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LIBRARY

OF THE

UNIVERSITY OF CALIFORNIA.

Class

MARCONI WIRELESS TELEGRAPH STATION, CLIFDEN, IRELAND

Photographed at night while sending a message across the Atlantic.

The terrific snapping of the electric discharge is heard by one
standing near the station, but no light is seen. The strange light
given out from the network of wires is invisible to the eye, but is
caught by the photographic plate.

THE SAME STATION PHOTOGRAPHED BY DAYLIGHT

THE STORY OF
GREAT INVENTIONS

ELMER ELLSWORTH BURNS

* INSTRUCTOR IN PHYSICS IN THE

JOSEPH MEDILL HIGH SCHOOL, CHICAGO

WITH MANY ILLUSTRATIONS

HARPER & BROTHERS PUBLISHERS

YORK AND LONDON
M CMX

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Published November, IQIO.
Printed in the United States of America

CONTENTS

CHAPTER I

THE AGE OF ARCHIMEDES

Archimedes the first great inventor. — The battle of Syracuse. — Archi-
medes' principle. — Inventions of the ancient Greeks . . . Page i

CHAPTER II

THE AGE OF GALILEO

Galileo and the battle for truth. — The pendulum clock. — Galileo's ex-
periment with falling shot. — The telescope. — Galileo's struggle. —
Torricelli and the barometer. — Otto von Guericke and the air-pump. —
Robert Boyle and the pressure of air and steam. — Pascal and the
hydraulic press. — Newton. — Gravitation. — Colors in sunlight . Page 9

CHAPTER III
THE EIGHTEENTH CENTURY

James Watt and the steam-engine. — The first steam-engine with a piston.
— Newcomen's engine. — Watt's engine. — Horse-power of an engine. —
The Leyde.n jar. — Conductors and insulators. — Two kinds of electric
charge. — Franklin's kite experiment. — The lightning-rod. — Galvani
and the electric current. — Volta and the electric battery . . Page 34

CHAPTER IV
FARADAY AND THE FIRST DYNAMO

Count Rumford. — Count Rumford's experiment with the cannon. — Davy.
— Faraday's electrical discoveries. — Oersted and electromagnetism. —
Ampere. — Arago. — Faraday's first electric motor. — An electric current
produced by a magnet. — Detecting and measuring an electric current.
— An electric current produced by the magnetic field of another cur-
rent.— Faraday's dynamo. — A wonderful law of nature . , Page 55

235469

CONTENTS

CHAPTER V

GREAT INVENTIONS OF THE NINETEENTH CENTURY
Electric batteries. — The dry battery. — The storage battery. — The dy-
namo.— Siemens' dynamo. — The drum armature. — Edison's compound-
wound dynamo. — Electric power. — The first electric railway. — Electric
lighting. — The telegraph. — Duplex telegraphy. — The telephone. — The
phonograph. — Gas-engines. — The steam locomotive. — How a locomo-
tive works. — The turbine Page 88

CHAPTER VI

THE TWENTIETH-CENTURY OUTLOOK

Air-ships. — The aeroplane. — How the Wright aeroplane is kept afloat. —
Submarines. — Some spinning tops that are useful. — The monorail-car.
— Liquid air and the greatest cold. — The electric furnace and the
greatest heat. — The wireless telegraph — The wireless telephone. —
Wonders of the alternating current. — X-rays and radium . Page 173

APPENDIX
Brief notes on important inventions Page 237

INDEX Page 247

ILLUSTRATIONS

FIG. PAGE

MARCONI WIRELESS-TELEGRAPH STATION, CLIFDEN, IRELAND )
THE SAME STATION PHOTOGRAPHED BY DAYLIGHT . . )

I THE BATTLE OF SYRACUSE 3

2 — GALILEO'S PENDULUM CLOCK n

3 AN AIR THERMOMETER 14

4 TORRICELLl'S EXPERIMENT 19

5 — GUERICKE'S AIR-PUMP . . . 22

6 — GUERICKE'S WATER BAROMETER 24

7 A LIFT-PUMP 25

8 A SIMPLE HYDRAULIC PRESS 26

9 HOW AN HYDRAULIC PRESS WORKS 28

IO AN HYDRAULIC PRESS WITH BELT-DRIVEN PUMP 29

ii — NEWTON'S EXPERIMENT WITH THE PRISM . 32

12 — PAPIN'S ENGINE » 36

13 THE NEWCOMEN ENGINE, IN REPAIRING WHICH WATT WAS LED

TO HIS GREAT DISCOVERIES 39

14 CYLINDER OF WATT'S STEAM-ENGINE 41

15 A FLY-BALL GOVERNOR 42

l6 A LEYDEN JAR 43

17 — FRANKLIN'S KITE EXPERIMENT 47

l8 VOLTA EXPLAINING HIS ELECTRIC BATTERY TO NAPOLEON BONA-
PARTE 52

19 THE FIRST ELECTRIC BATTERY 54

20 — COUNT RUMFORD'S EXPERIMENT WITH THE CANNON, MAKING

WATER BOIL WITHOUT FIRE 60

21 — OERSTED'S EXPERIMENT 66

22 A COIL WITH A CURRENT FLOWING THROUGH IT ACTS LIKE A

MAGNET 67

23 A BAR OF SOFT IRON WITH A CURRENT FLOWING AROUND IT BE-
COMES A MAGNET 67

24 TWO COILS WITH CURRENTS FLOWING IN THE SAME DIRECTION

ATTRACT EACH OTHER 68

25 TWO COILS WITH CURRENTS FLOWING IN OPPOSITE DIRECTIONS

REPEL EACH OTHER 68

26 ARAGO'S EXPERIMENT ,,,,... 70

ILLUSTRATIONS

FIG. PAGE

27 ONE POLE OF A MAGNET SPINS ROUND A WIRE THROUGH WHICH

AN ELECTRIC CURRENT FLOWS 71

28 WHEN A MAGNET IS THRUST INTO A COIL OF WIRE IT CAUSES A

CURRENT TO FLOW IN THE COIL, BUT THE CURRENT FLOWS

ONLY WHILE THE MAGNET IS MOVING 73

29 A COIL OF WIRE AROUND A COMPASS-NEEDLE 74

30 — FARADAY'S INDUCTION-COIL 76

31 HISTORICAL APPARATUS OF FARADAY IN THE ROYAL INSTITUTION 77

32 — FARADAY'S FIRST DYNAMO 78

33 — FARADAY'S LABORATORY, WHERE THE FIRST DYNAMO WAS

MADE 79

34 THE FIRST TRANSFORMER 80

35 — THE "MAGNETIC FIELD" is THE SPACE AROUND A MAGNET

IN WHICH IT WILL ATTRACT IRON 8l

36 MAGNETIC FIELD OF A HORSESHOE MAGNET . . . . . . 8l

37 A DANIELL CELL 90

38 A GRAVITY CELL 91

39 SHOWING WHAT IS IN A DRY BATTERY 92

40 A STORAGE BATTERY, SHOWING THE " GRIDS " 94

41 A STORAGE-BATTERY PLATE MADE FROM A SHEET OF LEAD . . 95

42 — STURGEON'S ELECTROMAGNET 97

43 AN ELECTROMAGNET WITH MANY TURNS OF INSULATED WIRE . 98

44 AN ELECTROMAGNET LIFTING TWELVE TONS OF IRON ... 99

45 A DYNAMO WITS SIEMENS* ARMATURE 1OI

46 RING ARMATURE IO2

47 FIRST DYNAMO PATENTED IN THE UNITED STATES .... 103

48 A DRUM ARMATURE, SHOWING HOW AN ARMATURE OF FOUR

COILS IS WOUND 104

49 A SERIES-WOUND DYNAMO IO6

50 A SHUNT-WOUND DYNAMO 107

51 A COMPOUND-WOUND DYNAMO IO8

52 — ONE OF EDISON'S FIRST DYNAMOS 109

53 A DYNAMO MOUNTED ON THE TRUCK OF A RAILWAY CAR . . . HO

54 FIRST ELECTRIC LOCOMOTIVE 113

55 FIRST EDISON ELECTRIC LOCOMOTIVE 115

56 — EDISON'S FIRST PASSENGER LOCOMOTIVE 117

57 FIRST COMMERCIAL ELECTRIC RAILWAY 119

58 — EDISON, AMERICA'S GREATEST INVENTOR, AT WORK IN HIS

LABORATORY 122

59 — EDISON'S FAMOUS HORSESHOE PAPER-FILAMENT LAMP OF 1870. 123
60 FIRST COMMERCIAL EDISON ELECTRIC-LIGHTING PLANT; IN-
STALLED ON THE STEAMSHIP "COLUMBIA" IN MAY, 1880 . 125

6l A TELEGRAPH SOUNDER .....,,, 129

viii

ILLUSTRATIONS

FIG. PAGE

62 — MORSE'S FIRST TELEGRAPH INSTRUMENT 131

63 A TELEGRAPHIC CIRCUIT WITH RELAY AND SOUNDER. . . . 132

64 A SIMPLE TELEGRAPHIC CIRCUIT 133

65 FIRST TELEGRAPH INSTRUMENT USED FOR COMMERCIAL WORK . 135

66 HOW TWO MESSAGES ARE SENT OVER ONE WIRE AT THE SAME

TIME 137

67 HOW TWO MESSAGES ARE SENT OVER ONE WIRE AT THE SAME

TIME. BRIDGE METHOD ....'.. 139

68 FIRST BELL TELEPHONE RECEIVER AND TRANSMITTER . . . 142

69 A TELEPHONE RECEIVER 143

70 TWO RECEIVERS USED AS A COMPLETE TELEPHONE .... 145

71 CARBON-DUST TRANSMITTER • 146

72 THE PHONAUTOGRAPH, A FORERUNNER OF THE PHONOGRAPH . 149

73 — EDISON'S FIRST PHONOGRAPH AND A MODERN INSTRUMENT . 150

74 tO 77 THE FOUR-CYCLE GAS-ENGINE 152

78 TWO-CYCLE GAS-ENGINE. CRANK AND CONNECTING-ROD ARE

ENCLOSED WITH THE PISTON . . . . . , ". . . . 154
79 — SELDEN "EXPLOSION BUGGY," FORERUNNER OF THE MODERN

AUTOMOBILE 155

80 SOME EARLY LOCOMOTIVES 158

8 1 HOW A LOCOMOTIVE WORKS l6l

82 — HERO'S ENGINE * 164

83 AN UNDERSHOT WATER-WHEEL WITH CURVED BLADES . . . 165

84 AN OVERSHOT WATER-WHEEL 1 66

85 DE LAVAL STEAM-TURBINE 167

86 A MODERN STEAM-TURBINE WITH TOP CASING RAISED SHOWING

BLADES l68

87 DIAGRAM OF TURBINE SHOWN IN FIG. 86 169

88 A STEAM-TURBINE THAT RUNS A DYNAMO GENERATING I4,OOO

ELECTRICAL HORSE-POWER 170

89 BRITISH ARMY AIR - SHIP "NULLI SECUNDUS" READY FOR

FLIGHT 176

90 BASKET, MOTOR, AND PROPELLER , OF THE BRITISH ARMY AIR-
SHIP "NULLI SECUNDUS" 178

91 A ZEPPELIN AIR-SHIP l8l

92 — COUNT ZEPPELIN'S "DEUTSCHLAND," THE FIRST AIR-SHIP IN

REGULAR PASSENGER SERVICE 182

93 THE BALDWIN AIR-SHIP USED IN THE UNITED STATES ARMY . . 183

94 — IN FULL FLIGHT 185

95 WRIGHT AIR-SHIP IN FLIGHT 187

96 HOW THE WRIGHT AIR-SHIP IS KEPT AFLOAT 189

97 THE SEAT AND MOTOR OF THE WRIGHT AEROPLANE . . . . 191

98 THE BLERIOT MONOPLANE 192

ILLUSTRATIONS

FIG. PAGE

99 — THE "PLUNGER" 195

100 U. S. SUBMARINE " SHARK" READY FOR A DIVE 197

101 FIRST SUBMARINE CONSTRUCTED IN THE UNITED STATES. IT

WENT TO THE BOTTOM WITH SEVEN MEN, WHO WERE

DROWNED 198

IO2 HOW MEN IN A SUBMARINE SEE WHEN UNDER THE WATER . 199

103 A TOP THAT SPINS ON A STRING 2OO

104 A CAR THAT RUNS ON ONE RAIL 2O2

105 MANUFACTURING DIAMONDS FIRST OPERATION 207

106 MANUFACTURING DIAMONDS SECOND OPERATION .... 209

107 MANUFACTURING DIAMONDS THIRD OPERATION 211

I08 MARCONI AND HIS WIRELESS - TELEGRAPH SENDING AND RE-
CEIVING INSTRUMENTS . 215

109 DIAGRAM OF WIRELESS-TELEGRAPH SENDING APPARATUS . . 217

1 10 DIAGRAM OF MARCONI WIRELESS-TELEGRAPH RECEIVING

APPARATUS 2l8

III RECEIVER OF BELL'S PHOTOPHONE 223

112 A GAS FLAME IS SENSITIVE TO ELECTRIC WAVES .... 224

113 CAPTAIN INGERSOLL ON BOARD THE U. S. BATTLE - SHIP

"CONNECTICUT" USING THE WIRELESS TELEPHONE . . 226
114 INCANDESCENT ELECTRIC LAMP LIGHTED THOUGH NOT CON-
NECTED TO ANY BATTERY OR DYNAMO 229

115 AN ELECTRIC DISCHARGE AT A PRESSURE OF I2,OOO,OOO VOLTS,

A CURRENT OF 8OO AMPERES IN THE SECONDARY COIL . . 230

Il6 AN ELECTRIC DISCHARGE SIXTY-FIVE FEET IN LENGTH . . 231

117 A PHYSICIAN EXAMINING THE BONES OF THE ARM BY MEANS

OF X-RAYS .*...... 233

Il8 X-RAY PHOTOGRAPH OF THE EYE 234

119 PHOTOGRAPH MADE WITH RADIUM 235

INTRODUCTORY NOTE

inventions are a never-failing source of interest
to all of us, and particularly to the boy in his teens.
The dynamo, the electric motor, the telegraph, with and
without wires, the telephone, air-ships, and many other
inventions excite in him an interest which is deeper than
mere curiosity. He wants to know how these things work,
and how they were invented. The man is so absorbed in
the present that he cares little for the past. Not so with
the boy. He cares for the history of inventions, and in
this he is wiser than the man, for it is only by a study of
its origin and growth that we can understand the larger
significance of a great invention.

Great inventions have their origin in great discoveries.
The story of great inventions, therefore, includes the story
of the discoveries out of which they have arisen. The
stories of the discoveries and the inventions are inseparable
from the lives of the men who made them, and so we must
deal with biography, which in itself is of interest to the
boy. Such a story is the story of physical science in the
service of humanity.

The interest of the youth in great inventions is unques-
tioned. Shall we stifle this interest by overemphasis of

INTRODUCTORY NOTE

technical detail, or shall we minister to it as a thing vital
in the life of the youth of to-day ?

A few sentences quoted from G. Stanley Hall will indi-
cate the author's point of view. "The youth is in the
humanist stage. Nature is sentiment before it becomes
idea or formula or utility." "The heroes and history
epochs of each branch [of science] add another needed
quality to the still so largely humanistic stage." "A new
discovery, besides its technical record, involves the added
duty of concise and lucid popular statement as a tribute
to youth." The need of a "concise and lucid popular
statement" of the rise of the great inventions which
form the material basis of our modern civilization and
all of which are new to the young mind, has no doubt
been keenly felt by others as it has been by the author.
The story of our great inventions has been told in sundry
volumes for adult readers, but nowhere has this story, alive
with human interest, been told in a form suited to the
young. It was the realization of this need growing out of
years of experience in teaching these branches that led the
author to attempt the task of writing the story.

The purpose of this book is to tell in simple language
how our great inventions came into being, to depict the life-
struggles of the men who made them, and, in the telling- of
the story, to explain the working of the inventions in a
way the boy can understand. The stories which are here
woven together present the great epochs in the history of
physics, and are intended to give to the young reader a
connected view of the way in which our great inventions
have arisen out of scientific discovery on the one hand, and

xii

INTRODUCTORY NOTE

conditions which we may call social and economic on the other
hand. If the book shall appeal to young readers, and lead
them to an appreciation of the meaning of a great inven-
tion, the author will feel that his purpose has been achieved.

The author is deeply indebted to Dr. Charles A. McMurry
and Prof. Newell D. Gilbert, of the Northern Illinois State
Normal School; Profs. C. R. Mann and R. A. Millikan, of
the University of Chicago; and Prof. John F. Woodhull, of
Columbia University, for reading the manuscript and offer-
ing valuable suggestions. Acknowledgment is further
made here of valuable aid in collecting material for illus-
trations and letter-press. Such acknowledgment is due
to Prof. A. Gray, University of Glasgow; Prof. Antonio
Favaro, Royal University of Padua; Prof. A. Zammarchi,
Brescia, Italy; Mr. Nikola Tesla; the Royal Institution,
London; McC lure's Magazine; The Technical World Maga-
zine; The Scientific American; the Ellsworth Company;
Commonwealth-Edison Company; Association of Edison
Illuminating Companies; Electric Controller and Supply
Company; Kelley-Koett Manufacturing Company; Watson-
Stillman Company ; Gould Storage Battery Company ; Thor-
darson Electric Company ; the Westinghouse Machine Com-
pany; Marconi Wireless Telegraph Company of America,
and the Siemens-Schuckert Werke, Berlin.

The drawings illustrating Faraday's experiments are
from exact reproductions of Faraday's apparatus, made
by Mr. Joseph G. Branch, author of Conversations on Elec-
tricity, and are reproduced by his kind permission.

E. E. B.

CHICAGO, June, 1910.

THE
STORY OF GREAT INVENTIONS

Chapter I

THE AGE OF ARCHIMEDES

Archimedes, the First Great Inventor

ARCHIMEDES, the first great inventor, lived in Syracuse
/i more than two thousand years ago. Syracuse was a
Greek city on the island of Sicily. The King of Syracuse,
Hiero, took great interest in the discoveries of Archimedes.
One day Archimedes said to King Hiero that with his own
strength he could move any weight whatever. He even
said that, if there were another earth to which he could go,
he could move this earth wherever he pleased. The King,
full of wonder, begged of him to prove the truth of his state-
ment by moving some very heavy weight. Whereupon
Archimedes caused one of the King's galleys to be drawn
ashore. This required many hands and much labor. Hav-
ing manned the ship and put on board her usual loading, he
placed himself at a distance and easily moved with his hand
the end of a machine which consisted of a variety of ropes

r: OF GREAT INVENTIONS

and pulleys, drawing the ship over the sand in as smooth
and gentle a manner as if she had been under sail. The
King, quite astonished, prevailed with Archimedes to make
for him all manner of machines which could be used either
for attack or defence in a siege.

The Battle of Syracuse

During the life of King Hiero Syracuse had no occasion
to use the war machines of Archimedes. The grandson of
King Hiero, who succeeded to the throne, was a tyrant. He
attempted to throw off the sovereignty of Rome and en-
tered into an alliance with Carthage. His cruelty toward
his own people was so great that, after a short reign, he was
assassinated. There was anarchy in Syracuse for a time,
the Roman and anti-Roman parties striving for supremacy.
The anti-Roman party gaining possession of the city, the
Romans, in order to bring Syracuse again into subjection,
prepared for an attack by sea and land. Then it was that
Syracuse had need of the war machines made by Archimedes
(Fig. i).

The Romans came with a large land force and a fleet.
They were sure that within five days they could conquer the
city. But there are times when one man with brains is
worth more than an army. In the battle which followed,
Archimedes with his inventions was more than a match for
the Romans.

The city was strong from the fact that the wall on one side
lay along a chain of hills with overhanging brows ; on the
other side the wall had its foundation close down by the sea.

FIG. I THE BATTLE OF SYRACUSE

The city defended by the inventions of Archimedes.

THE STORY OF GREAT INVENTIONS

A fleet of sixty ships commanded by Marcellus bore down
upon the city. The ships were full of men armed with bows
and slings and javelins with which to dislodge the men who
fought on the battlements. Eight ships had been fastened
together in pairs. These double vessels were rowed by the
outer oars of each of the pair. On each pair of ships was a
ladder four feet wide and of a height to reach to the top of
the wall. Each side of the ladder was protected by a railing,
and a small roof-like covering, called a penthouse, was fast-
ened to the upper end of the ladder. This covering served
to protect the soldiers until they could reach the top of the
wall. They thought to bring these double ships close to
shore, raise the ladders by ropes and pulleys until they rest-
ed against the wall, then scale the wall and capture the city.

But Archimedes had crossbows ready, and, when the ships
were still at some distance, he shot stones and darts at the
enemy, wounding and greatly annoying them. When these
began to carry over their heads, he used smaller crossbows of
shorter range, so that stones and darts fell constantly in their
midst. By this means he checked their advance, and finally
Marcellus, in despair, was obliged to bring up his ships under
cover of night. But when they had come close to land, and
so too near to be hit by the crossbows, they found that
Archimedes had another contrivance ready. He had pierced
the wall as high as a man's head with many loopholes which
on the outside were about as big as the palm of the hand.
Inside the wall he had stationed archers and men with cross-
bows to shoot down the marines. By these means he not
only baffled the enemy, but killed the greater number of
them. When they tried to use their ladders, they discovered

THE AGE OF ARCHIMEDES

that he had cranes ready all along the walls, not visible at
other times but which suddenly reared themselves above the
wall from the inside and stretched their beams far over the
battlements, some of them carrying stones weighing about
five hundred pounds, and others great masses of lead. So,
whenever the ships came near, these beams swung round on
their pivots and by means of a rope running through a
pulley dropped the stones upon the ships. The result was
that they not only smashed the ships to pieces, but killed
many of the soldiers on board.

Another machine made by Archimedes was an "iron
hand" or grappling-hook swung on a chain and carried by a
crane. The hook was dropped on the prow of a ship, and
when it had taken hold the ship was lifted until it stood on
its stern, then quickly dropped, causing it either to sink or
ship a great quantity of water.

With such machines, unknown before, Archimedes drove
back the enemy. On the landward side similar machines
were used. The Romans were reduced to such a state of
terror that ' ' if they saw but a rope or a stick put over the
walls they cried out that Archimedes was levelling some
machine at them and turned their backs and fled."

After a long siege, however, hunger forced the Syracusans
to surrender. Marcellus so admired the genius of Archi-
medes that he gave orders that he should not be injured.
Yet, in the sack of the city which followed, Archimedes was
slain by a Roman soldier.

The Roman historian Livy records that "Archimedes,
while intent on some figures which he had made in the dust,
although the confusion was as great as could possibly be,

THE STORY OF GREAT INVENTIONS

was put to death by a soldier who did not know who he was ;
that Marcellus was greatly grieved at this, and that pains
were taken about his funeral, while his relations also were
carefully sought and received honor and protection on ac-
count of his name and memory."

Archimedes* Principle

Hiero, when he became King of Syracuse, decreed that a
crown of gold, of great value, should be placed in a certain
temple as an offering to the gods, and sent to a manufacturer
the correct weight of gold. In due time the crown was
brought to the King, and a beautiful piece of work it was.
The weight of the crown was the same as that of the gold,
but a report was circulated that some of the gold had been
taken out and silver supplied in its place. Hiero was angry,
but knew no method by which the theft might be detected.
He therefore requested Archimedes to give the matter his
attention.

While trying to solve this problem Archimedes went one
day to a bath. As he got into the bath-tub he saw that as
his body became immersed the water ran out of the tub.
He quickly saw how he could solve the problem, leaped out
of the bath in joy, and, running home naked, cried out with
a loud voice "Eureka! eureka!" (I have found it! I have
found it!)

Using a piece of gold and a piece of silver, each equal in
weight to the crown, and a large vase full of water, he
proved that the crown was not pure gold, and found how
much silver had been mixed with the gold.

The incident of the golden crown may have been the

THE AGE OF ARCHIMEDES

starting-point of Archimedes' study of solid bodies when
immersed in fluids. Every one knows that a boy can lift
a heavy stone under water that he could not lift out of
water. The stone seems lighter when in the water. A diver
with his lead-soled shoes could scarcely walk on land, but
walks easily under water. When the diver comes up, the
place where he was immediately becomes filled with water.
Now, whatever that water weighs which fills the diver's
place, just that much weight will the diver lose when he goes
dowrn. What is true of the diver is true of the stone or of
any object under water. The stone when in the water loses
just as much weight as the weight of the water that would
fill its place. This is the fact which was discovered by
Archimedes and which is called "Archimedes' Principle."

It is said by an ancient author that Archimedes invented
more than forty machines. Of these the best known are
the block and tackle, the endless screw (worm gear), and the
water snail, or Archimedean screw. Yet his delight was not
in his machines, but in his mathematics. Though he had
invented machines to please his king, he regarded such work
as trifling, and took little interest in the common needs of
life.

Inventions of the Ancient Greeks

The common needs of life are to-day the chief concern of
the greatest men, and so we find it hard to sympathize with
this view of Archimedes. His view, however, was that of
other learned men of his time, that the common needs of
life are beneath the dignity of the scholar, and so we can see
why the Greeks made so few great inventions.

THE STORY OF GREAT INVENTIONS

Hero, who lived a century later than Archimedes, invented
a steam-engine, which, however, was only a toy. A water-
clock, in which the first cog-wheels were used, was invented
by another Greek named Ktesibus, who also invented the
force-pump. The suction-pump was known in the time of
Aristotle, who lived about a century before the time of
Archimedes, but the inventor is unknown.

Concerning electricity, the Greeks knew very little. They
knew that amber when rubbed will attract light objects,
such as dust or chaff. Amber was called by the Greeks
"electron," because it reflected the brightness of the sun-
light, and their name for the sun was "Elector." From the
Greek name for amber we get our word "electricity."

The Greeks possessed scarcely more knowledge of magnets
than of electricity. In fact, their ideas of magnets cannot
be called knowledge, for they consisted chiefly of legends.

They told of the shepherd Magnes, who, while watching
his flock on Mount Ida, suddenly found the iron ferrule of
his staff and the nails of his shoes adhering to a stone; that,
later, this stone was called, after him, the "Magnes stone,"
or "Magnet."

They told impossible stories of iron statues being sus-
pended in the air by means of magnets, and of ships sailing
near the magnetic mountains when every nail and piece of
iron in the ship would fly to the mountain, leaving the ship
a wreck upon the waves.

Chapter II

THE AGE OF GALILEO

Galileo and the Battle for Truth

FOR eighteen centuries after the time of Archimedes
no inventions of importance were made. Men sought
for truth where truth could not be found. They looked
within their mouldy manuscripts and asked, ''What do the
great philosophers say ought to happen?" instead of look-
ing at nature and asking, "What does happen ?" And when
a man arose who dared to doubt the authority of the old
masters and turn to nature to find out the truth, all the
weapons at the command of the old school were hurled
against him.

Let us, at this distance, blame neither the one side nor
the other. The conflict was inevitable. It was an acci-
dent of history that the brunt of the attack fell upon a
man born in Italy in 1564, and that the battle was fought
chiefly in the "Eternal City," from which centuries before
had marched the legions that conquered the world.

The boy, Galileo, who was to become the central figure
of the great conflict, was talented in many ways. In lute-
playing his skill excelled that of his father, who was one of
the noted musicians of his day. His skill in drawing was

THE STORY OF GREAT INVENTIONS

such that noted artists submitted their work to him for
criticism. He wrote essays on the works of Dante and
other classical writers. He amused his boy companions by
constructing toy machines which, though ingenious, did not
always work.

His preference was for mechanics, but, as this subject
offered little prospect of profitable work, he took up the
study of medicine in accordance with his father's wishes.

In his eighteenth year he entered the University of Pisa.
Here he found men who refused to think for themselves,
but decided every question by referring to what the ancient
philosophers said. Galileo could not endure such slavish
submission to authority. So strongly did he assert himself
that he was nicknamed "The Wrangler," and, by his wrang-
ling, he lost a scholarship in the university.

He neglected his medical studies and secretly studied
mathematics. His father, learning of this, consented to his
becoming a mathematician. Thus he followed his bent,
though it seemed to lead directly to poverty.

The Pendulum Clock

It was while a student at the University of Pisa that
he discovered a law of pendulums which makes possible
our pendulum clocks. While at his devotions in the cathe-
dral, he observed the swinging of the bronze lamp which
had been drawn back for lighting. Timing its swinging by
means of his pulse, the only timepiece in his possession, he
found that the time of one swing remained the same, though
the length of the swing grew smaller and smaller. This

FIG. 2 — GALILEO'S PENDULUM CLOCK
It had only one hand, which is not shown in the picture.

THE STORY OF GREAT INVENTIONS

discovery led to his invention of an instrument for physi-
cians' use in timing the pulse. About fifty years later he
invented the pendulum clock (Fig. 2).

Lack of funds compelled him to leave the university with-
out completing his course. He returned to the parental
roof and continued his scientific studies. The writings of
Archimedes were his favorite study. With Archimedes'
famous experiment on King Hiero's crown as a starting-
point, he discovered the laws of floating bodies, which ex-
plain why a ship or other object floats on water, and in-
vented a balance for weighing objects in water.

But such employment won nothing more substantial than
honor and fame. Food and clothing were needed. For
two years he strove without success to secure employment.
At the end of that time he was appointed professor of mathe-
matics in the University of Pisa at the magnificent salary
of sixty scudi (about sixty-three dollars) per year. "But
any port in a storm; and in Galileo's needy circumstances
even this wretched salary was not to be rejected." More-
over, he could add somewhat to his income by private
tutoring.

Galileo's Experiment with Falling Shot

While teaching at the University of Pisa, he performed
his famous experiment of dropping from the top of the
leaning tower two shot, one weighing ten pounds, the other
one pound. Now, according to Aristotle, the ten-pound
shot should fall in one-tenth the time required by the one-
pound shot. But the assembled company of professors and
students saw the two shot start together, fall together, and

THE AGE OF GALILEO

strike the ground at the same instant, and still refused to
believe their own eyes. They continued to affirm that a
weight of ten pounds would reach the ground in a tenth of
the time taken by a one-pound weight, because they were
able to quote chapter and verse in which Aristotle assured
them that such is the fact. Thus Galileo made enemies of
the other professors, but for a time they could do nothing
more than annoy him.

About this time Galileo incurred the wrath of the Grand
Duke of Tuscany, from whom he had received his appoint-
ment. He was commissioned to examine a machine in-
vented by a nephew of the Grand Duke for the purpose of
cleaning harbors. Galileo plainly said that the machine
was worthless. It was tried, and his opinion proved true.
But like the kings of olden time who killed the bearer of
evil tidings even though the tidings were true, his enemies
made his position so unpleasant that he resigned.

He had neither employment nor money. His father's
death occurring about this time, threw upon him the care
of a mother, a worthless brother, and two sisters. In his
distress he sought help from a friend, and secured an ap-
pointment as professor of mathematics in the University of
Padua . His salary was one hundred and eighty florins (about
ninety-five dollars), while other professors received more
than ten times as much.

While at Padua, Galileo was busy inventing. He in-
vented the sector, which is to be found in most cases of
mathematical instruments and is used in certain kinds of
drawing. He also invented an air thermometer (Fig. 3),
the first instrument for measuring temperature.

FIG. 3 AN AIR THERMOMETER

When the air in the bulb grows cooler it contracts, and the air outside
forces the water up the tube. When the air in the bulb grows warmer it
expands and forces the water down in the tube.

THE AGE OF GALILEO

In 1604 there appeared a new star of great brilliancy.
It continued to shine with varying brightness for eighteen
months, and then vanished. This was a strange event, and
Galileo made use of it. He proved that the new star must
lie among the most distant of the heavenly bodies, and this
fact did not agree with Aristotle's view that the heavens
are perfect, and therefore never change. A heated con-
troversy followed, and Galileo came out boldly in favor
of the theory that the earth revolves about the sun, the
prevailing notion then being that the earth does not
move, but that^the sun and other heavenly bodies revolve
around it.

The Telescope

In 1609 Galileo learned of a discovery that was to be of
great value to the world, but a source of untold trouble to
himself. An apprentice of a Dutch optician, while playing
with spectacle lenses, chanced to observe that if two of
the lenses were placed in a certain position objects seen
through them appeared much nearer. Galileo, learning of
this, set to work to construct a spy - glass, applying his
knowledge of light. In one day he had constructed such
an instrument, in which he used two lenses like the lenses
of the modern opera -glass. Thus, while the Dutchman's
discovery was by accident, Galileo's was by reasoning, and
was the more fruitful, as we shall see. %

Galileo continued improving his telescope until he had

made one which would magnify thirty times. He was the

first to apply the telescope to the study of the heavenly

bodies. The most startling of his discoveries was that of

2 15

THE STORY OF GREAT INVENTIONS

the moons of the planet Jupiter, which he called new
planets.

This aroused the fury of his enemies, who ridiculed the
idea of there being new planets; "for," they said, "to see
these planets they must first be put inside the telescope."
The excitement was intense. Poets chanted the praise of
Galileo. A public fete was held in his honor. One of his
pupils was imprisoned in the tower of San Marco, where
he had gone to make observations with his telescope, and
could not escape until the crowd had satisfied their curiosity.
Some of the philosophers refused to look lest they should
see and be convinced.

Galileo's Struggle

His enemies sought to steal from him the honor of his
discoveries. Some claimed to have made the discoveries
before Galileo did. Others claimed that his discoveries
were false, that their only use was to gratify Galileo's vanity
and thirst for gold. In these trying times the friendship of
the great astronomer Kepler warded off some of the most
exasperating attacks.

Galileo's fame spread throughout Europe. Students came
in great numbers, so that he had little leisure left for his
own studies. He therefore decided to leave Padua, and
secured an appointment as mathematician and philosopher
to the Grand Duke of Tuscany. This appointment took
him to Florence. It was here that an incident occurred
that marked the beginning of a persecution which continued
to the end of his life.

As we read the story of this conflict let us remember that

THE AGE OF GALILEO

it was not primarily a conflict between the Roman Catholic
Church and Galileo. It was a conflict of principles. On
the one side were arrayed those who said that men should
always believe as the ancient writers did; on the other,
those who said men should think for themselves. In the
first party were most of the university professors and others
who dreaded the introduction of new beliefs, whether in
religion or science. In the second party were Galileo and
a small band of devoted followers.

At a dinner at the table of the Grand Duke in Pisa the
conversation turned on the moons of Jupiter. Some praised
Galileo. Others condemned him, saying that the Holy
Scriptures were opposed to his theory of the motion of the
earth. A friend reported the incident to Galileo, and he
replied to the arguments of his opponents in a letter which
was made public. No doubt the sting of his sarcasm made
his enemies more bitter. He admitted that the Scriptures
cannot lie or err, but this, he said, does not hold good of
those who attempt to explain the Scriptures. In another
letter, he quoted with approval a saying of Cardinal Ba-
ronius, "The Holy Spirit intended to teach us in the Bible
how to go to Heaven, not how the heavens go."

The first shot had been fired. The battle was on, and
the Church, because it possessed the most powerful weap-
ons of attack, was used by the combined forces to break
the power of Galileo's reasoning. He went to Rome to
make his defence, but was commanded by the Holy Office
not to hold or teach that the sun is immovable, and that
the earth moves about the sun.

During another visit to Rome there was shown to Galileo

THE STORY OF GREAT INVENTIONS

an instrument which, it was said, would show a flea as large
as a cricket. Galileo recalled that some years before he
had so arranged a telescope that he had seen flies which he
said looked as big as a lamb, and were covered all over with
hair. This was the first microscope. Galileo quickly im-
proved the instrument, and soon his microscopes were in
great demand.

In violation of the decree of the Church, to which he had
submitted, he published his most famous work in which
he defended the theory that the earth moves about the
sun. The book was the outcome of his life-work, but the
Church believed it dangerous. He was summoned to
Rome. Confined to a sick-bed, he pleaded for delay, which
was granted. Before he recovered, however, the summons
was made imperative. He must go to Rome, or be carried
in irons. He went in a litter, carried by servants of the
Grand Duke. In Rome he was to appear before the In-
quisition. There he was treated with a consideration never
before accorded to a prisoner of the Inquisition. Nor was
he subjected to torture, as has been stated by some. He
was found guilty of teaching the doctrine that the sun does
not move, and that the earth moves about the sun. He
was compelled to recant, and sentenced to the prison of
the Holy Office and, by way of penance, to repeat once a
week for three years the seven penitential Psalms.

He yielded without reserve to the decree of the Inquisi-
tion, renounced his "errors and heresies," and, with his
hand on the Bible, took oath never again to teach the for-
bidden doctrine.

And now, though a shattered old man of seventy-four,

THE AGE OF GALILEO

enjoined to silence on the chief results of his life- work,
nothing could quench his devotion to science. In these
last years, he published a new book which, with his earlier
work, entitles him to be regarded as the founder of the
science of mechanics.

In his study of machines Galileo found that no machine
will do work of itself. Whenever a machine is at work, a
man or a horse, or some other power, is at work upon the
machine. In no case will a machine do work without re-
ceiving an equal amount of work.

Torricelli and the Barometer

Galileo had a pump which he found
would not work when the water was
thirty-five feet below the valve. He
thought the pump was injured, and
sent for the maker. The maker as-
sured him that no pump would do
better. This led Torricelli, one of
Galileo's pupils, to the discovery of
the barometer. Men had said that
water rises in a pump because nature
abhors a vacuum. Torricelli believed
that air-pressure and not nature's
"horror of a vacuum" is the cause
of water rising in a pump. He in-
vented the barometer to measure air-
pressure.

The first barometer was a glass tube filled with quick-
silver or mercury (Fig. 4). The tube was closed at the

FIG. 4 TORRICELLI S

EXPERIMENT

THE STORY OF GREAT INVENTIONS

upper end, and the lower end, which was open, dipped in
a dish of mercury. He allowed the tube to stand, and saw
that the height of the mercury changed. This he believed
was because the air-pressure changed. Wind, Torricelli
said, is caused by a difference of air-pressure, which is due
to unequal heating of the air. For this reason a cool breeze
blows from the mountain top to the heated valley, or from
sea to land on a summer day.

Otto Von Guericke and the Air-Pump

About this time a German burgomaster, Otto von Guericke,
of Magdeburg, was performing experiments on air-pressure.
The Thirty Years' War had been raging for thirteen years.
The Swedish King, Gustavus Adolphus, had landed in Ger-
many, and was winning victory after victory over the im-
perial troops. Magdeburg had entered into an alliance with
the Swedish King, by which he was granted free passage
through the city, while, on the other hand, he promised pro-
tection to the city.

The imperial army under Tilly and Pappenheim laid siege
to the city. On the one side there was hope that Gustavus
would arrive in time to effect a rescue; on the other, a de-
termination to conquer before such aid could arrive. While
Gustavus was on his way to the rescue, Magdeburg was
taken by storm, and the most horrible scene of the Thirty
Years' War was enacted. Tilly gave up the city to plunder,
and his soldiers without mercy killed men, women, and
children. In the midst of the scene of carnage the city was
set on fire, and soon the horrors of fire were added to the

THE AGE OF GALILEO

horrors of the sword. In less than twelve hours twenty
thousand people perished.

Guericke 's house and family were saved, but the suffer-
ings of the city were not yet ended. In five years the enemy
was again before the walls, and Magdeburg, then in the
possession of the Swedes, was compelled to yield to the
combined Saxon and imperial troops. Guericke entered the
service of Saxony, and was again made mayor of the city.

In the midst of these scenes of war, he found time to con-
tinue his studies. He made the first air-pump, and with it
performed experiments which led to some very important
results.

The experiments which Guericke made with his air-pump
aroused the attention of the princes, and especially Emperor
Ferdinand. Guericke was called to perform his experi-
ments before the Emperor. The most striking of these
experiments he performed with two hollow copper hemi-
spheres about a foot in diameter, fitted closely together.
When the air was pumped out, sixteen horses were barely
able to pull the hemispheres apart, though, when air was
admitted, they fell apart of their own weight.

Another experiment which astonished his audience was
performed with the cylinder of a large pump (Fig. 5). A
rope was tied to the piston. This rope was passed over a
pulley, and a large number of men applied their strength
to the rope to hold the piston in place. When the air was
taken out of the cylinder, the piston was forced down by
air-pressure, and the men were lifted violently from the
ground. This experiment, as we shall see, was of great im-
portance in the invention of the steam-engine.

FIG. 5 — GUERICKE'S AIR-PUMP
Men lifted from the ground by air-pressure.

THE AGE OF GALILEO

Guericke's study of air-pressure led him to make a water
barometer (Fig. 6). 'This consisted of a glass tube about
thirty feet long dipping into a dish of water. The tube was
filled with water, and the top projected above the roof of
the house. On the water in the tube he placed a wooden
image of a man. In fair weather the image would be seen
above the housetop. On the approach of a storm the
image would drop out of sight. This led his superstitious
neighbors to accuse him of being in league with Satan.

The first electrical machine was made by Guericke. This
was simply a globe of sulphur turning on a wooden axle.
He observed that when the dry hand was held against the
revolving globe, the globe would attract bits of paper and
other light objects.

Robert Boyle and the Pressure of Air and Steam

Robert Boyle, in England, improved the air-pump and
performed many new and interesting experiments with it.
One of his experiments was to make water boil by means
of an air-pump without applying heat. It is now well
known that water when boiling on a high mountain is not
so hot as when boiling down in the valley. This is because
the air-pressure is less on the mountain top than in the val-
ley. By using an air-pump to remove the air-pressure, water
may be made to boil when it is still quite cold to the hand.

Boyle compared the action of air under pressure to a
steel spring. The ''spring" of the air is evident to us in
the pneumatic tire of the bicycle or automobile. Boyle
found that the more air is compressed the greater is its
pressure or "spring,'* and that steam as it expands exerts

FIG. 6 — GUERICKE'S WATER BAROMETER

In fair weather the image appeared above the housetop. When a
storm was approaching the image dropped below the roof into the
house,

THE AGE OF GALILEO

less and less pressure. This is important in the steam-
engine.

Pascal and the Hydraulic Press

It was Blaise Pascal, a Frenchman, who proved beyond
the possibility of a doubt that air-pressure supports the mer-
cury in a barometer, and
lifts the water in a pump
(Fig. 7). He had two mer-
cury barometers exactly
alike set up at the foot of
a mountain. The mercury
stood at the same height in
each. Then one barometer
was left at the foot of the
mountain, and the other
was carried to the summit,
about three thousand feet
high. The mercury in the
second barometer then stood
more than three inches low-
er than at first. As the
barometer was carried down
the mountain the mercury
slowly rose until, at the
foot, it stood at the same
height as at first. The par- FIG. 7— A LIFT-PUMP

-, ! , -i ir Air pressing down on the water in

ty stopped about half-way the wjj cause* the water to rise in the

down the mountain, allow- pump. The air can do this only when

incr the barometer to rest the PlunSer is at work removing air or

J water and reducing the pressure inside

there for some time, and the pump.

THE STORY OF GREAT INVENTIONS

observing it carefully. They found that the mercury stood
about an inch and a half higher than at the foot of the moun-
tain. During all this time the height of the mercury in the
barometer which had been left at the foot of the mountain
did not change.

It is now known that when a barometer is carried up to
a height of nine hundred feet, the mercury stands an inch
lower than at the earth's surface. For every nine hundred
feet of elevation the mercury is lowered about one inch.
In this way the height of a mountain can be measured, and
a man in a balloon or an air-ship can tell at what height he
is sailing. For this purpose, however, a barometer is used
that is more easily carried than a mercury barometer.

Pascal invented the hy-
draulic press, a machine
with which he said he could
multiply pressure to any
extent, which reminds us
of Archimedes' saying that,
with his own hand, he could
move the earth if only he
had a place to stand. Pas-
cal could so arrange his

lib

FIG. 8 A SIMPLE HYDRAULIC PRESS

A one -pound weight holds up a
hundred pounds.

machine that a man press-
ing with a force of a hun-
dred pounds on the handle

could produce a pressure of many tons. In fact, a man can
so arrange this machine that he can lift any weight what-
ever (Fig. 8).

The hydraulic press has two cylinders. One cylinder

THE AGE OF GALILEO

must be larger than the other. The two cylinders are filled
with a liquid, as water or oil, and are connected by a tube
so that the liquid can flow from one cylinder into the other.
There is a tightly fitting piston in each cylinder. If one
piston has an area of one square inch, and the other has an
area of one hundred square inches, then every pound of
pressure on the small piston causes a hundred pounds of
pressure on the large piston. A hundred pounds on the
small piston would lift a weight of ten thousand pounds on
the large piston. But we can see that the large piston can-
not move as fast as the small one does. Though we can
lift a very heavy weight with this machine, we must ex-
pect this heavy weight to move slowly. There must be a
loss in speed to make up for the gain in the weight lifted
(Fig. 9). An hydraulic press with belt -driven pump is
illustrated in Fig. 10.

Newton

Sir Isaac Newton as a boy did not show any unusual
talent. In school he was backward and inattentive for a
number of years, until one day the boy above him in class
gave him a kick in the stomach. This roused him and, to
avenge the insult, he applied himself to study and quickly
passed above his offending classmate. His strong spirit
was aroused, and he soon took up his position at the head
of his class.

It was his delight to invent amusements for his class-
mates. He made paper kites, and carefully thought out
the best shape for a kite and the number of points to which
to attach the string. He would attach paper lanterns to

THE STORY OF GREAT INVENTIONS

FIG. 9 HOW AN HYDRAULIC PRESS WORKS

One man with the machine can exert as much pressure as a hundred
men could without the machine. The arrows show the direction in
which the liquid is forced by the action of the plunger p. The large
piston P is forced up, thus compressing the paper.

these kites and fly them on dark nights, to the delight of
his companions and the dismay of the superstitious country
people, who mistook them for comets portending some great
calamity. He made a toy mill to be run by a mouse, which
he called the miller; a mechanical carriage, run by a handle

THE AGE OF GALILEO

worked by the person inside, a water-clock, the hand of
which was turned by a piece of wood which fell or rose by
the action of dropping water.

At the age of fifteen, his mother, then a widow, removed
him from school to take charge of the family estate. But
the farm was not to his liking. The sheep went astray,

FIG. IO AN HYDRAULIC PRESS WITH BELT-DRIVEN

PUMP

THE STORY OF GREAT INVENTIONS

and the cattle trod down the corn while he was perusing
a book or working with some machine of his own con-
struction. His mother wisely permitted him to return to
school. After completing the course in the village school
he entered Trinity College, Cambridge.

Gravitation

It was in the year following his graduation from Cam-
bridge that he made his greatest discovery — that of the law
of gravitation. A plague had broken out in Cambridge,
to escape which Newton had retired to his estate at Wools-
thorpe. Here he was sitting one day alone in the garden
thinking of the wonderful power which causes all bodies to
fall toward the earth. The same power, he thought, which
causes an apple to fall to the ground causes bodies to fall
on the tops of the highest mountains and in the deepest
mines. May it not extend farther than the tops of the
mountains? May it not extend even as far as the moon?
And, if it does, is not this power alone able to hold the
moon in its orbit, as it bends into a curve a stone thrown
from the hand?

There followed a long calculation requiring years to com-
plete. Seeing that the results were likely to prove his
theory of gravitation, he was so overcome that he could
not finish the work. When this was done by one of his
friends, it was found that Newton's thought was correct —
that the force of gravitation which causes bodies to fall .at
the earth's surface is the same as the force which holds the
moon in its orbit. As the earth and moon attract each

THE AGE OF GALILEO

other, so every star and planet attracts every other star
and planet, and this attraction is gravitation.

Colors in Sunlight

About the same time that he made his first discoveries
regarding gravitation, he took up the study of light with a
view to improving the construction of telescopes. His first
experiment was to admit sunlight into a darkened room
through a circular hole in the shutter, and allow this beam
of light to pass through a glass prism to a white screen be-
yond. He expected to see a round spot of light, but to
his surprise the light was drawn out into a band of brilliant
colors.

He found that the light which comes from the sun is not
a simple thing, but is composed of colors, and these colors
were separated by the glass prism. In the same way the
colors of sunlight are separated by raindrops to form a rain-
bow. The colors may be again mingled together by passing
them through a second prism. They will then form a white
light.

Suppose that the light of the sun were not composed of
different colors, that all parts of white light were alike,
then there would be no colors in nature. All the trees and
flowers would have a dull, leaden hue, and the human
countenance would have the appearance of a pencil-sketch
or a photographic picture. The rainbow itself would
dwindle into a narrow arch of white light; the sun would
shine through a gray sky, and the beauty of the setting
sun would be replaced by the gray of twilight (Fig. n).

3 31

THE STORY OF GREAT INVENTIONS

FIG. ii — NEWTON'S EXPERIMENT WITH THE PRISM

Sunlight separated into the colors of the rainbow. The seven colors
are: violet, indigo, blue, green, yellow, orange, red.

One of Newton's inventions was a reflecting telescope —
that is, a telescope in which a curved mirror was used in
place of a lens. He made such a telescope only six inches
long, which would magnify forty times.

Newton was a member of the Convention Parliament,
which declared James II. to be no longer King of England
and tendered the crown to William and Mary. He was
made a knight by Queen Anne in 1705.

His knowledge of chemistry was used in the service of
his country when he was Master of the Mint. It was his
duty to superintend the recoining of the money of England,
which had been debased by dishonest officials at the mint.
He did his work without fear or favor.

Once a bribe of £6000 ($30,000) was offered him. He

THE AGE OF GALILEO

refused it, whereupon the agent who made the offer said to
him that it came from a great duchess. Newton replied:
" Tell the lady that if she were here herself, and had made
me this offer, I would have desired her to go out of my
house; and so I desire you, or you shall be turned out."

Although Newton's discoveries in the world of thought
were among the greatest ever made by man, he regarded
them as insignificant compared with the truth yet undis-
covered. He said of himself: "I do not know what I may
appear to the world, but to myself I seem to have been
only like a boy playing on the sea-shore and diverting
myself in now and then finding a smoother pebble or a
prettier shell than the ordinary, whilst the great ocean of
truth lay all undiscovered before me."

Chapter III

THE EIGHTEENTH CENTURY

James Watt and the Steam-Engine

IF you had visited the coal-mines of England and Scot-
land three hundred years ago, you might have seen
women bending under baskets of coal toiling up spiral
stairways leading from the depths of the mines. At some
of the mines horses were used. A combination of windlass
and pulleys made it possible for a horse to lift a heavy
bucket of coal. There came a time, however, when slow
and crude methods such as these could not supply the coal
as fast as it was needed. The shallower mines were being
exhausted. The mines must be dug deeper. The demand
for coal was increasing. The supply of coal, it was thought,
would not last until the end of the century. The wood
supply was already exhausted. It seemed that England
was facing a fuel famine.

There was only one way out of the difficulty. A machine
must be invented that would do the work of the women
and horses, a machine strong enough to raise coal with
speed from the deepest mines. Then it happened that two
great inventors, Newcomen and Watt, arose to produce the
machine that was needed. When the world needs an in-

THE EIGHTEENTH CENTURY

vention it seldom fails to appear. It is true of the world,
as of an individual, that "Necessity is the mother of in-
vention."

In the mean time Torricelli had performed his famous
barometer experiment, and Otto von Guericke had aston-
ished princes with proofs of the pressure of the air. There
was no apparent connection between these experiments
and the art of coal-mining, yet these discoveries made pos-
sible the steam-engine which was to revolutionize first the
coal-mining industry and, later, the entire industrial world.

The First Steam-Engine with a Piston

The first steam-engine with a piston was made by Denys
Papin, a Frenchman. Papin had observed that, in Guer-
icke 's experiment, air-pressure lifted several men off their
feet. So he thought the air could be made to lift heavy
weights and do useful work. But how should he produce
the vacuum ? His first thought was to explode gunpowder
beneath the piston. The gunpowder engine had been tried
by others and found wanting. He next turned his atten-
tion to steam, and discovered that if the piston were forced
up by steam and then the steam condensed, a vacuum was
formed beneath the piston, and air-pressure forced the pis--
ton to descend. If the piston were attached to a weight
by a rope passing over a pulley, then, as the piston de-
scended, it would lift the weight. Papin' s engine consisted
simply of a cylinder and piston (Fig. 12). There was no
boiler, but the water was placed in the cylinder beneath
the piston. A fire was placed under the cylinder and, as

THE STORY OF GREAT INVENTIONS

the water boiled, the steam raised the piston. Then the
fire was removed and, as the cylinder cooled, the steam
condensed, and the piston was forced down by air-pressure.

This was a slow and awk-
ward method. The engine
required several minutes to
make one stroke.

The principle of Papin's
engine was first success-
fully applied by Thomas
Newcomen. Newcomenwas
a blacksmith by trade, and
his great successor, Watt,
was a mechanic. Thus we
see that great discoveries
soon become common prop-
erty. The blacksmith and
the mechanic soon learn to
use the discoveries of the
scientist.

Newcomen's Engine

FIG. 12 PAPIN S ENGINE

In the Newcomen engine
The first steam-engine with a pistori. the piston moved a Walk-
When the piston B was forced down

by air-pressure, a weight was lifted mg-beam to which Was at-
by means of a rope TT passing over tacheda pump-rod. Steam
pulleys. 1 !

was used merely to bal-
ance the air-pressure on the piston and allow the pump-
rod to descend by its own weight. The steam was con-

THE EIGHTEENTH CENTURY

densed in the cylinder, and the pressure of the air forced
the piston down. Thus the work of raising water in
the pump was done by the air. Newcomen's first engine
made twelve strokes a minute, and at each stroke lifted
fifty gallons of water fifty yards. He used this engine in
pumping water from the mines, and also made engines for
lifting coal.

At first the steam was condensed by throwing cold water
on the outside of the cylinder. But one day the engine
suddenly increased its speed and continued to work with
unusual rapidity. The upper side of the piston was cov-
ered with water to make the piston air-tight, and it was
found that this water was entering the cylinder through
a hole that had worn in the piston, and this jet of cold
water was rapidly condensing the steam. This was the
origin of ''jet condensation."

After this steam and water were alternately admitted to
the cylinder through cocks turned by hand. A boy, Hum-
phrey Potter, to whom this work was intrusted, won fame
by tying strings to the cocks in such a way that the engine
would turn the cocks itself and the boy, Humphrey, was
free to play. This device was the origin of valve-gear.1

Newcomen's engine was extensively used. The tin and
copper mines of Cornwall were deepened. Coal-mines were
sunk to twice the depth that had been possible. But as

1 Any device by which a steam-engine operates the valves which admit
steam to the cylinder is called " valve-gear." One form of valve-gear is
the link motion invented by Stephenson. This form will be described
in connection with the locomotive. A simple valve-rod, worked by an
eccentric such as is used on most stationary engines, is also a form of valve-
gear.

THE STORY OF GREAT INVENTIONS

the mines were deepened the cost of running the engines
increased. The largest engines consumed about $15,000
worth of coal per year. The Newcomen engine required
about twenty-eight pounds of coal per hour per horse-power,
while a modern engine consumes less than two pounds.
Again, because of increased cost, mines were being aban-
doned. Such was the situation when James Watt came
into the field of action.

Watt had learned the mechanic's trade in one year in a
London shop, and, because he had not passed through an
apprenticeship of seven years, the Guild of Hammermen, a
labor- union of his time, refused him admission, and this
refusal meant no employment. He found shelter, however,
in the University of Glasgow, and was there provided with
a small workshop where he could make instruments for
sale.

Watt's Engine

A small Newcomen engine belonging to the University of
Glasgow was out of repair. London mechanics had failed
to make it work. The job was given to Watt. That he
might do a perfect piece of work on this engine, he made
a study of all that was then known relating to steam
(Fig. 13).

He saw that there was a great loss of heat in admitting
cold water into the cylinder to condense the steam, and
that, to prevent this loss, the cylinder must be kept always
as hot as the steam that enters it. While thinking upon
this problem the idea came to him that, if connection were
made between the cylinder and a tank from which the air

FIG. 13 THE NEWCOMEN ENGINE, IN REPAIRING WHICH

WATT WAS LED TO HIS GREAT DISCOVERIES

Preserved in the University of Glasgow.

THE STORY OF GREAT INVENTIONS

had been pumped out, the steam would rush into the tank,
and might there be condensed without cooling the cylinder.
This was the origin of the condenser.

We have seen that, in the Newcomen engine, the steam
acted only on the under side of the piston, air acting on
the upper side. It occurred to Watt that the steam should
act on both sides of the piston. So he proposed to put an
air-tight cover on the cylinder with a hole and stuffing-box
for the piston to slide through and to admit steam to act
upon it instead of air. Thus he was led to invent the double-
acting engine. The action in the cylinder of Watt's engine
was the same as that of the modern engine.

To save the power of steam, Watt arranged the valve in
his engine in such a way that the steam was cut off from
the cylinder when the piston had made about one-fourth
of a stroke. The steam in the cylinder continues to ex-
pand and drive the piston. This device more than doubles
the amount of work that the steam will do (Fig. 14).

Horse-Power of an Engine

When horses were about to be replaced by the steam-
engine at the mines, the question was asked: "How many
horses will the engine replace ?" Tests were made by Watt
and others before him of the rate at which a horse could
work in pumping water or in lifting a weight by means of
a pulley. Watt's experiments showed that "a good Lon-
don horse could go on lifting 150 pounds over a pulley at
the rate of 2| miles an hour or 220 feet per minute, and
continue the work eight hours a day." This would be

THE EIGHTEENTH CENTURY

equal to lifting 33,000 pounds one foot high every minute.
This rate of doing work he called a horse-power. It is more
than the average horse can do, but this number was used by
Watt that he might give good measure in his engines. The
horse-power of an engine at that time meant the rate of

SLIDE VALVE

FIG. 14 CYLINDER OF WATT'S STEAM-ENGINE

Arrows show the course of the steam.

work in lifting water or coal. Now it means the rate of
work done by the steam upon the piston, so that to find
the useful horse-power of an engine we must deduct the
work wasted in friction.

The indicator for measuring the pressure of steam in the
cylinder and the fly-ball governor are also inventions made

THE STORY OF GREAT INVENTIONS

by Watt (Fig. 1 5) . The fly -ball governor replaced the throt-
tle-valve which was at first used by Watt to regulate the speed
of his engines. The throttle- valve is still used on locomotives.
At the end of the eighteenth century the steam-engine
was full grown. It remained for the nineteenth century to
apply the engine to locomotion on sea and land, to develop
the steam-turbine, and so to increase the power of the

FIG. 15 A FLY-BALL GOVERNOR

The balls as they rotate regulate the admission of steam
to the cylinder by means of the lever L and the rod R.

steam-engine that, early in the twentieth century, a 68,000-
horse-power engine should speed an ocean liner across the
Atlantic in five days.

THE EIGHTEENTH CENTURY

The Leydcn Jar

The first electrical invention of practical use was made
by Benjamin Franklin. In Franklin's time great interest
in electricity had been aroused by the strange discovery
of a German professor, Pieter van Musschenbroek, of the
University of Ley den. This professor had tried what he
called a new but terrible experiment. He had suspended
by two silk threads a gun-barrel which received electricity
from an electrical machine. From one end of the gun-barrel
hung a brass wire. The
lower end of this wire dip-
ped in a jar of water. He
held the jar in one hand,
while with the other he
tried to draw sparks from
the gun -barrel. Suddenly
he received a shock which
seemed to him like a light-
ning stroke. So violent was
the shock that he thought
for a moment it would end
his life.

Out of this experiment came the Leyden jar, which for a
century and a half was of no practical use, but which now
forms an important part of every wireless telegraph equip-
ment. The Leyden jar is simply a glass bottle or jar coated
with tin-foil both inside and outside (Fig. 16). When
charged with electricity the jar will hold its charge until
the two coatings are connected by a metal wire or other

FIG. l6 A LEYDEN JAR

THE STORY OF GREAT INVENTIONS

good conductor of electricity. A person may receive a strong
shock by holding the jar in one hand and touching a knob
connected to the inner coating with the other hand.

Popular interest in electricity was aroused by this dis-
covery. The friction electrical machine and the Ley den
jar were simple and easy to make. People of fashion found
them interesting and amusing, the more so because of the
shock felt on taking through the body the discharge from
the "wonderful bottle," and the fact that several persons
could receive the shock at the same instant. On one
occasion the Abbe Nollet discharged a Leyden jar through
a line composed of all the monks of the Carthusian Monastery
in Paris. As the line of serious-faced monks a mile in length
jumped into the air, the effect was ridiculous in the extreme.

Conductors and Insulators

About this time other great electrical discoveries were
made. Early in the century, Stephen Gray discovered
that some objects conduct electricity and others do not.
He discovered that, when a glass tube is electrified by
rubbing, it will attract and repel light objects. In the same
way a comb or penholder of rubber may be electrified
by rubbing it on the sleeve. A bit of paper which touches
the comb becomes electrified. Electricity can be trans-
ferred from one object to another. Gray discovered further
that contact is not necessary, that a hempen thread or a
wire will carry an electric charge from one object to an-
other. A silk thread will not carry the electric charge.
"Some things convey electricity," he said, "and some do

THE EIGHTEENTH CENTURY

not, and those which do not can be used to prevent the
electricity escaping from those which do." Could this ob-
scure inventor have seen a modern telegraph line with the
glass insulators on the poles, which prevent the electric
current escaping from the telegraph wire, he might have
realized the importance of his discovery. He set up a line
of hempen thread six hundred and fifty feet long, and with
an electrical machine at one end of the line electrified a
boy suspended from the other end.

Two Kinds of Electric Charge

A Frenchman, DuFay, while carrying further the experi-
ments of Gray, was watching a bit of gold-leaf floating in the
air. The gold-leaf had been repelled after contact with
his electrified glass tube. Thinking to try the act ion of
two electrified objects on the gold leaf, he rubbed a piece of
gum-copal and brought it near the leaf. To his astonish-
ment the leaf, which was repelled by the glass tube, was
attracted by the gum-copal. He repeated the experiment
again and again, and each time the leaf was repehed by the
glass and attracted by the gum. He concluded from this
that there are two kinds of electricity, which he named
"vitreous" and "resinous." The two kinds of electric
charge were called by Franklin "positive" and "negative."

Franklin made a battery of Ley den jars, connecting the
inner coating of one to the outer coating of the next through-
out the series. In this way he could get a much stronger
spark than with a single jar. On one occasion he nearly lost
his life by taking a shock from his battery of Ley den jars.

THE STORY OF GREAT INVENTIONS

He magnetized and demagnetized steel needles by passing
the discharge from his Leyden jars through the needles.

Franklin's Kite Experiment

The conjecture that lightning is of the same nature as the
spark from the Leyden jar or the electrical machine had
gained a hold on the minds of others before Franklin. In
France sparks had been drawn from a rod ninety-nine feet
high, but this did not reach into the clouds. Franklin de-
termined to send a kite into a thunder-cloud, thinking elec-
tricity from the cloud would follow the string of the kite
and could be stored in a Leyden jar, and used like the charge
from an electrical machine. He had felt the power of a
Ley den- jar discharge, and through it had nearly lost his
life. He knew that lightning is far more powerful than any
battery of Leyden jars, and yet to test the truth of his
theory, that lightning is an electrical discharge, he was
about to draw the lightning to his hand. He knew little of
conductors of electricity. Whether the cord would draw
little or much of the "electric fire" he knew not. So far as
he knew he was toying with death.

The kite was made of two light strips of cedar placed
crosswise, and a large silk handkerchief fastened to the
strips. A sharp wire about a foot long was fastened to
one of the strips. To the lower end of the cord he attached
a key and a silk ribbon. By means of the ribbon he held
the cord to insulate it from his hand. The kite soared into
the clouds, and Franklin and his son stood under a shed
awaiting the coming of the "electric fire "(Fig. 17). Soon

FIG. 17 FRANKLIN S KITE EXPERIMENT

Taking electricity from the clouds.

THE STORY OF GREAT INVENTIONS

the fibres of the cord began to bristle up. He approached
his knuckles to the key. A spark passed. He brought up
a Leyden jar and charged it with electricity from the
cloud, and found that with this charge he could do every-
thing that could be done with electricity from his machine.
He had proved the identity of lightning and electricity.

The Lightning-Rod

Some time before, he had discovered the action of a
point in discharging electricity. He said: "If you fix a
needle to the end of a gun-barrel like a little bayonet, while it
remains there the gun-barrel cannot be electrified so as to
give a spark, for the electric fire continually runs out silently
at the point." In the dark you may see a light gather upon
the point like that of a firefly or glow-worm. If the needle
is held in the hand and brought near to an object charged
with electricity, the object is quietly discharged, and a
light may be seen at the point of the needle. This action
of points explains the light sometimes seen on the tops of
ships' masts, called by sailors "Saint Elmo's fire," and
perhaps, also, the observation of Caesar that, in a certain
African war, the spears of the Fifth Roman Legion appeared
tipped with fire.

The lightning-rod was the outcome of Franklin's observa-
tions, and this was the first practical invention relating to
electricity. A building may be electrified by an electrified
cloud passing over it. If the building is protected by
pointed rods, the electric charge will quietly escape from
the points. The lower ends of the rods must be in the

THE EIGHTEENTH CENTURY

moist earth below the surface. The lightning-rod has not
proved so great a protection as Franklin supposed it would.
He supposed that a lightning- stroke is a discharge in one
direction only ; but we now know that it is a rapid surging
back and forth, and this fact accounts for the failure of the
lightning-rods to furnish perfect protection. In surging
back and forth, the lightning may skip from the lightning-
rod to some metal object within the building, as a stove or
radiator. The lightning-rod robbed the thunder-storm of
its terrors to the timid, and in time dispelled the supersti-
tion of people who believed that thunder and lightning are
evidence of the wrath of the Deity.

Franklin was the first to propose an answer to the ques-
tion: What is electricity? He believed electricity to be a
subtle fluid existing in all objects. If an object has more
than a certain amount of this fluid, it is positively elec-
trified; if less than this amount, it is negatively electrified.

The "one-fluid" theory of Franklin was soon met by the
"two-fluid" theory proposed by Robert Symmer, for
Franklin's theory had failed to explain why two bodies
negatively electrified should repel each other. According
to Symmer, an uncharged body contains an equal quantity
of two different electrical fluids. An excess of one of these
produces a positive charge, an excess of the other a negative
charge.

Symmer 's experiments are almost ludicrous. He wore
two pairs of silk stockings, and found that white and black
silk worn together became strongly electrified. When the
two stockings worn on one foot were pulled off together,
and then separated, they were found to be electrified, and

THE STORY OF GREAT INVENTIONS

attracted each other so strongly that a force of about one
pound was required to separate them. The two charges,
negative and positive, could, however, be separated. He
thought, therefore, that there are "two electrical powers,"
not one, as Franklin believed. His belief was strengthened
by examining a quire of paper through which an electric
spark had passed, and finding that "the edges of the holes
were bent two different ways, as if the hole had been made
in the quire by drawing two threads in contrary directions
through it."

There was a long controversy regarding the two theories,
and neither quite gained possession of the field. Each con-
tained some truth, and each had its weak points. The
two had more in common than men at that time thought.

Galvani and the Electric Current

Franklin had proven that there is electricity in the atmos-
phere, and that lightning is an electric discharge. A wide-
spread interest in the electricity of the atmosphere followed
this discovery. Aloisio Galvani, a physician in Bologna,
Italy, in attempting to learn the effect of atmospheric elec-
tricity on the nerves and muscles of the human body, made
a discovery which led to the electric battery and a knowl-
edge of electric currents.

Having dissected a frog, he laid it on a table on which
stood an electrical machine. When one of his assistants
touched lightly the nerve of the thigh with the point of a
knife while a spark was drawn from the electrical machine,
the muscles contracted violently, as if they were attacked

THE EIGHTEENTH CENTURY

by a cramp. When he held the knife by the bone handle,
there was no convulsion as there was when he held it by
the steel blade.

He next thought it important to find out if lightning
would excite contraction of the muscles. He stretched and
insulated a long iron wire in the open air on the housetop
and, as a storm drew near, hung on it a dissected frog. To
the feet he fastened another long iron wire, which was al-
lowed to dip in the water in the well. "The result," he said,
"came about as we wished. As often as the lightning broke
forth, the muscles were thrown into repeated violent con-
vulsions, so that always, as the lightning lightened the sky,
the muscle contractions and movements preceded the
thunder and, as it were, announced its coming. It was
best, however, when the lightning was strong, or the clouds
from which it broke forth were near the place of the experi-
ment."

He describes his greatest experiment as follows: "After
we had investigated the power of atmospheric electricity in
storms, our hearts burned with the desire to investigate
the daily quiet electricity of the atmosphere. Therefore, as
the prepared frogs, hung on an iron railing which surrounded
a hanging garden on our house, with brass hooks inserted
in the spinal cord, fell into convulsions not only when it
lightened, but when the sky was calm and clear, I thought
that the cause of these contractions was the changes in the
electricity of the atmosphere. Then for hours, yes, even
days, I observed the animals, but almost never a movement
of the muscles could be seen. At last, tired with such fruit-
less waiting, I began to press the brass hooks, which were

THE EIGHTEENTH CENTURY

fastened in the spinal cord, against the iron railing to see
if such a trick would cause the muscles to contract, and if
instead of changes in the atmospheric electricity any other
changes would have any influence. I observed, indeed,
vigorous contractions, but none which could be caused by
the condition of the atmosphere."

It was pressing the brass hook against the iron railing,
thus forming an electric battery, that caused electricity to
pass through the muscles of the frog. Galvani did not know
that he had discovered a new source of electricity. He
never arrived at a correct explanation of his results, and
never knew the value of his discovery.

Volta and the Electric Battery

It was left for Alexander Volta to show that, in Galvani' s
experiment, the muscles of the frog, together with the brass
hook and the iron railing, formed an electric battery. Volta
showed that an electric charge can be produced merely by
bringing two different metals into contact. He found that,
if he placed copper and zinc in sulphuric acid, or a solution
of common salt, he could produce a continuous flow of
electricity (Fig. 18).

In the beginning of the year 1800 Volta made the first
electric battery (Fig. 19). It was made of copper and
zinc disks placed alternately, with a piece of wet cloth
above each pair of disks. With his column of disks he
could obtain a strong shock; indeed, many shocks, one
after the other. This first battery of Volta's was a form
of "dry battery." Later Volta devised his "crown of

THE STORY OF GREAT INVENTIONS

FIG. IQ THE FIRST ELECTRIC BATTERY

No. i — A battery of one hundred pairs of copper and zinc disks.
No. 2 — Two such batteries connected.

By permission of the Italian Institute of Graphic Arts, Bergamo.

cups," a form of wet battery similar to some batteries in
use to-day. Each cup contained a strip of copper and a
strip of zinc in dilute sulphuric acid.

Volta did not know the real use of the liquid in his bat-
tery, nor that the strength of the current depends on the
rate at which the metal is dissolved by the acid; but he
had discovered the electric current, and with this discovery
began a new era in electrical invention.

Chapter IV

FARADAY AND THE FIRST DYNAMO

MICHAEL FARADAY, a London newsboy, the son of
a blacksmith, became the inventor of the dynamo, and
prepared the way for the wonderful electrical inventions of
the nineteenth century. He began his career as a book-
binder's apprentice, employing his spare moments in read-
ing the books he was binding. One of these books led him
to make some simple experiments in chemistry. He also
made an electrical machine, first with a glass bottle, and
afterward with a glass cylinder.

While an apprentice he wrote to his young friend, Ben-
jamin Abbott: "I have lately made a few simple galvanic
experiments, merely to illustrate to myself the first prin-
ciples of the science. I was going to Knight's to obtain
some nickel, and bethought me that they had malleable
zinc. I inquired, and bought some — have you seen any
yet ? The first portion I obtained was in the thinnest pieces
possible. It was, they informed me, thin enough for the
electric stick. I obtained it for the purpose of forming
disks with which and copper to make a little battery. The
first I completed contained the immense number of seven
pairs of plates!!! and of the immense size of halfpence

THE STORY OF GREAT INVENTIONS

each!!!!!! I, sir, I my own self, cut out seven disks of the
size of half pennies each! I, sir, covered them with seven
halfpence, and I interposed between them seven, or rather
six, pieces of paper soaked in a solution of muriate of soda
(common salt). But laugh no longer, dear A., rather
wonder at the effects this trivial power produced."

This tiny battery made of half pennies with zinc disks
and salt solution would decompose a certain solution which
Faraday tested. A larger battery made of copper and zinc
disks with salt solution would decompose water from the
cistern. When the wires from the larger battery were put
in the cistern-water he saw a dense white cloud descending
from the positive wire, and bubbles rising from the negative
wire. This action continued until all the white substance
was taken out of the water.

Because of his interest in science, young Faraday attracted
the attention of a Mr. Dance, a member of the Royal In-
stitution and a customer of his master, Mr. Riebau. Through
the kindness of Mr. Dance he heard four lectures by Sir
Humphry Davy. He took notes on the lectures, wrote
them out carefully, and added drawings of the apparatus.
These notes he sent to Davy with a letter expressing
the wish that he might secure employment at the Royal
Institution. In a short time, after a warning from Sir
Humphry that he had better stick to his business of book-
binding, that " Science is a harsh mistress," his wish was
granted, and we find him cleaning and caring for apparatus
in the Royal Institution and assisting Davy in preparing
for his lectures.

FARADAY AND THE FIRST DYNAMO

Count Rumford

Our story now takes us back to the time of the American
Revolution. In America, we find a young man of nineteen,
Benjamin Thompson by name, serving as major in the
Second Regiment of New Hampshire. The appointment of
so young a man as major, and his evident hold on the gov-
ernor's favor, aroused the jealousy of the older officers.
He was accused of being unfriendly to the cause of liberty.
He denied the charge, and was acquitted by the committee
of the people of Concord. A mob gathered round his house,
but he escaped. Driven from his refuge in his mother's
home, he fled to England, leaving his wife and child. Ap-
pointed lieutenant-colonel in the British Army, he returned
to America and fought against his former friends.

The war having ended, he returned to England, thence
to the Continent, intending to take part in an expected war
between Austria and Turkey. A chance meeting with a
Bavarian prince, Maximilian, changed the course of his life.
This prince, while commanding on parade, saw Thompson
among the spectators mounted on a fine English horse,
and addressed him. Thompson informed him that he came
from serving in the American war. The prince, pointing
to a number of his officers, said: " These gentlemen were in
the same war, but against you. They belonged to the Royal
Regiment of Deux Fonts, that acted in America under the
orders of Count Rochambeau." Thompson dined with
the prince and French officers. They conversed of war and
the battles in which they met. The prince, attracted to the

THE STORY OF GREAT INVENTIONS

colonel, induced him to pass through Munich, and gave him
a letter to his uncle, the Elector of Bavaria.

It was in Bavaria, the country to which such unexpected
turns of fortune led him, that his greatest work was done.
He entered the service of the Duke of Bavaria as aide-de-
camp. It was his aim while in the service of the Bavarian
Government to better the condition of the people. He in-
troduced reforms in the army, used the soldiers to rid the
country of beggars and robbers, and took steps to provide
for the infirm and find employment for the strong, his
motto being that people can best be made virtuous when
first made happy.

A Military Workhouse was opened for the beggars, and
a House of Industry for the poor. A Military Academy
was formed with a view to the free education of young peo-
ple of talent for the public service. He became absorbed
in the one aim of helping the poor. So thorough was his
devotion to the people, and so deeply did he win their
affection, that when he was dangerously ill a multitude of
hundreds went in procession to the church to make public
prayers for his recovery.

He saw that the poor may be helped by teaching them
to save, and in nothing is there greater need of saving than
in fuel and heat. In the kitchens of the Military Academy
and the House of Industry he carried out a series of experi-
ments on the economy of fuel, and succeeded in greatly
reducing the amount of fuel needed for cooking the food.
He did this by using a "closed fireplace," the forerunner
of the stove. The closed fireplace was in reality a brick
stove, and was a great improvement over the open chimney

FARADAY AND THE FIRST DYNAMO

fireplaces then in common use. He made the covers of
the cooking utensils double, to save the heat, for he had
found that heat cannot escape through confined air.

Benjamin Thompson was knighted by George III., and
in 1791 he was made a Count of the Holy Roman Empire,
and is known to the world of science as Count Rumford.

Count RumforcTs Experiment with the Cannon

While in the service of the Duke of Bavaria, it became
his duty to organize the field artillery. To provide cannon
for this purpose, he erected a foundry and machine-shops.
Being alert for any unusual fact relating to heat, he observed
the very high temperature produced by the boring of the
cannon. He was eager to learn how so much heat could
be produced. For this purpose he took a cannon in the
rough, as it came from the foundry, fixed it in the machine
used for boring, and caused the cannon to be turned by
horses while a blunt borer was forced against the end of the
cannon. He first tested the temperature of the metal itself
as it turned. Then he surrounded the end of the cannon
with water in an oblong box fitted water-tight (Fig. 20).

The cannon had been turning but a short time when he
found by putting his hand in the water that heat had been
produced. In two hours and thirty minutes the water
actually boiled. Astonishment was expressed in the faces
of the bystanders on seeing so large a quantity of water
heated and actually made to boil without any fire.

4 'Heat," Count Rumford said, "may thus be produced
merely by the strength of a horse, and, in case of necessity,

FARADAY AND THE FIRST DYNAMO

this heat might be used in cooking victuals. But no cir-
cumstance can be imagined in which there is any advan-
tage in this method of procuring heat, for more heat might
be obtained by burning the fodder which the horse would
eat." The meaning ot this last remark was not understood
until the time of Robert Mayer, about fifty years later.
Rumford had found that the work of a horse can produce
heat, and heat, in a steam-engine, can do the work of a
horse. Thus surely, though slowly, men were learning of
the forces that move the world and do man's bidding.

Count Rumford, true to his adopted land, returned to
London and became the founder of the Royal Institution
in which Faraday and his successors have achieved such
marvellous results. He believed that the poor can be helped
in no better way than by giving them knowledge, so that
they can better their own condition. For this purpose
he founded the Royal Institution. Here he intended that
men skilled in discovery should gain new knowledge that
would add to the comfort and happiness of the people.

Davy

In the English coal-fields many accidents due to the
burning of fire-damp had occurred. Fire-damp is caused
by gas issuing from the coal. On the approach of a flame
this gas catches fire, and as it burns it produces a violent
wind, driving the flame before it through the mine. Miners
were scorched to death, suffocated, or buried under ruins
from the roof. Hundreds of miners had been killed. No
means of lighting the mines in safety had been devised.

THE STORY OF GREAT INVENTIONS

Sir Humphry Davy, Professor of Chemistry in the Royal
Institution, was appealed to. After many experiments he
devised a "safe lamp," which was a common miner's lamp
enclosed in a wire gauze. This proved a perfect protection
from fire-damp, and the Davy safety lamp has been used
by miners the world over for more than a century.

But Davy's best work was with the electric battery.
Some of the facts most familiar to us were discovered by
him. Volta had contended that the contact of the metals
in a battery produces a current, that the liquid merely
carries the electricity from one metal plate to the other.
But Davy proved that there can be no current without
chemical action. Whenever we put two metals in an acid
or other solution that will dissolve one metal faster than
the other, and connect the metals with a wire, an electric
current is produced. If we use water with silver and gold,
there is no current, because water will not dissolve either
the silver or the gold.

Davy discovered the metal, potassium, by means of his
electric battery. Potassium is found in common potash
and saltpetre, and, when separated, is a very soft metal.
The newly discovered metal aroused great interest in other
countries. When Napoleon heard of it, he inquired im-
petuously how it happened the discovery had not been
made in France. On being told that in France there had
not been made an electric battery of sufficient power, he
exclaimed: "Then let one be instantly made without re-
gard to cost or labor." His command was obeyed, and he
was called to witness the action of the new battery. Before
any one could interfere he placed the ends of the wires

FARADAY AND THE FIRST DYNAMO

under his tongue and received a shock that nearly deprived
him of sensation. On recovering he left the laboratory
without a word, and was never afterward heard to refer to
the subject.

Davy made many great discoveries, but the greatest was
his discovery of Faraday.

A journey on the Continent with Davy was an event in
the life of Faraday, who up to that time had never to his
own recollection travelled twelve miles from London. On
this journey he met Volta, whom he describes as "an hale
elderly man, very free in conversation." He visited the
Academy del Cimento, in Florence, and wrote: "Here was
much to excite interest; in one place was Galileo's first
telescope, that with which he discovered Jupiter's satellites.
It was a simple tube of wood and paper, about three and a
half feet long, with a lens at each end. There was also
the first lens which Galileo made. It was set in a very
pretty frame of brass, with an inscription in Latin
on it."

Faraday crossed the Alps and the Apennines, climbed
Vesuvius, visited Rome, and saw a glow-worm. The last he
thought as wonderful as the first.

Shortly after his return to London he fell in love. Now,
Faraday had determined that he would not be conquered
by the master passion. In fact, he had written various
aspersions on love, of which the following is a sample:

"What is the pest and plague of human life?
And what the curse that often brings a wife?

Tis Love.
5 63

THE STORY OF GREAT INVENTIONS

What is't directs the madman's hot intent,
For which a dunce is fully competent?
What's that the wise man always strives to shun,
Though still it ever o'er the world has run?
Tis Love."

But he reckoned not with his own heart. It is not long
until we find him writing to Miss Sarah Barnard, a bright
girl of twenty-one: ''You have converted me from one
erroneous way, let me hope you will attempt to correct
what others are wrong. . . . Again and again I attempt to
say what I feel, but I cannot. Let me, however, claim not
to be the selfish being that wishes to bend your affections
for his own sake only. In whatever way I can minister to
your happiness, either by close attention or by absence, it
shall be done. Do not injure me by withdrawing your
friendship or punish me for aiming to be more than a friend
by making me less."

They were married and lived in rooms at the Royal
Institution. No poet ever loved more tenderly than Fara-
day. Truly, science does not dry up the heart's blood.
At the age of seventy-one he wrote to his wife while absent
from home for a few days: " Remember me; I think as
much of you as is good for either you or me. We cannot
well do without each other. But we love with a strong
hope of love continuing ever."

Faraday's Electrical Discoveries

Now we shall turn to Faraday's electrical discoveries
and inventions. Men had long known that, in houses that

FARADAY AND THE FIRST DYNAMO

have been struck by lightning, steel objects such as knives
and needles are sometimes found to be magnetized. Ships
struck by lightning had found their compass-needles point-
ing south instead of north, or wandering in direction and
worthless. Men had wondered how an electrical discharge
could magnetize steel. They had tried the spark of the
electrical machine with no definite result. Franklin, in his
experiment of magnetizing a steel needle by passing an
electric spark through it, could not tell before the spark was
passed through the needle which end would be the north
pole. There was no seeming connection between the di-
rection of the electric discharge and the polarity of the
needle. After the discovery of the electric battery, men
tried to discover a relation between the electric current and
magnetism.

Oersted and Electromagnetism

The first success in this direction was achieved by Hans
Christian Oersted, a native of Denmark. Poverty impelled
his father to take him from school at the age of twelve and
place him in an apothecary's shop. The boy, Hans, found
delight in the chemical work of the apothecary. His eager-
ness to learn and the pressure of poverty led him to neglect
the usual sports of boyhood and devote his leisure time to
reading and study. Again he entered school, and, though
paying his way by his own work, he graduated with honor
from the University of Copenhagen. He was appointed
Professor of Physics in this university, and here he made
his first great discovery in electromagnetism.

After working for seven years to discover a relation be-
5 65

THE STORY OF GREAT INVENTIONS

tween current electricity and magnetism, he made a dis-
covery which proved to be the first step in the invention of
the dynamo. He was using a magnetic compass, which is
a small magnetic needle balanced on a steel point. The
needle points nearly north and south unless disturbed by
a magnet brought near it. He had tried to find if a wire
through which a current is flowing would disturb the com-
pass as a magnet does. He had tried placing the wire east
and west, thinking the compass-needle would follow the

FIG. 21 OERSTED S EXPERIMENT

An electric current flowing over the compass-needle toward the north
causes the needle to turn until it points nearly west.

By permission of Joseph G. Branch.

wire as it does a magnet. One day, while lecturing to his
students, it occurred to him for the first time to place the
wire north and south over the compass-needle. He was
surprised and perplexed as he did so to see the needle
swing round and point nearly east and west (Fig. 21). On
reversing the current the needle swung in the opposite
direction. He had discovered the magnetic action of an
electric current. It was learned soon afterward that a coil
of wire with an electric current flowing through it acts like

FARADAY AND THE FIRST DYNAMO

a magnet, and that a current flowing around a bar of soft
iron makes the iron a magnet (Figs. 22 and 23).

FIG 22. A COIL WITH A CURRENT

FLOWING THROUGH IT ACTS
LIKE A MAGNET

The coil is picking up iron filings.

FIG. 23 A BAR OF SOFT IRON WITH

A CURRENT FLOWING AROUND
IT BECOMES A MAGNET

Ampere

The news of Oersted's discovery aroused great interest
throughout Europe. Soon aftei its announcement in France,
Andre Marie Ampere made a discovery of equal importance.
Oersted had discovered electromagnet ism. Ampere discov-
ered electrical power or motion produced by an electrical
current.

The youth of Ampere was passed amid the stormy scenes
of the French Revolution. His father had moved from his

THE STORY OF GREAT INVENTIONS

country home to Lyons and become a justice of the peace.
In the destruction of the city of Lyons during the Reign of
Terror he lost his head under the guillotine.

The blow was too great for Ampere, then a youth ot
eighteen. He had been a precocious child, advanced be-
yond his years in all the studies of the schools. But now
his strong mind failed. For a year he wandered about me-
chanically piling up heaps of sand or gazing upon the sky.
Then his mental power returned, and he took up with eager-
ness the study of botany and poetry.

He became a professor in the Polytechnic School in Paris,
and it was while teaching in this school that he made his
great discoveries. He found that two coils of wire can be
made to attract or repel each other by an electric current.
If the current flows through the two coils in the same direc-
tion, they attract each other (Fig. 24). If the current flows

FIG. 24 TWO COILS WITH CUR-
RENTS FLOWING IN SAME DIREC-
TION ATTRACT EACH OTHER

FIG. 25 TWO COILS WITH CUR-
RENTS FLOWING IN OPPOSITE DI-
RECTIONS REPEL EACH OTHER

FARADAY AND THE FIRST DYNAMO

in opposite directions through the coils, they repel each
other (Fig. 25). This is not very strange to us, for we
know that a coil with a current flowing through it acts just
like a magnet. Each coil then has a north pole and a south
pole. If the coils are placed so that the two north poles or
the two south poles are together, they will repel each other.
If the north pole of one coil is near the south pole of the
other, they will attract each other.

Ampere believed that electric currents are flowing around
within the earth, and that the earth has a north and a south
magnetic pole for the same reason that a coil of wire has
magnetic poles; that these poles are caused by the currents
flowing around in the earth just as the poles of the coil are
caused by the current flowing around in the coil.

We do honor to the name of Ampere whenever we measure
an electric current, for electric currents are measured in
"amperes."

Arago

Another important discovery was made by a young
Frenchman, Francois Arago, within a year of the time when
Oersted and Ampere made their discoveries. The three
great discoveries of these men were made in the years 1819
and 1820. The youth of Arago was full of adventure. He
had assisted in making a survey in the Pyrenees, the haunt
of daring robber-bands. Twice in his cabin he was visited
by a chief of a robber-band who claimed to be a custom-
house guard. On the second visit he said to the robber:
"Your position is perfectly known to me. I know that you
are not a custom-house guard. I have learned that you

THE STORY OF GREAT INVENTIONS

are the chief of the robbers of the country. Tell me whether
I have anything to fear from your confederates." The
robber replied: "The idea of robbing you did occur to us;
but, on the day that we molested an envoy from the French,
they would direct against us several regiments of soldiers,
and we are not so strong as they. Allow me to add that the
gratitude which I owe you for the night's shelter is your
surest guarantee."

At a later time, when war between Spain and France was
threatened, he was accused of being a spy, and a mob was

formed to put him out
of the way. He escaped
in disguise through the
midst of the mob and
boarded a Spanish ship.
He was carried to Moroc-
co, ran the gantlet of
bloodthirsty Mussulmans
in Algiers, escaped death
by a hair's-breadth, and
through it all clung to
the papers which record-
ed the results of the sur-
vey in the mountains,
FIG. 26— ARAGO'S EXPERIMENT an(j delivered them in

When the copper plate whirls the mag- safety to the office -of
net whirls also, though it does not touch .

the copper plate. the Bureau of Longitude

in Paris.

Arago made a discovery which, with those of Oersted and
Ampere, prepared the way for Faraday's great electrical

FARADAY AND THE FIRST DYNAMO

discoveries and the invention of the dynamo. He found that a
plate of copper whirling above or below a magnetic needle will
draw the needle after it (Fig. 26) . He could make the speed of
the whirling copper plate so great that the needle would whirl
rapidly, following the
copper plate. Faraday
was the first to explain
Arago's experiment.

Faraday's First Electric
Motor

Faraday's first electri-
cal discovery was made
soon after that of Ara-
go. Oersted had proven
that an electric current
acts on a magnet. The
magnet turns at right
angles to the wire. Far-
aday saw that this is be-
cause the north pole of
the magnet tries to go
round the wire in one
direction, and the south
pole tries to go round
in the opposite direc-
tion. He placed a magnet on end in a dish of mercury,
with one pole of the magnet above the mercury, and found
that the magnet would spin round a wire carrying a cur-
rent. When the current acts on one pole of the magnet

FIG. 27 ONE POLE OF A MAGNET SPINS

ROUND A WIRE THROUGH WHICH AN
ELECTRIC CURRENT FLOWS

THE STORY OF GREAT INVENTIONS

only, the magnet spins round the wire (Fig. 27). So Fara-
day's first electrical discovery prepared the way for the
electric motor.

An Electric Current Produced by a Magnet

He had written in his note-book: "Convert magnetism
into electricity." An electric current would magnetize iron.
Would not a magnet produce an electric current ? This
was his problem.

He connected a coil of wire to an instrument that would
tell when a current was flowing, and placed a magnet in the
coil. Others had claimed, and Faraday at first believed, that
a current would flow while the magnet lay quiet within the
coil. But Faraday was alert for the unexpected, and the
unexpected happened. For an instant, as he thrust the
magnet into the coil, his instrument showed that a current
was flowing. Again, as he drew the magnet quickly from
the coil, a current flowed, but in the opposite direction
(Fig. 28). From this simple experiment has grown the
alternating-current machinery by which the power of
Niagara is made to light cities and drive electric cars at a
distance of many miles.

A friend of Faraday, on learning of this discovery, wrote
the following impromptu lines:

"Around the magnet Faraday
Was sure that Volta's lightnings play.

But how to draw them from the wire?
He took a lesson from the heart: t*

'Tis when we meet, 'tis when we part,
Breaks forth the electric fire."
72

FARADAY AND THE FIRST DYNAMO

FIG. 38 WHEN A MAGNET IS THRUST INTO A COIL OF WIRE IT CAUSES A

CURRENT TO FLOW IN THE COIL, BUT THE CURRENT FLOWS

ONLY WHILE THE MAGNET IS MOVING
Drawing reproduced by permission of Joseph G. Branch.

A magnet will produce an electric current in a wire, but
only when the magnet or the wire is in motion.

Detecting and Measuring an Electric Current

The instrument which Faraday used to detect a current
was derived from Oersted's experiment. When a current
flows in a north-and- south direction over a compass-needle,
the needle swings round. When the current stops flowing

THE STORY OF GREAT INVENTIONS

the needle swings back to the north-and- south position.
The effect on the needle is stronger if the current flows
through a coil of wire and the coil is placed in a north-and-
south position around the needle (Fig. 29). The stronger
the current flowing through the coil the farther the needle
will turn from the north-and- south position.

FIG. 29 A COIL OF WIRE AROUND A COMPASS-NEEDLE

The needle tells when a current is flowing, and how strong the current is.

The coil and the needle together are called a galvanom-
eter, and may be used to tell when a current is flowing,
and also to indicate the strength of the current.

An Electric Current Produced by the Magnetic Field of Another

Current

Faraday had found that a current flowing around a piece
of iron will make the iron a magnet, and that a magnet in
motion will cause a current to flow in a wire. It seemed

FARADAY AND THE FIRST DYNAMO

to him that a second wire placed near the first should have
a current produced in it without the presence of iron. He
wound two coils of copper wire upon the same wooden spool.
The wire of the two coils he separated with twine and calico.
One coil was connected with a galvanometer, the other with
a battery of ten cells, yet not the slightest turning of the
needle could be observed. But he was not deterred by one
failure. He raised his battery from ten cells to one hundred
cells, but without avail. The current flowed calmly through
the battery wire without producing, during its flow, any
effect upon the galvanometer. During its flow was the
time when an effect was expected.

Again the unexpected happened. At the instant of mak-
ing contact with the battery there was a slight movement
of the needle. When the contact was broken, another slight
movement, but in the opposite direction to the first (Fig.
30). The current in one wire caused a current to flow
in the other, but the current in the second wire con-
tinued for an instant only at the making and breaking
of the contact with the battery. This was the begin-
ning of the induction-coil used to-day in wireless teleg-
raphy.

What was the secret of it ? Simply this : that a current
in one wire will cause a current to flow in another wire near
it, but only while the current in the first wire is changing.
That is, at the instant when the first wire is connected to
the battery, or its connection broken, a current is induced
in the second wire. There is no battery or other source of
current connected to the second wire; but a current flows
in this wire because it is near a wire in which a current is

THE STORY OF GREAT INVENTIONS

rapidly starting and stopping. When these two wires are
wound in coils, together they form an induction-coil. The
wire which we have called the first wire forms the ' ' primary "

FIG. 30 — FARADAY'S INDUCTION-COIL

Starting and stopping the battery current in the primary coil causes
a changing magnetic field, and this causes a current to flow in the
secondary coil.

Drawing reproduced by permission of Joseph G. Branch.

coil, and the one we have called the second wire forms the
"secondary" coil. By repeatedly making and breaking the
circuit in the primary coil we get an alternating current in

FARADAY AND THE FIRST DYNAMO

the secondary coil. Fig. 31 is from a photograph of some
of the coils actually used by Faraday.

Faraday's Dynamo

To invent a new electrical machine was Faraday's next
aim. Arago's disk of copper whirling near a magnet had
a current induced in it, so Faraday thought. It was the

FIG. 31 HISTORICAL APPARATUS OF FARADAY IN THE ROYAL INSTITUTION

Some of Faraday's transformer coils are shown here. The instrument
on the left in a glass case is his galvanometer.

action of this induced current which caused the magnet to
follow the whirling disk. Could the current in Arago's disk
be collected and caused to flow through a wire ? He placed
a copper disk between the poles of a magnet. One galva-

THE STORY OF GREAT INVENTIONS

nometer wire passed around the axis of the disk, the other he
held in contact with the edge. He whirled the disk. The
galvanometer needle moved. A current was flowing in the
disk as it whirled. The current from the whirling disk
flowed through the galvanometer. Faraday had discovered
the dynamo (Fig. 32).

FIG. 32 — FARADAY'S FIRST DYNAMO

A current flows in the copper disk as it whirls between the poles
of the magnet.

By permission of Joseph G. Branch.
78

FARADAY AND THE FIRST DYNAMO

All this work occupied but ten days in the autumn of
1831, though years of preparation had gone before. In
these ten days the foundation was laid for the induct ion-

FIG. 33 FARADAY S LABORATORY, WHERE THE FIRST DYNAMO WAS MADE

From the water-color drawing by Miss Harriet Moore.

coil, modern dynamo - electric machinery, and electric
lighting. Fig. 33 shows the laboratory in which Faraday
did this work.

Faraday continued to explore the field opened up be-
fore him. In one experiment two small pencils of charcoal
lightly touching were connected to the ends of a secondary
G 79

THE STORY OF GREAT INVENTIONS

coil. A spark passed between the charcoal points when
the primary circuit was closed. This was the first trans-
former producing a tiny electric light (Fig. 34).

Faraday discovered the induction-coil, the dynamo, and
the transformer, and he showed that, in each of these, it is
magnetism which produces the electric current. He had

SECONDARY/

COIL

FIG. 34 THE FIRST TRANSFORMER

discovered the secret when he obtained a current by thrust-
ing a magnet into a coil of wire. The space about a magnet
in which the magnet will attract iron he called the ' ' magnetic
field" (Figs. 35 and 36). In every case of magnetism caus-
ing an electric current to flow in a coil of wire, the coil is
in a magnetic field, and the magnetic field is changing — that

FARADAY AND THE FIRST DYNAMO

FIG. 35 — THE "MAGNETIC FIELD" is THE SPACE AROUND A MAGNET IN

WHICH IT WILL ATTRACT IRON

The iron filings over the magnet arrange themselves along the "lines
of force."

is, the magnetic field is made alternately stronger and weak-
er, or the coil moves across the magnetic field. The point is
that magnetism at rest will not produce an electric current.
There must be a changing magnetic field or motion. In
Faraday's dynamo a copper disk whirled between the poles

FIG. 36 MAGNETIC FIELD OF A HORSESHOE MAGNET

THE STORY OF GREAT INVENTIONS

of a magnet and the whirling of the disk in the magnetic
field caused an electric current. In the modern dynamo it
is the whirling of a coil of wire in a magnetic field that
causes a current to flow. In the induction-coil it is the
change in the magnetic field that causes a current to flow
in the secondary coil. A coil of wire with an electric
current flowing through it will attract iron like a magnet.
The primary coil with a current from a battery flowing
through it acts in all respects like a magnet; but as soon
as the current ceases to flow the magnetic field disappears —
the coil is no longer a magnet. When we make and break
the connection between the primary coil and the battery,
then, we repeatedly make and destroy the magnetic field,
and this changing magnetic field causes a current to flow
in the secondary coil. The induction-coil is one form of
transformer. We shall see later how the dynamo and the
transformer developed in the nineteenth century.

When a boy, Faraday had passed the current from his
little battery through a jar of cistern-water, and saw in the
water a " dense white cloud" descending from the positive
wire, and bubbles arising from the negative wire. Some-
thing was being taken out of the water by the electric cur-
rent. When he tried the experiment later in his laboratory,
he found that, whenever an electric current is passed through
water, bubbles of two gases, oxygen and hydrogen, rise
through the water. He found that if the current is made
stronger the bubbles are formed faster. The water in time
disappears, for it has been changed or "decomposed" into
the two gases.

It was the current from a battery that would decompose

FARADAY AND THE FIRST DYNAMO

water. The electricity from the electrical machine would
do other things that he had never seen a battery current
do. "Do the battery and the electrical machine produce
different kinds of electricity, or is electricity one and the
same in whatever way it is produced ?" This was the query
that troubled him. The answer to this question had been
so uncertain that the effect of the voltaic battery had been
termed "galvanism," while that of the friction machine
retained the name "electricity."

Faraday tried many experiments in searching for an
answer to this question. He found that the electricity of
the machine will produce the same effect as that of a bat-
tery if the machine is compelled to discharge slowly. An
electrical machine or a battery of Ley den jars can be made
to give out an electric current, and this current will affect
a magnetic needle in the same way that a battery current
will. It will magnetize steel. If passed through water, it
will decompose the water into the two gases oxygen and
hydrogen. In short, a current from an electrical machine
or a Ley den jar will do everything that a current from an
electric battery will do. Faraday caused the Leyden jar
to give a current instead of a spark by connecting the two
metal coatings with a wet string. On the other hand, the
discharge from a powertul electric battery willx produce a
spark and affect the human nerves in the same way as the
discharge from the electrical machine. The same effects
may be obtained from one as from the other.

In the discharge from the machine, a small quantity of
electricity is discharged under high pressure, as water may
be forced through a small opening by very high pressure.

THE STORY OF GREAT INVENTIONS

The voltaic cell, on the other hand, furnishes a large quantity
of electricity at low pressure, as a street may be flooded by
a broken water-main though the pressure is low. In fact,
the quantity of electricity required to decompose a grain
of water is equal to that discharged in a stroke of lightning,
while the action of a dilute acid on the one-hundredth part
of an ounce of zinc in a battery yields electricity sufficient
for a powerful thunder-storm.

Many tests were made, and the result was a convincing
proof that electricity is the same whatever its source, the
different effects being due to difference in pressure and
quantity. "But in no case," said Faraday, "not even in
those of the electric eel and torpedo, is there a production
of electric power without something being used up to sup-
ply it."

Faraday's professional work would have made him
wealthy. In one year he made £1000 ($5000), and the
amount would have increased had he sold his services at
their market value. But then there would have been no
Faraday the discoverer. The world would have had to
wait, no one knows how long, for the laying of the founda-
tions of electrical industries. He chose to give up wealth
for the sake of discovery. He gave up professional work
with the exception of scientific adviser to Trinity House,
the body which has charge of Great Britain's lighthouse
service. Nor did he carry his discoveries to the point of
practical application. As soon as he discovered one prin-
ciple, he set out in pursuit of others, leaving the practical
application to the future.

Faraday loved the beauty of nature. The sunset he

FARADAY AND THE FIRST DYNAMO

called the scenery of heaven. He saw the beauty of elec-
tricity, which he said lies not in its mystery, but in the
fact that it is under law and within the control of the human
intellect.

A Wonderful Law of Nature

Not long after Faraday made his first dynamo, Robert
Mayer, a physician from Germany, was making a voyage
to the East Indies which proved to be a voyage of discovery.
He had sailed as the ship's physician, and after some
months an epidemic broke out among the ship's company.
In his treatment he drew blood from the veins of the arms.
He was startled to see bright-red blood issue from the veins.
He might almost have believed that he had opened an artery
by mistake. It was soon explained to him by a physician
who had lived long in the tropics that the blood in the veins
of the natives, and of foreigners as well, in the tropics is
of nearly the same color as arterial blood. In colder
climates the venous blood is much darker than the arte-
rial.

He reasoned upon this curious fact for some time, and
came to the conclusion that the human body does not
make heat out of nothing, but consumes fuel. The fuel is
consumed in the blood, and there the heat is produced. In
the tropics less heat is needed, less fuel is consumed, and
therefore there is less change in the color of the blood.

When a man works he uses up fuel. If a blacksmith
heats a piece of iron by hammering, the heat given to the
iron and the heat produced in his body are together equal
to the heat of the fuel consumed in his blood. The work a

THE STORY OF GREAT INVENTIONS

man does, as well as the heat of his body, comes from the
burning of the fuel in his blood.

What is true of a man is true of an engine. The work
the engine does, as well as the heat it produces, comes from
the heat of the fuel in the furnace. Mayer found that one
hundred pounds of coal in a good working engine produces
the same amount of heat as ninety-five pounds in an engine
that is not working. In the working engine the heat of the
five pounds of coal is used up in the work of running the
engine, and therefore does not heat the engine. Heat that
is used in running the engine is no longer heat, but work.
So Mayer said the heat is not destroyed, but only changed
into work. He said, further, that the work of running the
engine may be changed again into heat.

Mayer's theory was opposed by many scientific men of
Europe. One great scientist said to him that if his theory
were correct water could be warmed by shaking. He re-
membered what the helmsman had remarked to him on
the voyage to Java, that water beaten about by a storm is
warmer than quiet sea- water; but he said nothing. He
went to his laboratory, tried the experiment, and some
weeks later returned, exclaiming: "It is so! It is so!"
He had warmed water simply by shaking it.

These results mean that work or energy cannot be de-
stroyed. Though it changes form in many ways, it is never
destroyed. Neither can man create energy; he can only
direct its changes as the engineer, by the motion of his
finger in opening a valve, sets the locomotive in motion. He
does not move the locomotive. He directs the energy al-
ready in the steam.

FARADAY AND THE FIRST DYNAMO

Since the time of Galileo, men had caught now and then
a glimpse of this great law.. Galileo had stated his law of
machines; that, when a machine does work, a man or a
horse or some other power does an equal amount of work
upon the machine. Count Rumford had performed his ex-
periment with the cannon, showing that heat is produced
by the work of a horse. Davy had proved that, in the
voltaic battery, something must be used up to produce the
current — the mere contact of the metals is not sufficient.
Faraday had said that in no case is there a production of
electrical power without something being used up to supply
it. Mayer stated clearly this law of energy when he said
that energy cannot be created or destroyed, but only
changed from one form to another.

And yet inventors have not learned the meaning of this
law. They continue trying to invent perpetual - motion
machines — machines that will produce work from nothing.
This is what a perpetual-motion machine would be if such
a machine were possible. For a machine without friction is
impossible, and friction means wasted work — work changed
into heat. A machine to keep itself running and supply
the work wasted in friction must produce work from noth-
ing. The great law of nature is that you cannot get some-
thing for nothing. Whether you get work, heat, electricity,
or light, something must be used up to produce it. For
whatever you get out of a machine you must give an equiva-
lent. This law cannot be evaded, and from it there is no
appeal.

Chapter V
GREAT INVENTIONS OF THE NINETEENTH CENTURY

THE discoveries of Faraday prepared the way for the
great Inventions of the nineteenth century. By the
middle of the century men knew how to control the won-
derful power of electricity. They did not know what elec-
tricity is, nor do we know to-day, though we have made
some progress in that direction ; but to control it and make
it furnish light, heat, and power was more important.

Before the inventions of James Watt made it possible to
use steam-power, factories were built near falling water, so
that water-power could be used. But the steam-engine
made it possible to build great factories wherever a supply
of water for the boilers could be obtained. Cities were built
around the factories. Cities already great became greater.
With the growth of cities the need of a new means of pro-
ducing light and power made itself felt. Electricity prom-
ised to become the Hercules that should perform the tasks
of the modern world.

Discovery gave way to invention. During the second
half of the nineteenth century many great inventions were
made and industries were developed, while discoveries were
few until near the close of the century. Within this period

NINETEENTH-CENTURY INVENTIONS

the great industries which characterize our modern civiliza-
tion, and which arose out of the discoveries that science had
made in the centuries preceding, attained a high degree of
development. In this chapter we shall trace the applica-
tions of some of the discoveries with which we have now
become familiar. This will lead us into the field of electri-
cal invention, for we are dealing now with the beginning
of the world's electrical age.

Electric Batteries

From the time of Volta to the time of Faraday the only
means of producing an electric current was the " voltaic bat-
tery," so called in honor of Volta. The voltaic cell is the
simplest form of electric battery. In this cell the zinc and
copper plates are placed in sulphuric acid diluted with
water. As the acid eats the zinc, hydrogen gas is formed.
This gas collects in bubbles on the copper plate and weakens
the current. The aim of inventors was to produce a steady
current, to devise a battery in which no gas would collect
on the copper plate. They saw the need of a battery that
would give out a current of unchanging strength until the
zinc or the acid was used up.

The first real improvement in the battery was made by
Professor Daniell, of King's College, London. In the Daniell
cell the zinc plate is in dilute sulphuric acid, and the copper
plate is in a solution of blue vitriol or copper sulphate.
Professor Danieil separated the two liquids by placing one
of them in a tube formed of the gullet of an ox. This tube
dipped into the other liquid. The hydrogen gas, as it was

THE STORY OF GREAT INVENTIONS

formed by the acid acting on the zinc, could go through
the walls of the tube, but was stopped by the copper sul-
phate, and copper was deposited on the copper plate. This
copper deposit in no way interfered with the current, so
that the current was not weakened until the zinc plate or
one of the solutions was nearly consumed. A cup of porous
earthenware is now used in Daniell cells to separate the

FIG. 37 A DANIELL CELL

liquids (Fig. 37). By placing crystals of blue vitriol in the
battery jar, the solution of blue vitriol can be kept up to
its full strength for a very long time. The zinc in time is
consumed, and must be replaced.

NINETEENTH-CENTURY INVENTIONS

FIG. 38 A GRAVITY CELL

In the gravity cell (Fig. 38)
the same materials are used
as in the Daniell cell — cop-
per in copper sulphate, and
zinc in sulphuric acid; but
there is no porous cup. The
solutions are kept separate
by gravity, the heavy cop-
per sulphate being at the
bottom. The gravity cell has
until recently been extensive-
ly used in telegraphy, and
continues in use in short-dis-
tance telegraphy and in au-
tomatic block signals. The

gravity and Daniell cells are used for closed-circuit work-
that is, for work in which the current is flowing almost con-
stantly.

The Dry Battery

Another important improvement was the invention of
the dry battery. You will remember that the first battery,
the one invented by Volta, was a form of dry battery ; but
it was a very feeble battery compared with the dry bat-
teries now in use, so that we may call the dry battery a
new invention. The dry battery is falsely named. There
can be no battery without a liquid. In the dry battery
the zinc cup forming the outside of the cell is one of the
plates of the cell (Fig. 39). The battery appears to be dry
because the solution of sal ammoniac is absorbed by blot-
ting-paper or other porous substance in contact with the

THE STORY OF GREAT INVENTIONS

zinc. The inner plate is carbon, and this is surrounded by
powdered carbon and manganese dioxide — the latter to
remove the hydrogen gas which collects on the carbon
plate. This gas weakens the current when the circuit has
been closed for a short time, but is slowly removed when
the circuit is broken. Thus the battery is said to "recover."

The dry cell will give

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f^vy

. *» Y." «

• *

*•*!*' !**

* *

I .

• . •

. •

9 ? ."

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ous substance tr/'tA
sal ammoniac

Zinc

dioxide.

a strong current, but for
a short time only. It
recovers, however, if al-
lowed to rest. It can
be used, therefore, only
in "open-circuit" work
— such as door-bell cir-
cuits, and some forms of
fire and burglar alarm.
A door -bell circuit is
open nearly all the time,
the current flowing only
while the button is being
pressed. Some forms of
wet battery work in the
same way as the dry bat-
tery, and are used like-
wise for open - circuit
work. In these batteries carbon and zinc plates in a so-
lution of sal ammoniac are used, the same materials as in
the dry battery. The only difference is that in the dry
battery the solution is absorbed by some porous substance
and the battery sealed so that it appears to be dry,

FIG. 39 SHOWING WHAT IS IN

BATTERY

A DRY

NINETEENTH-CENTURY INVENTIONS

The Storage Battery

One of the greatest improvements in electric batteries is
the storage battery. A simple storage battery may be
made by placing two strips of lead in sulphuric acid diluted
with water and connecting the lead strips to a battery of
Daniell cells or dry cells. In a short time one of the lead
strips will be found covered with a red coating. The sur-
face of this lead strip is no longer lead but an oxide of lead,
somewhat like the rust that forms on iron. If the lead strips
are now disconnected from the other battery and connected
to an electric bell, the bell will ring. We have here two
plates, one of lead and one of oxide of lead, in dilute sul-
phuric acid. This forms a storage battery.

The first storage battery was made of two sheets of lead
rolled together and kept apart by a strip of flannel. The
lead strips thus separated were immersed in dilute sulphuric
acid. A current from another battery was passed through
this cell for a long time — first in one direction, then in the
other. This roughened the surface of the lead plates, so
that the battery would hold a greater charge. The battery
was then charged by passing a current through it in one
direction only for a considerable length of time. Feeble
cells were used for charging. It took days, and sometimes
weeks, to charge the first storage batteries. Then the stor-
age battery would give out a strong current lasting for a
few hours. It slowly accumulated energy while being
charged, and then gave out this energy rapidly in the form
of a strong electric current. For this reason the storage
battery was called an "accumulator."

THE STORY OF GREAT INVENTIONS

While charging the storage cell there was formed on the
negative plate a coating of soft lead, and on the positive
plate a coating of dark-brown oxide of lead. It was found

better to apply these coat-
ings to the lead plates be-
fore making up the battery.
Later it was found that
the battery would hold a
still greater charge if the
plates were made in the
form of "grids" (Fig. 40),
and the cavities filled with
the active material — the
negative with spongy lead,
and the positive with dark-
brown lead oxide. Some
excellent commercial stor-
age batteries are made from
lead plates by the action of
an electric current, very
much as Plante made his
batteries. Fig. 41 shows
one of these plates.

FIG. 4<

-A STORAGE BATTERY, SHOW-
ING THE "GRIDS"

The storage battery does
not store up electricity. It
produces a current in exactly the same way as any other
battery — by the action of the acid on the plates. When
this action ceases it is no longer a battery, though it may
be made one again by passing a current through it in the
opposite direction from that which it gives out. In this

NINETEENTH-CENTURY INVENTIONS

it differs from the voltaic battery, for when such a battery
is run down it can be restored only by adding new solution
or new plates. The storage battery is especially useful for
"sparking" in gas or gasolene motors.

Edison has invented a storage battery that will do as
much work as a lead battery of twice its weight. Edison's
battery is intended especially for use in electric automobiles.
By reducing the weight
of the battery which
the machine must car-
ry the weight of the
truck may also be re-
duced. In the Edison
battery the positive
plates are made of a
grid of nickel - plated
steel containing tubes
filled with pure nickel.
The negative plate con-
sists of a nickel-plated
steel grid containing an
oxide of iron similar to
common iron-rust.

After working a num-
ber of years on this bat-
tery and making nine
thousand experiments,
Edison thought he had
it perfected, and indeed

, . FIG. 41 A STORAGE - BATTERY PLATE

It Was a great improve- MADE FROM A SHEET OF LEAD

7 95

THE STORY OF GREAT INVENTIONS

ment over the storage batteries that had been used — much
lighter and cheaper, and more successful in operation. Two
hundred and fifty automobiles were equipped with it, and it
proved superior to lead batteries for this purpose. But it was
not to Edison's liking. He threw the machinery, worth thou-
sands of dollars, on the scrap-heap, and worked on for six
years. He had then produced a battery as much better
than the first as the first was better than the lead battery,
and he was content to have the new battery placed on the
market.

The Dynamo

For the purpose of lighting and power the electric bat-
tery proved too costly. Davy produced an arc light with
a battery of four thousand cells. The arc was about four
inches in length and yielded a brilliant light, but as the
cost was six dollars a minute it was not thought practical.
Attempts were made early in the century to use a battery
current for power, but they failed because of the cost and
the fact that no good working motor had been invented.

Light and power were needed. Electricity could supply
both. But how overcome the difficulty of cost, and produce
an electric current from burning coal or falling water ? For
answer man looked to the great discovery of Faraday and
his "new electrical machine." Inventors in Germany,
France, England, Italy, and America made improvements
until from the disk dynamo of Faraday there had evolved
the modern dynamo.

Electroplating and the telegraph are the only applica-
tions of the electric current that became factors in the

NINETEENTH-CENTURY INVENTIONS

world's industry before the dynamo, yet in long-distance
telegraphy and in electroplating to-day the dynamo is used.
Without the dynamo, electric lighting, electric power, and
electric traction as developed in the nineteenth century
would have been impossible; in fact, the dynamo with the
electric motor (which, as we
shall see, is only a dynamo
reversed) is master of the
field.

The way had been pre-
pared for the application
of Faraday's discovery by
William Sturgeon, an Eng-
lishman, and Joseph Henry,
an American. Sturgeon dis-
covered that soft iron is
more quickly magnetized
than steel, and found that
the strength of an electro-
magnet can be greatly in-
creased by making the core
of a soft-iron rod and bend-

FIG' 42~

ELECTR°-

ing the rod into the form

of a horseshoe (Fig. 42). The iron rod was coated with
sealing-wax and wound with a single layer of copper wire,
the turns of wire not touching. This was in 1825, before
Faraday discovered the principle of the dynamo.

Professor Henry still further increased the strength of
the electromagnet by covering the wire with silk, which
made it possible to wind several layers of wire on the iron

THE STORY OF GREAT INVENTIONS

FIG. 43 AN ELECTROMAGNET WITH MANY TURNS OF INSULATED WIRE

core, and many times the length of wire that had been
used by Sturgeon. Fig. 43 shows such a magnet. One of
Henry's magnets weighed fifty-nine and a half pounds, and
would hold up a ton of iron. Sturgeon said: " Professor
Henry has produced a magnetic force which completely
eclipses every other in the whole annals of magnetism."
With Professor Henry's invention the electromagnet was
ready for use in the dynamo. Fig. 44 shows a strong
electromagnet.

A moving magnet causes a current to flow in a coil, but
a magnet at rest has no effect. A moving magnet is equal
to a battery. In Faraday's experiments a current was in-
duced in a coil of wire by moving a magnet in the coil or by

NINETEENTH-CENTURY INVENTIONS

making and breaking the circuit in another coil wound on
the same iron core. A current was induced in a metal disk
by revolving it between the poles of a magnet. In every
case there was motion in a magnetic field, or the field itself
was changed. A changing magnetic field is equal to a
moving magnet. What
is needed to induce a
current in a coil, whether
it be in a dynamo, an
induction-coil, or a trans-
former, is a changing
magnetic field about the
coil or motion of the coil
in the magnetic field.

If fine iron filings are
sprinkled over the poles
of a magnet the filings
arrange themselves in
definite lines. This is a
simple experiment which
any boy can try for him-
self. Faraday called the
lines marked out by the
iron filings "lines of
force" (the lines of force
of a horseshoe magnet
are shown in Fig. 36),

because they indicate the direction - in which the mag-
net pulls a piece of iron — that is, the direction of the
magnetic force. Now, if a current is to be induced in a

FIG. 44 AN ELECTROMAGNET LIFTING

TWELVE TONS OF IRON

THE STORY OF GREAT INVENTIONS

wire, the wire must move across the lines of force. If
the wire moves along the lines marked out by the iron
filings, there will be no current. When a coil rotates be-
tween the poles of a magnet, the wire moves across the lines
of force and a current is induced in the coil if the circuit is
closed. This is the way a current is produced in a dynamo.
Faraday produced a current by rotating a coil between
the poles of a steel magnet. He made a number of such
machines, and used them with some success in producing
lights for lighthouses, but the defects of these machines
were so great that the lighting of a city or the development
of power on a large scale was impractical. The electro-
magnet was needed to solve the problem.

Siemens' Dynamo

The war of 1866 between Austria and Prussia and the
certainty of a coming struggle with France turned the at-
tention of German inventors to the use of electricity in
warfare. Werner von Siemens, an artillery officer, was
improving an exploding device for mines. An electric cur-
rent was needed to produce a spark or heat a wire to red-
ness in the powder. Faraday had used a coil of wire turn-
ing between the poles of a steel magnet to produce a current.
In England a coil turning between the poles of an electro-
magnet had been used, but the electromagnet received
its current from another machine in which a steel magnet
was used. Siemens found that the steel magnet could be
dispensed with, and that a coil turning between the poles
of an electromagnet could furnish the current for the

100

NINETEENTH-CENTURY INVENTIONS

electromagnet. Two things are needed, then, to make a
dynamo: an electromagnet and a coil to turn between
the poles of that magnet. The rotating coil, which usually
contains a soft-iron core, is called the " armature." The
coil will furnish current for the magnet and some to spare;
in fact, only a small part of the current induced in the coil
is needed to keep the magnet up to its full strength, and the
greater part of the current may be used for lighting or

FIG. 45 — A DYNAMO WITH SIEMENS ARMATURE
101

THE STORY OF GREAT INVENTIONS

power. The new machine was named by its inventor ' ' the
dynamo-electric machine." The name has since been short-
ened to ''dynamo." The first practical problem which the
dynamo solved was the construction of an electric explod-
ing apparatus without the use of steel magnets or bat-
teries. A dynamo with Siemens' armature is shown in Fig. 45 .

FIG. 46 RING ARMATURE

In his first enthusiasm the inventor dreamed of great
things for the new machine, among others an electric street
railway in Berlin. But the dynamo was not yet ready.
The difficulty was the heating of the iron core of the arma-
ture, caused by the action of induced currents. There are
induced currents in the iron core as well as in the coil, and,
for the same reason, the coil and the iron core within it are
both moving in a magnetic field. These little currents circling

102

NINETEENTH-CENTURY INVENTIONS

FIG. 47 FIRST DYNAMO PATENTED IN THE UNITED STATES

Intended to be used for killing whales.

Photo by Claudy.

round and round in the iron core produce heat. The rapid
changing of the magnetism of the iron also heats the iron.
It remained for Gramme, in France, to apply the proper
rgmedy. This remedy was an armature in which the coil
was wound on an iron ring, invented by an Italian, Pacinotti.
Gramme applied the principle discovered by Siemens to
Pacinotti' s ring, and produced the first practical dynamo for
strong currents. This was in 1868. A ring armature is
shown in Fig. 46. The first dynamo patented in the United
States is shown in Fig. 47. This dynamo is only a curiosity.

103

THE STORY OF GREAT INVENTIONS

The Drum Armature

An improvement in the Siemens armature was made four
years later by Von Hefner- Alteneck, an engineer in the em-
ploy of Siemens. This improvement consisted in winding
on the iron core a number of coils similar to the one coil of
the Siemens armature, but wound in different directions.
This is called the "drum armature" (Fig. 48). The heating

of the core is prevented
by building it up of a
number of thin iron
plates insulated from
one another and by air-
spaces within the core.
The insulation prevents
the small currents from
flowing around in the
core. The air - spaces
serve for cooling. The
drum armature was a
great improvement over
both the Siemens and
the Gramme armatures.
With the Siemens one-
coil armature there is a point in each revolution at
which there is no current. The current, therefore, varies
during each revolution of the armature from zero to full
strength. In the Gramme armature only half the wire,
the part on the outside of the ring, receives the full
effect of the magnetic field. The inner half is practically

104

FIG. 48 A DRUM ARMATURE, SHOWING

HOW AN ARMATURE OF FOUR
COILS IS WOUND

NINETEENTH-CENTURY INVENTIONS

useless, except to carry the current which is generated in
the outer half. Both these difficulties are avoided in the
drum armature. The dynamos of to-day are modifications
of the two kinds invented by Siemens and Gramme. Many
special forms have been designed for special kinds of work.

Edison's Compound- Wound Dynamo

Edison, in his work on the electric light and the electric
railway, made some important improvements in the dynamo.
The armature of a dynamo is usually turned by a steam-
engine. Edison found that much power was wasted in the
use of belts to connect the engine and the dynamo. He
therefore connected the engine direct to the dynamo,
placing the armature of the dynamo on the shaft of the
engine. He also used more powerful field - magnets than
had been used before. His greatest improvement, how-
ever, was in making the dynamo self-regulating, so that
the dynamo will send out the strength of current that is
needed. Such a dynamo will send out more current when
more lights are turned on. Whether it supplies current
for one light or a thousand, it sends out just the current
that is needed — no more, no less. It will do this if no hu-
man being is near. An attendant is needed only to keep
the machinery well oiled and see that each part is in work-
ing order. Edison brought about this improvement by his
improved method of winding. This method is known as
''compound winding."

To understand compound winding we must first under-
stand two other methods of winding. In the series wind-

105

THE STORY OF GREAT INVENTIONS

ing (Fig. 49), all the current generated in the armature flows
through the coils of the field-magnet. There is only one
circuit. The same current flows through the coils of the

FIG. 49 A SERIES-WOUND DYNAMO

magnet and through the outer circuit, which may contain
lights or motors. Such a dynamo is commonly used for
arc lights. It will not regulate itself. If left to itself it will
give less electrical pressure when more pressure is needed.
It requires a special regulator.

In the second form of winding the current is divided into

106

NINETEENTH-CENTURY INVENTIONS

two branches. One branch goes through the coils of the
field-magnet. The other branch goes through the line wire
for use in lights or motors. This is called the " shunt wind-
ing " (Fig. 50) . The shunt-wound dynamo is used for incan-
descent lights. It also requires a special regulator, for if left

FIG. 50 A SHUNT-WOUND DYNAMO

to itself it gives less electrical pressure when the pressure
should be kept the same.

The compound winding (Fig. 51), which was first used by
Edison, is a combination of the series and shunt windings.

107

THE STORY OF GREAT INVENTIONS

FIG. 51 A COMPOUND-WOUND DYNAMO

The current is divided into two branches. One branch goes
only through the field-coils. The other branch goes through
additional coils which are wound on the field-magnet, and
also through the external circuit. Such a dynamo can be
made self-regulating, so that it will give always the same
electrical pressure whatever the number of lamps or motors
thrown into the circuit. In maintaining always the same
pressure it of course supplies more or less current, accord-
ing to the amount of current that is needed. This is clear
if we compare the flow of electric current with the flow of
water. Open, a water-faucet and notice how fast the water
flows. Then open several other faucets connected with the
same water-pipe. Probably the water will not flow so fast
from the first faucet. That is because the pressure has
been lowered by the flow of water from the other faucets.
If we could make the water adjust its own pressure and
keep the pressure always the same, then the water would
always flow at the same rate through a faucet, no matter

108

FIG. 52 ONE OF EDISON'S FIRST DYNAMOS

Permission of Association of Edison Illuminating Companies.

THE STORY OF GREAT INVENTIONS

how many other faucets were opened. This is what hap-
pens in the Edison compound-wound dynamo. Turn on
one 1 6-candle-power carbon lamp. It takes about half an
ampere of current. Turn on a hundred lamps connected
to the same wires, and the dynamo of its own accord keeps
the pressure the same, and supplies fifty amperes, or half

FIG. 53 A DYNAMO MOUNTED ON THE TRUCK OF A RAILWAY CAR

The dynamo furnishes current for the electric lights in the car. When
the train is not running the current is furnished by a storage battery.

an ampere for each lamp. With this invention of Edison
the dynamo was practically complete, and ready to furnish
current for any purpose for which current might be needed.
Fig. 52 shows one of Edison's first dynamos. Fig. 53 shows
a dynamo used for lighting a railway coach.

NINETEENTH-CENTURY INVENTIONS

Electric Power

It has been said that the nineteenth century was the age
of steam, but the twentieth will be the age of electricity.
Before the end of the nineteenth century, however, electric
power had become a reality, and there remained only de-
velopment along practical lines.

We must turn to Oersted, Ampere, and Faraday to find
the beginning of electric power. In Oersted's experiment,
motion of a magnet was produced by an electric current.
Ampere found that electric currents attract or repel each
other, and this because of their magnetic action. Faraday
found that one pole of a magnet will spin round a wire
through which a current is flowing. Here was motion pro-
duced by an electric current. These great scientists dis-
covered the principles that were applied later by inventors
in the electric motor.

A number of motors were invented in the early years of
the century, but they were of no practical use. It was not
until after the invention of the Gramme and Siemens
dynamos that a practical motor was possible. It was found
that one of these dynamos would run as a motor if a current
were sent through the coils of the armature and the field-
magnet; in fact, the current from one dynamo may be
made to run another similar machine as a motor. Thus
the dynamo is said to be reversible. If the armature is
turned by a steam-engine or some other power, a current
is produced. If a current is sent through the coils, the
armature turns and does work. If the machine is used to
supply an electric current, it is a dynamo. If used to do

8 in

THE STORY OF GREAT INVENTIONS

work — as, for example, to propel a street -car and for that
purpose receives a current — it is a motor. The same ma-
chine may be used for either purpose. In practice there are
some differences in the winding of the coils of dynamos and
motors, yet any dynamo can be used as a motor and any
motor can be used as a dynamo. This discovery made it
possible to transmit power to a distance with little waste
as well as to divide the power easily. The current from
one large dynamo may light streets and houses, and at the
same time run a number of motors in factories or street-
cars at great distances apart. A central-station dynamo
may run the motors that propel hundreds of street-cars.
Dynamos at Niagara furnish current for motors in Buffalo
and other cities. One great scientist, who no doubt fore-
saw the wonders of electricity which we know so well
to-day, said that the greatest discovery of the nineteenth
century was that the Gramme machine is reversible.

The First Electric Railway

The electric railway was made possible by the invention
of the dynamo and the discovery that the dynamo is re-
versible. At the Industrial Exposition in Berlin in 1879
there was exhibited the first practical electric locomotive,
the invention of Doctor Siemens. The locomotive and its
passenger-coach were absurdly small. The track was cir-
cular, and about one thousand feet in length. This diminu-
tive railway was referred to by an American magazine as
"Siemens' electrical merry-go-round." But the electrical
merry-go-round aroused great interest because of the pos-
sibilities it represented (Fig. 54).

112

THE STORY OF GREAT INVENTIONS

The current was generated by a dynamo in Machinery
Hall, this dynamo being run by a steam-engine. An exact-
ly similar dynamo mounted on wheels formed the locomotive.
The current from the dynamo in Machinery Hall was used
to run the other as a motor and so propel the car. The
rails served to conduct the current. A third rail in the
middle of the track was connected to one pole of the dynamo
and the two outer rails to the other pole. A small trolley
wheel made contact with the third rail. The rails were not
insulated, but it was found that the leakage current was
very small, even when the ground was wet.

The success of this experiment aroused great interest,
not only in Germany, but in Europe and America. America's
greatest inventor, Edison, took up the problem. Edison em-
ployed no trolley line or third rail, but only the two rails of
the track as conductors, sending the current out through one
rail and back through the other. Of course, this meant that
the wheels must be insulated, so that the current could flow
from one rail to the other only through the coils of the motor.

As in Siemens' experiment, the motor was of the same
construction as the dynamo. The rails were not insulated,
and it was found that, even when the track was wet, the
loss of electric current was not more than 5 per cent. Edison
found that he could realize in his motor 70 per cent, of the
power applied to the dynamo, whereas the German inventor
was able to realize only 60 per cent. The improvement was
largely due to the improved winding. Edison was the first
to use in practical work the compound-wound dynamo, and
this was done in connection with his electric railway. Fig.
55 shows Edison's first electric locomotive.

114

THE STORY OF GREAT INVENTIONS

The question of gearing was a troublesome one. The
armature shaft of the motor was at first connected by
friction gearing to the axle of two wheels of the locomotive.
Later a belt and pulleys were used. An idler pulley was
used to tighten the belt. When the motor was started and
the belt quickly tightened the armature was burned out.
This happened a number of times. Then Mr. Edison brought
out from the laboratory a number of resistance - boxes,
placed them on the locomotive, and connected them in
series with the armature. These resistances would permit
only a small current to flow through the motor as it was
starting, and so prevent the burning-out of the armature
coils. The locomotive was started with the resistance-boxes
in circuit, and after gaining some speed the operator would
plug the various boxes out of circuit, and in that way in-
crease the speed. When the motor is running there is a
back-pressure, or a pressure that would cause a current to
flow in the opposite direction from that which is running
the motor. Because of this back - pressure the current
which actually flows through the motor is small, and the
resistance-boxes may be safely taken out of the circuit.
Finding the resistance - boxes scattered about under the
seats and on the platform as they were a nuisance, Mr. Edison
threw them aside, and used some coils of wire wound on the
motor field-magnet which could be plugged out of the circuit
in the same way as the resistance -boxes. This device of Edi-
son's was the origin of the controller, though in the controller
now used on street-cars not only is the resistance cut out as
the speed of the car increases, but the electrical connections
of the motor are changed in such a way as to increase its

116

THE STORY OF GREAT INVENTIONS

speed gradually. Fig. 56 shows Edison's first passenger loco-
motive.

The news of the little electric railway at the Industrial
Exposition in Berlin was soon noised abroad, and the Ger-
man inventor received inquiries from all parts of the world,
indicating that efforts would be made in other countries
to develop practical electrical railways. The firm of Sie-
mens & Halske therefore determined to build a line for
actual traffic, not for profit, but that Germany might have
the honor of building the first practical electric railway. The
line was built between Berlin and Lichterfelde, a distance
of about one and a half miles. A horse-car seating twenty-
six persons was pressed into service. A motor was mounted
between the axles, and a central- station dynamo exactly
like the motor was installed. As in Edison's experimental
railway, the two rails of the track were used to carry the
current. This electric line replaced an omnibus line, and
was immediately used for regular traffic, and thus the electric
railway was launched upon its remarkable career. The first
electric car used for commercial service is shown in Fig. 57.

Electric Lighting

From the time when the night-watchman carried a
lantern to the time of brilliantly lighted streets was less
than a century. It was a time when the rapid growth of
railways and commerce brought about a rapid growth of
cities, and with the growth of cities the need of illumina-
tion. Factories must run at night to meet the world's de-
mands. Commerce cannot stop when the sun sets. The
centres of commerce must have light.

118

NINETEENTH-CENTURY INVENTIONS

During this time scientists were at work in their labora-
tories developing means for producing a high vacuum. They
were able to pump the air out of a glass bulb until less than
a millionth part of the air remained. They little dreamed
that there was any connection between the high vacuum
and the problem of lighting. Discoverers were at work

FIG. 57 FIRST COMMERCIAL ELECTRIC RAILWAY

An old horse-car converted into an electric car.

bringing to light the principles now utilized in the dynamo.
In the fulness of time these factors were brought together
to produce an efficient system of lighting.

For a time gas replaced the lantern of the night-watchman,
only to yield the greater portion of the field to its rival,
electricity.

119

THE STORY OF GREAT INVENTIONS

The first efforts were in the direction of the arc light.
From the earliest times the light given out by an electric
spark had been observed. It was the aim of inventors to
produce a continuous spark that should give out a brilliant
light. It was thought for a time that the electric battery
would solve the problem, but the cost of the battery cur-
rent was too great. Again we are indebted to Faraday, for
it was the dynamo that made electric lighting possible.

An arc light is produced by an electric current flowing
across a gap between two sticks of carbon. The air offers
very great resistance to the flow of electric current across
this gap. Now whenever an electric current flows through
something which resists its flow, heat is produced. The
high resistance of the air-gap causes such intense heat that
the tips of the carbons become white hot and give out a
brilliant light. If examined through a smoked glass a beau-
tiful blue arc of carbon vapor may be seen between the
carbon tips. If the current flows in one direction only,
one of the carbons, the positive, becomes hotter and brighter
than the other.

In 1878 the streets of Paris were lighted with the "Jab-
lochkoff candle," a form of arc light supplied with current
by the Gramme machine. In the same year the Brush
system of arc lighting was given to the public. This was
the beginning of our present system of arc lighting.

The electric arc is suitable for lighting streets and for
large buildings, but cannot be used for lighting houses.
The light is too intense. One arc would furnish enough
light for a number of houses if the light could be divided
So that there might be just the right amount of light in

120

NINETEENTH-CENTURY INVENTIONS

each room. But this is impossible with the electric arc.
The Edison system of incandescent lighting was required to
solve the problem of lighting houses by electricity.

In 1880 the Edison system was brought out for commercial
use. Edison's problem was to produce a light that could
be divided into a number of small lights, and one that
would require less attention than the arc light. He tried
passing a current through platinum wire enclosed in a
vacuum. This gave a fairly good light, but was not wholly
satisfactory. He sat one night thinking about the problem,
unconsciously fingering a bit of lampblack mixed with tar
which he had used in his telephone. Not thinking what he
was doing, he rolled this mixture of tar and lampblack into
a thread. Then he noticed what he had done, and the
thought occurred to him: ''Why not pass an electric cur-
rent through this thread of carbon?" He tried it. A faint
glow was the result. He felt that he was on the right track.
A piece of cotton thread must be heated in a furnace in an
iron mold, which would prevent the thread from burning
by keeping out the air. Then all the other elements that
were in the thread would be driven out and only the carbon
remain. For three days he worked without sleep to pre-
pare this carbon filament. At the end of two days he suc-
ceeded in getting a perfect filament, but when he attempted
to seal it in the glass bulb it broke. He patiently worked
another day, and was rewarded by securing a good carbon
filament sealed in a glass globe. He pumped the air out of
this globe, sealed it, and sent a current through the carbon
thread. He tried a weak current at first. There was a
faint glow. He increased the current. The thread glowed

121

NINETEENTH-CENTURY INVENTIONS

more brightly. He continued to increase the current until
the slender thread of carbon, which would crumble at a
touch, was carrying a current that would melt a wire of
platinum strong enough to support a weight of several
pounds. The carbon gave a bright light. He had found
a means of causing the electric current to furnish a large
number of small lights. Fig. 58 is an excellent photograph

FIG. 59 — EDISON'S FAMOUS HORSESHOE PAPER-FILAMENT LAMP OF 1870

of Edison at work in his laboratory. Fig. 59 shows some of
Edison's first incandescent lamps. He next set out in
search of the best kind of carbon for the purpose. He car-
bonized paper and wood of various kinds — in fact, every-
thing he could find that would yield a carbon filament. He
tried the fibres of a Japanese fan made of bamboo, and
found that this gave a better light than anything he had
tried before. He then began the search for the best kind

123

THE STORY OF GREAT INVENTIONS

of bamboo. He learned that there are about twelve hun-
dred varieties of bamboo. He must have a sample of every
variety. He sent men into every part of the world where
bamboo grows. One man travelled thirty thousand miles
and had many encounters with wild beasts in his search for
the samples of bamboo. At last a Japanese bamboo was
found that was better than any other. The search for the
carbon fibre had cost about a hundred thousand dollars.
Later it was found that a "squirted filament" could be
made that worked as well as the bamboo fibre. This was
made by dissolving cotton wool in a certain solution, and
then squirting this solution through a small hole into a
small tank containing alcohol. The alcohol causes the sub-
stance to set and harden, and thus forms a carbon thread
the size of the hole. Fig. 60 shows the first commercial
electric -lighting plant, which was installed on the steamship
Columbia in 1880.

The carbon thread in the incandescent light is heated to
a white heat, and because it is so heated it gives out light.
In air such a tiny thread of white-hot carbon would burn
in a fraction of a second. The carbon must be in a vacuum,
and so the air is pumped out of the light bulb with a special
kind of air-pump invented not long before Edison began
his work on the electric light. This pump is capable
of taking out practically all the air that was in the bulb.
Perhaps a millionth part of the original air remains.

A great invention is never completed by one man. It
was to be expected that the electric light would be im-
proved. A number of kinds of incandescent light have been
devised, using different kinds of filaments and adapted to

124

NINETEENTH-CENTURY INVENTIONS

FIG. 60 FIRST COMMERCIAL EDISON ELECTRIC-LIGHTING PLANT; INSTALLED

ON THE STEAMSHIP " COLUMBIA " IN MAY, l88o

a variety of uses. The original Edison carbon lamp, how-
ever, continues in use, being better adapted to certain pur-
poses than the newer forms.

The mercury vapor light deserves mention as a special
form of arc light. In the ordinary arc light the arc is
formed of carbon vapor, and the light is given out from the
tips of the white-hot carbons. In the mercury vapor light
the light is given out from the mercury vapor which forms
the arc. This arc may be of any desired length, and yields
a soft, bluish-white light which is a near approach to day-
light.

125

THE STORY OF GREAT INVENTIONS

The Telegraph

The need of some means of giving signals at a distance
was early felt in the art of war. Flag signals such as are
now used by the armies and navies of the world were intro-
duced in the middle of the seventeenth century by the
Duke of York, admiral of the English fleet, who afterward
became James II. of England. Other methods of com-
municating at a distance were devised from time to time,
but the distance was only that at which a signal could be
seen or a sound heard. No means of communicating over
very long distances was possible until the magnetic action
of an electric current was discovered. When Oersted's dis-
covery was made known men began to think of signalling to
a distance by means of the action of an electric current on
a magnetic needle. A current may be sent over a very
long wire, and it will deflect a magnetic needle at the other
end. The movements of the needle may be controlled by
opening and closing the circuit, and a system of signals or
an alphabet may be arranged. A number of needle tele-
graphs were invented, but they were too slow in action.
Two other great inventions were needed to prepare the
way for the telegraph. One was the electromagnet in the
form developed by Professor Henry, a horseshoe magnet
with many turns of silk-covered wire around the soft-iron
core, so that a very feeble current will produce a magnet
strong enough to move an armature of soft iron. The mag-
net has this strength because the current flows so many
times around the iron core. Another need was that of a
battery that could be depended on to give a constant cur-

126

NINETEENTH-CENTURY INVENTIONS

rent for a considerable length of time. This need was met
by the Daniell cell.

The electromagnet made the telegraph possible. The
locomotive made it a necessity. Without the telegraph it
would be impossible to control a railway system from a
central office. A train after leaving the central station
would be like a ship at sea before the invention of the wire-
less telegraph. Nothing could be known of its movements
until it returned. The need of a telegraph was keenly felt
in America when the new republic was extended to the
Pacific Coast. An English statesman said, after the United
States acquired California, that this marked the end of the
great American Republic, for a people spread over such a
vast area and separated by such natural barriers could
not hold together. He did not know that the iron wire
of the telegraph would bind the new nation firmly to-
gether.

The Morse telegraph system now in use throughout the
civilized world was made possible by the work of Sturgeon
and Henry. Sturgeon's electromagnet might have been
used for telegraphy through very short distances, but
Henry's magnet, with its coils of many turns of insulated
wire, was needed for long-distance signalling. In one of
the rooms of the Albany Academy, Professor Henry caused
an electromagnet to sound a bell when the current was
transmitted through more than a mile of wire. This might
be called the first electromagnetic telegraph. But the ap-
plication to actual practice was made by Morse, and the
man who first makes the practical application of a prin-
ciple is the true inventor.

9 127

THE STORY OF GREAT INVENTIONS

In 1832, on board the packet-ship Sully, Samuel F. B.
Morse, an American artist, forty-one years of age, was re-
turning from Europe. In conversation a Doctor Jackson
referred to the electrical experiments of Ampere, which he
had witnessed while in Europe, and, in reply to a question,
said that electricity passes instantaneously over any known
length of wire. The thought of transmitting words by
means of the electric current at once took possession of the
artist's mind. After many days and sleepless nights he
showed to friends on board the drawings and notes he had
made of a recording telegraph.

In New York, in a room provided by his brothers, he
gave himself up to the working-out of his idea, sleeping
little and eating the simplest food. Receiving an appoint-
ment as professor in the University of the City of New
York, he moved to one of the buildings of that university
and continued his experiments in extreme poverty, and at
times facing starvation, as his salary depended on the tui-
tion fees of his pupils.

A story told by one of his pupils describes his condition
at the time.

"I engaged to become one of Morse's pupils. He had
three others. I soon found that the professor had little
patronage. I paid my fifty dollars; that settled one quar-
ter's tuition. I remember, when the second was due, my
remittance from home did not come as expected, and one
day the professor came in and said, courteously:

14 * Well, Strother, my boy, how are we off for money?'
"Why, professor, I am sorry to say I have been disap-
pointed; but I expect a remittance next week.'

128

NINETEENTH-CENTURY INVENTIONS

"'Next week!' he repeated, sadly; 'I shall be dead by
that time.'

'"Dead, sir?'

"'Yes; dead by starvation!'

"I was distressed and astonished. I said, hurriedly:
'Would ten dollars be of any service?'

"'Ten dollars would save my life; that is all it would
do.'"

The money was paid, all the student had, and the two
dined together. It was Morse's first meal in twenty-four
hours.

The Morse telegraph sounder (Fig, 61) consists of an

FIG. 6l A TELEGRAPH SOUNDER

electromagnet and a soft-iron armature. When no current
is flowing the armature is held away from the magnet by a
spring. When the circuit is closed a current flows through

129

THE STORY OF GREAT INVENTIONS

the coils of the magnet and the armature is attracted, caus-
ing a click. When the circuit is broken the spring pulls the
armature away from the magnet, causing another click.
The circuit is made and broken by means of a key at the
other end of the line. In Morse's first instrument (Fig. 62)
the armature carried a pen, which was drawn across a rib-
bon of paper when the armature was attracted by the magnet.
If the pen was held by the magnet for a very short time, a
dot was made ; if for a longer time, a dash. The pen was
soon discarded, and the message taken by sound only.
The Morse alphabet now in use was devised by a Mr. Vail,
who assisted Morse in developing the telegraph. The
thought occurred to Mr. Vail that he could get help from
a printing-office in deciding the combinations of dots and
dashes that should be used for the different letters. The
letters requiring the largest spaces in the type-cases are
the ones that occur most frequently, and for these letters
he used the simplest combinations of dots and dashes.

Morse repeatedly said that, if he could make his telegraph
work through ten miles, he could make it work around the
world. This promise of long-distance telegraphy he ful-
filled by the use of the relay. The relay works in the same
way as the sounder. The current coming over a long line
may be too feeble to produce a click that can be easily
heard, yet strong enough to magnetize the coils of the relay
and cause the armature to close another circuit. This
second circuit includes the sounder and a battery in the
same station as the sounder, which we shall call ''the local
battery." The relay simply acts as a contact key, and closes
the circuit of the local battery. Thus the current from the

130

FIG. 62 MORSE'S FIRST TELEGRAPH INSTRUMENT

A pen was attached to the pendulum and drawn across the strip of
paper by the action of the electromagnet. The lead type shown in the
lower right-hand corner was used in making electrical contact when send-
ing a message. The modern instrument shown in the lower left-hand cor-
ner is the one that sent a message around the world in 1896.

Photo by Claud y.

THE STORY OF GREAT INVENTIONS

local battery flows through the sounder and produces a
loud click. Sometimes a relay is used to control a second
very long circuit. At the farther end of the second circuit
may be a sounder or a second relay which controls a third
circuit. Any number of circuits may be thus connected
by means of relays. This is a form of repeating system
used for telegraphing over very long distances. Fig. 63
shows a circuit with relay and sounder.

In the telegraphic circuit only one connecting wire is

O =r

Sounder1

Line wire

/?<?/,

FIG. 63 A TELEGRAPHIC CIRCUIT WITH RELAY AND SOUNDER

132

NINETEENTH-CENTURY INVENTIONS

needed. The earth, being a good conductor of electricity,
is used as part of the circuit. It is necessary, therefore, to
make a ground connection at each end of the line, the in-
struments being connected between the line wire and the

Sounder

^^ Battery

FIG. 64 A SIMPLE TELEGRAPHIC CIRCUIT

Two keys are shown at K K, and two switches at 5 S. When one key
is to be used the switch at that station must be open, and the switch
at the other station closed.

earth. For long-distance telegraphy a current from a
dynamo is used instead of a battery current. Fig. 64 shows
a simple telegraphic circuit.

A telegraphic message travels with the speed of light,
for the speed of electricity and the speed of light are the
same. A telegraphic signal would go more than seven
times around the earth in one second if it travelled on one
continuous wire. The relays that must be used, however,
cause some delay.

'33

THE STORY OF GREAT INVENTIONS

In 1835 Morse's experimental telegraph was completed,
and in 1837 & was exhibited to the public, but seven years
more passed before a line was established for public use.
Aid from Congress was necessary. Going to Washington,
Morse exhibited his instrument in the halls of the Capitol,
sending messages through ten miles of wire wound on a
reel. The invention was ridiculed, but the inventor did not
despair. A bill for an appropriation to establish a tele-
graphic line between Washington and Baltimore passed the
House by a small majority. The last day of the session
came. Ten o'clock at night, two hours before adjourn-
ment, and the Senate had not acted. A senator advised
Morse to go home and think no more of it, saying that the
Senate was not in sympathy with his project. He went
to his hotel, counted his money, and found that he could
pay his bill, buy his ticket home, and have thirty-seven
cents left. All through his work he had firmly believed
that a Higher Power was directing his work, and bringing
to the world, through his invention, a new and uplift-
ing force ; and so when all seemed lost he did not lose
heart.

In the morning a friend, Miss Ellsworth, called and of-
fered her congratulations that the bill had been passed by
the Senate and thirty thousand dollars appropriated for
the telegraph. Being the first to bring the news of his
success, Mr. Morse promised her that the first message over
the new line should be hers. In about a year the line was
completed, and Miss Ellsworth dictated the now famous
message : ' ' What hath God wrought !"

Soon afterward the Democratic Convention, in session in

134

NINETEENTH-CENTURY INVENTIONS

Baltimore, received a telegraphic message from Senator
Silas Wright, in Washington, declining the nomination for
the Vice-Presidency, which had been tendered him. The
convention refused to accept a message sent by telegraph,
and sent a committee to Washington to investigate. The
message was confirmed, and Morse and his telegraph be-
came famous. Fig. 65 shows the first telegraph instrument
used for commercial work.

The desire to telegraph across the ocean came with the

FIG. 65 FIRST TELEGRAPH INSTRUMENT USED FOR COMMERCIAL WORK

Photo by Claudy.

introduction of the telegraph on land. Bare wires in the
air with glass insulators at the poles are used for land teleg-
raphy, but bare wires in the water could not be used, for
ocean water will conduct electricity. Something was needed
to cover the wire, protect it from the water, and prevent
the escape of the electric current. Just when it was needed

THE STORY OF GREAT INVENTIONS

such a substance was discovered. In 1843, when Morse was
working on his telegraph, it was found that the juice of a cer-
tain kind of tree growing in the Malayan Archipelago formed
a substance somewhat like rubber but more durable, and
especially suited to the insulation of wires in water. This
substance is gutta-percha. Ocean cables are made of a
number of copper wires, each wire covered with gutta-
percha, the wires twisted together and protected with tarred
rope yarn and an outer layer of galvanized iron wires. The
earth is used for the return circuit, as in the land telegraph.

Duplex Telegraphy

The telegraph was a success, but many improvements
were yet to be made. Economy of construction was the
thing sought for. To make one wire do the work of two
was accomplished by the invention of the duplex system.
In duplex telegraphy two messages may be sent in opposite
directions over the same wire at the same time. Let us
take a look at some of the methods by which this is accom-
plished.

One method with a long name but very simple in its
working is the differential system (Fig. 66). In the differ-
ential system the current from the home battery divides
into two branches passing around the coils of the electro-
magnet in opposite directions. Now if these two branches
are so arranged that the currents flowing through them are
equal, the relay will not be magnetized, because one cur-
rent would tend to make the end A a north pole, and the
pther current would tend to make the same end a south

136

THE STORY OF GREAT INVENTIONS

pole. The result is that the relay coil is not magnetized,
and does not attract the armature. But the current from
the distant battery comes over one of these branches only,
and will magnetize the relay. Hence, with a similar ar-
rangement at the second station, two messages may be
sent at the same time in opposite directions.

Another method not quite so simple in principle is the
bridge method. When the key at station A (see Fig. 67)
is closed, the current from the battery at station A divides
at C, and if the resistances i and 2 are equal, and the re-
sistance 3 is equal to the resistance of the line, no current
will flow through the sounder. But if a current comes over
the line from the distant station this current divides at D,
and a part goes through the sounder, causing it to click.
The sounder is not affected, therefore, by the current from
the home battery, but is affected by the current from the
distant battery. Therefore, a message may be sent and
another received at the same time. If there is a similar
arrangement at the other station, two messages may travel
over the line in opposite directions at the same time.

The differential method is used in land telegraphy, the
bridge method almost exclusively in submarine telegraphy.
The next step was a quadruplex system, by means of which
four messages may be transmitted over one wire at the
same time. The first quadruplex system was invented by
Edison in 1874, and in four years it saved more than half
a million dollars. Other systems have been invented which
make it possible to send even a larger number of messages
at one time over a single wire.

THE STORY OF GREAT INVENTIONS

The Telephone

The idea of "talking by telegraph" began to grow in the
minds of inventors soon after the Morse instrument came
into use. The sound of the voice causes vibrations in the
air. This is simply shown in the string telephone. This
telephone is made by stretching a thin membrane, such as
thin sheepskin, or gold-beaters' skin, over a round frame
of wood or metal. , Two such instruments are connected by
a string, the end of the string being fastened to the middle
of the stretched membrane. The sound of the voice causes
this membrane to vibrate. As the membrane moves rapid-
ly back and forth, it pulls and releases the string, and so
causes the membrane at the other end to vibrate and give
out the sound. This is the actual carrying of the sound
vibrations along the string. In the telephone it is not
sound vibrations but an electric current that travels over
the line wire. The telephone message, therefore, travels
with the speed of electricity, not with the speed of sound.
If it travelled with the speed of sound in air, a message
spoken in Chicago would be heard in New York one hour
later; but we know that a message spoken in Chicago may
be heard in New York the instant it is spoken.

The telephone, like the telegraph, depends on the electro-
magnet. The thought of inventors at first was to make
the vibrations of a thin membrane, caused by the sound of
the voice, open and close a telegraphic circuit. An electro-
magnet at the other end of the line would cause a thin
membrane with a piece of soft iron attached to it to vibrate,
just as the magnet in the telegraph receiver pulls and re-

149

NINETEENTH-CENTURY INVENTIONS

leases the soft-iron armature as the circuit is made and
broken. The thin membrane caused to vibrate in this way
would give out the sound. A telephone on this principle
was invented by Philip Reis, a schoolmaster in Germany,
The transmitter was carved out of wood in the shape of a
human ear, the thin membrane being in the position of the
ear-drum. Musical sounds and even words were trans-
mitted by this telephone, but it could never have been
successful as a practical working telephone. The mem-
brane in the receiver would vibrate with the same speed
as the membrane in the transmitter, but sound depends
on something more than speed of vibration.

The Bell telephone, as known to-day, began with a study
of the human ear. Alexander Graham Bell was a teacher
of the deaf. His aim was to teach the deaf to use spoken
language, and for this purpose he wished to learn the nature
of the vibrations caused by the voice. His plan was to
cause the ear itself to trace on smoked glass the waves pro-
duced by the different letters of the alphabet, and to use
these tracings in teaching the deaf. Accordingly, a human
ear was mounted on a suitable support, the stirrup-bone
removed, leaving two bones attached, and a stylus of wheat
straw attached to one of the bones. The ear-drum, caused
to vibrate by the sound, moved the two small bones and
the pointer of straw, so that when he sang or talked to the
ear delicate tracings were made on the glass.

This experiment suggested to Mr. Bell that a membrane
heavier than the ear-drum would move a heavier weight.
If the ear-drum, no thicker than tissue-paper, could move
the bones of the ear, a heavier membrane might vibrate

141

THE STORY OF GREAT INVENTIONS

a piece of iron in front of an electromagnet. He was at the
same time devising a telegraph for transmitting messages
by means of musical sounds. In this telegraph he was
using an electromagnet in the transmitter and another
electromagnet in the receiver. He attached the soft-iron
armature of each electromagnet to a stretched membrane
of gold-beaters' skin, expecting that the sound of his voice
would cause the membrane of the transmitter to vibrate,
and that, by means of the electromagnets, the membrane
of the receiver would be made to vibrate in the same way
(Fig. 68). At first he was disappointed, but after making

FIG. 68 FIRST BELL TELEPHONE RECEIVER AND TRANSMITTER

The receiver is on the left in the picture. A thin membrane of gold-
beaters' skin tightly stretched and fastened with a cord can be seen on
the end of the transmitter and of the receiver. An electromagnet is also
shown over each membrane. This thin membrane, with a piece of soft iron
attached, was used in place of the soft-iron disk of the modern receiver.

142

NINETEENTH-CENTURY INVENTIONS

some changes in the armatures a distinct sound was heard
in the receiver. Later the membrane was discarded, and
a thin iron disk used with better effect.

The story of Bell's struggles might seem like the repetition
of the life story of many another great inventor. He knew

FIG. 69 A TELEPHONE RECEIVER

that he had discovered something of great value to the
world. He devoted his time to the perfecting of the tele-
phone, neglecting his professional work and finally giving
it up, that he might give his whole time to his invention.
He was forced to endure poverty and ridicule. He was
called "a crank who says he can talk through a wire."
Men said his invention could never be made practical.
Even after he succeeded in finding a few purchasers and
some of the telephones were in actual use, people were slow
to adopt it. The idea of talking at a piece of iron and hear-
ing another piece of iron talk seemed like a kind of witchcraft.
In the telephone we see another use of the electromagnet.
A very thin iron disk near the poles of an electromagnet
forms the telephone receiver (Fig. 69). An electric current
travels over the telephone wire. If the current grows
10 143

THE STORY OF GREAT INVENTIONS

stronger, the magnet is made stronger and pulls the disk
toward it. If the current grows weaker, the magnet be-
comes weaker and does not pull so hard on the disk. The
disk then springs back from the magnet. If these changes
take place rapidly the disk moves back and forth rapidly
and gives out a sound. The sound of the voice at the
other end of the line sets the disk in the mouthpiece vibrat-
ing. The vibrations of this disk cause the changes in the
electric current flowing over the line-wire, and the changes
in the electric current cause the disk of the receiver to vi-
brate in exactly the same way as the disk at the mouth-
piece. Thus the words spoken into the mouthpiece may
be heard at the receiver.

The transmitter used by Bell was like the receiver. Two
receivers from the common telephone connected by two
wires may be used as a telephone without batteries. Fig. 70
shows a complete telephone made of two receivers con-
nected by two wires. The disk in one receiver which is now
used as a transmitter is made to vibrate by the sound of the
voice. Now when a piece of iron moves back and forth in
a magnetic field it strengthens and weakens the field. So
the magnetic field in the transmitter is rapidly changed by
the movement of the iron disk. Now we have found that
whenever a coil of wire is in a changing magnetic field a
current is induced in the coil. The small coil in the trans-
mitter, therefore, has a current induced in it. We have also
found that when the magnetic field is made stronger the
induced current flows in one direction, and when the field
is made weaker the current flows in the opposite direction.
Since the field in the transmitter is made alternately stronger

144

NINETEENTH-CENTURY INVENTIONS

and weaker, the current in the coil flows first in one direc-
tion,- then in the opposite direction — that is, we have an
alternating current. This alternating current, of course,

y^.*aa£
fc/« _Tf

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FIG. 70 TWO RECEIVERS USED AS A COMPLETE TELEPHONE

flows over the line-wire and through the coil in the receiver.
In the receiver the alternating current will alternately
strengthen and weaken the magnetic field, and as it does so
the pull of the magnet on the iron disk is strengthened and
weakened. The iron disk in the receiver, therefore, vi-
brates in exactly the same way as the disk in the transmit-
ter, and so gives out a sound just like that which is acting
on the transmitter.

THE STORY OF GREAT INVENTIONS

In the Blake transmitter, which is now commonly used,
the disk moves a pencil of carbon which presses against
another pencil of carbon. This varies the pressure between
the two pencils of carbon. A battery current flows through
the two carbons, and as the pressure of the carbons changes
the strength of the current changes. When the carbons are
pressed together more closely the current is stronger. When
the pressure is less the current is weaker. We have, then,
a varying current through the carbons. This current flows

through the primary coil of an
induction-coil, the secondary
being connected to the line-
wire. Now a current of vary-
ing strength in the primary
induces an alternating current
in the secondary. We have,
DIAPHRAGM then, an alternating current
flowing over the line -wire.
This alternating current acts
on the magnetic field of the
receiver in the way described
before, causing the disk in the
receiver to vibrate and give
out the sound.

For long-distance work a
carbon -dust transmitter (Fig.
71) is used. In this there are
many granules of carbon, so
that instead of two carbon-points in contact there are many.
This makes the transmitter more sensitive.

146

CARBON
DUST

FIG. 71 CARBON-DUST TRANS-
MITTER

NINETEENTH-CENTURY INVENTIONS

The strength of current required for the telephone is very
small. To transmit a telephone message requires less than
a hundred -millionth part of the current required for a tele-
graphic message. The work done in lifting the telephone
receiver a distance of one foot, if changed into an alternating
current, would be sufficient to keep up a sound in the re-
ceiver for a hundred thousand years. Because of its extreme
sensitiveness the telephone requires a complete wire circuit.
The earth cannot be used for the return circuit, as in the
case of the telegraph. Disturbances in the earth, vibra-
tion, leakage currents from trolley lines, and so forth, would
interfere seriously with the action of the telephone.

When the telephone was invented it was commonly re-
marked that it could not take the place of the telegraph
in commerce, for the latter gave the merchant some evidence
of a business transaction, while the telephone left no sign.
There was a time when men feared to trust each other, but
now large business deals are made by telephone; products
of the farm, the factory, and the mine are bought and sold
in immense quantities without a written contract or even
the written evidence of a telegram. Thus the telephone has
developed a spirit of business honor.

The Phonograph

The phonograph grew out of the telephone. It is said
to be the only one of Edison's inventions that came by
accident, yet only a man of genius would have seen the
meaning of such an accident. He was singing into the
mouthpiece of a telephone when the vibrations of the disk

THE STORY OF GREAT INVENTIONS

caused a fine steel point to pierce one of his fingers held just
behind the disk. This set him to thinking. If the sound
of his voice could cause the disk to vibrate with force
enough to pierce the skin, would it not make impressions
on tin-foil, and so make a record of the voice that could
be reproduced by passing the point rapidly over the same
impressions? He gave his assistants the necessary in-
structions, and soon the first phonograph was made.

This disk in the phonograph is set in vibration by sound
vibrations in the air in the same way as the disk in the tele-
phone transmitter. Attached to the disk is a needle-point
which, of course, vibrates with the disk. If a cylinder with
a soft surface is turned rapidly under the steel point as it-
vibrates, impressions are made in the cylinder correspond-
ing to the movements of the disk. The cylinder must move
forward as it turns, so that its path will be a spiral. If, now,
the stylus is placed at the starting-point and the cylinder
turned rapidly the stylus will move rapidly up and down
as it goes over the indentations in the cylinder, and so cause
the metal disk to vibrate and give out a sound like that
received at first. In the earliest phonographs the cylinder
was covered with tin-foil. Later the so-called "wax rec-
ords" came into use. These cylinders are not made of wax,
but of very hard soap. Fig. v 72 shows an instrument in
which the sound of the voice caused a pencil-point to trace
a wavy line on a cylinder. This instrument may be called
a forerunner of the phonograph. Fig. 73 shows Edison's
first phonograph with a modern instrument placed beside
it for comparison.

THE STORY OF GREAT INVENTIONS

Gas-Engines

Cannons are the oldest gas-engines. Indeed, the prin-
ciple of the cannon is the same as that of the modern gas-
engine, the piston in the engine taking the place of the
cannon-ball. The power in each case is obtained by ex-
plosion — in the cannon the explosion of powder, in the
engine the explosion of a mixture of air and gas. Powder-
engines with pistons were proposed in the seventeenth cen-

FIG. 73 EDISON S FIRST PHONOGRAPH AND A MODERN INSTRUMENT

Photo by Claudy.

.tury, and some were actually built, but it proved too diffi-
cult to control them, and the idea of the gas-engine was
abandoned for more than a hundred years.

The discovery of coal-gas near the close of the eighteenth
century gave a new impetus to the gas-engine. John Bar-
ber, an Englishman, built the first actual gas-engine. He

150

NINETEENTH-CENTURY INVENTIONS

used gas distilled from wood, coal, or oil. The gas, mixed
with the proper proportion of air, was introduced into a tank
which he called the exploder. The mixture was fired and
issued out in a continuous stream of flame against the
vanes of a paddle-wheel, driving them round with great
force.

In 1804 Lebon, a French engineer, was assassinated, and
the progress of the gas-engine set back a number of years,
for this engineer had proposed to compress the mixture of
gas and air before firing, and to fire the mixture by an
electric spark. This is the method used in gas-engines
to-day.

The first practical working gas-engine was invented by
Lenoir, a Frenchman, in 1860. From this time to the end
of the century the gas-engine developed rapidly, receiving
a new impulse from the increasing demand for the motor-
car.

The engine of the German inventors, Otto and Langen,
brought out in 1876, marked the beginning of a new era.
The greater number of engines used in automobiles to-day
are of the kind known as the Otto cycle, or four-cycle,
engine. This engine is called four-cycle because the piston
makes four strokes for every explosion. There is one stroke
to admit the mixture of gas and air to the cylinder, another
to compress the gas and air, at the beginning of the third
stroke the explosion takes place, and in the fourth stroke the
burned-out gases are driven out of the cylinder. The work-
ing of the four-cycle gas-engine is made clear in Figs. 74,
75, 76, and 77.

In such a gas-engine the power .is applied to the piston

FIG. 74 FIRST STROKE. GAS AND AIR ADMITTED TO THE CYLINDER

FIG. 75 SECOND STROKE. MIXTURE OF GAS AND AIR COMPRESSED

FIG. 76 THIRD STROKE. THE MIXTURE IS EXPLODED AND EXPANDS,

DRIVING THE PISTON FORWARD

FIG. 77 FOURTH STROKE, EXHAUST. THE BURNED-OUT MIXTURE OF

GAS AND AIR EXPELLED FROM THE CYLINDER

THE FOUR-CYCLE GAS-ENGINE

NINETEENTH-CENTURY INVENTIONS

only in one stroke out of every four, while in the steam-
engine the power is applied at every stroke. It would seem,
therefore, that a steam-engine would do more work than a
gas-engine for the same amount of heat, but such is not the
case; in fact, a good gas-engine will do about twice as
much work as a good steam-engine for the same amount of
fuel. The reason is that the steam-engine wastes its heat.
Heat is given to the condenser, to the iron of the boiler, to
the connecting pipes and the air around them, while in the
gas-engine the heat is produced in the cylinder by the ex-
plosion and the power applied directly to the piston-head.
More than this, a steam-engine when at rest wastes heat;
there must be a fire under the boiler if the engine is to be
ready for use on short notice. When a gas-engine is at rest
there is no fire, nothing is being used up, and yet the engine
can be started very quickly. A gas-engine can be made
much lighter than a steam-engine of the same horse-power.
The automobile and the flying-machine require very light
engines. Without the gas-engine the automobile would have
remained imperfect and crude, while the flying-machine
would have been impossible.

In a two-cycle gas-engine there is an explosion for every
two strokes of the piston, or one explosion for every revo-
lution of the crank-shaft. During one stroke the mixture
of gas and air on one side of the piston is compressed and
a new mixture enters on the opposite side of the piston.
At the end of this stroke the compressed mixture is ex-
ploded, and power is applied to the piston during about
one-fourth of the next stroke. During the remainder of
the second stroke the burned-out gas escapes, and the fresh

THE STORY OF GREAT INVENTIONS

mixture passes over from one side of the piston to the other
ready for compression. The two-cycle engine is simpler in
construction than the four-cycle, having no valves. It also

FIG. 78 TWO-CYCLE GAS-ENGINE. CRANK AND CONNECTING-ROD ARE

ENCLOSED WITH THE PISTON

has less weight per horse-power. The cylinder of a two-
cycle engine is shown in Fig. 78.

A steam-engine is self-starting. The engineer has only
to turn the steam into the cylinder, but the gas-engine re-
quires to be turned until at least one explosion takes place,
for until there is an explosion of gas and air in the cylinder
there is no power.

A gas-engine may have a number of cylinders. Four-
cylinder and six-cylinder engines are common. In a four-
cylinder, four-cycle engine, while one cylinder is on the
power stroke the next is on the compression stroke, the
third on the admission stroke, and the fourth on the exhaust
stroke. Fig. 79 shows the Selden " explosion buggy" pro-

NINETEENTH-CENTURY INVENTIONS

pelled by a gas-engine. This machine was the forerunner
of the modern automobile.

The Steam Locomotive

Late in the eighteenth century a mischievous boy put
some water in a gun-barrel, rammed down a tight wad, and
placed the barrel in the fire of a blacksmith's forge. The
wad was thrown out with a loud report, and the boy's play-
mate, Oliver Evans, thought he had discovered a new

FIG. 79 SELDEN "EXPLOSION BUGGY." FORERUNNER OF THE MODERN

AUTOMOBILE

155

THE STORY OF GREAT INVENTIONS

power. The prank with the gun-barrel set young Evans
thinking about the power of steam. It was not long until
he read a description of a Newcomen engine. In the New-
comen engine, you will remember, it was the pressure of
air, not the pressure of steam, that lifted the weight. Evans
soon set about building an engine in which the pressure of
steam should do the work. He is sometimes called the
"Watt of America," for he did in America much the same
work that Watt did in Scotland. Evans built the first
successful non-condensing engine — that is, an engine in
which the steam, after driving the piston, escapes into the
air instead of into a condenser. The non-condensing en-
gine made the locomotive possible, for a locomotive could
not conveniently carry a condenser. Evans made a loco-
motive which travelled very slowly. He said, however:
"The time will come when people will travel in stages
moved by steam-engines from one city to another, almost
as fast as birds can fly, fifteen or twenty miles an hour."

The inventor who made the first successful locomotive
was George Stephenson, and it is worth noting that one of
his engines, the "Rocket," possessed all the elements of
the modern locomotive. He combined in the "Rocket"
the tubular boiler, the forced draft, and direct connec-
tion of the piston-rod to the crank-pin of the driving-
wheel.

The " Rocket" was used on the first steam railway (the
Stockton & Darlington, in England) , which was opened in
1825. There had been other railways for hauling coal by
means of horses over iron tracks, and other locomotives that
travelled over an ordinary road ; but this was the first road

NINETEENTH-CENTURY INVENTIONS

on which a steam-engine pulled a load over an iron track,
the first real railroad. Fig. 80 shows the " Rocket" and
two other early locomotives.

In order to build a railroad between Liverpool and Man-
chester for carrying both passengers and freight it was
necessary to secure an act of Parliament. Stephenson was
compelled to undergo a severe cross-examination by a com-
mittee of Parliament, who feared there would be great
danger if the speed of the trains were as high as twelve
miles an hour. He was asked:

"Have you seen a railroad that would stand a speed of
twelve miles an hour?"

"Yes."

"Where?"

"Any railroad that would bear going four miles an hour.
I mean to say that if it would bear the weight at four miles
an hour it would bear it at twelve."

* ' Do you mean to say that it would not require a stronger
railway to carry the same weight at twelve miles an hour?"

"I will give an answer to that. I dare say every person
has been over ice when skating, or seen persons go over,
and they know that it would bear them better at a greater
velocity than it would if they went slower; when they go
quickly the weight, in a measure, ceases."

"Would not that imply that the road must be perfect?"

"It would, and I mean to make it perfect."

For seven miles the road must be built over a peat bog
into which a stone would sink to unknown depths. To
convince the committee, however, and secure the act of
Parliament was more difficult than to build the road. But

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NINETEENTH-CENTURY INVENTIONS

Stephenson was one of the men who do things because they
never give up, and the road was built.

How a Locomotive Works

To understand how a locomotive works, let us consider
how the steam is -produced, how it acts on the piston, and
how it is controlled. The steam is produced in a locomotive
in exactly the same way that steam is produced in a tea-
kettle. Now everybody knows that a quart of water in a
tea-kettle with a wide bottom placed on a stove will boil
more quickly than the same amount of water in a tea-pot
with a narrow bottom. The greater the heating-surface—
that is, the greater the surface of heated metal in contact
with the water — the more quickly the water will boil and
the more quickly steam can be produced. In a locomotive
the aim is to use as large a heating-surface as possible. This
is done by making the fire-box double and allowing the water
to circulate in the space between the inner and. outer parts,
except underneath; also by placing tubes in the boiler
through which the heated gases and smoke from the fire
must pass. An ordinary locomotive contains two hundred
or more of these tubes. The water surrounds these tubes,
and is therefore in contact with a very large surface of
heated metal. In some engines the water is in the tubes,
and the heated gases surround the tubes.

The steam as it enters the cylinder should be dry — that
is, it should not contain drops of water. This is accom-
plished by allowing the steam from the boiler to pass into
a dome above the boiler. Here the steam, which is nearly

THE STORY OF GREAT INVENTIONS

dry, enters a steam-pipe leading to the cylinder (Fig. 81).
The steam is admitted to the cylinder by means of a slide-
valve. From the diagram it can easily be seen that the
valve admits steam first on one side of the piston, then on
the other. It can also be seen that the valve closes the
admission-port, and so cuts off the steam before the piston
has made a full stroke. The steam that is shut up in the
cylinder continues to expand and act on the piston. At the
same time the valve opens the exhaust-port, allowing the
steam to escape from the other side of the piston; but it
closes this port before the piston has quite finished the
stroke. The small quantity of steam thus shut up acts like
a cushion to prevent the piston striking the end of the
cylinder with too great force. The exhaust-steam escapes
through a blast-pipe into the chimney, drives the air before
it up the chimney, and thus makes a greater draft of air
through the fire-box. This is called the forced draft. The
escape of the exhaust-steam causes the puffing of the loco-
motive just after starting. After the engine is under way
the engineer partly shuts off the steam by means of the
reversing lever and the puffing is less noticeable.

The action of the steam may be summed up as follows:

1. Steam admitted to the cylinder (admission).

2. Valve closes admission -port (cut-off).

3 . Steam shut up in the cylinder expands, acting on the
piston (expansion period).

4. Valve opens exhaust - port to allow used steam to
escape (exhaust).

The devices for controlling the steam are the throttle-
valve and the valve-gear. The throttle-valve is at the en-

160

p O

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s- S

THE STORY OF GREAT INVENTIONS

trance to the steam-pipe in the steam-dome. This valve is
opened and closed by means of a rod in the engineer's
cab.

Stephenson's link-motion valve-gear is used on most loco-
motives. The forward rod in the diagram is in position to
act upon the valve-rod through the lever L. Suppose the
reversing-lever is drawn back to the dotted line ; then the for-
ward rod will be raised and the backward rod will come into
position to act on the lever L. If this is done while the loco-
motive is at rest the valve is moved through one-half a com-
plete stroke. In the diagram the steam enters the cylinder
on the right of the piston. After this movement of the valve
the steam would enter on the left side of the piston. In the
present position the locomotive would move forward, but
if the valve is changed so as to admit steam to the left of
the piston while the connecting-rod is in the position shown
then the engine will move backward. Thus the direction
can be controlled by the engineer in the cab. Of course,
this can be done while the engine is in motion. The for-
ward rod and the backward rod are each moved by an
eccentric on the axle of the front driving-wheel. The two
eccentrics are in opposite positions on the axle. An eccen-
tric acts just like a crank, causing the rod to move forward
and backward as the axle turns, and of course this motion
is given to the valve-rod through the lever. When the link
is set midway between the forward and the backward rod
the valve cannot move. When the link is raised or lowered
part way the valve makes a short stroke, and less steam is
admitted to the cylinder than with a full stroke. In start-
ing the locomotive the valve is set to make a full stroke.

162

NINETEENTH-CENTURY INVENTIONS

When the train is under headway the valve is set for a short
stroke to economize steam. The valve-gear and the throttle-
valve together take the place of the governor in the station-
ary engine, but while the governor acts automatically these
are controlled by the engineer.

In reality a locomotive is two engines, one on either side,
connected to the same driving-wheels. But the two piston-
rods are connected to the driving-wheels at points which
are at right angles with each other, so that when the crank
on one side is at the end of a stroke — the "dead centre" —
that on the other side is on the quarter, either above or
below the axle, ready for applying the greatest turning
force.

The expansion-engine was designed to use more of the
power of the steam than can be done in the single-cylinder
engine. In the double expansion-engine the steam expands
from one cylinder into another. The second cylinder must
be larger in diameter than the first. In the triple expansion-
engine the steam expands from the second cylinder into a
third, still larger. The second and third cylinders use a
large part of the power that would be wasted with only one
cylinder.

The Turbine

One of the great inventions relating to steam-power is
the steam-turbine. The water-turbine is equally useful in
relation to water-power. The water-turbine and the steam-
turbine work in very much the same way, the difference
being due to the fact that steam expands as it drives the
engine, while water drives it by its weight in falling, or by

THE STORY OF GREAT INVENTIONS

its motion as it rushes in a swift stream or jet against the
blades of the turbine.

The first steam-engine, that of Hero in the time of Archi-
medes, was a form of turbine (Fig. 82). It was driven by

the reaction of the steam as
it escaped into the air. The
common lawn-sprinkler, that
whirls as the water rushes
through it, is a water - turbine
that works in the same way.
"Barker's Mill" is the name
applied to a water-turbine that
works like the lawn-sprinkler.
As the water rushes out of the
opening it pushes against the
air. It cannot push against
the air without pushing back
at the same time. Never yet
has any person or object in
nature been able to push in
one direction only. It can-
not be done. If you push

a cart forward you push backward against the ground
at the same time. If there were nothing for you to push
back against your forward push would not move the cart
a hair's-breadth. If you doubt this, try to push a cart
when you are standing on ice so slippery that you cannot
get a foothold. It is the backward push of the water in the
lawn-sprinkler and the backward push of the steam in
Hero's engine that cause the machine to turn.

164

FIG. 82 HERO'S ENGINE

NINETEENTH-CENTURY INVENTIONS

The turbines in common use for both water and steam
power have curved blades. The reason for curving the
blades can best be seen by referring to an early form of
water-wheel. The best water-turbine is only an improved
form of water-wheel. The first water-wheels had flat
blades, and these answered very well so long as only a low
power was needed and it was not necessary to save the
power of the water. It was found, however, that there
was a great waste of power in the wheel with flat blades.
One inventor proposed to improve the wheel by curving the

PIG. 83 AN UNDERSHOT WATER-WHEEL WITH CURVED BLADES

blades in such a way that the water would glide up the
curve and then drop directly downward (Fig. 83). The
water then gives up practically all of its power to the wheel
and falls from the wheel. It would have no power to

165

THE STORY OF GREAT INVENTIONS

move a second wheel. In this way he used practically
all the power of the water. To save the power of the water
by making all of the water strike the wheel at high speed

FIG. 84 AN OVERSHOT WATER-WHEEL

the channel was made narrow just above the wheel, form-
ing a mill-race. This applies to the undershot wheel. In
the overshot wheel (Fig. 84) the power depends on the
weight of the water and on its height. The water runs into
buckets attached to the wheel, and, as it falls in these
buckets, turns the wheel. The undershot wheel and the

166

NINETEENTH-CENTURY INVENTIONS

some

mill-race represent a common form of turbine, that form in
which the steam or the water is forced in a jet against a
set of curved blades. Fig. 85 shows a steam-turbine run
by a jet of steam. In the water-turbine there are two sets
of blades. One set rotates, the other remains fixed. The
use of the fixed blades is to turn the water and drive it in
the right direction against the moving blades. In
forms of turbine there are
more than two sets of
blades. The steam, as it
passes through, gives up
some of its power to each
set of blades until, after
passing the last set, it has
given up nearly all its pow-
er. The action of the steam
in this turbine is somewhat
like that in the expansion-
engine, in which the steam
gives up a portion of its
power in each cylinder.
Fig. 86 is from a photo-
graph of a modern steam-
turbine, and Fig. 87 is a
drawing of the same tur-
bine showing the course of the steam,
that runs a large dynamo.

In 1897, as the battle-ships of the British fleet were as-
sembled to celebrate the Diamond Jubilee of Queen Victoria,
a little vessel a hundred feet long darted in and out among

167

FIG. 85 DE LAVAL STEAM-TURBINE

Driven by a jet of steam striking
the blades. .

Fig. 88 is a turbine

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THE STORY OF GREAT INVENTIONS

the giant ships, defied the patrol-boats whose duty it was
to keep out intruders, and raced down the lines of battle-
ships at the then unheard-of speed of thirty-five knots an
hour. It was the Turbinia, fitted with the Parsons turbine.
This event marked the beginning of the modern turbine.

FIG. 88 A STEAM-TURBINE THAT RUNS A DYNAMO GENERATING I4,OOO

ELECTRICAL HORSE-POWER

The steam enters through the large pipe at the left.

It also marked the beginning of a revolution in steam
propulsion.

The Parsons turbine does not use the jet method, but
the steam enters near the centre of the wheel and flows

170

NINETEENTH-CENTURY INVENTIONS

toward the rim, passing over a number of rows of curved
blades. The Parsons turbine is used on the fastest ocean
liners. The Lusitania, one of the fastest steamships in the
first decade of the twentieth century, has two sets of high
and low pressure turbines with a total of 68,000 horse-power.

The windmill is a form of turbine driven by the air. As
the air rushes against the blades of the windmill, it forces
them to turn. If the windmill were turned by some me-
chanical power, it would drive the air back, and we should
have a blower. This is what we have in the electric fan,
a small windmill driven by an electric motor so that it
drives the air instead of being driven by it. The blades of
the windmill and the electric fan are shaped very much
like the screw propeller. The screw propeller, driven by
an engine, would drive the water back if the ship were
firmly anchored, just as the fan drives the air. But it can-
not drive the water back without pushing forward on the
ship at the same time, and this forward push propels the
ship. It is difficult to attain what is now regarded as high
speed with a single screw. With engines in pairs and two
lines of shafting higher power can be used. The best
steamers, therefore, are fitted with the twin-screw pro-
peller. Some large steamers have three and some four
screws.

The screw propellers of turbine steamships are made of
small diameter, that they may rotate at high speed without
undue waste of power. By the use of turbine engines and
twin-screw propellers, the weight of the machinery has been
greatly reduced. The old paddle-wheels, with low-pressure
engines, developed only about two horse-power for each

171

THE STORY OF GREAT INVENTIONS

ton of machinery. The turbine, with the twin-screw pro-
peller, develops from six to seven horse-power for every
ton of machinery. The modern steamer, with all its ma-
chinery and coal for an Atlantic voyage, weighs no more
than the engines of the old paddle-wheel type and coal
would weigh for the same horse-power. The steam-turbine
and the twin-screw propeller have made rapid ocean travel
possible.

Chapter VI

THE TWENTIETH-CENTURY OUTLOOK

WE have seen that the latter half of the nineteenth cen-
tury was a time of invention. It was a time when the
great discoveries of many centuries bore fruit in great in-
ventions. It was thought by some scientists that all the
great discoveries had been made, and that all that remained
was careful work in applying the great principles that had
been discovered. So far was this from being true that in
the last ten years of the nineteenth century discoveries were
made more startling, if possible, than any that had pre-
ceded. The nineteenth century not only brought forth
many great inventions, but handed down to the twentieth
century a series of discoveries that point the way to still
greater inventions.

Air-Ships

For centuries men sailed over the water at the mercy of
the wind. The sailing vessel is helpless in a storm. Early
in the nineteenth century they learned to use the power of
steam for ocean travel, and the wind lost its terrors. Late
in the eighteenth century men learned to sail through the
air in balloons even more at the mercy of the wind than the

THE STORY OF GREAT INVENTIONS

sailing vessels on the ocean. More than a hundred years
later they learned to propel air-ships in the teeth of the
wind. The nineteenth century saw the mastery of the
water. The twentieth is witnessing the mastery of the air.

The first balloon ascension was made in 1783, two men
being carried over Paris by what Benjamin Franklin called
a "bag of smoke." The balloon was a bag of oiled silk
open at the bottom. In the middle of the opening was a
grate in which bundles of fagots and sheaves of straw were
burned. The heated air filled the balloon, and as the heated
air was lighter than the air around it the balloon could rise
and carry a load. Beneath the grate was a wicker car for
the men. They were supplied with straw and fagots with
which to feed the fire. When they wanted to rise higher
thev added fuel to heat the air in the balloon. When they
wished to descend they allowed the fire to die out, so that
the air in the balloon would cool. They could not guide
the balloon, but drifted with the wind. That great philoso-
pher Benjamin Franklin, who saw the ascension, said that
the time might come when the balloon could be made to
move in a calm and guided in a wind. In the second
ascension bags of sand were taken as ballast, and the car
was suspended from a net which enclosed the balloon. In
this second ascension hydrogen gas was used in place of
heated air.

The greatest height ever reached by a human being is
about seven miles. This height was first reached in 1862 by
two balloonists who nearly lost their lives in the adventure.
At a height of nearly six miles one of the men became un-
conscious. The other tried to pull the valve-cord to allow

174

THE TWENTIETH-CENTURY OUTLOOK

the gas to escape, but found that the cord was out of his
reach. His hands were frozen, but he climbed out of the
car into the netting of the balloon, secured the cord in his
teeth, returned to the car, and threw the weight of his body
on the cord. This opened the valve and the balloon de-
scended.

Those who go to great heights now provide themselves
with tanks of compressed oxygen. Then when the air
becomes so thin and rare that breathing is difficult they
can breathe from the oxygen tanks.

A captive balloon in war serves as an observation tower
from which to observe the enemy. It is connected to the
ground by a cable. This cable is wound on a drum carried
by the balloon wagon. The balloon can be lowered or
raised by winding or unwinding the cable.

The gas-bag is sometimes made of oiled silk, sometimes
of two layers of cotton cloth with vulcanized rubber be-
tween. The cotton cloth gives the strength needed, and
the rubber makes the bag gas-tight.

The most convenient gas for rilling balloons is heated air,
but the air cools rapidly and loses its lifting power. Coal-
gas furnished by city gas-plants is sometimes used. This
gas will lift about thirty-five pounds for every thousand
cubic feet. A balloon holding thirty-five thousand cubic
feet of coal gas will easily lift the car and three persons.
The lightest gas is hydrogen. This gas will lift about
seventy pounds for every thousand cubic feet. Hydrogen
is made by the action of sulphuric acid and water on iron.
If a bit of iron is thrown into a mixture of sulphuric acid
and water bubbles of hydrogen gas will rise through the
12

THE TWENTIETH-CENTURY OUTLOOK

liquid. This gas will burn if a lighted match is brought
near.

A balloon without propelling or steering apparatus is not
an air- ship. It may be raised by throwing out ballast or
lowered by letting out gas, but further than this the aero-
naut has no control over its movements. The balloon
moves with the wind. No breeze is felt, for balloon and
air move together. To the aeronaut the balloon seems to
be in a dead calm. It is only when he catches sight of
houses and trees and rivers darting past below that he
realizes that the balloon is moving.

If a balloon has a propelling apparatus it may move
against the wind, or it may outspeed the wind. A balloon
with propelling and steering apparatus is called a "dirigible"
balloon, which means a balloon that can be guided. Figs.
89 and 90 are from photographs of a "dirigible" used in the
British army. Such a balloon is usually long and pointed
like a spindle or a cigar. It is built to cut the air, just as a
rowboat built for speed is long and pointed so that it may
cut the water. The propeller acts like an electric fan. An
electric fan drives the air before it, but the air pushes back
on the fan just as much as the fan pushes forward on the
air, and if the fan were suspended by a long cord it would
move backward. So the large fan or screw propeller on an
air-ship drives the air backward, and the air reacts and
drives the ship forward. In the same way the screw-
propeller of an ocean liner drives the vessel forward by the
reaction of the water.

A balloon rises for the same reason that wood floats on
water. The wood is lighter than water, and the water

177

THE TWENTIETH-CENTURY OUTLOOK

holds it up. The balloon is lighter than air and the air
pushes it up. The upward push of the air is just equal to
the weight of the air , that would fill the same space the
balloon fills. The balloon can support a load that makes
the whole weight of the balloon and its load together equal
to the weight of the air that would fill the same space. For
the balloon to rise the load must be somewhat lighter than
this. A balloon may be made lighter than air by filling
it with heated air or coal-gas. Hydrogen, however, is used
in the better balloons and in air-ships of the "lighter than
air" type.

The air- ship must, of course, use a very light motor. A
steam-engine cannot .be made light enough. Neither can
an electric motor, if we add the weight of the storage battery
that would be required. Air-ships have been propelled by
both steam-engines and electric motors, but with low speed
because of the weight of the engine or motor. The only
successful motor for this purpose is the gasolene motor,
which is a form of gas-engine using gas formed by the
evaporation of gasolene.

The first air-ship that could be controlled and brought
back to the starting-point was made in France, in 1885, by
Captain Renard, of the French army. It was a cigar-
shaped balloon, with a screw propeller run by an electric
motor of eight horse-power. The ship attained a speed of
thirteen miles an hour.

A more successful air-ship was that built by Santos
Dumont. With this ship, in 1901, he won a prize of $20,000,
which had been offered to the builder of the first air-ship that
would sail round the Eiffel Tower in Paris from the Aero-

179

THE STORY OF GREAT INVENTIONS

static Park of Vaugirard, a distance of about three miles,
and return in half an hour.

The balloon part of this air-ship was 112^ feet long and
19 J feet in diameter, holding about 6400 cubic feet of gas.
The car was built of pine beams no larger in section than
two fingers and weighing only no pounds. This car could
be taken apart and put in a trunk. A gasolene automobile
motor was used, and thus it is seen that the automobile
aided in solving the problem of sailing through the air. It
was the automobile that led to the construction of light and
powerful gasolene motors. The car and motor were sus-
pended from the balloon by means of piano wires, which
at a short distance were invisible, so that the man in the
car appeared in some mysterious way to follow the balloon.
The ship was turned to the left or right by means of a
rudder. It was made to ascend or descend by shifting the
weight of a heavy rope that hung from the car, thus in-
clining the ship upward or downward.

Count Zeppelin, of Germany, constructed a much larger
dirigible balloon than that of Santos Dumont. The balloon
of the first Zeppelin air- ship w^as 390 feet in length, with a
diameter of about 39 feet. It was divided into seventeen
sections, each section being a balloon in itself. These sec-
tions serve the same purpose as the water-tight compart-
ments of a battle-ship. An accident to one section would
not mean the destruction of the entire ship. Within the
balloon is a framework of aluminum rods extending from
one end to the other and held in place by aluminum rings
twenty-four feet apart. The balloon contains about 108,000
cubic feet of gas, and it costs about $2500 to fill it. One

1 80

FIG. 91 A ZEPPELIN AIR-SHIP

THE STORY OF GREAT INVENTION S

filling of gas will last about three weeks. There are two
cars, each about ten feet long, five feet wide, and three feet
deep. The cars are connected by a narrow passageway
made of aluminum wires and plates, making a walking
distance of 326 feet — longer than the decks of many ocean
steamers. A sliding weight of 300 kilograms (about 600
pounds) serves the same purpose as the guide-ropes in the
Santos Dumont air- ship. By moving this weight forward
or backward the ship is raised or lowered at the bow or
stern, and thus caused to glide up or down. Anchor-ropes
are carried for use in landing. The ship is propelled by

4 t

FIG. 92 COUNT ZEPPELINS DEUTSCHLAND, THE FIRST AIR-SHIP IN

REGULAR PASSENGER SERVICE

182

THE TWENTIETH-CENTURY OUTLOOK

four screws, and guided by a number of rudders laced
some in front and some in the rear. The first Zeppelin
air- ship carried four passengers. The work of Dumont and

Zeppelin has led the great powers to manufacture dirigible
balloons for use in time of war. Fig. 91 shows one of the
Zeppelin air-ships sailing over a lake.

A larger air-ship, the Deutschland, built later by Count
Zeppelin, was the first air-ship to be used for regular pas-
senger service. The Deutschland is shown in Fig. 92. The
Deutschland carried the crew and twenty passengers. It

183

THE STORY OF GREAT INVENTIONS

operated for a time as a regular passenger air-ship between
Friedrichshafen and Dusseldorf , a distance of three hundred
miles. The Deutschland was wrecked in a storm on June 28,
1910, but it was successfully operated long enough to give
Germany the honor of establishing the first air-ship line for
regular passenger service. This is an honor perhaps equal-
ly as great as that of establishing the first commercial elec-
tric railway, which also belongs to Germany. An American
army air-ship is shown in Fig. 93.

The Aeroplane

The aeroplane is a later development than the dirigible
balloon. The aeroplane is heavier than air. So is a bird
and so is a kite. What supports a kite or a bird as it soars ?
Every boy knows that the strings of a kite must be attached
so that the kite is inclined and catches the wind under-
neath. Then the wind lifts the kite. In still air the kite
will not fly unless the boy who holds the string runs very
fast and so causes an artificial breeze to blow against the
kite. In much the same way a hovering bird is held aloft
by the wind. In a dead calm the bird must flap its wings
to keep afloat. If the kite string is cut the kite tips over
and drops to the earth because it has lost its balance. The
lifting power of the wind is well shown in the man-lifting
kites which are used in the British army service. In a high
wind a large kite is used in place of a captive balloon. It
is a box -kite made of bamboo and carries a passenger in a
car, the car running on the cable which attaches the kite
to the ground. Now suppose a kite with a motor and pro-

184

FIG. 94 — IN FULL FLIGHT

THE STORY OF GREAT INVENTIONS

peller in place of a string and a boy to run with it, and that
the kite is able to balance itself, then it will sail against a
wind of its own making and you have a flying-machine
heavier than air.

The first aeroplane that would fly under perfect control
of the operator was built by the Wright brothers at Dayton,
Ohio. When they were boys, Bishop Wright gave his two
sons, Orville and Wilbur, a toy flyer. From that time on
the thought of flying through the air was in their minds.
A few years later the death of Lilienthal, who was killed by
a fall with his glider in Germany, stirred them, and they
took up the problem in earnest. They read all the writings
of Lilienthal and became acquainted with Mr. Octave
Chanute, an engineer of Chicago who had made a success-
ful glider. They soon built a glider of their own, and ex-
perimented with it each summer on the huge sand-dunes of
the North Carolina coast.

A glider is an aeroplane without a propeller. With it
one can cast off into the air from a great height and sail
slowly to the ground. Before attempting to use a motor
and propeller, the Wrights learned to control the glider
perfectly. They had to learn how to prevent its being
tipped over by the wind, and how to steer it in any direc-
tion. This took years of patient work. But the problem
was conquered at last, and they attached a motor and pro-
peller to the glider, and had an air-ship under perfect con-
trol and with the speed of an express- train. Their flyer
of 1905, which made a flight of twenty-four miles at a speed
of more than thirty-eight miles an hour, carried a twenty-
five-horse-power gasolene motor, and weighed, with its load,

186

5' 2

?> 5

THE STORY OF GREAT INVENTIONS

925 pounds. Figs. 94 and 95 show the Wright air-ship in
flight. Fig. 97 shows the mechanism.

How the Wright Aeroplane Is Kept Afloat

The Wright aeroplane is balanced by a warping or twist-
ing of the planes i and 2, which form the supporting sur-
faces (Fig. 96) . If left to itself the machine would tip over
like a kite when the string is cut and drop edgewise to
the ground. Suppose the side R starts to fall. The cor-
ners a and e are raised by the operator while b and / are
lowered, thus twisting the planes, as shown in the dotted
lines of the figure. The side R then catches more wind than
the side L. The wind exerts a greater lifting force on R than
on L, and the balance is restored. The twist is then taken
out of the machine by the operator. A ship when sailing
on an even keel presents true un warped planes to the wind.

The twisting is brought about by a pull on the rope 3,
which is attached at d and c, and passes through pulleys at
g and h. When the rope is pulled toward the left the right
end is tightened and slack is paid out at the left end. This
pulls down the corner d, and raises e. The corner a is
raised by the post which connects a and e. The rope 4,
passing from a to b through pulleys at m and n, is thus
drawn toward a and pulls down the corner b. Thus a is
raised and b is lowered. At the same time rope 4 turns
the rear rudder to the left, as shown by the dotted lines,
thus forcing the side R against the wind. Of course, if
the left side of the machine starts to fall, the rope 3 is
pulled toward the right, and all the movements take place

188

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THE STORY OF GREAT INVENTIONS

in the opposite direction. The ropes are connected to a
lever, by which the operator controls the warping of the
planes. These movements are possible because the joints
are all universal, permitting movement in any direction.
In whatever position the planes may be set, they are held
perfectly rigid by the two ropes, together with others not
shown in the figure. The machine is guided up or down
by the front horizontal rudder.

When the aeroplane swings round a curve the outer wing
is raised because it moves faster than the inner wing, and
therefore has greater lifting force. Thus the aeroplane banks
its own curves.

The Wright flying-machine is called a biplane because it
has two principal planes, one above the other. A number of
successful flying-machines have been built with only one
plane, and these are called monoplanes. A monoplane that
early became famous is that of Bleriot (Fig. 98). The
Bleriot monoplane was the first flying-machine to cross the
English Channel. This machine is controlled by a single
lever mounted with a ball-and-socket coupling, so that it
can move in any direction. When on the ground it is sup-
ported by three wheels like bicycle wheels, so that it does
not require a track for starting, but can start anywhere from
level ground. The Wright and the Bleriot represent the
two leading types of early successful flying-machines.

Submarines

Successful navigation beneath the surface of the water,
though not carried to the extent imagined by Jules Verne,

190

I S

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THE STORY OF GREAT INVENTIONS

was a reality at the beginning of the twentieth century.
Instead of twenty thousand leagues under the sea, less
than a hundred leagues had been accomplished, but no one
can foretell what the future may have in store.

The principal use of the submarine is in war. It is a
diving torpedo - boat, and acts under cover of water as

FIG. 98 — THE BL£RIOT MONOPLANE

the light artillery on land is secured behind intrenchments.
The weapon used by the submarine is the torpedo. The
torpedo is itself a small submarine able to propel itself, and
if started in the water toward a certain object, to go under
water straight to the mark. It carries a heavy charge either

192

THE TWENTIETH-CENTURY OUTLOOK

of guncotton or dynamite, which explodes when the tor-
pedo strikes a solid object, such as a battle-ship. The first
torpedo was intended to be steered from the shore by means
of long tiller-ropes, and to be propelled by a steam-engine
or by clockwork. The Whitehead fish torpedo, invented
in 1866, is self-steering. At the head of the torpedo is a
pointed steel firing-pin. When the torpedo strikes a ship
or any rigid object this steel pin is driven against a det-
onator cap which is in the centre of the charge of dyna-
mite. The blow causes the cap to explode, and the ex-
plosion of the cap explodes the dynamite. The torpedo is
so arranged that it cannot explode until it is about thirty
yards away from the ship from which it is fired. The steel
pin cannot strike the cap until a small " collar" has been
revolved off by a propeller fan, and this requires a distance
of about thirty yards. The screw propeller is driven by
compressed air. A valve which is worked by the pressure
of the water keeps the torpedo at any depth for wjaich the
valve is set. The torpedo contains many ingenious devices
for bringing it quickly to the required depth and keeping
it straight in its course. One of these devices is the gyro-
scope, which will be described under the head of ''spinning
tops." Whitehead torpedoes are capable of running at a
speed of over thirty-seven miles an hour for a range of two
thousand yards and hitting the mark aimed at almost as
accurately as a gun. The submarine boat carries a number
of torpedoes, and has one torpedo-tube near the forward
end from which to fire the torpedoes.

It would be very difficult for one submarine to fight an-
other submarine, for the submarine when completely sub-

i93

THE STORY OF GREAT INVENTIONS

merged is blind. It could not see in the water to find its
enemy. The torpedo-boat-destroyer is able to destroy a
submarine by means of torpedoes, shells full of high ex-
plosives, or quick-firing guns. Advantage must be taken
of the moment when the submarine comes to the surface
to get a view of her enemy.

One of the great enemies of the submarine will probably
be the air- ship, for while the submarine when under water
cannot be seen from a ship on the surface, it can, under
favorable conditions, be seen from a certain height in the
air.

Most submarines use a gasolene motor for surface travel,
and an electric motor run by a storage battery for naviga-
tion below the surface. The best submarines can travel at
the surface like an ordinary boat, or " awash " —that is, just
below the surface — with only the conning tower projecting
above the water, or they can travel completely submerged.

The rising and sinking of the submarine depend on the
principle of Archimedes. The upward push of the water is
just equal to the weight of the water displaced. If the
water displaced weighs more than the boat, then the up-
ward push of the water is greater than the weight of the
boat and the boat rises. However, the boat can be made
to dive when its weight is just a little less than the weight
of the water displaced. This is done by means of horizon-
tal rudders which may be inclined so as to cause the boat
to glide downward as its propeller drives it forward.

The magnetic compass is not reliable in a submarine with
a hull made of steel. The electric motor used for propel-
ling the boat under water also interferes with the action of

194

THE TWENTIETH-CENTURY OUTLOOK

the compass, because of its magnetic field. The gyroscope,
which we shall describe later, is not affected by magnetic
action, and may take the place of the compass.

Water ballast is used, and when the submarine wishes to
dive, water is admitted into the tanks until the boat is
nearly heavy enough to sink of its own weight. It is then
guided downward by the horizontal rudder. The sub-
marine is driven by a screw propeller, and some submarines
are lowered by means of a vertical screw. Just as a hori-
zontal screw propels a vessel forward, so a vertical screw
will propel it downward. When the submarine wishes to
rise, it may do so by the action of its rudder, or the water
may be pumped out of its tanks, when the water will raise

FIG. 99 — THE "PLUNGER"

Photo by Pictorial News Co.
195

THE STORY OF GREAT INVENTIONS

it rapidly. A submarine which is kept always a little
lighter than water will rise to the surface in case of accident
to its machinery. Figs. 99, 100, and 101 are from photo-
graphs of United States submarines.

There is one kind of submarine built for peaceful pur-
suits which deserves mention. It is the Argonaut, invented
by Simon Lake. This remarkable boat crawls along the
bottom of the sea, but not at a very great depth. It is
equipped with divers' appliances, and is used in saving
wreckage. Divers can go out through the bottom of the
boat, walk about on the sea bottom, and when through with
their work re-enter the boat; all the while boat and men
are, perhaps, a hundred feet below the surface. The divers'
compartment, from which the divers go out into the water,
is separated by an air-tight partition from the rest of the
boat. Compressed air is forced into this compartment until
the pressure of the air equals the pressure of the water out-
side. Then the door in the bottom is opened, and the air
keeps the water out. The men in their diving-suits can
then go out and in as they please.

For every boat there is a depth beyond which it must
not go. The penalty for going beyond this depth is a
batter ed-in vessel, for the pressure increases with the depth.
Every time the depth is increased thirty-two feet the press-
ure is increased fifteen pounds on every square inch. Be-
yond a certain depth the vessel cannot resist the pressure.
Submarines have been made strong enough to withstand
the pressure at a depth of five thousand feet, or nearly a
mile. Most submarines, however, cannot go deeper than
a hundred and fifty feet.

196

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THE STORY OF GREAT INVENTIONS

Air is supplied to the occupants of the boat either from
reservoirs containing compressed air or oxygen, or by means
of chemicals which absorb the carbon dioxide produced in
breathing and restore the needed quantity of oxygen to the
air.

While the men in >the boat cannot see in the water, they
can see objects on the surface of the water, even when their

FIG. 101 FIRST SUBMARINE CONSTRUCTED IN UNITED STATES. IT WENT

TO THE BOTTOM WITH SEVEN MEN, WHO WERE DROWNED

Photo by Pictorial News Co.

boat is several feet below the surface, by means of the peri-
scope. This is an arrangement of lenses and mirrors in a
tube bent in two right angles, which projects a short dis-
tance above the surface and can be turned in any direction

198

THE TWENTIETH-CENTURY OUTLOOK

(Fig. 102). Thus the boat,
while itself nearly invisible,
can have a clear view of the
battle-ship which it is about
to attack.

Some Spinning Tops that
Are Useful

Every one knows that a
top will stand upright only
when it is spinning. Most
tops when spinning will
stand very rough treatment
without being upset. The
whip -top will stand a se-
vere lashing. Spin a top
upright and give it a knock.
It will go round in a circle
in a slanting position, and
after a time will right itself.
If the top is struck toward
the south it will not bow-
to ward the south, but tow-
ard the east or west. In
throwing a quoit, the quoit

must be given a spinning motion or the thrower cannot be cer-
tain how it will alight. A coin thrown up with a spinning mo-
tion will not turn over. The quoit and the coin are like the
top. They will not turn over easily when spinning. For
the same reason a rifle bullet is set spinning by the spiral

199

FIG. 102 HOW MEN IN A SUBMARINE

SEE WHEN UNDER THE WATER

THE STORY OF GREAT INVENTIONS

grooves in the bore of the gun, and it goes straight to its
mark. With a smooth-bore gun that does not set the bullet
spinning the gunner cannot be sure of his aim.

It took a long time to discover that the spinning top is
a useful machine. It is useful because of its steady motion,
because it is difficult to turn over. It was discovered by
Newton long ago that every moving object tries to keep
on in the direction in which it is moving. A moving object
always requires some force to change its direction. The
spinning top is a beautiful illustration of this principle.
The top that is most useful is the gyroscope top (Fig. 103).
It is mounted on pivots so arranged that the top can turn in
any direction within the frame that supports it. If the
top is set spinning one may turn the frame in any direction,

FIG. 103 A TOP THAT SPINS ON A STRING

but the top does not change direction. The axis of the top
will point in the same direction all the while the top is
spinning, no matter how the supporting frame is moved
about. The top will spin on a string. If attached inside

200

THE TWENTIETH-CENTURY OUTLOOK

a box the box can be made to stand on one corner while the
top is spinning.

This top, which is so hard to upset, has been used in ships
to prevent the ship being rolled by the waves. A large fly-
wheel is mounted in the middle of the vessel on a hori-
zontal axle. A fly-wheel is only a large top. It spins with
a steady motion, and because of its larger size it is very
much harder to overturn than a toy top. The fly-wheel in
the ship resists the rolling force of the waves and steadies
the ship, so that even with high waves the rolling can
scarcely be felt. The waves do not so readily break over
the ship when thus steadied by the revolving wheel.

The gyroscope is also used in some forms of torpedo to
give the torpedo steady motion. By means of a spring re-
leased by a trigger the gyroscope within the torpedo is set
spinning before the torpedo enters the water. The gyro-
scope keeps its direction unchanged, and as the torpedo
turns one way or the other the gyroscope acts upon one or
the other of two valves connected with the compressed-air
chambers from which the screws of the torpedo are driven.
The air thus set free by the gyroscope drives a piston-rod
connected with a rudder in such a way as to right the tor-
pedo. The torpedo goes through the water with a slightly
zigzag motion, but never more than two feet out of the line
in which it was aimed.

The Monorail-Car

Another use of the gyroscope is in the monorail-car. To
make a car run on a single rail, with its weight above the

201

THE STORY OF GREAT INVENTIONS

rail, was impossible until the use of the gyroscope was dis-
covered. In the monorail-car invented by Brennan (Fig.
104) there are two gyroscopes, each weighing fifteen hun-
dred pounds, driven at a speed of three thousand revolu-
tions a minute by an electric motor. Each gyroscope wheel

FIG. 104 A CAR THAT RUNS ON ONE RAIL

Louis Brennan's full-size monorail.

with its motor is mounted in an air-tight casing from which
the air is pumped out. The wheel will run much more easily
in a vacuum than in air, for the air offers very great resist-
ance to its motion. The wheels are placed one on each side
of the car with their axles horizontal. When the car starts
to fall the spinning gyroscopes right it much as a spinning
top rights itself if tipped to one side by a blow. If the wind
tips the car to the left the gyroscopes incline to the right

202

THE TWENTIETH-CENTURY OUTLOOK

until the car is again upright. If the load is heavier on the
right side the car inclines itself toward the left just as a
man leans to the left when carrying a load on his right
shoulder. In rounding a curve the car leans to the inside
of the curve just as a bicycle rider does, and as a railway
train is made to do by laying the outer rail of the curve
higher than the inner rail. Two gyroscopes spinning in
opposite directions are necessary to keep the car from fall-
ing when rounding a curve.

The gyroscope may be used in place of a compass. If it
is set spinning in a north and south direction it will con-
tinue to spin in a north and south direction, no matter how
the ship may turn. It is even more reliable than the com-
pass, for it is not affected by magnetic action. Possibly
some of the great inventions yet to be made will be new
uses of the spinning top.

Liquid Air and the Greatest Cold

For a long time after men had learned the use of the fur-
nace and could produce great heat, the greatest cold known
was that of the mountain-top. Men wondered what would
happen if air could be made colder than the frost of winter,
but knew not how to bring about such a result. They won-
dered what things could be frozen that remain liquid or
gaseous even in the cold of winter.

The first artificial cold was produced by a mixture of
salt and ice, such as we now use in an ice-cream freezer.
In time men learned other ways of producing great cold
and even to manufacture ice in large quantities.

203

THE STORY OF GREAT INVENTIONS

The cold of liquid air is far greater than that of ice or
even a freezing mixture of salt and ice. Liquid air is simply
air that is so cold that it becomes a liquid just as steam
when cooled forms water. Steam has only to be cooled to
the temperature of boiling water, while air must be cooled
to 314 degrees below zero on the Fahrenheit scale.

If it were possible for us to live in such a climate, and
tfye world were cooled to the temperature of liquid air, we
should have a curious world, \yatch - springs might be
made out of pewter, bells of tin, and piano wires of solder,
for these metals are made stronger by the extreme cold of
liquid air. There would be no air to breathe. Oceans and
rivers would be frozen solid, and the air would form a liquid
ocean about thirty-five feet deep. This ocean of liquid air
would be kept boiling a long time by the heat of the ice
beneath it, for ice is hot compared with liquid air. The ice
would cool as it gave up its heat to the liquid air and in
time become as cold as the liquid air itself.

Liquid air has been shipped thousands of miles in a double
walled tin can, the space between the two walls being filled
with felt. The felt protects the liquid air from the Jieat of
the air without. The liquid air evaporates slowly, and es-
capes through a small opening at the top.

Professor Dewar, a successor of Faraday in the Royal
Institution, invented the Dewar bulb, by means of which
the evaporation of the liquid air is prevented. This bulb
is a double- walled flask. In the space between the two
walls of the flask is a vacuum. Now a vacuum is the best
possible protection against heat. If we were to take a
bottle full of air and pump out from the bottle all except

204

THE TWENTIETH-CENTURY OUTLOOK

about a thousandth of a millionth of the air it contained at
first we should have such a vacuum as that of the Dewar
bulb. With such a vacuum around it ice could be kept
from melting for many days even in the hottest weather,
for no heat can go through a vacuum.

But the greatest cold is not the cold of liquid air. Liquid
hydrogen is so cold that it freezes air. When a flask of
liquid hydrogen is opened there is a small snow-storm of
frozen air in the mouth of the flask. But even this is not
the greatest cold. The liquid hydrogen may be frozen,
forming a hydrogen snow whose temperature is 43 5 degrees
below zero. This is nearly equal to the cold of the space
beyond the earth's atmosphere, which is the greatest pos-
sible cold.

The Electric Furnace and the Greatest Heat

The greatest heat that has yet been produced artificially
is that of the electric arc. The exact temperature of the
electric arc is not known with certainty. It is known, how-
ever, that the temperature of the hottest part of the arc
is not less than 6500 degrees Fahrenheit. When we com-
pare this with the temperature of the hottest coal furnace,
which is about 4000 degrees, we can very easily understand
that something is likely to happen at the temperature of
the electric arc that could not happen in an ordinary
furnace.

If an electric arc is enclosed by something that will hold
the heat in we have an electric furnace, and any substance
placed in the furnace may be made nearly as hot as the

205

THE STORY OF GREAT INVENTIONS

arc itself. In the electric furnace any substance, whether
found in nature or prepared artificially, may be melted or
vaporized.

It was Henri Moissan, Professor of Chemistry at the Sor-
bonne in Paris, who made the first great discoveries in the
use of the electric furnace and produced the first artifi-
cial diamonds. The study of diamonds led Moissan to be-
lieve that in nature they are formed by the cooling of a
melted mixture of iron and carbon. He could prepare such
a mixture with his electric furnace, he thought, and so
make diamonds like those of the diamond mines. So, with
an electric furnace having electrodes as large as a man's
wrist, a mixture of iron and charcoal in a carbon crucible,
and a glass tank filled with water, Moissan set out to change
the charcoal to diamonds. At a temperature of more than
six thousand degrees the iron and charcoal were melted to-
gether. For a time of from three to six minutes the mixture
was in the intense heat. Then the covering of the furnace
was removed and the crucible with the melted mixture
dropped into the tank of water. With some fear this was
done for the first time, for it was not known what would
happen when such a hot object was dropped into cold
water. But no explosion occurred, only a violent boiling
of the water, a fierce blazing of the molten mass, and then
a gradual change of color from white to red and red to
black. With boiling acids and other chemicals the refuse
was removed, and the fragments that remained were found
to be diamonds, small, it is true, so small that they could
be seen only with the aid of a microscope, but giving prom-
ise of greater things to come. Trie outer crust of iron held

206

FIG. 105 MANUFACTURING DIAMONDS FIRST OPERATION

Preparing the furnace. Charcoal and iron ore placed in a crucible and
subjected to enormous heat electrically.

THE STORY OF GREAT INVENTIONS

the melted charcoal under enormous pressure while it
slowly cooled and formed the diamond crystals. The proc-
ess of manufacturing diamonds is illustrated in Figs. 105,
106, and 107.

The electric furnace has made possible the preparation
of substances unknown before, and the production in large
quantities at low cost of substances that before were too
costly for general use. One of the best known of these
substances is aluminum. With the discovery of the electric-
furnace method of extracting aluminum from its ores, the
price of aluminum fell from one hundred and twenty-four
dollars per pound to twelve cents per pound.

Among the many uses of the electric furnace we may
mention the preparation of calcium carbide, which is used
in producing the acetylene light; carborundum, a sub-
stance almost as hard as diamond; and phosphorus, which
is used in making the phosphorus match. It is used also
to some extent in the manufacture of glass, and, in some
cases, for extracting iron from its ores.

The Wireless Telegraph

A ship in a fog is struck by another ship. The water
rushes in, puts out the fires in the boilers, the engines stop,
the ship is helpless in mid-ocean in the darkness of the night.
But the snapping of an electric spark is heard in one of the
cabins. Soon another vessel steams alongside. The life-
boats are lowered and every person is saved. The call for
help had gone out over the sea in every direction for two
hundred miles. Another ship had caught the signal and

208

FIG. I06— MANUFACTURING DIAMONDS SECOND OPERATION

The furnace at work.

THE STORY OF GREAT INVENTIONS

hastened to the rescue, and the world realized that the
wireless telegraph had robbed the sea of its terrors.

Without the curious combination of magnets, wires, and
batteries on the first ship no signal could have been sent,
and without such a combination on the second ship the
signal would have passed unheeded. How was this com-
bination discovered, and how does it work?

Faraday, as we have seen, discovered the principle of the
induction-coil. With the induction-coil a powerful electric
spark can be produced. The friction electrical machine was
known long before the time of Faraday. Franklin proved
that a stroke of lightning is like a spark from an electrical
machine, only more powerful. These great discoverers did
not know, however, that an electric spark sends out some-
thing like light which travels in all directions. They did
not know it, because they had no eyes to see this strange
light.

I will tell you a fable to make the meaning clear. There
once lived a race of blind men. Not one of them could see.
They built houses and cities, railroads and steamships,
but they did everything by touch and sound. When they
met they touched each other and spoke, and each man
knew his friend by the sound of his voice. One day a wise
man among them said he believed there was something
besides the sound of the voice with which they could make
signals to each other. Another wise man thought upon
this matter for some time and brought forth a proof that
there is something called light, though no man could see it.
Another, wiser and more practical, invented an eye which
any man could carry about with him and see the light

210

FIG, 107 MANUFACTURING DIAMONDS THIRD OPERATION

Plunging the crucible into cold water. Observe the white-hot carbon
just removed from the furnace.

THE STORY OF GREAT INVENTIONS

when he turned it in the direction from which the light
was coming. Thereafter each man carried a light that
flashed like the flashing of a firefly. Each man also carried
an eye, and each could see his friend as well as hear the
sound of his voice.

The fable is true. The light which no man had seen we
now call electric waves. The eye with which any one can
perceive this light is the receiving instrument of the wire-
less telegraph. The strange light flashed out whenever an
electric spark passed from an electrical machine, a Ley den
jar, an induction-coil, or as lightning in the clouds, but for
hundreds of years this light was unseen. The human eye
could not see it, and no artificial eye that would catch elec-
tric waves had been invented. A man in England, James
Clerk-Maxwell, first proved that there is such a light. Hein-
rich Hertz, a German, first made an eye that would catch
the waves from the electric spark, and the man who first
perfected an eye with which one could catch the electric
waves at a great distance and improved the instruments
for sending out such waves was Marconi.

The fable is true, for electric waves are like the light from
the sun. They go through space in all directions as light
does. They will not merely go through air, but through
what we call empty space, or a vacuum, as light will. If we
think of waves somewhat like water waves, but not exactly
like them, rushing through space, we have about as good a
picture of electric waves as we can well form in our minds.
As the light of a lamp goes out in all directions, so do the
electric waves go out in all directions from the place where
the electric spark passes. Since these waves go through

212

THE TWENTIETH-CENTURY OUTLOOK

what we call empty space, we must think of something in
that space and that it is not really empty. Examine an in-
candescent electric lamp. The bulb was full of air when
the carbon thread was placed in it. The air was then
pumped out until only about a millionth part remained.
The bulb was then sealed at the tip and made air-tight.
We say the space inside is a vacuum. If the bulb is broken
there is a loud report as the air rushes in. Is the bulb really
empty after the air is pumped out ? Is anything left in the
bulb around the carbon thread? Turn on the electric cur-
rent and the carbon thread becomes white hot. The light
from the white-hot carbon thread goes out through the
vacuum. There is nothing in the vacuum that we can see
or feel or handle, but something must be there to carry the
light from the carbon thread. The light of the sun comes
to the earth through ninety-three million miles of space.
Is there anything between the earth and the sun through
which this light can pass? Light, we know, is made up of
waves, and we cannot think of waves going through empty
space. There must be something between the sun and the
earth. That something through which the light of the sun
comes to the earth we call the ether. It is the ether that
carries the light across the vacuum in the light bulb as well
as from the sun to the earth. Electric waves used in wire-
less telegraphy go through this same ether. The light of
the sun is made up of the same kind of waves, and we do
not think it strange because it is so common. It is true
we do not see light waves, but they affect our eyes so that
by means of them we can see objects and perceive the flash-
ing of a light. So with the wireless receiving instrument we

213

THE STORY OF GREAT INVENTIONS

do not see the electric waves, but we perceive the flashing
of the strange light. Electric waves and light travel with
the same speed — 186,000 miles in a second. A wireless
message will go around the earth in about one-seventh of
a second.

Electric waves will go through a brick wall as readily as
sunlight will go through a glass window, but that is not so
strange as it may seem. Red light will not go through blue
glass. Blue glass holds back the red light, but lets the
blue light go through. So the brick wall holds back com-
mon light, but allows the light which we call electric waves
to go through.

Some waves on water are longer than others. So electric
waves are longer than light waves. That is the only differ-
ence between them. In fact, the light of the sun is made
up of very short electric waves. These short waves affect
our eyes, but the longer electric waves do not. We are daily
receiving the wireless-telegraph waves from the sun, which
we call light. Electric waves used in wireless telegraphy
vary from about six hundred feet to two miles in length,
while the longest light waves that affect our eyes are only
one thirty-three-thousandth of an inch in length.

The sensitive part of the Marconi receiving apparatus is
the coherer. The first coherer was made in 1890 by Prof.
Edward Branly, of the Catholic University of Paris. Very
fine metal filings were enclosed in a tube of ebonite and
connected in a circuit with a battery and a galvanometer.
The filings have so high a resistance that no current flows.
The waves from an electric spark, however, affect the filings
so that they allow the current to flow. The electric waves

214

THE TWENTIETH-CENTURY OUTLOOK

are said to cause the filings to cohere — that is, to cling to-
gether more closely. It is a peculiar form of electric weld-
ing. Branly discovered that a slight tapping of the tube
loosens the filings and stops the flow of the current.

All that was needed for wireless telegraphy was at hand.
Men knew how to produce electric waves of any desired
length. They knew how they would act. A sensitive re-
ceiver had been discovered. There was needed the prac-
tical man who should combine the parts, improve details,
and apply the wireless telegraph to actual use. This was
the work of Guglielmo Marconi. In 1894, at the age of
twenty, Marconi began his experiments on his father's
estate, the Villa Grifone, Bologna, Italy. Fig. 108 is from a
photograph of Marconi and his wireless sending and receiv-
ing instruments.

FIG. I08 MARCONI AND HIS WIRELESS-TELEGRAPH SENDING AND

RECEIVING INSTRUMENTS

215

THE STORY OF GREAT INVENTIONS

To Marconi, telegraphing through space without wires
appears no more wonderful than telegraphing with wires.
In the wire telegraph electric waves, which we then call an
electric current, follow a wire somewhat as the sound of the
voice goes through a speaking-tube. - In the wireless telegraph
the electric waves go out through space without any wire
to guide them. The light and heat waves of the sun travei
to us through millions of miles of space without requiring any
conducting wire. That electric waves should go though
space in the same way that light does is no more wonderful
than that the waves should follow all the turns of a wire.

The sending instrument used by Marconi includes an in-
duction-coil, one side of the spark-gap being connected to
the earth and the other to a vertical wire (Fig. 109). There
must be a battery of Leyden jars in the circuit of the sec-
ondary coil. The induction-coil may be operated by a
storage battery or dynamo. The vertical wire, or antenna,
is to the sending instrument what the sounding-board is to
a violin. It is needed to increase the strength of the waves.
In the wireless telegraph some wires must be used. It
is called wireless because the stations are not connected
by wires. The antenna for long-distance work consists of
a network of overhead wires. When the key is pressed a
rapid succession of sparks passes across the spark-gap. The
antenna, or overhead wire, is thus made to send out electric
waves. By pressing the key for a longer or shorter time, a
longer or shorter series of waves may be produced and a
correspondingly longer or shorter effect on the receiver. In
this manner the dots and dashes of the Morse alphabet may
be transmitted.

216

THE TWENTIETH-CENTURY OUTLOOK

O 0

Jn due t ion -c oil

Earth

FIG. lOQ DIAGRAM OF WIRELESS-TELEGRAPH SENDING APPARATUS

At the receiving station there are two circuits. One in-
cludes a coherer, a local battery, and a telegraph relay (Fig.
no). The other circuit, which is opened and closed by the
relay, includes a recording instrument and a tapper. One
end of the coherer is connected to the earth and the other
to a vertical wire like that used for the transmitter. The

217

THE STORY OF GREAT INVENTIONS

electric waves weld the filings in the coherer, and this closes
the first circuit. The relay then closes the second circuit,
the recording instrument records a dot or a dash, and the
tapper strikes the coherer and breaks the filings apart ready
for another stream of electric waves.

Coherer

Battery

FIG. 110 DIAGRAM OF MARCONI WIRELESS-TELEGRAPH RECEIVING

APPARATUS

The second circuit described in the text is not shown here. The relay
and the second circuit would take the place of the electric bell. In the
circuit as shown here the electric waves would cause the coherer to close
the circuit and ring the bell.

218

THE TWENTIETH-CENTURY OUTLOOK

With this arrangement it was possible to work only two
stations at one time. Though stations were to be estab-
lished in all the cities of Great Britain, only one message
could be sent at one time, and all stations but one must
keep silence, because a second series of waves would mingle
with the first and confusion would result.

Marconi's next effort was :o make it possible to send any
number of messages at one time. This led to his system of
tuning the sending and receiving instruments. With this
system the receiving instrument will take a message only
from a sending instrument with which it is in tune. It is
possible, therefore, for any number of wireless - telegraph
stations to operate at the same time, the waves crossing
one another in all directions without interfering, each
receiver responding to the waves intended for it. An
ocean steamer can, with the tuned system, send one mes-
sage and receive another from a different station at the
same time.

Marconi's ambition was to send a wireless message across
the Atlantic. Quietly he made his preparation, building at
Poldhu, Cornwall, England, a more powerful transmitter
than had yet been used. At noon on the i2th of December,
1901, he sat in a room of the old barracks on Signal Hill,
near St. Johns, Newfoundland, waiting for a signal from
England. His assistants at the Poldhu station were to
telegraph across the ocean the letter ' ' S " at certain times
each day. On the table was the receiving apparatus, made
very sensitive, and including a telephone receiver. A wire
led out of the window to a huge kite, which the furious wind
held four hundred feet above him. One kite and a balloon

219

THE STORY OF GREAT INVENTIONS

used for supporting the antenna had been carried out to
sea. He held the telephone receiver to his ear for some
time. The critical time had come for which he had worked
for years, for which his three hundred patents had prepared
the way, and for which his company had erected the costly
power station at Poldhu. Calmly he listened, his face
showing no sign of emotion. Suddenly there sounded the
sharp click of the tapper as it struck the coherer. After a
short time Marconi handed the telephone receiver to his
assistant. "See if you can hear anything," he said. A
moment later, faintly and yet distinctly, came the three
little clicks, the dots of the letter "S" tapped out
an instant before in England. Marconi's victory was
won.

A flying-machine can de equipped with a wireless-tele-
graph outfit, so that a man can telegraph while flying
through the air. Two men are needed, one to operate the
flying-machine, the other to send the telegraphic messages.
This has been done with the Wright machine and with some
dirigible balloons. Of course, the wireless instruments on
the flying-machine cannot be connected to the ground. In-
stead of the ground connection there is a second antenna,—
one antenna on each side of the spark-gap. While in the
ordinary wireless instruments the discharge surges back
and forth between the antenna and the earth, in the flying-
machine wireless the discharge surges back and forth be-
tween the two antennae. In the Wright machine, when
equipped for wireless telegraphy, the two antennae are
placed one under the upper plane, the other under the lower
plane of the flying-machine.

THE TWENTIETH-CENTURY OUTLOOK

More power is required for the wireless than for the wire
telegraph. In the wire telegraph about one-hundredth
horse-power is required to send a message one hundred and
twenty miles. To send a message the same distance with
the wireless requires about ten horse-power, or a thousand
times as much as with the wire telegraph. This is because
in the wireless telegraph the waves go out in all directions,
and much of the power is wasted. In the wire telegraph
the electric waves are directed along the wire and very little
of the power is wasted. For the same reason a person's
voice can be heard a long distance through a speaking-tube.
The speaking-tube guides the sound and prevents it from
scattering somewhat as the wire guides the electric waves.

The overhead wires of a wireless-telegraph station send
out a "dark" light while a message is being sent. (See
frontispiece.) Standing near the station on a dark night
one can see nothing, but can hear only the terrific snapping
of the electric discharge. The camera, however, shows that
light goes out from the wires. It is light of shorter waves
than any that the eye can perceive, but the sensitive film
of the photographic plate makes it known to us.

The Wireless Telephone

In sending a message by the wire telegraph the current
flows over the line wire when the key is pressed. When the
key is released the current stops. The circuit is made and
broken for every dot or dash. This we may call an inter-
rupted current. Now we have seen that the attempt to
invent a wire telephone using an interrupted current failed.

221

THE STORY OF GREAT INVENTIONS

While one is talking over the wire telephone a current
(alternating) must be flowing over the line wire. The sound
of the voice does not make and break the circuit, but
changes the strength of the current. This alternating cur-
rent is wonderfully sensitive. It can vary in the rate at
which it alternates or the number of alternations per second
to correspond to sound of every pitch. It varies in strength
to correspond to all the variations in the voice, and repro-
duces in the receiver not merely the words that are spoken
but the quality of the voice, so that the voice of a friend
can be recognized by telephone almost as well as if talking
face to face.

The same things are true of the wireless telegraph and
telephone. Instead of an electric current, let us say ''a
stream of electric waves." Then we may say of the wire-
less everything that we have said of the wire telegraph and
telephone. In sending a message by wireless telegraph the
stream of electric waves flows when the key is pressed and
stops when the key is released. We have an interrupted
stream of felectric waves. But an interrupted stream of
waves cannot be used for a wireless telephone any more
than an interrupted current can be used for a wire-telephone.
There must be a constantly flowing stream of electric waves,
and these waves must be changed in strength and form by
the sound of the voice. Fig. in shows a wireless-telephone
receiver in which light is used to carry the message. The light
acts on the receiver in such a way as to reproduce the sound.

In the wireless-telegraph receiver the interrupted stream
of electric waves makes and breaks the circuit of an electric
battery. The wireless-telephone receiver must not make

222

> M

_. o

p. a

S i

a »

1 §

CD W

THE STORY OF GREAT INVENTIONS

and break a circuit, but it must be sensitive to all the
changes in the electric waves. One such receiver is the
audion, which we shall now describe.

The audion was invented by Dr. Lee de Forest. De
Forest had taken the degree of Doctor of Philosophy at
Yale University, having written his thesis for that degree

Telephone
receiver

FIG. 112 A GAS FLAME IS SENSITIVE TO ELECTRIC WAVES

on the subject of electric waves. He then entered the em-
ploy of the Western Electric Company in Chicago, and while
in this position worked at night in his room on experiments
with electric waves.

Here he found that a gas flame is sensitive to electric
waves (Fig. 112). If a gas flame is made part of the circuit

224

THE TWENTIETH-CENTURY OUTLOOK

of an electric battery, which includes also an induction-coil
connected to a telephone receiver, then when a stream of
electric waves comes along there is a click in the receiver.
The waves change the resistance of the flame, and so change
the strength of the current. The flame is a simple audion.
It is the heated gas in the flame that responds to the electric
waves.

If instead of a gas flame an incandescent-light bulb is
used having a metal filament, and on either side of the fila-
ment a small strip of platinum, a more sensitive receiver is
obtained. This is the audion, which is the distinguishing
feature of the De Forest wireless telegraph and wireless
telephone. The metal filament is made white hot by the
current from a storage battery. The vacuum in the bulb is
about the same as that of the ordinary incandescent electric
light. A very small quantity of gas is therefore left in the
bulb. The electrified particles of gas respond more freely
to electric waves in this bulb than in the gas flame.

The De Forest wireless telephone was adopted for use
in the United States Navy shortly before the cruise around
the world in 1908. Every ship in the navy was equipped
with the wireless telephone, enabling the Admiral to talk
with the officers of any vessel up to a distance of thirty-five
miles. The wireless telephone in use on a battle-ship is
shown in Fig. 113.

Wonders of the Alternating Current

Before the days of the electric current, men used the
power of falling water, The mill or factory using the water-

225

THE STORY OF GREAT INVENTIO NS_

power was placed beside the fall. The water turned a great
wheel, to which was connected the machinery of the mill.
It was not until the invention of the dynamo and motor
that water-power could be used at a great distance. If a

FIG. 113 CAPTAIN INGERSOLL ON BOARD THE U. S. BATTLE-SHIP

"CONNECTICUT" USING THE WIRELESS TELEPHONE

hundred years ago a man had said that the time would come
when a waterfall could turn the wheels of a mill a hundred
miles away he would have been laughed at. Yet this very

226

THE TWENTIETH-CENTURY OUTLOOK

thing has come to pass. Indeed, one waterfall may turn
the wheels of many factories, run street -cars, and light
cities up to a distance of a hundred miles and even more.
The power of the falling water goes out over slender copper
wires from a great dynamo near the fall to the motors in
the factories and street-cars.

The falling water of Niagara has about five million horse-
power. About the hundredth part of this power is now
being used. The water, falling in a wheel-pit 141 feet deep,
turns a great dynamo weighing 87,000 pounds with a speed
of 250 turns per minute. A number of such dynamos are
used supplying an alternating current at a pressure of
22,000 volts, the current alternating or changing direction
twenty-five times per second. Such a pressure is too high
for the motors and electric lights, but the current is carried
at high pressure to the place where it is to be used and
there transformed to a current of low pressure. In carry-
ing a current over a long line, there is less loss if the cur-
rent is carried at high pressure. With an alternating
current this can be done and the current changed by
means of a transformer to a current of low pressure.

A transformer is simply two coils of wire wound on an
iron core. The simplest transformer is the form used by
Faraday when he discovered electromagnetic induction. If
instead of making and breaking a circuit that flows only in
one direction as Faraday did, we cause an alternating cur-
rent to flow through one of the coils, which we may call the
primary, each time the current changes direction in the
primary the magnetic field is reversed — that is, the end of
the coil which was the north pole becomes the south pole.

227

THE STORY OF GREAT INVENTIONS

This rapidly changing magnetic field induces a current in
the secondary coil. Each time the magnetic field of the
primary coil is reversed the current in the secondary changes
direction. Thus an alternating current in the primary in-
duces an alternating current in the secondary. One of these
coils is of fine wire, which is wound a great many times
around the iron. The other is of coarser wire wound only
a few times around the iron. Suppose the current is to be
changed from high pressure to low pressure. Then the high-
pressure current from the line is made to flow through the
coil of many turns, and a current of low pressure is given out
from the coil of few turns. By changing the number of
turns of wire in the coils we can make the pressure whatever
we please. If the pressure or voltage of the secondary coil
is less than that of the primary, we have a " step-down"
transformer. On the other hand, if we send the current
from the line wire through the coil of few turns, then we
get a higher voltage from the secondary coil than that of the
line wire, and we have a "step-up" transformer. The
Niagara current is "stepped down" from 22,000 volts to
220 volts for use in motors.

An electric lamp may be lighted though not connected to
any battery or dynamo, but connected only to a coil of
wire (Fig. 114). More than this, the coil may be insulated
so that no current can enter it from any other coil or wire,
and yet the lamp can be lighted. This can be done only by
means of an alternating current. If the coil to which the
lamp is connected is held in the magnetic field of an alter-
nating current, then another alternating current is induced
in the coil, and this second current flows through the lamp.

228

THE TWENTIETH-CENTURY OUTLOOK

FIG. 114 INCANDESCENT ELECTRIC LAMP LIGHTED THOUGH NOT CON-
NECTED TO ANY BATTERY OR DYNAMO

We have already learned that a changing magnetic field in-
duces a current in a coil. Now the coil through which an
alternating current is flowing has a changing magnetic field
all around it, and if the lamp-coil is brought into this
changing magnetic field an alternating current will flow
through the coil and the lamp. The insulation on the
lamp-coil does not prevent the magnetic field from acting,

229

THE STORY OF GREAT INVENTIONS

though it does prevent a current from entering the coil.
The current is induced in the coil itself, and does not enter
it from any outside source.

The transformer works in the same way, the only differ-
ence being that in the transformer the two coils are on the

FIG. 115— AN ELECTRIC DISCHARGE AT A PRESSURE OF I2,OOO,OOO VOLTS,
A CURRENT OF 8oO AMPERES IN THE SECONDARY COIL

same iron core. But in the transformer the two coils are
insulated so that no current can flow from one coil to the
other. When an alternating current and transformers are
used, .the current that lights the lamps in the houses or on
the streets is not the current from the dynamo. It is a new

230

THE TWENTIETH-CENTURY OUTLOOK

current induced in the secondary coil of the transformer by
the magnetic field of the primary coil.

A peculiar transformer which produces an alternating
current that changes direction millions of times in a second
has been made by Nikola Tesla. This current will do many
wonderful things which no ordinary current will do. It
will light a room or run a motor without connecting
wires. It has produced an electric discharge sixty -five
feet in length (Figs. 115 and 116). Though this current
is caused to flow by a pressure of millions of volts, it may
be taken with safety through the human body. Strange as
it may seem, the safety of this current is due to the high

FIG. Il6. \N ELECTRIC DISCHARGE SIXTY-FIVE FEET IN LENGTH

231

THE STORY OF GREAT INVENTIONS

pressure and the rapidity with which it changes direction.
While the current used at Sing Sing in executing criminals
has a pressure of about twenty-five hundred volts, a current
having a pressure of a million volts and alternating hundreds
of thousands or millions of times per second is harmless.
With such a current the human body may become a "live
wire," and an electric lamp to be lighted held in one hand
while the other hand grasps the wire from the transformer.

X-Rays and Radium

A strange light which passes through the human body as
readily as sunlight through a window was discovered by
Prof. Wilhelm Konrad Roentgen, of the University of Wiirz-
burg. This light, which Professor Roentgen named X-rays,
is given out when an electric discharge at high pressure
passes through a certain kind of glass tube from which the air
has been pumped out until there is a nearly perfect vacuum.

X-rays were discovered by accident. Professor Roentgen
was working at his desk with one of the glass tubes when
he was called to lunch. He laid the tube with the electric
discharge passing through it on a book. Returning from
lunch he took a photographic plate-holder which was under
the book and made some outdoor exposures with his
camera. On developing the plates a picture of a key ap-
peared on one of them. He was greatly puzzled at first,
but after a search for the key found it between the leaves
of the book. The strange light from the electric discharge
in the glass tube had passed through the book and the hard-
rubber slide of the plate-holder and made a shadow-picture

232

FIG. 117 A PHYSICIAN EXAMINING THE BONES OP THE ARM BY MEANS

OP X-RAYS

THE STORY OF GREAT INVENTIONS

of the key on the photographic plate. He tried the strange
light in many ways, and found that it would go through
many objects. It would even go through the human body,
so that shadow-pictures of the bones and organs of the
body could be obtained. In Fig. 117 is shown a physician
using X-rays. Fig. 118 is an X-ray photograph of the eye.

FIG. Il8 X-RAY PHOTOGRAPH OF THE EYE

The eye is above and to the left of the larger black circle. The smaller
black circle is a shot which has lodged back of the eye.

Not long after the discovery of X-rays it was discovered
that light very much like the X-rays is given out by certain
minerals. One of the most interesting and the best known
of these is radium. Radium gives out a light somewhat
like X-rays that will go through copper and other metals.
It does many other strange things. It gives out heat as

234

THE TWENTIETH-CENTURY OUTLOOK

well as light; so much heat, in fact, that it is always about
five degrees warmer than the air around it. It continues
to give out heat at such a rate that a pound of radium will
melt a pound of ice every hour. It can probably keep this
up for at least a thousand years. If this, heat could be
used in running an engine, a hundred pounds of radium
would run a one-horse-power engine without stopping for
many hundred years. The power of Niagara might be re-
placed by the power of radium if an engine that could use
this power were invented. Fig. 119 is from a photograph
made with radium.

FIG. 119 PHOTOGRAPH MADE WITH RADIUM

A purse containing a coin. The strange light from the radium goes
through the purse and the slide of the plate-holder and makes a shadow-
picture.

235

THE STORY OF GREAT INVENTIONS

The great inventor of the future may be able to use the
heat of radium or some new power now unknown. We
have seen how, through the toil of many years and the
labors of many men, the great inventions of our age have
come into being. It may be that we are now witnessing
other great inventions in the making.

APPENDIX

BRIEF NOTES ON IMPORTANT INVENTIONS

Aerial Navigation

air balloon — Montgolfier Brothers, France, 1783.

1 First balloon ascension — Rozier, France. 1783.

First gas balloon — Charles, France, 1783.

First crossing of the English Channel in a balloon — Blanchard, 1785.

First successful dirigible balloon — La France, Renard and Krebs,
France, 1884.

First successful motor-driven aeroplane — Wright Brothers, United
States; date of patent, 1906.

First crossing of the English Channel by an aeroplane — Bleriot, 1909.

First air-ship in regular passenger service — Count Zeppelin, Ger-
many, 1910.

Agriculture

Plough with cast-iron mold-board ' and iron shares — James Small,
Scotland, 1784.

Grain-threshing machine — Andrew Meikle, England, 1788.

McCormick reaper, first practical grain - harvesting machine —
Cyrus H. McCormick, United States, 1831.

Self -raker for harvesters — McCormick, 1845.

Inclined platform and elevator in the reaper, to enable men bind-
ing the grain to ride with the machine — J. S. Marsh, United
States, 1858.

Barbed-wire fence introduced — United States, 1861.

Self-binder, first automatic grain-binding device for the reaper —
Jacob Behel, United States, 1864.

Sulky plough — B. Slusser, United States, 1868.

237

THE STORY OF GREAT INVENTIONS

Twine-binder for harvesters — M. L. Gorham, United States, 1873.
Improved self-binding reaper — Lock and Wood, United States, 1873.
Barbed-wire machine — Glidden and Vaughn, United States, 1874.
Rotary disk cultivator — Mallon, United States, 1878.
Steam-plough — W. Foy, United States, 1879.

Combined harvester and thresher — Matteson, United States, 1886.
Automobile mower — Deering Harvester Company, United States,
1901.

Automobile

First steam-automobile — Cugnot, France, 1769.

First chain transmission of power in an automobile — Gurney,
England, 1829.

Application of gas-engine to road vehicles, beginning of the modern
motor-car — Gottlieb Daimler and Carl Benz working independ-
ently, Germany, 1886. Daimler's invention consisted of a
two-cylinder air-cooled motor. It was taken up in 1889 by
Panhard and Levassor, of Paris, who began immediately the
construction of the motor-car. This was the beginning of the
motor-car industry.

Bicycle

First bicycle— Branchard and Magurier, France. 1779.
Rear-driven chain safety bicycle — George W. Marble, United States,

1884.
Bicycles first equipped with pneumatic tires — 1890.

Electrical Inventions

William Gilbert, England, 1540-1603, called " the father of magnetic
philosophy," first to use the terms "electric force," "electric
attraction," "magnetic pole."

First electrical machine, a machine for producing electricity by
friction — Otto von Guericke, Germany, about 1681.

Discovery of conductors and insulators — Stephen Gray, England,
1696-1736.

First to discover that electric charges are of two kinds — Cisternay
du Fay, France, 1698-1739; Du Fay was also the first to at-
tempt an explanation of electrical action. He supposed that
electricity consists of two fluids which are separated by friction,

238

APPENDIX

and which neutralize each other when they combine. This
theory was more fully set forth by Robert Symmer.

Leyden jar — Discovered first by Von Kleist in 1745. The same
discovery was made and the Leyden jar brought to the atten-
tion of the public in 1 746 by Pieter van Musschenbroek in Holland.

Lightning-rod — Benjamin Franklin, 1732.

Electroplating — Luigi Brugnatelli, Italy, 1805.

Voltaic arc, a powerful arc light produced with a battery current —
vSir Humphry Davy, England, 1808.

Storage battery — Ritter, Germany, 1803. Platinum wires were
dipped in water and a battery current passed through. Hydro-
gen collected on one wire and oxygen on the other. If the
platinum wires were disconnected from the battery and con-
nected with each other by a conductor, the two wires acted
like the plates of a battery, and a current would flow for a short
time in the new circuit.

Electromagnetism discovered — H. C. Oersted, Denmark, 1819.

Galvanometer, a coil of wire around a magnetic needle for measur-
ing the strength of an electric current — Schweigger, Germany,
1820.

Motion of magnet produced by an electric current — M. Faraday,
England, 1821.

Thermo-electricity, an electric current produced by heating the
junction of two unlike metals — Discovered by Professor See-
beck, England, 1821.

Principles of electrodynamics, motion produced by an electric cur-
rent— Ampere, France. Announced in 1823.

Law of electric circuits, Ohm's law, current strength equals electro-
motive force divided by resistance of the circuit — George S.
Ohm, Germany. Proven by experiment in 1826 ; mathematical
proof published in 1827.

Magnetr - Metric induction, induction of electric currents by means
01 a magnetic field — M. Faraday, England, 1831.

F1jctric telegraph — Prof. S. F. B. Morse, United States, 1832.

First telegram sent in 1844 — Morse.

Constant electric battery — J. P. Daniell, England, 1836.

First electric motor-boat — Jacobi, Russia, 1839.

Induction-coil — Rhumkorff, Germany, 1851.

Duplex telegraph, first practical system — Stearns, United States,
about 1855-1860.
16 239

THE STORY OF GREAT INVENTIONS

Storage battery, lead plates in sulphuric acid — Gaston Plante,
France, 1859.

Telephone, make-and-break system, first electrical transmission of
speech — Philip Reiss, Germany, 1860.

Atlantic cable laid — Cyrus W. Field, 1866.

Dynamo, armature coil rotates in the field of an electromagnet,
armature supplies current for the electromagnet as well as
for the external circuit — William Siemens, Germany, 1866.

Gramme ring armature for dynamo — Gramme, France, 1868.

Theory that light consists of electromagnetic waves — Clerk- Max-
well, England, 1873.

Quadruplex telegraph, sending four messages over one wire at the
same time — Edison, 1873.

Siphon recorder for submarine telegraph, sensitive to very feeble
currents — Sir William Thomson, England, 1874.

Telephone, varying current, first practical working telephone —
Alexander Graham Bell, United States, 1876.

Electric candle, beginning of present arc light — Paul Jablochkoff,
Russia, 1876.

Telephone transmitter of variable resistance — Emil Berliner and
Edison working independently, United States, 1877. Edison
used carbon contacts, Berliner used metal contacts.

Brush system of arc lighting — 1878.

Incandescent electric lamp with carbon filament — Edison, 1878.

First electric locomotive — Siemens, Germany, 1879.

Blake telephone transmitter — Blake, United States, 1880.

Storage battery, lead grids filled with active material — Faure,
France, 1881.

Electric welding — Elihu Thompson, United States, 1886.

Electric waves discovered by experiment — Heinrich Hertz, Ger-
many, 1888.

Coherer for receiving electric waves — Edward Branly, France,
1890.

X-rays — Discovered by Prof. W. C. Roentgen, Germany; announced
to the public in 1895.

Wireless telegraphy — G. Marconi, Italy, 1896. v

Nernst electric light, a clay capable of conducting electricity when
heated is used; it becomes incandescent without a vacuum —
Walter Nernst, Germany, 1897.

Radium discovered by Madame Curie, France, 1898.

240

APPENDIX

Explosives

Gunpowder — Inventor and date unknown.

Guncotton — Schonbein, Germany, 1845.

Nitroglycerine — Sobrero, 1847. ..•*.

Explosive gelatine — A. Nobel, France, 1863.

Dynamite — A Nobel, France, 1866.

Smokeless powder — Vielle, France, 1866.

Firearms and Ordnance

Spirally grooved rifle barrel — Koster, England, 1620.

Breech-loading shot-gun — Thornton and Hall, United States, 1811.

The revolver; a device "for combining a number of long barrels
so as to rotate upon a spindle by the act of cocking the ham-
mer"— Samuel Colt, United States, 1836.

Breech gun-lock, interrupted thread — Chambers, United States, 1849.

Magazine gun — Walter Hunt, United States, 1849.

Breech-loading rifle — Maynard, United States, 1851.

Iron-clad floating batteries first used in Crimean War — 1855.

Breech-loading ordnance — Wright and Gould, United States, 1858.

Revolving turret for floating batteries — Theodore Timby, United
States, 1862.

First iron-clad floating battery propelled by steam: the Monitor —
John Ericsson, United States, 1862.

Gatling gun — Dr. R. J. Gatling, United States, 1862.

Automatic shell-ejector for revolver — W. C. Dodge, United States,
1865.

Torpedo — Whitehead, United States, 1866.

Disappearing gun-carriage — Moncrief, England, 1868.

Rebounding gun-lock — L. Hailer, United States, 1870.

Magazine rifle — Lee, United States, 1879.

Hammerless gun — Greener, United States, 1880.

Gun silencer, to be attached to barrel of gun; gun can be fired
without noise — Maxim, 1909.

Gas Used for Light and Power

Gas first used for illuminating purposes — William Murdoch, England,

1792.

First street gas-lighting in England — F. A, Winsor, 1814.

241

THE STORY OF GREAT INVENTIONS

Gas-meter — S. Clegg, England, 1815.

Water-gas, prepared by passing steam over white-hot anthracite

coal — First produced in England in 1823.
Illuminating water-gas — Lowe, United States, 1875.
Gas-engine, 4-cycle, beginning of modern gas-engine — Otto and

Langen, Germany, 1877.
Incandescent gas-mantle — Carl A. von Welsbach, Austria, 1887.

Iron and Steel

Blast-furnace, beginning of iron industry — Belgium, 1340.

Use of coke in blast - furnace — Abram Darly, England, about
1720.

Puddling iron — Henry Cort, England, 1783-84.

Process of making malleable-iron castings — Lucas, England, 1804.

Hot-air blast for iron furnaces — J. B. Neilson, Scotland, 1828.

The galvanizing of iron — Henry Craufurd, England, 1837.

Process of making steel, blowing air through molten pig-iron to
burn out carbon, then adding spiegel iron; first production of
cheap steel — Sir Henry Bessemer, England, 1855.

Regenerative furnace, a gas-furnace in which gas and air are
heated before being introduced into the furnace, giving an
extremely high temperature — William Siemens, England,
1856.

Open-hearth process of making steel — Siemens-Martin, England,
1856.

Nickel steel, much stronger than ordinary steel, used for armor-
plate — Schneider, United States, 1889.

Mining

Miners' safety-lamp — Sir Humphry Davy, England, 1815.

Compressed-air rock-drill — C. Burleigh, United States, 1866.

Diamond rock-drill, a tube of cast-steel with a number of black
diamonds set at one end. The machine cuts a circular groove,
leaving a core inside the tube. This core is brought to the
surface with a rod, and the powdered rock is washed out by
water forced down the tube and flowing up the sides of the
hole. The drill does not have to stop for cleaning out — Her-
man, United States, 1854.

242

APPENDIX

Photography

First photographic picture, not permanent — Thomas Wedgewood,

England, 1791.
Daguerreotype, first developing process — Louis Daguerre, France,

1839-
First photographic portraits, daguerreotype process — Prof. J. W.

Draper, United States, 1839.

Collodion process in photography — Scott Archer, England, 1849.
Photographic roll films — Melhuish, England, 1854.
Dry-plate photography — Dr. J. M. Taupenot, 1855.
Photographic emulsion, bromide of silver in gelatine, basis of

present rapid photography — R. L. Maddox, England, 1871.
Hand photographic camera for plates — William Schmid, United

States, 1 88 1.

Printing

First printing with movable types in Europe and first printing-
press — Guttenberg, Germany, about 1445.

Screw printing-press — Blaew, Germany, 1620.

First newspaper of importance — London Weekly Courant, 1625.

Stereotyping, making plates from casts of the type after it is set
up — William Ged, Scotland, 1731.

First practical steam rotary printing-press, paper printed on both
sides, 1800 impressions per hour — Frederick Koenig, Ger-
many, 1814.

Printing from curved stereotype plates — H. Cowper, England, 1815.

Hoe's lightning press, 2000 impressions per hour — R. Hoe, United
States, 1847.

Printing from a continuous web, paper wound in rolls, both sides
printed at once — William Bullock, United States, 1865.

" Straightline newspaper perfecting" press, prints 100,000 eight-
page papers her hour — Goss Company, United States.

Linotype machine. The operator uses a keyboard like that of a
typewriter. The machine sets the matrices which correspond
to the type, casts the type in lines from molten metal, delivers
the lines of type on a galley, and returns the matrices to their
appropriate tubes. It does the work of five men setting type
in the ordinary way — Othmar Mergenthaler, United States,
1890.

243

THE STORY OF GREAT INVENTIONS

Steam Navigation

First steamboat in the world — Papin, River Fulda, Germany, 1705.
First steamboat in America — John Fitch, Delaware River, 1783.
First passenger steamboat in the world, the Clermont — Robert

Fulton, Hudson River, 1807.
First steamer to cross the Atlantic, the Savannah, built at New York

— First voyage across the Atlantic, 1819.
The screw propeller first used on a steamboat — John Ericsson,

United States, about 1836.

Compound engines adopted for steamers — 1856.
First turbine-steamer, the Turbinia — Parsons, 1895.
First mercantile steam-turbine ship, the King Edward — Denny and

Brothers, England, 1901.

Steam Used for Power and Land Transportation

First steam-engine with a piston — Denys Papin, France, 1690.

First practical application of the power of steam, pumping water —
Thomas Savery, England, 1698.

Double-acting steam-engine and condenser — James Watt, Scotland,
1782.

Steam-locomotive first used to haul loads on a railroad — Richard
Trevethick, England, 1804.

First passenger steam railway, the "Stockton & Darlington "-
George Stephenson, England, 1825.

First steam - locomotive in the United States, the "Stourbridge
Lion" — 1829.

Link motion for locomotives — George Stephenson, England, 1833.

Steam -whistle, adopted for use on locomotives — George Stephen-
son, 1833.

Steam-hammer — James Nasmyth, Scotland, 1842.

Steam-pressure gauge — Bourdon, France, 1849.

Corliss engine — G. H. Corliss, United States, 1849.

First practical steam-turbine — C. A. Parsons, England, 1884.

Textile Industries

Flying shuttle, first important invention in weaving, leading to
modern weaving machinery — John Kay, England, 1733.

244

APPENDIX

Spinning-jenny — James Hargreaves, England, 1763.

Power loom — James Cartwright, England, 1785.

Cotton-gin, for separating the seeds from the fibre, gave a new

impetus to the cotton industry. The production of cotton

increased in five years from 35,000 to 155,000 bales — Eli

Whitney, United States, 1792.
Pattern loom, for the weaving of patterns — M. J. Jacquard, France,

1801.
Application of steam to the loom — William Horrocks, England,

1803.

Knitting-machine — Brunei, England, 1816.
Sewing-machine — Elias Howe, United States, 1846.
Mercerized cotton — John Mercer, England, 1850.
Process of making artificial silk — H. de Chardonnet, France, 1888.

Wood-Working

Circular wood-saw — Miller, England, 1777.

Wood-planing machine — Samuel Benthem, England, 1791.

Wood-mortising machine — M. J. Brunei, England, 1801.

Band wood-saw — Newberry, England, 1808.

Lathe for turning irregular wood forms — Thomas Blanchard, United

States, 1819.
Improved planing-machine — William Woodworth, United States,

1828.

Miscellaneous

First fireproof safe — Richard Scott, England, 1801.

Steel pen, quill pen used up to this time — Wise, England, 1803.

First life-preserver — John Edwards, England, 1805.

Calculating machine — Charles Babbage, England, 1822.

First friction matches — John Walker, United States, 1827. Flint
and steel were used for starting fires before matches were
invented.

First portable steam fire-engine — Brithwaite and Ericsson, Eng-
land, 1830.

Vulcanizing of rubber — Charles Goodyear, United States, 1839.

Pneumatic tire — R. W. Thompson, England, 1845.

Time-lock for safes — Savage, United States, 1847.

Match-making machinery — A. L. Denison, United States, 1850.

245

THE STORY OF GREAT INVENTIONS

American machine-made watches — United States, 1850.

Safety matches — Lundstrom, Sweden, 1855.

Sleeping-car — Woodruff, United States, 1856.

Printing-machine for the blind, origin of the typewriter — Alfred E.
Beach, United States, 1856.

Cable-car — E. A. Gardner, United States, 1858.

Driven well, an iron tube with the end pointed and perforated
driven into the ground — Col. N. W. Green, United States, 1861.

Passenger elevator — E. G. Otis, United States, 1861.

First practical typewriter — C. L. Sholes, United States, 1861.

Railway air-brake, use of air-pressure in applying brakes to the
wheels of a car. A strong spring presses the brake against
the wheels. Air acts against the spring and holds the brake
away from the wheels. To apply the brake, air is allowed to
escape, reducing the pressure and allowing the spring to act —
George Westinghouse, United States, 1869.

Store-cash carrier — Dr. Brown, United States, 1875.

Roller flour-mills — F. Wegman, United States, 1875.

Kinetoscope, moving-picture machine — Edison, 1893.

INDEX

AEROPLANE, 184.

Air-pressure, 23.

Air-pump, 20.

Air- ships, 173.

Air thermometer, 13.

Alternating current, wonders of,

225.

Amber, 8.
Ampere, 67, in.
Arago, 69.

Archimedes, i, 12; inventions of, 7.
Archimedes' principle, 6, 12.
Arc light, 120.
Armature, 101, 103, 104.

BALLOONS, 174.

Barometer, mercury, 19, 25; water,

23-

Battle of Syracuse, 2.
Bell, Alexander Graham, 141.
Blake transmitter, 146.
Bleriot, 190.
Boyle, 23.
Branly, 214.

CANNON EXPERIMENT, Rumford's, 59.
Cog-wheels, first used, 8.
Coherer, 214.
Colors in sunlight, 31.
Condenser in steam-engine, 40.
Conductors, electrical, 44.
Controller, 116.

DANIELL CELL, 89, 127.
Davy, 56, 6 1, 96.
De Forest, 224.

Diamonds, manufacturing, 206.

Drum armature, 104.

Dry battery, 91.

DuFay, 45.

Dumont, 179.

Duplex telegraphy, 136.

Dynamo, 55, 79, 81, 96, 99, 100,
105, in; series wound, 105 ; shunt
wound, 107; compound wound,
108.

EDISON, 95, 105, 114, 121.
Electrical machine, 23, 44, 45, 83.
Electric battery, 53, 62, 84, 89.
Electric charge, two kinds, 45.
Electric current, 50, 69, 73, 74, 82,

96; magnetic action of, 66, 68;

produced by a magnet, 72.
Electric furnace, 205.
Electricity, 8, 50; theories of, 49;

speed of, 133.
Electric lighting, 97, 118.
Electric motor, 71, 97, in.
Electric power, in.
Electric railway, 112.
Electric waves, 212.
Electromagnet, 100, 126, 143.
Electromagnetism, 65.

FARADAY, 55, 63, 100, in; elec-
trical discoveries, 64.
Force-pump, 8.
Franklin, 43, 45, 46, 65.

GALILEO, 9, 63; experiment with
falling shot, 12.

247

THE STORY OF GREAT INVENTIONS

Galvani, 50.
Galvanometer, 74 , 75.
Gas-engines, 150.
Glider, 186.
Governor, fly-ball, 42.
Gramme-ring armature, 103.
Gravitation, 30.
Gravity cell, 91.
Gray, Stephen, 44.
Guericke, 20, 35.
Gyroscope, 200.

HEAT, 59.

Henry, Joseph, 97, 127.

Hero, 8, 164; engine, 164.

Hiero, King of Syracuse, i, 6.

Horse-power, 40.

Hydraulic press, 26.

INCANDESCENT LIGHT, 121.
Indicator, 41.
Induction-coil, 76, 82, 99.
Induction, electrical, 74.
Insulators, 44.

Inventions of the ancient Greeks,
7; of the nineteenth century, 88.

KITE EXPERIMENT, Franklin's, 46.
Kites, 27.

LEYDEN JAR, 43.
Lightning-rod, 48.
Lines of force, 99.

/Liquid air, 203.
/ Locomotive, electric,

114; steam, 155.

MAGDEBURG, 21.
Magnetic field, 80, 99.
Magnets, 8, 130.
Marconi, 215.
Mayer, Robert, 61, 85.
Mercury vapor light, 125.
Microscope, 18.
Miner's safety lamp, 61.
Monorail car, 201.
Morse, 128.

NAPOLEON, 62.
Newcomen, 34, 36.
Newcomen's engine, 36.

Newton, 27.
Niagara, 227

OERSTED, 65, 71, m, 126.

PAPIN, 35.

Papin's engine, 35.

Pascal, 25.

Pendulum clock, 10, 12.

Perpetual motion impossible, 87.

Phonograph, 147.

Principle of work, 19.

Prism, 3 1 .

Pump, 8, 19.

RADIUM, 232.

Reis, Philip, 141.

Relay, 130.

Roentgen, 232.

Royal institution, 56, 61.

Rumford, 57, 59.

Rumford's cannon experiment, 59.

SAFETY-LAMP, 62.
Screw propeller, 171.
Siemens', 100.
Spinning tops, 199.
Steam-engine, 8, 25, 34. , /
Steam locomotive, 155.
Steam pressure, 23.
Stephenson, 156.
Storage battery, 93.
Sturgeon, 97, 127.
Submarines, 190.
Suction-pump, 8.
Symmer, Robert, 49.

TELEGRAPH, 96, 126; wireless, 208.
Telephone, 140; wireless, 221.
Telescope, invention of, 15; New-
ton's 32.
Tesla, 231.

Thermometer, air, 13.
Torpedo, 192.
Torricelli, 19, 35.
Transformer, 80, 82, 99, 227.
Turbine, 163.

UNIVERSITY OF PADUA, 13.
University of Pisa, 10, 12.

248

INDEX

Valve-gear, 37, 162.
Volta, 53, 63, 89.
Voltaic battery, 53, 89.

WATER-CLOCK, 8, 29.
Water-wheel, 165.
Watt, James, 34.

Watt's engine, 38.
Wireless telegraph, 208.
Wright aeroplane, 188.

X-RAYS, 232.
ZEPPELIN, 180.

THE END

TK1

14 DAY USE

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APR 91970

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UNIVERSITY OF CALIFORNIA LIBRARY

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