
\ UDUBON was a born naturalist, a keen observer, and a remark-
-^- able artist. Although he inherited wealth, he soon lost all his
money and for many years wandered through the Ohio and Missis-
sippi valleys almost penniless. But during this time he was making
a wonderful collection of paintings of birds, which afterwards be-
came the illustrations for his famous Birds of America.
LIVING THINGS IN MY YARD
279
Some Birds Found in Home Grounds. Most of the
birds frequently found on the home grounds are perchers,
having four toes in front and one behind, making a foot
well adapted to perching. In this large group are found
the thrushes, which include our robin ; the wrens, little
birds with a cheery note and sociable disposition ; the
mocking bird and its relative, the catbird ; the sparrows,
all useful weed-seed eaters except the English sparrow ;
Wright Pierce Wright Pierce
What can you tell of the habits of these two birds from their photographs ?
the blackbirds, meadow larks and grackles, and many
others. The woodpeckers and flickers, with two toes
pointing forward and two backward, make up another
order, while the hawks and owls, birds of prey, are placed
in a group which has claws and beaks adapted for tearing.
How May We Attract Birds ? There are several ways
in which birds may be attracted. First, nesting boxes
may be made. The birds which frequent such houses
are the wrens, blackbirds, martins, woodpeckers, and,
unfortunately, English sparrows. Houses for wrens can
be placed near the house, for they are friendly little crea-
tures. Be sure to make the entrances too small to admit
280 LIVING THINGS IN THEIR ENVIRONMENT
the English sparrows. Bluebird and martin houses can
go into the garden either on a post or nailed to a tree.
The martin house should have several entrances because
if the bird house has only
one entrance, the English
sparrows may get posses-
sion and the martins can-
not drive them out. The
woodpecker box should be
deep, with cleats attached
below the hole so that the
bird will have a place to
light on.
Bird baths and feeding
places are other means
of attracting birds. The
drinking fountain and
baths must be so placed
that cats will not be able to disturb the birds. Feeding
boxes or shelves, on which are placed cracked corn, bread
crumbs, chopped meat, and in winter a piece of suet, will
attract birds if feeding is done at regular times.
Wright Pierce
A bird bath that is safe. Cats cannot dis-
turb birds here.
SELF-TESTING EXERCISE
Select from the following list those words which best Jill in the blank
spaces in the sentences below and arrange the words in proper numerical
order. A word may be used more than once.
high
green
wings
fangs
residents
mollusks
protect
pollen
flowers
conifers
shrubs
fins
dead
millipeds
hardy
protect
earthworms
spiders
crabs
bushy
low
soft
migrants
toads
water
destroy
insects
amphibians
deciduous
LIFE IN STREAM AND POND 281
Many different kinds of living things may be found in one's
yard. Two kinds of trees are (1) or evergreens, and (2)
trees, which shed their leaves in cold weather. Then we find
(3) , small tree-like plants having a (4) appearance.
Many forms of animals are found, (5) , which feed on garden
plants, or take nectar or (6) from the flowers ; (7) , which
live on the ground and feed on the insects ; (8) , which live in
the soil and many other small animals. Toads and frogs are called
(9) , because they pass part of their lives in the (10) Snails
and slugs, which live on plants, are called (11) because they have
(12) bodies, while the thousand leggers are (13) , so called
because of their many (14) Most important of all are the
birds which (15) the trees and plants from destructive (16)
and cheer us with their pleasant songs. Birds are either all-year-
round (17) or (18)
STORY TEST
MARGARET TELLS WHY WE SHOULD PROTECT THE BIRDS
Read carefully and critically. List all the errors and suggest corrections.
Birds are good neighbors, because they are pretty and have
sweet songs. I like the robin's note in the spring. In cold
weather I guess he stays in his nest, for I never see him. Most
birds like the robin or oriole stay in the north all the year, but a
few, like the woodpeckers migrate south to escape the cold weather.
Sparrows (except the English sparrow) are especially useful, for
they eat harmful insects. We can attract birds by feeding them,
by making bird baths, and by attracting the English sparrows and
starlings, which the other birds like.
PROBLEM V. LIFE IN STREAM AND POND
How to Prepare for a Collecting Trip. Have you ever
gone on a collecting trip to a stream or pond? If you
have, you know what fun it is and how many interesting
creatures live in this habitat. You will need a pail, a
few Mason jars with covers, and a long-handled net.
This you can make out of a broom handle, a piece of steel
wire for the frame, which can be bent and fastened into
the handle as is shown in the illustration. The net can
282 LIVING THINGS IN THEIR ENVIRONMENT
be made of coarse cheesecloth or mosiquito netting. With
this equipment you can capture all sorts of animals for
your home or school
aquarium.
Zones of Life. As
we observe life in a
stream or pond we
soon see what living
things frequent one
of several zones;
they may be in or
along the bank, in
the water, on the
water, or in the air
just over it, in or
It would be an interesting project to make a net under stones in the
like the one shown above. Why not try it ? i •, i T-I i
brook or pond. Each
zone has its own collection of inhabitants. For example,
the young stages or larvae of some insects, worms,
and little crustaceans, to be known by their jointed
bodies divided into two parts and jointed legs, will be
found in the mud or crawling on the bottom or under
stones. Fish, crustaceans, and insect larvae are in the
water. Insects will be in the air or on the surface film
of the water, while larger animals like turtles and frogs,
although they may be in any of these zones, will be
likely to be found sunning themselves on the bank.
Water plants are much more restricted to their own
particular zone. The many forms of algae, plants with
thread-like bodies or with finely divided leaves living in
the water, pond lilies with floating leaves at the surface,
and many water weeds frequent the banks, offering
shelter to insects and other small animals. In every
case, if you look, you can find many adaptations for
aquatic life. The stems are thin and long, for the plant
LIFE IN STREAM AND POND 283
is supported by the water it lives in. Leaves are either
numerous and much divided, as in plants under water, or
the leaves are brought to the surface by long thin stems,
which are supported by the water. This enables the
leaves to get sunlight. List as many other adaptations
as you can in your workbook.
How Fish Live. You will usually find small minnows
in a brook, which can sometimes be caught in your net.
The chub or dace, minnows, and sticklebacks are often
found in brooks, while the perch and sunfish are quite
often found in small ponds. If you watch a fish carefully,
you will see that it frequently opens its mouth, as if it were
biting. It is doing this in order to take in water which
passes out over the gills or breathing organs. You have
all seen the gills, red feathery structures on each side
of the head, covered by the cheek bones. These gills are
able to take oxygen out of the water. Look for clear
round areas of gravel. These are nests of the sunfish, and
if you can see one of the fish there, it is quite likely to be
a male guarding the nest. The eggs are laid in these
nests, and sometimes a lucky stroke of the net will bring
in some, which you can watch develop in the school
aquarium or in a small saucer at home.
Frogs and Turtles. Several different frogs may be
seen. The big bullfrog can often be caught with a bit of
red flannel on a hook. They are too large for your aqua-
rium. A better frog to keep is the spotted leopard frog
or the green frog. Notice how well fitted they are for
aquatic life. The slimy, streamlined body, the big webbed
feet, the eyes so placed that they can see without being
seen when they are at rest on the surface of the water.
If your trip is taken early in the spring, look for the eggs
of frogs and toads. The former are laid in masses of jelly,
usually attached to some sunken sticks or weeds near the
surface of the water. Toads' eggs are laid in strings of
284 LIVING THINGS IN THEIR ENVIRONMENT
Study the diagram carefully and then make an es-
timate of the time that elapses between each of
the stages shown above.
jelly in shallow water.
Be sure to bring in
some eggs if you find
them so you can
watch their develop-
ment.
You may also see
several different
kinds of turtles.
They make interest-
ing pets, but should
not be kept in the
aquarium, for they
will eat the other
inhabitants. If you
watch a water turtle,
you will notice that he comes to the surface after a time,
and that quite often under water he gives off a stream
of bubbles from his mouth. This shows that he breathes
by lungs, and has to come out frequently for air. The
spotted mud turtle is found in brooks, while the painted
turtle is found in shallow ponds. A snapping turtle
occasionally found. Be care-
ful if you pick him up, for he
has a long neck and sharp
jaws. Soft-shelled turtles are
common in the South and in
the far West.
Other Inhabitants. Most
brooks and ponds are in-
habited by snails. Several
different kinds will be found
living on water plants or
crawling on stones or along ,
The western painted turtle, commonly
the bottom. They make an called water turtle.
IS
LIFE IN STREAM AND POND
285
American Museum of Natural History
Turtles make good pets. You can keep
them in a pen in your yard. Sink a small
tub in the ground and give them plenty of
shade in hot weather.
excellent addition to the
aquarium and will often
lay their eggs on the glass
walls, where they can be
watched in their develop-
ment with a hand magni-
fier. Fresh- water mussels
and tiny clams are often
found. Both of these live
nicely in aquariums. Bring
in as many different kinds
as you can and try to iden-
tify them with the aid of
some of the books men-
tioned at the end of the unit.
Crustaceans which have jointed bodies and jointed legs
are also likely to be r^~~ - . , , _„_ ,^,
found. The largest
crustacean we are
likely to see is the
crayfish, which will
often be found in shal-
low, slow-running
brooks. It makes its
home in tunnels in the
banks of the stream.
It has a jointed body
covered with a hard
skeleton, with five
pairs of walking legs,
the front ones armed
with pincers, two pa irs i ^.g|
of feelers, and eyes Fresh water mussels are called clams by most
mmmfprl rm mnvahlp Pe°Ple- Notice the siphon, through which the
animal gets its food and oxygen, and the mus-
Stalks, like the lobster. cular foot, by means of which it moves.
mucct
286 LIVING THINGS IN THEIR ENVIRONMENT
The female carries her eggs on the under side of the jointed
abdomen. Crayfish must be kept by themselves, for they,
like the turtle, will eat the living things in your aquarium.
Ab.
The crayfish — (A) antennae or feelers ; (M) the line points to the mouth ; (Ch)
the chelipeds or big pincers; (E) the eyes on stalks; (CF) the caudal fin or tail;
(CP) the cephalothorax or head and body part, and (Ab) the jointed abdomen.
How many pairs of legs has the crayfish ? How many joints in the abdomen ?
Many other crustaceans will be found : rarely, small
shrimps, and more frequently, flattened "sow bugs,"
" water fleas/' and copepods. Many smaller crustaceans,
almost too small to see with the unaided eye, swarm in the
ponds, forming food for fish and in turn feeding on still
smaller animals and plants.
Many Insects Live in the Water. Many insects are
attracted to water, as they lay their eggs in it and the
young live either in the mud or water. The larvae of the
dragon fly, called nymphs, are mud-colored, strong-legged
creatures, which carry a pair of hinged jaws on the front
of their heads, which they shoot out to catch their prey.
They may often be found on the bottom of a quiet stream
and can be brought to the school laboratory. Keep them
in a separate jar, for they prey on other living things.
Another carnivorous insect is the beetle known as the
water boatman. It will even attack small fish. Many
other insect larvae live in the mud, such as the young
of the water boatman, stone fly, damsel fly, and others.
Mosquito larvae or wigglers are often found, either quiet
at the surface or wriggling through the water, and the
LIFE IN STREAM AND POND
28?
larvae of many dif-
ferent flies live in
tubes fastened to
stones. You can
learn to identify
these in any good
book of aquatic in-
sects. Some insects
live on the surface
film of the water,
while others, as the
water boatman and
water bug, swim
near the surface.
Look in Down- The life cycle of the dragon fly. How does the
ing's "Our Liv- larva catch its foods? What happens before the
ITT i i j > • f adult is hatched out ?
ing World/' if
you want to learn more about these interesting forms.
SELF-TESTING EXERCISE
Select from the following list the words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once if necessary.
fishes
adults
stems
frogs
held down
buoyed up
lizards
mollusks
a'daptations
webbed
long
flowers
larvae
divided
jellyfish
toads
crustaceans
lobsters
embryos
slimy
turtles
gills
algae
seaweed
Things which live in the water show (1) for this kind of
life. Plants have finely (2) leaves and (3) thin (4) ,
because they are (5) by the water. Aquatic animals are
likely to have (6) , fins, (7) feet, or (8) body. In
brooks we are likely to find (9)_
(10) , which lay their eggs in masses of jelly;
such as minnows or chub,
(11) , which
have to come to the surface to breathe, (12) , as snails, mussels,
or clams ; (13) which have jointed legs and bodies covered with
a hard skeleton, and many insects, both (14) and (15)
288 LIVING THINGS IN THEIR ENVIRONMENT
STORY TEST
JOHN TELLS ABOUT His COLLECTING TRIP
Read care/idly and critically. List all the errors and suggest corrections.
Our teacher wanted some living things for our school aquarium,
so I went after some. I chose a stream I knew near home. It
was sluggish and filled with sewage, but I thought this would be a
good place to find living things, particularly fish. But here I was
disappointed. There was plenty of dead stuff for food, but no fish
except a few polliwogs. I did find some mosquitoes and their
larvae, little wrigglers, that went zigzagging through the water
as if they were drunk. I also found lots of snails and a few crabs.
Most of the water plants I hoped to find were not there, but I did
find plenty of water cress which I brought home to eat. I think
it grows plentifully there because there was lots of filth for it to
grow on. It will be safe to eat after it is washed.
PROBLEM VI. LIFE IN THE FOREST AND ON
THE MOUNTAINS
Forests a Refuge for Wild Life. Some boys and girls
fortunate enough to live in the country know what it
means to take a hike in a real forest. Others may have
gone to the mountains on a holiday and remember the
forest-covered mountain sides, with their deep valleys
and canyons through which a clear stream came leaping
down. Here the fisherman might find sport in the pools
and any nature lover could see wild life at its best — squir-
rels in the trees, a mink swimming in the brook, trout
jumping for flies, and birds enjoying themselves on the
pebbly bank. The forests and mountains are the last
stand of the original life that inhabited this country before
civilized man changed it. The government has wisely
enough thrown large areas of our mountains and forests
into great national parks and forests, which will always
give the citizens of our nation a place to play as well
as make a refuge for the few of our original wild animals.
LIFE IN THE FOREST AND ON THE MOUNTAINS 289
Wright Pierce
The "Elfin forest" or chaparral. Notice the zone of larger trees higher up on
the slopes of the mountain. How do these western mountains differ from those
in the East (see page 234) ?
Zones of Life in the Mountains. Any one familiar
with the mountains of southern California knows that
they rise up out of the desert and that the lower slopes
are covered with chaparral, the " Elfin forest/' made up
almost entirely of tough shrubby growth that can exist
without much water. This growth is of great use, be-
cause it helps to hold in the soil the small amount of rain
that falls there. Further up these mountains we come to
another zone of life, big pine trees appear, and at an alti-
tude of from 6000 to 8000 feet we have forests. Still
higher the trees become more sparse and stunted until at
about 10,000 feet we come to a zone of dwarfed growth
almost like that of northern Canada. Taking the train
inland from Veracruz to Mexico City, we can pick wild
bananas at the coast and wild strawberries the same day
H. & W. SCI. I — 20
290 LIVING THINGS IN THEIR ENVIRONMENT
The diagram on the left shows the life zones on a mountain rising from the desert
in Arizona. See if you can find any of these zones in the picture at the right.
at 6000 feet elevation; while at 11,000 feet you could
have a snow fight. This change in vegetation is caused
largely by differences in temperature.
On a mountain side in the eastern United States the
forests are much denser and clothe the mountains from
base to peak. Only at an altitude of over 5000 feet do
the trees begin to get smaller. At the summit of Mt.
Washington in the White Mountains or Mt. Marcy in
the Adirondacks we do find alpine conditions with bare
rocks and a few stunted trees in sheltered places.
Forests Differ in Different Places. The forests of the
western mountains are largely yellow pines, with scattered
conifers and a few aspens or other deciduous trees. In
the East, however, we have largely mixed forests : hem-
locks, spruces intermingled with ash, beech, hickory,
birch, maple, walnut, and many other hardwoods. In
the southern states the conifers are mostly cypress and
pine, while catalpa, magnolia, locusts, and sweet gums are
added to the list of forest trees given above. Some
forests in the areas where rain is abundant are carpeted
with fern and other undergrowth, while in the dryer West
the trees are not crowded so closely together and forests
LIFE IN THE FOREST AND ON THE MOUNTAINS 291
contain park-like areas scattered here and there, covered
with grass and flowers, making an ideal place for deer and
other grazing animals.
Forests Support Many Living Things. Forests serve
not only as homes for our native birds, but also for many
other wild animals. The woodpeckers, warblers, thrushes,
creepers, and many other insect-feeding birds are found
there, as well as some of our game birds such as quail and
grouse. Forests are also the home of the few wild animals
that are left, such as deer, antelope, elk, bear, wildcat, or
coyotes. Along the streams live some of the larger gnaw-
ers, such as beavers and muskrats, while hosts of squirrels
and smaller rodents live in the trees or in the ground.
Insects in great numbers feed upon the leaves of forest
Wright Pierce
A forest of yellow pine in the Far West. Notice how far apart the trees grow.
Would you find this condition in Maine ? In Michigan ? Explain.
292 LIVING THINGS IN THEIR ENVIRONMENT
trees. Many insect larvae, as the forest tent caterpillar,
the caterpillars of the gypsy moth, the tussock moth, and
the brown-tail moth eat the leaves of forest trees. Beetles
bore in the wood or eat the roots, and scores of other in-
sects do their best to destroy our forests. Fortunately
the birds which live there feed on the insects and keep
the destruction down. So we may say the future of our
forests rests largely with our birds. If we kill the birds,
we also may kill our trees. In addition, man often does
harm by setting fires which destroy hundreds of thousands
of trees, or sheep are allowed to browse in forests and
destroy young seedling trees.
.-bark
Rh.
- -Cambium
layer-
This tree grows both inward and outward from the cambium layer. How much
did it grow last year ? How old is the tree ? How can you tell this ?
How Do Trees Grow ? If you break off a rapidly grow-
ing shoot from a forest tree, you will find it much softer
than an older branch. A cut trunk shows a series of well-
marked rings of growth. The branch or tree trunk grows
from an area just under the bark. This soft area, known
as the cambium, is a place where the cells of the tree are
rapidly multiplying in warm weather. They grow in
both directions, inward to form wood and outward to
form bark. Each winter growth slows up, and in spring it
becomes more rapid. This irregularity in growth causes
the rings of growth seen in trees. It is thus true that each
LIFE IN THE FOREST AND ON THE MOUNTAINS
ring represents a year of growth, and we can tell the
approximate age of a tree by its yearly rings of growth.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
areas dwarf bush plains
conifers pupae deserts birds
few zones no wild
trees destroy large tame
upper mixed chaparral large
lower maggots grasses larvae
Plant life on a mountainside is in (1) At high elevations
there are (2) trees, a little down there are a few (3) trees,
while still lower the forests are made up of (4) . trees. In the
Far West, where the mountains rise out of the (5) , their (6)
slopes are covered with (7) like (8) In the West the
forests are largely made up of (9) , but in the East and South
the forests are (10) growth. Forests are the last place left
where (11) animals can live and they also protect our native
(12) Many insects, particularly their (13) , live upon
forest (14) and would (15) them were it not for the
(16) which in turn feed upon them.
STORY TEST
SALLIE TELLS ABOUT A TRIP TO THE FOREST
Read carefully and critically. List all the errors and suggest corrections.
The forest I visited was not far from our house. It was largely
made up of spruce and pine trees and as the trees are scattered
every which way it is called a mixed forest. There is a brook
which flows through the woods and I have counted as many as six
or seven little fish — I think they were trout, in one pool. These
fish have a large head and a small tail, and sometimes they seem to
have little legs growing from their bodies. I also saw a good many
frogs there and some jelly-like masses with little black dots inside,
which I took to be fish eggs. In the trees I heard a good many
birds and I saw one redheaded woodpecker making holes in the
bark of a tree. I think he was after food, perhaps sap. I noticed
294 LIVING THINGS IN THEIR ENVIRONMENT
one tree had a lot of holes in which acorns were lodged. I couldn't
see how they got there, for the tree was a pine and there were no
rats near. Who can tell me what caused this to happen?
PROBLEM VII. LIFE ON THE SEASHORE
How to Equip Yourself for a Collecting Trip. If you
live near enough to the coast to take a collecting trip to
the seashore, you will be repaid by seeing examples of
life that are not found in fresh water. For such a trip
you should have a large pail, a few pint jars or wide-mouth
bottles with corks for holding specimens, a small spade, an
old knife or a small iron bar for prying off animals fastened
to the rocks, a small pair of tweezers, and, if possible, a
hand lens or reading glass.
Life Zones. Evidently the salts in the water control
the life in the environment, for the forms most found
have no near relations inland where these salts are lack-
ing. We find the environment along the shore is marked
off into zones of life ; first, an upper zone of dry sand and
rocks drenched by salt spray during storms ; next, an
American Museum of Natural History
Can you find the life zones mentioned in your text in this picture ?
LIFE ON THE SEASHORE
295
vater
OYl*
inter-tidal zone, either seaweed-covered rocks or sandy
beaches and flats; and then a third shallow-water zone
found just off shore.
Life on the Shore. The upper zone, stretching from high
tide to the grass and trees of the soil, has little life. There
are sea birds, animals like rats
or rabbits which wander in
from the fields, a few insects,
principally gray grasshoppers
that harmonize beautifully
with the sand, and great
hordes of little sand hoppers
or sand fleas, tiny crustaceans,
which constitute most of the
life. These last named ani-
mals are abundant, especially
in the windrows of seaweed
thrown up at the high- tide line.
The Intertidal Zone. The
intertidal zones may be sandy
beach, sand and mud flats,
or rocky coast. Each of these
environments houses quite
different animals and plants.
The Sweep of the tide and A salt-water "long » or "soft" clam.
j. Compare this mollusk with the one
the pounding Of the Waves shown on page 285. What difference
make life in this area hard, do you find? Would this tell you any-
A . , . , . . , . thing about the changes in habitat ?
As the tide comes in, it brings
food in the shape of tiny one-celled plants and animals
(collectively called plankton), and many animals such
as small fish, crabs, starfish, and snails come in to feed.
As the tide goes out, the flats become crowded with
scavengers, gulls and other birds, crabs and other crusta-
ceans. Even land animals, such as beetles, crows, and
rats, may come down to feed. The sandy beaches and
296 LIVING THINGS IN THEIR ENVIRONMENT
flats are the permanent homes of many mollusks, little
periwinkles, and other snails almost covering the surface
in places. Other larger snails, whelks, are found, as well
as many bivalve or two-shelled mollusks. Some of these,
like the scallops, not permanent residents, live on the sur-
face of the sand or mud ; others, like mussels and oysters,
are attached to the rocks ; while still others, like the clams,
burrow into the sand by means of a muscular foot. Some
clams have long tube-like siphons which project out to
the surface. Through the siphon the animal gets oxygen
and water containing microscopic food. (See page 295.)
Many little green or brown crabs will be found, as well as
the funny little hermit crabs carrying around snail shells
in which they have made their homes.
Life in the Sand or Mud. The sand or mud is honey-
combed with burrows of several different kinds of worms.
One of the most common is the sandworm, which has a
jointed body, each joint provided with flat appendages
strengthened with many bristles and a head provided
with horny jaws, tentacles, and four eyes. Other seg-
mented (jointed) worms may be found, as well as some
unsegmented species. Small crustaceans and burrow-
ing crabs are often seen digging into the sand at our ap-
proach, while sea cucumbers and sea urchins, both " spiny
skinned " animals, are sometimes found on the surface of
the sand.
Life on the Rocks. Along a rocky shore quite a dif-
ferent association of animals is found. Here we will find
great densely-packed communities of barnacles, a fixed
crustacean, easily distinguished by its white shell divided
into plates ; while mussels of several species are numerous,
half covered by masses of brown fucus or other seaweeds.
Often we find starfish or sea urchins, while sheltered under
rocks and in pools are the wonderful sea anemones. These
animals belong to the same group as the corals. When
LIFE ON THE SEASHORE
297
American Museum of Natural History
Would you expect to find any living things in the area shown in the left-hand
picture ? If so, what plants and animals ? Where would they be found ? Where
would you expect to find the animals shown in the right-hand picture ? To what
groups of animals and plants do they belong ?
they are extended, they look like great red, brown, or
yellow chrysanthemums. When touched, they close up,
pull in their colored tentacles, and look like a lump of dull-
colored mud. Tidal pools are rich finds, and one can watch
the living creatures there by the hour, discovering new
forms of life at every turn. Small fish, several species of
crabs and other crustaceans, tube-building worms, dense
masses of tiny animals that are close relations to the sea
anemone as well as numerous varieties of starfish and sea
urchins are likely to inhabit most tidal pools. Why not
make a list of all the forms found in a single pool as a
project or report ?
Along a rocky shore many interesting new forms will be
found by turning over flat stones. Here beautiful leaf-
like flat worms are often found. These can be put into
a jar of salt water, where they will swim with a slow un-
dulating motion. Beautifully colored naked mollusks with
projecting gills are sometimes found. Of course, the rocks
are covered with delicate red, brown, and yellow seaweeds.
How many of the forms of plant life shown here have you ever seen ? Make a
list for your workbook, telling where you saw each form you mention.
298
,
'ANIMAL
LIFE
How many of the forms of animal life shown here have you seen ? Make a
similar list to that mentioned on the opposite page.
300 LIVING THINGS AND THEIR ENVIRONMENT
Life in Shallow Water. In the shallow water and on
the bottom near the coast are found hosts of other plants
and animals. Kelps, eel grass, and other sea plants float
and wave in the water, making an ideal hiding place for
small fishes, crabs, lobsters, starfish, and numerous other
small animals. Many
starfish and sea ur-
chins, as well as barna-
cles, snails, mussels,
and other mollusks,
may be found. A most
interesting project
would be to make a
list according to zonal
distribution of all the
forms of life you can
find on a trip to the
shore. Remember such
American Museum of Natural History a fa^ jg fo^ taken On
Life in a tidal pool. How do you account for the ,-• . ,.j
differences in appearance of the sea anemones ? the Outgoing tide, and
to be really successful
you should have a very low tide. Dress warmly, but with
old clothes, for you will get dirty and wet. Have with you,
if possible, a good illustrated book on sea life.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
mosses
birds
anemones
segmented
frogs
snails
life
jump
scallops
dead
insects
flat
fish
polliwogs
burrow
crustaceans
robins
algae
owls
mollusks
cucumbers
LIFE ON THE SEASHORE 301
Life along the seacoast is divided into zones. The upper zone
above high tide has little (1) , a few (2) , (3) , and sea
(4) The zone between high and low tide is teeming with
life. On the rocks are found many (5) , mussels being the
most plentiful, while different kinds of slow moving (6) are
also found there. Clams (7) in the sand while other mollusks
like (8) or (9) live on its surface. Many worms, both
(10) and smooth, also live in the sand. Sea (11) are in
the tidal pools, along with small (12) , many (13) , seaweeds,
and mollusks. Under stones we find (14) worms and on the
rocks many forms of red, brown, or yellow (15)
STORY TEST
DICK TELLS ABOUT His TRIP TO THE SHORE
Read carefully and critically. List all the errors and suggest corrections.
Several of our class organized a trip to the shore last week. We
consulted the tide tables and found high tide was in the afternoon,
so we went then. We went to Rocky Point and found the water
calm so we could get out on the rocks. They were mostly under
water and covered with seaweeds, so we couldn't find many living
animals. I fished for a while and got some small fish and a big
crab. I saw some gray grasshoppers on the rocks and lots of gulls
appeared to be catching them. I also saw millions, I guess, of
little sandhoppers just above the high-water mark on the rocks.
But on the whole I should say there were not many kinds of living
things on the beach or rocks. This doesn't agree with our book;
I wonder why.
THE REVIEW SUMMARY
This unit will be a little difficult for you to make a summary on
because much of the material has to do with ways in which you can
identify the plants and animals in certain localities. But there are
some big ideas or generalizations which we can make. See if you
can add any to the list that follows :
1. Living things respond to stimuli and adjust themselves to
their surroundings.
2. Living things can change food into living matter.
302 LIVING THINGS AND THEIR ENVIRONMENT
3. Living things are made up of cells.
4. Living things come from other living things.
5. The kind of living things found in a given place depends
upon the environment.
6. Certain plants are always associated with certain animals
in a given environment.
7. Green plants manufacture food for animals.
Before making your review summary, test your knowledge of
the facts of the unit by checking over the text so as to be sure you
know the facts underlying the generalizations. Then, using the
generalizations, the material in the text, and everything you have
read, seen, or done yourself, make a summary outline for your
notebook. This outline you may use when you make a recitation.
TEST ON FUNDAMENTAL CONCEPTS
Make two vertical columns in your workbook. Head one CORRECT
and the other INCORRECT. Under the first place the numbers of all state-
ments you believe to be correct. Under the second place all the numbers
of the statements you believe to be incorrect. Your grade = right answers
X2.
I. Living things : (1) differ in different environments; (2) have
adaptations which enable them to live under certain definite condi-
tions ; (3) are able to make some adjustments to changes in con-
ditions ; (4) cannot ever adjust themselves to changed conditions ;
(5) are not affected by their environment.
II. Living things differ from lifeless things because : (6) they
respond to stimuli; (7) they grow; (8) they feel; (9) they are
made of cells ; (10) they arise spontaneously.
III. Green plants: (11) depend upon animals for their food;
(12) use water as their only food; (13) use water and carbon
dioxide to make food; (14) need sunlight if they are to make
food ; (15) need not be green in order to make food.
IV. The following adaptations for food making can be found
in green plants : (16) the stem is long and straight, proving a good
passageway for foods ; (17) the leaves are usually placed so that
they get the most sunlight possible ; (18) in many plants stems
turn toward the light; (19) leaves are flat and the most green
material is placed on the side from which the sunlight comes ;
(20) the flowers only produce seed in the sunlight.
V. Animals show adaptations for food getting : (21) when their
eyes are placed far at the front of the head ; (22) when they are
inconspicuous; (23) when their claws and teeth are sharp and
LIFE ON THE SEASHORE 303
pointed ; (24) when they have teeth fitted for grinding ; (25) when
they feed on the young of other species.
VI. Birds: (26) like the English sparrow do much good by
eating seeds ; (27) like the woodpecker, do much harm by making
holes in trees, thus causing them to die ; (28) protect our forests
by eating harmful caterpillars ; (29) are adapted to their life by
having a large heart, light hollow bones, feathers, and front legs
modified to form wings ; (30) which are native to the home grounds
are pigeons, plover, and crows.
VII. In a stream or pond: (31) we may observe zones of life,
each having its own plants and animals; (32) the fish lay their
eggs in the mud ; (33) insect larvae live on the bottom ; (34) turtles
have to come out to breathe ; (35) frogs lay their eggs in masses
of jelly.
VIII. In the mountains: (36) we would always expect to find
the largest trees at the bases ; (37) of the southwest the big trees
are found at over 6000 feet elevation ; (38) the change in kind of
vegetation is largely due to differences in temperature ; (39) you
would expect to find buffalo and reindeer ; (40) many native insect-
killing birds make their home.
IX. You would never expect to find : (41) sea anemones in
salt water ; (42) living starfish in the upper beach zone ; (43) worms
on the rocks 'along the seacoast ; (44) crustaceans in the sand of
the beaches ; (45) sea urchins on the rocks.
X. A lynx is : (46) a crustacean ; (47) a vertebrate ; (48) a
mammal ; (49) a cat ; (50) none of these.
THOUGHT QUESTIONS
1. How many ways can you find by which a fish is fitted for
its life?
2. Why is it that sometimes the school aquarium does not keep
its "balance" of life?
3. How would you prove that without birds we could not have
gardens?
4. How could you tell the difference between an herbivorous
and a carnivorous animal ?
REPORTS UPON OUTSIDE THINGS I HAVE READ,
DONE, OR SEEN
1. Report upon an article related to some topic discussed in
this unit. The article may be from a current number of a science
magazine or from some popular science book you have read.
304 LIVING THINGS AND THEIR ENVIRONMENT
2. Ways in which a living thing depends upon its environment.
3. The chemical factory in a green leaf.
4. Just what are the important differences between a plant
and an animal.
5. Living things I have found interesting on my field trips.
SCIENCE RECREATIONS
1. Take a hike to some place where you think you can collect
living things and make a map of the locality showing where differ-
ent plants or animals can be found.
2. Take a trip to a near-by park and see how many animals you
can find feeding. Make a list for your notebook and tell just
what they eat, how they get their food, and how they eat it.
3. Take a trip to a "zoo," select ten different animals, and
make a list of all their adaptations.
4. Make a collection of pictures showing adaptations to environ-
ment.
5. Make a survey of the birds nesting in your vicinity and
locate their nests.
6. Make a tree survey of your block and make recommenda-
tions for tree planting.
7. Select a small area in your yard and study it carefully over
a period of one week. List all the living things you find, both
plants and animals. Find out, if possible, the names of the vari-
ous plants. Make two lists — native and introduced. Look for
birds. List all you recognize. Make descriptions of those you
do not know and try to identify them from some bird book. Look
under the leaves, in stems and bark, on the ground, and in the soil
for insects. Look in and on the soil, especially under boards and
stones, for other animals. You will be surprised to see what a long
list you have by the end of the week.
8. Make a bird calendar in which observations of migrants will
be kept.
SCIENCE CLUB ACTIVITIES
1. To make a collection of plants inhabiting some particular
environment, mount them and make labels telling all the adapta-
tions you can find in each.
2. Prepare a skeleton of a dog or a bird, mount it, and label all the
adaptations for life you can find.
3. Make an excursion to the shore and bring back materials to
stock a salt-water aquarium.
LIFE ON THE SEASHORE 305
4. Arrange and label the school museum, making it an up-to-date
collection of animals that live in your environment.
5. Collect and cut sections of small branches from different forest
trees in your locality. The sections can be smoothed, varnished, and
mounted with leaves and fruits of the tree, thus making a valuable
addition to the school museum.
6. How to Make a Balanced Aquarium. An aquarium can be made
by having a tinsmith make a frame of angle tin into which you can
cement glass sides and ends cut to fit. A good size is about 8" by
12" for the bottom, the sides 6" by 12 ', and the ends 6" by 8". A
waterproof aquarium cement can be purchased and the glass
cemented into place. It should be left to harden for several days
before it is used.
Stocking the Aquarium. The pond or stream you visit will
certainly have several species of water plants or algae. Green
plants that live under water are necessary in order that they provide
food and oxygen for the animals that live in the aquarium. Blad-
der-wort, milfoil, water moss, or some of the slimy pond scum
will make useful plants. Snails will act as scavengers and will
eat the tiny green algae that may form on the sides of the aquarium.
Add stones and sand for the bottom so as to give your insect larvae
a place to live and plants to root. Remember crayfish, dragon-fly
larvae, and especially the larvae of the giant water bug will eat all
living things, so do not try to keep them. Use brook or pond
water and be sure not to add city water that has been chlorinated
or you may destroy the lives of your pets. Keep records and
make observations on the doings of the vaiious inhabitants and
you will be surprised how much of interest you will find out about
the lives of these tiny neighbors whose presence many people do
not even suspect.
REFERENCE READING
Downing, E. R., Our Living World. Longmans Green, 1924.
Fuller, R. T., Walk, Look and Listen. Day, 1929.
Johnson, M. E., and Snook, H. J., Seashore Animals of the Pacific
Coast. Macmillan, 1927.
Macdougal, D. T., The Green Leaf. Appleton, 1930.
Mann, P. B., and Hastings, G. T., Out of Doors. Holt, 1932.
Mayer, A. S., Seashore Life. New York Zoological Society, New
York, 1905.
Palmer, E. L., Fieldbook of Nature Study. Comstock, 1927.
H. & W. SCI. 1 — 21
SURVEY QUESTIONS
Why do you eat different kinds of
food?
In what ways can you compare the
human body with an automobile
engine ?
Where do most foods that are used
in your community come from ?
Do the foods used in different parts
of the world vary ? Do you know
why?
Milk is a good food. Why should
we not use milk alone ?
How is food used by the body?
Do you know why foods spoil ?
Do you know how we keep foods
from spoiling ?
Burton Holmes for Galloway
UNIT XI
THE FOODS WE EAT
PREVIEW
If you could take a trip around the world, you would be
much amused to see what different kinds of foods dif-
ferent people eat. In Japan we would find fish and rice
most used as food ; in China, rice or millet, fish, and some
strange foods, such as edible birds' nests and shark fins ;
in the Philippines the natives would be found eating the
fish they catch and the native fruits and vegetables found
there in abundance ; in India, corn often takes the place
of rice and we have milk and butter used as well as many
vegetables and fruits that we know and like. The story
would be different for each country, for each would have
its own peculiar foods, but all people use food for the
same purpose that we do.
What is true of man is equally true of plants and other
animals. A plant as well as an animal may starve to
death. Ask any farmer about this. Does this mean
that a plant actually eats soil, water, and sunlight, or do
plants use foods as we do? Green plants do use foods
for the same purposes as animals do, but there is a great
difference in the way they get their food.
Do the different kinds of foods really make any differ-
ence in our growth or the way we feel? We can answer
that question by feeding white rats on different foods to
see what happens. Rats use the same kinds of food that
man does, so the results of feeding rats help to show
what the effect would be on man. Recently a series of
307
308 THE FOODS WE EAT
interesting experiments were carried out by some school
children in Texas. They chose six rats of the same size
and weight from the same litter, and tried feeding them
on the same ration of corn meal, water, and green food,
but two of the rats were given milk in addition while two
others had chile, another candy, and another a soft drink
added to their diet. The children found that "The rats
given milk grew to be larger, had finer hair, brighter eyes,
were better natured, and were more active" than those
which did not have milk. It is experiments like these
that give us some of our information about the kinds of
foods that are best for growing boys and girls.
We know that our bodies use food not only to release
energy so that we can do work, but also they help the body
to grow. Rather recently a third use of foods, that of
protecting and regulating the body, has been found. We
will later learn something about the kinds of food that do
these things.
If foods are oxidized in the body, the amount of energy
given off ought to depend on the kind and amount of food
that is eaten. This, in a general way, is true. People
who do hard physical work should eat more food, and food
that has greater fuel value, than those who lead inactive
lives. The boy or girl who plays hard needs more fuel
food than another boy or girl of the same age and weight
who stays indoors reading. People in the arctic region,
where the cold makes demands on the system and where
hard work has to be done in order to gain a scanty living,
consume much more heat-producing food than do people
living in the tropics. In our own country we eat more
food and more heat-producing foods in the winter than
we do in the summer. We have heard of people fasting
for long periods of time. In order to do this they dress
warmly or go to bed so as to prevent the body heat from
escaping. Since they do not exercise, very little energy
FOODS AND WHERE THEY COME FROM
309
is used and, therefore, they can exist for longer periods
without food than if they were living an active life.
We know that
foods spoil, but we
may not always
know the reasons for
this. We shall learn
later that there
are tiny plants
called bacteria and
fungi, which are
the cause of this
spoiling. They are
always present in
the air and will
grow rapidly when-
ever the conditions
of moisture, tem-
perature, and food
are favorable.
How are the human body and an engine alike?
Would these boys need the same amount of food
if they were studying ?
PROBLEM I. WHAT ARE FOODS AND WHERE
DO THEY COME FROM?
Where Do Foods Come From? Make a list of all the
different kinds of food you have eaten in one day, including
water, salt, pepper, etc. List the foods which come from
animals or plants, and those that do not come from living
things.
If we study this list we notice several things. First,
that many more foods come from plants than from
animals. Second, that we have a greater variety of plant
than of animal food and that we use more parts of plants
than of animals. In animals, the part we call meat is
really the muscle of the animal. The fat we use sparingly.
310
THE FOODS WE EAT
In shellfish, such as clams and oysters, we eat practically
all of the animal. We use mostly the muscle of scallops,
lobsters, or crabs. Milk, cheese, butter, and eggs are
animal products.
The fruit is probably used more than any other part of
a plant. Think of the millions of acres of grains such as
wheat, oats, barley,
rice, and corn planted
in various parts of the
earth! Think of the
various uses of this
seedlike fruit in mak-
ing bread, cereals,
pies, and cakes ! Think
of the many, many
people who live almost
wholly on rice or corn,
with a little meat or
fish! Then there are
the apples, pears,
How many more fruits and vegetables can you plums, grapes, VariOUS
add to this group? Make lists and place them kindg of berries and
in your workbook.
citrus fruits that we
all know so well. Millions of dollars7 worth of fruits
are raised every year in this country. Seeds, such as
peas and beans, and nuts form other important sources
of food. Perhaps next in importance are roots and
underground stems of plants, such as the potato, beet,
carrot, and turnip. In some countries stems also furnish
important foods. Sugar from the sugar cane, sago from
the sago palm, and asparagus are examples of such
kinds of food. The leaves of some plants are cooked
for greens, such as beet tops or spinach, while others
furnish the basis for our salads, as lettuce or romaine.
Some vegetables, as onions or artichokes, are formed of
FOODS AND WHERE THEY COME FROM 311
thickened leaves. Buds and flowers are occasionally
used, cauliflower and Brussels sprouts being the most
common examples.
Green Plants Make Food. We have said that green
plants make the food of the world. This is very easy to
show by means of an experiment. If we take a healthy
plant, such as a common geranium, and put it in the dark
for at least 24 hours, it will use up all the spare food made
in the leaves. While it is still in the dark, we may fasten
pieces of cork on some of the leaves. These pieces of
cork must be so placed that both sides of the leaf are
covered. We will then put the plant in strong sunlight
for a few hours. Later we can pick off the leaves which
have the cork on >
them, remove the
cork, and boil the
leaves. Then we
place them in hot
methyl alcohol.
This takes the green
coloring matter out
of the leaves and
makes them appear
to be white. If we
now wash the leaves
carefully and then
put them in an
iodine solution,1 we
will find that the
area covered by the
cork remains white while the rest of the leaf turns dark
blue or black. Iodine is a test for the presence of starch.
1 Made by adding a few crystals of iodine to 95 per cent alcohol, or by
adding to one gram of iodine, two thirds of a gram of potassium iodide
and then adding enough 35 per cent alcohol to darken to a brown color
this takes
rtva.te.r- cxna. expose "Co sun out the
•start VitVz a plant that
. has been in a ctark
closet for 24 hours.
green
312 THE FOODS WE EAT
This experiment shows that the part of the leaf which
was in the sunlight made starch. Experiments show
that starch is always found in leaves that are exposed to
sunlight. We can also show that it is not found in
leaves that have been left in the dark for some time or
in such parts of leaves as have been covered.
Other food materials are also made in the leaf, but the
processes are very complicated. After foods are formed
in the leaf, they have to be circulated through the body
of the plant in order to be used by or stored in the fruit,
the seed, the stem, or the root.
What Kinds of Foods Are There ? If you were to ask
a chemist about foods, he would tell you that they were
composed of chemical elements put together in different
proportions. Such a classification would give us foods
like starches and sugars, which are called carbohydrates
because they contain carbon, hydrogen, and oxygen ; fats
and oils, which are composed of the same elements as the
carbohydrates, but in different proportions ; proteins,
which contain nitrogen in addition to the other three
elements ; water, minerals, and certain regulative sub-
stances of a complicated chemical nature called vitamins,
of which we shall learn more later. If you were to ask the
school nurse or a nutritional expert to classify foods, she
would tell you that foods may be classified as fuel foods,
body-building foods, and regulative or protective foods.
SELF-TESTING EXERCISE
Select from the following list those words that best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
protective green body starches
sun's liquids yellow fuel
living vitamins inorganic building
carbohydrates dead water air
HOW DO WE USE FOODS? 313
organic sugars moon's stars'
destroying gases minerals fats
proteins germ soil fluid
Foods which come from living things are called (1) foods,
while water and mineral salts are examples of (2) foods.
(3) plants are said to provide food for the world because in
the long run the (4) energy, acting on the (5) coloring
matter in leaves, causes (6) or (7) to be made there from
certain raw materials found in (8) and (9) Foods are
classified by the chemist as (10) , fats and oils, (11) ,
water, (12) , and (13) The nutrition expert classifies our
foods as (14) foods, (15) building foods, and (16) or
regulative foods.
STORY TEST
JULIA FINDS THE STUDY OF FOODS EASY
Read carefully and critically. List all the errors and suggest corrections.
I have found this problem on foods and their sources interesting
and easy. Many of the facts we know already, for example :
Those foods we get from the ground as salt, potatoes, and carrots
are mineral foods ; those from plants as corn, apples, and wheat
are plant foods; and those from animals as eggs, lamb, and beef
are animal foods. Milk and vegetables which have an abundance
of mineral salt in them are inorganic foods. The fruits, as oranges,
bananas, berries, corn, potato, and wheat, are the most-used part
of a plant. However, the roots of plants are very important
plant foods, among these are the beet, potato, turnip, onion, and
peanut.
Plants make food out of the raw materials they take up from
the earth through the roots. The water from the soil brings
carbon dioxide and mineral salts up to the leaves, where sunlight
causes chemical changes which result in plant foods. One of
these plant foods is sugar, and the test for it is iodine. If food has
a drop of iodine solution placed on it and it turns blue, there is
sugar in it. The important classes of foods are sugar, fats, proteins,
mineral matter, and vitamins.
PROBLEM II. HOW DO WE USE FOODS?
People Live on Foods from Their Own Environment. It
is interesting to see that through the ages, long before
people knew anything about the chemical composition of
314
THE FOODS WE EAT
foods, people were strong and did much hard work, al-
though many of them died young. They may not have
known why this or that food was good or bad, but we
know that they ate different kinds of foods and they ate
what was most abundant in their own environments.
The Indians lived on fish, fresh venison, or birds with some
wild fruits or nuts ; the Arab, on dates and figs, grasses,
and meat of goats or sheep ; the early colonists on such
foods as they could bring with them on ships, but soon
supplementing these things with fresh meat from the
forests and with corn, which they grew in their little
clearings.
A Varied Diet Important. Not only did people eat
what was easy to get, but they ate a variety of foods.
This fact was their salvation. Scientific experiments
Wright Pierce
Do you think you could prepare a well-balanced meal from the food in this
picture ? Are there any foods shown that you would not change ?
HOW DO WE USE FOODS?
315
tried with large numbers of people show one thing very
plainly — that a varied diet is most important. We need
foods of all kinds. In order to keep well, work, and grow,
we must have protective foods, growth foods, and fuel
foods. These foods are usually found plentifully all
about us no matter where we live. So for this reason
people have been able to get along pretty well in the past,
even though they did not know much about the reasons
for eating certain foods.
Green Vegetables Important. In the days before
refrigeration was known, the late winter found the stock
of vegetables getting low and no green food was left.
People began to be ill, they were unable to resist disease,
and went to the doctor or the drug store for spring bitters
or blood purifiers. As spring came on, they began to
feel better and attributed their improvement to the medi-
cines. In reality it was the change in diet, brought about
by the fact that green vegetables and salads were again
available.
Fuel Foods. Your body is like an engine because it
does work and uses fuel. Certain kinds of food burn
better than others. You can prove this by actually
burning a piece of bread, some fat, and a piece of meat
FOODS RICH IN STARCH
SUGARS
FOODS RICH IN FATS
AND OILS
Cereals
Sugar
Fat meats
Wheat (bread)
Granulated
Salad oils
Corn
Pulverized
Olive oils
Rice
Maple
Lard
Oats
Corn sirup
Peanut butter
Fruits
Beet roots
Eggs (yolks)
Most vegetables
Molasses
Some fish
Macaroni
Honey
Butter
Potatoes
Ripe fruits
Nuts
Cornstarch
Cream
316 THE FOODS WE EAT
or fish. You know the fat will burn best. Fats release
about twice as much heat as do either carbohydrates or
proteins. But the carbohydrates do make excellent
fuels, and in addition, they are much easier to digest than
the fats. So we say that carbohydrates and the fats
and oils are the heat- and energy-producing foods.
How about Alcohol ? A number of years ago a very fa-
mous scientist in this country made a series of experiments
to see whether alcohol could be used in the body as a food.
He reasoned that because it had the same chemical ele-
ments (CHO) as did other carbohydrates, that it ought
to be oxidized like other foods. After these experiments
he found that some of the alcohol was oxidized and ap-
parently in small amounts it was used as a food. But he
also found that it was a very poor food, for it acted like a
poison as well. Glycerine, iodine, and many other poisons
are oxydized in the body, but they cannot be said to be
good foods. As one doctor puts it, the inedible mush-
room called the deadly amanita contains a poison. It is
made up of almost exactly the same amounts of food ma-
terials as is found in the edible mushroom, but you would
not eat the deadly amanita. Why should you take al-
cohol if the case is parallel ?
How about Candy? Since sugar is a fuel food, we
might well ask if candy eating would not be a good way to
release energy in the human body. But pure sugar,
although it is a good fuel, does not contain any of the
mineral and regulative materials found in fruits or cereals.
If we would take candy as a dessert along with other
fuel foods, it would be useful. But unfortunately candy
eating becomes a habit, and not only do we eat it between
meals, thus spoiling our appetite, but many boys or girls
substitute it for their school lunch, thus depriving the
body of better fuels. In one large high school it was esti-
mated that the members of one class were eating enough
HOW DO WE USE FOODS?
317
candy in a year to equal five times the weight of each
boy and girl in that class. If you want to keep that school-
girl complexion, substitute sweet fruits for candy.
Growth Foods. But the body grows and has to repair
itself. Cells multiply in number as we grow in height and
weight. They
must be made
out of some-
thing. Chemi-
cal analysis of
the living stuff
out of which
the cells are
formed shows
it to be a very
complex sub-
stance made up
chiefly of car-
bon, hydrogen,
oxygen, and
nitrogen, with
Are you a candy eater? If so, why not figure out how
many pounds you eat in a year, and insert the results in
your workbook ?
a much smaller
amount of sev-
eral other ele-
ments. The carbohydrates contain the elements carbon,
oxygen, and hydrogen, but the proteins contain in addi-
tion the element nitrogen. Evidently then, living matter
can only be built out of proteins, for the other foods do
not contain this necessary element. This is why we call
the proteins growth foods. Examples of such foods are
lean meat, peas, beans, eggs, cheese, fish, and nuts.
The Protective or Regulative Foods. The human
machine is not foolproof and will not run efficiently with-
out intelligent care. Most of us eat what we like, without
thinking very much of its effect on our bodily comfort.
318 THE FOODS WE EAT
But sooner or later, if we are careless, we pay the penalty,
sometimes in loss of "pep," sometimes in indigestion, or
during constipation, or even loss of weight and vitality.
The last few years science has made wonderful progress in
scientific discoveries about foods, and the most interest-
ing are those about the vitamins, substances which are
necessities for bodily growth and health. It has also been
proved that certain mineral substances found in milk,
water, and other foods are also necessary for health. Such
foods are called protective or regulative. It has taken a
good deal of experimentation, both with animals and man,
to learn all we have about these wonderful substances,
and we are finding out more every day.
The Vitamins. The vitamins are called after letters of
the alphabet, A, B, C, D, E, and G. Vitamin A has been
found to aid us in resisting colds, pneumonia, tuberculosis,
sinus infections, and the like. It is a resistance-building
vitamin and also promotes growth. It was first dis-
covered when its absence caused an eye disease in rats
and other animals as well as interfering with the body
activities. Vitamin A is found abundantly in kale, spinach,
turnip greens, and other leafy vegetables, such as cabbage
and lettuce, in vegetables containing yellow pigment,
such as carrots and yellow corn, and in butter, oils, eggs,
and the fat of milk.
Vitamin B also helps growth and seems to aid in build-
ing up the nervous system because its lack causes a nervous
disease called beri-beri. This disease is very prevalent
among people of the tropics whose diet consists largely of
rice. Vitamin B is found in vegetables, such as asparagus,
cabbage, wheat germs, and tomatoes ; in yeast and liver,
whole cereals, and milk.
Vitamin C is most common in citrus fruits, such as
oranges and lemons, in many other fresh fruits, and in
milk, It helps the growth of bone and the teeth and
HOW DO WE USE FOODS?
319
prevents scurvy, a disease which used to be very prevalent
on sailing ships.
Vitamin D has been called the sunshine vitamin because
it has been found that the ultra-violet rays of the sun
builds this vitamin in the various food substances and in
our own bodies. It is found in cod-liver oil, in canned
vitamin B
prevents beri-beri
bunds resistance against
respiratory diseases a
prevents «ye disease.
§-'. -pravents sever v
'
vitamin G or PP
prevents
pellagra
prevents- sterility
in rats /'
Read your text carefully and refer to the tables on pages 328-329. Then make
a list of all the foods you have eaten in the past 24 hours and check each for the
vitamins they contain.
salmon, butter, yeast, egg yolk, and milk. Vitamin D
helps to build bones and teeth and prevents rickets, a
disease in which the bones lack the proper amount of
mineral material.
Vitamin E is found in grains, milk fat, and some meats.
Experiments with rats have shown it to be concerned
with reproduction, but we are not sure what its effects
on man are.
320 THE FOODS WE EAT
The latest addition to the list of vitamins is vitamin G,
or PPy as it is sometimes called. This vitamin is found
in milk, yeast, lean meat, and some other foods and is
believed to prevent pellagra, which has been known in
many parts of the South, where people lived, during the
winter, on a restricted diet of corn meal, molasses, and
fat pork.
The Value of Bulky or Coarse Foods. Vegetables have
another value besides that of giving a source of vitamins.
It has been found that roughage or coarse, fibrous, and
indigestible parts of foods may be of great value in stimu-
lating the lower part of the food tube to pass out the
wastes left there. Frequent movement of the bowels is
necessary for health, because the waste material kept in
the body passes off poisons, which cause us to lose our
"pep" and feel constantly tired and out of sorts. Such
bulky foods are (a) cereals from which the outer coat or
bran has not been removed ; (6) vegetables such as cab-
bage, lettuce, celery, onions, parsnips, turnips, and the
skin of potatoes ; (c) fruits such as apples, prunes, pears,
peaches, raisins, and all fruits in which you can eat the
skins.
Values of Fruit in the Daily Diet. There are a good
many reasons why we should eat plenty of fresh fruit.
In the first place, fruits give us a much better source of
sugar than candy because one can satisfy the craving
for sweets without danger of overeating. They are good
sources of our essential mineral elements and they also
contain vitamins A, B, C, and G. We have already said
that they help prevent scurvy, and that certain fruits
help prevent an acid condition. Fruits also give flavor and
palatability to diets and have a laxative effect, thus aiding
in elimination of decayed material in the lower bowels.
Rather recently fruits have been found to help prevent
decay of the teeth. All of these reasons and more can be
HOW DO WE USE FOODS?
321
Wright Pierce
Classify the foods shown here with reference to the vitamins they contain. Can
you suggest additions for your own environment ?
given which show the reasons for eating fresh fruits at
least once a day.
Water as a Regulative Food. Have you ever stopped
to think how important water is to living things ? Seeds
cannot sprout and plants cannot grow without it : all
animals are dependent upon it and soon die if their supply
is cut off. The human body is over 65 per cent water.
Body cells cannot do their work without it, for chemical
changes cannot take place unless water is present. Water
usually contains mineral salts which are necessary for life.
It helps regulate the temperature of the body, it helps
dissolve foods so they may be absorbed by the cells, and
it aids in the passing off of wastes from the body. Al-
though we take a good deal of water into the body with
our foods, for example, in fruits, milk, and other beverages,
it is a good plan to get the habit of drinking 5 or 6 glasses
H. & w. sci. i — 22
322
THE FOODS WE EAT
of water a day, especially upon arising and between
meals.
The Value of Minerals in the Diet. A chemical analysis
of the human body shows that it is made up of about 72
per cent oxygen, 13.5 per
cent carbon, 9 per cent
hydrogen, 2.5 per cent
nitrogen, and about 3 per
cent of various mineral
salts. Chemically, then,
the body is composed of
the same substances as the
food on which it feeds.
Mineral salts, although pres-
ent in such minute quan-
tities, have been found to
be absolutely necessary for
life. If the body does not
get sufficient iodine, the
thyroid gland, found in the
front of the neck, is likely
to enlarge and form a goiter.
Iodine is found in some
natural drinking water and
Everything that is alive or has had life
contains some water. Make a list of
foods that you think contain a large
amount of water.
in
others. It is also
in foods such as
clams, oysters, and fish that
come from the ocean.
Lime or calcium is needed for building bones and carrying
on certain processes in the body. For example, without
the presence of calcium our blood would not clot, and
we might bleed to death from even the slightest wound.
Milk, carrots, and some fruits, especially prunes and
oranges, contain a good supply of calcium. Iron is found
in the red blood cells, and lack of it causes people to
HOW DO WE USE FOODS?
323
milk cheese Txittermilk cauliflower
bcaT?5 celery s/rap
sources of fboct CctlcUtm
Of what use is calcium to your body ?
Redrawn from Hygeia
become anaemic.1 Iron cannot be used as well by the
body in the form of medicine as when in the food. It
is found in spinach, string beans, cabbage, egg yolk, beef,
and prunes, and to a less extent in carrots and other
vegetables and fruits. Phosphorus and sulphur are both
necessary in the living matter of the body, and sufficient
amounts can usually be obtained from meat, fish, and eggs.
Sodium and chlorine are also necessary parts of living
material, and are obtained from our table salt which forms
a part of the daily diet. Many of the most important
body actions, such as the beating of the heart, the con-
traction of the body muscles, and the work of the nervous
system, appear to depend, to some extent, upon the
presence of these different salts in our blood.
Someone has said that the body contains sufficient fat
to make seven bars of. soap ; enough sulphur to rid a dog
of fleas ; enough iron to make a good-sized nail ; sufficient
magnesium for a dose of magnesia ; enough lime to white-
wash a chicken coop ; enough phosphorus to make 2200
match tips ; sufficient potassium to explode a toy cannon ;
1 Anaemic (d-ne'mlk) : affected with a deficiency in the red corpuscles of
the blood.
324
THE FOODS WE EAT
QLii
Sulphur* iron, magnesium,
lime *pteosptaoru$ ^potassium
What does this cartoon sfiow ?
and enough sugar to fill a shaker. In the form of the
chemical substances out of which it is made, the body
could be purchased for less than a dollar. But as a living
being, man's value cannot be estimated in dollars and
cents. For who knows what boy or girl who reads these
lines may not make discoveries that will save human lives
and alleviate human suffering. Such values cannot be
estimated.
The Perfect Food. However, the building and repair of
the body is not so simple as this. Living matter contains
very small amounts of mineral salts. Such salts may be
obtained from vegetables and cereals. But the most
important body-building food is milk. We lived on it
when we were babies and that is the most rapid growth
period in our lives. Milk should always form part of the
day's food supply. Not only does it contain proteins,
fats, and carbohydrates, but it also has small quantities
of lime and other minerals. In addition milk contains
HOW DO WE USE FOODS?
325
most of the protective vitamins. The experiment shown
indicates the value of milk in the diet. Children should
have at least one quart of milk a day.
grams
80
1O 15 2O 25 3O 35 <4O 45 So
What does this demonstration show ?
Demonstration 1. Effect of Milk in Diet of Rats.
Take two white rats of equal size. Weigh them and record
their weights. Place them in adjoining cages under the same
conditions of air, water, and sunlight. Feed one rat on a weighed
ration containing milk, bread, and cabbage. Give the other rat
the same amount of weight of bread, cabbage, and water. Weigh
each rat at the end of one, two, and three weeks. Are there any
differences in weight ? How do you account for this difference ?
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order. A
word may be used more than once.
oils
brown
protective
dairy
vitamins
coffee
fuel
regulative
citrus
vegetables
mixed
fats
meat
minerals
growth
green
green
carbohydrates
yeast
water
proteins
tea
milk
yellow
THE FOODS WE EAT
A varied diet is important for health because it provides the
body with (1) foods, (2) foods, and those which are (3)
and (4) Fats and (5) are our chief sources of energy and
hence are called (6) foods. (7) build tissues and are
(8) foods while minerals, (9) , and water may be con-
sidered as (10) and (11) Minerals needed by the body
are found largely in (12) , milk, and (13) (14) The
six known (15) are called A, B, C, D, E, and G. They are
found in cereals, (16) vegetables, (17) fruits, certain
(18) , (19) , and (20) products. Therefore if we are
to have all of these in our food, we must have a (21) diet.
(22) is a perfect food because it contains all the nutrients and
(23) and most of the mineral salts necessary for life.
STORY TEST
ELLA FINDS SHE CAN LEARN EVEN WHEN SHE Is SICK
Read carefully and critically. List all the errors and suggest cor-
rections.
I learned a lot from my nurse when I was getting over the scarlet
fever. There are three classes of foods. Protective foods which
make you strong, like spinach, which has iron ; growth foods,
like corn and potatoes, which grow in our gardens ; and fuel foods,
like coal and coke. Heat is just as necessary to run our bodies as
to run an engine. The food fuels do not burn with a flame in our
bodies but they do unite with oxygen. This happens in the lungs,
where we take in air. The best growth foods are those which
contain nitrogen. Butter and cheese are good examples of these.
There are many different vitamins, but if one drinks lots of milk
and tomato juice, he doesn't need to worry about the lack of them.
I was surprised to learn that there are more than half a dozen
different metals in the body without which we cannot live.
PROBLEM III. SHOULD EVERYBODY EAT THE
SAME KINDS AND AMOUNTS OF FOOD?
What Makes the Human Machine Go? If you were
to answer this question for your automobile, you would
say gasoline, as you would say coal or wood or gas
makes the steam engine go. From what you have already
learned you know certain kinds of foods have fuel values
for the human machine. In the locomotive the energy
PROPER AMOUNTS OF FOOD
327
ct locomotive
uses on)/ \Q%
of the bound up
energy- in Cool
Cocci
an automobile
uses 20% of
t"he bound up
energy in fuel
ctn2an,cctn.
use 33% of
the energy
in "his -food
"potatoes^
Man is evidently an efficient machine as com-
pared with a locomotive or automobile.
in the fuel is released by oxidation in the fire box, as it is
when gasoline is exploded in the cylinders of the automo-
bile. In the body the principle involved is the same, foods
are oxidized and energy
is released. But this is
done in the body cells,
the oxygen which re-
leases the energy being
taken in when we
breathe.
The Energy Values
of Food Can Be Meas-
ured. It has taken a
good many men and a
large number of experi-
ments to prove that different foods have different fuel
values. Just as in measuring distance we use the inch or
the foot as a unit of length, so we use a unit of heat called
the Calorie. This is roughly the amount of heat needed
to raise the temperature of one pound of water 4 degrees
Fahrenheit. Thus it became possible to estimate exactly
how many units of heat were locked up in given amounts
of different kinds of foods. It has been found that a
given weight of fat will furnish about twice as many
Calories as the same weight of carbohydrates or proteins.
Should We Count Our Calories? After knowing the
number of Calories in different foods, the next step was
for scientists to find out the Calorie requirements of the
human machine. As you can see, these requirements would
not always be the same. Any one who does hard work
requires more energy-producing foods in a given time
than when he is sitting quietly at home. An adult resting
quietly in bed needs only from 1500 to 1800 Calories a day,
depending on his weight, while the same man, doing hard
muscular work, would need at least 4000 Calories a day-
328
THE FOODS WE EAT
MINERALS
VITAMINS
WT.
GRAMS
CALOR
IES
WT.
FAT
GRAMS
WT.
CARBO.
GRAMS
WT.
PROT.
GRAMS
CAL-
MUM
PHOS
PHOR
us
IRON
A
B
c
0
E
BEVERAGES
toco*
1 cup
255
240
12
24
9.5
X~XX
XXX
x
XXX
XX
x
Grape Juice
Icup
199
200
50
X
X
XX
XX
XX
XX
Orange Juice
1 cup
232
100
25
X
XXX
XX
XXX
BREADS
Coffee cake
3*3x4"
117
333
12.08
48
8
X
X
X
Muffins, graham
1 large
78
200
3.5
35
6.5
X
XX
X
X
X
Waffles, plain
1 6"diam.
26.7
100
4
12.5
'73.5
X
X
X
X
Rolls, French
1 roll „
36.8
100
1
20
3
X
X
X
Ham sandwich
1 slice 2x4 x|
39
200
14
13.7
5
x
X
X
Lettuce and tomato
sandwich
1 slice 2x4^
59
108
6
11
2
X
X
X
XX
X
CAKE
Gingerbread
1x 1/3x2f'
31
100
2
18
2
X
X
X
X
White
l^xZSl"
42
135
5
16
3
X
X
X
CEREALS
Farina *
\ Wip
170
100
.5
21
3
X
X
XX
Oats, rolled *
1 cup
280.5
100
1.83
16.67
4.2
X
XX
X
x
XX
X
Wheat, shredded
1 bfe.
27.4
100
.49
20.59
3.51
X
XX
X
X
XX
X
CRACKERS
Saltines
6
23
98
3
15
2.4
Uneedas
4
28.4
105
2.3
19
2.5
FATS
Butter
1 Tbsp.
13
100
11
.13
XXX
X
X
X
Olive Oil
1 Tbsp.
11.11
100
11.11
FRUITS
Apple §
1
212
100
.64
23
.64
X
X
X
XX
Canteloupe §
1 4^'diam.
510
100
24
1.5
XX
XX
XX
x
Figs, dried
iH large
31
100
24
1.4
X
XX
X
X
Oranges §
1 large
268
100
.3
23
1.61
X
XX
X
XX
XXX
Peaches, fresh §
3med.
290
100
,.3
23
1.5
x
X
X
XX
Prunes, stewed
2&2T. juice
60
100
24
.5
X
X
XX
NUTS
Brazil nuts
2 nuts
15.5
100
9.5
J
2,5
XX
Peanuts, sh'l'd
' "'
single nuts
20-24
18.2
100
7
4.5
4.69
X
x
x
XX
XX
PIES
Apple
4^'arc
136
300
13.8
42
2.25
X
x
x
Custard
4"arc
118
200
7.2
29.5
4.5
x
x
XX
XX
Lemon meringue
3"arc
85
450
13.5
76
5.8
x
x
Raisin
4^'arc
85
256
CO
EGGS
oz
Plain
\h
67.5
100
7.09
9.05
x
x
X
XXX
XXX
X
x
x
FISH
Creamed codfish
Mackerel, broiled
4'x2xl^'
60
62
100
100
5
5
5.5
8
14
x
x
x
X
X
X
XXX
XX
XXX
Salmon, canned
^cup
52
100
6
11
X
X
X
XX
x
* Cooked
§ As purchased
PROPER AMOUNTS OF FOOD
329
MINERALS
VITAMINS
WT.
GRAMS
CALOR-
IES
WT.
FAT
GRAMS
WT.
CARBO.
GRAMS
WT.
PROT.
GRAMS
CAL-
CIUM
HOS
HOR
us
RON
A
B
c
D
E
CHEESE
American, pale
^"cubc
22.8
100
8
.07
6.5
XX
XX
XX
XX
MEATS
Chicken meat
1 med. slice
55
100
5.57
12.5
X
X
Beef , round pot roast
1 slice
43
88
5
13
X
X
Steak, broiled club
Lamb, chops, broiled
3*2^,, .
large2x'2xlJ£
51
46
100
100
6.5
6.5
10
10
X
X
X
X
Pork, bacon
4-0 small pcs.
14
100
9.5
3
X
X
Ham, boiled
4^"4x!^B
37
100
8
7
X
X
XX
Hamourger
2^l"diam.xl"
56
100
5
14
X
X
X
XX
Frankfort
%oflink,334"l.
40
100
7.4
.44
7.8
X
MILK
Whole
5$ cup
144.5
100
5.8
7
4.7
XXX
XX
XXX
XX
X
X
X
Malted
2 Tbsp.
25.7
100
.77
19.71
3.57
XX
XX
X
XX
X
X
X
PUDDINGS
Jread pudding
%cup
66.8
259
12
8
29
X
X
X
X
3up custard
3^ cup
210
225
9
25
10
X
X
X
XX
X
X
SALADS
Combination
^cup
90
34
.2
6
2
XX
XXX
XX
XX
XX
XX
Fruit
Jicup
87
198
16
11
2
X
X
XX
XXX
XXX
X
Lettuce, French
dressing
1 serv.
78
237
25
2
.8
XX
XXX
XXX
X
XX
XXX
XX
Tomato and lettuce
1 serv.
149
194
19
5
2
X
XX
X
XXX
XX
XXX
X
Salad Dressings
French
2 Tbsp.
24
133
15
Mayonnaise
1 Tbsp
14
100
10
.6
2
X
X
XX
SOUPS
Consomme
1 cup
214
5
.2
1
Cream of clear tomato
1 cup
240
269
19
18
7.5
XX
XX
X
XX
XX
XX
X
X
Split pea
1 cup
260
93
.04
12
10
X
XX
XX
XX
XX
X
SWEETS
Chocolate fudge
1^x^*1^
25.5
97.8
2.2
19
.5
X
X
X
XX
X
Jelly beans
tf/z large
2*3xl"
28
100
oon
H"
24
1
4
4ut bar
Suckers
ft
26
ooU
100
25
T
VEGETABLES
Asparagus
5 stalks
112
25
.13
13.82
2.07
X
XX
XX
XXX
String beans
1 cup
108
45
.32
7
2.44
XX
XX
XX
XX
XX
X
Cabbage, shred'd
1 cup
63.3
20
.19
3.55
1.01
XX
X
XXX
X
XX
XXX
Corn on cob
1 ear 6"
130
100
1
19.5
3
X
X
X
X
XX
Onions
3 or 4 med.
205
100
.62
20.33
3.3
X
X
X
X
XX
Peas, canned
/If cup
180.5
100
.36
17.73
6.52
X
XX
XX
XX
XX
Potatoes, plain
1
120
too
.12
22.09
2.64
X
X
X
X
XX
X
Tomatoes, canned
1%
442
100
.88
17.70
5.31
X
XX
X
XX
XX
XXX
Sauerkraut
3 Tbsp. heap
100
16
3
1
X
XX
X
X
XX
X
After Table* of Food Vilue*,, A. V.Bradley, Santa Barbara State Teachers College, Santa Barbara. CillL
380
THE FOODS WE EAT
thermometer |
shoeing char
More Food Needed during the Growing Period. It is
an old saying that growing boys need more food than
grown men. Experi-
ments have proved this
to be true. Rapidly
growing boys between
the ages of 10 and 15
need about 2500 Calo-
ries a day, while girls of
the same ages require
about 2000 Calories a
day, older girls requir-
ing a little more and
younger girls a little less
than this amount. The
table on page 331 gives
an estimate based on
body weight. It will be
seen that as we grow
older, we require fewer
Calories per pound.
You can see why this is
so, for after we become
adults, the body does
not grow much in size.
Food is required for
repair purposes and for
the release of energy
but not for rapid growth. So we see the hearty appetites
of growing boys and girls have a scientific basis.
Seasonal Differences in Food Requirements. Every
one knows that in hot weather we are not so hungry as in
cold weather. Have you ever stopped to think why this
is so? The body has a temperature of 98.6° F. In
cold weather more heat is lost than in warm weather,
•water for insulation.
I— :vater arounct bomb
\/armect bv burning-
of food
The bomb calorimeter is used to find out the
fuel value of food. Can you explain how it
works ?
PROPER AMOUNTS OF FOOD 331
so we need more fuel foods. Then we are likely to exercise
harder in cold weather — which means more food and
more fuel food. We find the inhabitants of the polar
regions live largely on animal fats and meats, while those
living in the tropics eat largely fruits and vegetables with
little meat. Can you give at least two reasons why this
is so?
Calories needed daily for each pound of body weight
Under 1 year 40 to 43
during 2nd year.... 40 to 43
during 3rd year.... 37 to 40
during 4th year.... 37 to 40
during 5th year.... 35 to 37
during 6th year.... 34 to 35
during 7th year.. ..32 to 34
during 8th year.... 30 to 35
during 9th year.... 30 to 35
during 10thVear...28 to 32
during llth year.. .28 to 32
during 12th year... 28 to 32
during 13th year.. .25 to 30
during 14th year.. .20 to 25
during 15th year. ..20 to 25
during 16th year.. .20 to 25
17th year and up depends on body activity
All Types of Foods Necessary. We must not think be-
cause we can estimate our needs in Calories that we should
eat only fuel foods. Body-building foods are necessary as
are regulative and protective foods. But protein foods can
be used to release energy as well as to build and repair
tissues. And many of our regulative foods, especially
vegetables and fruits, are good sources of energy. In
selecting foods the most important rule is to get a variety
of foods, for in this way we will meet all the body needs.
What Proportion of the Diet Should Be Proteins ? Ex-
periments have been made that show that as Americans
we eat relatively more proteins than many other peoples.
Most people eat too much protein food and not enough
green vegetables and fruits. It is estimated that about
332 THE FOODS WE EAT
15 per cent of our total Calories should come from proteins.
One widely used standard says a ratio of 1 Calorie from
proteins, 3 from fats, and 6 from carbohydrates is about
right, although others believe that a ratio containing even
less protein is desirable. Later we will find that not all
proteins are equally valuable for building body cells, so
the kinds of proteins as well as the amounts used are im-
portant in making up a diet. Young people need rela-
tively more protein in the diet than do older persons,
because they lead more active lives and are growing. For
such, proteins should come largely from eggs, milk, lean
meats, and whole-grained cereals.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
differ
proteins
weight
5 per cent
loses
eight
active
less
In the human machine just as in the automobile the (1)
which makes both go comes from the (2) of fuel. In the
human machine the food is (3) in the (4) of the body,
thus releasing the (5) where it is used. The unit of heat
used in measuring energy released from foods is called the (6)
It is the amount of heat necessary to raise the temperature of a
(7) of water (8) degrees (9) (10) give about
twice as much energy as do (11) or (12) The (13)
requirements of the body (14) , depending upon age, sex,
season of the year, and kind of work done by the individual. A
rapidly growing boy or girl needs (15) food than does an old
man, because the former is making new (16) and thus gaining
in (17) A person needs more (18) in winter than in
summer, because the body (19) heat more rapidly then and
carbohydrates
ounce
Fahrenheit
quiet
Centigrade
15 per cent
energy
Calories
less
fats
four
six
two
protein
cells
oxidation
oxidized
25 per cent
Calorie
gains
more
pound
50 per cent
gram
WHY DO FOODS SPOIL? 333
we are usually more (20) About (21) of the Calories
in one's diet should come from (22) or a ratio of 1:3:6 should
be maintained between our (23) , (24) , and (25)
STORY TEST
BOB MAY BE A BETTER ENGINEER THAN DOCTOR
Read carefully and critically. List all the errors and suggest corrections.
Just as it takes fuel to run a gasoline engine so it takes fuel to
run the human engine. The energy value of foods is measured
in Calories. A food Calorie is the amount of heat that will warm
one pound of water 1° F. Children of junior high school age
require less food than their parents because of their smaller size.
It is the oxidation of food that gives us heat to keep the body
temperature up to normal, 89.6° F.
Last winter I had the grip, and developed a temperature of
104° F., so the nurse said, but I think she was wrong because I
was eating less food than when I was well. It is a good plan to
check your weight by standard weight tables to see whether you
are of proper weight for the best health. If you are too heavy,
stop eating protein because they are building foods. This will
give you less variety, but the only reason for a varied diet is because
one is likely to tire of a food unless he has a change often.
PROBLEM IV. WHY DO FOODS SPOIL?
What Causes Food to Spoil. It is a matter of common
knowledge that foods become unfit to eat if they remain
for any length of time exposed to air in a warm place.
They smell badly and probably taste worse. Sometimes
fuzzy growths which we call mold appear on them. Fruit
juices usually taste as if they had alcohol in them. Many
kinds of tiny plants cause these changes.
Demonstration 2. To Show Action of Bacteria, Yeasts, and Molds.
Make a solution of molasses and water, using about one part
of molasses to five parts of water. Put the solutions in two cups :
one exposed to the air in a warm place, the other kept as near
the ice as possible in the icebox. Observe the appearance of the
contents of the two cups from day to day. Is there any difference
in the odor? Is there any difference in taste? How do you
account for these changes?
334
THE FOODS WE EAT
Moisten a slice of bread and expose it to the air of the kitchen
for a half hour and then place it in a jar and cover lightly. Keep
the bread moist and in a warm place. Place a slice of dry bread
in another jar and screw the cover on tightly so that no dust or air
may enter. Note the appearance of the bread in the two jars from
day to day. What is happening to the moist bread ? Leave it for
several days. What happens to the color of the fuzzy growth on
the bread?
When examined with the lens, the dark objects will be seen to
be filled with tiny bodies called spores. These spores get into the
air, settle on food, and develop into mold.
Expose to the air in a moderately warm location a few moist
beans in a cup. Place an equal number of dry beans in another
cup. Examine after a day or two. What has happened to the
moist beans? Do they look different from the dry beans? Is
there any odor present? What causes it?
The changes that we have just observed are caused by
tiny organisms, most of which are far too small to be seen
without the aid of a compound microscope. Hence they
Wright Pierce
This picture shows at the left two tubes of sterilized beef broth, a good substance
for the growth of bacteria. One tube was plugged with absorbent cotton, the
other left open. Both tubes were left in a warm place for a week. At the end
of this time the contents of tube A was unchanged while that in tube B smelt
and tasted of decay. How do you account for this ?
WHY DO FOODS SPOIL?
335
ccrrloon.
dio>dde
TorectcL
When yeast plants grow they break down their food into carbon dioxide and
alcohol. How would this account for the rising of bread ?
are called microorganisms. They include the bacteria,
yeasts, and molds. Bacteria multiply with very great
rapidity once they get a favorable place in which to live.
They must have dead or living foods in order to grow,
since, unlike green plants, they cannot make their own
food. Yeast and molds likewise grow rapidly when food
and temperature conditions become favorable. We know
that the action of bacteria will cause the decay of various
organisms. Sometimes they give up poisons as a result
of their growth. Some will cause milk to sour and some
will even cause diseases of various kinds. These tiny
plants, yeasts, molds, and bacteria, are always present
in the air although we cannot see them, and when they
settle upon foods and grow rapidly, they cause the foods
to spoil, changing both the taste and odor.
Yeasts and Their Work. Every one knows that yeast
under certain conditions of warmth and moisture causes
bread dough to "rise," but it is not so well known that
this condition is caused by the growth of millions of tiny
one-celled plants which were in the compressed yeast cake.
Wild yeasts occur almost everywhere and, under favorable
conditions, cause the process of fermentation to take place.
In this process the yeast plants break down the sugar
and starches on which they feed into carbon dioxide
and alcohol. Yeast plants often get into sweet foods,
THE FOODS WE EAT
especially fruits, causing them to ferment or " work "
and become unpleasant to the taste.
Molds in the Home. Mold is one of the most common
enemies of food in the home. Molds do considerable
damage, although they do not necessarily render food
unfit to eat. You may remember scraping the layer of
mold from cheese before using it. As a matter of fact,
certain cheeses get their flavor from the molds that grow
in them. Molds attack other substances besides food,
and frequently grow on shoes, leather, paper, or moist
wood.
Proof that Bacteria Are Living Things. How do we
know that bacteria cause decay ? We cannot see bacteria
unless we have a powerful microscope, but it is possible
for us to prove that bacteria really do cause things to
Preparing Petri dishes for an experiment. After the culture media is poured into
the dishes they are sterilized again to make sure no germs got in from the air
before the dishes were covered.
WHY DO FOODS SPOIL?
337
Colonies of bacteria growing on culture
media in a Petri dish.
decay. This can be easily done by a simple experiment.
It has been found by scientists that bacteria grow well in
a medium made by cooking
beef broth with either gelatin
or agar, a substance obtained
from a Japanese seaweed.
It is poured, while still boil-
ing hot, into small Petri
dishes. These are glass
dishes (see picture, page 336),
which have loosely fitting,
overlapping covers. Then
the dishes and their contents
are heated in order to kill all
life that might exist in them.
After one of these dishes has cooled, it is exposed to
the air for a very short time and then covered and put
in a warm place. Another dish containing media which
was not exposed is left as a control. If these dishes are
left in a warm place for two or three days, spots appear
on the surface of the culture medium
of the dish that was exposed.
These spots may be gray, orange,
brown, or even red in color. If a
tiny speck from one of these spots is
removed and examined under a high-
powered microscope, it will be found
to be made up of great numbers of
spirilla tiny rod, spiral, or ball-shaped bodies.
These bodies have been proven by
scientists to be bacteria. If some of
these bacteria are placed on food,
they will develop rapidly into more
Three ^ forms of Bacteria. colonieg of bacteria of the Same kind
and the food will spoil. Thus we
bacilli
Are all exactly alike within
a given group ?
H. & w. sci. I — 23
338 THE FOODS WE EAT
know that bacteria present in the air under certain con-
ditions will grow in foods and will cause foods to decay.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces*
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
grow vacuum dark dryness
light plants excessive circulation
odor moderate animals ferment
moisture vitamins decay appearance
Foods spoil because tiny (1) , yeasts, bacteria, and mold,
grow in them. Experiments have shown that (2) and (3)
temperature as well as some protein food, which is living or dead, are
all factors favorable to the growth of bacteria. Bacteria grow more
rapidly in the (4) . than in the (5) Microorganisms cause
food to spoil. Bacteria cause it to (6) , yeast causes it to
(7) , while molds may change its (8) and give it an unpleas-
ant (9)
STORY TEST
ROY MAY BECOME A BIOLOGIST
Read carefully and critically. List all the errors and suggest corrections.
I used to think it rather funny that they called bacteria and
yeast, plants when you couldn't even see them. Molds seem like
plants, at least you can see them. I made some root beer by
putting yeast into a prepared sugar solution, with some root
extracts. I could see bubbles of gas as it worked. This is the
same kind of change that occurs when bacteria in milk cause it
to sour. The same gas is given off in both cases. Plants that
we can barely see with the unaided eye are called microorganisms.
When microorganisms take root and grow in our foods, the food
may acquire a changed and more pleasing taste as is the case,
sometimes, with cheese and butter. Or it may produce an offen-
sive odor and taste. Bacteria are seen under the microscope to
have three common forms or shapes. They are rods, circular,
and ball shaped.
HOW MAY WE KEEP FOODS FROM SPOILING? 339
PROBLEM V. HOW MAY WE KEEP FOODS FROM
SPOILING?
How May We Keep Foods from Spoiling? We have
seen from what has just been said that bacteria live and
grow under certain favorable conditions. Our next
question will be to find out what unfavorable conditions
will prevent the growth of these organisms.
What Cooking Does to Foods. If we examine a bit of
raw potato under the microscope, we find that the starch
contained in it is in
little cells surrounded
by thick walls. If we
examine a bit of well-
cooked potato under
the same microscope,
we find the cell walls
have largely disap-
peared. Cooking
softens and breaks
down these tough walls and makes vegetables and meat
less tough and more palatable, thus aiding digestion.
More than this, cooking makes foods safe, as it destroys
germs and other living organisms which might grow if
taken into the body. Cooking, with the addition of salts
and condiments, improves the flavor of foods.
Home Experiment. What Temperature Is Unfavorable for the
Growth of Microorganisms ? Take a small number of beans, soak
them, and put an equal number in three cups containing small
amounts of water. Place one cup in the ice box near the ice;
another in a moderately warm place ; and the third in the oven or
some place where it is exposed to rather high heat. Be sure to keep
the amount of water in each cup about the same. Examine the
cups from day to day. In which one of the three cups do you find
the most decay? Observe the growth of mold in bread and the
growth of yeast in a molasses solution in cold, moderate, and very
warm temperatures. What results do you obtain?
Conclusion. What conditions are unfavorable for growth?
The effect of cooking on the cells of potato.
Notice the walls of the cells and the enclosed
starch grains in the uncooked potato. What
has happened in the right-hand figure ?
340
THE FOODS WE EAT
What is this girl doing ?
The Value of Sterilization. These experiments show
rather conclusively that very hot and very cold tempera-
tures are unfavorable
for the growth of
bacteria, yeast, and
molds. Most bac-
teria are killed after
boiling for ten
minutes, or exposure
to dry heat of 212°
for about the same
length of time. Heat-
ing substances for a
long enough period to
kill all bacteria is
called sterilization. It is a process used in canning vege-
tables and fruits. We cook our foods, and we put them
in cold storage or ice boxes in order to keep them. Other
experiments made with bacteria show that bacteria must
have moisture in order to grow ; that the bacteria must
have a moderate temperature ;
and that food substances must be
present. Proteins seem to be
the substances most favorable to
their growth. It has also been
found that light is unfavorable
and darkness is favorable for
the growth of many microor-
ganisms.
Milk and Bacteria. Milk is
not only a perfect food for man,
but it is also a perfect food for
bacteria. Since it is one of our
most important foods, and one
that easily spoils, great care must
.•water
level
jniltc
\ heab /
£- £
one for home use?
HOW MAY WE KEEP FOODS FROM SPOILING? 341
be taken in handling it so that dirt and disease germs
do not get into it.
Milk should be kept cold and covered, from the time
it leaves the cow until the time it is used. Since milk
is the best food for young children and since a baby's
digestion is easily upset, we must keep milk free from harm-
ful bacteria. To kill bacteria without injuring the milk,
a process known as pasteurization is used. This is named
after the great French scientist, Louis Pasteur, who first
used the process to kill harmful organisms in wine.
Demonstration 3. How to Pasteurize Milk.
Fill each of two test tubes half-full of raw milk and plug both
tubes with clean absorbent cotton. Place one tube in a beaker
of water and heat it to 145° F. for 25 or 30 minutes, and cool it in
cold water. Set the two tubes aside so that they will both be
Galloway
Milk from this dairy is a safe food for babies. Why ? Name all the devices
which make clean milk possible.
342 THE FOODS WE EAT
under the same conditions of temperature. Examine the tubes at
intervals of 24 hours for three or four days. Note the taste and
odor of each.
Raw Milk and Pasteurized Milk. Careful pasteuriza-
tion will not harm milk, but if the temperature is raised too
high, the Vitamin C in the milk will be destroyed and thus
the milk will not be of as much value as a food. A special
grade of raw milk called certified milk is now sold in most
communities. The price is higher because of the special
care taken in producing and handling it.
A Cold Temperature Unfavorable to Bacteria. If you
will think back to the experiments on bacteria, you will
recall that cold is unfavorable for the growth of bacteria.
However, some bacteria will live in ice for a long time.
Intense cold prevents the growth of bacteria, but it does
not always kill them. We have come to make use of this
knowledge in our homes by using refrigerators. A well-
made electric refrigerator or even a good ice box will keep
the temperature below 45° F., which is sufficient to prevent
bacterial growth and will keep foods from spoiling before
they can be eaten.
Construction of the Refrigerator. The household
refrigerator is a large box with thick, heat-insulated walls,
and with doors or covers to the several inside compart-
ments. There is always one chamber for the ice or the
ice-making machine, and another with shelves for food.
These compartments are connected by tubes or openings,
so that there is a free circulation of air throughout the
entire refrigerator. The drainage pipe leads to a pan, or
to a waste pipe protected by a trap that prevents warm
air from coming in.
How We Use the Refrigerator. When air comes in
contact with ice, it gives up its heat, becomes colder and
heavier, and sinks to the bottom of the ice chamber.
An outlet below the ice allows this cold air to pass out
HOW MAY WE KEEP FOODS FROM SPOILING? 343
at one side to the bottom part of the refrigerator, where
warm food substances give off their heat to the cold air,
which is warmed and gradually rises, passing in again at
the top of the ice chamber. Thus we have a circulation
of air within the
refrigerator. The
warm air returns
to the ice which
absorbs heat in
the process of
melting and the
heat is carried off
in the water which
drips into the
drain pipe.
Electric and
Other Methods
of Refrigeration.
The application of
the cold-storage
plant to the home
is found in the
newer types of re-
frigerators which
run by electricity
or by gas. These automatic refrigerators are more expen-
sive in the first cost than ordinary ice boxes, but they have
the advantage- of being able to keep a nearly constant
temperature all the time and they are economical to run.
Since these automatic devices are colder than the ordinary
refrigerators using ice, the arrangement of foods in them
is of less importance.
A New Development in Refrigeration. One of the latest
developments in refrigeration is the use of "dry ice,"
which is solid carbon dioxide. This has the advantage of
Are the foods properly placed in this electric re-
frigerator ? Explain how the cold air circulates.
344
THE FOODS WE EAT
What is "dry ice"?
Is it really dry ? What
are the advantages of
dry ice ?
being about 140° F. colder than ice itself, and hence a small
cube of it will do the work of a much larger piece of ice.
In addition, dry ice lasts longer than ordinary ice. A
forty-pound piece uncovered in a store
window during the summer would last
about twenty-four hours. Dry ice
evaporates slowly without leaving any
liquid behind to rust or corrode the
container. At present, it is used hi
the refrigeration of perishable foods
in transit, and particularly for the
transportation of small packages of
ice cream.
The Iceless Refrigerator. In hot
countries, one finds porous skins and
unglazed earthenware vessels filled
with water hanging in a breeze in the
shade. The natives have learned that the water gets
cooler when so treated, though they do not understand
why. When water evaporates, it absorbs heat. If you
wet your hand and swing it in the air, it feels cooler.
This is due to the absorption of heat during evaporation.
Thermos Bottle. The thermos bottle is really a double-
walled bottle, or one bottle inside of another with a
vacuum between them. A vacuum is a better insulator
than air. The inside walls of the bottles surrounding
the vacuum are mirrors which reflect the heat rays and
prevent their passage across the vacuum.
A Clean Kitchen Necessary. Since foods are handled
in the kitchen, it goes without saying that a clean kitchen
will aid greatly in preventing the spoiling of foods. All
surfaces in the kitchen should be washed frequently.
Wooden surfaces, especially when they become greasy,
make excellent dwelling places for bacteria. For this
reason tiled surfaces are more hygienic than wood. Re-
HOW MAY WE KEEP FOODS FROM SPOILING? 345
Galloway
Make a list of all the hygienic and all the labor-saving devices found here.
member that the hands must be kept clean when handling
foods. Since flies carry disease, the kitchen should be
well screened. Dishes should be washed clean with
plenty of soap and rinsed with very hot water.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
low
100°
30
50
clean
spreading
C
screened
vitamin
nutrient
circulation
E
refrigeration
10
vacuum
dry
digest
evaporation
prevent
sterilization
A
pasteurization
start
high
60
145°
212°
D
B
kill
ice
dirty
346 THE FOODS WE EAT
We cook foods because the (1) _ temperature kills the germs
and because the cooking softens tough fibers, thus making food
taste better and (2) _ more easily. Heating substances for a
period long enough to kill germs is called (3) __ Cold will
(4) _ the growth of bacteria, but it does not always (5) _
them. Milk, even when handled under the most sanitary condi-
tions, spoils very easily. One way to help prevent its spoiling
too soon is a process called (6) __ In this process the milk
is heated to (7) _ F., for a period of (8) _ minutes. Heating
the milk to too high a temperature destroys (9) _ (10) _ and
makes the milk less useful. Cold as well as heat is used to prevent
food decay. (11) _ of air is important in (12) _ because it
helps to keep the constant low temperature. Electric (13) _ and
the use of (14) _ (15) _ , are two modern methods of refrigera-
tion. Thermos bottles use a (16) _ to keep the temperature con-
stant. Water may be cooled in iceless refrigerators by the action of
(17) __ Since bacteria cause foods to spoil, the kitchen should be
kept spotlessly (18) __ It should be well (19) _ to prevent the
(20) _ of germs by flies.
STORY TEST
PAUL WAS ABSENT JUST ONE DAY FROM CLASS
Read carefully and critically. List all the errors and suggest corrections.
Of the many things that cause milk to spoil bacteria are the
worst, but they can be checked by cooling and killed by freezing.
One common cause of milk souring is the thunderstorm and there is
no help for it. If you wish to prevent mold from forming on food,
you can do any one of three things. Keep it cool, keep it hot, or
keep it very moist. Since microorganisms are plants, they die if
kept away from the sunlight very long. In canning fruits and
vegetables, it is necessary to heat them to 144° F. in a process
called Pasteurization. They must then be quickly put into cans
and sealed so that they are air-tight. Foods so preserved will
keep indefinitely. The principle of the electric refrigerator is that
the refrigerator has electric insulation in all the walls. An ordinary
refrigerator keeps just the heat out, but the electric refrigerator
keeps both electric and heat energy out.
THE REVIEW SUMMARY
In preparing a summary of what you have learned in this unit,
you will want to place emphasis on the big ideas which have come
HOW MAY WE KEEP FOODS FROM SPOILING? 347
out of the applications of the facts you have learned and the
demonstrations you have seen. For this unit they are as follows :
1. We need a variety of foods.
2. Foods come from plants, animals, and inorganic matter.
3. Foods are used for growth, energy, and regulation of the
bodily activities.
4. Vitamins are essential to life.
5. Milk is the one best food.
6. Bacteria cause foods to spoil.
7. Refrigeration, drying, preserving, and cooking protects foods.
Before making your review summary, test your knowledge of
the facts of the unit by checking over the text so as to be sure
you know the facts underlying the generalizations. Then, using
the generalizations, the material in the text, and everything you
have read, seen, or done yourself, make a summary outline for
your notebook. This outline you may use when you make a
recitation.
TEST ON FUNDAMENTAL CONCEPTS
Make two vertical columns in your workbook. Head one CORRECT and
the other INCORRECT. Under the first place the numbers of all statements
you believe to be correct. Under the other place all the numbers of the
statements you believe to be incorrect. Your grade = right answers X 2.
I. Organic foods are necessary for plants and animals because :
(1) living matter contains the same chemical substances as foods;
(2) they grow and some foods are needed for growth ; (3) living
things do work and some foods are oxidized to release energy;
(4) they need mineral salts ; (5) when a plant wilts it needs organic
food.
II. Green plants: (6) are the food producers of the living
world ; (7) make food only when in the sunlight ; (8) do not use
the foods which they manufacture ; (9) get the energy to do their
work from the sun ; (10) utilize the wastes from animals in making
organic foods.
III. A varied diet is necessary in order: (11) to get a variety
of food; (12) that we will not tire of food; (13) to get vitamins,
minerals, and all the foods which help to build and regulate the
body; (14) to keep enough of the different kinds of food on the
earth ; (15) to give us necessary growth foods.
IV. Proteins must be a part of the daily dietary because they :
(16) make us strong; (17) contain much iron; (18) contain the
necessary materials for body growth ; (19) give us the best supply
of vitamins ; (20) release more energy than other foods.
348 THE FOODS WE EAT
V. Green vegetables should be included in the daily dietary
because they: (21) supply us with many necessary minerals;
(22) are our best sources of fat ; (23) are all rich in proteins ;
(24) supply vitamins ; (25) supply energy at low cost.
VI. We must count our Calories in our food because : (26) it
is the fashion to do so ; (27) each one of us needs a given number
of Calories, depending upon the work we do; (28) overweight
people need fewer Calories than underweight people; (29) age,
weight, and occupation demand a different number of Calories;
(30) young people need more Calories than older people.
VII. Refrigeration: (31) is one means of keeping foods from
spoiling; (32) uses well-insulated containers to regulate temper-
ature ; (33) kills germs because its temperature is so low ; (34) makes
possible the transportation of milk for long distances; (35) is
economical because it keeps foods fresh for such a long time.
VIII. Foods may be kept from spoiling by : (36) drying them
so that bacteria will not grow ; (37) putting them in a cold ice
box ; (38) sterilizing them ; (39) adding salt, sugar, or other
preservatives to them; (40) eating them as soon as they are
cooked.
IX. Milk is the best food for young people because it : (41) con-
tains a good deal of protein ; (42) contains all the body-building
and body-regulating foods; (43) contains vitamins; (44) is our
best source of calcium ; (45) is very cheap.
X. Cooking is useful because it : (46) kills germs ; (47) makes
foods taste good ; (48) softens food so that it may be easily digested ;
(49) makes possible the addition of fat in frying, which aids in
digestion ; (50) makes meats more palatable.
THOUGHT QUESTIONS
1. Suppose you live in a part of the country that has a deficiency
of iodine in its water supply. What should you do about it?
2. Devise an experiment by which you can prove that bacteria
and not molds are responsible for the spoiling of some particular
food. Show all the steps of the experiment, tell what foods you
would use for it, and just how you could prove your point.
3. Determine which would be cheaper for a five-year period,
an ice box which cost originally $70 and which uses 700 pounds
of ice a month at 60^ a hundred, or an automatic iceless refrigerator
that costs $300 and costs $2 a month to operate. Allow 50^
a month for food saved by the iceless refrigerator over that saved
by the ice refrigerator and charge 6% interest on the investment.
4. What processes are dependent upon yeast?
HOW MAY WE KEEP FOODS FROM SPOILING? 349
REPORTS UPON OUTSIDE THINGS I HAVE READ,
DONE, OR SEEN
1. Report upon an article related to some topic discussed in
this unit.
2. Interesting foods of peoples in distant lands.
3. Different ways in which wheat appears upon our dining table.
4. Variations in the temperature of the human body.
5. The value of hunger.
SCIENCE RECREATION
1. Obtain starch from potatoes.
2. Test and preserve eggs for home use.
3. Plan an experiment to show that protein food is the most
favorable kind of food for bacteria.
4. Read Gather's Shadows on the Rock, pages 46 to 47, to see
how the people of Quebec lived in winter during the early days.
SCIENCE CLUB ACTIVITIES
1. Visit a flour mill to see how flour is made.
2. Visit a large dairy to see how milk is protected.
3. Make a list of all the candy you eat for a week, giving the
time of day when you ate it. Can you improve your diet by sub-
stituting other sweet fuel foods? Show changes you would make
and give reasons for so doing.
4. Make a list of all foods you have eaten in the last 24 hours
that contain vitamins. Refer to tables on pages 326 to 327.
How could you improve your dietary?
REFERENCE READING
Conn, H. W., Bacteria, Yeasts and Molds in the Home. Ginn, 1917.
Fisher, I., and Fisk, E. L., How to Live. Funk and Wagnalls, 1932.
Harris, J. W., Lacey, E. V., and Blood, A. F., Everyday Foods.
Houghton Mifflin, 1927.
Hunter, G. W., Laboratory Problems in Civic Biology. American Book
Company, 1916. 100 Calorie Portions, tables, page 204.
Hunter, G. W., New Civic Biology. American Book Company, 1926.
Foods and Dietaries, pages 118-137.
Rose, M. D., Feeding the Family. Macmillan, 1924. Tables, pages
241-433.
Whitman, W. G., Household Physics. Wiley, 1932.
SURVEY QUESTIONS
Do you know in what ways your
body is like an auto ? In what
ways does it differ?
Can you prove that your skin pro-
tects you in any way ?
Do you know how you move ?
Can you tell what happens to a
bowl of bread and milk after you
have eaten it ?
Work is done in all parts of your
body. How is energy released
from the muscles if food gives us
energy?
Can you prove that the human
machine is self-directed ?
Carroll Photo Service
UNIT XH
THE HUMAN MACHINE AND
HOW TO CARE FOR IT
PREVIEW
Each of you has seen a modern locomotive pull a heavy
train up a grade and has wondered at the work it does.
Who has not marveled at the efficient running of an
auto or an airplane engine? But each boy or girl who
reads these lines controls a more wonderful machine than
those just mentioned. Think of it for a moment — a
self -regulated, intelligent machine which does many kinds
of work, which repairs itself when it is injured, and which,
if taken proper care of, will long outlast the locomotive
or auto. And yet we think little about its care and often
abuse it. When a navy battleship or destroyer is to
make a test run, the fuel is selected with the greatest care.
Every one knows that an auto engine requires constant
lubrication and a good quality of gasoline if it is to do its
work effectively. But how many boys and girls think
very much about what is the best fuel food for their own
machine, or what to do to keep the machine in good
running order?
We say that the human body is like an engine or an
automobile, but can we prove this statement ? What is a
machine anyhow ? You have all seen the fireman shovel-
ing coal into the fire box of a locomotive engine or have
watched the man at the gas station fill the fuel tank of
your automobile. But have you ever stopped to think
of what happened to that fuel after it burned ? That fuel
351
352
THE HUMAN MACHINE
Wright Pierce
Where does the energy come from which pulls this heavy train up the grade?
Is the engine getting full efficiency from the fuel ? How do you know ?
contained power or energy which was released as it burned.
Then this energy pushed the piston of the locomotive
engine and turned its wheels. In the auto engine the
gasoline exploded in the cylinders of the engine and drove
pistons which turned a shaft and transmitted the power to
the wheels. In both cases the power or energy locked up
in the fuel was let out in the process of burning or oxida-
tion, and this energy was transformed into work done by
the driving wheels.
The human machine works in much the same way.
Most foods, as we know, are fuels. When taken into the
body, they are actually burned or oxidized and give up
their energy. This energy is then transformed in the
human machine and causes work to be done. That this is
actually so can be proved by some simple demonstrations
THE BODY DIFFERS FROM OTHER MACHINES 353
which we shall see later. The human machine, however,
does more than do work. Unlike the auto or the loco-
motive, with proper
care, it can grow
larger and stronger
or with abuse, it can
waste away, become
weaker, or even die.
liquid oXxsfcas-
eteom pushes
a piston*
lY7e-wh«*l*
Ccxrfoon dioxicte
anct water vapor^
released:
Explain this cartoon in your workbook.
The food it consumes SEE1 2^*- f ^V ****•«****
is not all fuel, for the
human machine grows
and is to some ex-
tent regulated by
foods which, as we
have seen in a previ-
ous unit, are not used
as fuels. In this re-
spect the human machine is very different from the
man-made auto or locomotive.
In order to grow, that is, gain in weight and size, the
body uses the various
chemical elements in the
foods, building them in-
to complex combinations
which make up the living
matter of the body. This
living matter is built up
of millions of tiny units
called cells. You have
all noticed that a brick
building when seen from
a distance does not show
Just as this house is made of bricks, so the the individual bricks,
plants and our bodies are made of cells, the g() ^ the human body
units of structure in living things. Can you . -
see the cells in your body ? WC Cannot SCC these tiny
H. & w- sci. 1 — 24
354 THE HUMAN MACHINE
units or cells unless we use a microscope. Food helps
to build these cells, and in a growing boy or girl the
number of cells is constantly increasing. Food also gives
off energy when it is oxidized or burned in the body.
Each kind of cell, muscle, bone, or nerve has its work
to do. This work means expenditure of energy — the
energy we get from our food which is distributed to the
cells by means of the blood. There in the cells, and
there only, the food is actually oxidized, and gives off
energy in the form of heat, to do our work.
But you ask, how can pieces of solid food get into these
tiny cells ? Food is of no value to the body until it does
get into the cells, and to do this it must be in the form
of a liquid. This is done by a process we call digestion,
during which food changed from a solid to a liquid form.
In this condition it may be absorbed or taken up by the
blood, then circulated to various parts of the body.
Finally, it enters the cells or individual units of the body,
where it is actually used. The pages which follow will
help us understand a little more about the care of this
most wonderful of all machines, the human body.
PROBLEM I. HOW DOES THE HUMAN MACHINE
DIFFER FROM AN AUTOMOBILE?
How an Automobile and the Human Machine Are Alike.
At first sight the human body does not seem much like an
automobile and yet we can see many ways in which they
are alike. Both have a framework which holds them
up — in the auto it is metal, in the body, the bony
skeleton. Both have protective coverings, the glossy
paint finish in the auto, the skin in the body. Both
consume fuel and use it in the same way to release energy
or power to do work. The gears and wheels transmit
the power in the automobile, while in the human machine
HUMAN MACHINE AND THE AUTOMOBILE 355
a complicated system of bony levers1 worked by muscles
gives us our ability to move about. We might even com-
pare the system Of pipes which carries the fuel in the auto
to the system of blood
vessels which carries
food to the parts of
the body where it is
used or the electric
wires of the car to
the nerves which
carry messages to
various parts of the
body. Both engine
and body must get
rid of the waste ma-
terial, for no engine
can run with its fire
box clogged with
ashes, nor can any
human being live
long without getting
rid of wastes. Neither
engine nor body can
be overworked with-
out breaking down.
Rest has been found to be necessary for metals as well as
for man. It is necessary to allow the most smooth-running
machine to take a rest now and then if the machinery is
to be kept in good condition.
How the Auto and the Human Machine Differ. But
let us ask ourselves, how do these two machines differ?
Several differences are easily seen. In the first place the
automobile, once made, can never grow, while we know
the human machine, if properly cared for, can grow larger,
1 Lever. A bar capable of turning around one point.
Wide World
Compare these two kinds of machines. List the
likeness and differences for your workbook.
356 THE HUMAN MACHINE
using the food taken into the body to do this. We also
know the auto cannot repair itself if injured, while our
bodies if cut or bruised will soon heal if we are in good
condition. And perhaps most important of all, while
the auto has to be directed from the outside, the human
machine is self-directed. And each human machine is
an individual, alike in general pattern to every other, yet
different. Anyone of us may accomplish great things
if we have our machine in perfect condition, or we may
be handicapped throughout life by not knowing how to
get the most out of it.
The Building Materials of the Human Machine. We
have already learned that plants and animals are made up
of living units of living stuff called cells. The human
machine is also built of these tiny bits of living matter.
They are so tiny that it would take several thousand to
fill the space made by this letter O.
Demonstration 1. Body Cells.
Scrape the inner surface of the mouth with a clean spoon.
Wash off the scraping, on a glass slide, with a drop of water, add a
drop of blue ink and examine under a compound microscope. The
structures seen are cells which make up the inner lining of the mouth.
Every cell has a body made of living matter, while
within it is found a darker staining structure called the
nucleus. We shall find in our later study of biology that
the nucleus has a very important work in the division of
cells. As the body grows, the cells of which it is composed
are constantly dividing to form more cells, so that our
bodies are formed by the multiplication of cells. These
cells do not grow in size, but in number, and it often hap-
pens that a very large animal or plant is made up of small
cells, while a tiny one may be made up of very large cells.
Demonstration 2. Cells in Hay Infusion.
Place a drop of a hay infusion under the low power and see how
many different kinds of cells you can find.
HUMAN MACHINE AND THE AUTOMOBILE 357
bacteria are microscopic plants
pond scutn
is slippery
string's of
cells
plartt
foimd on the
Kortb side of
trees and rocks
amoeka.
15 OT3<3 of
the simplest
animals
the
slipper-
animal
^Y\ small cmiYmxls
V\ cause waiouria
Some Cells Can Live
Alone. There are
many cells which can
live by themselves. We
have heard of the bac-
teria — they are such
forms of life. Pond
water swarms with
many different kinds
of single-celled animals
and plants, while in
some parts of the ocean
they are so numerous
that they form the food
of other larger animals.
Cells Form Tissues.
But although cells all
have a similar struc-
ture, they differ greatly
in size, shape, and use
in the human body.
We have blood cells,
muscle cells, bone cells, nerve cells, and many other va-
rieties. These cells, when they are all alike and all doing
a certain kind of
work, are called
tissues.
Tissues Form
Organs. We
also find in the
body that
groups of tissues
may have some
work to do to-
ceiis from tissues. gether. Take,
Some cells that live alone. The plant at the
left is a string of cells and is magnified much
less than the rest of the plate. All of the
plants and animals shown live in the water.
cell
chlbroplosb
nucleus
cytoplasm
!im
one celled, animals . amoeba
THE HUMAN MACHINE
r\
Tissues build organs.
for example, the hand. It is made up of skin, bones,
muscles, nerves, and other tissues. But these tissues
all work together.
We call such groups
of tissues an organ
and the different
plants and animals
are called organisms
because they are
made up of numer-
ous organs.
The Human Machine an Organism. In man, the most
complicated of all machines, we find many systems of
organs. We find the protective covering or skin, beneath
it a layer of fat, then muscles giving form to the body and
by attachment to the bones allowing movement. We
also find a tube running through the body, made up of
many kinds of cells, and varying greatly in structure.
Since it has a general work to do, we speak of it as the
digestive tract, for its job is to make food usable in the
body by digestion. Other systems of organs are found.
We know the use of the lungs in breathing and of the heart
in pumping the blood over the body. Most wonderful of
all is the directive apparatus called the nervous system.
By this complicated group of organs, those of sight, hear-
ing, smelling, tasting, and touching, we are able to know
about things which surround us. And by means of the
nerves, which connect these organs of sensation with the
directive apparatus called the brain, our human machine
is able to run intelligently.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
HOW IS THE HUMAN MACHINE PROTECTED? 359
skeleton nonliving heavy steam
protective tissues organs food
oxygen nitrogen carbon hydrogen
self protection build energy
blood cells tear down oxidize
repair wastes living dead
The auto and the human body are alike because they both
release (1) when they (2) fuels. They both have (3)
coverings, both have a framework or (4) , both use (5)
to release energy, both have to get rid of their (6) But
they differ greatly because the human machine can (7) and
(8) its structure out of (9) , and it is (10) directed.
It is made of (11) material the units of which are called
(12) , while the auto is made from many (13) materials.
STORY TEST
SALLIE TELLS ABOUT CELLS
Read carefully and critically. List all the errors and suggest corrections.
My teacher has asked me to tell the class what cells are and
what they do. Your body and mine are made of cells. They
are tiny units of living stuff so small that single cells cannot be
seen except with a microscope. Like bricks, they are all exactly
alike in size and shape, the only difference being that big animals
and plants have big cells while small ones have little cells. As a
body grows larger, the cells grow in size, so this is another reason
why larger things have larger cells. Every cell has a nucleus and
grows by dividing, so that one cell may form two, these two, four,
and so on. This is all I know about cells.
PROBLEM II. HOW IS THE HUMAN MACHINE
PROTECTED ?
The Skin, Its Uses and Its Care. We all know that
the skin is a protective covering and that if we cut or
break it, we feel a sensation of pain. The figure on page
361 shows us that the skin is made up of cells, the outer
layer of which is largely dead, while the inner layer is very
much alive. It is this part that bleeds when we scratch
or cut ourselves, for it is really supplied with tiny blood
vessels. If you look at the surface of the skin on your
360
THE HUMAN MACHINE
Finger prints of the same area in three
different persons.
hand, you will notice that it is thrown into many tiny
ridges. These have no particular pattern and they are so
individual in different
persons that finger prints
made by pressing these
ridges on an ink pad and
then on paper are used
for purposes of identifica-
tion, for each person's
finger prints are different
from each other person's.
If you could examine a bit of your skin with a micro-
scope, you might find many tiny holes which open on its
surface. These are the openings of the sweat glands,
tiny groups of cells which take water and wastes from
the blood. We perspire when we are warm, and, as
a matter of fact, the
water which passes
out not only carries
wastes from the blood,
but also gets rid of
some heat. Since these
tiny pores are very
important in the regu-
lation of our body
cfglcmct
temperature, we must
not allow them to be-
come clogged with dirt •
or grease. The fre-
quent use of soap and
water is necessary, es-
pecially after working
in a dusty or grimy
r>lflpp if WP «rp tn kppr» A sweat gland showinS its position in the skin.
,6, It We )Keep Can you find the outer dead layer? Wastes are
the pores Open. passed out through the mouth of the gland.
HOW IS THE HUMAN MACHINE PROTECTED? 361
.sktftofboir
epicfermw
gland-. ill
Hairs and How They Grow. Have you ever looked at
the back of your hand when it was held in a strong light ?
If so, you noticed many hairs growing there. Although
these hairs are thicker or longer in some parts of the body,
we can find them growing almost everywhere from the
skin. They grow as the
accompanying diagram
shows, from little pits in
the dermis, or inner skin.
At the base of each hair
are found tiny collections
of cells which form oil
called oil glands. These
lubricate the hairs. Since
the openings of these
glands may become
clogged with dirt, sur-
faces covered with hair
should be washed fre-
quently.
Care of the Hair. The
simplest method of car-
ing for the hair is brush-
ing. Whether the hair is
long or short, both boys
and girls should brush
their hair thoroughly
every day. This keeps
the scalp stimulated and
free from dirt or dandruff. It also distributes the natural
oil from the scalp over the length of the hair and makes
it look glossy and healthy. Wetting the hair with water
every day to keep it in place is a bad habit, which has
often been blamed for early baldness. Unruly hair may
be trained into place by the use of a light oily dressing.
bbod
vessel
nerve -
A section cut through a hair. In which
layer of the skin do hairs grow ?
362 THE HUMAN MACHINE
Sticky or waxy fixatives should be avoided because they
may harden into a thin coating all over the scalp, which
stunts the growth of the hair.
Hair should be shampooed as often as it needs it. The
average time is once every two weeks. Pure Castile soap
is the best for shampooing. All strongly alkaline sub-
stances, like laundry soap or washing powders, should be
avoided. Where the water is hard, it can be softened
with a little borax or soda, dissolved in the water before
soap is used. The scum that often forms on the hair
when it is washed in hard water can be removed by care-
ful rinsing with a little lemon juice or vinegar (also to be
added to the water, never poured directly on the hair).
Both water softeners and acid rinses must be used spar-
ingly, because they make the hair reddish, harsh, dry,
and brittle. Hair that is burned or dried from the sun,
salt-water bathing, or any other cause can be improved
by treatments with a mixture of olive and castor oils.
Care of the Nails. The nails on the fingers and toes,
like the hair, and like the feathers, scales, horns, and
hoofs on lower animals, are outgrowths from the inner
skin. Normally they grow continuously, and if one falls
out or is injured, another comes to take its place. Young
people should learn to care for their nails as carefully as
they wash their hands. The skin at the base should be
pushed back regularly, and the nails should be kept clean
under their free edge by means of a blunt, soft stick.
Metal instruments may injure or disfigure the nails.
They should be well shaped with a thin file, and, above
all, should never be bitten off, because biting causes
changes in form and growth which can never be corrected
throughout life. Many a man and woman have regretted
in later years the bad habit of biting the nails in childhood.
Care of the Skin. No other part of the human machine
needs care more than the skin. In the first place it should
HOW IS THE HUMAN MACHINE PROTECTED? 363
J
-vhite individual .
soap manicure complexion face
brash. cloth
_1_ fresh air
— sunshirce
_ -vhoksoroe {bods
exercise
Set
What are the best ways of taking care of the skin ?
be kept clean, especially the face and hands, for they are
exposed to dirt, smoke, and other irritating substances.
Nothing is better for cleaning than plain soap and water.
Scented soaps, powders, or lotions do not improve the skin
and often do harm by clogging up the pores or placing
substances that are injurious in the skin. The tubes
from the sweat and oil glands are readily filled with dirt
or other substances, and if certain bacteria lodge in these
ducts, they are apt to cause pimples or boils. In severe
or chronic cases of this kind, the boy or girl should go to
a physician for advice and treatment. Careless or incor-
rect treatment often causes marks in the skin, which may
remain as permanent disfigurements.
If the skin becomes sunburned, it should be protected
from further injury by the application of soothing oint-
ments and lotions. Frequent exposure gradually makes
the skin tough, and freckles or tan may develop. The
best thing to do for these discolorations is to let them
wear away, because skin bleaches have little or no bene-
ficial effect.
The Use of Cosmetics. Young skin has normally
invisible pores and a healthy glow from the lively circu-
lation in a well-exercised body. "The key-note of beauty
is naturalness," so the natural color in her cheeks and
lips should make artificial aids to beauty unnecessary for
the young high school girl. But she must keep her skin
364 THE HUMAN MACHINE
perfectly clean. Oily skin needs only mild soap and
water, but dry skin can be improved by the use of a good
cleansing cream (preferably one containing a little lanolin
or other animal fat) after washing.
There is no such thing as a "skin food" beyond what
is taken into the mouth as food for the whole body.
Remember a healthy skin is a natural skin.
The Skin Regulates Our Body Temperature. We are all
aware of the fact that sometimes we feel hot or feel cold,
but if we were to take the body temperature at either of
these times, we would find it varied little from its normal
heat of 98.6°. To be sure, the outer part of the skin
would be colder on a cold day and warmer on a warm
day, but the skin itself has a very complex mechanism
for regulating our body temperature. By means of the
sweat glands shown in the diagram on page 360 as little
coiled tubes, and the very delicate nervous apparatus
which controls the amount of sweat released, the skin is
enabled to regulate the heat of the body. When we do
more work and the body becomes warmer from the in-
creased oxidation within it, the skin automatically is
enabled to throw off this heat and it is able also to retain
more heat on a cold day.
How the Body Loses Heat. Heat is lost from the body
by the three methods we have studied in the preceding
chapters. A certain amount of heat is lost by conduction,
although the air is a very poor conductor, and warm
fabrics get much of their heat-holding qualities because
of the stagnant air confined in their meshes. Most of our
heat from the body is lost by convection. When we fan
ourselves, we create a current of air, causing cooler air
to replace the warm air about the body. We also lose
heat by radiation to other solid objects which are cold.
It is very easy to take cold by sitting on the damp ground,
or close to cold windows or walls, because in this way
HOW IS THE HUMAN MACHINE PROTECTED? 365
Study this diagram carefully. What
important story does it tell about the
loss of heat from your body ?
warmth is removed rapidly from one part of the body.
Curiously enough, although we feel warm when we per-
spire, much of the heat of
the body is taken away by
evaporation of the water
from the body surface. On
a hot muggy day, when the
atmosphere is moist, little
heat is lost by evaporation
and we feel much hotter
than on an equally hot, dry
day when we perspire freely.
On a humid day a blanket
of stagnant heated air forms
about the body, which
makes one feel very uncom-
fortable. For this reason electric fans have saved people
from much discomfort by keeping the air in motion, thus
evaporating the moisture and removing heat from the
body.
Underclothes and Their Uses. In winter we need under-
clothes which are nonconductors of heat, and retain the
warmth of the body. In summer we need underclothes
that do not hold moisture, for wet, clammy underclothes
cool us by conduction if it is cold, or if it is warm, make
us uncomfortably hot by preventing evaporation, and
sometimes even cause a
cold to develop. It does
not seem to make very
much difference what
kind of materials are
used, whether woolen,
cotton, linen, or silk
Which weave of underclothes will be better fibeF' SO long RS the Un'
for summer? why? derclothes are porous.
^tebisi
w»i|Ms
366
THE HUMAN MACHINE
Woolen underclothes are best for wear in winter, because
the natural curly fiber makes them porous, and also be-
cause they absorb more water, and this protects the skin
from cooling too rapidly in case we get overheated. Most
colds are taken because people insist on wearing too
much in winter. They wear heavy underclothes and
heavy outer clothes, then go from a warm room to the
cold outdoors, and back again to warm workrooms where
the temperature is often higher than that of summer
heat. The better rule is to wear a medium-weight under-
wear in winter and heavier outside clothes, which can be
changed as one goes into different temperatures.
Bathing and the Skin. Since the skin is such an im-
portant organ for heat regulation and for getting rid of
wastes as well, it goes without saying that we should take
good care of it. Bathing keeps the pores open and the
skin clean. In summer, when perspiration is increased,
baths should be more frequent than in winter. A cold
shower or plunge every day, both in winter and in summer,
is an excellent habit to accustom the skin to different
changes. If you find that after a rubdown the skin does
not glow and you feel cold and chilly, do not take the
baths so cold. It is always well to begin with tepid water
and gradually turn on colder as the bath progresses.
Which bath should be taken in the morning and which in the evening ? Give
your reasons.
HOW IS THE HUMAN MACHINE PROTECTED? 367
Hot baths should only be taken at night, as they tend to
bring blood to the skin and increase the radiation from
the body, thus making the chances of taking cold greater.
But hot baths take the blood away from the brain, thus
helping anyone who is wide awake to get to sleep more
easily. The best bath is the shower, for this stimulates
the outside skin, helping to make it resistant against colds.
When we chill the body, the body resistance is lowered
and germs, which are almost always present in our
mouths and throats, develop rapidly and cause a cold.
Habits of Cleanliness. " Cleanliness is next to god-
liness " is an old saying, and a good one. Habits of clean-
liness at meals are particularly necessary. One should
always wash the hands after going to the toilet. Bathing
the entire body at least once a week should be a habit, and
if the feet or body become covered with perspiration in
warm weather, one should bathe every day.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
raise dead oil ridges
hairs sight protected temperature
depressions different pores identification
touch nerves hearing blood vessels
alike prints bones cells
sweat alive regulate arteries
The human machine is (1) by the skin. It has two layers,
the inner of which is (2) It is supplied with (3) and
(4) It gives us sensations of (5) , (6) , and pressure.
Nails and (7) grow from the inner skin. The skin has millions
of (8) , which are openings of (9) glands. The skin in
giving off perspiration helps to (10) our body temperature.
Due to the fact that the skin is thrown into (11) and (12)
and that the skin of every person is slightly (13) from that of
every other person, (14) are made of the finger tips and are
used for purposes of (15)
368
THE HUMAN MACHINE
STORY TEST
AGNES TELLS How TO TAKE CARE OF THE SKIN
Read carefully and critically. List all the errors and suggest corrections.
Every girl likes to have a good complexion. Most people think
that unscented soap and water are best, but I like to use scented
soap and face powder. The powder keeps dirt out of the pores
and gives color to the skin. A touch of rouge is also attractive
and makes the skin healthy, because it also keeps dirt out of the
pores. The hair can be kept in good condition by frequent brush-
ing as this spreads the oil from the glands at base of the hair over
the surface of the hair. It is not good to allow cold water to touch
the skin as this is apt to chill it and then we take cold.
PROBLEM III. HOW DOES THE BODY MOVE?
The Skeleton and Muscles. Have you ever thought of
what the skeleton does for your body? You may have
seen a jellyfish or some other animal that has no skeleton
either inside or outside of its body. A jellyfish thrown
up on the beach has no definite form. It is only when
the water supports it that it has its beautiful shape.
Without a skeleton our bodies would sink into a shapeless
mass, for we are over 65 per cent water. The skeleton
gives attachment to the muscles, thus aiding in movement.
Study the diagram on page 369 carefully. You will notice
that instead of
being all in one
piece, the skele-
ton is made of
many bones and
that those used
for movement
are jointed.
The skeleton
protects the
delicate parts of
.cottar- bone
op forearm
Why can the arm lift a weight ? Read through the entire
problem before you attempt an answer.
HOW DOES THE BODY MOVE?
369
the body. Look at the bony skull which protects the
brain, and notice how well it is fitted to do this. Observe
in the accompanying diagram how the curved
ribs are attached in back to the backbone
and in front to the breastbone, thus forming
a protection for the delicate lungs and other
organs held in the cavity they surround.
What Are Bones Made of? If you burn
one leg bone of a chicken in a hot fire, it can
be reduced to a little heap of white ashes,
largely lime. If the other leg bone is
placed for a few days in a 10 per cent solu-
tion of hydrochloric acid, the mineral
matter will be dissolved out so that the
bone can be tied into a knot. Thus we
see bone is made of animal matter as well
as mineral. The bones of young people
are growing and contain relatively more
animal matter than do the bones of older
people. A broken bone, therefore, is much
more serious in an older person. Do you
see why? Live bones are surrounded with
a delicate covering of living matter, through
which they absorb nourishment. Damage
to this part of the bone is serious because
it cuts off the food supply from the bone.
Bones and Muscles. How we admire an athlete ! And
how most of us enjoy playing games or swimming or
hiking. Have you ever thought why the machine we call
the body can do these things so well ? Let us look at the
diagram on page 368. The skeleton in a general way
seems to have two purposes : one, protection ; the other,
to aid in movement. Move your own arm and you will
see that the long bones are jointed. Now compare with
the diagram and you will find the structures we call
H. & w. sci. i — 25
Does the skele-
ton give shape to
the body? What
other functions
has it ?
370
THE HUMAN MACHINE
1
muscles attached to the bones in such a way that when
they lengthen or shorten, they raise or lower the bones,
; thus causing movement. Thus long
bones act as levers, and allow us to
move.
Muscles are always found in pairs, so
when one gets longer, the other contracts,
thus causing movement. Find two such
muscles in your own arm. Muscles are
attached to the bones by strong cordlike
tendons which are not so elastic as the
muscles, but which serve to fasten the
muscles firmly to the bones. .Look at
the leg bones of a dog or cat skeleton
and you will find roughened places in the
surface. These are where the tendons are
attached. Now you can see what hap-
pens when you
"pull a tendon"
and why it is that
you have to be inac-
tive for so long after
such an accident.
Ligaments and Bones. If you
have ever tried to carve a duck,
you may remember what a hard
time you had disjointing the leg
bones. As you cut into the joints,
you found there white, glistening
cords which held the bones to-
gether. These are the ligaments,
T /. , , u . . , i Notice how the tendons are
and are found between all jointed attached to the muscles and
bones. When we tear Or injure a are held near to the wrist
ligament, we have a "sprain." 5^* £JSlL2
Sprains are often more serious above.
In what part of the
skeleton do you
think this fracture
took place? Give
your reasons after
studying the cut on
page 369.
muscle/
cement-
•tendon
.tewdon.
HOW DOES THE BODY MOVE?
371
than broken bones, for they heal slowly. Sprained joints
should be bandaged carefully, have frequent hot applica-
tions, and should be rested until well.
Cartilage and Bones. If you have ever measured your
height after getting out of bed in the morning, and again
just before going to bed at night, you would be astonished
to find that you had grown shorter during the day. But
why ? Your backbone is made up of a number of separate
bones put together in the form of a double curve. Be-
tween each of these bones is a pad of elastic substance
called cartilage. This protects us against jars when we
walk or jump. You can thus see why the body is shorter
at night. Cartilage
is found between
all movable bones
and serves to make
them more elastic,
thus protecting
them against break-
The Value of
Good Posture. We
all admire a boy or
girl who stands
erect and carries the
body well. They
look alert, strong,
and graceful. It is
said that more
young people are
turned down from
jobs because of the
bad impression
given from poor
posture than for
Wright Pierce
Examples of poor and fair posture in college boys.
372
THE HUMAN MACHINE
any other reason. In good standing posture the body is
held erect, the chest is thrust forward, and the head and
shoulders are balanced above the body's center of gravity.
A glance at the cuts on pages 369 and 371 shows that the
skeleton, if held erect, balances the body so that no strain
is put on any one set of muscles. Since good posture is
largely a matter of habit, we should learn to achieve it
while still young. In good posture the lungs, heart, and
digestive organs are in proper position, thus aiding good
breathing, circulation, and digestion. And most of all, we
have a feeling of health which enables us to look at our
tasks or difficulties and laugh them off because we feel well.
How to Get and Keep Good Posture. We first must
have the feeling that comes with a knowledge of correct
posture and then we must continually practice standing
and walking correctly. If we fail to hold our head erect,
or if we allow our shoulders to become round or let our
chest slump in and our abdomen stick out, we are failing
to practice good posture. Slumping over our desks when
studying is one way to get
poor posture and allowing
the muscles of the abdomen
to relax is another bad fault.
Ask your physical education
teacher to suggest exercises
which will help you to build
up a good erect carriage and
then practice these regularly,
for it is only by constant
effort that we are able to
keep good posture.
Flat Feet. Fallen arches
are Often a cause of poor
Notice how the muscles tend to keep nnc;tllrp FYatninp thp flifl-
the bones of the foot arched. What Posture-
might cause the arches to fall? gram Carefully. IOU Will
HOW DOES THE BODY MOVE? 373
notice that the bones of the foot form a perfect arch,
which is supported by the pull of certain muscles and
tendons of the foot. You can easily test your own arches
by placing the feet in water and then walking on a dry, flat
Which of the two people have fallen arches ?
surface. Fallen arches will make almost as wide a mark
under the middle of the foot as at the toes or heel/while
a good arch will only make a narrow mark under the
middle of the foot. Fallen arches may give pain in
the foot, the leg, or even the back. This is because of the
strain put on muscles in order to keep erect. One of the
best ways to keep the arches in good condition is to walk
with the feet straight instead of " toeing out." If your
arches are not perfect, ask your physical education teacher
for exercises that will correct your trouble. Perhaps
your shoes may not be correct. High heels often cause
broken arches, as do shoes which are too narrow. Better
be sensible than sorry !
Shoes for Comfort. For ordinary wear, heavy-soled
shoes may keep the feet fairly dry, but in case of rain,
it is better to wear rubbers, although most people con-
sider them a nuisance. Our feet surely should receive
our best care, for they bear our body weight the greater
part of the working day. They are often harmed in
youth by improper shoes, especially in the case of girls,
374
THE HUMAN MACHINE
who pride themselves on the shapely appearance of the
feet and ankles. The high heels worn by many do much
to strain the muscles
of the feet, and are
responsible for many
aches and pains in
later life, which come
as a result of flat
feet, broken arches,
and other ailments.
Corns, callous spots,
and blisters are
caused by wearing
shoes of a wrong size
or shape for the feet.
Shoes should be long and broad enough to give plenty of
room for the toes. They should have a straight last, and
the heels should not be too high. A common-sense shoe,
sold by most dealers nowadays, is better than the longer,
pointed, high-heeled shoe which is fashionable and worn
by girls who do not realize the harm caused by wearing
a shoe which does not fit the shape of the foot.
This X-ray photograph shows how high heels
throw the foot out of shape.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
living
shape
cord
cartilage
support
dead
attach
protect
trunk
triplets
mass
string
ligaments
balanced
bony
contracts
pads
soft
organic
gravity
expands
levers
unelastic
muscles
unbalanced
mineral
pairs
brain
The (1) skeleton helps (2) the body, gives it (3).
and enables (4) to move the body because they are attached
THE USE OF FOOD 375
to the bones which act as (5) Bones also (6) delicate
organs such as the (7) and spinal (8) Bones are made
of (9) as well as (10) matter. Muscles which cause
movement are found in (11) : one (12) when its opposite
relaxes. Tendons (13) muscles to bones; (14) bind
bones together. Between bones which move against each other
are found (15) of elastic (16) which save the body from
unnecessary jars. Good standing posture is brought about by
having the head and shoulders (17) over the center of (18)
of the body.
STORY TEST
JACK WRITES ABOUT POSTURE
Read carefully and critically. List all the errors and suggest corrections.
Anyone who hopes to succeed in life needs good posture. Not
only do employers like to see it in people who come to them for
jobs, but it helps one keep well. Good posture can never become
a matter of habit, you always have to practice it consciously.
Postural exercises do not do us much good because if you practice
them you get tired and that is bad. Fallen arches are a symptom
of bad posture. You can test your arches by walking with wet
bare feet on a flat surface. A wide mark made on the paper
between toe and heel shows that the arch is perfect. Girls often
wear shoes with high heels, which tip the body forward. This is
often a cause of poor posture.
PROBLEM IV. HOW DOES THE HUMAN MACHINE
MAKE USE OF FOOD?
The Problem of Getting Food Where It Can Be Used.
If we recall our auto, we remember that fuel is burned in
the cylinders. The explosion of gas pushes the piston,
which causes the shaft to revolve. This transmits power
to the wheels and the car moves. Very different condi-
tions exist, however, in the human machine. Food is not
oxidized where it is taken into the body, but in the individ-
ual cells which do the work. If this is true, then while you
are reading these words, work is done and food is oxidized
in your hands, which hold the book, in the muscle cells
which move your eyes, in the cells in the eye which register
376
THE HUMAN MACHINE
the words you read, and in the cells of the brain which
you use in thinking about what you read. Hundreds,
perhaps thousands, of cells are involved in the simplest
processes of daily life. So you see it is far from simple
How does food get to the cells ? What happens to food in the cells ?
to explain just how the human machine makes use of the
food it takes in. Not only must the food be put into a
condition so that it can get out of the digestive tract into
the cells, but it must also be carried to these cells. In
addition, if the food is to be oxidized, oxygen is used.
This must get in from the air and be passed to the cells.
Three systems of organs accomplish this work. First,
the digestive tract prepares the food, or digests it, so that
• oxyg&n.
a capillary
Cccrries "
useful
materials
to needy cells
it contracts
and as
it Vorks
it to *ork
wastes
a capillary
carries '
Wastes from
Cells at
Vork-
How does a muscle work ?
THE USE OF FOOD 377
it may be absorbed into the blood. Then the heart must
pump the blood and the blood vessels carry the food to the
cells. In the cells, as the food is used, waste products
are formed which must be removed and the blood must
carry these away. A third system of organs brings the
oxygen from outside the body so that it may get into
the blood and then be carried to the cells. These are the
organs of respiration, or the breathing organs.
These processes are all different, but each is tied up
with the other. Food must be digested, then transported
to the cells. Then oxygen must be used to burn the food
before energy can be released and work done. In addi-
tion, some of the food may be used to build up the cells,
and finally materials not usable must be removed — a
complicated process, but if we take one thing at a time,
we may be able to understand what happens.
Demonstration 3. What Do We Mean by Digestion?
Place a piece of soda cracker -in water in a test tube. Add a
few drops of iodine. What happens? If the mixture turns blue-
black, it shows the presence of starch.
Take another piece of the same cracker treated in the same
way, but place in the test tube an equal amount of a blue sub-
stance called Fehling's solution. Heat to almost boiling. If the
mixture in the test tube turns brick red, this shows the presence
of grape sugar. What happens?
Now chew a piece of soda cracker until it tastes sweet. Con-
tinue to chew it until it is thoroughly mixed with saliva. Then
place the chewed cracker with plenty of saliva in a test tube. Set
the tube in warm water for 20 minutes. Then test the contents
with Fehling's solution, treating as before. What happens?
This is an example of a controlled experiment by which
we have proved that something in the saliva must have
caused the cracker to change from starch to grape sugar.
Starch will not dissolve in water, but sugar will. If food
is to get into the cells, it must be in solution. These
experiments show the necessity for digestion,
378
THE HUMAN MACHINE
**«t— iV-?sr
What Causes Digestion ? We find in plants and animals
that the process of changing foods from a solid to a liquid
condition goes on rather constantly, for in no other
way can food get
into the cells. The
process is brought
about by substances
which are called en-
gallbladder zymes. These are
the active substances
in our digestive
juices. In the mouth
starches are digested
by enzymes, while
in the stomach pro-
teins are changed to
fluids by other kinds
of enzymes. In the
small intestine we
have other enzymes
that act on all three
food substances :
starches, fats, and
proteins. We will
stomach
small
intestine.
intestine,
append!
rect/um
, , ,
learn mO1
The food tube of man with the liver and pancreas,
What have these structures to do with the food
tube ? What is another name for everything these WOnderf ul SUb-
showninthiscut? stances later.
Where Does Digestion Take Place ? If you will look at
the accompanying diagram, you will see the parts of the
digestive tract of man. We have already seen that di-
gestion takes place in various parts of the tract. The
food, after being chewed and mixed with saliva, is squeezed
down the tract by means of contractions of the muscles
of the food tube. This movement occurs in both the
large and small intestines and is of great importance in
THE USE OP FOOD
causing food to pass on its way. The food tube also helps
to break up the food through the churning of its muscles.
The end results are that the food which passes into the
mouth in solid form is gradually broken up and then made
soluble by means of enzymes formed in the glands in
different parts of the food tube. The wall of the tube
is filled with tiny blood vessels, and in the small intestine
there are numerous tiny projections into which these
tiny blood vessels pass. As the food
becomes soluble, it is absorbed
through these projections and gets
into the blood and thus ultimately
gets to the cells.
Demonstration 4. How Food Is Prepared ' _panctSttic|..~
for Digestion. juice,
Cut a half-inch cube from a hard-boiled
egg and place it in a test tube with a
small amount of artificial pancreatic juice.
Take a second cube of the same size and
mince it. Place this in a second test tube
with an equal amount of artificial pancreatic juice. Place the
two test tubes in warm water and leave for half an hour. What
has happened in each of the tubes ? How do you explain this ?
If enzymes are to do their work properly, then food
must come in contact with them. If the food is chewed
into small particles, a greater amount of surface will be
exposed to the enzyme and digestion will then take place
more rapidly. This shows the reason for chewing food.
Our teeth are well fitted for this
purpose ; some are sharp and are
used for cutting and others have
broad surfaces used for grinding.
Care of the Teeth. Thorough
chewing of the food is necessary
for good health. Many of us bolt
What is the object of chewing &
food? our food, and as a result suffer
WILLIAM HARVEY, 1578-1657.
TTARVEY as a boy must have led a pleasant life near London
-as a son in a well-to-do English family. At the age of fourteen
he entered Cambridge University, and five years later went to Italy,
where he studied at the University of Padua, under the famous
anatomist, Fabricius. From him he learned of the presence of valves
in the veins, a fact he made use of later. On his return to England
he practiced medicine and taught in the medical school, and soon
became one of the most noted physicians in England. He was the
court physician under both James I and Charles I. But his name
is remembered today for his discovery of the circulation of the
blood. Up to this time physicians thought the blood moved in
the body but did not know that the heart pumped it through the
arteries. Harvey showed, in a book published in 1628, that there
was a complete circulation from one side of the heart through the
arteries and back through the veins to the other side of the heart.
He never proved the existence of the capillaries, although he rea-
soned that they must be present.
We know very little of Harvey as a practitioner. In fact he was,
according to some records, not at all popular. We do know he was
an active physician and performed important surgical operations.
THE USE OF FOOD 381
from indigestion. The teeth are important factors in
the habit of proper chewing. We can form no better
habit than that of properly brushing them. The teeth
should be brushed at least twice a day, and not only
the teeth, but also the gums around them. Brushing
up and down rather than across the teeth is of much
more value because it dislodges the food particles held
between the teeth and thus prevents their decay. The
teeth should be examined by a dentist at least twice a
year, for this will save much pain and possible loss later
on. Decay of the teeth comes as a result of bacteria
lodging in the same crevices with food. They pour out
an acid waste substance which attacks the hard enamel
of the teeth, breaking it down and thus allowing germs
gradually to attack the living portion of the teeth under-
neath. Upon our teeth depends much of our health
later on in life, so let us form habits of proper care of
them while we are boys and girls.
How Digested Food Gets to the Body Cells. We have
already seen that the body is well supplied with blood
vessels. If we could take away all flesh and bones from a
body and fill the blood vessels with something that would
hold them in place, they would form a perfect mold of the
body, with tiny vessels reaching to all its parts. The
fluid part of the blood is the vehicle which carries digested
food to all parts of the body. Another solid part of the
blood, called the red corpuscles, carries oxygen to the cells
so that work can be done there. These red corpuscles
are little flattened disks so numerous and small that it is
estimated there are about 500,000,000 in a drop of healthy
blood. We also find in the blood colorless corpuscles,
the body police, which protect the body against harmful
bacteria by eating them up. Other bodies called the blood
platelets help the blood to clot when a blood vessel is cut,
thus keeping us from bleeding to death.
THE HUMAN MACHINE
What Causes the Blood to Circulate ? But the blood
does not just flow around in the vessels. It is under pres-
sure from a double force pump we call the heart. This
to head, anct
to righb arm and: band
•pulmonary
circulation
to right lung
systemic
Circulation.
to left arm andhanct
pulmonary
circulation
renal Circulation
to right
systemic circulation
to lejb
right auri
right ventricle
left auricle
left ventricle
Tenal Circulation
to left "kidney
systemic circulation
The blood circulates throughout the body by means of a continuous closed
system of tubes, called the circulatory system.
organ, though not bigger than the fist of a good-sized man,
pumps about a gallon of blood a minute, day in and day
out, during our lives. When we exercise, the heart pumps
faster, and during a game of handball or tennis it may
pump five or six gallons a minute to the working cells.
Blood vessels which leave the heart are elastic with
rather thick walls in order to withstand the pressure.
These are called arteries. They are the vessels which
pulsate as the heart beats and from them we get our pulse.
Arteries branch out, getting smaller and smaller until
THE USE OF FOOD
383
valve
'.valve
.muscle
they form a network of tiny blood vessels which run close
around the cells in the tissues all over the body. These
small blood vessels are
called capillaries and
from the blood in them
the cells get food and
oxygen, and take up
wastes. The capillaries
in turn lead into tiny
veins, thin-walled vessels
which get larger and
larger as they return
blood to the heart.
There are two complete
circulations of blood in
the body, one from the
right side of the heart
to the lungs, returning
to the left side of the
heart, from which it
passes, as has just been
described, to all parts
of the body. The blood returns to the right side of the
heart, thus completing the circulation.
each Vialf of the
hectrt, is a pump
The heart is a double force pump. Can
you prove it from the diagram? The thick
muscular part of the heart is called ventricle,
the thin-walled upper portion auricle. De-
scribe the heart's action, using the above
terms.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
digested
waste
liver
enzymes
kidneys
used
lungs
carbon dioxide
same
energy
wasted
soluble
stomach
oxidized
absorbed
vitamins
different
blood
cells
unites
bones
fuel
oxygen
separates
384 THE HUMAN MACHINE
Although the human body is like an engine, it differs from it
in the way it uses its (1) All work is done in the (2) of
the body. Food is (3) to release energy. Food must be
made (4) or digested so that it can get into the cells. Digestion
takes place in the food tube and is brought about by the action of
substances called (5) Starches, fats, and proteins are each
(6) by different (7) After the foods are digested, they are
(8) into the blood, taken to the cells, and then (9) there.
Oxygen from the air is taken into the (10) and from there
carried by the (11) to the cells, where it (12) with the
food substances and releases (13) The (14) products
are carried away by the blood.
STORY TEST
PHILIP TELLS ABOUT AN EXPERIMENT
Read carefully and critically. List all the errors and suggest corrections.
We saw an experiment the other day that showed why we should
chew food. The teacher took two pieces of hard-boiled egg exactly
the same size. Then he chopped one piece up fine and left the
other as it was and then put the two lots of egg into two test tubes.
Each tube was about half full of some stuff he called artificial
digestive juice. I think this juice contained an acid, for, after he
left the tubes for half an hour in warm water, we looked again
and found that the big piece of egg was not changed but the little
pieces were all gone and the substance in one tube looked milky.
I guessed that the acid dissolved the small pieces of egg. I don't
see why it didn't break down the big piece of egg, unless it was
because it wasn't strong enough.
PROBLEM V. HOW DO WE CONTROL
THE HUMAN MACHINE?
How the Nervous System Works. You have all seen
a race of sprinters. At the start all is attention. The
runners get set. Every muscle is tense awaiting the
starter's gun. Then off they go. What has happened?
The boys in the race have been alert to listen for the sound
of the starter's gun. Then the messages travel from the
ear to the brain, and from there messages go to the muscles
HOW DO WE CONTROL THE HUMAN MACHINE? 385
Wright Pierce
In a sprint the race usually depends upon the start. How did these boys get
off " on the gun " ?
of the legs and arms. Toes dig into the ground ; muscles
are tensed, and the boys are off. The nervous system
has been the director and is responsible for their success
or failure in the race.
The Central Nervous System. We know in a general
way what the nervous system is. There are really two
parts to the nervous system : a central portion consisting
of the brain and spinal cord, which are protected by the
bones of the skull and spinal column, and a number of
paired nerves which leave the central nervous system
and seem to run to all parts of the body. The nervous
system is made up of cells like the rest of the body,
but these cells are of various shapes and sizes and many
of them have very long threadlike tails. These are the
structures that make up the nerves. The nerves are
made up of two kinds of cells. In one kind the cells
pick up the sensation on the outside of the body by
H. & w. sci. i—26
THE HUMAN MACHINE
sound or touch or smell and carry it to the inner nervous
system. Here the sensory cells turn it over to another
lot of nerve cells and they in turn translate the message
to the muscles which act. Such nerves are called motor
nerves. In every conscious act not one set of nerve cells
but hundreds — perhaps thousands — take part. General
science is not the place to study the details of the nervous
system, but rather to learn something about its control and
care. In our automobile we do not pretend to know much
about the mechanics of the engine under the hood, but we
want to know how to drive it carefully.
Unconscious activities are also controlled by the nervous
system. When we sit in the driver's seat and decide
where the car shall go, the engine goes purring along.
Water circulates through the radiator, supplies of gas
and oil are in circulation, spark plugs ignite the gas. All
these activities go on if the car is to run. So in the human
machine. As you read these words your breathing goes
on, movements of the digestive organs take place, the
making of enzymes, pumping of the heart, the regulation
Two kinds of control are illustrated here. Read your text and then try to
explain the picture.
of the body temperature — all are going on without any
conscious activity on your part. The regular activities
HOW DO WE CONTROL THE HUMAN MACHINE? 387
pineal gland
pituitary*
parathyroid
-thyroid
tWmus
liver
of the body go on without our knowing much about what
is taking place.
Two Kinds of Control. Your unconscious body con-
trol is of two sources. One is under the care of the so-
called autonomic nervous
system ; but there is another
control brought about by
some very wonderful glands
in the body. These glands
are not connected with the
food tube or other parts of
the body, but instead pour
their secretions directly into
the blood. They are called
endocrine glands. You have
heard about some of them.
The thyroid gland, for ex-
ample, sends certain messages
into the blood which causes
a greater or lesser activity
on the part of the body.
The suprarenal glands are
used at times when we are
angry, or when we wish to
make a desperate muscular effort of some sort. The
pituitary gland, a little organ no larger than a chestnut,
found at the base of the brain, controls the size of the
human body. There are several of these glands which
you will learn more about later in your study of biology,
but they have a very definite effect on the running of the
human machine. If they are in good condition, the
human machine behaves normally. If they are out of
condition, the machine may behave very badly.
Other Things that Influence Body Control. You have
all found that you could not work as well when you were
creas
spleen
adrenal
sex gland
Glands that influence body control.
Can you tell what each one shown
does for the body ?
388
THE HUMAN MACHINE
tired. This is due to the fact that the body cells, when
they do work, give off poisons and these poisons gradually
accumulate when we get overtired and cause the feeling of
fatigue. No one can do his best work when he is fatigued.
The nervous system is shocked by such poisons or by other
poisons which we take into the body. One example
would be tobacco. The effect of tobacco in general
seems very slight. It may give you a smoker's cough,
or it may seem to have no effect at all, but case experi-
ments made with the same sets of men doing work with
and without tobacco show that smoking makes for a loss
of efficiency. The same is true with overdoses of alcohol.
Here many other experiments where accuracy is needed -
such as shooting at a mark or setting type — have shown
that men without alcohol do much better work and more
work than those who have alcohol.
This apparatus is used to measure fatigue. As the finger is moved it lifts a
weight and makes marks on the revolving drum. As the finger grows more and
more fatigued the weight is lifted less distance at each effort and the marks grow
shorter and shorter. At length the finger cannot be moved and no more marks
are made. It has become too fatigued to do any more work.
HOW DO WE CONTROL THE HUMAN MACHINE?
Effective Running of the Human Machine a Matter
of Training. No one would think of trying to drive a car
in traffic unless he had learned first how to control it and
then practiced in its control. So it is when running a
human machine. Training and practice are necessary.
You may remember Uncas the Indian. It was by training
that he became acute enough to read the signs in the
forests that told him that enemies or animals had passed
that way. We learn in control by profiting by our mis-
takes. It is much more important in training that we
know when we make a mistake and profit by it than it is
to go on and luckily make no mistakes. We should
learn to be alert and cool and, once having found the right
way to act, to practice doing it so that it may become a
habit. The boy or girl who has the habit of stopping to
think before acting has done much to gain control of his
or her nervous system. In reading or listening to any one,
get the habit of paying attention to what is being said.
A wandering mind is not an alert mind. By paying
attention we avoid mistakes and avoid accidents. More
fatal driving accidents come from carelessness than from
any other cause. Above all, do your best all the time.
"Not failure but low aim is crime."
What Is Fair Play to the Nervous System ? Nerves can
stand hard work for long periods of time, provided they
get occasional rest and sleep. A transcontinental train
cannot run a long distance without changing engines.
This is done every 200 to 300 miles. In the human ma-
chine we must have occasional rest, and the best rest
comes from sleep. Scientists say that children from
eleven to twelve years of age should have from nine to
ten hours of sleep. But even more important than long
hours of sleep is the habit of taking short rest periods when
tired. Learn to relax. When we go to sleep, we relax, as
you can see if you watch a person who is just falling asleep
390
THE HUMAN MACHINE
in an upright position. The head nods. This means
that the muscles which hold the head relax and the head
drops.
Exercise in moderation is also good for the nerves be-
cause it brings oxygen to the blood by causing the heart
to pump faster and
the lungs to take in
more air. This
gives the nerves
opportunity to get
more food and oxy-
gen. But do not
exercise when tired
and do not exercise
just before meals,
for the blood then
has work to do for
the digestive tract.
Many boys of
j unior - high - school
age over-exercise in
football practice.
They are growing rapidly and their muscles are not yet
ready for such strenuous exercise. Frequently the practice
lasts until just before supper time, and they go to a meal
feeling fatigued, with the result that they have indigestion.
Cheerfulness is another important habit for the nervous
system. Look upon life from the bright side. If you
grouch, it may become a habit, and this affects others as
well as yourself. Learn to face problems fairly, not
overestimating them or underestimating them. Never
use drugs to deaden pain or stimulate the nervous system.
Pain is the symptom of faulty running. If it continues,
see a doctor. Do not let it continue to lessen the effective-
ness of your machine.
Is this a fair allotment of time for a 7th grader ?
How does your own allotment agree with this ?
HOW DO WE CONTROL THE HUMAN MACHINE? 391
Rest and Health. Our days should be made up of
work and play, rest and sleep. It is just as bad to over-
exercise as it is to underexercise. One should remember
that all machines need rest, and the human machine is no
exception to the rule. At least eight hours of sleep should
be had by every boy and girl of high school age, and nine
or ten hours of sleep by younger children. Fewer movies
and more quiet reading at home would be good for every
boy and girl. Moderation in all things is a good rule.
Overstrain of any kind brings on fatigue, and in the end
shows that we cannot strain an organ without paying for
it. If we overstrain the eyes, for example, we pay for it
by wearing glasses later. If we overstrain in athletics,
we may have to give up athletics altogether. Overfatigue
by keeping too late hours will surely call us to account
later in life. Let us learn while young the value of com-
plete relaxation, and let us, while we are growing, get the
habit of going to bed at the proper hour.
Fair play in running your own machine will result in
your being well and happy and then you will feel like
being fair to others.
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank spaces
in the sentences below and arrange the words in proper numerical order.
A word may be used more than once.
tendons thinking sheath
stimulations blood vessels autonomic
sense muscles outward
suprarenal brain control
endocrine movements thyroid
motor breathing inward
sensory cord nerves
The nervous system has the (1) of the human machine.
There is a central part made up of the (2) , spinal (3) , out-
going (4) , and another portion which consists of certain (5)
organs like the eye or organs of taste, with nerves which lead
392 THE HUMAN MACHINE
(6) and connect with the central system. The sensory nerves
receive (7) while the outgoing nerves send messages to the
(8) which result in (9) Hence they are called (10)
nerves. In addition the ordinary automatic activities of the body
such as (11) , the beating of the heart, or the (12) of the
intestines, are governed by the (13) nervous system. Certain
glands called (14) also help control bodily activities. An
example is the (15) gland, the secretions of which " pep "
up the body.
STORY TEST
JANE WRITES ON How TO CONTROL THE NERVOUS SYSTEM
Read carefully and critically. List all errors and suggest corrections.
Each one of us has a pretty big job on his hands in learning how
to control the human machine. Most of our daily acts are habit.
So first he needs to learn to do things right and then make all
of his thinking habits. He should aim high always. He should
try not to be careless for that is habit also. Cheerfulness or
grouchiness is habitual. But people cannot be habitually cheerful
if they are in pain. Therefore, it is best to take something which
will deaden pain if we have to, for in this way we can keep cheerful.
Like any machine, every so often the human body needs rest.
The nervous system gets its rest through sleep. Never take short
naps as this is wasted time. Long sleeping periods of from eleven
to twelve hours at junior high school age is what we need.
PROBLEM VI. ALCOHOL, NARCOTICS, AND THE
HUMAN MACHINE
We Have Only One Human Machine. If you had a new
car, you would not deliberately run it over the worst roads
you could find, or allow dirt and dust to mar the fine finish.
If you lived near the seashore, you would not deliberately
run the car through a pool of salt water because you know
that salt water would cause the exposed parts to rust.
How much more important is the human machine and how
much more careful we should be of it, for while we may be
able to purchase a new car when the old one is worn out,
our own body mechanism has to last us as long as we
live. We should, therefore, try to use it as efficiently as
possible and protect it from damage when we know how.
ALCOHOL, NARCOTICS, AND THE HUMAN MACHINE 393
What Fatigue Poisons Do. You have all found out that
you cannot work as well when you are tired. This is due
to the fact that as we overuse the body cells, more and
more waste products are formed and are not taken away
as quickly as they should be. These wastes are poisons
and as they accumulate in the body cells, they soon give
us a feeling of fatigue. No one can do his best work when
fatigued, and the fatigue poisons in time do great damage
to the body cells. Especially is the nervous system
damaged by poisons.
Demonstration 5. Effect of Cigarette Smoke upon Fish.
Prepare a cigarette smoker as follows : Heat the end of a glass
tube and insert the end of a file and ream out the end, making it
flaring so it will hold the end of a cigarette (A). Bend the tube
to make a narrow loop. Connect the other end at C to a tube
going nearly to the bottom of a Florence flask. Fill this flask
just over half full of water and put a goldfish in it. Connect the
flask to a two-liter bottle (E) by means of tube D. Fill E with
water and arrange tube to siphon water out of E. By opening
clamp F and blowing into A, the siphon tube is easily filled. Close
clamp. Insert cigarette at A. Open F and light the cigarette.
As water runs out of E, smoke will bubble through the water W,
394 THE HUMAN MACHINE
Not all the products of burning pass into the water. Notice
matter collected in the coiled tube at B. After the fish shows the
effects of the smoke, transfer it to a bowl of fresh water. Note
the appearance and odor of the liquid at B. What becomes of
this product when one smokes a cigarette ?
What a Great Athletic Director Has to Say about To-
bacco. The following letter which was sent by A. A. Stagg
to a teacher in the Wellesley Junior High School, Wellesley,
Mass., speaks for itself. Anyone who has followed his
teams on the west coast knows that he is still a coach
whose teams play the game as good sportsmen should.
The University of Chicago l
Department of Physical Culture and Athletics
Office of the Director
December 9, 1931
From personal observation of athletes who have been addicted to the
use of tobacco, I can speak with confidence, that, as a rule, they do not
possess the endurance of athletes who have grown up free from the use
of it. Few people smoke without inhaling, which means that eight
times as much of the nicotine poison goes into their systems, according
to recent experiments by a German scientist, than from the use of
tobacco without inhaling. One of the leading physicians of Chicago
has personally told me that since he started smoking, his pulse has
gone up ten to twelve beats, and another physician, to whom I told
this, has confirmed it by his personal experience.
Outside of the matter of endurance, I have no exact data, but I am
strongly of the opinion that athletes who have used tobacco would not
have as steady nerves in tight pinches as non-users.
The Danger from the Narcotic Poison, Nicotine. Just
as fatigue poisons damage the human machine so do other
poisons damage it. You have often heard older people
say when they were tired, that a good smoke rested them.
It seems to rest them, for tobacco contains a narcotic
poison called nicotine. Any narcotic deadens the senses
and soothes a person into believing he is rested, but along
with this comes the effect of the poison in the body.
1 From Manual for Teaching Effects of Alcohol, Stimulants and Narcotics
upon the Human Body. Commonwealth of Massachusetts, Department
of Education,
ALCOHOL, NARCOTICS, AND THE HUMAN MACHINE 395
While tobacco may not seem to do any great harm to
smokers, it does harm people in the long run. One
Russian investigator compelled certain rabbits to smoke
A study made at Yale University showed that 5 per cent of the honor men, 60 per
cent of the average men, and 73 per cent of the failures were smokers.
cigarettes for periods of from 6 to 8 hours daily, with the
result that some of the rabbits died within a month's time,
showing heart changes. Others developed tolerance for
tobacco like human smokers, but when they were killed,
they showed degeneration of the blood vessels. Doctors
who have made a study of the effect of tobacco on the
human system find that cigarette smoking causes an
increase in the heart rate and a heightened blood pressure
which indicate the effect of the poison. The fact that
heart trouble is increasing in this country makes us wonder
if it has anything to do with the increase in the use of
cigarettes which has taken place since women have taken
up smoking.
Smokers Do Not Have as Good Chances at Athletics.
While a smoker may not have smoker's cough or may not
seem to show any loss of mental efficiency, yet studies of
mental and physical efficiency indicate that the smoker is
at a disadvantage. Certain statistics were gathered by a
professor at the University of Utah in which he grouped
students competing for places on the football teams in six
institutions into groups of smokers and non-smokers.
He found that only half as many smokers made the teams
396 THE HUMAN MACHINE
as non-smokers, that the smokers showed a loss of lung
capacity amounting to about 10 per cent as compared with
the non-smokers, and in almost every case the non-smokers
showed higher scholarship. Since there were over 200
men involved in this experiment, the figures ought to be
worth something. Other experiments have shown that
runners, especially distance runners, do not have as good
chances of winning if they are smokers. Many coaches
ask runners and football men to cut out smoking while
in training because of the effect on their wind. An experi-
ment by Professor Lombard of the University of Michigan
showed that on days he smoked his muscles lost 41 per
cent of their working power. So this looks as if the
coaches were right.
Tobacco May Cause Serious Injury. One insurance
company has figures based upon 180,000 policyholders
which show that the abstinents from tobacco had almost
twice as much likelihood of living to old age as those who
smoked moderately all their lives. Dyspepsia, catarrhal
Wright Pierce
Successful football coaches forbid the use of alcohol and tobacco among the
members of their teams. Why are such teams usually successful ?
ALCOHOL, NARCOTICS, AND THE HUMAN MACHINE 397
conditions of the nose and throat, and sleeplessness are
some of the afflictions brought on by excessive smoking.
Here are certainly enough reasons to show young people
that the game isn't worth the candle.
What about the Harm Done by Alcohol? Anyone
living in the world today knows the value of being alert and
wide awake. No one who is interested in science would try
to handicap himself at the start of life by dulling his mind
and causing his muscles to lose their control. But that
is exactly what the drinker does when he gets the alcohol
habit. But you say : "If I drink, I'll know when to stop,
and besides a little drinking never hurts any one." Sci-
ence cannot agree with this statement. Alcohol is a nar-
cotic drug and as such it is a habit-forming drug. In small
quantities it may be used in the body much as an energy
food is used, but unfortunately it has a narcotic effect
as well. It seems to be able to deceive us by making us
think we are stronger, more sensitive, and more efficient
than we really are. It does this because of its narcotic
or deadening effect. It is this fact about drinking alcohol
that makes it so dangerous, for one soon becomes incapable
of forming accurate judgment. He throws caution aside,
takes chances, and makes errors. In an age when restraint
and caution are needed in driving a car or crossing a
crowded street, or doing the hundred and one things one
has to do in a crowded city, it is evident that the drinker
is at a decided disadvantage.
Alcohol Acts on the Nervous System. There is plenty
of evidence that alcohol acting on the nervous system slows
up the action of muscles, makes us react slower, and causes
the loss of muscular control. You have doubtless noticed
this effect in anyone under the influence of liquor. More
than this, it blunts the ability to judge one's own actions,
thus relaxing self-restraint and allowing one's emotions
to rule his will or intellect.
398 THE HUMAN MACHINE
Alcohol Damages the Body Machine. More serious
still is the effect of alcohol upon the body machine. Alco-
hol taken in excess shortens life very considerably by
undermining the structure of the digestive tract, liver,
kidneys, blood vessels, and nerves. It slows muscular
efficiency, as can be shown by experiments in mountain
climbing, digging ditches, carrying weights, etc. In all of
these experiments the subjects without alcohol did more
work and did it better. It makes for inefficiency in any
work where judgment and skill are involved, such as
typing, drawing, or using machines. It slows up all
mental work and makes it less accurate, although the
person believes he is doing better work. No boy or girl
who wants success in life can take a chance with alcohol.
SELF-TESTING EXERCISE
Select from the following list of words those which best fill the blank
spaces below and arrange them in proper numerical order. A word
may be used more than once.
smoker nicotine less wealth
success strong heart drinker
money food same alcohol
body failure fatigue athletics
health scholarship feet narcotic
more cells machine heavy
nervous life efficiency light
When a person feels tired, it is because (1) poisons have been
formed in the (2) of the (3) A (4) poison such as
(5) which is found in tobacco acts in much the (6) way.
Smoking is a bad habit because it not only wastes (7) but it also
lowers one's (8) It does this through its effect on the (9)
and (10) system. Smokers in college do not have as much chance
in (11) or (12) , according to statistics as do non-smokers,
and their chances of good (13) are (14) than of non-smokers.
The same may be said about the use of (15) Not only does it
harm the human (16) , but it handicaps the (17) so severely
that his chances of (18) in life are not to be compared with those
of the non-drinker.
SAFETY EDUCATION AND FIRST AID 399
STORY TEST
NED TELLS OF SOME DANGERS FROM SMOKING
Read carefully and critically. List errors and suggest corrections.
I used to think because my father smokes that I would, but I have
changed my mind. In the first place, I tried it one day and it made me
beastly sick. About this time we made an experiment in school. The
teacher took one drop of nicotine which he got from an old pipe and
stirred it up in a small bowl of water and then placed in it one of the
goldfish from our school aquarium. It took just about five minutes
to kill that fish. Well, that gave me a reason for being so sick after
my first smoke. So I decided to investigate farther and do a little
reading. I found that all tobacco contains nicotine and that it passes
into the mouth with the smoke. Of course if you inhale, you carry
some of it down into your lungs and that's just too bad, for sooner or
later it poisons the tissues there. That I suppose accounts for the
shortness of wind that the smoker often has. According to a number
of experiments my teacher showed me, the smoker doesn't do as well
in athletics or in scholarship as the non-smoker. And I also read that
in Yale, I think it was, that non-smokers had smaller lung capacity
than smokers, and were shorter and smaller. I got enough dope to
make me feel certain that I don't care to try smoking now and I
doubt if I will want to smoke when I get older, for it takes a lot of
money that I could use to better advantage.
PROBLEM VII. WHAT IS THE IMPORTANCE
OF SAFETY EDUCATION AND FIRST AID?
Why Safety Education Is Important. Did you know
that last year over 34,000 people were killed in various
traffic accidents ; over 27,000 met their death in various
industrial accidents ; 13,000 more were killed by falls ;
and more than 6000 by burns and drowning? Over
90,000 people were killed, around 2,000,000 seriously
injured, and no one knows how many slightly injured
in one year. It is estimated that one out of every eleven
of the 23,000,000 motor vehicles registered in this country
is in an accident each year. In 1927, according to the
United States mortality statistics, while there was a
decrease in all other accidental deaths, in children of high
400
THE HUMAN MACHINE
bwr-ns
X'/of all
"-y0 accidents
are personal
^ happen, in,
our "
•xyof accidents
fire-avTns
clrov/rtirjcf
matches
due/to fopd. poison
vincCovs
^/<> occur in-
cur schools
traffic/
due "to falls
games
?f all
aooid^»ts-
ana public ones
29^
machinery
ions
autos-
airplanes
explosions
ofoccidents
occur in- cfeceto
of ,
buildCmgs
Classification of accidents in the United
States.
school age between the
years 1917 and 1927
there was an increase of
nearly 17 per cent in the
deaths from auto acci-
dents and today con-
ditions are worse.
While the school can-
not be expected to teach
you to drive a car safely,
it can point out some of
the commonest forms of
accidents and help you
to avoid them. In 1933,
in a total of 756,500
auto accidents in which
the driver was at fault,
it was found that over 575,300 people were killed and
injured. The accidents that took the greatest toll of
life and injury were in order these : (1) exceeding speed
limit, (2) car did not have right of way, (3) car was on
wrong side of road, (4) driving off roadway in traffic. Of
the eleven listed accident causes, they constituted three
quarters of all accidents. These then point out some
definite things that
young drivers should
do. Most accidents
occur at intersections.
Always slow up and
have your car under
control. Carelessness
at such places on the
part of the driver is
the biggest cause of K we ^ more verdicts Uke this we would have
accidents. Keep alert fewer reckless drivers.
\ForRECKLESS DRIVING
ASSAULT With a
DEADLYQTEAPON
SAFETY EDUCATION AND FIRST AID
401
and watch for what the other fellow may do. Do not
speed ; it is better to be safe than sorry. Brakes sud-
denly applied may mean a skid, a crash, and broken
bones or worse. If you hope to drive without injuring
others, you must drive carefully. Especially accidents
are likely to come when young people cut in, fail to use
hand signals, fail to stop at signals or a dangerous cross
street. Nearly 10,000 people are killed or injured each
year on grade crossings. It pays to stop, look, and
listen.
What Are the Most Common Accidents to Pedestrians ?
It has been found that about one third of all pedestrian
accidents occur at street crossings where there is no signal,
about one quarter come from crossing between inter-
sections, and about one fifth come from playing or riding
bicycles in the street. This latter figure is increasing now
that more boys and girls ride wheels. It is also found that
" jay walking" is responsible for a very large percentage of
injuries. These facts show us the importance of watching
our step while on the street. Playing games in the street,
unless it is closed to traffic, is a risky occupation.
212
198
153
143
CHIEF CAUSES OF FATALITIES
IN STREET ACCIDENTS
FOR THE YEAR 1933
SAFETY BUREAU
POLICE DEPARTMENT
CITY OF NEW YORK
& £ 47 ^
I I I I I • • •
C ra
127
This is a typical graph. What can you do about it ?
H. & w. sci. i—27
402
THE HUMAN MACHINE
What Can We Do to Prevent Accidents? We can
co-operate with city and state in observing traffic regu-
lations. We can aid in the direction of the traffic near
the schools by estab-
lishing traffic and
patrol squads and by
helping control traffic
at times of congestion.
We can organize safety
campaigns and give
personal demonstra-
tions on how to behave
safely and sanely.
And, most of all, we
can personally be care-
ful, for by far the
greatest number of
accidents come through
carelessness.
Have you a traffic squad in your school? What to Do Ul Case
of Accidents. In spite
of everything, accidents do occur on the street, at school,
and at home. Statistics show that in large high school
systems — such as St. Louis and Los Angeles — the per-
centage of accidents based on their enrollment is over
1 per cent of the school population. Accidents happen
in playing games, in the shops and laboratories, and on the
school grounds. At home we have falls and burns taking
a large toll. Suffocation and electric shock are frequent
causes of death. Especially among high school boys and
girls drowning accidents play a large part, over 30 per cent
of all deaths coming from this cause. First and most
important, we should keep cool. If the accident is serious,
do what you can in first aid and send at once for a physi-
cian. A knowledge of first aid is important for every
SAFETY EDUCATION AND FIRST AID
403
boy and girl, and each one of us should know what to do in
case of a bad cut, broken bones, or suffocation from drown-
ing, fire, and other causes. The paragraphs that follow
will help us to cut the
toll of death from these
accidents.
What to Do in Case
of Drowning. In the
case of drowning, electric
shock, or poisoning by
gas, the treatment is by
artificial respiration. The
prone-pressure method is
easily learned and is
generally used. In the
case of apparent drown-
ing, the first thing to do
is to get the water out of
the lungs and air passages.
To do this raise the lower
part of the body of the
patient from the ground
so that the water may
run out. With the arms
underneath the abdomen
lift the patient up quickly
two or three times with a jerk. Water from the lungs will
thus be forced out. Do not take more than half a minute
to do this. Place the patient on the ground face down,
and with head turned to one side and resting on an arm.
Kneel astride of the patient, and place the palms of your
hands across the small of his back, thumbs touching.
Allow your weight to fall on your wrists by bending your
body slowly forward. Now release the pressure by swing-
ing backward. Continue these motions for four or five
Read the text carefully and then explain
the diagrams.
404 THE HUMAN MACHINE
seconds at a time, at about the rate that one breathes.
Victims of drowning accidents have been brought back
to life after hours of work. If there are other persons to
help, have them rub the arms and legs of the patient
toward the body, as this helps the circulation. When
respiration is restored, cover the patient with warm blan-
kets and place hot-water bags at the hands and feet.
After consciousness has returned warm drinks may be
given.
What to Do in Case of Suffocation and Electric Shock.
In case of suffocation, where the patient has lost con-
sciousness, start artificial respiration, and send for a doctor
at once. In case of electric shock a rescue must be effected
first. Remember that live wires can transfer electricity
through the body of the victim to you. To prevent
receiving a shock, it is necessary to stand on dry wood,
cloth, or rubber, and remove the wire with a piece of dry
wood, or cut it with an ax having a dry wooden handle.
If the patient is lying on the wire, place coats under his
head and feet and lift him off. As soon as you have
rescued the victim start artificial respiration at once, for
time is a very important factor, especially if he has become
unconscious. Treatment for lightning shock is the same
as for electric shock.
What to Do in Case of Sunstroke or Fainting. Sun-
stroke and heat exhaustion are usually brought about by
working in excessive heat, either indoors or out of doors.
Too heavy clothing and hats which do not protect the
head from the sun's rays help bring on this condition.
The results are often very serious, and anyone feeling
the effect of the heat either as dizziness and weakness
(which are the symptoms of heat exhaustion) or pain
in the head and great oppression (the symptoms of sun-
stroke) should lie down at once. The necessary thing to
do is to reduce the body temperature as quickly as possible.
SAFETY EDUCATION AND FIRST AID
405
Do this by applying ice to the head and the chest, or by
giving the victim a cool bath. In the case of heat ex-
haustion, such stimulants as tea, coffee, or aromatic spirits
of ammonia may be given.
A fainting attack is brought on by a decrease in the
amount of blood in the brain. A person feeling dizzy
should lie down with the head slightly lower than the
rest of the body. Give him plenty of fresh air and loosen
his clothing. Respiration may be stimulated by putting
cold water upon the face and chest. Aromatic spirits
of ammonia may be inhaled.
What to Do in Accidents Where Bones Are Broken.
In case of broken bones, the first thing to do is to put
the patient in as comfortable a position as possible, and
then send for a doctor. If some time must elapse before
a doctor can treat the fracture, make smooth splints
of wood and tie them about the broken bone with strips
of any cloth or a
necktie. Remem-
ber that the broken
bones must be held
as nearly as pos-
sible in a natural
position and must
not be allowed to
move about. Trans-
portation of the
patient must be
done with the greatest care in order to have no move-
ment of the broken bones.
Practical Exercise. Make a demonstration before the class of
first-aid treatment of a broken leg, broken collar bone, or a dislo-
cated finger.
What to Do to Stop Bleeding. Frequently a person's
life may be saved if one knows what to do and can act
A temporary bandage for a broken arm. Why
must the arm be kept immobile?
406
THE HUMAN MACHINE
quickly. Wounds that bleed steadily, even if they are
deep, are not necessarily dangerous and may usually be
controlled by placing the wounded person flat on the back
and binding a pad or wad of sterile gauze or any clean
cloth over the wound.
But if the blood comes
in spurts and is bright
red, an artery has been
cut. This means that
pressure should be ap-
plied between the cut
and the heart. You can
sometimes do this with
your fingers. If the cut
is in a limb, a tourniquet
(toor'ni-ket), made by
knotting a handkerchief
and twisting it tightly by
means of a stick so the
knot presses on the
artery, can be used. A
physician should be ob-
tained at the earliest pos-
sible moment and the patient kept absolutely quiet. Open
wounds must be kept clean. If a wound is covered with
a bandage or compress of gauze, it is very important that
such material be absolutely clean. Washing the surface
of the wound to get out the dirt is necessary, and if iodine
or Mercurochrome is available, pour some over the open
surface of the wound. The chief danger from a cut or
wound is that germs may get in and start an infection.
Therefore, cleanliness is the first need.
What to Do for Burns. Burns are often very serious
because of the difficulty of getting them to heal. Slight
burns may be healed by excluding the air with a thin
What two methods of treating cuts are
shown here ? Why the difference ?
SAFETY EDUCATION AND FIRST AID 407
paste of baking soda and a little water. Put on a light
bandage to keep this paste in place. Severe burns require
the attention of a physician. A picric acid dressing may
be used for immediate relief, after the clothes have been
cut away or removed.
How to Treat Poisons. In case of a poisonous snake
bite, open the wound at once to induce free bleeding;
wash it with potassium permanganate, and give the person
strong doses of a stimulant, such as aromatic spirits of
ammonia. Antivenin serum should be administered as
soon as possible, as the poison works very quickly. Poison
ivy is relieved by washing the surface with a solution of
potassium permanganate. In all poisons taken into the
stomach give an emetic 1 at once. A good plan is to
first give raw white of egg in water or milk, followed by
warm salt water, mustard water, or anything to get the
poison out of the stomach. The emetic will usually be
suggested on the label of the bottle containing the poison.
Exceptions to the general rule for emetics are that no
emetics should be given with strong acids or alkalies.
In this case we must apply our knowledge of household
chemistry. Acids and bases should be neutralized, using
soda or dilute ammonia for acids and vinegar or lemon
juice for alkalies.
Home Medicine Chest. A few simple remedies should be kept
at home in order to take care of simple ailments. The following
supplies are suggested :
Alcohol, 4 ounces Soda mint tablets, 100 tablets
Aromatic spirits of ammonia Adhesive tape, 1 spool
(rubber cork) Antiseptic gauze, 1 package
Castor oil, 4 ounces Absorbent cotton, \ pound
Limewater, 2 ounces Gauze bandages, 6 rolls, various
Witch hazel, 4 ounces widths
Carbolized vaseline, 1 tube First-aid outfits (Red Cross), 2
Iodine and Mercurochrome
(6-m6t'ik) : inducing to vomit.
408 THE HUMAN MACHINE
SELF-TESTING EXERCISE
Select from the following list those words which best fill the blank
spaces in the sentences below and arrange the words in proper numerical
order. A word may be used more than once.
less flat intersections between
back motionless wrong drowning
upright fewer prone air
roadside side bandage way
cool pressure more means
hot beside stimulants tourniquet
right splint pedestrians emetic
Motor accidents kill and maim (1) children than any other
one cause. Most accidents occur at (2) of streets. Therefore,
we should be alert and be sure we have (3) of (4) there.
Most accidents to (5) also occur at intersections. In case
of accident we should keep (6) and be able to use first aid
when it is necessary. In apparent drowning the (7) (8)
method of artificial respiration is best. In case of sunstroke or
fainting place the patient (9) on the (10) , give (11) ,
as aromatic spirits of ammonia, and plenty of fresh (12)
In case of a broken bone make a (13) so as to keep the bone
(14) until a doctor comes. In case of a cut artery a (15)
applied (16) the heart and the wound may save a life. In
cases of poisons which are not strong acids or alkalies give an (17)
PROBLEM TESTS
Test 1. Check the statement or statements which best answer the
problem.
You stop at a filling station to get gasoline and leave your engine
running. The attendant asks you to turn off the switch. Why
does he do this ? He does it because :
(1) You are wasting gasoline.
(2) He might be overcome by carbon monoxide while filling the
tank.
(3) The exhaust might ignite fumes from the open tank of
gasoline.
(4) The noise of the engine makes it hard for him to ask you the
necessary questions about service.
(5) It is bad for the engine to let it idle.
SAFETY EDUCATION AND FIRST AID
409
Test 2. Study the dia-
gram carefully before
answering the ques-
tion.
You get off a street car
going south and walk
around the back of the
car to cross to the east
side of the street. As
you step out from behind
the car, you are knocked
down by an auto which
is going fifteen miles an
hour in a northerly
direction. Who is at
fault in this accident
and why?
Vest
North
THE REVIEW SUMMARY
The generalizations that can be made on this unit are numerous.
You may change the list that follows if you so desire, as this is
giving you only a partial list of those that you might make for
your review summary. Some of the generalizations are :
•
1. The human body is a self-direction machine which oxidizes
fuel to release energy.
2. The nervous system controls the human machine.
3. The skin is a heat-regulating apparatus which also protects
the body.
4. Bones act as levers while muscles exert power and give us
movement of the body machine.
5. Food must be digested before it can be used by the body.
6. At the present time automobiles are our greatest sources of
accidents.
Before making your review summary, test your knowledge of
the facts of the unit by checking over the text so as to be sure you
know the facts underlying the generalizations. Then, using the
generalizations, the material in the text, and everything you have
read, seen, or done yourself, make a summary outline for your
notebook. This outline you may use when you make a recitation.
410 THE HUMAN MACHINE
TEST ON FUNDAMENTAL CONCEPTS
Make two vertical columns in your workbook. Head one CORRECT
and the other INCORRECT. Under the first place the numbers of all state-
ments you believe to be correct. Under the second place all the numbers
of the statements you believe to be incorrect. Your grade = right answers
X2.
I. The human machine is like an automobile because : (1) both
use fuel to release energy; (2) both have a protective covering;
(3) both possess the same building material; (4) both form wastes
that have to be removed ; (5) both have a framework.
II. The human machine is unlike an automobile because:
(6) one is self-directed, the other not ; (7) both can be self -repaired ;
(8) one is a perfect machine, the other is not ; (9) one is made
entirely of one material, the other is not; (10) one needs air, the
other does not.
III. The skin : (11) is an organ of heat production ; (12) should
be powdered frequently so as to keep dirt out of the pores ; (13) is a
means of individual protection; (14) regulates body temperatures
by means of the sweat glands; (15) is a dead covering.
IV. Bodily movement is accomplished: (16) by the expansion
of blood in the muscles ; (17) by the contraction and relaxing of
muscles alone; (18) by means of muscles attached to bones which
act as levers; (19) better with high-heeled shoes; (20) in part by
means of the ligaments and tendons.
V. The human machine uses food: (21) to make new parts;
(22) to repair old parts; (23) in the stomach; (24) to release
energy in the cells; (25) because it.tastes good.
VI. Good health is largely determined by : (26) a strong consti-
tution ; (27) living in the country : (28) getting at least 12 hours
sleep every night; (29) getting recreation, work, and rest each
day ; (30) cheerfulness, optimism, and common sense.
VII. Digestion is necessary: (31) in order to make the food
taste good ; (32) in order to get the food out of the food tube ;
(33) if the blood is to be supplied with food ; (34) in order to get
food into the cells ; (35) if work is to be done by the body.
VIII. Your personal habits : (36) do not ever affect others ;
(37) may affect others if you are sick ; (38) largely determine the
state of your own health ; (39) should make for clean living and
clean thinking; (40) should be centered on making your clothes
and person as attractive as possible.
IX. The human machine: (41) is controlled by the nervous
system ; (42) is entirely directed by stimuli from without ; (43) is
entirely directed by our thoughts; (44) is controlled entirely by
endocrine glands ; (45) is controlled by all of the above.
SAFETY EDUCATION AND FIRST AID 411
X. Safety education and first aid are important because:
(46) children's deaths from accidents are increasing; (47) you
never can tell when an accident will occur; (48) rattlesnakes are
numerous in the deserts of the West ; (49) over 90,000 people died
and 200,000 were injured in accidents last year ; (50) over 1 per cent
of all boys and girls in school are hurt in accidents every year.
THOUGHT QUESTIONS
1. Constance is fifteen pounds under weight. What should
she do to gain her normal weight ?
2. Clara weighs ten pounds more than normal and wants to
go on a diet. What should she do ?
3. George is growing rapidly, has stoop shoulders, and a flat
chest. He is more than 10 per cent under weight. He is a good
runner and wants to try out for end on the school team. What
should he do about it?
4. John is playing guard in basket ball but weighs fifteen pounds
less than the coach thinks he should. What should he do to bring
up his weight ?
5. Should Tom, who is fifteen and growing rapidly, break train-
ing after the football season is over? Justify your answer.
6. What can you do to decrease auto accidents ?
7. Why must food be digested before it can be used in the body ?
8. What would you do if you were alone with a friend who met
an accident in which his arm was broken and an artery severed in
the same arm near the break?
9. What would you do in case of a fire in the motion picture
projector used in the science room?
10. What would you do if you were alone in the laboratory and
should be severely burned by acids?
REPORTS UPON OUTSIDE THINGS I HAVE READ,
DONE, OR SEEN
1. Report upon an article related to some topic discussed in
this unit. The article may be from a current number of a science
magazine or from some popular science book you have read.
2. The value of pain.
3. Comparison of skeletons of different kinds of animals.
4. Do animals think?
5. Automobile accidents in my state for the last year and how
they might have been lessened in number.
6. Under what conditions might narcotics be useful? If useful,
who should use them?
THE HUMAN MACHINE
SCIENCE RECREATION
1. Make a series of your own finger prints, right and left hands.
Compare them with prints of other members of your class.
2. Find examples of joints in the skeleton. There are three
kinds : ball and socket, hinge joints, and sutures, such as are found
in the skull.
3. Locate in your own mouth the position and number of each
of the following kinds of teeth : incisors, or cutting ; canines, or
tearing ; molars, or grinding.
4. Make a list of the tissues of the body and locate them on a
diagram.
5. Learn to use different kinds of bandages, especially the tri-
angular and roller bandages.
6. Keep a monthly record as suggested in the following table
to form correct health habits.
^IONTHLY RECORD
10
1. Age
2. Weight
3. Height
4. Chest measure
(1) Expanded
(2) Contracted
(3) Chest expansion =
5. Lung capacity
6. Time can hold breath
7. Eye test
8. Hearing
9. Grip test
10. Lifting strength
SCIENCE CLUB ACTIVITIES
1. Plan a safety first assembly to be given by the club.
2. Organize a safety patrol to control traffic and pedestrians
outside the school grounds.
3. Organize a first-aid club.
4. Make a chart for use in the science room, giving a list of all
the common poisons and the proper treatment for each.
5. Compare the first aid cabinets in the school with ideal medicine
cabinets and make efforts to make them as near perfect as possible.
6. Plan the equipment for an ideal school rest room and start one.
SAFETY EDUCATION AND FIRST AID 413
REFERENCE READING
Elwyn, A., Yourself Incorporated: The Story of the Human Body
Coward-McCann, 1930.
Fisher, I., and Fisk, E. L., How to Live. Funk and Wagnalls, 1932.
Hartman, L. L., Teeth and Mouth. Appleton, 1927.
Kellogg, J. H., The Itinerary of a Breakfast. Funk and Wagnalls, 1926.
Lewin, P., Posture and Hygiene of the Feet. Funk and Wagnalls, 1929.
McCarthy, J. D., Health and Efficiency. Holt, 1921.
Strickler, A., The Skin: Its Care and Treatment. Appleton, 1927.
Towns, C. B., Habits That Handicap. Funk and Wagnalls, 1920.
GLOSSARY
GLOSSARY OF IMPORTANT TERMS
The diacritical marks are those used in the Webster school dictionaries.
Absorbed (ab-sorbd') : taken in.
Accommodation (a-k6m'6-da'shwn) :
adapting the lens of the eyes for
near and distant vision.
Adaptation (ad'ap-ta'shwn) : modifi-
cation of a plant or animal fitting
it more perfectly to live in its
environment.
Alkali (al'kd-ll) : a substance having
marked basic qualities, including
ability to turn red litmus blue.
Ammonium chloride (a-mo'nl-#m
klo'rid) : a chemical compound.
Amphibian (am-ftb'I-tm) : an animal
that spends part of its life in the
water and part on land, as frogs
and toads.
Aphid (a'ftd) : a plant louse.
Aquarium (d-kwa'rl-#m) : a glass
tank of water.
Archimedes (ar'M-me'dez) : a Greek
scientist.
Arcturus (ark-tu'r#s) : a first-magni-
tude star.
Artery (ar'ter-I) : one of the large
tubes which carry blood from the
heart to various parts of the body.
Astigmatism (d-stlg'md-tfz'm) : a
defect of the eye which causes
imperfect images.
Astrologer (as-tr6l'6-jer) : one pro-
fessing to foretell events by aspects
of the stars.
Astronomer (as-tr6n'6-mer) : one
having knowledge of the heavenly
bodies.
Atom (at'#m) : the smallest particle
of a substance that can exist.
Atomizer (at'&m-lz'er) : an instru-
ment to make a fine spray.
Bacteria (bak-te'ri-d) : a certain
group of microscopic plants, some
of which cause diseases.
Bacteriologist (bak-te'ri-61'6-jM) : an
expert in the study of bacteria.
Bootes (b6-6'tez) : the constellation
containing Arcturus.
Brontpsaurus (br6n't6-so'rws) : an
extinct animal of huge size.
Buoy (boi) : to keep from sinking.
Calorie (kal'6-rf) : the amount of
heat necessary to warm 1 kilogram
of water 1° C. or about 4 pounds
of water 1° F.
Calorimeter (kal'o-rnii'e'-ter) : appa-
ratus for measuring amount of
heat in foods.
Calyx (ka'llks): the outer floral
leaves of a flower. All the sepals
taken together.
Capillaries (kap'I-la-rlz) : fine, hair-
like tubes ; the very small blood
vessels through which the blood
flows from the arteries to the
veins.
Carbohydrate (kar'b6-hl'drat) : a
group of compounds containing
carbon, hydrogen, and oxygen, as
sugar and starch.
Carnivorous (kar-nlv'6-rws) : living
on flesh.
Cartilage (kar'tl-laj) : a translucent
elastic tissue.
Cassiopeia (kiis'I-6-pe'ya) : name of
a constellation.
Celestial (sg-leVchal) : pertaining to
the sky or visible heavens.
Cell (s£l.) : a small structural unit of
which plants and animals are corn-
Cellophane (sel'6-fan) : a transpar-
ent wrapping "paper" having the
composition of rayon.
Centigrade (s&n'tl-grad) : name of
metric thermometer, on which the
distance between the freezing
point and boiling is divided into
100 parts or degrees.
Chaparral (chap'd-ral') : a dense
thicket of stiff or thorny shrubs.
Chlorophyll (klo'ro-fll) : the green
coloring matter of plants.
Circulation (sur'ku-la'sh#n) : the
Erocess by which oxygen and blood
ow to all parts of the body.
Combustion (kdm-bus'chtin) : act of
burning.
Compound: substance formed by
the chemical union of elements.
Concave : curving inward like the
inside of a ball.
H. & w. sci. i — 28
417
418
GLOSSARY OP IMPORTANT TERMS
Condensation (k6n'd£n-sa'shwn) :
changing from gas to liquid.
Condensed (k<5n-de"nst') : changed
from a vapor or gas to a liquid.
Conduction (kdn-dtik'sh#n) : passing
from particle to particle, as heat.
Conifer (ko'nl-fer) : cone-bearing
tree.
Constellation (k6n'st£-la'sh#n) : a
group of fixed stars.
Convection (kon-veVshun) : transfer
of heat by currents in gases or
liquids.
Convex (k6n've"ks) : curving out-
ward ; opposite to concave.
Copernicus (ko-pur'nl-kws) : an as-
tronomer (1473-1543) who first
explained that the apparent rota-
tion of the heavens was due to the
rotation of the earth.
Corolla (k6-r51'd) : the inner petals
of a flower.
Corpuscle (kor'ptis'l) : a minute cell
in the blood or lymph.
Cotyledon (k&tl-le'dfln) : the first
leaf or pair of leaves developed in
seed plants.
Crustacean (krus-ta'shan) : seg-
mented animal with jointed legs
and a crustlike shell.
Cylinder (sil'm-der) : the chamber
in an engine in which the piston
moves.
Daguerreotype (dd-ge"r'6-tip) : an
early variety of photograph.
Deciduous (de"-sld'u-ws) : shedding
leaves in winter. ^"^
Diaphragm (dl'd-fram) : a vibrating
disk or membrane as in the tele-
phone. Muscular partition sepa-
rating the chest cavity from the
abdomen.
Diffused (dl-fuzd') : spread.
Diffusion (dl-fu'zMn) : the mixing
of the particles of two substances
in solution.
Digest (dl-j6sf) : to change food into
a form that the blood can absorb.
Diphtheria (dlf-the'rf-d) : an infec-
tious disease of the throat.
Disinfect (dls'm-fekt') : to purify by
killing the germs of disease.
Distillation (dls'tl-la'shun) : act of
driving off gas from liquids and
then condensing the gas by cooling.
Dormant (ddr'mtfnt) : inactive.
Electrolysis (e-lek-tr6l'l-sls) : the
separation of a compound into its
parts by means of an electric cur-
rent.
Electron (S-lek'tr&n) : that part of
an atom that carries a negative
charge of electricity.
Element (ei'fi-m&it) : a substance
that cannot be broken up into
simpler substances.
Embryo (Sm'brl-o) : an organism in
early stages of development.
Emulsion (e-mul'shwn) : a liquid
preparation in which minute par-
ticles remain in suspension.
Endocrine (e"n'd6-krin) : organs
which secrete fluids.
Energy (e"n'er-jl) : the capacity to do
work.
Environment (Sn-vl'rftn-mgnt) : sur-
rounding conditions or influ-
ences.
Enzyme (e'n'zlm) : a substance which
effects certain chemical changes.
Epidermis (Sp'I-dur'mls) : outer
layer of the skin.
Eradicate (e-rad'I-kaf) : to destroy
utterly.
Erosion (g-ro'zrmn) : the process by
which rocks and soil are scoured off
and carried away by water.
Evaporation (e"-vap'6-ra'sh#n) : act
of changing a solid or a liquid to a
vapor.
Exhale (Sks-hal') : to breathe out.
Exhilaration (eg-zfl'd-ra'sh&n) : act
of being enlivened or made
glad.
Expiration (Sks'pl-ra'shun) : passing
air out of the lungs.
Explosion (e"ks-plo'zh#n) : a sudden
bursting from great pressure.
Factor (fak'ter) : one of the parts of
a product.
Fahrenheit (fa'r£n-hlt) : a thermom-
eter in which the freezing point of
water is 32° and the boiling point
is 212°.
Fatigue (fd-teg') : exhaustion of
strength.
Fermentation (fur-m6n-ta'shiin) : the
production of alcohol and carbon
dioxide by the action of yeast.
Fertilization (fur'ti-ll-za'srmn) : the
union of a male germ cell with the
female germ cell or egg.
GLOSSARY OF IMPORTANT TERMS
419
Fluctuation (fluk'tft-a'shwn) : vary-
ing or changing in strength of
current.
Focus (fo'kws) : a point at which
rays as of light, heat, sound, etc.,
meet, after being reflected or
refracted.
Fossil (f6s'Il) : remains or impres-
sions of a living thing preserved
in rock of ancient date.
Friction (frlk'shwn) : act of rubbing
one thing against another.
Geologist (je-6T6-jfet) : a geological
student or investigator.
Germ (jurm) : a small plant or
animal that may produce dis-
ease.
Germinate (jur'mJ-nat) : to begin to
grow, to sprout.
Geyser (gi'ser) : a spring which
throws intermittent jets of hot
water.
Glacier (gla'sher) : a slowly moving
body or field of ice.
Gland : an organ of the body which
makes and gives off a fluid.
Gravity (grav'I-ti) : the pull of the
earth upon objects.
Gyrocompass (ji'rd-kum'pds) : a
non-magnetic compass.
Hazards (haz'drds) : dangers.
Herbivorous (hgr-biv'6-r#s) : living
on plants.
Huygens (hi'ge'nz) : a Dutch astron-
omer (1629-1695).
Hyacinth (hi'd-smth) : a garden
plant.
Hydra (hi'drd) : a small fresh-water
animal.
Hygiene (hi'jl-en) : a study of the
proper care of the body.
Hyposulphite of soda (hi'p6-sm"flt) :
a chemical used in photography.
Igneous (Ig'ne"-#s) : rocks which have
been melted by intense heat, that
is, by volcanic action.
Immune (I-mun') : free from or pro-
tected against any particular dis-
ease.
Incident (m'sl-d&it) : falling upon
a surface.
Infectious (In-feVshus) : catching ;
communicable ; a germ disease.
Inhale (In-hal') : to breathe in.
Inspiration (In'spf-ra'shftn) : the act
of breathing in.
Insulate (In'su-lat) : to separate one
body from another by a material
that does not allow heat or elec-
tricity to pass through it.
Insulator (In'su-la'ter) : a body
through which an electric current
passes only slightly or not at all.
Jonquil (j6n'kwll) : a garden plant.
Kaleidoscope (kd-ll'do-skop) : a de-
vice to show symmetrical designs
by use of two mirrors.
Larva (lar'vd) : the immature worm-
like stage of insect development.
Lava (la'vd) : fluid rock from a vol-
cano or such rock hardened.
Legume (ISg'um) : a plant, such as
the pea or bean, bearing pods.
Lever (le'ver) : a bar capable of
turning about one point.
Ligament (Hg'd-mgnt) : a tough
band of tissue.
Luminous (lu'ml-n#s) : giving out
light.
Magnesium (mag-ne'zhl-tim) : a sil-
ver-white metal.
Magnet (mag'ne't) : a piece of iron
or steel which attracts iron or
steel.
Magnetism (mag'ne't-Iz'm) : having
the property of being magnetic, of
having attraction.
Mammal (mam'al) : all animals that
nourish their young with milk.
Matter: anything that occupies
space and has weight.
Membrane (mgm'bran) : a thin pli-
able animal or vegetable tissue.
Metamorphic rock (mgt'd-mor'flk) :
rock changed by heat, pressure, or
movement.
Micro^rgamsm(mI'kr6-6r'g#n-Iz'm):
any organism of microscopic size.
Molecule (mSl'e-kul) : smallest part
of a substance that can exist alone.
Mollusk (m5l'#sk) : an unsegrnented
soft-bodied animal, sometimes
bearing a shell.
Mulch (mulch) : a loose covering.
Muscle (mtis"l) : a mass of tissue
whose function is the production
of motion.
420
GLOSSARY OF IMPORTANT TERMS
Myriad (mfr1-#d): an indefinite
large number.
Narcotic (nar-k6t'Ik) : a drug which
in great doses produces stupor.
Neutralize (nu'trdl-lz) : to counter-
act.
Nucleus (nu'kle"-#s) : a central mass.
Nutrient (nu'trf-ent) : substances
which furnish food to the body.
Opaque (6-pak'): not permitting
light to pass through.
Organic (6r-gan'Ik) : pertaining to
living plants and animals.
Oxidation (6k'st-da'shwn) : act of
combining with oxygen.
Oxidize (6k'sl-diz) : to add oxygen.
Parallel (par'a-lel) : lying evenly
everywhere in the same direction.
Pasteurization (pas'ter-I-za'shwn) : a
Ccess for checking growth of
teria in fluids by heating.
Perpendicular (pur'pen-dlk'u-ldr) : in
the line of gravity or at right
angles to a surface.
Perspiration (pur'spf-ra'srmn) : fluid
excreted by sweat glands.
Phenomenon (fe-n6m'e-n6n) (pi.
phenomena) : a happening or
event.
Phosphorus (f6s'f<5r-#s) : a chemical
element which burns at a low
temperature.
Physiology (fiz'I-Sl'6-jI) : the study
of the structures of the body and
how they work.
Piccard (pe"'kar'): Belgian scientist
who made the first trip into the
stratosphere in a closed gondola.
Pistil (pls'tll) : the central structure
of a flower, which contains the
ovary.
Pituitary (pi-tu'I-ta-rf) : a ductless
gland.
Pneumonia (nu-mo'nl-d) : a disease
characterized by inflammation of
the lungs.
Pollen (pSl'Sn) : fine dust grains
from the anthers of flowers.
Pollination (p61'I-na'sh#n) : the
transfer of pollen of one flower to
the stigma of another.
Prism (prlz'm) : a body with
similar ends and rectangular faces.
Propaganda (prbp'd-gan'dd) : an
organization for spreading a par-
ticular system of principles.
Protein (pro'te"-m) : food material
containing carbon, hydrogen, oxy-
gen, and nitrogen. Foods con-
taining proteins are meat and
Proton (pro'tSn) : the part (nucleus)
of the atom that has a positive
electric charge.
Quantum (kw6n't#m) :
quantity.
a certain
Radiant (ra'dl-ant) : given out or
emitted by rays.
Radiation (ra'dl-a'shwn) : the trans-
fer of energy across space, as heat
and light from the sun.
Reflection (re'-fle'k'slmn) : turning or
bending back.
Refraction (re-frak'sMn) : bending
of a ray going obliquely from one
medium into another in which the
velocity is different.
Refrigeration (rg-frlj'er-a'shwn) : a
process of cooling.
Refrigerator (re"-frij'er-a-ter) : a box
or room for keeping things cool.
Respiration (reVpI-ra'sh&n) : act of
breathing.
Retina (reVi-nd) : the membrane of
the eye which receives the image.
Rigel (rl'jel) : a first magnitude star
in the constellation Orion.
Rotate (ro'tat) : to turn.
Secretion (se-kre'shwn) : material
separated and discharged by cells.
Sedimentary rocks (se'd'I-meVtd-rf) :
rocks formed from deposits made
under water.
Soluble (sol'u-bT) : to dissolve.
Solution (so-lu'sh&n) : a liquid in
which a solid or a gas has dis-
solved.
Solvent (s6l'vent) : having power of
dissolving.
Spectroscope (spSk'tro-skSp) : an
instrument for forming spectra.
Sperm (spurm) : male reproductive
cell.
Spherical (sfSr'I-kal) : globular in
form.
Stalactite (std-lak'tit) : a formation
of calcium carbonate, resembling
an icicle.
GLOSSARY OP IMPORTANT TERMS
421
Stamen (sta'mgn) : the part of a
flower which contains the pollen.
Sterilized (ster'Mizd) : freed from
disease bacteria.
Stimulus (stlm'u-lws) : an agent
capable of producing an impression
on a sensory organ.
Stoma (sto'md) (pi. sto'mci-td) :
mouthlike opening in epidermis
of green leaf.
Stratified (strat'I-fld) : arranged in
layers.
Sulphuric (sul-fu'rlk) : acid com-
posed of hydrogen, sulphur, and
oxygen.
Tomcelli (t6r're-cheTle) : an Italian
physicist who devised the method
of measuring atmospheric pressure
in 1643.
Tourniquet (toor'nl-kgt) : a device
for arresting bleeding.
Translucent (trans-lu's£nt) : allow-
ing some light to pass through, but
not enough to permit objects
to be clearly seen through the sub-
stance.
Transmit (trans-mTt') : to pass on.
Transparent (trans-par'£nt) : allows
light to pass through easily.
Tuberculosis (tu-bur'ku-lo'sls) : an
infectious disease of the lungs.
Vacuum (vak'u-#m) : a space from
which all air or other matter is
removed.
Vaporization (va'per-I-za'sh&n) : act
of changing from liquid to a gas.
Vaporize (va'per-iz) : to change to a
vapor.
Vegetation (vSj'e"-ta'slmn) : any sort
of plant life.
Veins (vanz) : tubes carrying blood
back to the heart.
Vitamin (vl'td-mm) : regulative food
substance necessary to life.
Weathering (w6th'er-ing) : the proc-
ess of breaking up and changing
rock to soil.
INDEX
INDEX
Bold-face numbers refer to illustrations.
Accidents, auto 399, 400, 401, 402
classification of 400
broken bones 405
prevention of 402
to pedestrians 401
what to do in case of . . 402-407
Adaptations, acts 35
cactus 30, 31
for seed dispersal . . . 31-32
for food getting .... 27, 267
green plant 30-31
how we make them ... 38
in birds 28-30, 34
in fishes 36
in man 33-35
what they are .... 26-27
Air, a mixture 47
exerts pressure .... 52, 53
occupies space 45
pump 62
supply 67, 68
uses of 50, 51, 59-66
Alcohol, effects of . . 388, 397, 398
food value 316
harm done by 397
Amphibia 275
Animals, adaptation for food
getting .... 266, 267, 268
business of life .... 266-269
carnivorous 267
food eaten by 266
harmful to gardens . . . 274
herbivorous 267
on home grounds .... 273
like machines 267
reproduction 268-269
Anthers 263
Arches, fallen 372-373
how kept in good condition
372-373
Arcturus 192, 203
Aristotle 2
Arteries 382
Artificial respiration, prone-
pressure method . . . 403-404
Athletics, overstrain in ... 391
Atlantosaurus 224
Atomizer 61-62
Atmosphere, exerts pressure . 46
holds things together . 56, 57, 58
tapers off 46
Atmospheric pressure . . 55-56
Auto and human machine . 354-358
Audubon 278
Bacteria 333-341, 337
colonies of 337
forms of 337
how we grow 337
living things 336
Barnacles 296
Bath, Roman 88
Baths, uses of 366-367
Beebe, William 29
Beetles 274
Betelgeuse 203
Bird bath 280
Birds 277-280
attraction of 280
on home grounds .... 279
protection of 279
relation to forest .... 291
useful 277
Bleeding, arterial 406
first aid 406
from veins 406
Bones and ligaments .... 370
and muscles 369
and tendons 370
as levers 368
broken, first aid .... 405
fractured 369,370
in foot 372
Body control, how influenced 387-388
Boils, cause of 363
Bomb calorimeter 330
Brashear, computations . . . 191
Breathe, how we ... 69-71, 70
Brontosaurus 224
Bugs 276
Burns, first aid 407
Butterflies 274
Calcium in body , . . 322, 323
Calorie . 329,330
requirements of body . . 329-331
requirements of man . . 329-331
Calyx 263
Cambium 292
Camera 143, 144
first picture made with . . 143
resembles the eye .... 149
425
426
INDEX
Camera (Continued)
shutter 144
what makes some expensive 145
Candy, as a food .... 316-317
Capillaries 383
Capillarity 238
Cartilage, where joined . . . 371
uses of 371
Caterpillars 274
Cassiopea 203
Catbird 279
Cavendish 82
Cells .... 353, 354, 356-357
body built of . . . .353,354
electric 178,179
free living 357
how food gets to .... 381
from tissues 357
of onion 254
of nervous system .... 385
release energy 354
Century of Progress . . . . 192
Changes, chemical and physical 15
Chaparral 289
Characteristics of living things
252-257
Cheerfulness, as a habit . . . 390
Chemical change 15
Cigarette smoke, effects on fish 393
Clam, salt water 295
Clothing, and body heat . . 117
extremes in 118
for summer 120
for winter 120
materials used for . . . . 117
Collecting trip, outfit for . . 282
preparation for 281
shore 294
Color blindness 156
Color, what it is 154
Colored objects 155
Colors of stars 193
Compass, how to make a . . 168
how to use 168
value of 171
Compounds 14
Condensation 84
Conduction 110
Constellations 202, 203
named by Greeks . . .201, 202
Conductors 177
Conifer 271
Control 337
nervous 386
Convection 109
currents 109
Copernicus 188, 189
Corolla 263
Corpuscles, colorless .... 381
red 381
Cosmetics, use of 363
Crabs 296
Crickets 274
Cross pollination 263
Crustaceans 276
crayfish 286
Current electricity . . . . 178
Daguerre . 143
Dairy, a model barn .... 340
Day, a 7th grader's .... 390
Decay, cause of 334
Deciduous trees . . 270, 271, 272
Dermis 361
Desert, before and after rain 80, 81
Digestion, demonstration to
show 377
organs of 378
work of enzymes . . . 378-379
Dipper, Big . . . . 201, 202, 203
Little 201, 202, 203
Distances to stars 191
Downing 287
Dry ice 343-344
temperature of 344
uses of 344
Drowning, first aid .... 403
Earth, age of 222
movements of .... 196-198
Earthworm 276
Egg 263-264
Electric cells 178-179
Electric energy, produced
chemically 179
shock, first aid 404
Electrified bodies, properties
of 175-176
Electricity, current ... 178
ways of producing . . . 173-179
Elements 14
Elfin forest 289
Elm 271,272
Emetic 407
Emulsion 91
Enzymes 378-379
Endocrine glands 387
Energy 14
from fuel 352
English sparrows 280
Environment
differences in . . . . 17-18
factors of 1 1 , 12
life depends on 255
use of 16
INDEX
427
Environments, adaptations for
different 251
Erosion 230-235
by glaciers 233
by solution 232
by water 231
by wind 230,231
use of knowledge on ... 234
Evergreens 271, 272
expiration 71
Eye, and light intensities . 150-151
defects 151
like a camera .... 149, 150
Eyes, care of 152-153
Fainting, first aid 404
Farming, dry 240
Fatigue, dangers from . .391, 393
experiment to measure . . 388
poisons 388, 393
Fatalities, causes of .... 401
Feather, structure of .... 29
Feet, flat 372, 373
Feldspar 319
Fermentation, by yeasts . . 335
Fertilization 263,264
Fibers, cotton 119
flax 119
linen 119
silk 119
wool .119
Field trip 252,300
Finger prints 360
Fire, cause of 106
making a 104
worshipers 103
First aid 402-407
Fish, how they live .... 283
Fishing 288
Flame 49
Flatworms 297
Flower, fruit from . 260, 262, 264
parts of 262, 263
work of 263
Food 375-382
chewing 379
eaten by animals .... 266
how does it get to the cells
381-382
how prepared for digestion . 379
how transported in body 375-377
made by green plants . . 261, 311
tables 328-329
values 327-330
water as a 321
Foods, body building . . . 312
how absorbed ., 379
bulky 320
energy producing . 308, 315-317
fuel .... 308, 309, 312, 315
growth 312
how to keep from spoiling . 339
in different countries . . . 307
kinds of 312
measuring energy of . . 329, 330
minerals in 322, 323
protective 308, 312, 317-320, 319
regulative . . 308, 317-320, 319
what cooking does to ... 339
where do they come from 309-311
why do they spoil . . . 333-338
Food cycle 258
Forests 290-293
and wild life 288
animals in 291
insects harmful to .... 292
mixed 290
support life 291
trees of 290, 291
yellow pine 291
Fossil fern 220
fish 221
tree 222
Fossils, age of 222
what are 220-221
Franklin 166, 177
Frogs 283
life history of 284
eggs of 283
Fruits, as foods . . 310, 320, 321
formation of ... 260, 262, 264
Fuel value of food .... 332
Fuels, supply energy .... 352
Galaxy 206
Galen 2
Galileo 53,54,55
Galvani 174,166
Geysers 232-233
Glands of control 387
Granite 218,219
Grasshoppers 274
Green leaves, as food factories 261
Green plants, food making by
parts of '259
Green vegetables, importance
of 315
Greeks, as astronomers . .201, 202
Growing trees exert force . . 229
Habits, formation of 7, 366, 390, 397
Hair, care of 361-362
shampooing 362
428
INDEX
Hairs, how they grow . . . 361
structure 361
Heat, and humidity .... 365
causes changes of matter . 112
causes expansion . . . . Ill
loss from body .... 364, 365
unit of 327, 330
Heart, a double force pump . 382
work of .... 377,382,383
Hemlock 271
Hippocrates 2
Home medicine chest . . . 407
Hot springs 232
Human body, a machine . 354-355
an engine 353
Human body and engine com-
pared . 309, 351, 354, 353, 355
building materials . . . 356-357
Human machine, an organism 358
and training ...... 389
differences between it and
auto 354-355
Humus 214
Hunter, John 1, 2
Indians, keen observers
used smoke signals
Insect, diagram of
Inspiration ....
Insulators ....
Intestine, large .
small
Iodine, test for starch
uses of, in body . .
Iron in body . . .
3
130
274
71
177
378
378
311
322
323
LaBreaPits 223,225
Larvae, dragon fly .... 286
mosquito 286
Lava, flow 216
Lavoisier 44
Leaves, functions of .... 261
where placed 260
Levers, bony 355
Laboratory 336
Lichens 3
Life, a series of changes ... 16
comes from life 253
depends on environment . . 255
in pond 282
in tidal pools .... 297, 300
in sand or mud 296
on earth changing . . . 224, 226
on the rocks 296-297
origin of 252-253
tree of 298-299
Life zones, in mountains . . 290
in pond 282
intertidal 295
shore 294, 295
Ligaments 370
Light, absorbed 134
diffused 139-140
how we use 129, 152
law of reflection . . .136, 137
properties of 134
reflected 134
refraction of 140, 141
transmitted 134
Lightning 177
Limestone 237
Living stuff, analysis of . .317, 322
Living things, are responsive 254, 255
are sensitive . . . 249, 250, 255
grow 253
made of cells 254
Magdeburg experiment ... 57
Magnet, the earth a . 165, 171, 172
Magnets, how named . . . 165
how to make 167
permanent 167-168
properties of 167-173
what will they attract . . 167
Magnetic boat 184
field 170, 171
Magnetic poles 169-179
law of 170
Man, an efficient machine . . 327
and his environment ... 37
Maple 271
Maps, star . . 201,202,204,205
Matter, nature of 13
Mica 218
Microorganisms 335
Milk, a perfect food . . . 324, 325
and bacteria 340-342
Milky Way 206
Millipeds 276
Minerals, in body .... 322, 323
hardness 219
Mirrors, curved .... 138, 139
how we see in 137
Mold spores 334
Molds 336
Mollusks 274
Mussels, fresh water .... 285
Moths 274
Mosquito larvae 286
Mountains, life zones . . 289, 290
old 234
young 235
Mulches 240
dust 240
paper 240
INDEX
429
Muscles, and bones . . . 370-371
how they do work .... 376
Narcotics 394-398
Nails, care of 362
Negative, printing from . . . 147
making a 146, 147
Nervous control 386
Nervous system, care of . 389-391
fair play to 389
Nesting boxes 279
Nests, birds 277
sunfish 283
Newton, Sir Isaac 128
Nicotine 394
North Star . . . .198, 200, 201
Nucleus 356
Nutrient solution for plants . 241
Oak 271,272
Observatory, Mount Wilson . 189
Oil glands 361
Opaque 135
Optical illusions 4
Organism 358
Organs 357, 358
Ovary 264
Oxidation 49
Oxygen, helps burning . . 48, 49
useful and harmful ... 48
Pasteur, Louis 253, 341
Pasteurization 341
Pebbles 215
Petals 262, 263
Petri dishes 336, 337
Phosphorus in body . . . 322, 323
Photoelectric cell 192
Photography in astronomy . 190
Photographs, how made . 142-147
Physical change 15
Pigments, mixing 156
Pill bug 276
Pimples, cause of 363
Pine 271
Pistil 262,263,264
Pinhole image, how made . 130, 131
Plankton 295
Plants, elements used by . . 242
how fitted for work . . . 258
mineral substances needed
for 241
Poisons, how to treat . . . 407
Polaris . . 199, 200, 201, 202, 203
Porcupine 27
Positive, making a .... 147
Posture, examples of .... 371
related to shoes 373
how to get good .... 372
value of good .... 371, 372
Pressure cooker 115
Priestley 44
Prism, use of 164
Problem solving 5
and the scientist .... 6
in tennis 6
Proteins 312, 317, 331
proportion in diet . . . 331-332
Quartz 219
Radiation 110
Rats, experiments with . . 307-308
Recreations depending upon
water 94, 95
Refrigeration, electric . . . 343
iceless 344
Refrigerator, construction of . 342
use of . . ' 342
Rest and health 391
Rigel 203
Rocks, from soil 219
how formed 214
igneous 216
metamorphic 217
sedimentary 217
Rocks and minerals . . . 217-218
differences 218-219
Roots, function of ... 259, 261
Root hair 261
Rotation of earth .... 196-197
Rusting, causes of .... 47-48
Safety education, why impor-
tant 399, 400
Salt 218
Salts, relation to life .... 294
Sea anemones 296, 300
Sea urchin 296, 297
Seaweeds 296,297,300
Seasonal differences in food re-
quirements 330
Self-testing exercise, use of . . 9
Sense impressions 4, 5
Sensory cells 386
Seeds, how formed .... 260
how scattered 264
Sepals 262,263
Shadow 136
Shoes, comfortable . . . 373-374
Shore, life on 295
life zones 294
Signal lights, colored . . . 132
Siphon of clam 296, 296
430
INDEX
Sirius 203
Skeleton, and muscles . . . 368
human 369
Skin, a protective covering 359-360
care of 362-384,363
dermis 361
epidermis 361
need for cleanliness . . 366-367
oil glands 361
regulates body temperature 364
use of cosmetics . . . 363-364
uses 359-365
sweat glands 360
Sleep, value of 389
Slugs 274
Smoking, effects of ... 395, 396
Snails 274
Soap, value of 91
Soil, acid 242-243
alkaline 242
differences in .... 236-237
effect of cultivatioh on . 239-240
how formed 228-235
kinds of 237
water in 237, 238
water film in 238
Solution of limestone . . 230, 231
Sow bug 276
Spectroscope 194
Sperm nucleus 263-264
Spider 276
Spoiling of foods 333
Sprinters 385
Spruce 271
Stamens 262, 263
Star colors 193
magnitudes 193
maps . . . 201,202,204,205
Stars, why do they rise and set
198-199
Starfish 297,299
Sterilization, value of ... 340
Stigma 262,264
Stimuli, responses to .... 250
what are they 256
Stomata 261
Story test, use of 10
Stratosphere flight . . . 44,46
Stream, mountain 214
Suffocation, first aid .... 404
Sulphur 218
Sunfish nest 382
Sunstroke, first aid .... 404
Superstitions, common ... 8, 9
Survey of yard 270
Sweat glands, structure . . . 360
use of 360
Table giving ages of fossils . . 225
Tables, food values . . . 328-329
Teeth, care of 379, 381
Temperature, and microorgan-
isms 339
freezing and boiling . . . 113
how measured 112
kindling 105, 106
of stars 194
Tests, carbon dioxide ... 50
for fibers 118-119
Thermometers 1 12, 113
Thermos bottle 344
Tidal pools 297
Tinder box, use of ... 107-108
Tire pump 63
Tissues, examples .... 357-358
Toad 275
eggs of 283
Tobacco, cause of injury . . 396
Torricelli "... 55
Traffic squads 402
Training, and the human ma-
chine 389
Translucent 135
Transparent 135
Tree, growth of 292
Tree of life 298,299
Trees, rings of growth . . . 292
Turtles 283, 284, 285
Uncas 3,5,389
Underclothes, porous best . . 365
uses of 365-366
weave of 365
Unconscious activities . . 386, 387
Vacuum, how made .... 61
uses of . . . . 61, 62, 63, 64, 65
Vaporization 84
Varied diet, importance of . 314-315
necessity for 331
Veins 383
Vitamins 318, 319, 320
Volta . 166
Water, a regulative food
a solvent
amount in living things
boiling of
composition of ...
cycle
distillation ....
electrolysis of ...
life in . . ...
pure . . .
purification of
. 321
89,90
. 92
. 114
. 82
85,86
. 84
82-83
94-96
83-84
84
INDEX
431
recreations depending upon 94, 95
safe and unsafe 92
sun drawing 86
used in cooking 93
uses of 88-95
Weathering 228
chemical 229
mechanical 228, 229
Wells, safe and unsafe
Woodpecker
Wool for underclothes
Workbook, use of . .
279
366
9
Yardstick, astronomers . . 190, 191
Young, rearing of 269
Yeasts 333-336
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