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Title: Electricity for Boys

Author: James Slough Zerbe

Release date: September 25, 2007 [eBook #22766]
Most recently updated: March 2, 2013

Language: English

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*** START OF THE PROJECT GUTENBERG EBOOK ELECTRICITY
FOR BOYS ***

WARNING: This book of one hundred years ago
describes
experiments which are too dangerous to attempt
by either
adults or children. It is published for historical
interest only.

The "How-to-do-it" Books

ELECTRICITY FOR BOYS

Fig. 1. WORK BENCH

THE "HOW-TO-DO-IT" BOOKS

ELECTRICITY FOR
BOYS

A working guide, in the successive
steps of electricity, described in
simple terms
WITH MANY ORIGINAL
ILLUSTRATIONS

By J. S. ZERBE, M.E.

AUTHOR OF
CARPENTRY FOR BOYS PRACTICAL MECHANICS FOR
BOYS

THE NEW YORK BOOK COMPANY
New York

Copyright, 1914, by
THE NEW YORK BOOK COMPANY

p. i

CONTENTS

Introductory Page 1

I. Electricity Considered. Brief Page 5
Historical Events
The Study of Electricity. First Historical
Accounts. Bottling Electricity. Discovery of
Galvanic Electricity. Electro-motive Force.
Measuring Instruments. Rapidity of Modern
Progress. How to Acquire the Vast Knowledge.
The Means Employed.

II. What Tools and Apparatus are Needed Page 11

Preparing the Workshop. Uses of Our
Workshop. What to Build. What to Learn.
Uses of the Electrical Devices. Tools. Magnet-
winding Reel.

III. Magnets, Coils, Armatures, Etc. Page 18

The Two Kinds of Magnets. Permanent
Magnets. Electro-Magnets. Magnetism.
Materials for Magnets. Non-magnetic
Material. Action of a Second Magnet. What
North and South Pole Mean. Repulsion and
Attraction. Positives and Negatives. Magnetic
Lines of Force. The Earth as a Magnet. Why
the Compass Points North and South.
Peculiarity of a Magnet. Action of the Electro-
Magnet. Exterior Magnetic Influence Around a
Wires Carrying a Current. Parallel Wires.

IV. Frictional, Voltaic or Galvanic and Page 29
Electro-magnetic Electricity
Three Electrical Sources. Frictional
Electricity. Leyden Jar. Voltaic or Galvanic p. ii

Electricity. Voltaic Pile; How Made. Plus and
Minus Signs. The Common Primary Cell.
Battery Resistance. Electrolyte and Current.
Electro-magnetic Electricity. Magnetic
Radiation. Different Kinds of Dynamos. Direct
Current Dynamos. Simple Magnet
Construction. How to Wind. The Dynamo
Fields. The Armature. Armature Windings.
Mounting the Armature. The Commutator.
Commutator Brushes. Dynamo Windings. The
Field. Series-wound Field. Shunt-wound.
Compound-wound.

V. How to Detect and Measure Page 49
Electricity
Measuring Instruments. The Detector.
Direction of Current. Simple Current Detector.
How to Place the Detector. Different Ways to
Measure a Current. The Sulphuric Acid
Voltameter. The Copper Voltameter. The
Galvanoscope Electro-magnetic Method. The
Calorimeter. The Light Method. The Preferred
Method. How to Make a Sulphuric Acid
Voltameter. How to Make a Copper
Voltameter. Objections to the Calorimeter.

VI. Volts, Amperes, Ohms and Watts Page 60

Understanding Terms. Intensity and Quantity.
Voltage. Amperage Meaning of Watts and
Kilowatt. A Standard of Measurement. The
Ampere Standard. The Voltage Standard. The
Ohm. Calculating the Voltage.

VII. Push Buttons, Switches, Annunciators, Page 65
Bells and Like Apparatus
Simple Switches. A Two-Pole Switch. Double-
Pole Switch. Sliding Switch. Reversing
Switch. Push Buttons. Electric Bells. How p. iii

Made. How Operated. Annunciators. Burglar
Alarm. Wire Circuiting. Circuiting System
with Two Bells and Push Buttons. The Push
Buttons, Annunciators and Bells. Wiring Up a
House.

VIII. Accumulators, Storage or Secondary Page 82
Batteries
Storing Up Electricity. The Accumulator.
Accumulator Plates. The Grid. The Negative
Pole. Connecting Up the Plates. Charging the
Cells. The Initial Charge. The Charging
Current.

IX. The Telegraph Page 90

Mechanism in Telegraph Circuit. The Sending
Key. The Sounder. Connecting Up the Key and
Sounder. Two Stations in Circuit. The Double
Click. Illustrating the Dot and the Dash. The
Morse Telegraph Code. Example in Use.

X. High-tension Apparatus, Condensers, Page 98
Etc.
Induction. Low and High Tension. Elastic
Property of Electricity. The Condenser.
Connecting up a Condenser. The Interrupter.
Uses of High-tension Coils.

XI. Wireless Telegraphy Page 104

Telegraphing Without Wires. Surging
Character of High-tension Currents. The
Coherer. How Made. The Decoherer. The
Sending Apparatus. The Receiving Apparatus.
How the Circuits are Formed.

XII. The Telephone Page 110

Vibrations. The Acoustic Telephone. Sound
Waves. Hearing Electricity. The Diaphragm in p. iv

a Magnetic Field. A Simple Telephone Circuit.
How to Make a Telephone. Telephone
Connections. Complete Installation. The
Microphone. Light Contact Points. How to
Make a Microphone. Microphone, the Father
of the Transmitter. Automatic Cut-outs for
Telephones. Complete Circuiting with
Transmitters.

XIII. Electrolysis, Water Purification, Page 123
Electroplating
Decomposing Liquids. Making Hydrogen and
Oxygen. Purifying Water. Rust. Oxygen as a
Purifier. Composition of Water. Common Air
Not a Good Purifier. Pure Oxygen a Water

Purifier. The Use of Hydrogen in Purification.
Aluminum Electrodes. Electric Hand Purifier.
Purification and Separation of Metals.
Electroplating. Plating Iron with Copper.
Direction of Current.

XIV. Electric Heating. Thermo-Electricity Page 135

Generating Heat in a Wire. Resistance of
Substances. Signs of Connectors. Comparison
of Metals. A Simple Electric Heater. How to
Arrange for Quantity of Current Used. An
Electric Iron. Thermo-Electricity Converting
Heat Directly into Electricity Metals. Electric,
Positive, Negative. Thermo-electric Coupler.

XV. Alternating Currents, Choking Coil, Page 145
Transformer
Direct Current. Alternating Current. The
Magnetic Field. Action of a Magnetized Wire.
The Movement of a Current in a Charged
Wire. Current Reversing Itself. Self-Induction.
Brushes in a Direct Current Dynamo: p. v

Alternating, Positive and Negative Poles. How
an Alternating Current Dynamo is Made. The
Windings. The Armature Wires. Choking
Coils. The Transformer. How the Voltage is
Determined. Voltage and Amperage in
Transformers.

XVI. Electric Lighting Page 161

Early conditions. Fuels. Reversibility of
Dynamo. Electric arc. Mechanism to maintain

the arc. Resistance coil. Parallel carbons for
making arc. Series current. Incandescent
system. Multiple circuit. Subdivision of
electric light. The filament. The glass bulb.
Metallic filaments. Vapor lamps. Directions
for improvements. Heat in electric lighting.
Curious superstitions concerning electricity.
Magnetism. Amber. Discovery of the
properties of a magnet. Electricity in mountain
regions. Early beliefs as to magnetism and
electricity. The lightning rod. Protests against
using it. Pliny's explanation of electricity.

XVII. Power, and Various Other Electrical Page 175
Manifestations
Early beliefs concerning the dynamo.
Experiments with magnets. Physical action of
dynamo and motor. Electrical influence in
windings. Comparing motor and dynamo. How
the current acts in a dynamo. Its force in a
motor. Loss in power transmission. The four
ways in which power is dissipated.
Disadvantages of electric power. Its
advantages. Transmission of energy. High
voltages. The transformer. Step-down
transformers. Electric furnaces. Welding by
electricity. Merging the particles of the joined
ends.
Page 184 p. vi
XVIII. X-Ray, Radium and the Like
The camera and the eye. Actinic rays. Hertzian
waves. High-tension apparatus. Vacuum tubes.

Character of the ultra-violet rays. How
distinguished. The infra-red rays. Their uses.
X-rays not capable of reflection. Not subject
to refraction. Transmission through opaque
substances. Reducing rates of vibration.
Radium. Radio-activity. Radio-active
materials. Pitchblende. A new form of energy.
Electrical source. Healing power. Problems for
scientists.

Glossary of Words Used in the Text Page 189

Index Page 207

p. vii

LIST OF ILLUSTRATIONS

1. Work bench Frontispiece
PAGE

2. Top of magnet-winding reel 14

3. Side of magnet-winding reel 14

4. Journal block 15

5. Plain magnet bar 19

6. Severed magnet 20

7. Reversed magnets 21

8. Horseshoe magnet 22

9. Earth's magnetic lines 23

10. Two permanent magnets 24

11. Magnets in earth's magnetic field 24

12. Armatures for magnets 25

13. Magnetized field 26

14. Magnetized bar 26

15. Direction of current 27

16. Direction of induction current 28

17. Frictional-electricity machine 30

18. Leyden jar 32

19. Galvanic electricity. Crown of cups 33

20. Voltaic electricity 34

21. Primary battery 36

22. Dynamo field and pole piece 39

23. Base and fields assembled 41

24. Details of the armature, core 42

25. Details of the armature, body 42
43 p. viii
26. Armature Journals
27. Commutator 43

28. End view of armature, mounted 44

29. Top view of armature on base 45

30. Field winding 47

31. Series-wound 47

32. Shunt-wound 48

33. Compound-wound 48

34. Compass magnet, swing to the right 50

35. Magnetic compass 50

36. Magnet, swing to the left 50

37. Indicating direction of current 51

38. The bridge of the detector 52

39. Details of detector 53

40. Cross-section of detector 54

41. Acid voltameter 56

42. Copper voltameter 56

43. Two-pole switch 66

44. Double-pole switch 66

45. Sliding switch 67

46. Rheostat form of switch 68

47. Reversing switch 69

48. Push button 70

49. Electric bell 71

50. Armature of electric bell 72

51. Vertical section of annunciator 72

52. Front view of annunciator 72

53. Horizontal section of annunciator 72

54. Front plate of annunciator 72

55. Alarm switch on window 76

56. Burglar alarm on window 76

57. Burglar alarm contact 77

58. Neutral position of contact 78
79 p. ix
59. Circuiting for electric bell
60. Annunciators in circuit 80

61. Wiring system for a house 80

62. Accumulator grids 83

63. Assemblage of accumulator grids 85

64. Connecting up storage battery in series 87

65. Parallel series 88

66. Charging circuit 88

67. Telegraph sending key 91

68. Telegraph sounder 92

69. A telegraph circuit 94

70. Induction coil and circuit 99

71. Illustrating elasticity 100

72. Condenser 101

73. High-tension circuit 102

74. Current interrupter 103

75. Wireless-telegraphy coherer 105

76. Wireless sending-apparatus 107

77. Wireless receiving-apparatus 108

78. Acoustic telephone 111

79. Illustrating vibrations 111

80. The magnetic field 112

81. Section of telephone receiver 114

82. The magnet and receiver head 115

83. Simple telephone connection 116

84. Telephone stations in circuit 117

85. Illustrating light contact points 118

86. The microphone 119

87. The transmitter 119

88. Complete telephone circuit 121

89. Device for making hydrogen and oxygen 124

90. Electric-water purifier 127
129 p. x
91. Portable electric purifier
92. Section of positive plate 130

93. Section of negative plate 130

94. Positive and negative in position 130

95. Form of the insulator 130

96. Simple electric heater 137

97. Side view of resistance device 139

98. Top view of resistance device 139

99. Plan view of electric iron 140

100. Section of electric iron 141

101. Thermo-electric couple 143

102. Cutting a magnetic field 146

103. Alternations, first position 148

104. Alternations, second position 148

105. Alternations, third position 148

106. Alternations, fourth position 148

107. Increasing alternations, first view 149

108. Increasing alternations, second view 149

109. Connection of alternating dynamo 150
armature
110. Direct current dynamo 151

111. Circuit wires in direct current dynamo 152

112. Alternating polarity lines 154

113. Alternating current dynamo 155

114. Choking coil 157

115. A transformer 158

116. Parallel carbons 164

117. Arc-lighting circuit 165

118. Interrupted conductor 166

119. Incandescent circuit 167

120. Magnetic action in dynamo, 1st 177

121. Magnetic action in dynamo, 2d 177

122. Magnetic action in dynamo, 3d 178
178 p. xi
123. Magnetic action in dynamo, 4th
124. Magnetic action in motor, 1st 179

125. Magnetic action in motor, 2d 179

126. Magnetic action in motor, 3d 180

127. Magnetic action in motor, 4th 180

p. 1

INTRODUCTORY
Electricity, like every science, presents two phases to the student, one
belonging to a theoretical knowledge, and the other which pertains to the
practical application of that knowledge. The boy is directly interested in the
practical use which he can make of this wonderful phenomenon in nature.
It is, in reality, the most successful avenue by which he may obtain the
theory, for he learns the abstract more readily from concrete examples.
It is an art in which shop practice is a greater educator than can be possible
with books. Boys are not, generally, inclined to speculate or theorize on
phenomena apart from the work itself; but once put them into contact with
the mechanism itself, let them become a living part of it, and they will
commence to reason and think for themselves.
It would be a dry, dull and uninteresting thing to tell a boy that electricity
can be generated by riveting together two pieces of dissimilar metals,p. 2and
applying heat to the juncture. But put into his hands the metals, and set him
to perform the actual work of riveting the metals together, then wiring up
the ends of the metals, heating them, and, with a galvanometer, watching
for results, it will at once make him see something in the experiment which
never occurred when the abstract theory was propounded.
He will inquire first what metals should be used to get the best results, and
finally, he will speculate as to the reasons for the phenomena. When he
learns that all metals are positive-negative or negative-positive to each
other, he has grasped a new idea in the realm of knowledge, which he
unconsciously traces back still further, only to learn that he has entered a
field which relates to the constitution of matter itself. As he follows the
subject through its various channels he will learn that there is a common
source of all things; a manifestation common to all matter, and that all
substances in nature are linked together in a most wonderful way.
An impulse must be given to a boy's training. The time is past for the rule-
and-rote method. The rule can be learned better by a manual application

than by committing a sentence to memory.
p. 3
In the preparation of this book, therefore, I have made practice and work the
predominating factors. It has been my aim to suggest the best form in which
to do the things in a practical way, and from that work, as the boy carries it
out, to deduce certain laws and develop the principles which underlie them.
Wherever it is deemed possible to do so, it is planned to have the boy make
these discoveries for himself, so as to encourage him to become a thinker
and a reasoner instead of a mere machine.
A boy does not develop into a philosopher or a scientist through being told
he must learn the principles of this teaching, or the fundamentals of that
school of reasoning. He will unconsciously imbibe the spirit and the
willingness if we but place before him the tools by which he may build
even the simple machinery that displays the various electrical
manifestations.

p. 5

CHAPTER I
THE STUDY OF ELECTRICITY. HISTORICAL

There is no study so profound as electricity. It is a marvel to the scientist as
well as to the novice. It is simple in its manifestations, but most complex in
its organization and in its ramifications. It has been shown that light, heat,
magnetism and electricity are the same, but that they differ merely in their
modes of motion.
First Historical Account.—The first historical account of electricity dates
back to 600 years B. C. Thales of Miletus was the first to describe the
properties of amber, which, when rubbed, attracted and repelled light
bodies. The ancients also described what was probably tourmaline, a
mineral which has the same qualities. The torpedo, a fish which has the
power of emitting electric impulses, was known in very early times.
From that period down to about the year 1600 no accounts of any historical
value have been given. Dr. Gilbert, of England, made a number of
researches at that time, principally with amber and other materials, and
Boyle, in 1650, made numerous experiments with frictional electricity.
Sir Isaac Newton also took up the subject at about the same period. In p.1705
6

Hawksbee made numerous experiments; also Gray, in 1720, and a
Welshman, Dufay, at about the same time. The Germans, from 1740 to
1780, made many experiments. In 1740, at Leyden, was discovered the jar
which bears that name. Before that time, all experiments began and ended
with frictional electricity.
The first attempt to "bottle" electricity was attempted by Muschenbrœck, at
Leyden, who conceived the idea that electricity in materials might be
retained by surrounding them with bodies which did not conduct the
current. He electrified some water in a jar, and communication having been
established between the water and the prime conductor, his assistant, who
was holding the bottle, on trying to disengage the communicating wire,
received a sudden shock.

In 1747 Sir William Watson fired gunpowder by an electric spark, and, later
on, a party from the Royal Society, in conjunction with Watson, conducted a
series of experiments to determine the velocity of the electric fluid, as it
was then termed.
Benjamin Franklin, in 1750, showed that lightning was electricity, and later
on made his interesting experiments with the kite and the key.
Discovering Galvanic Electricity.—The great discovery of Galvani, in
p. 7
1790, led to the recognition of a new element in electricity, called galvanic
or voltaic (named after the experimenter, Volta), and now known to be
identical with frictional electricity. In 1805 Poisson was the first to analyze
electricity; and when Œrsted of Copenhagen, in 1820, discovered the
magnetic action of electricity, it offered a great stimulus to the science, and
paved the way for investigation in a new direction. Ampere was the first to
develop the idea that a motor or a dynamo could be made operative by
means of the electro-magnetic current; and Faraday, about 1830, discovered
electro-magnetic rotation.
Electro-magnetic Force.—From this time on the knowledge of electricity
grew with amazing rapidity. Ohm's definition of electro-motive force,
current strength and resistance eventuated into Ohm's law. Thomson greatly
simplified the galvanometer, and Wheatstone invented the rheostat, a means
of measuring resistance, about 1850. Then primary batteries were brought
forward by Daniels, Grove, Bunsen and Thomson, and electrolysis by
Faraday. Then came the instruments of precision—the electrometer, the
resistance bridge, the ammeter, the voltmeter—all of the utmost value in the
science.
Measuring Instruments.—The perfection of measuring instruments did
more to advance electricity than almost any other field of endeavor; sop. 8that
after 1875 the inventors took up the subject, and by their energy developed
and put into practical operation a most wonderful array of mechanism,
which has become valuable in the service of man in almost every field of
human activity.
Rapidity of Modern Progress.—This brief history is given merely to show
what wonders have been accomplished in a few years. The art is really less
than fifty years old, and yet so rapidly has it gone forward that it is not at all

surprising to hear the remark, that the end of the wonders has been reached.
Less than twenty-five years ago a high official of the United States Patent
Office stated that it was probable the end of electrical research had been
reached. The most wonderful developments have been made since that
time; and now, as in the past, one discovery is but the prelude to another
still more remarkable. We are beginning to learn that we are only on the
threshold of that storehouse in which nature has locked her secrets, and that
there is no limit to human ingenuity.
How to Acquire the Vast Knowledge.—As the boy, with his limited
vision, surveys this vast accumulation of tools, instruments and machinery,
p. 9
and sees what has been and is now being accomplished, it is not to be
wondered at that he should enter the field with timidity. In his mind the
great question is, how to acquire the knowledge. There is so much to learn.
How can it be accomplished?
The answer to this is, that the student of to-day has the advantage of the
knowledge of all who have gone before; and now the pertinent thing is to
acquire that knowledge.
The Means Employed.—This brings us definitely down to an examination
of the means that we shall employ to instil this knowledge, so that it may
become a permanent asset to the student's store of information.
The most significant thing in the history of electrical development is the
knowledge that of all the great scientists not one of them ever added any
knowledge to the science on purely speculative reasoning. All of them were
experimenters. They practically applied and developed their theories in the
laboratory or the workshop. The natural inference is, therefore, that the boy
who starts out to acquire a knowledge of electricity, must not only theorize,
but that he shall, primarily, conduct the experiments, and thereby acquire
the information in a practical way, one example of which will make a more
lasting impression than pages of dry text
p. 10
Throughout these pages, therefore, I shall, as briefly as possible, point out
the theories involved, as a foundation for the work, and then illustrate the
structural types or samples; and the work is so arranged that what is done
to-day is merely a prelude or stepping-stone to the next phase of the art. In
reality, we shall travel, to a considerable extent, the course which the great

investigators followed when they were groping for the facts and discovering
the great manifestations in nature.

p. 11

CHAPTER IIToC
WHAT TOOLS AND APPARATUS ARE NEEDED

Preparing the Workshop.—Before commencing actual experiments we
should prepare the workshop and tools. Since we are going into this work as
pioneers, we shall have to be dependent upon our own efforts for the
production of the electrical apparatus, so as to be able, with our home-made
factory, to provide the power, the heat and the electricity. Then, finding we
are successful in these enterprises, we may look forward for "more worlds
to conquer."
By this time our neighbors will become interested in and solicit work from
us.
Uses of Our Workshops.—They may want us to test batteries, and it then
becomes necessary to construct mechanism to detect and measure
electricity; to install new and improved apparatus; and to put in and connect
up electric bells in their houses, as well as burglar alarms. To meet the
requirements, we put in a telegraph line, having learned, as well as we are
able, how they are made and operated. But we find the telegraph too slow
and altogether unsuited for our purposes, as well as for the uses of the
p. 12
neighborhood, so we conclude to put in a telephone system.
What to Build.—It is necessary, therefore, to commence right at the
bottom to build a telephone, a transmitter, a receiver and a switch-board for
our system. From the telephone we soon see the desirability of getting into
touch with the great outside world, and wireless telegraphy absorbs our
time and energies.
But as we learn more and more of the wonderful things electricity will do,
we are brought into contact with problems which directly interest the home.
Sanitation attracts our attention. Why cannot electricity act as an agent to
purify our drinking water, to sterilize sewage and to arrest offensive odors?
We must, therefore, learn something about the subject of electrolysis.

What to Learn.—The decomposition of water is not the only thing that we
shall describe pertaining to this subject. We go a step further, and find that
we can decompose metals as well as liquids, and that we can make a pure
metal out of an impure one, as well as make the foulest water pure. But we
shall also, in the course of our experiments, find that a cheap metal can be
coated with a costly one by means of electricity—that we can electroplate
by electrolysis.
Uses of the Electrical Devices.—While all this is progressing andp. 13our
factory is turning out an amazing variety of useful articles, we are led to
inquire into the uses to which we may devote our surplus electricity. The
current may be diverted for boiling water; for welding metals; for heating
sad-irons, as well as for other purposes which are daily required.
Tools.—To do these things tools are necessary, and for the present they
should not be expensive. A small, rigidly built bench is the first
requirement. This may be made, as shown in Fig. 1, of three 2-inch planks,
each 10 inches wide and 6 feet long, mounted on legs 36 inches in height.
In the front part are three drawers for your material, or the small odds and
ends, as well as for such little tools as you may accumulate. Then you will
need a small vise, say, with a 2-inch jaw, and you will also require a hand
reel for winding magnets. This will be fully described hereafter.
You can also, probably, get a small, cheap anvil, which will be of the
greatest service in your work. It should be mounted close up to the work
bench. Two small hammers, one with an A-shaped peon, and the other with
a round peon, should be selected, and also a plane and a small wood saw
with fine teeth. A bit stock, or a ratchet drill, if you can afford it, with a
p. 14
variety of small drills; two wood chisels, say of ⅜-inch and ¾-inch widths;
small cold chisels; hack saw, 10-inch blade; small iron square; pair of
dividers; tin shears; wire cutters; 2 pairs of pliers, one flat and the other
round-nosed; 2 awls, centering punch, wire cutters, and, finally, soldering
tools.

Fig. 2.

Fig. 3.
Magnet-winding Reel

If a gas stove is not available, a brazing torch is an essential tool. Numerous
small torches are being made, which are cheap and easily operated. A small
soldering iron, with pointed end, should be provided; also metal shears and
a small square; an awl and several sizes of gimlets; a screwdriver; pair of
pliers and wire cutters
From the foregoing it will be seen that the cost of tools is not a p.very
15

expensive item.
This entire outfit, not including the anvil and vise, may be purchased new
for about $20.00, so we have not been extravagant.
Magnet-winding Reel.—Some little preparation must be made, so we may
be enabled to handle our work by the construction of mechanical aids.

Fig. 4. Journal Block.

First of these is the magnet-winding reel, a plan view of which is shown in
Fig. 2. This, for our present work, will be made wholly of wood.

Select a plank 1½ inches thick and 8 inches wide, and from this cut off two
pieces (A), each 7 inches long, and then trim off the corners (B, B), as
shown in Fig. 4. To serve as the mandrel (C, Fig. 2), select a piece of
broomstick 9 inches long. Bore a hole (D) in each block (A) a half inch
below the upper margin of the block, this hole being of such diameter that
the broomstick mandrel will fit and easily turn therein
Place a crank (E), 5 inches long, on the outer end of the mandrel, as inp. Fig.
16

3. Then mount one block on the end of the bench and the other block 3
inches away. Affix them to the bench by nails or screws, preferably the
latter.
On the inner end of the mandrel put a block (F) of hard wood. This is done
by boring a hole 1 inch deep in the center of the block, into which the
mandrel is driven. On the outer face of the block is a square hole large
enough to receive the head of a ⅜-inch bolt, and into the depression thus
formed a screw (G) is driven through the block and into the end of the
mandrel, so as to hold the block (F) and mandrel firmly together. When
these parts are properly put together, the inner side of the block will rest and
turn against the inner journal block (A).
The tailpiece is made of a 2" × 4" scantling (H), 10 inches long, one end of
it being nailed to a transverse block (I) 2" × 2" × 4". The inner face of this
block has a depression in which is placed a V-shaped cup (J), to receive the
end of the magnet core (K) or bolt, which is to be used for this purpose. The
tailpiece (H) has a longitudinal slot (L) 5 inches long adapted to receive a
½-inch bolt (M), which passes down through the bench, and is, therefore,
p. 17
adjustable, so it may be moved to and from the journal bearing (A), thereby
providing a place for the bolts to be put in. These bolts are the magnet cores
(K), 6 inches long, but they may be even longer, if you bore several holes
(N) through the bench so you may set over the tailpiece.
With a single tool made substantially like this, over a thousand of the finest
magnets have been wound. Its value will be appreciated after you have had
the experience of winding a few magnets.
Order in the Workshop.—Select a place for each tool on the rear upright of
the bench, and make it a rule to put each tool back into its place after using.

This, if persisted in, will soon become a habit, and will save you hours of
time. Hunting for tools is the unprofitable part of any work.

p. 18

CHAPTER IIIToC
MAGNETS, COILS, ARMATURES, ETC.

The Two Kinds of Magnet.—Generally speaking, magnets are of two
kinds, namely, permanent and electro-magnetic.
Permanent Magnets.—A permanent magnet is a piece of steel in which an
electric force is exerted at all times. An electro-magnet is a piece of iron
which is magnetized by a winding of wire, and the magnet is energized only
while a current of electricity is passing through the wire.
Electro-Magnet.—The electro-magnet, therefore, is the more useful,
because the pull of the magnet can be controlled by the current which
actuates it.
The electro-magnet is the most essential of all contrivances in the operation
and use of electricity. It is the piece of mechanism which does the physical
work of almost every electrical apparatus or machine. It is the device which
has the power to convert the unseen electric current into motion which may
be observed by the human eye. Without it electricity would be a useless
agent to man.
p. 19
While the electro-magnet is, therefore, the form of device which is almost
wholly used, it is necessary, first, to understand the principles of the
permanent magnet.
Magnetism.—The curious force exerted by a magnet is called magnetism,
but its origin has never been explained. We know its manifestations only,
and laws have been formulated to explain its various phases; how to make it
more or less intense; how to make its pull more effective; the shape and
form of the magnet and the material most useful in its construction.

Fig 5. Plain Magnet Bar

Materials for Magnets.—Iron and steel are the best materials for magnets.
Some metals are non-magnetic, this applying to iron if combined with
manganese. Others, like sulphur, zinc, bismuth, antimony, gold, silver and
copper, not only are non-magnetic, but they are actually repelled by
magnetism. They are called the diamagnetics.
Non-magnetic Materials.—Any non-magnetic body in the path of a
magnetic force does not screen or diminish its action, whereas a magnetic
substance will
In Fig. 5 we show the simplest form of magnet, merely a bar of steelp. 20(A)
with the magnetic lines of force passing from end to end. It will be
understood that these lines extend out on all sides, and not only along two
sides, as shown in the drawing. The object is to explain clearly how the
lines run.

Fig 6. Severed Magnet

Action of a Severed Magnet.—Now, let us suppose that we sever this bar
in the middle, as in Fig. 6, or at any other point between the ends. In this
case each part becomes a perfect magnet, and a new north pole (N) and a
new south pole (S) are made, so that the movement of the magnetic lines of
force are still in the same direction in each—that is, the current flows from
the north pole to the south pole.
What North and South Poles Mean.—If these two parts are placed close
together they will attract each other. But if, on the other hand, one of the
pieces is reversed, as in Fig. 7, they will repel each other. From this comes
the statement that likes repel and unlikes attract each other
p. 21

Repulsion and Attraction.—This physical act of repulsion and attraction is
made use of in motors, as we shall see hereinafter.
It will be well to bear in mind that in treating of electricity the north pole is
always associated with the plus sign (+) and the south pole with the minus
sign (-). Or the N sign is positive and the S sign negative electricity.

Fig. 7. Reversed Magnets

Positives and Negatives.—There is really no difference between positive
and negative electricity, so called, but the foregoing method merely serves
as a means of identifying or classifying the opposite ends of a magnet or of
a wire.
Magnetic Lines of Force.—It will be noticed that the magnetic lines of
force pass through the bar and then go from end to end through the
atmosphere. Air is a poor conductor of electricity, so that if we can find a
shorter way to conduct the current from the north pole to the south pole, the
efficiency of the magnet is increased.
p. 22
This is accomplished by means of the well-known horseshoe magnet, where
the two ends (N, S) are brought close together, as in Fig. 8.
The Earth as a Magnet.—The earth is a huge magnet and the magnetic
lines run from the north pole to the south pole around all sides of the globe.

Fig. 8. Horseshoe Magnet

The north magnetic pole does not coincide with the true north pole or the
pivotal point of the earth's rotation, but it is sufficiently near for all practical

purposes. Fig. 9 shows the magnetic lines running from the north to the
south pole.
Why the Compass Points North and South.—Now, let us try to ascertain
why the compass points north and south.
Let us assume that we have a large magnet (A, Fig. 10), and suspend a
small magnet (B) above it, so that it is within the magnetic field of the large
magnet. This may be done by means of a short pin (C), which is located in
p. 23
the middle of the magnet (B), the upper end of this pin having thereon a
loop to which a thread (D) is attached. The pin also carries thereon a pointer
(E), which is directed toward the north pole of the bar (B).

Fig. 9. Earth's Magnetic Lines

You will now take note of the interior magnetic lines (X), and the exterior
magnetic lines (Z) of the large magnet (A), and compare the direction of
their flow with the similar lines in the small magnet (B).
The small magnet has both its exterior and its interior lines within the
exterior lines (Z) of the large magnet (A), so that as the small magnet (B) is
p. 24
capable of swinging around, the N pole of the bar (B) will point toward the
S pole of the larger bar (A). The small bar, therefore, is influenced by the
exterior magnetic field (Z).

Fig. 10. Two Permanent Magnets

Fig. 11. Magnets in the Earth's Magnetic Field

Let us now take the outline represented by the earth's surface (Fig. 11), and
suspend a magnet (A) at any point, like the needle of a compass, and it will
be seen that the needle will arrange itself north and south, within the
magnetic field which flows from the north to the south pole
p. 25
Peculiarity of a Magnet.—One characteristic of a magnet is that, while
apparently the magnetic field flows out at one end of the magnet, and
moves inwardly at the other end, the power of attraction is just the same at
both ends.
In Fig. 12 are shown a bar (A) and a horseshoe magnet (B). The bar (A) has
metal blocks (C) at each end, and each of these blocks is attracted to and
held in contact with the ends by magnetic influence, just the same as the bar
(D) is attracted by and held against the two ends of the horseshoe magnet.
These blocks (C) or the bar (D) are called armatures. Through them is
represented the visible motion produced by the magnetic field.

Fig. 12. Armatures for Magnets

Action of the Electro-Magnet.—The electro-magnet exerts its force in the
same manner as a permanent magnet, so far as attraction and repulsion are
concerned, and it has a north and a south pole, as in the case with the
p. 26
permanent magnet. An electro-magnet is simply a bar of iron with a coil or
coils of wire around it; when a current of electricity flows through the wire,
the bar is magnetized. The moment the current is cut off, the bar is
demagnetized. The question that now arises is, why an electric current
flowing through a wire, under those conditions, magnetizes the bar, or core,
as it is called.

Fig. 13. Magnetized Field

Fig. 14. Magnetized Bar

In Fig. 13 is shown a piece of wire (A). Let us assume that a current of
electricity is flowing through this wire in the direction of the darts. What
actually takes place is that the electricity extends out beyond the surface of
the wire in the form of the closed rings (B). If, now, this wire (A) is wound
p. 27
around an iron core (C, Fig. 14), you will observe that this electric field, as
it is called, entirely surrounds the core, or rather, that the core is within the
magnetic field or influence of the current flowing through the wire, and the
core (C) thereby becomes magnetized, but it is magnetized only when the
current passes through the wire coil (A).

Fig. 15. Direction of Current

From the foregoing, it will be understood that a wire carrying a current of
electricity not only is affected within its body, but that it also has a sphere of
influence exteriorly to the body of the wire, at all points; and advantage is
taken of this phenomenon in constructing motors, dynamos, electrical
measuring devices and almost every kind of electrical mechanism in
existence.
Exterior Magnetic Influence Around a Wire Carrying a Current.—Bear
in mind that the wire coil (A, Fig. 14) does not come into contact with the
core (C). It is insulated from the core, either by air or by rubber or other
insulating substance, and a current passing from A to C under those
conditions is a current of induction. On the other hand, the current flowing
p. 28
through the wire (A) from end to end is called a conduction current.
Remember these terms.
In this connection there is also another thing which you will do well to bear
in mind. In Fig. 15 you will notice a core (C) and an insulated wire coil (B)
wound around it. The current, through the wire (B), as shown by the darts
(D), moves in one direction, and the induced current in the core (C) travels
in the opposite direction, as shown by the darts (D).

Fig. 16. Direction of Induction Current

Parallel Wires.—In like manner, if two wires (A, B, Fig. 16) are parallel
with each other, and a current of electricity passes along the wire (A) in one
direction, the induced current in the wire (B) will move in the opposite
direction.

These fundamental principles should be thoroughly understood and
mastered.

p. 29

CHAPTER IVToC
FRICTIONAL, VOLTAIC OR GALVANIC, AND ELECTRO-
MAGNETIC ELECTRICITY

Three Electrical Sources.—It has been found that there are three kinds of
electricity, or, to be more accurate, there are three ways to generate it. These
will now be described.
When man first began experimenting, he produced a current by frictional
means, and collected the electricity in a bottle or jar. Electricity, so stored,
could be drawn from the jar, by attaching thereto suitable connection. This
could be effected only in one way, and that was by discharging the entire
accumulation instantaneously. At that time they knew of no means whereby
the current could be made to flow from the jar as from a battery or cell.
Frictional Electricity.—With a view of explaining the principles
involved, we show in Fig. 17 a machine for producing electricity by
friction.

Fig. 17. Friction-Electricity Machine

This is made up as follows: A represents the base, having thereon a flat
member (B), on which is mounted a pair of parallel posts or standards (C,
C), which are connected at the top by a cross piece (D). Between these two
p. 30
posts is a glass disc (E), mounted upon a shaft (F), which passes through the
posts, this shaft having at one end a crank (G). Two leather collecting
surfaces (H, H), which are in contact with the glass disc (E), are held in
position by arms (I, J), the arm (I) being supported by the cross piece (D),
and the arm (J) held by the base piece (B). A rod (K), U-shaped in form,
passes over the structure here thus described, its ends being secured to the
p. 31
base (B). The arms (I, J) are both electrically connected with this rod, or
conductor (K), joined to a main conductor (L), which has a terminating
knob (M). On each side and close to the terminal end of each leather
collector (H) is a fork-shaped collector (N). These two collectors are also
connected electrically with the conductor (K). When the disc is turned
electricity is generated by the leather flaps and accumulated by the
collectors (N), after which it is ready to be discharged at the knob (M).
In order to collect the electricity thus generated a vessel called a Leyden jar
is used.

Leyden Jar.—This is shown in Fig. 18. The jar (A) is of glass coated
exteriorly at its lower end with tinfoil (B), which extends up a little more
than halfway from the bottom. This jar has a wooden cover or top (C),
provided centrally with a hole (D). The jar is designed to receive within it a
tripod and standard (E) of lead. Within this lead standard is fitted a metal
rod (F), which projects upwardly through the hole (D), its upper end having
thereon a terminal knob (G). A sliding cork (H) on the rod (F) serves as a
means to close the jar when not in use. When in use this cork is raised so
the rod may not come into contact, electrically, with the cover (C).
p. 32
The jar is half filled with sulphuric acid (I), after which, in order to charge
the jar, the knob (G) is brought into contact with the knob (M) of the
friction generator (Fig. 17).
Voltaic or Galvanic Electricity.—The second method of generating
electricity is by chemical means, so called, because a liquid is used as one
of the agents.

Fig. 18. Leyden Jar

Galvani, in 1790, made the experiments which led to the generation of
electricity by means of liquids and metals. The first battery was called the
"crown of cups," shown in Fig. 19, and consisting of a row of glass p.cups33

(A), containing salt water. These cups were electrically connected by means
of bent metal strips (B), each strip having at one end a copper plate (C), and

at the other end a zinc plate (D). The first plate in the cup at one end is
connected with the last plate in the cup at the other end by a conductor (E)
to make a complete circuit.

Fig. 19. Galvanic Electricity. Crown of Cups

The Cell and Battery.—From the foregoing it will be seen that within
each cup the current flows from the zinc to the copper plates, and exteriorly
from the copper to the zinc plates through the conductors (B and E).
A few years afterwards Volta devised what is known as the voltaic pile (Fig.
20).
Voltaic Pile—How Made.—This is made of alternate discs of copper and
zinc with a piece of cardboard of corresponding size between each zincp. 34and
copper plate. The cardboard discs are moistened with acidulated water. The
bottom disc of copper has a strip which connects with a cup of acid, and
one wire terminal (A) runs therefrom. The upper disc, which is of zinc, is
also connected, by a strip, with a cup of acid from which extends the other
terminal wire (B).

Fig. 20. Voltaic Electricity

Plus and Minus Signs.—It will be noted that the positive or copper disc has
the plus sign (+) while the zinc disc has the minus (-) sign. These p.signs
35

denote the positive and the negative sides of the current.
The liquid in the cells, or in the moistened paper, is called the electrolyte
and the plates or discs are called electrodes. To define them more clearly,
the positive plate is the anode, and the negative plate the cathode.
The current, upon entering the zinc plate, decomposes the water in the
electrolyte, thereby forming oxygen. The hydrogen in the water, which has
also been formed by the decomposition, is carried to the copper plate, so
that the plate finally is so coated with hydrogen that it is difficult for the
current to pass through. This condition is called "polarization," and to
prevent it has been the aim of all inventors. To it also we may attribute the
great variety of primary batteries, each having some distinctive claim of
merit.
The Common Primary Cell.—The most common form of primary cell
contains sulphuric acid, or a sulphuric acid solution, as the electrolyte, with
zinc for the anode, and carbon, instead of copper, for the cathode.
The ends of the zinc and copper plates are called terminals, and while the
zinc is the anode or positive element, its terminal is designated as the

p. 36
positive pole. In like manner, the carbon is the negative element or cathode,
and its terminal is designated as negative pole.
Fig. 21 will show the relative arrangement of the parts. It is customary to
term that end or element from which the current flows as positive. A cell is
regarded as a whole, and as the current passes out of the cell from the
copper element, the copper terminal becomes positive.

Fig. 21. Primary Battery

Battery Resistance, Electrolyte and Current.—The following should be
carefully memorized:
A cell has reference to a single vessel. When two or more cells are coupled
together they form a battery
p. 37
Resistance is opposition to the movement of the current. If it is offered by
the electrolyte, it is designated "Internal Resistance." If, on the other hand,
the opposition takes place, for instance, through the wire, it is then called
"External Resistance."
The electrolyte must be either acid, or alkaline, or saline, and the electrodes
must be of dissimilar metals, so the electrolyte will attack one of them.
The current is measured in amperes, and the force with which it is caused to
flow is measured in volts. In practice the word "current" is used to designate
ampere flow; and electromotive force, or E. M. F., is used instead of
voltage.

Electro-magnetic Electricity.—The third method of generating electricity
is by electro-magnets. The value and use of induction will now be seen, and
you will be enabled to utilize the lesson concerning magnetic action
referred to in the previous chapter.
Magnetic Radiation.—You will remember that every piece of metal which
is within the path of an electric current has a space all about its surface from
end to end which is electrified. This electrified field extends out a certain
distance from the metal, and is supposed to maintain a movement around it.
If, now, another piece of metal is brought within range of this electric or
p. 38
magnetic zone and moved across it, so as to cut through this field, a current
will be generated thereby, or rather added to the current already exerted, so
that if we start with a feeble current, it can be increased by rapidly "cutting
the lines of force," as it is called.
Different Kinds of Dynamo.—While there are many kinds of dynamo, they
all, without exception, are constructed in accordance with this principle.
There are also many varieties of current. For instance, a dynamo may be
made to produce a high voltage and a low amperage; another with high
amperage and low voltage; another which gives a direct current for lighting,
heating, power, and electroplating; still another which generates an
alternating current for high tension power, or transmission, arc-lighting,
etc., all of which will be explained hereafter.
In this place, however, a full description of a direct-current dynamo will
explain the principle involved in all dynamos—that to generate a current of
electricity makes it necessary for us to move a field of force, like an
armature, rapidly and continuously through another field of force, like a
magnetic field.
Direct-Current Dynamo.—We shall now make the simplest form of
dynamo, using for this purpose a pair of permanent magnets
p. 39

Fig. 22. Dynamo Field and Pole Piece

Simple Magnet Construction.—A simple way to make a pair of magnets
for this purpose is shown in Fig. 22. A piece of round ¾-inch steel core (A),
5½ inches long, is threaded at both ends to receive at one end a nut (B),
which is screwed on a sufficient distance so that the end of the core (A)
projects a half inch beyond the nut. The other end of the steel core has a
pole piece of iron (C) 2" × 2" × 4", with a hole midway between the p.ends,
40

threaded entirely through, and provided along one side with a concave
channel, within which the armature is to turn. Now, before the pole piece
(C) is put on, we will slip on a disc (E), made of hard rubber, then a thin
rubber tube (F), and finally a rubber disc (G), so as to provide a positive
insulation for the wire coil which is wound on the bobbin thus made.
How to Wind.—In practice, and as you go further along in this work, you
will learn the value, first, of winding one layer of insulated wire on the
spool, coating it with shellac, and then putting on the next layer, and so on;
when completely wound, the two wire terminals may be brought out at one
end; but for our present purpose, and to render the explanation clearer, the
wire terminals are at the opposite ends of the spool (H, H').

The Dynamo Fields.—Two of these spools are so made and they are called
the fields of the dynamo.
We will next prepare an iron bar (I), 5 inches long and ½ inch thick and 1½
inches wide, then bore two holes through it so the distance measures 3
inches from center to center. These holes are to be threaded for the ¾-inch
cores (A). This bar holds together the upper ends of the cores, as shown in
Fig. 23
p. 41

Fig. 23. Base and Fields Assembled

We then prepare a base (J) of any hard wood, 2 inches thick, 8 inches long
p. 42
and 8 inches wide, and bore two ¾-inch holes 3 inches apart on a middle
line, to receive a pair of ¾-inch cap screws (K), which pass upwardly
through the holes in the base and screw into the pole pieces (C). A wooden
bar (L), 1½" × 1½", 8 inches long, is placed under each pole piece, which is
also provided with holes for the cap screws (K). The lower side of the base

(J) should be countersunk, as at M, so the head of the nut will not project.
The fields of the dynamo are now secured in position to the base.

Figs. 24-25. Details of the Armature

The Armature.—A bar of iron (Fig. 24), 1" × 1" and 2¼ inches long, is next
provided. Through this bar (1) are then bored two 5/16-inch holes 1¾
inches apart, and on the opposite sides of this bar are two half-rounded
plates of iron (3) (Fig. 25).
Armature Winding.—Each plate is ½ inch thick, 1¾ inches wide and 4
inches long, each plate having holes (4) to coincide with the holes (2) of the
bar (1), so that when the two plates are applied to opposite sides of thep. 43bar,
and riveted together, a cylindrical member is formed, with two channels
running longitudinally, and transversely at the ends; and in these channels
the insulated wires are wound from end to end around the central block (1).
Mounting the Armature.—It is now necessary to provide a means for
revolving this armature. To this end a brass disc (5, Fig. 26) is made, 2
inches in diameter, ⅛ inch thick. Centrally, at one side, is a projecting stem
(6) of round brass, which projects out 2 inches, and the outer end is turned
down, as at 7, to form a small bearing surface.

Figs. 26-27. Armature Mountings

The other end of the armature has a similar disc (8), with a central stem (9),
1½ inches long, turned down to ¼-inch diameter up to within ¼ inch of the
disc (7), so as to form a shoulder
The Commutator.—In Fig. 27 is shown, at 10, a wooden cylinder, 1p.inch 44

long and 1¼ inches in diameter, with a hole (11) bored through axially, so
that it will fit tightly on the stem (6) of the disc (5). On this wooden
cylinder is driven a brass or copper tube (12), which has holes (13) opposite
each other. Screws are used to hold the tube to the wooden cylinder, and
after they are properly secured together, the tube (12) is cut by a saw, as at
14, so as to form two independent tubular surfaces
p. 45

Fig. 28.
End View Armature, Mounted

These tubular sections are called the commutator plates.

Fig. 29.
Top View of Armature on Base

In order to mount this armature, two bearings are provided, each comprising
a bar of brass (15, Fig. 28), each ¼ inch thick, ½ inch wide and 4½ inches
long. Two holes, 3 inches apart, are formed through this bar, to receive
round-headed wood screws (16), these screws being 3 inches long, so they
p. 46
will pass through the wooden pieces (I) and enter the base (J). Midway
between the ends, each bar (15) has an iron bearing block (17), ¾" × ½" and
1½ inches high, the ¼-inch hole for the journal (7) being midway between
its ends.
Commutator Brushes.—Fig. 28 shows the base, armature and commutator
assembled in position, and to these parts have been added the commutator
brushes. The brush holder (18) is a horizontal bar made of hard rubber
loosely mounted upon the journal pin (7), which is 2½ inches long. At each
end is a right-angled metal arm (19) secured to the bar (18) by screws (20).
To these arms the brushes (21) are attached, so that their spring ends engage
with the commutator (12). An adjusting screw (22) in the bearing post (17),
with the head thereof bearing against the brush-holder (18), serves as a
means for revolubly adjusting the brushes with relation to the commutator.
Dynamo Windings.—There are several ways to wind the dynamos. These
can be shown better by the following diagrams (Figs. 30, 31, 32, 33):

The Field.—If the field (A, Fig. 30) is not a permanent magnet, it must be
excited by a cell or battery, and the wires (B, B') are connected up with a
battery, while the wires (C, C') may be connected up to run a motor. This
would, therefore, be what is called a "separately excited" dynamo. Inp. 47this
case the battery excites the field and the armature (D), cutting the lines of
force at the pole pieces (E), so that the armature gathers the current for the
wires (C, C').

Figs. 30-31. Field Winding, Series-wound

Series-wound Field.—Fig. 31 shows a "series-wound" dynamo. The wires
of the fields (A) are connected up in series with the brushes of the armature
(D), and the wires (G, G') are led out and connected up with a lamp, motor
or other mechanism. In this case, as well as in Figs. 32 and 33, both the
field and the armature are made of soft gray iron. With this winding and
means of connecting the wires, the field is constantly excited by the current
passing through the wires.
Shunt-wound Field.—Fig. 32 represents what is known as a "shunt-wound"
p. 48
dynamo. Here the field wires (H, H) connect with the opposite brushes of
the armature, and the wires (I, I') are also connected with the brushes, these
two wires being provided to perform the work required. This is a more
useful form of winding for electroplating purposes.

Figs. 32-33. Shunt-wound, Compound-wound

Compound-wound Field.—Fig. 33 is a diagram of a "compound-wound"
dynamo. The regular field winding (J) has its opposite ends connected
directly with the armature brushes. There is also a winding, of a
comparatively few turns, of a thicker wire, one terminal (K) of which is
connected with one of the brushes and the other terminal (K') forms one
side of the lighting circuit. A wire (L) connects with the other armature
brush to form a complete lighting circuit.

p. 49

CHAPTER VToC
HOW TO DETECT AND MEASURE ELECTRICITY

Measuring Instruments.—The production of an electric current would not
be of much value unless we had some way by which we might detect and
measure it. The pound weight, the foot rule and the quart measure are very
simple devices, but without them very little business could be done. There
must be a standard of measurement in electricity as well as in dealing with
iron or vegetables or fabrics.
As electricity cannot be seen by the human eye, some mechanism must be
made which will reveal its movements.
The Detector.—It has been shown in the preceding chapter that a current
of electricity passing through a wire will cause a current to pass through a
parallel wire, if the two wires are placed close together, but not actually in
contact with each other. An instrument which reveals this condition is called
a galvanometer. It not only detects the presence of a current, but it shows
the direction of its flow. We shall now see how this is done.
For example, the wire (A, Fig. 35) is connected up in an electric circuitp.with
50

a permanent magnet (B) suspended by a fine wire (C), so that the magnet
(B) may freely revolve.

Figs. 34-36.
To the right, Compass Magnet, To the left

For convenience, the magnetic field is shown flowing in the direction of the
darts, in which the dart (D) represents the current within the magnet (B)
flowing toward the north pole, and the darts (E) showing the exterior
current flowing toward the south pole. Now, if the wire (A) is brought up

close to the magnet (B), and a current passed through A, the magnet (B)
will be affected. Fig. 35 shows the normal condition of the magnetized bar
(B) parallel with the wire (A) when a current is not passing through the
latter.
Direction of Current.—If the current should go through the wire (A) from
right to left, as shown in Fig. 34, the magnet (B) would swing in the
p. 51
direction taken by the hands of a clock and assume the position shown in
Fig. 34. If, on the other hand, the current in the wire (A) should be reversed
or flow from left to right, the magnet (B) would swing counter-clock-wise,
and assume the position shown in Fig. 36. The little pointer (G) would, in
either case, point in the direction of the flow of the current through the wire
(A).

Fig. 37. Indicating Direction of Current
p. 52
Simple Current Detector.—A simple current detector may be made as
follows:
Prepare a base 3' × 4' in size and 1 inch thick. At each corner of one end fix
a binding post, as at A, A', Fig. 37. Then select 20 feet of No. 28 cotton-
insulated wire, and make a coil (B) 2 inches in diameter, leaving the ends
free, so they may be affixed to the binding posts (A, A'). Now glue or nail

six blocks (C) to the base, each block being 1" × 1" × 2", and lay the coil on
these blocks. Then drive an L-shaped nail (D) down into each block, on the
inside of the coil, as shown, so as to hold the latter in place.

Fig. 38. The Bridge

Now make a bridge (E, Fig. 38) of a strip of brass ½ inch wide, 1/16 inch
thick and long enough to span the coil, and bend the ends down, as at F, so
as to form legs. A screw hole (G) is formed in each foot, so it may be
screwed to the base.
Midway between the ends this bridge has a transverse slot (H) in one edge,
p. 53
to receive therein the pivot pin of the swinging magnet. In order to hold the
pivot pin in place, cut out an H-shaped piece of sheet brass (I), which, when
laid on the bridge, has its ends bent around the latter, as shown at J, and the
crossbar of the H-shaped piece then will prevent the pivot pin from coming
out of the slot (H).

Fig. 39. Details of Detector

The magnet is made of a bar of steel (K, Fig. 39) 1½ inches long, ⅜ inch
wide and 1/16 inch thick, a piece of a clock spring being very serviceable
for this purpose. The pivot pin is made of an ordinary pin (L), and as it is
difficult to solder the steel magnet (K) to the pin, solder only a small disc
(M) to the pin (L). Then bore a hole (N) through the middle of the magnet
(K), larger in diameter than the pin (L), and, after putting the pin in the
hole, pour sealing wax into the hole, and thereby secure the two parts
together. Near the upper end of the pin (L) solder the end of a pointer (O),
p. 54
this pointer being at right angles to the armature (K). It is better to have a
metal socket for the lower end of the pin. When these parts are put together,
as shown in Fig. 37, a removable glass top, or cover, should be provided.

This is shown in Fig. 40, in which a square, wooden frame (P) is used, and
a glass (Q) fitted into the frame, the glass being so arranged that when the
cover is in position it will be in close proximity to the upper projecting end
of the pivot pin (L), and thus prevent the magnet from becoming misplaced.

Fig. 40. Cross Section of Detector

How to Place the Detector.—If the detector is placed north and south, as
shown by the two markings, N and S (Fig. 37), the magnet bar will point
north and south, being affected by the earth's magnetism; but when a
current of electricity flows through the coil (B), the magnet will be
deflected to the right or to the left, so that the pointer (O) will then show the
p. 55
direction in which the current is flowing through the wire (R) which you are
testing.
The next step of importance is to measure the current, that is, to determine
its strength or intensity, as well as the flow or quantity.
Different Ways of Measuring a Current.—There are several ways to
measure the properties of a current, which may be defined as follows:
1. The Sulphuric Acid Voltameter.—By means of an electrolytic action,
whereby the current decomposes an acidulated solution—that is, water
which has in it a small amount of sulphuric acid—and then measuring the
gas generated by the current.
2. The Copper Voltameter.—By electro-chemical means, in which the
current passes through plates immersed in a solution of copper sulphate.
3. The Galvanoscope.—By having a coil of insulated wire, with a magnet
suspended so as to turn freely within the coil, forming what is called a
galvanoscope.
4. Electro-magnetic Method.—By using a pair of magnets and sending a
current through the coils, and then measuring the pull on the armature.

5. The Power or Speed Method.—By using an electric fan, and noting the
revolutions produced by the current
p. 56
6. The Calorimeter.—By using a coil of bare wire, immersed in paraffine
oil, and then measuring the temperature by means of a thermometer.

Fig. 41. Fig. 42.
Acid Voltameter Copper Voltameter

7. The Light Method.—Lastly, by means of an electric light, which shows,
by its brightness, a greater or less current.
The Preferred Methods.—It has been found that the first and second
p. 57
methods are the only ones which will accurately register current strength,
and these methods have this advantage—that the chemical effect produced
is not dependent upon the size or shape of the apparatus or the plates used.
How to Make a Sulphuric Acid Voltameter.—In Fig. 41 is shown a simple
form of sulphuric acid voltameter, to illustrate the first method. A is a jar,
tightly closed by a cover (B). Within is a pair of platinum plates (C, C),
each having a wire (D) through the cover. The cover has a vertical glass
tube (E) through it, which extends down to the bottom of the jar, the
electrolyte therein being a weak solution of sulphuric acid. When a current

passes through the wires (D), the solution is partially decomposed—that is,
converted into gas, which passes up into the vacant space (F) above the
liquid, and, as it cannot escape, it presses the liquid downwardly, and causes
the latter to flow upwardly into the tube (E). It is then an easy matter, after
the current is on for a certain time, to determine its strength by the height of
the liquid in the tube.
How to Make a Copper Voltameter.—The second, or copper voltameter, is
shown in Fig. 42. The glass jar (A) contains a solution of copper sulphate,
known in commerce as blue vitriol. A pair of copper plates (B, B')p. 58are
placed in this solution, each being provided with a connecting wire (C).
When a current passes through the wires (C), one copper plate (B) is eaten
away and deposited on the other plate (B'). It is then an easy matter to take
out the plates and find out how much in weight B' has gained, or how much
B has lost.
In this way, in comparing the strength of, say, two separate currents, one
should have each current pass through the voltameter the same length of
time as the other, so as to obtain comparative results.
It is not necessary, in the first and second methods, to consider the shapes,
the sizes of the plates or the distances between them. In the first method the
gas produced, within a given time, will be the same, and in the second
method the amount deposited or eaten away will be the same under all
conditions.
Disadvantages of the Galvanoscope.—With the third method (using the
galvanoscope) it is necessary, in order to get a positively correct reading
instrument, to follow an absolutely accurate plan in constructing each part,
in every detail, and great care must be exercised, particularly in winding. It
p. 59
is necessary also to be very careful in selecting the sizes of wire used and in
the number of turns made in the coils.
This is equally true of the fourth method, using the electro-magnet, because
the magnetic pull is dependent upon the size of wire from which the coils
are made and the number of turns of wire.
Objections to the Calorimeter.—The calorimeter, or sixth method, has the
same objection. The galvanoscope and electro-magnet do not respond

equally to all currents, and this is also true, even to a greater extent, with the
calorimeter.

p. 60

CHAPTER VIToC
VOLTS, AMPERES, OHMS AND WATTS

Understanding Terms.—We must now try to ascertain the meaning of some
of the terms so frequently used in connection with electricity. If you
intended to sell or measure produce or goods of any kind, it would be
essential to know how many pints or quarts are contained in a gallon, or in a
bushel, or how many inches there are in a yard, and you also ought to know
just what the quantity term bushel or the measurement yard means.
Intensity and Quantity.—Electricity, while it has no weight, is capable of
being measured by means of its intensity, or by its quantity. Light may be
measured or tested by its brilliancy. If one light is of less intensity than
another and both of them receive their impulses from the same source, there
must be something which interferes with that light which shows the least
brilliancy. Electricity can also be interfered with, and this interference is
called resistance.
Voltage.—Water may be made to flow with greater or less force, or
p. 61
velocity, through a pipe, the degree of same depending upon the height of
the water which supplies the pipe. So with electricity. It may pass over a
wire with greater or less force under one condition than another. This force
is called voltage. If we have a large pipe, a much greater quantity of water
will flow through it than will pass through a small pipe, providing the
pressure in each case is alike. This quantity in electricity is called
amperage.
In the case of water, a column 1" × 1", 28 inches in height, weighs 1 pound;
so that if a pipe 1 inch square draws water from the bottom it flows with a
pressure of 1 pound. If the pipe has a measurement of 2 square inches,
double the quantity of water will flow therefrom, at the same pressure.
Amperage.—If, on the other hand, we have a pipe 1 inch square, and there
is a depth of 56 inches of water in the reservoir, we shall get as much water

from the reservoir as though we had a pipe of 2 square inches drawing
water from a reservoir which is 28 inches deep.
Meaning of Watts.—It is obvious, therefore, that if we multiply the height
of the water in inches with the area of the pipe, we shall obtain a factor
which will show how much water is flowing.
Here are two examples:
p. 62
1. 28 inches = height of the water in the reservoir.
2 square inches = size of the pipe.
Multiply 28 × 2 = 56.
2. 56 = height of the water in the reservoir.
1 square inch = size of the pipe.
Multiply 56 × 1 = 56.
Thus the two problems are equal.
A Kilowatt.—Now, in electricity, remembering that the height of the water
corresponds with voltage in electricity, and the size of the pipe with
amperage, if we multiply volts by amperes, or amperes by volts, we get a
result which is indicated by the term watts. One thousand of these watts
make a kilowatt, and the latter is the standard of measurement by which a
dynamo or motor is judged or rated.
Thus, if we have 5 amperes and 110 volts, the result of multiplying them
would be 550 watts, or 5 volts and 110 amperes would produce 550 watts.
A Standard of Measurement.—But with all this we must have some
standard. A bushel measure is of a certain size, and a foot has a definite
length, so in electricity there is a recognized force and quantity which are
determined as follows:
The Ampere Standard.—It is necessary, first, to determine what an ampere
p. 63
is. For this purpose a standard solution of nitrate of silver is used, and a
current of electricity is passed through this solution. In doing so the current
deposits silver at the rate of 0.001118 grains per second for each ampere.
The Voltage Standard.—In order to determine the voltage we must know
something of resistance. Different metals do not transmit a current with

equal ease. The size of a conductor, also, is an important factor in the
passage of a current. A large conductor will transmit a current much better
than a small conductor. We must therefore have a standard for the ohm,
which is the measure of resistance.
The Ohm.—It is calculated in this way: There are several standards, but the
one most generally employed is the International Ohm. To determine it, by
this system, a column of pure mercury, 106.3 millimeters long and
weighing 14.4521 grams, is used. This would make a square tube about 94
inches long, and a little over 1/25 of an inch in diameter. The resistance to a
current flow in such a column would be equal to 1 ohm.
Calculating the Voltage.—In order to arrive at the voltage we must use a
conductor, which, with a resistance of 1 ohm, will produce 1 ampere. It
must be remembered that the volt is the practical unit of electro-motive
force
p. 64
While it would be difficult for the boy to conduct these experiments in the
absence of suitable apparatus, still, it is well to understand thoroughly how
and why these standards are made and used.

p. 65

CHAPTER VIIToC
PUSH BUTTONS, SWITCHES, ANNUNCIATORS, BELLS
AND LIKE APPARATUS

Simple Switches.—We have now gone over the simpler or elementary
outlines of electrical phenomena, and we may commence to do some of the
practical work in the art. We need certain apparatus to make connections,
which will be constructed first.
A Two-Pole Switch.—A simple two-pole switch for a single line is made as
follows:
A base block (A, Fig. 43) 3 inches long, 2 inches wide and ¾ inch thick, has
on it, at one end, a binding screw (B), which holds a pair of fingers (C) of
brass or copper, these fingers being bent upwardly and so arranged as to
serve as fingers to hold a switch bar (D) between them. This bar is also of
copper or brass and is pivoted to the fingers. Near the other end of the base
is a similar binding screw (E) and fingers (F) to receive the blade of the
switch bar. The bar has a handle (G) of wood. The wires are attached to the
respective binding screws (B, E).
Double-Pole Switch.—A double-pole switch or a switch for a double line
p. 66
is shown in Fig. 44. This is made similar in all respects to the one shown in
Fig. 43, excepting that there are two switch blades (A, A) connected by a
cross bar (B) of insulating material, and this bar carries the handle (C).

Fig. 43. Two-Pole Switch

Fig. 44. Double-Pole Switch

Other types of switch will be found very useful. In Fig. 45 is a simple
sliding switch in which the base block has, at one end, a pair of copper
plates (A, B), each held at one end to the base by a binding screw (C), and
p. 67
having a bearing or contact surface (D) at its other end. At the other end of
the base is a copper plate (E) held by a binding screw (F), to the inner end
of which plate is hinged a swinging switch blade (G), the free end of which
is adapted to engage with the plates (A, B).

Fig. 45. Sliding Switch

Sliding Switch.—This sliding switch form may have the contact plates (A,
B and C, Fig. 46) circularly arranged and any number may be located on the
base, so they may be engaged by a single switching lever (H). It is the form
usually adopted for rheostats.
Reversing Switch.—A reversing switch is shown in Fig. 47. The base has
two plates (A, B) at one end, to which the parallel switch bars (C, D) are
hinged. The other end of the base has three contact plates (E, F, G) to
engage the swinging switch bars, these latter being at such distance p.apart
68

that they will engage with the middle and one of the outer plates. The inlet
wires, positive and negative, are attached to the plates (A, B, respectively),
and one of the outlet wires (H) is attached to the middle contact plate (F),
while the other wire is connected up with both of the outside plates. When
the switch bars (C, D) are thrown to the left so as to be in contact with E, F,
the outside plate (E) and the middle plate (F) will be positive and negative,
respectively; but when the switch is thrown to the right, as shown in the
figure, plate F becomes positive and plate E negative, as shown.

Fig. 46. Rheostat Form of Switch

Push Buttons.—A push button is but a modified structure of a switch, and
they are serviceable because they are operating, or the circuit is formedp.only
69

while the finger is on the button.

Fig. 47. Reversing Switch

In its simplest form (Fig. 48) the push button has merely a circular base (A)
of insulating material, and near one margin, on the flat side, is a rectangular
plate (B), intended to serve as a contact plate as well as a means for
attaching one of the wires thereto. In line with this plate is a spring finger
(C), bent upwardly so that it is normally out of contact with the plate (B), its
end being held by a binding screw (D). To effect contact, the spring end of
the finger (C) is pressed against the bar (B), as at E. This is enclosed in a
suitable casing, such as will readily suggest itself to the novice.
Electric Bell.—One of the first things the boy wants to make, andp. 70one
which is also an interesting piece of work, is an electric bell.
To make this he will be brought, experimentally, in touch with several
important features in electrical work. He must make a battery for the
production of current, a pair of electro-magnets to be acted upon by the
current, a switch to control it, and, finally, he must learn how to connect it
up so that it may be operated not only from one, but from two or more push
buttons.

Fig. 48. Push Button

How Made.—In Fig. 49 is shown an electric bell, as usually constructed, so
modified as to show the structure at a glance, with its connections. A is the
base, B, B' the binding posts for the wires, C, C the electro-magnets, C' the
bracket for holding the magnets, D the armature, E the thin spring which
connects the armature with the post F, G the clapper arm, H the bell, I the
p. 71
adjusting screw on the post J, K the wire lead from the binding post B to the
first magnet, L the wire which connects the two magnets, M the wire which
runs from the second magnet to the post J, and N a wire leading from the
armature post to the binding post B'.

Fig. 49. Electric Bell

The principle of the electric bell is this: In looking at Fig. 49, you will note
p. 72
that the armature bar D is held against the end of the adjusting screw by the
small spring E. When a current is turned on, it passes through the
connections and conduits as follows: Wire K to the magnets, wire M to the
binding post J, and set screw I, then through the armature to the post F, and
from post F to the binding post B'.

Fig. 50. Armature of Electric Bell

Electric Bell—How Operated.—The moment a current passes through the
magnets (C, C), the core is magnetized, and the result is that the armature
(D) is attracted to the magnets, as shown by the dotted lines (O), when the
clapper strikes the bell. But when the armature moves over to the magnet,
the connection is broken between the screw (I) and armature (D), so that the
cores of the magnets are demagnetized and lose their pull, and the spring
p. 73
(E) succeeds in drawing back the armature. This operation of vibrating the
armature is repeated with great rapidity, alternately breaking and re-
establishing the circuit, by the action of the current.
In making the bell, you must observe one thing, the binding posts (B, B')
must be insulated from each other, and the post J, or the post F, should also
be insulated from the base. For convenience we show the post F insulated,
so as to necessitate the use of wire (N) from post (F) to binding post (B').
The foregoing assumes that you have used a cast metal base, as most bells
are now made; but if you use a wooden base, the binding posts (B, B') and
the posts (F, J) are insulated from each other, and the construction is much
simplified.
It is better, in practice, to have a small spring (P, Fig. 50) between the
armature (D) and the end of the adjusting screw (I), so as to give a return
impetus to the clapper. The object of the adjusting screw is to push and hold
the armature close up to the ends of the magnets, if it seems necessary.
If two bells are placed on the base with the clapper mounted between them,
both bells will be struck by the swinging motion of the armature.

An easily removable cap or cover is usually placed over the coilsp. 74and
armature, to keep out dust.
A very simple annunciator may be attached to the bell, as shown in the
following figures:

Figs. 51-54. Annunciator

Annunciators.—Make a box of wood, with a base (A) 4" × 5" and ½ inch
thick. On this you can permanently mount the two side pieces (B) and two
top and bottom pieces (C), respectively, so they project outwardlyp. 754½
inches from the base. On the open front place a wood or metal plate (D),
provided with a square opening (D), as in Fig. 54, near its lower end. This
plate is held to the box by screws (E).
Within is a magnet (F), screwed into the base (A), as shown in Fig. 51; and
pivoted to the bottom of the box is a vertical armature (G), which extends
upwardly and contacts with the core of the magnet. The upper end of the
armature has a shoulder (H), which is in such position that it serves as a rest
for a V-shaped stirrup (I), which is hinged at J to the base (C). This stirrup
carries the number plate (K), and when it is raised to its highest point it is
held on the shoulder (H), unless the electro-magnet draws the armature out
of range of the stirrup. A spring (L) bearing against the inner side of the

armature keeps its upper end normally away from the magnet core. When
the magnet draws the armature inwardly, the number plate drops and
exposes the numeral through the opening in the front of the box. In order to
return the number plate to its original position, as shown in Fig. 51, a
vertical trigger (M) passes up through the bottom, its upper end being
within range of one of the limbs of the stirrup.
p. 76
This is easily made by the ingenious boy, and will be quite an acquisition to
his stock of instruments. In practice, the annunciator may be located in any
convenient place and wires run to that point.

Fig. 55. Alarm Switch on Window

Fig. 56. Burglar Alarm Attachment to Window

Burglar Alarm.—In order to make a burglar alarm connection with a bell,
p. 77
push buttons or switches may be put in circuit to connect with the windows
and doors, and by means of the annunciators you may locate the door or
window which has been opened. The simplest form of switch for a window
is shown in the following figures:
The base piece (A), which may be of hard rubber or fiber, is ¼ inch thick
and 1" × 1½" in size.

Fig. 57. Burglar Alarm Contact

At one end is a brass plate (B), with a hole for a wood screw (C), this screw
being designed to pass through the plate and also into the window-frame, so
as to serve as a means of attaching one of the wires thereto. The inner end
of the plate has a hole for a round-headed screw (C') that also goes through
the base and into the window-frame. It also passes through the lower end of
the heart-shaped metal switch-piece (D)
The upper end of the base has a brass plate (E), also secured to the basep. 78and
window by a screw (F) at its upper end. The heart-shaped switch is of such
length and width at its upper end that when it is swung to the right with one
of the lobes projecting past the edge of the window-frame, the other lobe
will be out of contact with the plate (E).

Fig. 58. Neutral Position of Contact

The window sash (G) has a removable pin (H), which, when the sash moves
upwardly, is in the path of the lobe of the heart-shaped switch, as shown in
Fig. 56, and in this manner the pin (H) moves the upper end of the switch
(D) inwardly, so that the other lobe contacts with the plate (E), and
establishes an electric circuit, as shown in Fig. 57. During the daytime the

p. 79
pin (H) may be removed, and in order to protect the switch the heart-shaped
piece (D) is swung inwardly, as shown in Fig. 58, so that neither of the
lobes is in contact with the plate (E).
Wire Circuiting.—For the purpose of understanding fully the circuiting,
diagrams will be shown of the simple electric bell with two push buttons;
next in order, the circuiting with an annunciator and then the circuiting
necessary for a series of windows and doors, with annunciator attachments.

Fig. 59. Circuiting for Electric Bell

Circuiting System with a Bell and Two Push Buttons.—Fig. 59 shows a
simple circuiting system which has two push buttons, although any number
may be used, so that the bell will ring when the circuit is closed by either
button.
The Push Buttons and the Annunciator Bells.—Fig. 60 shows three push
buttons and an annunciator for each button. These three circuitsp. 80are
indicated by A, B and C, so that when either button makes contact, a
complete circuit is formed through the corresponding annunciator.

Fig. 60. Annunciators

Fig. 61. Wiring System for a House

Wiring Up a House.—The system of wiring up a house so that all doors and
windows will be connected to form a burglar alarm outfit, is shown in Fig.
61. It will be understood that, in practice, the bell is mounted on or at the
p. 81
annunciator, and that, for convenience, the annunciator box has also a
receptacle for the battery. The circuiting is shown diagramatically, as it is
called, so as fully to explain how the lines are run. Two windows and a door
are connected up with an annunciator having three drops, or numbers 1, 2,
3. The circuit runs from one pole of the battery to the bell and then to one
post of the annunciator. From the other post a wire runs to one terminal of
the switch at the door or window. The other switch terminal has a wire
running to the other pole of the battery.
A, B, C represent the circuit wires from the terminals of the window and
door switches, to the annunciators.
It is entirely immaterial which side of the battery is connected up with the
bell.
From the foregoing it will readily be understood how to connect up any
ordinary apparatus, remembering that in all cases the magnet must be
brought into the electric circuit.

p. 82

CHAPTER VIIIToC
ACCUMULATORS. STORAGE OR SECONDARY
BATTERIES

Storing Up Electricity.—In the foregoing chapters we have seen that,
originally, electricity was confined in a bottle, called the Leyden jar, from
which it was wholly discharged at a single impulse, as soon as it was
connected up by external means. Later the primary battery and the dynamo
were invented to generate a constant current, and after these came the
second form of storing electricity, called the storage or secondary battery,
and later still recognized as accumulators.
The Accumulator.—The term accumulator is, strictly speaking, the more
nearly correct, as electricity is, in reality, "stored" in an accumulator. But
when an accumulator is charged by a current of electricity, a chemical
change is gradually produced in the active element of which the
accumulator is made. This change or decomposition continues so long as
the charging current is on. When the accumulator is disconnected from the
charging battery or dynamo, and its terminals are connected up with a
p. 83
lighting system, or with a motor, for instance, a reverse process is set up, or
the particles re-form themselves into their original compositions, which
causes a current to flow in a direction opposite to that of the charging
current.
It is immaterial to the purposes of this chapter, as to the charging source,
whether it be by batteries or dynamos; the same principles will apply in
either case.

Fig. 62. Accumulator Grids

Accumulator Plates.—The elements used for accumulator plates are red
lead for the positive plates, and precipitated lead, or the well-known
litharge, for the negative plates. Experience has shown that the best way to
hold this material is by means of lead grids
Fig. 62 shows the typical form of one of these grids. It is made of lead,p. 84
cast
or molded in one piece, usually square, as at A, with a wing or projection
(B), at one margin, extending upwardly and provided with a hole (C). The
grid is about a quarter of an inch thick.
The Grid.—The open space, called the grid, proper, comprises cross bars,
integral with the plate, made in a variety of shapes. Fig. 62 shows three
forms of constructing these bars or ribs, the object being to provide a form
which will hold in the lead paste, which is pressed in so as to make a solid-
looking plate when completed.
The Positive Plate.—The positive plate is made in the following manner:
Make a stiff paste of red lead and sulphuric acid; using a solution, say, of
one part of acid to two parts of water. The grid is laid on a flat surface and
the paste forced into the perforations with a stiff knife or spatula. Turn over
the grid so as to get the paste in evenly on both sides.
The grid is then stood on its edge, from 18 to 20 hours, to dry, and
afterwards immersed in a concentrated solution of chloride of lime, so as to
convert it into lead peroxide. When the action is complete it is thoroughly
rinsed in cold water, and is ready to use.

The Negative Plate.—The negative plate is filled, in like manner, p.with 85

precipitated lead. This lead is made by putting a strip of zinc into a standard
solution of acetate of lead, and crystals will then form on the zinc. These
will be very thin, and will adhere together, firmly, forming a porous mass.
This, when saturated and kept under water for a short time, may be put into
the openings of the negative plate.

Fig. 63. Assemblage of Accumulator Plates

Connecting Up the Plates.—The next step is to put these plates in position
to form a battery. In Fig. 63 is shown a collection of plates connected
together
For simplicity in illustrating, the cell is made up of glass, porcelain, orp.hard
86

rubber, with five plates (A), A, A representing the negative and B, B the
positive plates. A base of grooved strips (C, C) is placed in the batteries of
the cell to receive the lower ends of the plates. The positive plates are held
apart by means of a short section of tubing (D), which is clamped and held
within the plates by a bolt (E), this bolt also being designed to hold the
terminal strip (F).
In like manner, the negative plates are held apart by the two tubular sections
(G), each of which is of the same length as the section D of the positives.
The bolt (H) holds the negatives together as well as the terminal (I). The
terminals should be lead strips, and it would be well, owing to the acid

fumes which are formed, to coat all brass work, screws, etc., with paraffine
wax.
The electrolyte or acid used in the cell, for working purposes, is a pure
sulphuric acid, which should be diluted with about four times its weight in
water. Remember, you should always add the strong acid to the water, and
never pour the water into the acid, as the latter method causes a dangerous
ebullition, and does not produce a good mixture
Put enough of this solution into the cell to cover the tops of the plates,p. 87and
the cell is ready.

Fig. 64. Connecting Up Storage Battery in Series

Charging the Cells.—The charge of the current must never be less than 2.5
volts. Each cell has an output, in voltage, of about 2 volts, hence if we have,
say, 10 cells, we must have at least 25 volts charging capacity. We may
arrange these in one line, or in series, as it is called, so far as the
connections are concerned, and charge them with a dynamo, or other
electrical source, which shows a pressure of 25 volts, as illustrated in Fig.
64, or, instead of this, we may put them into two parallel sets of 5 cells
each, as shown in Fig. 65, and use 12.5 volts to charge with. In this case it
will take double the time because we are charging with only one-half the
voltage used in the first case.
The positive pole of the dynamo should be connected with the positive pole
of the accumulator cell, and negative with negative. When this has p.been 88

done run up the machine until it slightly exceeds the voltage of the cells.
Thus, if we have 50 cells in parallel, like in Fig. 64, at least 125 volts will
be required, and the excess necessary should bring up the voltage in the
dynamo to 135 or 140 volts.

Fig. 65. Parallel Series

Fig. 66. Charging Circuit

The Initial Charge.—It is usual initially to charge the battery from periods
ranging from 36 to 40 hours, and to let it stand for 12 or 15 hours, after
which to re-charge, until the positive plates have turned to a chocolate
color, and the negative plates to a slate or gray color, and both platesp.give
89

off large bubbles of gas.
In charging, the temperature of the electrolyte should not exceed 100°
Fahrenheit.
When using the accumulators they should never be fully discharged.
The Charging Circuit.—The diagram (Fig. 66) shows how a charging
circuit is formed. The lamps are connected up in parallel, as illustrated.
Each 16-candle-power 105-volt lamp will carry ½ ampere, so that,
supposing we have a dynamo which gives 110 volts, and we want to charge
a 4-volt accumulator, there will be 5-volt surplus to go to the accumulator.
If, for instance, you want the cell to have a charge of 2 amperes, four of
these lamps should be connected up in parallel. If 3 amperes are required,
use 6 lamps, and so on.

p. 90

CHAPTER IXToC
THE TELEGRAPH

The telegraph is a very simple instrument. The key is nothing more or less
than a switch which turns the current on and off alternately.
The signals sent over the wires are simply the audible sounds made by the
armature, as it moves to and from the magnets.
Mechanism in Telegraph Circuits.—A telegraph circuit requires three
pieces of mechanism at each station, namely, a key used by the sender, a
sounder for the receiver, and a battery.
The Sending Key.—The base of the sending instrument is six inches long,
four inches wide, and three-quarters of an inch thick, made of wood, or any
suitable non-conducting material. The key (A) is a piece of brass three-
eighths by one-half inch in thickness and six inches long. Midway between
its ends is a cross hole, to receive the pivot pin (B), which also passes
through a pair of metal brackets (C, D), the bracket C having a screw to
hold one of the line wires, and the other bracket having a metal switch (E)
p. 91
hinged thereto. This switch bar, like the brackets, is made of brass, one-half
inch wide by one-sixteenth of an inch thick.
Below the forward end of the key (A) is a cross bar of brass (F), screwed to
the base by a screw at one end, to receive the other line wire. Directly
below the key (A) is a screw (G), so that the key will strike it when moved
downwardly. The other end of the bar (F) contacts with the forward end of
the switch bar (E) when the latter is moved inwardly.

Fig. 67. Telegraph Sending Key

The forward end of the key (A) has a knob (H) for the fingers, and the rear
end has an elastic (I) attached thereto which is secured to the end of the
base, so that, normally, the rear end is held against the base and away from
the screw head (G). The head (J) of a screw projects from the base at its rear
end. Key A contacts with it.
When the key A contacts with the screw heads G, J, a click is produced,p. 92one
when the key is pressed down and the other when the key is released.
You will notice that the two plates C, F are connected up in circuit with the
battery, so that, as the switch E is thrown, so as to be out of contact, the
circuit is open, and may be closed either by the key A or the switch E. The
use of the switch will be illustrated in connection with the sounder.

Fig. 68. Telegraph Sounder

When the key A is depressed, the circuit of course goes through plate C, key
A and plate F to the station signalled.
The Sounder.—The sounder is the instrument which carries the electro-
magnet.
In Fig. 68 this is shown in perspective. The base is six inches long and four
p. 93
inches wide, being made, preferably, of wood. Near the forward end is
mounted a pair of electro-magnets (A, A), with their terminal wires
connected up with plates B, B', to which the line wires are attached.
Midway between the magnets and the rear end of the base is a pair of
upwardly projecting brackets (C). Between these are pivoted a bar (D), the
forward end of which rests between the magnets and carries, thereon, a

cross bar (E) which is directly above the magnets, and serves as the
armature.
The rear end of the base has a screw (F) directly beneath the bar D of such
height that when the rear end of the bar D is in contact therewith the
armature E will be out of contact with the magnet cores (A, A). A spiral
spring (G) secured to the rear ends of the arm and to the base, respectively,
serves to keep the rear end of the key normally in contact with the screw F.
Connecting Up the Key and Sounder.—Having made these two
instruments, we must next connect them up in the circuit, or circuits,
formed for them, as there must be a battery, a key, and a sounder at each
end of the line.
In Fig. 69 you will note two groups of those instruments. Now observe how
the wires connect them together. There are two line wires, one (A) which
connects up the two batteries, the wire being attached so that onep. 94end
connects with the positive terminal of the battery, and the other end with the
negative terminal.

Fig. 69. A Telegraph Circuit

The other line wire (B), between the two stations, has its opposite ends
connected with the terminals of the electro-magnet C of the sounders. The
other terminals of each electro-magnet are connected up with one terminal
of each key by a wire (D), and to complete the circuit at each station, the
other terminal of the key has a wire (E) to its own battery.
Two Stations in Circuit.—The illustration shows station 2 telegraphing to
station 1. This is indicated by the fact that the switch F' of that instrument is
open, and the switch F of station 1 closed. When, therefore, the key of
station 2 is depressed, a complete circuit is formed which transmitsp. 95the

current through wire E' and battery, through line A, then through the battery
of station 1, through wire E to the key, and from the key, through wire D, to
the sounder, and finally from the sounder over line wire B back to the
sounder of station 2, completing the circuit at the key through wire D'.
When the operator at station 2 closes the switch F', and the operator at
station 1 opens the switch F, the reverse operation takes place. In both
cases, however, the sounder is in at both ends of the line, and only the
circuit through the key is cut out by the switch F, or F'.
The Double Click.—The importance of the double click of the sounder will
be understood when it is realized that the receiving operator must have
some means of determining if the sounder has transmitted a dot or a dash.
Whether he depresses the key for a dot or a dash, there must be one click
when the key is pressed down on the screw head G (Fig. 62), and also
another click, of a different kind, when the key is raised up so that its rear
end strikes the screw head J. This action of the key is instantly duplicated
by the bar D (Fig. 68) of the sounder, so that the sounder as well as the
receiver knows the time between the first and the second click, and by that
means he learns that a dot or a dash is made
p. 96
Illustrating the Dot and the Dash.—To illustrate: Let us suppose, for
convenience, that the downward movement of the lever in the key, and the
bar in the sounder, make a sharp click, and the return of the lever and bar
make a dull click. In this case the ear, after a little practice, can learn readily
how to distinguish the number of downward impulses that have been given
to the key.
The Morse Telegraph Code

Example in Use.—Let us take an example in the word "electrical."

p. 97
The operator first makes a dot, which means a sharp and a dull click close
together; there is then a brief interval, then a lapse, after which there is a
sharp click, followed, after a comparatively longer interval, with the dull
click. Now a dash by itself may be an L, a T, or the figure 0, dependent
upon its length. The short dash is T, and the longest dash the figure 0. The
operator will soon learn whether it is either of these or the letter L, which is
intermediate in length.
In time the sender as well as receiver will give a uniform length to the dash
impulse, so that it may be readily distinguished. In the same way, we find
that R, which is indicated by a dot, is followed, after a short interval, by two
dots. This might readily be mistaken for the single dot for E and the two
dots for I, were it not that the time element in R is not as long between the
first and second dots, as it ordinarily is between the single dot of E when
followed by the two dots of I.

p. 98

CHAPTER XToC
HIGH TENSION APPARATUS, CONDENSERS, ETC.

Induction.—One of the most remarkable things in electricity is the action
of induction—that property of an electric current which enables it to pass
from one conductor to another conductor through the air. Another singular
and interesting thing is that the current so transmitted across spaces changes
its direction of flow, and, furthermore, the tension of such a current may be
changed by transmitting it from one conductor to another.
Low and High Tension.—In order to effect this latter change—that is, to
convert it from a low tension to a high tension—coils are used, one coil
being wound upon the other; one of these coils is called the primary and the
other the secondary. The primary coil receives the current from the battery,
or source of electrical power, and the secondary coil receives charges, and
transmits the current.
For an illustration of this examine Fig. 70, in which you will note a coil of
heavy wire (A), around which is wound a coil of fine wire (B). If, for
p. 99
instance, the primary coil has a low voltage, the secondary coil will have a
high voltage, or tension. Advantage is taken of this phase to use a few cells,
as a primary battery, and then, by a set of Induction Coils, as they are
called, to build up a high-tension electro-motive force, so that the spark will
jump across a gap, as shown at C, for the purpose of igniting the charges of
gas in a gasoline motor; or the current may be used for medical batteries,
and for other purposes.

Fig. 70. Induction Coil and Circuit

The current passes, by induction, from the primary to the secondary coil. It
passes from a large conductor to a small conductor, the small conductor
having a much greater resistance than the large one.
Elastic Property of Electricity.—While electricity has no resiliency, like
a spring, for instance, still it acts in the manner of a cushion under certain
conditions. It may be likened to an oscillating spring acted upon by a bar
p. 100
Referring to Fig. 71, we will assume that the bar A in falling down upon the
spring B compresses the latter, so that at the time of greatest compression
the bar goes down as far as the dotted line C. It is obvious that the spring B
will throw the bar upwardly. Now, electricity appears to have a kind of
elasticity, which characteristic is taken advantage of in order to increase the
efficiency of the induction in the coil.

Fig. 71. Illustrating Elasticity

The Condenser.—To make a condenser, prepare two pine boards like A,
say, eight by ten inches and a half inch thick, and shellac thoroughly on all
sides. Then prepare sheets of tinfoil (B), six by eight inches in size, and also
sheets of paraffined paper (C), seven by nine inches in dimensions. Also cut
out from the waste pieces of tinfoil strips (D), one inch by two inches. To
build up the condenser, lay down a sheet of paraffined paper (C), then a
p. 101
sheet of tinfoil (B), and before putting on the next sheet of paraffined paper
lay down one of the small strips (D) of tinfoil, as shown in the illustration,
so that its end projects over one end of the board A; then on the second
sheet of paraffine paper lay another sheet of tinfoil, and on this, at the
opposite end, place one of the small strips (D), and so on, using from 50 to
100 of the tinfoil sheets. When the last paraffine sheet is laid on, the other
board is placed on top, and the whole bound together, either by wrapping
cords around the same or by clamping them together with bolts.

Fig. 72. Condenser

You may now make a hole through the projecting ends of the strips, and you
will have two sets of tinfoil sheets, alternately connected together at
opposite ends of the condenser.
Care should be exercised to leave the paraffine sheets perfect or without
p. 102
holes. You can make these sheets yourself by soaking them in melted
paraffine wax.
Connecting Up a Condenser.—When completed, one end of the condenser
is connected up with one terminal of the secondary coil, and the other end
of the condenser with the other secondary terminal.

Fig. 73. High-tension Circuit

In Fig. 73 a high-tension circuit is shown. Two coils, side by side, are
always used to show an induction coil, and a condenser is generally shown,
as illustrated, by means of a pair of forks, one resting within the other.
The Interrupter.—One other piece of mechanism is necessary, and that is
an Interrupter, for the purpose of getting the effect of the pulsations given
out by the secondary coil.
A simple current interrupter is made as follows: Prepare a wooden base (A),
one inch thick, six inches wide, and twelve inches long. Upon this mount a
toothed wheel (B), six inches in diameter, of thin sheet metal, or a p.brass
103

gear wheel will answer the purpose. The standard (C), which supports the
wheel, may be of metal bent up to form two posts, between which the
crankshaft (D) is journaled. The base of the posts has an extension plate (E),
with a binding post for a wire. At the front end of the base is an L-shaped
strip (F), with a binding post for a wire connection, and the upwardly
projecting part of the strip contacts with the toothed wheel. When the wheel
B is rotated the spring finger (F) snaps from one tooth to the next, so that,
momentarily, the current is broken, and the frequency is dependent upon the
speed imparted to the wheel.

Fig. 74. Current Interrupter

Uses of High-tension Coils.—This high-tension coil is made use of, and is
the essential apparatus in wireless telegraphy, as we shall see in the chapter
treating upon that subject.

p. 104

CHAPTER XIToC
WIRELESS TELEGRAPHY

Telegraphing Without Wires.—Wireless telegraphy is an outgrowth of the
ordinary telegraph system. When Maxwell, and, later on, Hertz, discovered
that electricity, magnetism, and light were transmitted through the ether, and
that they differed only in their wave lengths, they laid the foundations for
wireless telegraphy. Ether is a substance which is millions and millions of
times lighter than air, and it pervades all space. It is so unstable that it is
constantly in motion, and this phase led some one to suggest that if a proper
electrical apparatus could be made, the ether would thereby be disturbed
sufficiently so that its impulses would extend out a distance proportioned to
the intensity of the electrical agitation thereby created.
Surging Character of High-tension Currents.—When a current of
electricity is sent through a wire, hundreds of miles in length, the current
surges back and forth on the wire many thousands of times a second. Light
comes to us from the sun, over 90,000,000 of miles, through the ether. It is
p. 105
as reasonable to suppose, or infer, that the ether can, therefore, convey an
electrical impulse as readily as does a wire.
It is on this principle that impulses are sent for thousands of miles, and no
doubt they extend even farther, if the proper mechanism could be devised to
detect movement of the waves so propagated.
The Coherer.—The instrument for detecting these impulses, or
disturbances, in the ether is generally called a coherer, although detector is
the term which is most satisfactory. The name coherer comes from the first
practical instrument made for this purpose.

Fig. 75. Wireless Telegraphy Coherer

How Made.—The coherer is simply a tube, say, of glass, within which is
placed iron filings. When the oscillations surge through the secondary coil
the pressure or potentiality of the current finally causes it to leap across the
small space separating the filings and, as it were, it welds together their
p. 106
edges so that a current freely passes. The bringing together of the particles,
under these conditions, is called cohering.
Fig. 75 shows the simplest form of coherer. The posts (A) are firmly affixed
to the base (B), each post having an adjusting screw (C) in its upper end,
and these screw downwardly against and serve to bind a pair of horizontal
rods (D), the inner ends of which closely approach each other. These may
be adjusted so as to be as near together or as far apart as desired. E is a glass
tube in which the ends of the rods (D) rest, and between the separated ends
of the rods (D) the iron filings (F) are placed.
The Decoherers.—For the purpose of causing the metal filings to fall apart,
or decohere, the tube is tapped lightly, and this is done by a little object like
the clapper of an electric bell.
In practice, the coils and the parts directly connected with it are put together
on one base.
The Sending Apparatus.—Fig. 76 shows a section of a coil with its
connection in the sending station. The spark gap rods (A) may be swung so
as to bring them closer together or farther apart, but they must not at any
time contact with each other.
The induction coil has one terminal of the primary coil connected up by a
p. 107
wire (B) with one post of a telegraph key, and the other post of the key has
a wire connection (C), with one side of a storage battery. The other side of
the battery has a wire (D) running to the other terminal of the primary.

Fig. 76. Wireless Sending Apparatus

The secondary coil has one of its terminals connected with a binding post
(E). This binding post has an adjustable rod with a knob (F) on its end, and
the other binding post (G), which is connected up with the other terminal of
p. 108
the secondary coil, carries a similar adjusting rod with a knob (H).
From the post (E) is a wire (I), which extends upwardly, and is called the
aerial wire, or wire for the antennæ, and this wire also connects with one
side of the condenser by a conductor (J). The ground wire (K) connects with
the other binding post (G), and a branch wire (L) also connects the ground
wire (K) with one end of the condenser.

Fig. 77. Wireless Receiving Apparatus

The Receiving Apparatus.—The receiving station, on the other hand, has
neither condenser, induction coil, nor key. When the apparatus is in
operation, the coherer switch is closed, and the instant a current passes

through the coherer and operates the telegraph sounder, the galvanometer
indicates the current.
Of course, when the coherer switch is closed, the battery operates the
decoherer
p. 109
How the Circuits are Formed.—By referring again to Fig. 76, it will be
seen that when the key is depressed, a circuit is formed from the battery
through wire B to the primary coil, and back again to the battery through
wire D. The secondary coil is thereby energized, and, when the full
potential is reached, the current leaps across the gap formed between the
two knobs (F, H), thereby setting up a disturbance in the ether which is
transmitted through space in all directions.
It is this impulse, or disturbance, which is received by the coherer at the
receiving station, and which is indicated by the telegraph sounder.

p. 110

CHAPTER XIIToC
THE TELEPHONE

Vibrations.—Every manifestation in nature is by way of vibration. The
beating of the heart, the action of the legs in walking, the winking of the
eyelid; the impulses from the sun, which we call light; sound, taste and
color appeal to our senses by vibratory means, and, as we have hereinbefore
stated, the manifestations of electricity and magnetism are merely
vibrations of different wave lengths.
The Acoustic Telephone.—That sound is merely a product of vibrations
may be proven in many ways. One of the earliest forms of telephones was
simply a "sound" telephone, called the Acoustic Telephone. The principle of
this may be illustrated as follows:
Take two cups (A, B), as in Fig. 78, punch a small hole through the bottom
of each, and run a string or wire (C) from the hole of one cup to that of the
other, and secure it at both ends so it may be drawn taut. Now, by talking
into the cup (A) the bottom of it will vibrate to and fro, as shown by the
p. 111
dotted lines and thereby cause the bottom of the other cup (B) to vibrate in
like manner, and in so vibrating it will receive not only the same amplitude,
but also the same character of vibrations as the cup (A) gave forth.

Fig. 78. Acoustic Telephone

Fig. 79. Illustrating Vibrations

Sound Waves.—Sound waves are long and short; the long waves giving
sounds which are low in the musical scale, and the short waves high
musical tones. You may easily determine this by the following experiment:
Stretch a wire, as at B (Fig. 79), fairly tight, and then vibrate it. The
amplitude of the vibration will be as indicated by dotted line A. Now,
stretch it very tight, as at C, so that the amplitude of vibration will be as
shown at E. By putting your ear close to the string you will find that while
p. 112
A has a low pitch, C is very much higher. This is the principle on which
stringed instruments are built. You will note that the wave length, which
represents the distance between the dotted lines A is much greater than E.
Hearing Electricity.—In electricity, mechanism has been made to enable
man to note the action of the current. By means of the armature, vibrating in
front of a magnet, we can see its manifestations. It is now but a step to
devise some means whereby we may hear it. In this, as in everything else
electrically, the magnet comes into play.

Fig. 80. The Magnetic Field

In the chapter on magnetism, it was stated that the magnetic field extended
out beyond the magnet, so that if we were able to see the magnetism, the
end of a magnet would appear to us something like a moving field,
represented by the dotted lines in Fig. 80.
p. 113
The magnetic field is shown in Fig. 80 at only one end, but its
manifestations are alike at both ends. It will be seen that the magnetic field
extends out to a considerable distance and has quite a radius of influence.
The Diaphragm in a Magnetic Field.—If, now, we put a diaphragm (A) in
this magnetic field, close up to the end of the magnet, but not so close as to

touch it, and then push it in and out, or talk into it so that the sound waves
strike it, the movement or the vibration of the diaphragm (A) will disturb
the magnetic field emanating from the magnet, and this disturbance of the
magnetic field at one end of the magnet also affects the magnetic field at the
other end in the same way, so that the disturbance there will be of the same
amplitude. It will also display the same characteristics as did the magnetic
field when the diaphragm (A) disturbed it.
A Simple Telephone Circuit.—From this simple fact grew the telephone. If
two magnets are connected up in the same circuit, so that the magnetic
fields of the two magnets have the same source of electric power, the
disturbance of one diaphragm will affect the other similarly, just the same
as the two magnetic fields of the single magnet are disturbed in unison.
How to Make a Telephone.—For experimental and testing purposes two of
these telephones should be made at the same time. The case or holderp. 114(A)
may be made either of hard wood or hard rubber, so that it is of insulating
material. The core (B) is of soft iron, ⅜ inch in diameter and 5 inches long,
bored and threaded at one end to receive a screw (C) which passes through
the end of the case (A).
The enlarged end of the case should be, exteriorly, 2¼ inches in diameter,
and the body of the case 1 inch in diameter.

Fig. 81. Section of Telephone Receiver

Interiorly, the large end of the case is provided with a circular recess 1¾
inches in diameter and adapted to receive therein a spool which is,
diametrically, a little smaller than the recess. The spool fits fairly tight upon
the end of the core, and when in position rests against an annular shoulder
in the recess. A hollow space (F) is thus provided behind the spool (D), so

p. 115
the two wires from the magnet may have room where they emerge from the
spool.
The spool is a little shorter than the distance between the shoulder (E) and
the end of the casing, at G, and the core projects only a short distance
beyond the end of the spool, so that when the diaphragm (H) is put upon the
end of the case, and held there by screws (I) it will not touch the end of the
core. A wooden or rubber mouthpiece (J) is then turned up to fit over the
end of the case.

Fig. 82. The Magnet and Receiver Head

The spool (D) is made of hard rubber, and is wound with No. 24 silk-
covered wire, the windings to be well insulated from each other. The two
ends of the wire are brought out, and threaded through holes (K) drilled
longitudinally through the walls of the case, and affixed to the end by
means of screws (L), so that the two wires may be brought together and
connected with a duplex wire (M)
p. 116
As the screw (C), which holds the core in place, has its head hidden within
a recess, which can be closed up by wax, the two terminals of the wires are
well separated so that short-circuiting cannot take place.
Telephone Connections.—The simplest form of telephone connection is
shown in Fig. 83. This has merely the two telephones (A and B), with a
single battery (C) to supply electricity for both. One line wire (D) connects
the two telephones directly, while the other line (E) has the battery in its
circuit.

Fig. 83. Simple Telephone Connection

Complete Installation.—To install a more complete system requires, at
each end, a switch, a battery and an electro-magneto bell. You may use, for
this purpose, a bell, made as shown in the chapter on bells.
Fig. 84 shows such a circuit. We now dispense with one of the line wires,
because it has been found that the ground between the two stations serves as
a conductor, so that only one line wire (A) is necessary to connect directly
p. 117
with the telephones of the two stations. The telephones (B, B', respectively)
have wires (C, C') running to the pivots of double-throw switches (D, D'),
one terminal of the switches having wires (E, E'), which go to electric bells
(F, F'), and from the bells are other wires (G, G'), which go to the ground.
The ground wires also have wires (H, H'), which go to the other terminals
of the switch (D, D'). The double-throw switch (D, D'), in the two stations,
is thrown over so the current, if any should pass through, will go through
the bell to the ground, through the wires (E, G or E', G').

Fig. 84. Telephone Stations in Circuit

Now, supposing the switch (D'), in station 2, should be thrown over so it
contacts with the wire (H'). It is obvious that the current will then flow from
the battery (I') through wires (H', C') and line (A) to station 1; then through
wire C, switch D, wire E to the bell F, to the ground through wire G. From
p. 118
wire G the current returns through the ground to station 2, where it flows up
wire G' to the battery, thereby completing the circuit.

Fig. 85. Illustrating Light Contact Points

The operator at station 2, having given the signal, again throws his switch
(D') back to the position shown in Fig. 84, and the operator at station 1
throws on his switch (D), so as to ring the bell in station 2, thereby
answering the signal, which means that both switches are again to be
thrown over so they contact with the battery wires (H and H'), respectively.
When both are thus thrown over, the bells (G, G') are cut out of the circuit,
and the batteries are both thrown in, so that the telephones are now ready
for talking purposes.
Microphone.—Originally this form of telephone system was generally
employed, but it was found that for long distances a more sensitive
instrument was necessary.
Light Contact Points.—In 1877 Professor Hughes discovered,
accidentally, that a light contact point in an electric circuit augmented the
sound in a telephone circuit. If, for instance, a light pin, or a nail (A,p. Fig.
119

85) should be used to connect the severed ends of a wire (B), the sounds in
the telephone not only would be louder, but they would be more distinct,
and the first instrument made practically, to demonstrate this, is shown in
Fig. 86.

Fig. 86. Microphone Fig. 87. Transmitter

How to Make a Microphone.—This instrument has simply a base (A) of
wood, and near one end is a perpendicular sounding-board (B) of wood, to
one side of which is attached, by wax or otherwise, a pair of carbon blocks
(C, D). The lower carbon block (C) has a cup-shaped depression in its upper
side, and the upper block has a similar depression in its lower side. A

carbon pencil (E) is lightly held within these cups, so that the lightest
p. 120
contact of the upper end of the pencil with the carbon block, makes the
instrument so sensitive that a fly, walking upon the sounding-board, may be
distinctly heard through the telephone which is in the circuit.
Microphone the Father of the Transmitter.—This instrument has been
greatly modified, and is now used as a transmitter, the latter thereby taking
the place of the pin (A), shown in Fig. 85.
Automatic Cut-outs for Telephones.—In the operation of the telephone,
the great drawback originally was in inducing users of the lines to replace
or adjust their instruments carefully. When switches were used, they would
forget to throw them back, and all sorts of trouble resulted.
It was found necessary to provide an automatic means for throwing in and
cutting out an instrument, this being done by hanging the telephone on the
hook, so that the act merely of leaving the telephone made it necessary, in
replacing the instrument, to cut out the apparatus.
Before describing the circuiting required for these improvements, we show,
in Fig. 87, a section of a transmitter.
A cup-shaped case (A) is provided, made of some insulating material,
which has a diaphragm (B) secured at its open side. This diaphragm carries
the carbon pencil (C) on one side and from the blocks which support the
p. 121
carbon pencil the wires run to binding posts on the case. Of course the
carbon supporting posts must be insulated from each other, so the current
will go through the carbon pencil (C).
Complete Circuiting with Transmitter.—In showing the circuiting (Fig.
88) it will not be possible to illustrate the boxes, or casings, which receive
the various instruments. For instance, the hook which carries the telephone
or the receiver, is hinged within the transmitter box. The circuiting is all that
it is intended to show.

Fig. 88. Complete Telephonic Circuit

The batteries of the two stations are connected up by a wire (A), unless a
ground circuit is used. The other side of each battery has a wire connection
(B, B') with one terminal of the transmitter, and the other terminal of the
transmitter has a wire (C, C') which goes to the receiver. From the other
terminal of the receiver is a wire (D, D') which leads to the upper stop
contact (E, E') of the telephone hook. A wire (F, F') from the lowerp. stop
122

contact (G, G') of the hook goes to one terminal of the bell, and from the
other terminal of the bell is a wire (H, H') which makes connection with the
line wire (A). In order to make a complete circuit between the two stations,
a line wire (I) is run from the pivot of the hook in station 1 to the pivot of
the hook in station 2.
In the diagram, it is assumed that the receivers are on the hooks, and that
both hooks are, therefore, in circuit with the lower contacts (G, G'), so that
the transmitter and receiver are both out of circuit with the batteries, and the
bell in circuit; but the moment the receiver, for instance, in station 1 is taken
off the hook, the latter springs up so that it contacts with the stop (E), thus
establishing a circuit through the line wire (I) to the hook of station 2, and
from the hook through line (F') to the bell. From the bell, the line (A)
carries the current back to the battery of station (A), thence through the wire
(B) to the transmitter wire (C) to receiver and wire (D) to the post (E),
thereby completing the circuit.
When, at station 2, the receiver is taken off the hook, and the latter contacts
with the post (E'), the transmitter and receiver of both stations are in circuit
with each other, but both bells are cut out.

p. 123

CHAPTER XIIIToC
ELECTROLYSIS, WATER PURIFICATION,
ELECTROPLATING

Decomposing Liquids.—During the earlier experiments in the field of
electricity, after the battery or cell was discovered, it was noted that when a
current was formed in the cell, the electrolyte was charged and gases
evolved from it. A similar action takes place when a current of electricity
passes through a liquid, with the result that the liquid is decomposed—that
is, the liquid is broken up into its original compounds. Thus, water is
composed of two parts, by bulk, of hydrogen and of oxygen, so that if two
electrodes are placed in water, and a current is sent through the electrodes in
either direction, all the water will finally disappear in the form of hydrogen
and oxygen gases.
Making Hydrogen and Oxygen.—During this electrical action, the
hydrogen is set free at the negative pole and the oxygen at the positive pole.
A simple apparatus, which any boy can make, to generate pure oxygen and
pure hydrogen, is shown in Fig. 89.
It is constructed of a glass or earthen jar (A), preferably square, to which is
p. 124
fitted a wooden top (B), this top being provided with a packing ring (C), so
as to make it air-tight. Within is a vertical partition (D), the edges of which,
below the cap, fit tightly against the inner walls of the jar. This partition
extends down into the jar a sufficient distance so it will terminate below the
water level. A pipe is fitted through the top on each side of the partition, and
each pipe has a valve. An electrode, of any convenient metal, is secured at
its upper end to the top of the cap, on each side of the partition. These
electrodes extend down to the bottom of the jar, and an electric wire
connects with each of them at the top.

Fig. 89. Device for Making Hydrogen and Oxygen

If a current of electricity is passed through the wires and the electrodes, in
the direction shown by the darts, hydrogen will form at the negative p.pole,
125

and oxygen at the positive pole. These gases will escape upwardly, so that
they will be trapped in their respective compartments, and may be drawn
off by means of the pipes.
Purifying Water.—Advantage is taken of this electrolytic action, to purify
water. Oxygen is the most wonderful chemical in nature. It is called the
acid-maker of the universe. The name is derived from two words, oxy and
gen; one denoting oxydation, and the other that it generates. In other words,
it is the generator of oxides. It is the element which, when united with any
other element, produces an acid, an alkali or a neutral compound.
Rust.—For instance, iron is largely composed of ferric acid. When oxygen,
in a free or gaseous state, comes into contact with iron, it produces ferrous
oxide, which is recognized as rust.
Oxygen as a Purifier.—But oxygen is also a purifier. All low forms of
animal life, like bacteria or germs in water, succumb to free oxygen. By free
oxygen is meant oxygen in the form of gas.
Composition of Water.—Now, water, in which harmful germs live, is one-
third oxygen. Nevertheless, the germs thrive in water, because the oxygen is
p. 126
in a compound state, and, therefore, not an active agent. But if oxygen, in
the form of gas, can be forced through water, it will attack the germs, and
destroy them.

Common Air Not a Good Purifier.—Water may be purified, to a certain
extent, by forcing common air through it, and the foulest water, if run over
rocks, will be purified, in a measure, because air is intermingled with it. But
common air is composed of four-fifths nitrogen, and only one-fifth oxygen,
and, as nitrogen is the staple article of food for bacteria, the purifying
method by air is not effectual.
Pure Oxygen.—When, however, oxygen is generated from water, by means
of electrolysis, it is pure; hence is more active and is not tainted by a life-
giving substance for germs, such as nitrogen.
The mechanism usually employed for purifying water is shown in Fig. 90.
A Water Purifier.—The case (A, Fig. 90) may be made of metal or of an
insulating material. If made of metal it must be insulated within with slate,
glass, marble or hard rubber, as shown at B. The case is provided with
exterior flanges (C, D), with upper and lower ends, and it is mounted upon a
base plate (E) and affixed thereto by bolts. The upper end has a conically-
formed cap (F) bolted to the flanges (C), and this has an outlet to which a
pipe (G) is attached. The water inlet pipe (H) passes through the lowerp. 127
end
of the case (A). The electrodes (I, J) are secured, vertically, within the case,
separated from each other equidistant, each alternate electrode being
connected up with one wire (K), and the alternate electrodes with a wire
(L).

Fig. 90. Electric Water Purifier
p. 128
When the water passes upwardly, the decomposed or gaseous oxygen
percolates through the water and thus attacks the germs and destroys them.
The Use of Hydrogen in Purification.—On the other hand, the hydrogen
also plays an important part in purifying the water. This depends upon the
material of which the electrodes are made. Aluminum is by far the best
material, as it is one of nature's most active purifiers. All clay contains
aluminum, in what is known as the sulphate form, and water passing
through the clay of the earth thereby becomes purified, because of this
element.
Aluminum Electrodes.—When this material is used as the electrodes in
water, hydrate of aluminum is formed, or a compound of hydrogen and
oxygen with aluminum. The product of decomposition is a flocculent matter
which moves upwardly through the water, giving it a milky appearance.
This substance is like gelatine, so that it entangles or enmeshes the germ
life and prevents it from passing through a filter.
If no filter is used, this flocculent matter, as soon as it has given off the
gases, will settle to the bottom and carry with it all decomposed matter,

p. 129
such as germs and other organic matter attacked by the oxygen, which has
become entangled in the aluminum hydrate.
Electric Hand Purifier.—An interesting and serviceable little purifier may
be made by any boy with the simplest tools, by cutting out three pieces of
sheet aluminum. Hard rolled is best for the purpose. It is better to have one
of the sheets (A), the middle one, thicker than the two outer plates (B).

Fig. 91. Portable Electric Purifier

Let each sheet be 1½ inches wide and 5½ inches thick. One-half inch from
p. 130
the upper ends of the two outside plates (B, B) bore bolt holes (C), each of
these holes being a quarter of an inch from the edge of the plate. The inside
plate (A) has two large holes (D) corresponding with the small holes (C) in
the outside plates. At the upper end of this plate form a wing (E), ½ inch
wide and ½ inch long, provided with a small hole for a bolt. Next cut out
two hard-rubber blocks (F), each 1½ inches long, 1 inch wide and ⅜ inch
thick, and then bore a hole (G) through each, corresponding with the small
holes (C) in the plates (B). The machine is now ready to be assembled. If
the inner plate is ⅛ inch thick and the outer plates each 1/16 inch thick, use
two small eighth-inch bolts 1¼ inches long, and clamp together the p.three 131

plates with these bolts. One of the bolts may be used to attach thereto one of
the electric wires (H), and the other wire (I) is attached by a bolt to the wing
(E).

Figs. 92-95. Details of Portable Purifier

Such a device will answer for a 110-volt circuit, in ordinary water. Now fill
a glass nearly full of water, and stand the purifier in the glass. Within a few
minutes the action of electrolysis will be apparent by the formation of
numerous bubbles on the plates, followed by the decomposition of the
organic matter in the water. At first the flocculent decomposed matter will
rise to the surface of the water, but before many minutes it will settle to the
bottom of the glass and leave clear water above.
Purification and Separation of Metals.—This electrolytic action is utilized
in metallurgy for the purpose of producing pure metals, but it is more
largely used to separate copper from its base. In order to utilize a current for
this purpose, a high ampere flow and low voltage are required. The sheets
of copper, containing all of its impurities, are placed within a tank, parallel
with a thin copper sheet. The impure sheet is connected with the positive
pole of an electroplating dynamo, and the thin sheet of copper is connected
p. 132
with the negative pole. The electrolyte in the tank is a solution of sulphate
of copper. The action of the current will cause the pure copper in the impure
sheet to disintegrate and it is then carried over and deposited upon the thin
sheet, this action continuing until the impure sheet is entirely eaten away.
All the impurities which were in the sheet fall to the bottom of the tank.
Other metals are treated in the same way, and this treatment has a very wide
range of usefulness.
Electroplating.—The next feature to be considered in electrolysis is a most
interesting and useful one, because a cheap or inferior metal may be coated
by a more expensive metal. Silver and nickel plating are brought about by

this action of a current passing through metals, which are immersed in an
electrolyte.
Plating Iron with Copper.—We have room in this chapter for only one
concrete example of this work, which, with suitable modifications, is an
example of the art as practiced commercially. Iron, to a considerable extent,
is now being coated with copper to preserve it from rust. To carry out this
work, however, an electroplating dynamo, of large amperage, is required,
the amperage, of course, depending upon the surface to be treated at one
time. The pressure should not exceed 5 volts
The iron surface to be treated should first be thoroughly cleansed, andp.then
133

immediately put into a tank containing a cyanide of copper solution. Two
forms of copper solution are used, namely, the cyanide, which is a salt
solution of copper, and the sulphate, which is an acid solution of copper.
Cyanide is first used because it does not attack the iron, as would be the
case if the sulphate solution should first come into contact with the iron.
A sheet of copper, termed the anode, is then placed within the tank, parallel
with the surface to be plated, known as the cathode, and so mounted that it
may be adjusted to or from the iron surface, or cathode. A direct current of
electricity is then caused to flow through the copper plate and into the iron
plate or surface, and the plating proceeded with until the iron surface has a
thin film of copper deposited thereon. This is a slow process with the
cyanide solution, so it is discontinued as soon as possible, after the iron
surface has been completely covered with copper. This copper surface is
thoroughly cleaned off to remove therefrom the saline or alkaline solution,
and it is then immersed within a bath, containing a solution of sulphate of
p. 134
copper. The current is then thrown on and allowed so to remain until it has
deposited the proper thickness of copper.
Direction of Current.—If a copper and an iron plate are put into a copper
solution and connected up in circuit with each other, a primary battery is
thereby formed, which will generate electricity. In this case, the iron will be
positive and the copper negative, so that the current within such a cell
would flow from the iron (in this instance, the anode) to the negative, or
cathode.

The action of electroplating reverses this process and causes the current to
flow from the copper to the iron (in this instance, the cathode).

p. 135

CHAPTER XIVToC
ELECTRIC HEATING, THERMO ELECTRICITY

Generating Heat in a Wire.—When a current of electricity passes through
a conductor, like a wire, more or less heat is developed in the conductor.
This heat may be so small that it cannot be measured, but it is, nevertheless,
present in a greater or less degree. Conductors offer a resistance to the
passage of a current, just the same as water finds a resistance in pipes
through which it passes. This resistance is measured in ohms, as explained
in a preceding chapter, and it is this resistance which is utilized for electric
heating.
Resistance of Substances.—Silver offers less resistance to the passage of a
current than any other metal, the next in order is copper, while iron is,
comparatively, a poor conductor.
The following is a partial list of metals, showing their relative conductivity:
Silver 1.
Copper 1.04 to 1.09
Gold 1.38 to 1.41
Aluminum 1.64 p. 136
Zinc 3.79
Nickel 4.69
Iron 6.56
Tin 8.9
Lead 13.2
German Silver 12.2 to 15

From this table it will be seen that, for instance, iron offers six and a half
times the resistance of silver, and that German silver has fifteen times the
resistance of silver.
This table is made up of strands of the different metals of the same
diameters and lengths, so as to obtain their relative values.

Sizes of Conductors.—Another thing, however, must be understood. If two
conductors of the same metal, having different diameters, receive the same
current of electricity, the small conductor will offer a greater resistance than
the large conductor, hence will generate more heat. This can be offset by
increasing the diameter of the conductor. The metal used is, therefore, of
importance, on account of the cost involved.
Comparison of Metals.—A conductor of aluminum, say, 10 feet long and of
the same weight as copper, has a diameter two and a quarter times greater
than copper; but as the resistance of aluminum is 50 per cent. more than that
p. 137
of silver, it will be seen that, weight for weight, copper is the cheaper,
particularly as aluminum costs fully three times as much as copper.

Fig. 96. Simple Electric Heater

The table shows that German silver has the highest resistance. Of course,
there are other metals, like antimony, platinum and the like, which have still
higher resistance. German silver, however, is most commonly used,
although there are various alloys of metal made which have high resistance
and are cheaper.
The principle of all electric heaters is the same, namely, the resistancep. of
138
a
conductor to the passage of a current, and an illustration of a water heater
will show the elementary principles in all of these devices.

A Simple Electric Heater.—In Fig. 96 the illustration shows a cup or
holder (A) for the wire, made of hard rubber. This may be of such diameter
as to fit upon and form the cover for a glass (B). The rubber should be ½
inch thick. Two holes are bored through the rubber cup, and through them
are screwed two round-headed screws (C, D), each screw being 1½ inches
long, so they will project an inch below the cap. Each screw should have a
small hole in its lower end to receive a pin (E) which will prevent the
resistance wire from slipping off.
The resistance wire (F) is coiled for a suitable length, dependent upon the
current used, one end being fastened by wrapping it around the screw (C).
The other end of the wire is then brought upwardly through the interior of
the coil and secured in like manner to the other screw (D).
Caution must be used to prevent the different coils or turns from touching
each other. When completed, the coil may be immersed in water, the current
turned on, and left so until the water is sufficiently heated.

Fig. 97. Resistance Device

Fig. 98. Resistance Device
. 139
How to Arrange for Quantity of Current Used.—It is difficult p
to
determine just the proper length the coil should be, or the sizes of the wire,
unless you know what kind of current you have. You may, however, rig up
your own apparatus for the purpose of making it fit your heater, by
preparing a base of wood (A) 8 inches long, 3 inches wide and 1 inch thick.
On this mount four electric lamp sockets (B). Then connect the inlet wire
(C) by means of short pieces of wire (D) with all the sockets on one side.
The outlet wire (E) should then be connected up with the other sides of the

sockets by the short wires (F). If, now, we have one 16-candlepower lamp
in one of the sockets, there is a half ampere going through the wires (C, F).
p. 140
If there are two lamps on the board you will have 1 ampere, and so on. By
this means you may readily determine how much current you are using and
it will also afford you a means of finding out whether you have too much or
too little wire in your coil to do the work.

Fig. 99. Plan View of Electric Iron

An Electric Iron.—An electric iron is made in the same way. The upper
side of a flatiron has a circular or oval depression (A) cast therein, and a
spool of slate (B) is made so it will fit into the depression and the high
resistance wire (C) is wound around this spool, and insulating material,
such as asbestos, must be used to pack around it. Centrally, the slate spool
has an upwardly projecting circular extension (D) which passes through the
cap or cover (E) of the iron. The wires of the resistance coil are then
brought through this circular extension and are connected up withp. 141 the
source of electrical supply. Wires are now sold for this purpose, which are
adapted to withstand an intense heat.

Fig. 100. Section of Electric Iron

The foregoing example of the use of the current, through resistance wires,
has a very wide application, and any boy, with these examples before him,
can readily make these devices.
Thermo Electricity.—It has long been the dream of scientists to convert
heat directly into electricity. The present practice is to use a boiler to
generate steam, an engine to provide the motion, and a dynamo to convert
that motion into electricity. The result is that there is loss in the process of
converting the fuel heat into steam; loss to change the steam into motion,
p. 142
and loss to make electricity out of the motion of the engine. By using water-
power there is less actual loss; but water-power is not available everywhere.
Converting Heat Directly Into Electricity.—Heat may be converted
directly into electricity without using a boiler, an engine or a dynamo, but it
has not been successful from a commercial standpoint. It is interesting,
however, to know and understand the subject, and for that reason it is
explained herein.
Metals; Electric Positive-Negative.—To understand the principle, it may
be stated that all metals are electrically positive-negative to each other. You
will remember that it has hereinbefore been stated that if, for instance, iron
and copper are put into an acid solution, a current will be created or
generated thereby. So with zinc and copper, the usual primary battery
elements. In all such cases an electrolyte is used.
Thermo-electricity dispenses with the electrolyte, and nothing is used but
the metallic elements and heat. The word thermo means heat. If, now, we
can select two strips of different metals, and place them as far apart as
possible—that is, in their positive-negative relations with each other, and
unite the end of one with one end of other by means of a rivet, and then heat
p. 143
the riveted ends, a current will be generated in the strips. If, for instance, we
use an iron in conjunction with a copper strip, the current will flow from the
copper to the iron, because copper is positive to iron, and iron negative to
copper. It is from this that the term positive-negative is taken.
The two metals most available, which are thus farthest apart in the scale of
positive-negative relation, are bismuth and antimony.

Fig. 101. Thermo-Electric Couple

In Fig. 101 is shown a thermo-electric couple (A, B) riveted together, with
thin outer ends connected by means of a wire (C) to form a circuit. A
galvanometer (D) or other current-testing means is placed in this circuit. A
lamp is placed below the joined ends.
Thermo-Electric Couples.—Any number of these couples may be put
together and joined at each end to a common wire and a fairly large flow of
current obtained thereby.
p. 144
One thing must be observed: A current will be generated only so long as
there exists a difference in temperature between the inner and the outer ends
of the bars (A, B). This may be accomplished by water, or any other cooling
means which may suggest itself.

p. 145

CHAPTER XVToC
ALTERNATING CURRENTS, CHOKING COILS,
TRANSFORMERS, CONVERTERS AND RECTIFIERS

Direct Current.—When a current of electricity is generated by a cell, it is
assumed to move along the wire in one direction, in a steady, continuous
flow, and is called a direct current. This direct current is a natural one if
generated by a cell.
Alternating Current.—On the other hand, the natural current generated by
a dynamo is alternating in its character—that is, it is not a direct, steady
flow in one direction, but, instead, it flows for an instant in one direction,
then in the other direction, and so on.
A direct-current dynamo such as we have shown in Chapter IV, is much
easier to explain, hence it is illustrated to show the third method used in
generating an electric current.
It is a difficult matter to explain the principle and operation of alternating
current machines, without becoming, in a measure, too technical for the
purposes of this book, but it is important to know the fundamentals
involved, so that the operation and uses of certain apparatus, like the
choking coil, transformers, rectifiers and converters, may be explained.p. 146
The Magnetic Field.—It has been stated that when a wire passes through
the magnetic field of a magnet, so as to cut the lines of force flowing out
from the end of a magnet, the wire will receive a charge of electricity.

Fig. 102. Cutting a Magnetic Field

To explain this, study Fig. 102, in which is a bar magnet (A). If we take a
metal wire (B) and bend it in the form of a loop, as shown, and mount the
ends on journal-bearing blocks, the wire may be rotated so that the loop will
pass through the magnetic field. When this takes place, the wire receives a
charge of electricity, which moves, say, in the direction of the darts, and
will make a complete circuit if the ends of the looped wire are joined, as
shown by the conductor (D).
Action of the Magnetized Wire.—You will remember, also that we have
pointed out how, when a current passes over a wire, it has a magnetic field
extending out around it at all points, so that while it is passing through the
magnetic field of the magnet (A), it becomes, in a measure, a magnet p.of147its
own and tries to set up in business for itself as a generator of electricity. But
when the loop leaves the magnetic field, the magnetic or electrical impulse
in the wire also leaves it.
The Movement of a Current in a Charged Wire.—Your attention is
directed, also, to another statement, heretofore made, namely, that when a
current from a charged wire passes by induction to a wire across space, so
as to charge it with an electric current, it moves along the charged wire in a
direction opposite to that of the current in the charging wire.
Now, the darts show the direction in which the current moves while it is
approaching and passing through the magnetic field. But the moment the
loop is about to pass out of the magnetic field, the current in the loop surges
back in the opposite direction, and when the loop has made a revolution and
is again entering the magnetic field, it must again change the direction of
flow in the current, and thus produce alternations in the flow thereof.
Let us illustrate this by showing the four positions of the revolving loop. In
Fig. 103 the loop (B) is in the middle of the magnetic field, moving
upwardly in the direction of the curved dart (A), and while in that position
the voltage, or the electrical impulse, is the most intense. The currentp.used
148

flows in the direction of the darts (C) or to the left.
In Fig. 104, the loop (A) has gone beyond the influence of the magnetic
field, and now the current in the loop tries to return, or reverse itself, as
shown by the dart (D). It is a reaction that causes the current to die out, so
that when the loop has reached the point farthest from the magnet, as shown

in Fig. 105, there is no current in the loop, or, if there is any, it moves
faintly in the direction of the dart (E).

Fig. 103-106. Illustrating Alternations

Current Reversing Itself.—When the loop reaches its lowest point (Fig.
106) it again comes within the magnetic field and the current commences to
flow back to its original direction, as shown by darts (C)
Self-Induction.—This tendency of a current to reverse itself, underp. 149the
conditions cited, is called self-induction, or inductance, and it would be
well to keep this in mind in pursuing the study of alternating currents.
You will see from the foregoing, that the alternations, or the change of
direction of the current, depends upon the speed of rotation of the loop past
the end of the magnet.

Fig. 107. Form for Increasing Alternations

Fig. 108. Form for Increasing Alternations

Instead, therefore, of using a single loop, we may make four loops (Fig.
107), which at the same speed as we had in the case of the single loop, will
give four alternations, instead of one, and still further, to increase the

periods of alternation, we may use the four loops and two magnets, p.as150in
Fig. 108. By having a sufficient number of loops and of magnets, there may
be 40, 50, 60, 80, 100 or 120 such alternating periods in each second. Time,
therefore, is an element in the operation of alternating currents.
Let us now illustrate the manner of connecting up and building the dynamo,
so as to derive the current from it. In Fig. 109, the loop (A) shows, for
convenience, a pair of bearings (B). A contact finger (C) rests on each, and
to these the circuit wire (D) is attached. Do not confuse these contact
fingers with the commutator brushes, shown in the direct-current motor, as
they are there merely for the purpose of making contact between the
revolving loop (A) and stationary wire (D).

Fig. 109. Connection of Alternating Dynamo
Armature

Brushes in a Direct-Current Dynamo.—The object of the brushes in the
direct-current dynamo, in connection with a commutator, is to convert this
inductance of the wire, or this effort to reverse itself into a current which
p. 151
will go in one direction all the time, and not in both directions alternately.
To explain this more fully attention is directed to Figs. 110 and 111. Let A
represent the armature, with a pair of grooves (B) for the wires. The
commutator is made of a split tube, the parts so divided being insulated
from each other, and in Fig. 110, the upper one, we shall call and designate
the positive (+) and the lower one the negative (-). The armature wire (C)
has one end attached to the positive commutator terminal and the other end
of this wire is attached to the negative terminal.

Fig. 110. Direct Current Dynamo

One brush (D) contacts with the positive terminal of the commutator and
the other brush (E) with the negative terminal. Let us assume thatp. 152 the
current impulse imparted to the wire (C) is in the direction of the dart (F,
Fig. 110). The current will then flow through the positive (+) terminal of the
commutator to the brush (D), and from the brush (D) through the wire (G)
to the brush (E), which contacts with the negative (-) terminal of the
commutator. This will continue to be the case, while the wire (C) is passing
the magnetic field, and while the brush (D) is in contact with the positive
(+) terminal. But when the armature makes a half turn, or when it reaches
that point where the brush (D) contacts with the negative (-) terminal, and
the brush (E) contacts with the positive (+) terminal, a change inp. 153 the
direction of the current through the wire (G) takes place, unless something
has happened to change it before it has reached the brushes (D, E).

Fig. 111. Circuit Wires in Direct Current Dynamo

Now, this change is just exactly what has happened in the wire (C), as we
have explained. The current attempts to reverse itself and start out on

business of its own, so to speak, with the result that when the brushes (D
and E) contact with the negative and positive terminals, respectively, the
surging current in the wire (C) is going in the direction of the dart (H)—that
is, while, in Fig. 110, the current flows from the wire (C) into the positive
terminal, and out of the negative terminal into the wire (C), the conditions
are exactly reversed in Fig. 111. Here the current in wire C flows into the
negative (-) terminal, and from the positive (+) terminal into the wire C, so
that in either case the current will flow out of the brush D and into the brush
E, through the external circuit (G).
It will be seen, therefore, that in the direct-current motor, advantage is taken
of the surging, or back-and-forth movement, of the current to pass it along
in one direction, whereas in the alternating current no such change in
direction is attempted.
. 154
Alternating Positive and Negative Poles.—The alternating current, owing p

to this surging movement, makes the poles alternately positive and negative.
To express this more clearly, supposing we take a line (A, Fig. 112), which
is called the zero line, or line of no electricity. The current may be
represented by the zigzag line (B). The lines (B) above zero (A) may be
designated as positive, and those below the line as negative. The polarity
reverses at the line A, goes up to D, which is the maximum intensity or
voltage above zero, and, when the current falls and crosses the line A, it
goes in the opposite direction to E, which is its maximum voltage in the
other direction. In point of time, if it takes one second for the current to go
from C to F, on the down line, then it takes only a half second to go from C
to G, so that the line A represents the time, and the line H the intensity, a
complete cycle being formed from C, D, F, then through F, E, C, and so on.

Fig. 112. Alternating Polarity Lines
p. 155
How an Alternating Dynamo Is Made.—It is now necessary to apply these
principles in the construction of an alternating-current machine. Fig. 113 is
a diagram representing the various elements, and the circuiting.

Fig. 113. Alternating Current Dynamo

Let A represent the ring or frame containing the inwardly projecting field
magnet cores (B). C is the shaft on which the armature revolves, and this
carries the wheel (D), which has as many radially disposed magnet cores
(E) as there are of the field magnet cores (B).
The shaft (C) also carries two pulleys with rings thereon. One of these rings
p. 156
(F) is for one end of the armature winding, and the other ring (G) for the
other end of the armature wire.
The Windings.—The winding is as follows: One wire, as at H, is first coiled
around one magnet core, the turnings being to the right. The outlet terminal
of this wire is then carried to the next magnet core and wound around that,
in the opposite direction, and so on, so that the terminal of the wire is
brought out, as at I, all of these wires being connected to binding posts (J,
J'), to which, also, the working circuits are attached.
The Armature Wires.—The armature wires, in like manner, run from the
ring (G) to one armature core, being wound from right to left, then to the
next core, which is wound to the right, afterward to the next core, which is
wound to the left, and so on, the final end of the wire being connected up
with the other ring (F). The north (N) and the south (S) poles are indicated
in the diagram.
Choking Coil.—The self-induction in a current of this kind is utilized in
transmitting electricity to great distances. Wires offer resistance, or they

impede the flow of a current, as hereinbefore stated, so that it is not
economical to transmit a direct current over long distances. This can be
done more efficiently by means of the alternating current, which is subject
p. 157
to far less loss than is the case with the direct current. It affords a means
whereby the flow of a current may be checked or reduced without
depending upon the resistance offered by the wire over which it is
transmitted. This is done by means of what is called a choking coil. It is
merely a coil of wire, wound upon an iron core, and the current to be
choked passes through the coil. To illustrate this, let us take an arc lamp
designed to use a 50-volt current. If a current is supplied to it carrying 100
volts, it is obvious that there are 50 volts more than are needed. We must
take care of this excess of 50 volts without losing it, as would happen were
we to locate a resistance of some kind in the circuit. This result we
accomplish by the introduction of the choking coil, which has the effect of
absorbing the excessive 50 volts, the action being due to its quality of self-
induction, referred to in the foregoing.

Fig. 114. Choking Coil
p. 158
In Fig. 114, A is the choking coil and B an arc lamp, connected up, in series,
with the choking coil.
The Transformer.—It is more economical to transmit 10,000 volts a long
distance than 1,000 volts, because the lower the pressure, or the voltage, the
larger must be the conductor to avoid loss. It is for this reason that 500
volts, or more, are used on electric railways. For electric light purposes,
where the current goes into dwellings, even this is too high, so a
transformer is used to take a high-voltage current from the main line and
transform it into a low voltage. This is done by means of two distinct coils
of wire, wound upon an iron core.

Fig. 115. A Transformer

In Fig. 115 the core is O-shaped, so that a primary winding (A), from the
p. 159
electrical source, can be wound upon one limb, and the secondary winding
(B) wound around the other limb. The wires, to supply the lamps, run from
the secondary coil. There is no electrical connection between the two coils,
but the action from the primary to the secondary coil is solely by induction.
When a current passes through the primary coil, the surging movement,
heretofore explained, is transmitted to the iron core, and the iron core, in
turn, transmits this electrical energy to the secondary coil.
How the Voltage Is Determined.—The voltage produced by the secondary
coil will depend upon several things, namely, the strength of the magnetism
transmitted to it; the rapidity, or periodicity of the current, and the number
of turns of wire around the coil. The voltage is dependent upon the length of
the winding. But the voltage may also be increased, as well as decreased. If
the primary has, we will say, 100 turns of wire, and has 200 volts, and the
secondary has 50 turns of wire, the secondary will give forth only one-half
as much as the primary, or 100 volts.
If, on the other hand, 400 volts would be required, the secondary should
have 200 turns in the winding.
Voltage and Amperage in Transformers.—It must not be understood that,
by increasing the voltage in this way, we are getting that much p.more 160

electricity. If the primary coil, with 100 turns, produces a current of 200
volts and 50 amperes, which would be 200 × 50 = 10,000 watts, and the
secondary coil has 50 turns, we shall have 100 volts and 100 amperes: 100
(V.) × 100 (A.) = 10,000 watts. Or, if, on the other hand, our secondary
winding is composed of 200 turns, we shall have 400 volts and 25 amperes,
400 (volts) × 25 (amperes) also gives 10,000 watts.

Necessarily, there will be some loss, but the foregoing is offered as the
theoretical basis of calculation.

p. 161

CHAPTER XVIToC
ELECTRIC LIGHTING

The most important step in the electric field, after the dynamo had been
brought to a fairly workable condition, was its utilization to make light. It
was long known prior to the discovery of practical electric dynamos, that
the electric current would produce an intense heat.
Ordinary fuels under certain favorable conditions will produce a
temperature of 4,500 degrees of heat; but by means of the electric arc, as
high as six, eight and ten thousand degrees are available.
The fact that when a conductor, in an electric current, is severed, a spark
will follow the drawing part of the broken ends, led many scientists to
believe, even before the dynamo was in a practical shape, that electricity,
sooner or later, would be employed as the great lighting agent.
When the dynamo finally reached a stage in development where its
operation could be depended on, and was made reversible, the first active
steps were taken to not only produce, but to maintain an arc between two
electrodes.
p. 162
It would be difficult and tedious to follow out the first experiments in detail,
and it might, also, be useless, as information, in view of the present
knowledge of the science. A few steps in the course of the development are,
however, necessary to a complete understanding of the subject.
Reference has been made in a previous chapter to what is called the Electric
Arc, produced by slightly separated conductors, across which the electric
current jumps, producing the brilliantly lighted area.
This light is produced by the combustion of the carbon of which the
electrodes are composed. Thus, the illumination is the result of directly
burning a fuel. The current, in passing from one electrode to the other,

through the gap, produces such an intense heat that the fuel through which
the current passes is consumed.
Carbon in a comparatively pure state is difficult to ignite, owing to its great
resistance to heat. At about 7,000 degrees it will fuse, and pass into a vapor
which causes the intense illumination.
The earliest form of electric lighting was by means of the arc, in which the
light is maintained so long as the electrodes were kept a certain distance
apart.
To do this requires delicate mechanism, for the reason that when contact is
made, and the current flows through the two electrodes, which are
p. 163
connected up directly with the coils of a magnet, the cores, or armatures,
will be magnetized. The result is that the electrode, connected with the
armature of the magnet, is drawn away from the other electrode, and the arc
is formed, between the separated ends.
As the current also passes through a resistance coil, the moment the ends of
the electrodes are separated too great a distance, the resistance prevents a
flow of the normal amount of current, and the armature is compelled to
reduce its pull. The effect is to cause the two electrodes to again approach
each other, and in doing so the arc becomes brighter.
It will be seen, therefore, that there is a constant fight between the
resistance coil and the magnet, the combined action of the two being such,
that, if properly arranged, and with powers in correct relation to each other,
the light may be maintained without undue flickering. Such devices are now
universally used, and they afford a steady and reliable means of
illumination.
Many improvements are made in this direction, as well as in the ingredients
of the electrodes. A very novel device for assuring a perfect separation at all
times between the electrodes, is by means of a pair of parallel carbons, held
p. 164
apart by a non-conductor such as clay, or some mixture of earth, a form of
which is shown in Fig. 116.
The drawing shows two electrodes, separated by a non-conducting material,
which is of such a character that it will break down and crumble away, as
the ends of the electrodes burn away.

Fig. 116. Parallel Carbons.

This device is admirable where the alternating current is used, because the
current moves back and forth, and the two electrodes are thus burned away
at the same rate of speed.
In the direct or continuous current the movement is in one direction p.only,
165

and as a result the positive electrode is eaten away twice as fast as the
negative.
This is the arc form of lamp universally used for lighting large spaces or
areas, such as streets, railway stations, and the like. It is important also as
the means for utilizing searchlight illumination, and frequently for
locomotive headlights.
Arc lights are produced by what is called the series current. This means that
the lamps are all connected in a single line. This is illustrated by reference
to Fig. 117, in which A represents the wire from the dynamo, and B, C the
two electrodes, showing the current passing through from one lamp to the
next.

Fig. 117. Arc-Lighting Circuit.

A high voltage is necessary in order to cause the current to leap across the
gap made by the separation of the electrodes
p. 166
The Incandescent System.—This method is entirely different from the arc
system. It has been stated that certain metals conduct electricity with greater
facility than others, and some have higher resistance than others. If a certain
amount of electricity is forced through some metals, they will become
heated. This is true, also, if metals, which, ordinarily, will conduct a current
freely, are made up into such small conductors that it is difficult for the
current to pass.

Fig. 118. Interrupted Conductor.

In the arc method high voltage is essential; in the incandescent plan, current
is the important consideration. In the arc, the light is produced by virtue of
the break in the line of the conductor; in the incandescent, the system is
closed at all times.
Supposing we have a wire A, a quarter of an inch in diameter, carrying a
current of, say, 500 amperes, and at any point in the circuit the wire is made
very small, as shown at B, in Fig. 118, it is obvious that the small wire
would not be large enough to carry the current.
p. 167
The result would be that the small connection B would heat up, and, finally,
be fused. While the large part of the wire would carry 500 amperes, the
small wire could not possibly carry more than, say, 10 amperes. Now these
little wires are the filaments in an electric bulb, and originally the attempt

was made to have them so connected up that they could be illuminated by a
single wire, as with the arc system above explained, one following the other
as shown in Fig. 117.

Fig. 119. Incandescent Circuit.

It was discovered, however, that the addition of each successive lamp, so
wired, would not give light in proportion to the addition, but at only about
one-fourth the illumination, and such a course would, therefore, make
electric lighting enormously expensive.
This knowledge resulted in an entirely new system of wiring up the lamps
in a circuit. This is explained in Fig. 119. In this figure A represents the
dynamo, B, B the brushes, C, D the two line wires, E the lamps, and p.F168
the
short-circuiting wires between the two main conductors C, D.
It will be observed that the wires C, D are larger than the cross wires F. The
object is to show that the main wires might carry a very heavy amperage,
while the small cross wires F require only a few amperes.
This is called the multiple circuit, and it is obvious that the entire amperage
produced by the dynamo will not be required to pass through each lamp,
but, on the other hand, each lamp takes only enough necessary to render the
filament incandescent.
This invention at once solved the problem of the incandescent system and
was called the subdivision of the electric light. By this means the cost was
materially reduced, and the wiring up and installation of lights materially
simplified.
But the divisibility of the light did not, by any means, solve the great
problem that has occupied the attention of electricians and experimenters

ever since. The great question was and is to preserve the little filament
which is heated to incandescence, and from which we get the light.
The effort of the current to pass through the small filament meets with such
a great resistance that the substance is heated up. If it is made of metal p.there
169

is a point at which it will fuse, and thus the lamp is destroyed.
It was found that carbon, properly treated, would heat to a brilliant white
heat without fusing, or melting, so that this material was employed. But
now followed another difficulty. As this intense heat consumed the particles
of carbon, owing to the presence of oxygen, means were sought to exclude
the air.
This was finally accomplished by making a bulb of glass, from which the
air was exhausted, and as such a globe had no air to support combustion,
the filaments were finally made so that they would last a long time before
being finally disintegrated.
The quest now is, and has been, to find some material of a purely metallic
character, which will have a very high fusing point, and which will,
therefore, dispense with the cost of the exhausted bulb. Some metals, as for
instance, osmium, tantalum, thorium, and others, have been used, and
others, also, with great success, so that the march of improvements is now
going forward with rapid strides.
Vapor Lamps.—One of the directions in which considerable energy has
been directed in the past, was to produce light from vapors. The Cooper
Hewitt mercury vapor lamp is a tube filled with the vapor of mercury, and a
current is sent through the vapor which produces a greenish light,p. 170and
owing to that peculiar color, has not met with much success.
It is merely cited to show that there are other directions than the use of
metallic conductors and filaments which will produce light, and the day is
no doubt close at hand when we may expect some important developments
in the production of light by means of the Hertzian waves.
Directions for Improvements.—Electricity, however, is not a cheap method
of illumination. The enormous heat developed is largely wasted. The quest
of the inventor is to find a means whereby light can be produced without
the generation of the immense heat necessary.

Man has not yet found a means whereby he can make a heat without
increasing the temperature, as nature does it in the glow worm, or in the
firefly. A certain electric energy will produce both light and heat, but it is
found that much more of this energy is used in the heat than in the light.
What wonderful possibilities are in store for the inventor who can make a
heatless light! It is a direction for the exercise of ingenuity that will well
repay any efforts
p. 171
Curious Superstitions Concerning Electricity
Electricity, as exhibited in light, has been the great marvel of all times. The
word electricity itself comes from the thunderbolt of the ancient God Zeus,
which is known to be synonymous with the thunderbolt and the lightning.
Magnetism, which we know to be only another form of electricity, was not
regarded the same as electricity by the ancients. Iron which had the property
to attract, was first found near the town of Magnesia, in Lydia, and for that
reason was called magnetism.
Later on, a glimmer of the truth seemed to dawn on the early scientists,
when they saw the resemblance between the actions of the amber and the
loadstone, as both attracted particles. And here another curious thing
resulted. Amber will attract particles other than metals. The magnet did not;
and from this imperfect observation and understanding, grew a belief that
electricity, or magnetism would attract all substances, even human flesh,
and many devices were made from magnets, and used as cures for the gout,
and to affect the brain, or to remove pain.
Even as early as 2,500 years before the birth of Christ the Chinese knew of
the properties of the magnet, and also discovered that a bar ofp. 172 the
permanent magnet would arrange itself north and south, like the mariners'
compass. There is no evidence, however, that it was used as a mariner's
compass until centuries afterwards.
But the matter connected with light, as an electrical development, which
interests us, is its manifestations to the ancients in the form of lightning.
The electricity of the earth concentrates itself on the tops of mountains, or
in sharp peaks, and accounts for the magnificent electrical displays always
found in mountainous regions.

Some years ago, a noted scientist, Dr. Siemens, while standing on the top of
the great pyramid of Cheops, in Egypt, during a storm, noted that an
electrical discharge flowed from his hand when extended toward the
heavens. The current manifested itself in such a manner that the hissing
noise was plainly perceptible.
The literature of all ages and of all countries shows that this manifestation
of electrical discharges was noted, and became the subject of discussions
among learned men.
All these displays were regarded as the bolts of an angry God, and
historians give many accounts of instances where, in His anger, He sent
down the lightning to destroy.
Among the Romans Jupiter thus hurled forth his wrath; and among many
p. 173
ancient people, even down to the time of Charlemagne, any space struck by
lightning was considered sacred, and made consecrated ground.
From this grew the belief that it was sacrilegious to attempt to imitate the
lightning of the sky—that Deity would visit dire punishment on any man
who attempted to produce an electric light. Virgil relates accounts where
certain princes attempted to imitate the lightning, and were struck by
thunderbolts as punishments.
Less than a century ago Benjamin Franklin devised the lightning rod, in
order to prevent lightning from striking objects. The literature of that day
abounds with instances of protests made, on the part of those who were as
superstitions as the people in ancient times, who urged that it was impious
to attempt to ward off Heaven's lightnings. It was argued that the lightning
was one way in which the Creator manifested His displeasure, and
exercised His power to strike the wicked.
When such writers as Pliny will gravely set forth an explanation of the
causes of lightning, as follows in the paragraph below, we can understand
why it inculcated superstitious fears in the people of ancient times. He says:
"Most men are ignorant of that secret, which, by close observation of the
heavens, deep scholars and principal men of learning have foundp. 174 out,
namely, that they are the fires of the uppermost planets, which, falling to the
earth, are called lightning; but those especially which are seated in the

middle, that is about Jupiter, perhaps because participating in the excessive
cold and moisture from the upper circle of Saturn, and the immoderate heat
of Mars, that is next beneath, by this means he discharges his superfluity,
and therefore it is commonly said, 'That Jupiter shooteth and darteth
lightning.' Therefore, like as out of a burning piece of wood a coal flieth
forth with a crack, even so from a star is spit out, as it were, and voided
forth this celestial fire, carrying with it presages of future things; so that the
heavens showeth divine operations, even in these parcels and portions
which are rejected and cast away as superfluous."

p. 175

CHAPTER XVIIToC
POWER, AND VARIOUS OTHER ELECTRICAL
MANIFESTATIONS

It would be difficult to mention any direction in human activity where
electricity does not serve as an agent in some form or manner. Man has
learned that the Creator gave this great power into the hands of man to use,
and not to curse.
When the dynamo was first developed it did not appear possible that it
could generate electricity, and then use that electricity in order to turn the
dynamo in the opposite direction. It all seems so very natural to us now, that
such a thing should practically follow; but man had to learn this.
Let us try to make the statement plain by a few simple illustrations. By
carefully going over the chapter on the making of the dynamo, it will be
evident that the basis of the generation of the current depends on the
changing of the direction of the flow of an electric current.
Look at the simple horse-shoe magnet. If two of them are gradually moved
toward each other, so that the north pole of one approaches the north pole of
the other, there is a sensible attempt for them to push away from each other.
p. 176
If, however, one of them is turned, so that the north pole of one is opposite
the south pole of the other, they will draw together.
In this we have the foundation physical action of the dynamo and the motor.
When power is applied to an armature, and it moves through a magnetic
field, the action is just the same as in the case of the hand drawing the north
and the south pole of the two approaching magnets from each other.
The influence of the electrical disturbance produced by that act permeated
the entire winding of the field and armature, and extended out on the whole
line with which the dynamo was connected. In this way a current was
established and transmitted, and with proper wires was sent in the form of
circuits and distributed so as to do work.

But an electric current, without suitable mechanism, is of no value. It must
have mechanism to use it, as well as to make it. In the case of light, we have
explained how the arc and the incandescent lamps utilize it for that purpose.
But now, attempting to get something from it in the way of power, means
another piece of mechanism. This is done by the motor, and this motor is
simply a converter, or a device for reversing the action of the electricity.
Attention is called to Figs. 120 and 121. Let us assume that the field
magnets A, A are the positives, and the magnets B, B the negatives.p. 177The
revolving armature has also four magnet coils, two of them, C, C, being
positive, and the other two, D, D, negative, each of these magnet coils being
so connected up that they will reverse the polarities of the magnets.

Figs. 120-121. Action of Magnets in a Dynamo

Now in the particular position of the revolving armature, in Fig. 120, the
magnets of the armature have just passed the respective poles of the field
magnets, and the belt E is compelled to turn the armature past the pole
pieces by force in the direction of the arrow F. After the armature magnets
have gone to the positions in Fig. 121, the positives A try to draw back the
negatives D of the armature, and at the same time the negatives B repel the
negatives D, because they are of the same polarities
This repulsion of the negatives A, B continues until the armature polesp.C,
178
D
have slightly passed them, when the polarities of the magnets C, D are
changed; so that it will be seen, by reference to Fig. 122, that D is now
retreating from B, and C is going away from A—that is, being forced away
contrary to their natural attractive influences, and in Fig. 123, when the

complete cycle is nearly finished, the positives are again approaching each
other and the negatives moving together.

Figs. 122-123. Cycle Action in Dynamo

In this manner, at every point, the sets of magnets are compelled to move
against their magnetic pull. This explains the dynamo.
Now take up the cycle of the motor, and note in Fig. 124 that the negative
magnets D of the armature are closely approaching the positive and
p. 179
negative magnets, on one side; and the positive magnets C are nearing the
positive and negatives on the other side. The positives A, therefore, attract
the negatives D, and the negative B exert a pull on the positives C at the
same time. The result is that the armature is caused to revolve, as shown by
the dart G, in a direction opposite to the dart in Fig. 120.

Figs. 124-125. Action of Magnets in Motor

When the pole pieces of the magnets C, D are about to pass magnets A, B,
as shown in Fig. 125, it is necessary to change the polarities of the armature

magnets C, D; so that by reference to Fig. 126, it will be seen that they are
now indicated as C-, and D+, respectively, and have moved to a point
midway between the poles A, B (as in Fig. 125), where the pull on one side,
p. 180
and the push on the other are again the same, and the last Figure 127 shows
the cycle nearly completed.
The shaft of the motor armature is now the element which turns the
mechanism which is to be operated. To convert electrical impulses into
power, as thus shown, results in great loss. The first step is to take the steam
boiler, which is the first stage in that source which is the most common and
universal, and by means of fuel, converting water into steam. The second is
to use the pressure of this steam to drive an engine; the third is to drive the
dynamo which generates the electrical impulse; and the fourth is the
conversion from the dynamo into a motor shaft. Loss is met with at each
step, and the great problem is to eliminate this waste.

Figs. 126-127. Positions of Magnets in Motor

The great advantage of electrical power is not in utilizing itp. 181for
consumption at close ranges, but where it is desired to transmit it for long
distances. Such illustrations may be found in electric railways, and where
water power can be obtained as the primal source of energy, the cost is not
excessive. It is found, however, that even with the most improved forms of
mechanism, in electrical construction, the internal combustion engines are
far more economical.
Transmission of Energy

One of the great problems has been the transmission of the current to great
distances. By using a high voltage it may be sent hundreds of miles, but to
use a current of that character in the cars, or shops, or homes, would be
exceedingly dangerous.
To meet this requirement transformers have been devised, which will take a
current of very high voltage, and deliver a current of low tension, and
capable of being used anywhere with the ordinary motors.
The Transformer.—This is an electrical device made up of a core or cores
of thin sheet metal, around which is wound sets of insulated wires, one set
being designed to receive the high voltage, and the other set to put out the
low voltage, as described in a former chapter
These may be made where the original output is a very high voltage, sop. 182
that
they will be stepped down, first from one voltage to a lower, and then from
that to the next lower stage. This is called the "Step down" transformer, and
is now used over the entire world, where large voltages are generated.
Electric Furnaces.—The most important development of electricity in the
direction of heat is its use in furnaces. As before stated, an intense heat is
capable of being generated by the electric current, so that it becomes the
great agent to use for the treatment of refractory material.
In furnaces of this kind the electric arc is the mechanical form used to
produce the great heat, the only difference being in the size of the
apparatus. The electric furnace is simply an immense form of arc light,
capable of taking a high voltage, and such an arc is enclosed within a
suitable oven of refractory material, which still further conserves the heat.
Welding By Electricity.—The next step is to use the high heat thus
capable of being produced, to fuse metals so that they may be welded
together. It is a difficult matter to unite two large pieces of metal by the
forging method, because the highest heat is required, owing to their bulk,
and in addition immense hammers, weighing tons, must be employed. p. 183
Electric welding offers a simple and easy method of accomplishing the
result, and in the doing of which it avoids the oxidizing action of the
forging heat. Instead of heating the pieces to be welded in a forge, as is now
done, the ends to be united are simply brought into contact, and the current

is sent through the ends until they are in a soft condition, after which the
parts are pressed together and united by the simple merging of the plastic
condition in which they are reduced by the high electric heat.
This form of welding makes the most perfect joint, and requires no
hammering, as the mass of the metal flows from one part or end to the
other; the unity is a perfect one, and the advantage is that the metals can be
kept in a semi-fluid state for a considerable time, thus assuring a perfect
admixture of the two parts.
With the ordinary form of welding it is necessary to drive the heated parts
together without any delay, and at the least cooling must be reheated, or the
joint will not be perfect.
The smallest kinds of electric heating apparatus are now being made, so that
small articles, sheet metal, small rods, and like parts can be united with the
greatest facility.

p. 184

CHAPTER XVIIIToC
X-RAY, RADIUM, AND THE LIKE

The camera sees things invisible to the human eye. Its most effective work
is done with beams which are beyond human perception. The photographer
uses the Actinic rays. Ordinary light is composed of the seven primary
colors, of which the lowest in the scale is the red, and the highest to violet.
Those below the red are called the Infra-red, and they are the Hertzian
waves, or those used in wireless telegraphy. Those above the violet are
called Ultra-violet, and these are employed for X-ray work. The former are
produced by the high tension electric apparatus, which we have described in
the chapter relating to wireless telegraphy; and the latter, called also the
Roentgen rays, are generated by the Crookes' Tube.
This is a tube from which all the atmosphere has been extracted so that it is
a practical vacuum. Within this are placed electrodes so as to divert the
action of the electrical discharge in a particular direction, and this light,
when discharged, is of such a peculiar character that its discovery made a
sensation in the scientific world
The reason for this great wonder was not in the fact that it projected a p.light,
185

but because of its character. Ordinary light, as we see it with the eye, is
capable of being reflected, as when we look into a mirror at an angle. The
X-ray will not reflect, but instead, pass directly through the glass.
Then, ordinary light is capable of refraction. This is shown by a ray of light
bending as it passes through a glass of water, which is noticed when the
light is at an angle to the surface.
The X-ray will pass through the water without being changed from a
straight line. The foregoing being the case, it was but a simple step to
conclude that if it were possible to find a means whereby the human eye
could see within the ultra-violet beam, it would be possible to see through
opaque substances.

From the discovery so important and far reaching it was not long until it
was found that if the ultra-violet rays, thus propagated, were transmitted
through certain substances, their rates of vibration would be brought down
to the speeds which send forth the visible rays, and now the eye is able to
see, in a measure at least, what the actinic rays show.
This discovery was but the forerunner of a still more important
development, namely, the discovery of radium. The actual finding of the
p. 186
metal was preceded by the knowledge that certain minerals, and water, as
well, possessed the property of radio-activity.
Radio-activity is a word used to express that quality in metals or other
material by means of which obscure rays are emitted, that have the capacity
of discharging electrified bodies, and the power to ionize gases, as well as
to actually affect photograph plates.
Certain metals had this property to a remarkable degree, particularly
uranium, thorium, polonium, actinium, and others, and in 1898 the Curies,
husband and wife, French chemists, isolated an element, very ductile in its
character, which was a white metal, and had a most brilliant luster.
Pitchblende, the base metal from which this was extracted, was discovered
to be highly radio-active, and on making tests of the product taken from it,
they were surprised to find that it emitted a form of energy that far exceeded
in calculations any computations made on the basis of radio-activity in the
metals hitherto examined.
But this was not the most remarkable part of the developments. The energy,
whatever it was, had the power to change many other substances if brought
into close proximity. It darkens the color of diamonds, quartz, mica, and
p. 187
glass. It changes some of the latter in color, some kinds being turned to
brown and others into violet or purple tinges.
Radium has the capacity to redden the skin, and affect the flesh of persons,
even at some considerable distance, and it is a most powerful germicide,
destroying bacteria, and has been found also to produce some remarkable
cures in diseases of a cancerous nature.
The remarkable similarity of the rays propagated by this substance, with the
X-rays, lead many to believe that they are electrical in their character, and

the whole scientific world is now striving to use this substance, as well as
the more familiar light waves of the Roentgen tube, in the healing of
diseases.
It is not at all remarkable that this use of it should first be considered, as it
has been the history of the electrical developments, from the earliest times,
that each successive stage should find advocates who would urge its virtues
to heal the sick.
It was so when the dynamo was invented, when the high tension current
was produced; and electrical therapeutics became a leading theme when
transmission by induction became recognized as a scientific fact.
It is not many years since the X-rays were discovered, and thep. first
188

announcement was concerning its wonderful healing powers.
This was particularly true in the case of radium, but for some reason, after
the first tests, all experimenters were thwarted in their theories, because the
science, like all others, required infinite patience and experience. It was
discovered, in the case of the X-ray, that it must be used in a modified form,
and accordingly, various modifications of the waves were introduced, called
the m and the n rays, as well as many others, each having some peculiar
qualification.
In time, no doubt, the investigators will find the right quality for each
disease, and learn how to apply it. Thus, electricity, that most alluring thing
which, in itself, cannot be seen, and is of such a character that it cannot
even be defined in terms which will suit the exact scientific mind, is daily
bringing new wonders for our investigation and use.
It is, indeed, a study which is so broad that it has no limitations, and a field
which never will be exhausted.
THE END

p. 189

GLOSSARY OF WORDS USED IN TEXT OF THIS
VOLUMEToC
Acid. Accumulator material is sulphuric acid, diluted with
water.
Active Material. That part of the material in accumulator plates which is
acted upon by the electric current.
Accumulator. A cell, generally known as a storage battery, which while
it initially receives a charge of electricity, is nevertheless,
of such a character, owing to the active material of which
it is made, that it accumulates, or, as it were, generates
electricity.
Aerial Wire, or The wire which, in wireless telegraphy, is carried up into
Conductor. the air to connect the antennæ with the receiving and
sending apparatus.
Alarm, Burglar. A circulating system in a building, connected up with a
bell or other signaling means.
Alloy. A mixture of two or more metals; as copper and zinc to
make brass; nickel and zinc to form German silver.
Alternating A current which goes back and forth in opposite
Current. directions, unlike a direct current which flows
continuously in one direction over a wire.
Alternation. The term applied to a change in the direction of an
alternating current, the frequency of the alternations
ranging up to 20,000 or more vibrations per second.
Amber. A resin, yellow in color, which when rubbed with a cloth,
becomes excited and gives forth negative electricity. p. 190
Ammeter. An instrument for measuring the quantity or flow of
electricity.
Ampere. The unit of current; the term in which strength of the
current is measured. An ampere is an electromotive force
of one volt through a resistance of one ohm.
Annunciator. A device which indicates or signals a call given from
some distant point.
Anode. The positive terminal in a conducting circuit, like the
terminal of the carbon plate in a battery. It is a plate in an
electroplating bath from which the current goes over to
the cathode or negative plate or terminal.
Arc. A term employed to designate the gap, or the current
which flows across between the conductors, like the space
between the two carbons of an arc lamp, which gives the
light.
Armature. A body of iron, or other suitable metal, which is in the
magnetic field of a magnet.
Armature Bar. The piece which holds the armature. Also one of a series
of bars which form the conductors in armature windings.

Armature Coil. The winding around an armature, or around the core of an
armature.
Armature Core. The part in a dynamo or motor which revolves, and on
which the wire coils are wound.
Astatic That which has no magnetic action to direct or divert
(Galvanometer). anything exterior to it.
Atom. The ultimate particle of an elementary substance.
Attraction. That property of matter which causes particles to adhere,
or cohere, to each other. It is known under a variety of p. 191
terms, such as gravitation, chemical affinity, electro-
magnetism and dynamic attraction.
Automatic Cut- A device which acts through the operation of the
out. mechanism with which it is connected. It is usually
applied to a device which cuts out a current when it
overcharges or overloads the wire.
Bath. In electroplating, the vessel or tank which holds the
electroplating solution.
Battery. A combination of two or more cells.
Battery, Dry. A primary battery in which the electrolyte is made in a
solid form.
Battery, A battery which is better known by the name of the
Galvanic. Voltaic Pile, made up of zinc and copper plates which
alternate, and with a layer of acidulated paper between
each pair of plates.
Battery, Storage. A battery which accumulates electricity generated by a
primary battery or a generator.
Brush. A term applied to the conducting medium that bears
against the cylindrical surface of a commutator.
Buzzer. An electric call produced by a rapidly moving armature of
an electro-magnet.
Cable. A number of wires or conductors assembled in one strand.
Candle-power. The amount of light given by the legal-standard candle.
This standard is a sperm candle, which burns two grains a
minute.
Capacity. The carrying power of a wire or circuit, without heating.
When heated there is an overload, or the capacity of the
wire is overtaxed.
Capacity, The quantity of electricity in a secondary battery when
Storage. fully charged, usually reckoned in ampere hours. p. 192
Carbon. A material, like coke, ground or crushed, and formed into
sticks or plates by molding or compression. It requires a
high heat to melt or burn, and is used as electrodes for arc
lamps and for battery elements. It has poor conductivity,
and for arc lamps is coated with copper to increase its
conductivity.
Cell, Electrolytic. A vessel containing an electrolyte for electroplating
purposes.

Charge. The quantity of electricity on the surface of a body or
conductor.
Chemical When a current passes through electrodes in a solution, a
Change. change takes place which is chemical in its character.
Adding sulphuric acid to water produces heat. If
electrodes of opposite polarity are placed in such an acid
solution, a chemical change is produced, which is
transformed into electricity.
Choking Coil. An instrument in a circuit which by a form of resistance
regulates the flow of the current, or returns part of it to
the source of its generation.
Counter- Cells which are inserted in opposition to a battery to
electromotive reduce high voltage.
Force.
Circuit, Astatic. A circuit in an instrument so wound that the earth's
magnetism will not affect it.
Circuit Breaker. Any instrument in a circuit which cuts out or interrupts
the flow of a current.
Circuit, External. A current flows through a wire or conductor, and also
along the air outside of the conductor, the latter being the
external circuit.
Circuit Indicator. An instrument, like a galvanometer, that shows the
direction in which a current is flowing through a p. 193
conductor.
Circuit, Return. Usually the ground return, or the negative wire from a
battery.
Circuit, Short. Any connection between the mains or parallel lines of a
circuit which does not go through the apparatus for which
the circuit is intended.
Coherer. A tube, or other structure, containing normally high
resistance particles which form a path or bridge between
the opposite terminals of a circuit.
Coil. A wire, usually insulated, wound around a spool.
Coil, Induction. One of a pair of coils designed to change the voltage of a
current of electricity, from a higher to a lower, or from a
lower to a higher electro-motive force.
Coil, Resistance. A coil so wound that it will offer a resistance to a steady
current, or reduce the flow of electricity.
Commutator. A cylinder on the end of the armature of a dynamo or
motor and provided with a pair of contact plates for each
particular coil in the armature, in order to change the
direction of the current.
Compass. An apparatus which indicates the direction or flow of the
earth's magnetism.
Condenser. A device for storing up electro-static charges.
Conductance. That quality of a conductor to carry a current of
electricity, dependent on its shape for the best results.

Conduction. The transmission of a current through a rod, wire or
conductor.
Conductivity. That quality which has reference to the capacity to
conduct a current.
Conductor. Any body, such as a bar, rod, wire, or machine, which
will carry a current.
Connector. A binding post, clamp, screw, or other means to hold the p. 194
end of a wire, or electric conductor.
Contact. To unite any parts in an electric circuit.
Controller. The handle of a switchboard, or other contact making and
breaking means in a circuit.
Converter. An induction coil in an alternating circuit for changing
potential difference, such as high alternating voltage into
low direct current voltage.
Convolution. To wind like a clock spring.
Core. The inner portion of an electro-magnet. The inside part of
an armature wound with wire.
Core, Laminated. When the core is built up of a number of separate pieces
of the same material, but not insulated from each other.
Coulomb. The unit of electrical quantity. It is the quantity passed by
a current of one ampere intensity in one second of time.
Couple, Electric. Two or more electrodes in a liquid to produce an electric
force.
Current, A natural current produced by the action of electro-
Alternating. magnets. It is a succession of short impulses in opposite
directions.
Current, A current which is uniformly maintained in a steady
Constant. stream.
Current, Induced. A current produced by electro-dynamic induction.
Current Meter. An apparatus for indicating the strength of a current. An
ammeter.
Current, A current which periodically alternates.
Oscillating.
Current, A periodically varying current strength.
Periodic.
Current, A current which has a constant direction, but has a p. 195
Undulating. continuously varying strength.
Decomposition. The separation of a liquid, such as an electrolyte, into its
prime elements, either electrically or otherwise.
Deflection. The change of movement of a magnetic needle out of its
regular direction of movement.
Demagnetization. When a current passes through a coil wound on an iron
core, the core becomes magnetized. When the current
ceases the core is no longer a magnet. It is then said to be
demagnetized. It also has reference to the process for
making a watch non-magnetic so that it will not be
affected when in a magnetic field.

Density. The quantity of an electric charge in a conductor or
substance.
Depolarization. The removal of magnetism from a permanent magnet, or
a horse-shoe magnet, for instance. It is generally
accomplished by applying heat.
Deposition, The act of carrying metal from one pole of a cell to
Electrolysis. another pole, as in electroplating.
Detector. Mechanism for indicating the presence of a current in a
circuit.
Diaphragm. A plate in a telephone, which, in the receiver, is in the
magnetic field of a magnet, and in a transmitter carries
the light contact points.
Dielectric. A non-conductor for an electric current, but through
which electro-static induction will take place. For
example: glass and rubber are dielectrics.
Discharge. The current flowing from an accumulator.
Disintegration. The breaking up of the plate or active material.
Disruptive. A static discharge passing through a dielectric.
Duplex Wire. A pair of wires usually twisted together and insulated
from each other to form the conducting circuit of a p. 196
system.
Dynamic The term applied to a current flowing through a wire.
Electricity.
Dynamo. An apparatus, consisting of core and field magnets,
which, when the core is turned, will develop a current of
electricity.
Earth Returns. Instead of using two wires to carry a circuit, the earth is
used for what is called the return circuit.
Efficiency. The total electrical energy produced, in which that
wasted, as well as that used, is calculated.
Elasticity. That property of any matter which, after a stress, will
cause the substance to return to its original form or
condition. Electricity has elasticity, which is utilized in
condensers, as an instance.
Electricity, Lightning, and, in short, any current or electrical impulse,
Atmospheric. like wireless telegraphic waves, is called atmospheric.
Electricity, Electricity with a low potentiality and large current
Voltaic. density.
Electrification. The process of imparting a charge of electricity to any
body.
Electro- The study of which treats of electric and chemical forces,
chemistry. such as electric plating, electric fusing, electrolysis, and
the like.
Electrode. The terminals of a battery, or of any circuit; as, for
instance, an arc light.
Electrolyte. Any material which is capable of being decomposed by
an electric current.

Electro- Magnetism which is created by an electric current.
magnetism.
Electrometer. An instrument for measuring static electricity, differing
from a galvanometer, which measures a current in a wire
that acts on the magnetic needle of the galvanometer. p. 197
Electro-motive (E. M. F.) Voltage, which is the measure or unit of e. m. f.
Force.
Electroscope. A device for indicating not only the presence of
electricity, but whether it is positive or negative.
Electro-static Surfaces separated by a dielectric for opposite charging of
Accumulator. the surface.
Element. In electricity a form of matter, as, for instance, gold, or
silver, that has no other matter or compound. Original
elements cannot be separated, because they are not made
up of two or more elements, like brass, for instance.
Excessive A storage battery charged at too high a rate.
Charge.
Excessive A storage battery discharged at too high a rate.
Discharge.
Excessive Charging for too long a time.
Overcharge.
Exciter. A generator, either a dynamo or a battery, for exciting the
field of a dynamo.
Exhaustive An excessive over-discharge of an accumulator.
Discharge.
F. The sign used to indicate the heat term Fahrenheit.
Fall of Voltage. The difference between the initial and the final voltage in
a current.
Field. The space or region near a magnet or charged wire. Also
the electro-magnets in a dynamo or motor.
Flow. The volume of a current going through a conductor.
Force, Electro- The pull developed by an electro-magnet.
magnetic.
Frictional A current produced by rubbing dissimilar substances
Electricity. together.
Full Load. The greatest load a battery, accumulator or dynamo will p. 198
sustain.
Galvanic. Pertaining to the electro-chemical relations of metals
toward each other.
Galvanizing. The art of coating one metal with another, such, for
instance, as immersing iron in molten zinc.
Galvanometry. An instrument having a permanently magnetized needle,
which is influenced by a coil or a wire in close proximity
to it.
Galvanoscope. An instrument, like a galvanometer, which determines
whether or not a current is present in a tested wire.
Generator. A term used to generally indicate any device which
originates a current.

German Silver. An alloy of copper, nickel and zinc.
Graphite. One form of carbon. It is made artificially by the electric
current.
Grid. The metallic frame of a plate used to hold the active
material of an accumulator.
Gravity. The attraction of mass for mass. Weight. The accelerating
tendency of material to move toward the earth.
Gutta Percha. Caoutchouc, which has been treated with sulphur, to
harden it. It is produced from the sap of tropical trees, and
is a good insulator.
Harmonic A vibrating reed acted on by an electro-magnet, when
Receiver. tuned to its pitch.
High E. M. F. A term to indicate currents which have a high voltage,
and usually low amperage.
Igniter. Mechanism composed of a battery, induction coil and a
vibrator, for making a jump spark, to ignite gas, powder,
etc.
I. H. P. Abbreviation, which means Indicated Horse Power.
Impulse. A sudden motion of one body acting against another. An p. 199
electro-magnetic wave magnetizing soft iron, and this
iron attracting another piece of iron, as an example.
Incandescence, A conductor heated up by a current so it will glow.
Electric.
Induced Current. A current of electricity which sets up lines of force at
right angles to the body of the wire through which the
current is transmitted.
Induction, A body within a magnetic field which is excited by the
Magnetic. magnetism.
Installation. Everything belonging to an equipment of a building, or a
circuiting system to do a certain thing.
Insulation. A material or substance which resists the passage of a
current placed around a conductor.
Intensity. The strength of a magnetic field, or of a current flowing
over a wire.
Internal The current strength of electricity of a wire to resist the
Resistance. passage.
Interrupter. A device in a wire or circuit for checking a current. It also
refers to the vibrator of an induction coil.
Joint. The place where two or more conductors are united.
Joint Resistance. The combined resistance offered by two or more
substances or conductors.
Jump Spark. A spark, disruptive in its character, between two
conducting points.
Initial Charge. The charge required to start a battery.
Kathode, or The negative plate or side of a battery. The plate on which
Cathode. the electro deposit is made.
Key. The arm of a telegraph sounder. A bar with a finger piece,
which is hinged and so arranged that it will make and

break contacts in an electric circuit.
Keyboard. A switch-board; a board on which is mounted a number p. 200
of switches.
Kilowatt. A unit, representing 1,000 watts. An electric current
measure, usually expressed thus: K.W.
Kilowatt Hour. The computation of work equal to the exertion of one
kilowatt in one hour.
Knife Switch. A bar of a blade-like form, adapted to move down
between two fingers, and thus establish metallic
connections.
Laminated. Made up of thin plates of the same material, laid together,
but not insulated from each other.
Lamp Arc. A voltaic arc lamp, using carbon electrodes, with
mechanism for feeding the electrodes regularly.
Lamp, A lamp with a filament heated up to a glow by the action
Incandescent. of an electric current. The filament is within a vacuum in
a glass globe.
Leak. Loss of electrical energy through a fault in wiring, or in
using bare wires.
Load. The ampere current delivered by a dynamo under certain
conditions.
Low Frequency. A current in which the vibrations are of few alternations
per second.
Magnet. A metallic substance which has power to attract iron and
steel.
Magnet Bar. A straight piece of metal.
Magnet Coil. A coil of wire, insulated, surrounding a core of iron, to
receive a current of electricity.
Magnet Core. A bar of iron adapted to receive a winding of wire.
Magnet, Field. A magnet in a dynamo. A motor to produce electric
energy.
Magnet, A short steel form, to hold magnetism for a long time.
Permanent.
Magnetic The adherence of particles to the poles of a magnet. p. 201
Adherence.
Magnetic That quality of a metal which draws metals. Also the
Attraction and pulling action of unlike poles for each other, and pushing
Repulsion. away of like poles when brought together.
Magnetic Force. The action exercised by a magnet of attracting or
repelling.
Magnetic Pole. The earth has North and South magnetic poles. The south
pole of a magnetic needle is attracted so it points to the
north magnetic pole; and the north pole of the needle is
attracted to point to the south magnetic pole.
Magneto- A permanent magnet and a revolving armature for
generator. generating a current.
Maximum The final voltage after charging.
Voltage.

Molecule. Invisible particles made up of two or more atoms of
different matter. An atom is a particle of one substance
only.
Morse Sounder. An electric instrument designed to make a clicking sound,
when the armature is drawn down by a magnet.
Motor-dynamo. A motor and a dynamo having their armatures connected
together, whereby the motor is driven by the dynamo, so
as to change the current into a different voltage and
amperage.
Motor- A motor which delivers the current like a generator.
transformer.
Needle. A bar magnet horizontally poised on a vertical pivot
point, like the needle of a mariner's compass.
Negative Amber, when rubbed, produces negative electricity. A p. 202
Electricity. battery has positive as well as negative electricity.
Negative That plate in the solution of a battery cell which is not
Element. disintegrated.
Normal. The usual, or ordinary. The average. In a current the
regular force required to do the work.
North Pole, The term applied to the force located near the north pole
Electric. of the globe, to which a permanent magnet will point if
allowed to swing freely.
O. Abbreviation for Ohm.
Ohm. The unit of resistance. Equal to the resistance of a column
of mercury one square millimeter in cross section, and
106.24 centimeters in length.
Ohm's Law. It is expressed as follows:

1. The current strength is equal to the electro-motive
force divided by its resistance.
2. The electro-motive force is equal to the current
strength multiplied by the resistance.
3. The resistance is equal to the electro-motive force
divided by the current strength.

Overload. In a motor an excess of mechanical work which causes
the armature to turn too slowly and produces heat.
Phase. One complete oscillation. The special form of a wave at
any instant, or at any interval of time.
Plate, Condenser. In a static machine it is usually a plate of glass and
revoluble.
Plate, Negative. The plate in a battery, such as carbon, copper or platinum,
which is not attacked by the solution.
Plating, Electro-. The method of coating one metal with another by
electrolysis.
Polarity. The peculiarity, in a body, of arranging itself with
reference to magnetic influence.

Parallel. When a number of cells are coupled so that their similar p. 203
poles are grouped together. That is to say, as the carbon
plates, for instance, are connected with one terminal, and
all the zinc plates with the other terminal.
Polarization. When the cell is deprived of its electro-motive force, or
any part of it, polarization is the result. It is usually
caused by coating of the plates.
Porosity. Having small interstices or holes.
Positive Current. One which deflects a needle to the left.
Positive Any current flowing from the active element, such as
Electricity. zinc, in a battery. The negative electricity flows from the
carbon to the zinc.
Potential, The power which performs work in a circuit.
Electric.
Potential Energy. That form of force, which, when liberated, does or
performs work.
Power Unit. The volt-amperes or watt.
Primary. The induction coil in induction machines, or in a
transformer.
Push Button. A thumb piece which serves as a switch to close a circuit
while being pressed inwardly.
Quantity. Such arrangement of electrical connections which give
off the largest amount of current.
Receiver. An instrument in telephony and telegraphy which
receives or takes in the sound or impulses.
Relay. The device which opens or closes a circuit so as to admit
a new current which is sent to a more distant point.
Repulsion, That tendency in bodies to repel each other when
Electric. similarly charged.
Resilience. The springing back to its former condition or position. p. 204
Electricity has resilience.
Resistance. The quality in all conductors to oppose the passage of a
current.
Resistance Coil. A coil made up of wire which prevents the passage of a
current to a greater or less degree.
Resistance, The counter force in an electrolyte which seeks to prevent
Electrolytic. a decomposing current to pass through it.
Resistance: The opposing force to the movement of a current which is
Internal, in the cell or generator. This is called the internal. That
External. opposite action outside of the cell or generator is the
external.
Resonator, An open-circuited conductor for electrically resounding
Electric. or giving back a vibration, usually exhibited by means of
a spark.
Rheostat. A device which has an adjustable resistance, so arranged
that while adjusting the same the circuit will not be open.
Safety Fuse. A piece of fusible metal of such resistance that it breaks
down at a certain current strength.

Saturated. When a liquid has taken up a soluble material to the
fullest extent it is then completely saturated.
Secondary. One of the two coils in a transformer, or induction coil.
Secondary The brown or deep red plates in a storage battery when
Plates. charged.
Self-excited. Producing electricity by its own current.
Series. Arranged in regular order. From one to the other directly.
If lamps, for instance, should be arranged in circuit on a
single wire, they would be in series.
Series, Multiple. When lamps are grouped in sets in parallel, and these sets p. 205
are then connected up in series.
Series Windings. A generator or motor wound in such a manner that one of
the commutator brush connections is joined to the field
magnet winding, and the other end of the magnet winding
joined to the outer circuit.
Shunt. Going around.
Shunt Winding. A dynamo in which the field winding is parallel with the
winding of the armature.
Snap Switch. A switch so arranged that it will quickly make a break.
Sounder. The apparatus at one end of a line actuated by a key at the
other end of the line.
Spark Coil. A coil, to make a spark from a low electro-motive force.
Spark, Electric. The flash caused by drawing apart the ends of a
conductor.
Specific Gravity. The weight or density of a body.
Static Electricity. Generated by friction. Also lightning. Any current
generated by a high electro-motive force.
Strength of The quantity of electricity in a circuit.
Current.
Synchronize. Operating together; acting in unison.
Terminal. The end of any electric circuit or of a body or machine
which has a current passing through it.
Thermostat, An electric thermometer. Usually made with a metal coil
Electric. which expands through the action of the electricity
passing through it, and, in expanding, it makes a contact
and closes a circuit.
Transformer. The induction coil with a high initial E. M. F. changes
into a low electro-motive force.
Unit. A standard of light, heat, electricity, or of other p. 206
phenomena.
Vacuum. A space from which all matter has been exhausted.
Vibrator. Mechanism for making and breaking circuits in induction
coils or other apparatus.
Volt. The unit of electro-motive force.
Voltage. Electro-motive force which is expressed in volts.
Voltaic. A term applied to electric currents and devices.

Volt-meter. An apparatus for showing the difference of potential, or
E. M. F. in the term of volts.
Watt. The unit of electrical activity. The product of amperes
multiplied by volts.
Watt Hour. One watt maintained through one hour of time.
Waves, Electric Waves in the ether caused by electro-magnetic
Magnetic. disturbances.
X-rays. The radiation of invisible rays of light, which penetrate or
pass through opaque substances.
Yoke, or Bar. A soft iron body across the ends of a horseshoe magnet,
to enable the magnet to retain its magnetism an indefinite
time.
Zinc Battery. A battery which uses zinc for one of its elements.

p. 207

INDEXToC

A Alternating periods, 149.
Alternations, 147.
Accumulated, 31. Aluminum, 128, 129, 135,
Accumulation, 29. 137.
Accumulator cell, 87. Aluminum hydrate, 129.
Accumulators, 82, 88, 89. Amber, 5, 171.
Accumulators, plates, 83. Ammeter, 7, 88.
Acid, 34, 37, 125. Amperage, 38, 61, 62, 132,
159, 160, 168.
Acid maker, 125.
Ampere, 7, 37, 60, 63, 139,
Acid, sulphuric, 31, 84.
140, 167.
Acidulated, 55.
Amplitude, 111.
Acidulated water, 34.
Annunciator, 65, 74, 76, 79,
Acoustics, 110.
80, 81.
Actinic rays, 184, 185.
Annunciator bells, 11.
Actinium, 186.
Anode, 35, 133, 134.
Active element, 82.
Antennæ, 108.
Adjustable rod, 107.
Antimony 137, 143.
Adjusting screw, 70, 71, 72,
Anvil, 13, 14.
73, 106.
Apparatus, 11, 57, 106, 139,
Aerial wire, 108.
145.
Agents, 13, 32.
Arc, 163, 182.
Alarms, burglar, 11, 76, 80.
Arc lighting, 38, 165.
Alkali, 125.
Arc system, 166.
Alkaline, 37.
Armature, 18, 25, 38, 40, 42,
Alternate, 127. 43, 45, 46, 47, 48, 53, 55, 70,
Alternating, 38, 149, 150, 153, 72, 73, 74, 90, 93, 112, 151,
154, 155, 156. 152, 155, 163, 176, 177, 178,
Alternating current, 145. 179, 180.

p. 208
Armature brush, 48. Bearings, 45, 46.
Armature post, 71. Bells, 65, 73, 76, 122.
Armature, vertical, 75. Bells, electric, 70.
Armature winding, 42, 43, Bench, 13, 15, 17.
156. Binding post, 52, 70, 71, 72,
Asbestos, 140. 103, 107, 108, 121.
Astatic galvanometer, 108. Binding screw, 65, 66.
Atmosphere, 184. Bismuth, 18, 143.

Attract, 30. Bit, 13.
Attracted, 72. Blue vitriol, 57.
Attraction, 21, 25. Brass plate, 77, 78.
Attractive, 178. Brazing, 17, 65.
Automatic, 120. Bridge, 52.
Auxiliary, 44. Brush holder, 46.
Awls, 14. Brushes, 48, 150, 151, 153,
167.
B Burglar, 11.
Burglar alarm, 76, 80.
Bacteria, 126, 187. Buttons, contact, 80.
Bar, cross, 66. Buttons, push, 65, 68, 69, 70,
Bar, horizontal, 46. 76, 79.
Bar, parallel switch, 67.
Bar, switch, 65, 68. C
Base block, 66.
Batteries, 11, 93, 122. Calorimeter, 56.
Battery, 29, 30, 32, 35, 36, 46, Cancerous, 187.
47, 80, 81, 82, 83, 85, 86, 88, Candle power, 89, 139.
92, 94, 95, 107, 108, 116, 117, Cap, removable, 73.
118, 121, 134, 142. Cap screws, 42.
Battery charging, 82. Carbon, 35, 119, 121, 162,
163, 169.
Carbon block, 120.

p. 209
Carbon pencil, 119. Coils, induction, 99, 102.
Cathode, 35, 36, 133, 134. Coils, primary, 109.
Cell, 29, 33. Coils, secondary, 102, 109.
Cell, accumulator, 87. Coincide, 42.
Cell, charging, 87. Cold, 14.
Channel, 43. Collecting surfaces, 30.
Channel, concave, 40. Collector, 31.
Charged, 120. Column, 61.
Charged battery, 82. Combustion, 169.
Charging circuit, 82, 89. Commutator, 44, 46, 151, 152.
Charging source, 83. Commutator brushes, 46.
Charged wire, 147. Commutator plates, 45.
Chemical, 57. Compass, 22, 24, 172.
Chisels, 13. Composition, 83, 124.
Chloride of lime, 84. Compound wound, 47.
Choked, 157. Concave channel, 40.
Choking coils, 145, 146, 156, Condenser, 98, 100, 101, 102,
158. 108.
Circuit, 33, 69, 73, 76, 78, 80, Conduct, 6, 108.
81, 90, 92, 93, 109, 113, 116,

121, 122, 131, 134, 143, 156. Conduction, 135, 136, 138,
Circuit, primary, 99. 166, 170.
Circuit, secondary, 99. Conduction current, 27.
Circuiting, 81, 155. Conductor, 21, 31, 33, 63, 98,
Circuiting system, 79. 116, 161, 162.
Clapper arm, 70. Conduit, 72.
Closed rings, 26. Conically formed, 126.
Coherer, 105, 108, 109. Conjunction, 143.
Cohering, 106. Connecting wire, 58.
Coils, 18, 26, 52, 55, 74, 160. Connection, 72, 76.
Coils, choking, 145, 146, 156, Construction, magnet, 39.
158. Consumption, 180.

p. 210
Contact, 122, 123, 152, 162. Current changing, 82.
Contact finger, 150. Current conduction, 27.
Contact plate, 67, 68, 79. Current, continuous, 164.
Contact screws, 93. Current, direct, 145, 150.
Contact surface, 66. Current direction, 50.
Continuous, 145. Current, exterior, 50, 150.
Converter, 176. Current, reversing, 148.
Converting, 142, 145, 146. Current strength, 7, 57.
Copper, 18, 34, 36, 65, 66, Current testing, 143.
132, 133, 134, 135, 136, 137, Cut-out, 120.
142, 143. Cutter, 14.
Copper cyanide, 133. Cutting, lines of force, 38.
Copper plate, 33, 35, 58, 67. Cylinder, 44.
Copper sulphate, 57. Cylindrical, 43.
Copper voltameter, 55, 57.
Core, 27, 28, 36, 39, 40, 115. D
Core, magnet, 75, 93.
Counter, clock-wise, 51. Dash, 95, 97.
Coupled, 36. Decoherer, 106, 108.
Crank, 30. Decomposed, 57, 128.
Crookes' tube, 184. Decomposes, 55.
Cross bar, 52, 66. Decomposing, 123.
Crown of cups, 32. Decomposition, 12, 35, 82.
Crystal, 85. Deflected, 54.
Current, 6, 7, 13, 18, 26, 27, Degree, 135, 162.
28, 35, 36, 37, 38, 47, 50, 51, Demagnetized, 24, 72.
52, 55, 56, 57, 58, 59, 62, 63, Deposited, 58, 133.
70, 72, 73, 90, 95, 98, 105,
108, 116, 133, 134, 135, 136,
138, 139, 140, 141, 142, 143,
147, 148, 149, 150, 152, 153,

157, 160, 161, 163, 165, 166,
170.
Current, alternating, 150.

p. 211
Depression, 15, 140. Dynamo, 7, 27, 38, 42, 46, 48,
Detecting current, 49. 62, 82, 83, 87, 89, 132, 141,
Detector, 49, 52, 54, 105. 142, 145, 150, 155, 161, 165,
Devices, measuring, 27. 167, 175, 176, 180, 187.
Diagrams, 46, 48, 79, 89. Dynamo fields, 40, 41.
Diagrammatically, 81.
Diamagnetic, 19. E
Diametrically, 114.
Diaphragm, 112, 113, 116, Earth, 22.
120, 122. Elasticity, 100, 142.
Diamonds, 186. Electric, 6, 31, 49, 50, 76, 78,
Diluted, 86. 81, 131, 142, 158, 162, 173,
Direct current, 38, 140. 176.
Direction of current, 50. Electric arc, 63, 163.
Direction of flow, 98. Electric bell, 19, 69, 70, 71,
Discharge, 172. 72, 106, 117.
Disintegrate, 132. Electric bulbs, 167.
Disk, 43. Electric circuit, 118.
Dissimilar, 37. Electric fan, 55.
Disturbance, 176. Electric field, 76.
Dividers, 14. Electric hand purifier, 129.
Divisibility, 168. Electric heating, 135, 137,
Dot, 96, 97. 161.
Dot and dash, 96. Electric iron, 130, 141.
Double click, 95. Electric lamp socket, 139.
Double line, 65. Electric light, 56, 66.
Double-pole switch, 65. Electric lighting, 161.
Double-throw switch, 117. Electric power, 113.
Drawing, 20. Electric welding, 183.
Drill, ratchet, 13. Electrical, 8, 11, 65, 96, 98,
Drops, 81. 104, 141, 159, 180, 184, 187.
Ductile, 186.
Duplex wire, 115.

p. 212
Electrical impulses, 105, 147, Engine energy, 170, 180.
148. Equidistant, 127.
Electrical manifestations, 175. Ether, 104.
Electrically, 32, 70. Example, 61.

Electricity, 5, 6, 7, 8, 9, 12, Excited, 47.
13, 18, 21, 26, 27, 28, 29, 38, Extension plate, 103.
49, 54, 60, 61, 62, 82, 97, 98, Exterior, 3.
100, 104, 110, 112, 116, 123, Exterior magnetic, 27.
124, 133, 134, 136, 138, 145, External, 37.
146, 147, 154, 156, 160, 166, External circuit, 153.
170, 171, 172, 175, 182, 187. External current, 50.
Electricity measuring, 49. External resistance, 37.
Electricity, thermo-, 142.
Electrified, 37, 186.
F
Electro-chemical, 55.
Electrode, 35, 124, 127, 128,
Factor, 61.
161, 162, 163, 164, 165, 184.
Ferrous oxide, 125.
Electrolysis, 7, 123, 126, 132.
Field, 46, 47.
Electrolyte, 33, 35, 36, 57, 86,
Field, dynamo, 40, 41.
88, 123, 132, 142.
Field magnet cores, 155.
Electrolytic, 55, 123, 125.
Field, magnetic, 38.
Electro-magnet, 59, 78.
Electro-magnetic, 7, 24, 25, Field of force, 33.
29, 37, 55, 92, 93, 94. Field wire, 48.
Electro-magnetic force, 7. Filament, 168, 169, 170.
Electro-magnetic rotation, 7. Filter, 128.
Electro-magnetic switch, 116. Flat iron, 140.
Electro-meter, 7. Flocculent, 128.
Electro-motive force, 37, 63, Force, 50.
99. Formulated, 19.
Electroplate, 12, 38, 48, 123,
132, 134.
Electro-positive-negative,
142, 143.
Elements, 36, 83.

p. 213
Friction, 32. Heart-shaped switch, 77.
Frictional, 6, 7, 29. Heater, 136.
Fuse, 169. Heating, 13, 38.
Hertzian rays, 170.
G Hertzian wave, 184.
High tension, 38, 102, 184.
Galvani, 7. High tension apparatus, 98.
Galvanic, 7, 23, 30. High tension coils, 103.
Galvanometer, 7, 49, 108, High voltage, 158.
143. Horizontal bar, 46.
Galvanoscope, 55, 58, 59. Horseshoe magnet, 22, 24,
Gaseous, 128. 175.
Gasoline, 99. Hydrate of aluminum, 129.

Gas stove, 17. Hydrogen, 35, 123, 125, 128.
Gelatine, 128.
Generate, 29, 38, 134, 136, I
145.
Generated, 55. Igniting, 99.
Generating, 32, 134. Illumination, 162, 163, 165,
Generation, 170. 167, 170.
Generator, 32, 125, 147. Immersed, 133.
German silver, 136, 137. Impulses, 60, 62, 96, 104,
Germicide, 187. 109, 152, 179.
Gimlets, 17. Incandescent, 166, 168.
Glass, 30, 86, 126, 186. Induced, 28.
Gold, 135. Inductance, 149, 150.
Grid, 84. Induction, 27, 37, 98, 147.
Ground circuit, 121. Induction coils, 99, 102, 106.
Gunpowder, 6. Influences, 178.
Initial charge, 88.
H

Hack-saw, 14.
Hammer, 13.

p. 214
Insulated, 27, 28, 40, 43, 52, L
55, 73, 115, 151, 180.
Insulating, 66, 69, 120, 140, Laboratory, 9.
164.
Lead, 31, 136.
Insulating material, 114.
Lead, precipitated, 83, 85.
Insulation, 40, 116.
Lead, red, 83, 84.
Instruments, 49, 94, 112, 118,
Lever switching, 67.
120.
Light, 104.
Instruments, measuring, 8.
Light method, 56.
Intensity, 55, 60, 104, 154.
Lighting, 9, 38.
Interior, magnetic, 23.
Lighting circuit, 48.
Internal resistance, 37.
Lighting system, 82.
Interruption, 102, 103.
Lightning, 6, 171, 172, 173.
Installation, 168.
Lightning rod, 173.
Ionize, 186.
Lime, chloride of, 84.
Iron, 19, 132, 133, 136, 142,
Line of force, 146.
171.
Line wire, 122.
Isolated, 186.
Line, magnetic, 22, 23.
Liquid, 32.
J
Litharge, 83.
Loadstone, 17.
Jar, 29, 31, 32.
Locomotives, 165.
Journal, 46.

Journal block, 16, 146. Low tension, 38, 98, 102, 179.
Jump spark, 99.
M
K
Magnet bar, 20.
Key, 90, 91, 95. Magnet core, 16, 75, 93.
Key, sending, 90. Magnet, electro, 59, 78.
Knob, 32. Magnet, horseshoe, 22, 25,
Knob, terminal, 31. 175.

p. 215
Magnet lines, 22, 23. Measuring devices, 27.
Magnet, permanent, 25, 38, Measuring instruments, 8.
46, 50, 172. Mechanism, 47, 180.
Magnet, reversed, 20. Medical batteries, 99.
Magnet, steel, 53. Mercury, 63, 169.
Magnet, swinging, 53. Metal base, 73.
Magnetic, 7, 19, 20, 21, 22, Mica, 186.
25, 113, 178. Microphone, 118, 119, 120.
Magnetic construction, 39. Millimeter, 63.
Magnetic exterior, 27. Minus, 34.
Magnetic field, 22, 24, 27, 38, Minus sign, 21.
50, 112, 146, 148, 155. Morse code, 76.
Magnetic interior, 23. Motor, 7, 21, 27, 46, 47, 62,
Magnetic pull, 59. 82, 99, 150, 176, 180.
Magnetic radiator, 37. Mouthpiece, 115.
Magnetism, 19, 54, 104, 110, Mouthpiece rays, 188.
159, 171. Moving field, 117.
Magnetized, 18, 25, 27, 50. Multiple, 168.
Magnetized wire, 146. Musical scale, 111.
Magnets, 13, 14, 18, 19, 20,
21, 22, 23, 24, 25, 39, 51, 53, N
54, 70, 71, 73, 75, 81, 90, 93,
112, 113, 115, 147, 150, 163,
Negative, 21, 35, 36, 68, 83,
176, 177, 178.
86, 87, 94, 125, 151, 152, 154,
Main conductor, 31. 165, 177, 178, 179.
Mandrel, 15, 16. Neutral, 125.
Manganese, 19. Neutral plate, 84.
Manifestations, 19. Nickel, 136.
Mariner, 172. Nickel plating, 132.
Material, non-conducting, 90. Nitrate of silver, 62.
Maximum, 154. Nitrogen, 126.
Measure, 55, 56, 60, 62.
Measurement, 62.

p. 216
Non-conducting material, 90. Percolate, 128.
Non-conductor, 164. Periodicity, 159.
Non-magnetic, 19. Periods of alternations, 149.
North pole, 20, 21, 22, 23, 25, Permanent, 18, 19, 50.
50, 54, 156. Permanent magnet, 25, 38, 46,
Number plate, 75. 50, 172.
N-ray, 188. Phase, 19.
Phenomenon, 27, 65.
O Photograph, 186.
Physical, 21.
Ohms, 60, 63. Pile, voltaic, 33.
Ohms, international, 63. Pipe, 61.
Ohms law, 7. Pitchblende, 186.
Operator, 95, 118. Pivot pin, 53.
Oscillating, 99, 105. Pivotal, 22.
Osmium, 169. Plane, 13.
Oxides, 125. Plate, 57, 93.
Oxidizing, 183. Plate, contact, 67, 68, 79.
Oxygen, 35, 123, 125, 126, Plate, copper, 33, 35, 58, 67.
128, 129, 169. Plate, negative, 84.
Plate, number, 75.
P Plate, positive, 84, 88.
Plate, zinc, 33.
Packing ring, 124. Platinum, 13, 57, 137.
Paraffine, 56, 100, 101, 102. Pliers, 14.
Paraffine wax, 86. Plus sign, 21, 24.
Parallel, 87, 88, 89. Pointer, 53.
Parallel switch bar, 67. Polarity, 154, 177, 178, 179.
Parallel wires, 28, 49. Polarization, 35.
Partition, 124. Pole, north, 20, 21, 22, 23, 25,
Peon, 13. 50, 54, 156.

p. 217
Pole piece, 40, 42. R
Pole, south, 20, 21, 22, 25, 50,
54, 156. Radio-activity, 186.
Poles, 177, 179. Radium, 184, 185, 187, 188.
Polonium, 186. Ratchet drill, 13.
Porcelain, 86. Reaction, 148.
Porous, 85. Receiver, 12, 90, 97, 121, 122.
Positive, 4, 21, 25, 36, 40, 68, Receiving station, 109.
83, 86, 87, 94, 123, 125, 151,
Rectangular, 69.
152, 153, 155, 165.
Rectifiers, 146.
Post, binding, 52, 71.
Red lead, 83, 84.

Potentiality, 105, 109. Reel, 13.
Power, 38, 186. Reflected, 185.
Power, candle, 89, 139. Refraction, 185.
Precipitate of lead, 83, 85. Refractory, 182.
Precision, 7. Register, 57.
Pressure, 87. Removable, 54.
Primary, 35, 62, 98, 134, 142, Removable cap, 73.
159, 184. Repel, 20.
Primary battery, 7, 99. Repulsion, 21, 128.
Primary circuit, 99. Reservoir, 61, 62.
Primary coil, 106, 109. Resiliency, 99.
Prime conductor, 6. Resistance, 7, 36, 37, 60, 63,
Projected, 185. 99, 135, 136, 137, 138, 140,
Propagated, 105, 185. 141, 156, 157, 163, 166, 168.
Properties, 55. Resistance bridge, 7.
Purification, 123, 128. Resistance, external, 37.
Purifier, 126, 131. Resistance, internal, 37.
Push button, 65, 68, 69, 70, Rheostat, 7.
76, 79. Reversed, 20, 50, 153.

Q

Quantity, 55, 60, 61, 138.
Quartz, 186.

p. 218
Reversible, 163. Series-wound, 47.
Reversing, 176. Severed magnet, 20.
Reversing switch, 67. Sewage, 12.
Revolubly, 46. Shaft, 30.
Revolve, 179. Shears, 14, 17.
Revolving, 177. Shellac, 40.
Roentgen rays, 184. Shunt-wound, 47.
Roentgen tube, 187. Signal, 118.
Rotation, 149. Silver, 19, 63, 125.
Rubber, 40, 46, 77, 115, 126, Silver nitrate, 62.
130, 138. Socket, 54, 139.
Soldering, 14.
S Soldering iron, 17.
Solution, 55, 57, 62, 63, 84,
Sad-irons, 13. 86, 133, 134, 142.
Saline, 133. Sounder, 90, 92, 95, 96.
Sanitation, 12. Sounding board, 119.
Saturated, 85. Source, charging, 83.
Screw, 15. South pole, 20, 21, 22, 25, 50,
54, 156.

Screw, binding, 65, 66. Spark gap, 102, 106.
Screw-driver, 14. Spark jump, 99.
Screw, set, 72. Spring finger, 69.
Sealing wax, 53. Square, 14, 17.
Secondary, 62, 98, 105, 158, Standard, 62, 63.
159, 160. Station, 94, 95, 117, 122.
Secondary circuit, 99. Steel, 18, 19.
Secondary coil, 107, 108. Steel magnet, 53.
Self-induction, 149, 156. Sterilized, 12.
Sender, 90, 97. Stirrup, 75.
Sending apparatus, 106. Stock bit, 13.
Sending key, 90.
Separately excited, 46.

p. 219

Stock contact, 121. Telegraph key, 106.
Storage, 82. Telegraph sounder, 108, 109.
Storage battery, 107. Telegraphing, 94.
Storing, 82. Telephone, 12, 110, 113, 117,
Substances, 135. 118, 119, 120.
Sulphate, 55, 128, 133. Telephone circuit, 118.
Sulphur, 19. Telephone connections, 116.
Sulphuric acid, 31, 84. Telephone hook, 122.
Sulphuric acid voltameter, 55, Temperature, 56, 88, 134, 161,
57. 170.
Superstition, 171, 173. Tension, high, 38, 102, 184.
Surging, 153, 154. Tension, low, 38, 98, 102, 179.
Swinging magnet, 53. Terminal, 31, 34, 35, 40, 48,
Swinging switch blade, 67. 82, 86, 93, 95, 107, 116, 121,
Switch blades, 66. 122, 151, 152, 153, 154, 156.
Switches, 65, 66, 70, 77, 78, Terminal knob, 31.
90, 117. Terminal, secondary, 102.
Switches, bar, 65, 68, 90, 91. Terminal switch, 81.
Switches, bar, parallel, 67. Theoretical, 160.
Switches, heart-shaped, 78. Therapeutics, 187.
Switches, piece, 77. Thermo-electric couples, 146.
Switches, reversing, 67. Thermo-electricity, 135.
Switches, sliding, 67, 80. Thermometer, 56.
Switches, terminal, 8. Thorium, 169, 186.
Switches, two-pole, 65. Thunderbolt, 171, 173.
System, circuiting, 79. Tin, 136.
Tinfoil, 31, 101.
T Tools, 11, 13, 17.
Torch, brazing, 17.
Tail-piece, 16. Transformer, 145, 146, 158,
Tantalum, 169. 159, 180, 182.
Telegraph, 11, 90, 96.

p. 220
Transformer, step-down, 182. Voltaic pile, 33.
Transmission, 38, 187. Voltameter, 7, 58, 88.
Transmit, 63, 95, 157. Voltameter, sulphuric, acid,
Transmitter, 12, 120, 121, 55, 57.
122, 123. Volts, 60, 62, 87, 89, 132, 158,
Transverse, 16, 52. 159.
Transversely, 43.
Trigger, 75. W
Tripod, 31.
Tubular, 44, 45. Water, 123, 138, 144.

Two-pole switch, 65. Water power, 142.
Watts, 60, 61, 160.
U Wave lengths, 104, 110.
Weight, 49.
Ultra-violet, 185. Welding, 13, 182.
Uranium, 186. Winding, 18, 40, 47, 58, 159,
196.
V Winding reel, 14.
Window connection, 76.
Vacuum, 184. Window frame, 78.
Vapor lamps, 169. Wire, 6, 18, 21, 26, 28, 156.
Velocity, 60, 73. Wire, circuiting, 79.
Vertical armature, 75. Wire coil, 40.
Vibration, 110, 111, 113. Wire lead, 70.
Vibratory, 110. Wire, parallel, 28, 49.
Vise, 13. Wireless, 12.
Voltage, 37, 38, 60, 61, 62, 63, Wireless telegraphy, 103, 104,
87, 88, 99, 147, 154, 165, 180, 184.
182.
Voltage, high, 158.
Voltaic, 29, 32.

p. 221
Wiring, 80. X
Wiring, window, 77.
Workshop, 11, 17. X-ray, 184, 185, 187, 188.
Wound, compound, 48.
Wound-series, 47. Z
Wound-shunt, 47.
Zinc, 17, 34, 35, 85, 135.
Zinc plates, 33.

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