By BERNICE KOHN

stratcd hy I RNfSI

THESCIENTIFIC

METHOD

THESCIENTIFICMETHODby Bernice Kohnillustrated by Ernest Crichlow

Prentice-Hall, Inc., Englewood Cliffs, N.J

this book is for Raymond Sacks

other P-H books by Bernice Kohn:Our Tiny Servants: Molds and Yeasts

Computers at Your Service

Everything Has a Size

Everything Has a Shape

The Peaceful AtomMarvelous Mammals: Monotremes and Marsupials

The Scientific Method by Bernice Kohn

©1964 by Bemice KohnAll rights reserved, including the right to reproduce this

book, or any portions thereof, in any form except for the

inclusion of brief quotations in a review. Library of

Congress Catalog Card Number: 64-13256 Printed in

the United States of America

J-79606

Prentice-Hall International, Inc., London • Prentice-Hall of Aus-

tralia, Pty., Ltd., Sydney • Prentice-Hall of Canada, Ltd., Toronto •

Prentice-Hall of India (Private) Ltd., New Delhi • Prentice-Hall of

Japan, Inc., Tokyo • Prentice-Hall de Mexico, S.A., Mexico City

C641810

Contents

1 You've Done It! 8

2 The Method 12

3 Experimental Science Begins 20

4 The Circulation of Blood 26

5 Little Beasties 32

6 A Key, a Kite and the Method 38

7 Darwin and Evolution 44

8 The Wizard of Menlo Park 52

9 Miracle Medicines 58

10 Old Method, New World 64

Index 71

:#'^... /

I

?Il^

J

1

You've

done it!

What makes a scientist a scientist? How do scientists

discover things? Is it luck? Is it accident? Partly both,

perhaps. Then why doesn't just anyone make great sci-

entific discoveries?

The answer is that a scientist has a certain way of

finding out things. Another word for way is method, and

the scientist's way of solving a problem is called the sci-

entific method.

The use of the scientific method is the first step in the

training of a scientist but you don't have to be a scientist

to use it. In fact, it's very possible that you might have

used the scientific method without even knowing it. It

could have happened like this:

One day, walking home from school, you might have

heard a faint whimper from behind a bush. On investi-

gating, you found a tiny puppy, cold and shivering. Be-

cause he looked lonely and miserable, you picked him

up and took him home.

He stopped shivering in the cozy bed that you made

for him—but he still whined. You guessed that he was

hungry. But what does a small puppy eat? You didn't

know, so you had to find out. You called everyone you

8

knew who had a dog to ask what puppies eat. Each one

told you something different. One said hamburger, one

said milk—and your best friend suggested cereal!

You decided that one of them was probably right.

You would have to find out which one.

You located some hamburger in the refrigerator and

put it down in front of the dog. He didn't eat it. You

poured some milk into a saucer—but the puppy didn't

drink it. You tried to feed him cereal from a spoon, but

he turned his head away. And all the time he cried.

You decided that he must be hungry, so if he wouldn't

eat, it was because he couldn't. Perhaps he was still too

young to eat by himself. Maybe he needed to be fed from

a nursing bottle. You ran next door and borrowed a baby

bottle from your neighbor.

You filled the bottle with milk and put the nipple into

the puppy's mouth. He began to suck it right away. You

held the bottle for him and in a few minutes his little

belly was full and round, and the puppy fell asleep.

Does all of this have anything to do with the scientific

method? It certainly does. You followed it! And manyearly scientists followed the method exactly as you did,

without ever having heard of it! The scientific method is

simply the sensible way to go about solving a problem.

It can be explained in five steps. Let's see what they are.

9

If>»l/ 1

2Themethod

Before a scientist can begin to solve a problem, he

has to know exactly what the problem is. Sound simple?

Well, it isn't always—but in the case of the hungry puppy

it was. The problem was how to feed him.

The first thing you did was to gather all the informa-

tion you possibly could. You noticed that the puppy was

still unhappy even though he was warm. You got infor-

mation on feeding puppies from your friends. If you had

had the time, you probably would have gone to the

library to look for a book on puppy care. Or, you might

have taken the puppy to a veterinarian for advice. All of

this adds up to the first step in the scientific method. It

is observation—coWecting all the facts you possibly can.

You thought over the facts and decided that one of

them was probably correct. This is the second step in

the scientific method and it is called the hypothesis. That

means a guess based on the facts you have gathered

so far.

The third step is to test the guess ( or guesses ) to see

what happens. This part of the scientific method is called

experiment. You made three experiments when you fed

12

the puppy hamburger, milk from a saucer, and cereal.

None of the experiments worked—so you took the

fourth step. You developed a theory. A theory is a guess

based on the results of the experimentation.

The fifth and last step in the scientific method is the

proof of the theory. A good scientist makes use of all of

his scientific knowledge to prove a theory. Sometimes he

finds out that his theory is wrong and then he has to

start all over again. Your theory was proven quickly. The

puppy drank the milk from a bottle and was satisfied, so

you knew that you had found the right way to feed him

—you had solved the problem.

And that's all there is to the scientific method. Let's

list the steps in order, so that they are perfectly clear.

1. Observation: collecting as many facts as pos-

sible.

2. Hypothesis: making a guess based on the

facts.

3. Experiment: testing the hypothesis.

4. Theory: the hypothesis which seems to be

correct after experiment.

5. Proof: the ability of the theory to stand up

under any test which anyone at all can

think up.

13

Not every scientist follows all five steps exactly, every

time. Very often, one man carries on the unfinished work

of another. He may read about someone else's observa-

tion and develop a new hypothesis on which he will con-

duct his own experiments. Or, he may hear of someone

else's experiment and form his own theory from the re-

sult—and prove it. This sometimes happens within days,

sometimes not for many generations.

Just knowing the five steps of the scientific method

isn't the whole story. You also have to know how to think.

Scientists have lots of imagination—and they use it.

Many of the great discoveries of all time were made

by "accident"—only it wasn't really accident. The scien-

tist thought and imagined. When the accident came

along, he noticed it and recognized its possible impor-

tance. At some point along the line, he probably made

what is called an educated guess. The educated guess is

a guess, true enough, but it has a large amount of edu-

cation behind it. The scientist has studied, read, noticed,

and thought. In other words, he has observed. His

"guess" is just a hypothesis with perhaps a little more

than the usual amount of imagination thrown in.

The earliest craftsmen were men of imagination but

not of science. Invention and discovery began in the

days before history. When man learned to use fire, he

14

made a great discovery. When he fashioned the first

spear from stone, he invented a weapon. These men de-

veloped skills but we do not think of them as scientists.

The first glimmerings of what we would call science

began about six thousand years ago in Egypt and Meso-

potamia. Men observed the heavens and learned a great

deal about astronomy. They noted the constellations and

made a calender based on the stars. These people were

limited in their discoveries because they did not experi-

ment. However, they did record what they learned so

that the work could be carried on by others.

The Egyptians also made some fine inventions, includ-

ing the sundial and a water clock. But progress was very

slow. Three thousand years were to pass before a me-

chanical clock was invented!

Many discoveries were also made in early China,

India, Persia and elsewhere. But by 500 B.C., Greece had

become the center of progress. The Greeks were great

thinkers. They accomplished much with reason and

logic. They were also good observers.

The Greeks learned many things about the universe,

about medicine, and about mathematics. They madesome great discoveries—and some great mistakes! Someof the mistakes were so convincing that hundreds of

years passed by before anyone found out about them.

15

The Greeks fell down as scientists because in spite

of their careful observation and thinking, they didn't

experiment.

No one thought much about experiment at all until a

book was written by an English philosopher. His name

was Francis Bacon and he lived from 1561 to 1626.

Bacon believed that knowledge comes from experience

—and that the best way to gain experience is through ex-

periment. He is called the father of the scientific method.

Bacon completely abandoned the pure logic of Aris-

totle and the other Greeks. He stressed, instead, the im-

portance of experiment. He also made a point of the

necessity of exploring any evidence that did not seem

to agree with the theory being tested. This, of course,

is an important part of the proof. In practicing the last

step of the scientific method, every scientist tries as hard

as he can to disprove his theory. Only when he has failed

completely does he know for a fact that the theory was

correct.

The publication of Bacon's method started the era of

modern science. Gone were the guesses based only on

what men thought to be true. From Bacon's day on, ideas

would be based on what men had actually found out to

be true.

16

During the three hundred and fifty years since Bacon

lived, there have been more marvelous discoveries and

inventions than there were in all the thousands of years

before. Let's look at some of the wonderful things that

happened—the brilliant results of scientific thinking.

17

GALILEO %

<

# ,,^^^^-.

^^^ntm>:r>

Wt

J^

^

3 •

Experimental

science beginsfc

^/

M^tt mgmmimtMik LIA.

The change from the old methods to the scientific

method was not a sudden one. There were a few experi-

menters even before Bacon's time.

Leonardo da Vinci, an ItaHan who lived from 1452 to

1519, was notable. He was a great artist and engineer

and performed many experiments with valuable results.

As early as the 1580's, a Belgian, Simon Stevin, began

to think about the speed with which things fall. The

great Greek, Aristotle, had said that bodies fall with a

speed that is in proportion to their weight. That is, a

ten-pound stone would fall ten times as fast as a one-

pound stone. The entire civilized world had accepted

this idea for centuries. But not Stevin. He climbed to

the top of a thirty foot tower and took with him two

leaden balls, one ten times heavier than the other. Hedropped them both at the same time onto a board on

the ground and proved that the two weights hit at the

same time because only one sound was heard!

This experiment should have put an end to Aristotle's

theory—but it didn't. For one thing, the results of Stevin's

experiment were published in Dutch and very few peo-

20

pie outside of Holland knew the language. And for an-

other thing, people just didn't like to give up an idea

that they had had for so long.

But other men in other countries continued to chal-

lenge the old ideas. According to the ancient astrono-

mers, such as Aristotle, and the Egyptian, Ptolemy, the

earth was the center of the known universe and the sun

moved around it. In 1543, a Polish priest, Nicolas Coper-

nicus, published a new idea. Copernicus said that the

sun was the center of the universe and that the earth

and other planets moved around it. He also noted that

the moon rotated around the earth. Almost no one be-

lieved him.

But little by little, as men began to go beyond the

first step and reinforced their observations with experi-

ments, they started to find out how things really worked.

One of the first of the great experimental scientists

was Galileo Galilei. He was born in Pisa, Italy, in 1564

and died in 1642. Galileo devoted his life to exposing

the errors of the ancient philosophers. His work was

based on hard facts.

When there was no equipment for his experiments,

Galileo himself built what he needed. One of the things

he was eager to prove was Copernicus' theory of the uni-

verse, which he felt sure was correct. When he heard

21

about a Dutchman who had ground lenses to make

things look larger, Galileo promptly went to work and

made himself a telescope. He was probably the first man

in the world to see the moon as anything more than a

make-believe face on a disk of light.

The Greeks, by observation, had said that the moon

was perfectly smooth. But Galileo, experimenting with

his telescope, saw that the moon was covered with hills

and valleys. He decided that it must be another planet,

like the earth.

Galileo's telescope soon revealed other wonders. He

saw four moons circling around Jupiter and he saw spots

on the face of the sun. He also found that Venus

changed, like the moon, from a crescent to a full circle,

and that the Milky Way was made up of a host of stars.

As a result of his observations and experiments, Gali-

leo established that the sun was indeed the center of the

so-called universe.

Galileo also taught the world much about gravity and

falling bodies. He had probably never heard of Stevin's

experiment, but Galileo had the same idea and con-

ducted his own experiment to prove it.

There were no skyscrapers in those days, and Galileo

felt that the highest building he could find wouldn't be

high enough to really prove anything. But, he reasoned,

22

J

a slope is just the same as a height except that it is spread

out. For the purpose of an experiment it would be per-

fect because the objects would roll down slowly and

could be accurately timed.

And so Galileo took a beam twenty-two feet long and

made a smoothly polished groove in it. He ran brass

balls down the groove, timing each run with an Egyptian

water clock. As a result of his experiments, theory, and

proof, Galileo finally showed the world that Aristotle

was wrong about the speed of falling bodies. In fact, he

proved that all freely falling bodies, no matter what their

weight, fell the same distance in the same amount of

time.

By the careful use of the scientific method, Galileo

also found out much more about motion, gravity, pen-

dulums, sun spots, and the phases of the moon. He also

invented the thermometer.

Galileo's teachings were in conflict with the teachings

of the church in those days, and in 1633 he was put on

trial and condemned as a heretic. In order to save his

Hfe he was forced to say that his discoveries were false.

There is a popular story, and it may well be true, to

the effect that right after his "confession" that the earth

stood still, Galileo was heard to murmur under his

breath: "And yet it does move."

23

§m¥

./>

^;

^<=^

IkFROMBODY

TO BODY

TO LUNGS

//>

FROMLUNGS

mwi

THE HEART

la iH-

^\v

WILLIAMHARVEY

4Thecirculation

of blood

The story of the discovery how blood circulates

stretches over hundreds of years. Many men came close

to the truth—and yet failed to reach it. Some investi-

gators observed, some even experimented—but it wasn't

until the scientific method was followed completely that

the facts were known.

One of the great medical writers of ancient times was

Galen, a Greek who lived from 129 to 199 a.d. He wrote

131 books and articles—and 83 of them are still in ex-

istence!

Galen was very much interested in the heart and the

flow of blood. Unlike other Greeks of his time, he did a

few experiments, but only with animals, never with

humans.

Galen knew that the blood from the veins entered the

right chamber of the heart, and that the blood from the

left chamber entered the arteries. But he also knew that

the chambers of the heart are separated by a wall called

the septum. Therefore, Galen concluded that a little

blood must leak through the septum. That was his theory

—but he never tried to prove it.

26

Later writers studying Galen's work decided that the

blood swished back and forth. Some of them believed

that there were two different kinds of blood—one kind in

the veins and another in the arteries.

In the middle of the sixteenth century, a Fleming,

Andreas Vesalius, pointed out that the septum of the

heart was thick and tough, and that blood could not pos-

sibly pass through it. No one paid any attention to him.

At around the same period, Michael Servetus, a

Spaniard who worked in France and Switzerland, came

up with the idea that blood did not move back and forth

at all. Servetus decided that it moved in a circle from

the right to the left chambers of the heart, through the

lungs. Aristotle had said that only heavenly matter

could move in a circle. Everything else had a beginning

and an end. In presenting his arguments against Aris-

totle's ideas, Servetus unfortunately had a great deal to

say about religious matters. In 1553, he was condemned

as a heretic and burned at the stake. His writings were

burned with him.

There were other investigators, too, but they made

mistakes—and after what had happened to Servetus,

they were afraid to say too much. It wasn't until the sev-

enteenth century, in England, that the truth was found

and safely spoken.

27

William Harvey was born in the English town of

Folkestone in 1578. He wanted to be a doctor, so in

1597 he went to study at the University of Padua, the

finest medical school of the day.

One of the great teachers at the University was

Hieronymus Fabricius. This man had discovered what

he called "little doors" in the heart—but he didn't know

what they were for. Fabricius believed and taught

Galen's idea, that the blood oozed through the septum

and then washed back and forth.

It was a thrilling day for Harvey when he saw the

famous Fabricius dissect a human corpse and display

its heart. The thought that he would one day tell the

world that the great man was wrong probably never

crossed Harvey's mind—but that was exactly what was

to happen.

The more Harvey thought about Fabricius' "little

doors" (or valves) in the heart, the more puzzled he

became. What was their purpose?

He had observed the valves and now he had a hy-

pothesis. He wrote, "I began to think whether there

might not be a motion as it were in a circle."

Was there anything to the hypothesis? Harvey set up

an elaborate system of experiments and proofs. He was

the first of the blood investigators to actually weigh and

28

measure blood. He didn t jump to any conclusions—he

found out and proved every one. In short, he followed

the scientific method.

Harvey showed that blood moved in only one direc-

tion in the veins. The valves or "little doors" now had a

clear purpose. They were one-way openings. The blood

could not flow back and forth in the veins—it had to go

around.

In 1628, William Harvey published his famous book

called in Latin, Exercitatio Anatomica de Motu Cordis

et Sanguinis. In English, that means "An Exercise in

Anatomy on the Movements of the Heart and Blood in

Animals." In the book, Harvey clearly proved that blood

is pumped from one side of the heart, through the lungs,

to the other side. It then goes through the arteries to all

parts of the body, and finally, through the veins and

back to the heart again.

Through the scientific method, Harvey made a great

contribution to modern medicine and surgery—the

knowledge that blood circulates.

29

VAN JlEiIuWENHOEK

William Harvey died in 1657. But while he was still

making his discoveries about the circulation of the blood,

another young scientist was just growing up in Holland.

Only no one in the world would have thought of the

young Dutchman as a scientist—then.

Antony van Leeuwenhoek was born in 1632 in Delft,

Holland. He left school when he was sixteen and took a

job in a dry goods store in Amsterdam. When he was

grown up and had learned the business, Leeuwenhoek

went back to his home town, was married, and opened

a dry goods store of his own. To increase his income, he

got a part time job as the janitor of the Delft city hall.

It doesn't sound as if a man who owned a store, held

a job, and was raising a family would have much spare

time. But Leeuwenhoek, like many modern men, man-

aged to find a bit of time for his hobby—grinding lenses.

Eyeglasses, and other crude magnifying glasses, had

been invented long before and Leeuwenhoek thought

it very interesting to see things enlarged. He learned

from spectacle makers how to make lenses that enlarged

things two or even three times. But why stop there?

32

Leeuwenhoek developed a burning wish to make better

lenses and see smaller and smaller things. The more he

saw, the more curious he became. He fashioned a crude

microscope from his lenses and then worked tirelessly

to make the microscope better and better. It is probable

that the dry goods store was neglected, and that the city

hall grew dusty!

Leeuwenhoek began to examine strange things with

his microscope. He looked at skin, at animal eyes and

muscles, at parts of insects. He was astonished at the

things he saw. But he kept them all to himself. Leeu-

wenhoek was an uneducated man. He had never heard

of the scientific method. But he was a careful and a cau-

tious man. He wasn't going to say anything to anybody

until he was sure. So for twenty years, Leeuwenhoek

went on building finer microscopes, peering, studying,

peering some more, and checking and double checking

all of his experiments.

And then one day, Leeuwenhoek trained his micro-

scope on a drop of clean rain water. He stared, rubbed

his eyes, and stared again. Tumbling about in the water,

jumping and playing for all the world like a litter of

puppies, were hosts of tiny animals! Animals in a drop

of water? Impossible! And yet, there they were.

But Leeuwenhoek, the cautious man, didn't jump to

33

any conclusions. He had his hypothesis, he experimented

again and again, he checked his theories—3,nd always,

there were the "little beasties" as he called them. Whena drop of newly fallen rain showed no signs of life, Leeu-

wenhoek kept it for a few days. When he examined

it again, there were the "beasties." So, he reasoned, the

tiny animals did not come down from the sky with the

rain. Where did they come from?

The animals appeared to be everywhere. Leeuwen-

hoek was astonished to find them even in his mouth!

When endless observations and experiments finally

convinced Leeuwenhoek that he had made no mistake,

he wrote a letter to the Royal Society of England. In

pages and pages of painstaking script, Leeuwenhoek

described his tiny animals. They were so small, he said,

that a single drop of water held two million seven hun-

dred of them! He estimated that one animal was a

thousand times smaller than the eye of a louse.

The men of the Royal Society were interested in

Leeuwenhoek's letter, but they wanted to see for them-

selves. They wrote back asking the Dutchman to tell

them how he made his microscopes. Leeuwenhoek, how-

ever, was not ready to give away his secrets. The Royal

Society would have to find its own way to build micro-

scopes if they wanted to see the beasties.

34

And that is just what they did. Robert Hooke and

Nehemiah Grew were appointed to build a microscope

and to follow Leeuwenhoek's instructions for finding the

animals. On November 15, 1677, they succeeded, and

the most learned scientists of the world looked for the

first time at Leeuwenhoek's astonishing animals, or

microbes, as they came to be called (from the Greek

words micros, small, and bios, life).

Antony van Leeuwenhoek lived to be ninety-one years

old. Before his death he found the tiny capillary blood

vessels which carry the blood from the arteries to the

veins. The last proof of Harvey's circulation of the blood

was demonstrated. And a whole new world of investiga-

tion was opened up. The discovery of microbes was to

lead men on to finding the causes and the cures of manydiseases.

C641810

35

;'«^'f^

^'^:'

Z-

,^^

•^^

V:' W^ v

BENJAMl^4 /

FRANK;^'/

i

6A key, a kite

and the method

While the use of the scientific method was spreading

all over Europe, ripples of the wave were being felt in

the New World, too. The first great experimental scien-

tist in America was Benjamin Franklin, who was born

in Boston in 1706.

Franklin was famous as a statesman, an inventor, and

an investigator in many branches of science. His most

important contributions, however, were in the field of

electricity.

Electricity itself was not a new discovery. A British

doctor named William Gilbert had done some experi-

ments with electricity around the year 1600. Then, in

the early 1700's, a Frenchman named Charles du Fay

decided that there were two different kinds of electricity.

In 1745, Pieter van Muschenbroek of Leyden, Hol-

land, invented the Leyden jar. This was a specially con-

structed jar that could hold a charge of electricity. Whentouched, the jar gave up its charge with a resulting shock.

This was considered a great curiosity, and even though

an electric shock is quite unpleasant, many people were

very eager to experience it.

38

Benjamin Franklin, through careful use of the scien-

tific method, found out the true nature of electricity and

gave to the world one of the most powerful tools ever

discovered.

One of Franklin s first great discoveries was that there

are not two different kinds of electricity. There is only

one kind of electricity but it can appear in two forms,

positive or negative. This happens because there is either

too much or too little electric fluid. Electric fluid was a

term of Franklin's day. Nowadays, we talk about protons

and electrons instead. If a body has more protons than

electrons, it is positively charged. If it has more elec-

trons than protons, it is negatively charged.

Franklin's hypothesis was that if positively and nega-

tively charged bodies were brought close together, the

extra electric fluid would jump to the body that didn't

have enough. If a body that had no charge at all were

brought near either of the charged bodies—it would give

up fluid to the body that didn't have enough, or take

fluid from the body that had too much.

Franklin tested his hypothesis with the following

experiment:

He placed two men on insulated glass stools. One

man had a positive charge, the other a negative charge.

When the two men touched hands, they both became

39

uncharged because the extra charge flowed to the man

who didn't have enough.

Then the experiment was repeated with a third man

who was uncharged. When he touched either of the

charged men, he got a shock or drew a spark.

FrankUn conducted many other simple but dramatic

experiments which changed the whole field of electrical

study. But probably his most famous experiment was the

one that proved that lightning is electricity.

It may seem to you that such a simple fact doesn't

need any proof—but it wasn't so in 1752. It was popularly

believed that lightning was caused by explosions of

gases in the air.

Franklin proved that lightning was electricity in the

following way: First, he made a paper kite and tied a

very long string to it. Then he attached a metal key to

the end of the string. He planned to fly the kite during

a storm, so he knew that the string would get wet. Since

electricity flows easily along wet cotton string, Franklin

reasoned that if there were electricity in the storm

clouds, it would travel down the string to the key.

If Franklin had held the key, the electricity would

have passed right through the string and the key and

into him. To prevent this, Franklin tied a piece of silk

thread beneath the key and used it for a handle. He

40

knew that electricity will not flow through silk if it is

kept dry.

With his kite all ready, Franklin waited for a thunder

storm. Finally, one came. He ran outside but stood in the

shelter of a doorway. He was very careful to keep the bit

of silk thread in his hand dry.

Suddenly there was a brilliant flash of lightning and

a mighty crash of thunder. Had anything happened to

the kite? Franklin cautiously moved his finger toward

the key. Before he even touched it, a large spark jumped

from the key to his finger.

Franklin's hypothesis certainly seemed to be correct.

Further tests proved all of his theories. His book, Experi-

ments and Observations on Electricity Made at Phila-

delphia in America became one of the most popular

science books of the eighteenth century. It was printed

in French, Italian, and German, as well as in English.

Science and the quest for knowledge had advanced to

the point where Franklin did not have to fear for his life

because of his new ideas. Instead, he was honored all

over the world.

41

mfv

CH/^^UES DARWIN

PROTOHIPPUS

Darwin

and evolution

At the beginning of the nineteenth century there

were new thoughts popping up everywhere concerning

the origin of life. Almost everyone in the western world

believed that the story of creation as it was told in the

Bible was literally true. They believed that every kind of

living thing had been created in the first days, that each

plant and animal had come down through the ages

exactly as it had been made in the first place—and

yet . . .

There were many observers of nature throughout

Europe who began to think that perhaps the story of

creation in Genesis could be understood in new ways.

Jean Baptiste Lamarck in France dared to suggest that

different species of animals had descended one from the

other. Erasmus Darwin in England agreed with Lamarck

but went even further. Darwin felt that the competition

between living things had something to do with their

progress.

A British minister, Thomas Malthus, had published in

1798, An Essay on the Principle of Population. Malthus

pointed out that living beings multiply at such a rate

44

that the world could not possibly supply enough food

for them all. It was necessary for large numbers of ani-

mals to die—and people, too, through disease and wars

—to keep the world going.

Against this background of ideas, Charles Darwin,

son of a doctor and grandson of Erasmus Darwin, was

born in England in 1809. As a young man, he gave up

the idea of becoming, first, a doctor, and second, a

minister. The only thing that really interested him was

natural history. His endless fiddling with growing things

seemed like a waste of time to his family. They wished

that he would do something "useful."

But the young man's teachers felt differently. Whenthey heard of an opening for a naturalist on a govern-

ment ship, they recommended Darwin for the job.

And so, in December, 1831, Charles Darwin set sail

in the brig Beagle for a voyage of scientific exploration.

The trip was to last five years and to take the little ship

around the world.

Wherever the ship touched shore during the long

cruise, Darwin made painstaking collections of animals,

plants, rocks, fossils—anything at all relating to life. Hewas a careful observer, and certain questions kept

cropping up in his mind.

Why were the plants and animals on the islands often

45

diflFerent from those on the mainland? And why did it

happen that in a chain of islands (like the Galapagos)

the living things on one island were sometimes almost

like those on the next island, but yet a little diflFerent?

Why were there fossil bones of huge animals that did

not seem to exist any longer? Why did the birds on one

island have so many diflFerent kinds of beaks?

The answers to these questions began to simmer in

Darwin's mind. But he had to be sure. Slowly, carefully,

patiently, he observed, collected, listed, made notes, and

observed some more.

When the Beagle returned to England in 1836, Darwin

continued his investigations. He studied the breeding

patterns of domestic animals and experimented widely

himself, with the breeding of pigeons. For more than

twenty years, he labored. Always, he observed, hypothe-

sized, experimented, theorized, and proved. Finally, in

1859, Darwin published his famous book. Origin of

Species.

In the book, Darwin showed, as a result of his careful

scientific work, that all living things have undergone

changes in order to survive. This change from one kind

of plant or animal to another kind is called evolution.

Birds have diflFerent kinds of beaks because they eat

diflFerent kinds of food. Animals on one island are dif-

46

ferent from those on the next island because they need

to be in order to survive. As the island is different, the

animals have to adapt to its condition.

Malthus was right about the number of animals being

too great for the amount of food in the world—but

Darwin finished the thought. The animals which were

most jit, lived. The others perished.

By this means, Darwin pointed out, living things have

always improved. The strong ones, the smart ones, the

fast runners, the best nest-builders, the finest fighters,

the expert hiders, and so on, remained to be the parents

of the next generation. The weaklings eventually died

out.

Actually, another man, Alfred Russel Wallace, came

to the same conclusions about evolution as Darwin, and

at about the same time. He and Darwin had their first

papers on the subject published together. Darwin, how-

ever, is the man people remember for his great work.

On the Origin of the Species by Means of Natural Selec-

tion, or the Preservation of Favoured Races in the Strug-

gle for Life—SiS his book was called before the title was

shortened.

The secret of Darwin's contribution can be found in

his own words in his autobiography:

47

My first notebook was opened on July 1837.

I worked on true Baconian principles, and with-

out any theory collected facts on a wholesale

scale . . . fifteen months after I had begun mysystematic enquiry, I happened to read for

amusement Malthus on population, and being

well prepared to appreciate the struggle for ex-

istence which everywhere goes on from long

continued observation of the habits of animals

and plants, it at once struck me that under these

circumstances favourable variations would tend

to be preserved, and unfavourable ones to be

destroyed. The result of this would be the for-

mation of a new species. Here then I had at last

got a theory by which to work.

When, after twenty years, Darwin finally proved his

theory, there was an uproar heard around the world.

But not for long. Darwin's proof could not be ignored.

All of the work in biology (the study of living things)

since that time has been based on it.

Darwin's work was by no means ended with Origin

of Species. Proceeding in his usual, careful, scientific

way, he went on to publish The Fertilisation of Orchids

in 1862, The Variation of Plants and Animah under Do-

48

mestication in 1867, and The Descent of Man in 1871.

The latter became almost as famous as Origin of Spe-

cies. Following, there were still more books. All of them

proved, through the scientific method, the theory of

evolution in both plants and animals.

49

f

mw^ w

8The wizard

of Menio Park

Thomas Alva Edison was born in the United States,

in Milan, Ohio, in 1847. He showed his natural curiosity

at a very early age—when he tried to hatch eggs by sitting

on them. He also tried to make a friend light enough to

fly by feeding him quantites of a fizzy headache medi-

cine!

When Thomas was seven, his family moved to Port

Huron, Michigan. Instead of appreciating the young

genius, the local schoolteacher declared that Edison was

"addled" and couldn't be taught.

Thomas' mother, who was a teacher, knew better, how-

ever. She decided to keep her son at home and teach

him herself. The training she gave him helped him to

become one of the greatest inventors the world has ever

known. All his life Edison followed his mother's three

basic rules—read, experiment, and think.

While he was still quite young ( about ten years old

)

Edison became fascinated by one of his science books.

He made himself a laboratory in his basement and care-

fully tried all of the chemistry experiments suggested

in the book. Then he experimented on his own. Un-

52

doubtedly, by the time he was twelve, Edison was a

highly experienced follower of the scientific method.

Young Tom got a job selling papers and candy on a

train. With the money he earned, he was able to buy

books and equipment for his scientific experiments. One

of the things that interested him was the "new" telegraph.

Tom bought the necessary apparatus, rigged up a home-

made set and taught himself to operate it, becoming one

of the country's fastest telegraph operators.

Edison started inventing things while he was still in

his teens. He developed a machine to tell stockbrokers

all over the country the prices of stocks at the Stock Ex-

change in New York. This invention made enough

money for Edison to leave his job as a telegraph operator

when he was twenty-three years old and to do what he

had dreamed of for years—open his own fully staffed

laboratory in Menlo Park, New Jersey.

From then on, the inventions almost poured out.

Beginning in 1870, Edison patented an average of one

new invention every month for six years!

Edison invented telegraph systems which permitted

many messages to be sent at the same time; he helped

develop the typewriter; he invented the mimeograph

machine and wax paper; he devised a new type of fire

alarm and made improvements in the telephone.

In 1877, while Edison was experimenting with a tele-

53

phone, he felt a sharp steel point on the back of it vibrate

when he spoke. Getting a brilliant idea, Edison held a

piece of stiff paper against the steel point and said

"Hello." The vibrating point made a little groove in the

paper. Edison then pushed the point a second time over

the groove. Very faintly, he heard, "Hello."

Edison promptly made a sketch for a machine which

would record sound by means of a vibrating needle that

cut grooves in tinfoil. One of his mechanics put the

machine together and then stood staring and unbeliev-

ing as the machine clearly repeated after Edison, "Mary

had a little lamb, its fleece was white as snow . .

."

Edison called his new talking machine a phonograph,

from the Greek words for sound and to write.

Of all his inventions, none brought Edison as much

fame as the electric light bulb. Electric arc lights, in-

vented by Sir Humphrey Davey at the beginning of the

nineteenth century, were commercially manufactured

by Edison's time. But arc lights gave an unsteady light,

made a lot of noise, and hurt the eyes. Edison felt that

he could make a good light by passing electric current

through a filament until it was hot enough to glow. But

how could the filament get that hot without burning up?

Edison's solution was to place the filament inside a

glass bulb from which all the air had been pumped.

54

Without any oxygen, the filament couldn't burn up and

therefore would last a long time.

The first bulb Edison made used a platinum filament.

This worked fairly well, but the platinum was terribly

expensive. Edison began to experiment. He tested many,

many filament materials—one after the other. None was

satisfactory. Then Edison decided to try something very

simple—ordinary sewing cotton, baked in a furnace until

it was charred. You can imagine how hard this material

was to handle. It broke under the slightest touch. And

yet, after many attempts, Edison finally managed to bend

a piece of the carbonized thread into a loop and seal it

into a bulb. When the current was turned on, the bulb

glowed brightly. It remained lighted for over forty hours,

beginning on October 21, 1879.

From then on, it was only a matter of a few years until

Edison solved the problems of manufacturing really good

incandescent lamps (as light bulbs are properly called).

Electric lights soon became commonplace.

Among Edison's other great achievements were the

development of the electric railroad and the invention

of motion pictures. When he died in 1931, he was fa-

mous all over the world as the "Wizard of Menlo Park."

But wizards make us think of magic, and Edison didn't

practice magic. He followed the scientific method.

55

Miracle

medicines

In modern times, there is not so much talk about the

scientific method—it is taken completely for granted. All

scientists learn it as part of their early training. It is as

natural to them as breathing. It is their way of working,

their way of life. And so, an almost automatic observa-

tion led Alexander Fleming to one of the most important

medical discoveries of all time.

The year was 1928; the place, St. Mary's Hospital in

London. Fleming was at work in his laboratory. It was a

warm September day and he had left the window open.

He was experimenting with disease germs and he had a

dish of germs (a culture) on the windowsill. A bit of

mold had formed on the top of the culture, common blue-

green mold, the kind you sometimes find on a stale,

decaying lemon.

Fleming walked over to catch the breeze from the

window. Casually, his glance fell on the dish. He noticed

something very strange. The thick, cloudy culture had

turned clear all around the patch of mold. Where the

liquid was clear there couldn't be any germs. What had

happened to them? Fleming guessed (hypothesis) right

away that this might be something important.

58

1

He scraped off the bit of mold and put it into a culture

dish of its own. When the tiny patch of mold had grown

larger, Fleming began to experiment with it to see if it

could kill germs. It could!

One experiment followed another, and finally, Flem-

ing managed to squeeze a tiny drop of brownish fluid

from the mold. This was the germ killer. Fleming decided

to call it penicillin from Penicillium, the name of the

blue-green mold.

Penicillin proved in every test to be the best germ

killer ever discovered. But it took so long to make a single

drop of it, that it didn't seem as if it could ever be of any

use. Fleming stopped his experiments and went back

to his other work.

During World War II, however, there was a sudden

interest in new medicines for wounded soldiers. Twodoctors at Oxford University read about penicillin and

decided it was worth investigating. The doctors. Sir

Howard W. Florey and Ernst B. Chain, tried to pre-

pare the magic brown drops. They, too, found the going

very slow. The medicine was exciting—but impractical.

Then, in 1941, Dr. Florey came to the United States.

He and his fellow workers decided to search for a better

mold than the original one. Perhaps some other variety

would yield more penicillin. One fine day, an assistant

59

found a half rotten, very moldy cantaloupe in a fruit store

in Peoria, Illinois. She took it back to the laboratory. That

mold contained two hundred times as much penicillin

as Fleming's original mold.

And so the work begun by Fleming's observation,

hypothesis, and early experiments was carried on by

others. By 1946, penicillin was being made in big batches,

and millions of lives were saved with it. It was considered

a miracle medicine—but it was only the first of many

miracle medicines. If a mold could produce penicillin,

scientists reasoned, why couldn't other molds contain

other miracle drugs?

Professor Selman Waksman at Rutgers University was

particularly interested in the molds that grew in the soil.

He tested ten thousand different kinds! He tried out

each new mold in a germ culture like Fleming's—and

one day he was rewarded by seeing that beautiful, clear

ring all around the patch of mold. Waksman called his

new drug streptomycin.

Then the search was really on. Travelers were asked

to send in samples of soil from all over the world. Thou-

sands upon thousands of these samples were tested. Most

of the tests led to nothing. A few led to still better won-

der drugs.

Today, drugs from molds, or antibiotics, are in every-

60

day use all over the world. The next time you are sick and

your doctor makes you well with one of these drugs,

remember the devoted followers of the scientific method

who made this cure possible for you.

61

ENRICO FERMI

kl

10

Old method,

New World

Throughout the great sweep of scientific discovery

and development, certain achievements have stood out.

They have often been important enough to give their

names to the periods in which they happened. You were

born into such a period—the Atomic Age.

It is too bad that the world's first experience with

atomic energy came through its use in a war. For this

great, new tool of mankind can also be used to do fine

things never before dreamed of. It can supply power,

ease labor, improve health, provide better food. In short,

it can make the world an easier, healthier, better place

in which to live. Atomic energy is one of the great

triumphs of science, and a triumph for the scientific

method.

The ancient Greeks had made up the word atom to

mean a particle so tiny that it couldn't be divided. And

right into modern times, people believed that an atom

was the smallest thing there was. It was unsplittable,

indivisible—unconquerable.

But by the early part of the twentieth century it was

known that atoms were made of still smaller particles.

64

And in 1919, Ernest Rutherford, an English scientist,

split an atom for the first time.

By the middle of the 1930's, scientists were thinking

quite a bit about what would happen if one could split

the center, or nucleus, of the atom in such a way as to

make the exploding atom explode other atoms. This

process would be called a chain reaction.

In 1942, during World War II, a group of scientists

who had been working very hard on the problem of

atomic chain reactions, were ready to experiment for

the first time. The leader of the group was Enrico Fermi,

an Italian scientist who had come to this country.

On a cloudy morning in December the men met in

what had once been a squash court at the University of

Chicago. They entered through a door underneath the

football stadium.

The men had been in that room before. In fact, they

had been at work for days stacking up a huge pile of

graphite bricks. Here and there among the bricks they

had placed a piece of a radioactive element called

uranium. Fermi believed that when the pile reached a

certain size, a chain reaction would take place.

On the morning of December 2, 1942, the prepara-

tions had been finished and the great experiment was

about to start. Buried in the pile were three cadmium

65

rods. They were called control rods because while they

were in place nothing could happen. When they were

removed, the chain reaction would begin—the men

hoped!

Nearby were several Geiger counters. These are instru-

ments which tick whenever they are near atomic rays.

The counters would tell the scientists if a reaction began

and if the chain stage had been reached.

The first two control rods were drawn out of the pile.

The counters began to tick. Then Fermi gave the com-

mand to start pulling out the third rod. It was marked in

feet, and Fermi said, "Pull it out to thirteen feet." Every-

one watched the instruments. "Pull it out another foot."

Not yet. The men hardly dared breathe. Another foot.

Another inch. A little more. The counters ticked a little

faster. More. A little more.

Finally, after hours of tense and careful work, Fermi

said, "Pull it out another foot. This is going to do it!"

Suddenly the counters seemed to go mad. It had

worked! The chain reaction was in progress.

After twenty-eight minutes of operation, the control

rods were put back into the pile. The first chain reaction

had been started and had been stopped.

Arthur H. Compton, one of the men in the room, ran

to a telephone. He wanted to notify James B. Conant,

66

Chairman of the United States National Defense Re-

search Committee. However, this was top-secret informa-

tion because our country was at war. To make sure no

one else got his message, Compton said, "Ji^? you'll

be interested to know that the Italian navigator has just

landed in the New World."

Conant said, "Is that so? Were the natives friendly?"

And Compton replied, "Everyone landed safe and

happy."

Just as the Italian navigator, Columbus, had landed in

a new world, so the Italian physicist, Fermi, also landed

in a new world—the world of atomic energy. Like the

long line of great scientists before him, Fermi did his

valuable work by using the scientific method.

67

1

Index

I

antibiotics, 60

Aristotle, 16, 20, 21

atom, 64

Atomic Age, 64

atomic pile, 65

Bacon, Francis, 16

Beagle, 45

blood, 26

electron, 39

evolution, 46

Fabricius, Hieronymus, 28

falling bodies, 20, 22

Fermi, Enrico, 65

Fleming, Alexander, 58

Florey, Dr. Howard W., 57

Franklin, Ben, 38

Chain, Dr. Ernst, 59

chain reaction, 65

Compton, Arthur H., 66

Conant, James B., 66

control rods, 66

Copernicus, 21

da Vinci, Leonardo, 20

Darwin, Charles, 45

Darwin, Erasmus, 45

du Fay, Charles, 38

Edison, Thomas A., 52

Egyptians, 15

electric fluid, 39

electricity, 38

electric light bulb, 54

Galen, 26

Galileo, 21

Geiger counter, 66

Gilbert, William, 38

gravity, 22

Greeks, 15, 22, 26, 64

Grew, Nehemiah, 35

Harvey, William, 28

Hooke, Robert, 35

incandescent lamp, 55

Lamarck, Jean Baptiste, 44

Leeuwenhoek, Antony van, 32-35

Leyden jar, 38

lightning, 40

71

Malthus, Thomas, 44, 47

microbes, 35

microscope, 33

mold, 58

Muschenbroek, Pieter van, 38

negative charge, 39

nucleus, 65

Origin of Species, 46

penicillin, 59

Penicillium, 59

phonograph, 54

positive charge, 39

proton, 39

Ptolemy, 21

Rutherford, Ernest, 65

scientific method (def. ), 12

septum, 26

Servetus, Michael, 27

Stevin, Simon, 20

streptomycin, 60

telegraph, 53

telescope, 22

uranium, 65

Vesalius, Andreas, 27

Waksman, Selman, 60

Wallace, A. R, 47

72

I