Title: Electricity and Magnetism
Author: Gray, Elisha, 1835-1901
Language: English
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                    _NATURE'S MIRACLES, VOL. III._

                              Electricity
                             and Magnetism

                                  BY
                       ELISHA GRAY, PH.D., LL.D.


                            WILLIAM BRIGGS
                   29-33 Richmond St. West, Toronto
                     C. W. COATES, Montreal, Que.
                     S. F. HUESTIS, Halifax, N.S.



CONTENTS.


  CHAPTER                                           PAGE

          INTRODUCTION                                 v
       I. THE AUTHOR'S DESIGN                          1
      II. HISTORY OF ELECTRICAL SCIENCE                6
     III. HISTORY OF MAGNETISM                        20
      IV. THEORY AND NATURE OF MAGNETISM              25
       V. THEORY OF ELECTRICITY                       39
      VI. ELECTRICAL CURRENTS                         49
     VII. ELECTRIC GENERATORS                         62
    VIII. ATMOSPHERIC ELECTRICITY                     77
      IX. ELECTRICAL MEASUREMENT                      83
       X. THE ELECTRIC TELEGRAPH                      88
      XI. RECEIVING MESSAGES                         103
     XII. MISCELLANEOUS METHODS                      108
    XIII. MULTIPLE TRANSMISSION                      114
     XIV. WAY DUPLEX SYSTEM                          129
      XV. THE TELEPHONE                              134
     XVI. HOW THE TELEPHONE TALKS                    145
    XVII. SUBMARINE TELEGRAPHY                       154
   XVIII. SHORT-LINE TELEGRAPHS                      159
     XIX. THE TELAUTOGRAPH                           165
      XX. SOME CURIOSITIES                           171
     XXI. WIRELESS TELEGRAPHY                        176
    XXII. NIAGARA FALLS POWER--INTRODUCTION          186
   XXIII. NIAGARA FALLS POWER--APPLIANCES            190
    XXIV. NIAGARA FALLS POWER--APPLIANCES            199
     XXV. ELECTRICAL PRODUCTS--CARBORUNDUM           209
    XXVI. ELECTRICAL PRODUCTS--BLEACHING-POWDER      218
   XXVII. ELECTRICAL PRODUCTS--ALUMINUM              223
  XXVIII. ELECTRICAL PRODUCTS--CALCIUM CARBIDE       228
    XXIX. THE NEW ERA                                234



INTRODUCTION.


For the benefit of the readers of Vol. III, who have not read the
general Introduction found in Vol. I, a word as to the scope and object
of this volume will not be amiss.

It will be plain to any one on seeing the size of the little book that
it cannot be an exhaustive treatise on a subject so large as that of
Electricity. This volume, like the others, is intended for popular
reading, and technical terms are avoided as far as possible, or when
used clearly explained. The subject is treated historically,
theoretically, and practically.

As the author has lived through the period during which the science of
Electricity has had most of its growth, he naturally and necessarily
deals somewhat in reminiscence. All he hopes to do is to plant a few
seed-thoughts in the minds of his readers that will awaken an interest
in the study of natural science; and especially in its most fascinating
branch--Electricity.

If Vol. I is at hand, please read the Introduction. It will bring you
into closer sympathy with the author and his mode of treatment.

Again, if the reader is especially interested in the theory of
Electricity it will help him very much if he first reads Vols. I and II,
as a preparation for a better understanding of Vol. III. All the natural
sciences are so closely related that it is difficult to get a clear
insight into any one of them without at least a general idea of all the
others.



NATURE'S MIRACLES.

ELECTRICITY AND MAGNETISM.



CHAPTER I.

THE AUTHOR'S DESIGN.


The writer has spent much of his time for thirty-five years in the study
of electricity and in inventing appliances for purposes of transmitting
intelligence electrically between distant points, and is perhaps more
familiar with the phenomena of electricity than with those of any other
branch of physics; yet he finds it still the most difficult of all the
natural sciences to explain. To give any satisfactory theory as to its
place with and relation to other forms of energy is a perplexing
problem.

It is said that Lord Kelvin lately made the statement that no advance
had been made in explaining the real nature of electricity for fifty
years. While this statement--if he really made it--is rather broad, it
must be acknowledged that all the theories so far advanced are little
better than guesses. But there is value in guessing, for one man's guess
may lead to another that is better, and, as it is rarely the case that
each one does not give us a little different view of the matter, it may
be that out of the multiplicity of guesses there may some time be a
suggestion given to some investigator that will solve the problem, or at
least carry the theme farther back and establish its true relationship
to the other forms of energy. I cannot but think that there is yet a
simple statement to be made of Energy in its relation to Matter that
will establish a closer relationship between the different branches of
physical science. And this, most likely, will be brought about by a
better understanding of the nature of the interstellar substance called
Ether, and its relation to all forms and conditions of sensible matter
and energy.

In the talks that will follow it will be the endeavor of the writer to
give such a simple and popular exposition of the phenomena and
applications of electricity, in a general way only, that the popular
reader may get, at least, an elementary understanding of the subject so
far as it is known. As we have said, the descriptions will have to be
elementary, for nothing else can be done without such elaborate
technical drawings and specifications as would be impossible in our
limited space, and would not be clear to the ordinary reader who knows
nothing of the science.

Thousands who are employed in various ways with enterprises, the
foundations of which are electrical, know nothing of electricity as a
science. A friend of mine, who is a professor of physics in one of our
colleges, was traveling a few years ago, and in his wanderings he came
across some sort of a factory where an electric motor was employed.
Being on the alert for information, he stepped in and introduced himself
to the engineer, and began asking him questions about the electric motor
of which he had charge. The professor could talk ohm, ampères, and volts
smoothly, and he "fired" some of these electrotechnical names at the
engineer. The engineer looked at him blankly and said: "You can't prove
it by me. I don't know what you're talking about. All I know is to turn
on the juice and let her buzz." How much "juice" is wasted in this
cut-and-dry world of ours and how much could be saved if only all were
even fairly intelligent regarding the laws of nature! A great deal of
the business of this world is run on the "let her buzz" theory, and the
public pays for the waste. It will continue to be so until a higher
order of intelligence is more generally diffused among the people. A
fountain can rise no higher than its source. A business will never
exceed the intelligence that is put into it, nor will a government ever
be greater than its people.

Let us begin the subject of electricity by going somewhat into its past
history. It is always well to know the history of any subject we are
studying, for we often profit as much by the mistakes of others as by
their successes. I shall also give the theories advanced by different
investigators, and if I should have any thoughts of my own on the
subject I shall be free to give them, for I have just as good a right to
make a guess as any one. It must be confessed, however, that the older I
grow the less I feel that I know about the subject of electricity, or
anything else, in comparison with what I see there is yet to be known. I
once met a young man who had just graduated from college, and in his
conversation he stated that he had taken a course in electricity. I
asked him how long he had studied the subject. He said "three months." I
asked him if he understood it--and he said that he did. I told him that
he was the man that the world was looking for; that I had studied it for
thirty years and did not understand it yet.

"A little learning is a dangerous thing"--for it puffs us up, and we
feel that we know it all and have the world in our grasp; but after we
have tried our "little learning" on the world for a while and have
received the many hard knocks that are sure to come, we are sooner or
later brought up in front of the mirror of experience, and we "see
ourselves as others see us," and are not satisfied with the view.

Whatever the theories may be regarding electricity, and however
unsatisfactory they may be, there are certain well-defined facts and
phenomena that are of the greatest importance to the world. These we may
understand: and to this end let us especially direct our efforts.



CHAPTER II.

HISTORY OF ELECTRICAL SCIENCE.


Electricity as a well-developed science is not old. Those of us who have
lived fifty years have seen nearly all its development so far as it has
been applied to useful purposes, and those who have lived over
twenty-five years have seen the major portion of its development.

Thales of Miletus, 600 B.C., discovered, or at least described, the
properties of amber when rubbed, showing that it had the power to
attract and repel light substances, such as straws, dry leaves, etc. And
from the Greek word for amber--elektron--came the name electricity,
denoting this peculiar property. Theophrastus and Pliny made the same
observations; the former about 321 B.C., and the latter about 70 A.D. It
is also said that the ancients had observed the effects of animal
electricity, such as that of the fish called the torpedo. Pliny and
Aristotle both speak of its power to paralyze the feet of men and
animals, and to first benumb the fish which it then preyed upon. It is
also recorded that a freed-man of Tiberius was cured of the gout by the
shocks of the torpedo. It is further recorded that Wolimer, the King of
the Goths, was able to emit sparks from his body.

Coming down to more modern times--A.D. 1600--we find Dr. Gilbert, an
Englishman, taking up the investigation of the electrical properties of
various substances when submitted to friction, and formulating them in
the order of their importance. In these experiments we have the
beginnings of what has since developed into a great science. He made the
discovery that when the air was dry he could soon electrify the
substances rubbed, but when it was damp it took much longer and
sometimes he failed altogether. In 1705 Francis Hawksbee, an
experimental philosopher, discovered that mercury could be rendered
luminous by agitating it in an exhausted receiver. (It is a question
whether this phenomenon should not be classed with that of
phosphorescence rather than electricity.) The number of investigators
was so great that all of them cannot be mentioned. It often happens that
those who do really most for a science are never known to fame. A number
of people will make small contributions till the structure has by
degrees assumed large proportions, when finally some one comes along and
puts a gilded dome on it and the whole structure takes his name. This is
eminently true of many of the more important developments in the
science and applications of electricity during the last twenty-five or
thirty years.

Following Hawksbee may be mentioned Stephen Gray, Sir Isaac Newton, Dr.
Wall, M. Dupay and others. Dupay discovered the two conditions of
electrical excitation known now as positive and negative conditions. In
1745 the Leyden jar was invented. It takes its name from the city of
Leyden, where its use was first discovered. It is a glass jar, coated
inside and out with tin-foil. The inside coating is connected with a
brass knob at the top, through which it can be charged with electricity.
The inner and outer coatings must not be continuous but insulated from
each other. The author's name is not known, but it is said that three
different persons invented it independently, to wit, a monk by the name
of Kleist, a man by the name of Cuneus, and Professor Muschenbroeck of
Leyden. This was an important invention, as it was the forerunner of our
own Franklin's discoveries and a necessary part of his outfit with which
he established the identity of lightning and electricity. Every American
schoolboy has heard, from Fourth of July orations, how "Franklin caught
the forked lightning from the clouds and tamed it and made it
subservient to the will of man." How my boyish soul used to be stirred
to its depths by this oratorical display of electrical fireworks!

Franklin had long entertained the idea that the lightning of the clouds
was identical with what is called frictional electricity, and he waited
long for a church spire to be erected in his adopted home, the Quaker
City, in order that he might make the test and settle the question. But
the Quakers did not believe in spires, and Franklin's patience had a
limit.

Franklin had the theory that most investigators had at that time, that
electricity was a fluid and that certain substances had the power to
hold it. There were two theories prevalent in those days--both fluid
theories. One theory was that there were two fluids, a positive and a
negative. Franklin held to the theory of a single fluid, and that the
phenomenon of electricity was present only when the balance or natural
amount of electricity was disturbed. According to this theory, a body
charged with positive electricity had an excessive amount, and, of
course, some other body somewhere else had less than nature had allotted
to it; hence it was charged with negative electricity. A Leyden jar, for
instance, having one of its coatings (say the inside) charged with
positive or + electricity, the other coating will be charged with
negative or - electricity. The former was only a name for an amount
above normal and the latter a name for a shortage or lack of the normal
amount.

As we have said, Franklin believed in the identity of lightning and
electricity, and he waited long for an opportunity to demonstrate his
theory. He had the Leyden jar, and now all he needed was to establish
some suitable connection between a thunder-cloud and the earth.

Previous to 1750 Franklin had written a paper in which he showed the
likeness between the lightning spark and that of frictional electricity.
He showed that both sparks move in crooked lines--as we see it in a
storm-cloud, that both strike the highest or nearest points, that both
inflame combustibles, fuse metals, render needles magnetic and destroy
animal life. All this did not definitely establish their identity in the
mind of Franklin, and he waited long for an opportunity, and finally,
finding that no one presented itself, he did what many men have had to
do in other matters; he made one.

In the month of June, 1752, tired of waiting for a steeple to be
erected, Franklin devised a plan that was much better and probably saved
the experiment from failure; for the steeple would probably not have
been high enough. He constructed a kite by making a cross of light cedar
rods, fastening the four ends to the four corners of a large silk
handkerchief. He fixed a loop to tie the kite string to and balanced it
with a tail, as boys do nowadays. He fixed a pointed wire to the upper
end of one of the cross sticks for a lightning-rod, and then waited for
a thunder-storm. When it came, with the help of his boy, he sent up the
kite. He tied a loop of silk ribbon on the end of the string next his
hand--as silk was known to be an insulator or non-conductor--and having
tied a key to the string he waited the result, standing within a door to
prevent the silk loop from getting wet and thus destroying its
insulating qualities. The cloud had nearly passed and he feared his long
waited for experiment had failed, when he noticed the loose fibers of
the string standing out in every direction, and saw that they were
attracted by the approach of his finger. The rain now wet the string and
made a better conductor of it. Soon he could draw sparks with his
knuckle from the key. He charged a Leyden jar with this electrical
current from the thunder-cloud, and performed all the experiments with
it that he had done with ordinary electricity, thus establishing the
identity of the two and confirming beyond a doubt what he had long
before believed was true. In after experiments Franklin found that
sometimes the electricity of the clouds was positive and at other times
negative. From this experiment Franklin conceived the idea of erecting
lightning-rods to protect buildings, which are used to this day.

The news spread all over Europe, not through the medium of electricity,
however, but as soon as sailing vessels and stage-coaches could carry
it. Many philosophers repeated the experiments and at least one man
sacrificed his life through his interest in the new discovery. In 1753
Professor Richman of St. Petersburg erected on his house a metal rod
which terminated in a Leyden jar in one of the rooms. On the 31st of May
he was attending a meeting of the Academy of Sciences. He heard a roll
of thunder and hurried home to watch his apparatus. He and one of the
assistants were watching the apparatus when a stroke of lightning came
down the rod and leaped to the professor's head. He was standing too
near it and was instantly killed.

Passing over many names of men who followed in the wake of Franklin we
come to the next era-making discovery, namely, that of galvanic
electricity. In the year 1790 an incident occurred in the household of
one Luigi Galvani, an Italian physician and anatomist, that led to a new
and important branch of electrical science. Galvani's wife was preparing
some frogs for soup, and having skinned them placed them on a table near
a newly charged electric machine. A scalpel was on the table and had
been in contact with the machine. She accidentally touched one of the
frogs to the point of the scalpel, when, lo! the frog kicked, and the
kick of that dead frog changed the whole face of electrical science. She
called her husband and he repeated the experiment, and also appropriated
the discovery as well, and he has had the credit of it ever since, when
really his wife made the discovery. Galvani supposed it to be animal
electricity and clung to that theory the rest of his life, making many
experiments and publishing their results; but the discovery led others
to solve the problem.

Alessandro Volta, a professor of natural philosophy at Pavia, Italy,
was, it must be said, the founder of the science of galvanic or voltaic
electricity. Stimulated by the discovery of Galvani he attributed the
action of the frog's muscles, not to animal electricity, but to some
chemical action between the metals that touched it. To prove his theory,
he constructed a pile made of alternate layers of zinc, copper, and a
cloth or pasteboard saturated in some saline solution. By repeating
these trios--copper, zinc, and the saturated cloth--he attained a pile
that would give a powerful shock. It is called the Voltaic Pile.

I have a clear idea of the construction of this form of pile, founded on
experience. It was my habit when a boy to make everything that I found
described, if it were possible. The bottom of my mother's wash-boiler
was copper, and just the thing to make the square plates of copper to
match the zinc ones, made from another piece of domestic furniture used
under the stove. I shocked my mother twice--first with the voltaic pile
that I had constructed, and again when she found out where the metal
plates came from. The sequel to all this was--but why dwell upon a
painful subject!

Galvanism and voltaic electricity are the same. Volta was the first to
construct what is termed the galvanic battery. The unit of electrical
pressure or electromotive force is called the volt, and takes its name
from Volta, the great founder of the science of galvanic or voltaic
electricity. From this pile constructed by Volta innumerable forms of
batteries have been devised. The evolution of the galvanic battery in
all its forms, from Volta to the present day, would fill a large volume
if all were described.

The discoveries of Michael Faraday (1791-1867), the distinguished
English chemist and physicist, led to another phase of the science that
has revolutionized modern life. Faraday made an experiment that contains
the germ of all forms of the modern dynamo, which is a machine of
comparatively recent development. He found that by winding a piece of
insulated wire around a piece of soft iron and bringing the two ends
(of the wire) very close together, and then placing the iron across the
poles of a permanent magnet and suddenly jerking it away, a spark would
pass between the two ends of the wire that was wound around the piece of
soft iron. Here was an incipient dynamo-electric machine--the germ of
that which plays such an important part in our modern civilization.

Having brought our history down to the present day, it would seem
scarcely necessary to recite that which everybody knows. It is well,
however, to call a halt once in a while and compare our present
conditions of civilization with those of the past. Our world is filled
with croakers who are always sighing for the good old days. But we can
easily imagine that if they could go back to those days their croaking
would be still louder than it is.

Before the advent of electricity many things were impossible that are
easy now. In the old days the world was very, very large; now, thanks to
electricity, it is knocking at the door of every man's house. The
lumbering stage-coach that was formerly our limited express--limited to
thirty or forty miles a day--has been supplanted by one that covers 1000
miles in the same time, and this high rate of speed is made possible
only by the use of the electric telegraph.

In the old days all Europe could be involved in a great war and the news
of it would be weeks in reaching our shores, but now the firing of the
first gun is heard at every fireside the world over, almost before the
smoke has cleared away. Our planet is threaded with iron nerves that run
over mountains and under seas, whose trembling atoms, thrilled with the
electric fire, speak to us daily and hourly of the great throbbing life
of the whole civilized world.

Electricity has given us a voice that can be heard a thousand miles, and
not only heard, but recognized. It has given us a pen that will write
our autograph in New York, although we are still in Chicago. It has
given us the best light, both from an optical and a sanitary standpoint,
that the world has ever seen. The old-fashioned, jogging horse-car has
been supplanted by the electric "trolley," and we no longer have our
feelings harrowed with pity for the poor old steeds that pulled those
lumbering coaches through the streets, with men and women crowded in and
hanging on to straps, while everybody trod on every other body's toes.

  "In olden times we took a car
  Drawn by a horse, if going far,
    And felt that we were blest;
  Now the conductor takes the fare
  And puts a broomstick in the air--
    And lightning does the rest.

  "In other days, along the street,
  A glimmering lantern led the feet,
    When on a midnight stroll;
  But now we catch, when night is nigh,
  A piece of lightning from the sky
    And stick it on a pole.

  "Time was when one must hold his ear
  Close to a whispering voice to hear,
    Like deaf men--nigh and nigher;
  But now from town to town he talks
  And puts his nose into a box
    And whispers through a wire."

So jogs the old world along. We sometimes think it is slow, but when we
look back a few years and see what has been accomplished it seems to
have had a marvelously rapid development.

Something like fifty years ago a professor of physics in one of our
colleges was giving his class a course in electricity. The electric
telegraph was too little known at that time to cut much of a figure in
the classroom, so the stock experiments were those made with the
frictional electric machine and the Leyden jar. One day the professor
had, in one hour's time, taken his class through a course of
electricity, and at the end he said: "Gentlemen, you were born too late
to witness the development of this great science." I often wonder if the
good professor is ever allowed to part the veil that separates us from
the great beyond and to look down upon this busy world of ours in which
electricity plays such an important part in our every-day life; and if
so, what he thinks of that little speech he made to the boys fifty years
or more ago.

If we make an analysis of the history of the science of electricity we
shall see that it has progressed in successive eras, shortening as they
approach our time. For a period of 2300 years, from Thales to Franklin,
but little or no progress was made beyond the further development of the
phenomena of frictional electricity--the most important invention being
that of the Leyden jar. From Franklin to Volta was forty-eight years,
and from Volta to Faraday about thirty-two years. From this time on the
development was very rapid as compared with the old days. Soon after
Faraday, Morse, Henry, Wheatstone, and others began experiments that
have grown, during fifty or sixty years, into a most colossal system of
electric telegraphs, telephones, electric lights and electric railroads.
In the latter days marvel has succeeded marvel with such rapid strides
that the ink is scarcely dry from the description of one before another
crowds itself upon our attention. Where it will all end no one knows,
but that it has ended no one believes. The human mind has become so
accustomed to these periodic revelations of the marvelous that it must
have the stimulus once in a while or it suffers as the toper does when
deprived of his cups. The commercial instinct of the news-vender is not
slow to see the situation, and if the development is too slow to suit
the public demand his fertile brain supplies the lack. So that every few
days we hear of some great discovery made by some one it may be unknown
to fame. It has served its purpose. The public mind has had its mental
toddy and has been saved from a fit of intellectual delirium tremens
that it was in danger of from lack of its accustomed stimulus.

Having given you a very limited outline of the history of electricity,
from ancient times down to the present, we will endeavor now to give you
an elementary notion of the science as it stands to-day. To the common
mind the science is a blank page. So little is known of it by the
ordinary reader, who is fairly intelligent in other matters, that to
account for anything that we do not understand it is only necessary to
say that it is an electrical phenomenon and he accepts it. Electricity
is a synonym for all that we cannot understand. Inasmuch as magnetism is
so closely related to electricity in its uses as related to every-day
life, we will carry the two subjects along together, as the one will to
a large extent help to explain the other. In our next chapter we will
look at the history of magnetism.



CHAPTER III.

HISTORY OF MAGNETISM.


It is said that the word magnetism is derived from the name of a Greek
shepherd, called Magnes, who once observed on Mount Ida the attractive
properties of loadstone when applied to his iron shepherd's crook. It is
more likely that the name came from Magnesia, a country in Lydia, where
it was first discovered. It was also called Lapis Heracleus. Heraclea
was the capital of Magnesia. Loadstone is a magnetic ore or oxide of
iron found in the natural state, and has at some time by natural
processes been rendered magnetic--that is, given the power of attracting
iron, and, when suspended, of pointing to the North and South Poles. The
power of the natural magnet was known at a very early age in the history
of man. It was referred to by Homer, Pythagoras, and Aristotle. Pliny
also speaks of it, and refers to one Dinocares, who recommended to
Ptolemy Philadelphus to build a temple at Alexandria and suspend in its
vault a statue of the queen by the attractive power of "loadstones."
There is also mention of a statue being suspended in like manner in the
temple of Serapis, Alexandria.

It is claimed that the Chinese knew of and used the magnetic needle in
the earliest times and that travelers by land employed this needle
suspended by a string to guide them in their journeys across the country
a thousand years before Christ. Notwithstanding the claims of the
Chinese and Arabians to the discovery of the use of the magnetic needle,
modern authors question whether the ancients were familiar with any
artificial construction of a magnetic needle, however much they may have
studied and used the loadstones. No doubt the loadstone in its natural
state was used by mariners to steer their ships by, long before its
artificial counterpart was invented. In a history of the discovery of
Iceland, by Are Frode, who was born in 1068, it is stated that a mariner
by name of Folke Gadenhalen sailed from Norway in search of Iceland in
the year 868, and that he carried with him three ravens as guides, for
he says, "in those times seamen had no loadstones in the northern
countries." The magnetic needle as applied to the mariner's compass was
known in the eleventh century, as proved by various authors. In an old
French poem, the manuscript of which still exists, the mariner's compass
is clearly mentioned. The author was Guyot, of Provence, who was alive
in 1181.

Like electricity, magnetism has had a long history, but little use was
made of it till modern times beyond that of the mariner's compass. It
can readily be seen what an important factor it was in the science of
navigation. Long after the discovery of the compass needle there were
many perplexing problems arising, and all sorts of theories were
advanced to account for the various phenomena. The variation of the
needle was one of these problems. It is said that Columbus was the first
to discover the variation of the needle, as well as America. This is
disputed, however, as every man's pretensions usually are. However this
may be, Columbus had to invent some plausible theory to account for this
variation to prevent a mutiny among his crew. They were very
superstitious and thought that they were sailing into a new world where
the laws of nature were different from those of Spain. One phenomenon
that disturbed Columbus was the dip of the needle. As we move in a
northerly direction a magnetic needle dips, and it was the observation
of this phenomenon in different latitudes that finally resulted in the
invention of the dipping needle. It is well known that one pole of a
magnetic needle points to the north and the other to the south. In other
words, what is called the north pole of a needle points to one of the
magnetic poles of the earth which is in the direction of the north
pole, though not the same as the geographical pole. A dipping needle
revolves on an axis so that it can point to any declination. If we
should construct one that is perfectly balanced, so as to lie in a
perfectly horizontal direction before it is magnetized, it will dip--in
this latitude--downward toward the north after magnetization. If we keep
moving northward it will continue to dip downward till we come to the
true magnetic pole, when what is called the north pole of the needle
will point directly downward. If we go back to the equator the needle
will lie horizontally again. We call the end of the needle that points
to the north the north pole. It is really the south pole, because unlike
poles attract each other. If the magnetic poles of the earth are at the
north and south geographical poles, the south pole of the needle will
point north. But it is less confusing to call the end of the needle that
points north the north pole. The nomenclature is purely arbitrary.

It was not until it was learned that magnets could be made by
electricity that they became commercially important outside of their use
in navigation. The advent of electricity has brought magnetism to the
front as one of the great factors in our modern civilization. And we
might say with equal force that the discovery of magnetism has brought
electricity to the front. The truth is that they depend upon each
other. Electricity would be robbed of a large part of its importance as
a factor in modern life if it were not for its relation to magnetism.
Even electric lighting would be impossible, commercially, if it were not
for the part magnetism plays in the production of electricity for this
purpose. It could not be successfully carried on with any battery but
the storage-battery, and the storage-battery is dependent upon the
dynamo, and the dynamo is a magneto-electric machine. When we come to
analyze the relation between magnetism and electricity we cannot
separate them without robbing each of a large part of its usefulness.
They are interdependent forces.

As in the case of electricity there have been many theories regarding
magnetism. One philosopher in the old days accounts for the variation of
the compass-needle on the theory that there are two globes, one
revolving within the other, and that any derangement of their normal
movements in relation to each other affects the needle. Evidently there
were cranks in those days as well as now. Another theory of magnetism
was that there were two fluids--a boreal and an austral--one developing
north polarity and the other south polarity. In the next chapter the
nature of magnetism in the light of modern investigation will be
discussed.



CHAPTER IV.

THEORY AND NATURE OF MAGNETISM.


Iron and steel have a peculiar property called magnetism. It is an
attraction in many ways unlike the attraction of cohesion or the
attraction of gravitation. It is very certain that magnetism is an
inherent property of the molecules of iron and steel, and, to a small
degree, other forms of matter. That is to say, the molecules are little
natural magnets of themselves. It is as unnecessary to inquire why they
are magnets as it is to inquire why the molecules of all ordinary
substances possess the attraction of cohesion. The one is as easy to
explain as the other. People of all ages have insisted upon making a
greater mystery of all electrical and magnetic phenomena than they do of
other natural forces. Ampère's theory is that electric currents are
flowing around the molecules which render them magnetic; but it is just
as easy to suppose that magnetism is an inherent quality of the
molecule. (The word molecule is here used as referring to the smallest
particle of iron.)

These little molecular magnets, so small that 100,000 million million
million of them can be put into a cubic inch of space, have their
attractions satisfied by forming into little molecular rings, with their
unlike poles together, so that when the iron is in a natural or
unmagnetized condition it does not attract other iron. If I should take
a ring of hardened steel and cut it into two or more pieces and
magnetize them, each one of the pieces would be an independent magnet.
If now I put them together in the form of a ring they will cling
together by their mutual attraction for each other. Before I put them
together into a ring each piece would attract and adhere to other pieces
of iron or steel. But as soon as they are put together in the ring they
are satisfied with their own mutual attraction, and the ring as a whole
will not attract other pieces of iron.

Suppose the pieces forming the ring--it may be only two, if you
choose--are as small as the molecules we have described, the same thing
would be true of them. Each molecular ring would have its magnetic
attractions satisfied and would not attract other molecules outside of
its own little circle. When the iron is in the neutral state it will not
as a mass attract another piece of iron, because the millions of little
natural magnets of which it is made up have their attractive force all
turned in upon themselves.

Now, if we make a helix, or coil, of insulated wire and put a piece of
iron into it, and pass a current of electricity through the helix, the
iron becomes a magnet. Why? Because the electric current has the power
to break up these molecular magnetic rings and turn all their like poles
in one direction, so that their attractions are no longer satisfied
among themselves, and with a combined effort they reach outside and
attract any piece of iron that is within reach. In this state we say it
is magnetized. Most people think that we have put something into the
iron, but we have not; we have only developed and made active its
inherent power. It must be kept in mind that it takes power to develop
this magnetic power from its state of neutrality and that something is
never made from nothing. When this power is developed it will do work in
falling back to its natural state. The power is natural to the molecules
of the metal. It is only being exerted in a new direction. The millions
of little natural magnets have been forced to combine their attractions
into one whole and exert it on something outside of themselves. They are
under a strain in this condition, like a bent bow, and there is a
tendency to fly back to the natural position, and if it is soft iron and
not steel, they will fly back as soon as the power that wrenched them
apart and is holding them apart is taken away. This power is the
electric current. Now break the current, and the little natural magnets,
that have been so ruthlessly torn from their home circle attachments,
fly back to them again with the speed of lightning, and the iron rod as
a whole is no longer a magnet. The power to become so under the
electrical strain is in it still--only latent.

The kind of magnet that we have been describing is called an
electromagnet. It is a magnet only so long as the electric current is
passing around it. There is another kind of magnet called a permanent
magnet that will remain a magnet after the current is taken away. The
permanent magnet is made of steel and hardened; then its poles are
placed, to the poles of a powerful magnet, either electro or permanent,
when its molecular rings are wrenched apart and arranged in a polarized
position as heretofore described. Now take it away from the magnet and
it will be found to retain its magnetism. The molecules tend to fly back
the same as those of the soft iron, but they cannot because hardened
steel is so much finer grained than soft iron, and the molecules are so
close together that they are held in position by a friction that is
called its coercive force. The soft iron is comparatively free from this
coercive force, because its molecules are free to move on each other, so
that when they are wrenched out of their natural position they fly back
by their own attractions as soon as the force holding them apart is
taken away. The molecules of hardened steel are unable to fly back,
although they tend to do it just as much as in the iron, and so it is
called a permanent magnet. Its molecules also are under a strain, like a
bent bow. (The form of such a magnet is usually that of a horse-shoe, or
U.)

Let us use a homely illustration that may help us to understand. Let ten
boys represent the molecules in a piece of iron. Let them pair off into
five pairs and each one clasp his mate in his arms; each one, say, is
exerting a force of ten pounds, and it would require a force of twenty
pounds to pull any one of the pairs apart. The five pairs are exerting a
force of one hundred pounds, but this force is not felt outside of
themselves. Now let them unclasp themselves and take hold of a rope that
is tied to a post, and all pull with the same force that they were
using, to wit, ten pounds each, and all pull in the same direction, and
they would put a strain of one hundred pounds upon the post, the same
power that they were exerting upon themselves before they combined their
efforts on something outside of themselves. So with the magnet. So long
as the force of each molecule is wholly spent upon its neighbor there is
nothing left for exterior use. But as soon as they all line up and pull
conjointly in the same direction their combined force is felt outside.
The analogy may not be perfect, but it will help you to get a mental
picture of what takes place in iron when it is magnetized.

We have now described the magnet and the inherent power residing in the
molecular structure of iron. It is this magic power slumbering in its
molecules and the ability of the electric current to arouse them to
action at will and to hold them in action and at will let them fly back
to their normal position, that gives to electricity and magnetism--twin
sisters in nature's household--their great value as the servants of man.
There would be no virtue in winding up a weight if it could not run down
and do work in its fall. Simply bending a bow would never send the arrow
flying over its course; it must be released as well. The magnet could
not accomplish the great work it does if we could only charge it and not
have the ability to discharge it. Without this ability the electric
motor would not revolve, the electric light would not burn, the click of
the telegraph would not be heard, the telephone would not talk, nor
would the telautograph write.

I have said that the permanent magnet would hold its charge after once
having been magnetized. This is true only in a sense and under favorable
conditions. If made of the best of steel for the purpose and hardened
and tempered in just the right way, it will hold its charge if it is
given something to do. If a piece of iron is placed across its poles it
also becomes a magnet and its molecules turn and work in harmony with
those of the mother magnet. These magnetic lines of force reach around
in a circuit. Even before the iron, or "keeper," as it is called, is put
across its poles there are lines of force reaching around through the
air or ether from one pole to another. (For a description of Ether see
Chap. V.) This is called the "field" of the magnet, and when the iron is
placed in this field the lines of force pass through it in a closed
circuit, and if the "keeper" is large enough to take care of all the
lines of force in the field the magnet will not attract other bodies,
because its attraction is satisfied, like its prototype in the molecular
ring described above.

We speak of lines of force, not that force is necessarily exerted in a
bundle of lines but as a convenient way of telling the strength of a
magnetic field. The practical limit of the magnetization of soft iron
(called saturation) is 18,000 lines to the square centimeter. As long as
we give our magnet something to do, up to the measure of its capacity,
it will keep up its power. We may make other magnets with it, thousands,
yea, millions of them, and it not only does not lose its power but may
be even stronger for having done this work. If, however, we hang it up
without its "keeper," and give it nothing to do, it gradually returns to
its natural condition in the home circle of molecular rings. Little by
little the coercive force is overcome by the constant tendency of the
molecule to go back to its natural position among its fellows.

The magnet furnishes many beautiful lessons, as indeed do all the
natural phenomena. Every man has within him a latent power that needs
only to be aroused and directed in the right way to make his influence
felt upon his fellows. Like the magnet, the man who uses his power to
help his fellows up to the measure of his limitations not only has been
a benefactor to his race, but is himself a stronger and better man for
having done so. But, again, like the magnet, if he allows these
God-given powers to lie still and rust for want of legitimate use he
gradually loses the power he had and becomes simply a moving thing
without influence or use in a world in which he vegetates. But let us
leave philosophy and go back to science.

One of the striking exhibitions of magnetism is found in the earth. The
earth itself is a great magnet; and there is good reason for believing
that it is an electromagnet of great power. The magnetic poles of the
earth are not exactly coincident with the geographical poles, and they
are not constant. There is a gradual deviation going on, but as it
follows a certain law mariners are able to tell just what the deviation
should be at a certain time. The magnetic pole revolves around the polar
axis of the earth once in about 320 years. A thermal current (one
produced by heat) of electricity seems to flow around the earth caused
by the irregularities of temperature at the earth's surface, as the sun
makes his daily round. These earth currents vary at times, and other
phenomena are the occasion. This will be discussed when we come to
electric storms.

The value of the earth's magnetism is seen most in the science of
navigation. A magnetic needle is only a slender permanent magnet
suspended very delicately, and when not under local influence it points
north and south on the magnetic axis. The law of its action may be
explained as follows: Take a straight bar magnet of fairly good power
and suspend a magnetic needle over it. The needle will arrange itself
parallel to the bar magnet. The north pole of the needle will point
toward the south pole of the bar magnet. In the presence of the magnet
the needle is not affected by the earth, but yields to a superior force.
If, however, the bar magnet is taken out of the way of the needle it
will immediately arrange itself north and south. Of course if the
earth's magnetic axis changes the needle will vary with it. This
variation is uniform and in navigation is reduced to a science, so that
the mariner knows how much to allow for the variation. Columbus, as
heretofore mentioned, was supposed to have first noticed this variation
and it made him trouble. He did not know how to account for it, and as
his crew thought the laws of nature were changing because they were so
far from home he saw the necessity for some sort of explanation. So,
like the brave man that he was, he hatched up a theory that satisfied
the crew, and although in the light of the closing years of the
nineteenth century it was a questionable one, it worked well enough in
practice to serve his purpose.

We have already stated that the earth was a great magnet, and that
probably it was an electromagnet, caused by earth currents circulating
around the globe. You want to know how the earth can be a magnet unless
it has an iron core like an electromagnet. Magnetism or magnetic lines
of force may be developed without the presence of iron. When we pass a
current of electricity through a wire, magnetic lines of force are
thrown out at right angles with the direction of the current. This will
be fully explained further on. If we wind the wire into a coil, or
helix, these magnetic lines are concentrated. If now we suspend this
helix, or, better, float it on water so that it can move freely, and
pass a current of electricity through it, the helix will arrange itself
north and south the same as a magnetic needle. Its attractive properties
are feeble in comparison with that of the iron, but it obeys the laws of
a magnet. The earth is probably a magnet of this kind, consisting mostly
of lines of force.

However, the iron in the earth is affected magnetically, as we have
evidence in the loadstone. The earth has the power also to magnetize
iron through the medium of its magnetic field, that reaches out in lines
of force from pole to pole like those of the artificial magnet. If we
hold a bar of iron in line with the magnetic axis of the earth and dip
it in line with the dipping needle and then strike it a few blows on the
end, it will be found to be feebly magnetic. The blows have partly
loosened the molecules and during the moment that they unclasped
themselves the earth's magnetism has through its lines of force caught
them for a time and held them a little out of their natural position--as
they are in a state of rest. The peculiar changing light that we
sometimes see in the northern sky, that is called the Aurora Borealis
(Northern Light), is indirectly due to intense magnetic lines of force
that radiate from the north magnetic pole of the earth. Those lines of
force are able to cause the rarified air molecules to become feebly
incandescent, giving them the appearance that we see in a tube that is a
partial vacuum when electricity is passed through it. While these
auroral displays may be seen almost any night in the far north, they
vary greatly in their intensity, so it is only once in a while that they
are visible in the temperate latitudes.

What are called magnetic storms occur occasionally, and at such times
the telegraph service will sometimes be paralyzed on all the east and
west lines for many hours. Strong earth-currents will flow east and
west, and be so powerful and so erratic that it is sometimes impossible
to use the telegraph. It sometimes happens that the operators can throw
off their batteries and work on the earth-current alone. Sometimes it is
necessary to make a complete metallic circuit to get away from the
influence of the earth in order to use the telegraph. Currents equal to
the force of 2,000 cells of ordinary battery have been developed
sometimes in telegraph wires. This of course is a mere fraction of what
is passing through the earth under the wire through which the current
flowed. On the 17th and 18th of November, 1882, a magnetic storm
occurred that extended around the globe, as it was felt wherever there
were telegraph wires. These magnetic storms are attended by brilliant
displays of the aurora, and this fact strengthens the theory that the
earth is a great electromagnet; for the stronger the electrical current
the more powerful we should expect the magnetism to be, and this is
shown by the action of the magnetic needle at such times. The stronger
the magnet the more intense will be the lines of force, and naturally
the more intense the light, if indeed these lines of force are the cause
of the light. There is evidently some close relation between the two.

Another coincidence is that at the times of these storms there is an
unusual display of sun-spots. These sun-spots seem to be great holes
that have been blown through the photosphere of the sun. The photosphere
is a great luminous body of gaseous matter that is believed to envelop
the sun, so that we do not see the core of the sun unless it is when we
look into one of these spots. In some way, evidently, the sun affects
the earth by radiating magnetic lines of force which are cut by the
earth's revolution, and so creating currents of electricity. The sun is
the field-magnet, and the earth is the revolving armature of nature's
great dynamo-electric machine. It would seem that the radiant energy
that comes out through these spots or these holes in the sun's envelope,
are more potent to develop earth-currents than the ordinary rays; and
so, when for a brief while in the revolution of the earth about the sun,
these extra potent rays strike the earth, an unusual energy is
developed, and these unusual phenomena are the consequence. These
phenomena seem to occur periodically; some years (about eleven)
intervening.

All the forces and phenomena of nature are thus seen to be in a state of
unrest. And it is to this unrest, which does not stop with visible
things, but pervades even the atoms of matter throughout the universe,
that we are indebted for the ability to carry on all the activities of
life, and for life itself. For universal quiet would mean universal
death. The cyclone and tornado that devastate and strike terror to a
whole region are only eccentricities of nature when she is setting her
house to rights. The play of natural forces has disturbed her
equilibrium, and she is but making an effort to restore it.



CHAPTER V.

THEORY OF ELECTRICITY.


In the series of chapters on Heat (Vol. II) and in the chapter on
Magnetism the word molecule was frequently used synonymously with atom.
In chemistry a distinction is made, and as we can better explain the
theory, at least, of electricity by keeping this distinction in mind we
will refer to it here.

It has been stated that there are between sixty and seventy elementary
substances. An elementary substance cannot be destroyed as such. It can
be united with other elements and form chemical compounds of almost
endless variety. The smallest particle of an elementary substance is
called in chemistry an atom. The smallest particle of a compound
substance is called a molecule. The atom is the unit of the element, and
the molecule is the unit of the compound as such. It follows, then, that
there are as many different kinds of atoms as there are elements, and as
many different kinds of molecules as there are compounds. If the
elements have a molecular Structure then two or more atoms of the same
kind must combine to make a molecule of an elementary substance. Two
atoms of hydrogen combine with one of oxygen to form one molecule of
water. It cannot exist as water in any smaller quantity. If we subdivide
it, it no longer exists as water, but as the original gases from which
it was compounded.

We have shown in the series on Sound, Heat and Light that they are all
modes of motion. Sound is transmitted in longitudinal waves through air
and other material substance as vibration. Heat is a motion of the
ultimate particles or atoms of matter, and Light is a motion of the
luminiferous ether transmitted in waves that are transverse. Electricity
is also undoubtedly a mode of motion related in a peculiar way to the
atoms of the conductor.

Notice that there is a difference between conduction and radiation. The
former transmits energy by a transference of motion from atom to atom or
molecule to molecule within the body, while the latter does it by a
vibration of the ether outside--as light, radiant heat, and
electromagnetic lines of force.

For the benefit of those persons who have not read Vol. II, where the
nature of ether is discussed somewhat, let us refer to it here, as it
plays an important part in the explanation of electrical phenomena.
Ether is a tenuous and highly elastic substance that fills all
interstellar and interatomic space. It has few of the qualities of
ordinary matter. It is continuous and has no molecular structure. It
offers no perceptible resistance, and the closest-grained substances of
ordinary matter are more open to the ether than a coarse sieve is to the
finest flour. It fills all space, and, like eternity, it has no limits.
Some physicists suppose--and there is much plausibility in the
supposition--that the ether is the one substance out of which all forms
of matter come. That the atoms of matter are vortices or little
whirlpools in the ether; and that rigidity and other qualities of matter
all arise in the ether from different degrees or kinds of motion.

Electricity is not a fluid, or any form of material substance, but a
form of energy. Energy is expressed in different ways, and, while as
energy it is one and the same, we call it by different names--as heat
energy, chemical energy, electrical energy, and so on. They will all do
work, and in that respect are alike. One difficulty in explaining
electrical phenomena is the nomenclature that the science is loaded down
with. All the old names were adopted when electricity was regarded as a
fluid, hence the word "current." It is spoken of as "flowing" when it
does not flow any more than light flows.

If a man wants to write a treatise on electricity--outside of the mere
phenomena and applications--and wants to make a large book of it, he
would better tell what he does not know about it, for in that way he can
make a volume of almost any size. But if he wants to tell what it really
is, and what he really knows it is, a primer will be large enough. This
much we know--that it is one of many expressions of energy.

Chemistry teaches that heat is directly related to the atoms of matter.
Atoms of different substances differ greatly in weight. For instance,
the hydrogen atom is the unit of atomic weight, because it is the
lightest of all of them. Taking the hydrogen atom as the unit, in round
numbers the iron atom weighs as much as 56 atoms of hydrogen, copper a
little over 63, silver 108, gold 197. Heat acts upon matter according to
the number of atoms in a given space, and not as its weight. Knowing the
relative weights of the atoms of the different metals named, it would be
possible to determine by weight the dimensions of different pieces of
metal so that they will contain an equal number of atoms. If we take
pieces of iron, copper, silver and gold, each of such weight as that all
the pieces will contain the same number of atoms, and subject them to
heat till all are raised to the same temperature, it will be found that
they have all absorbed practically the same quantity of heat without
regard to the different weights of matter. It will be observed that the
piece of silver, for instance, will have to weigh nearly twice as much
as the iron in order to contain the same number of atoms, but it will
absorb the same amount of heat as the piece of iron containing the same
number of atoms, if both are raised to the same temperature. In view of
the above fact it seems that heat acts especially upon the atoms of
matter and is a peculiar form of atomic motion. Heat is one kind of
motion of the atoms, while electricity may be another form of motion of
the same. The two motions may be carried on together. The earth has a
compound motion. It revolves upon its axis once in twenty-four hours,
and it also revolves around the sun once each year. So you see that
there are different kinds of motion that may be communicated to the same
body--all producing different results.

The motion of the individual atom as heat may be, and is, as rapid as
light itself when the temperature is sufficiently high, but it does not
travel along a conductor rapidly as the electro-atomic motion will. If
we apply heat to the end of a metal rod it will travel slowly along the
rod. But if we make the rod a conductor of electricity it travels from
atom to atom with a speed nearer that of the light ray through the
ether. Some modern writers have attempted to explain all the phenomena
of electricity as having their origin in a certain play of forces upon
the ether, and there is no doubt but that the ether plays an important
part in all electrical phenomena as a medium through which energy is
transferred; but ether-waves that are set in motion by the electrical
excitation of ordinary matter are no more electricity than the
ether-waves set up by the sun in the cold regions of space are heat.
They become heat only when they strike matter. Heat, _as such_, begins
and ends in matter;--so (I believe) does electricity.

Do not be discouraged with these feeble attempts to explain the theory
of electricity. All I even hope to do is to establish in your minds this
fundamental thought, to wit, that there is really but one Energy, and
that it is always expressed by some form of motion or the ability to
create motion. Motions differ, and hence are called by different names.

If I should set an emery-wheel to revolving and hold a piece of steel
against it the piece of steel would become heated and incandescent
particles would fly off, making a brilliant display of fireworks. The
heat that has been developed is the measure of the mechanical energy
that I have used against the emery-wheel. Now, let us substitute for the
emery-wheel another wheel of the same size made of vulcanized rubber,
glass or resin. I set it to revolving at the same speed, and instead of
the piece of steel, I now hold a silk handkerchief or a catskin against
the wheel with the same force that I did the steel. If now I provide a
Leyden jar and some points to gather up the electricity that will be
produced (instead of the heat generated in the other case), it would be
found that the energy developed in the one case would exactly balance
that of the other, if it were all gathered up and put into work. The
electricity stored in the jar is in a state of strain, like a bent bow,
and will recoil, when it has a chance, with a power commensurate with
the time it has been storing and the amount of energy used in pressing
against the wheel.

If now I connect my two hands, one with the inside and the other with
the outside of the jar, this stored energy will strike me with a force
equal to all the energy I have previously expended in pressing against
the wheel, minus the loss in heat. If I did it for a long enough time
this electrical spring would be wound up to such a tension that the
recoil would destroy life if one put himself in the path of its
discharge. If all the heat in the first case were gathered up and made
to bend a stiff spring, and one should put himself in its way when
released, this mechanical spring would strike with the same power that
the electrical spring did when the Leyden jar was discharged. This
statement assumes that all the energy in the second experiment was
stored as electricity in the jar. You will be able to see from the
above illustration that heat, electrical energy, and mechanical energy
are really the same. Then you ask, how do they differ? Simply in their
phenomena--their outward manifestations.

While there is much that we cannot know about any of the phenomena of
nature, it is a great step in advance if we can establish a close
relationship between them. It helps to free electricity from many
vagaries that exist in the minds of most people regarding it; vagaries
that in ignorant minds amount to superstition. While it possesses
wonderful powers, they give it attributes that it does not possess. Not
long ago a favorite headline of the medical electrician's advertisement
was "Electricity Is Life," and it was a common thing to see
street-venders dealing out this "life" in shocking quantities to the
innocent multitudes--ten cents' worth in as many seconds.

Science divides electricity into two kinds--static and dynamic. Static
comes from a Greek word, meaning to stand, and refers to electricity as
a stationary charge. Dynamic is from the Greek word meaning power, and
refers to electricity in motion. When Franklin made his celebrated kite
experiment, the electricity came down the string, and from the key on
the end of the string he stored it in a Leyden jar. While the
electricity was moving down the string it was dynamic, but as soon as
it was stored in the Leyden jar it became static. Current electricity is
dynamic. A closed telegraphic circuit is charged dynamically, while the
prime conductor of a frictional electric machine is charged statically.
The distinction is arbitrary and in a sense a misnomer. When we rub a
piece of hard rubber with a catskin it is statically charged because the
substances are what are called non-conductors, and the charge cannot be
conducted readily away. All substances are divided into two classes, to
wit, conductors or non-electrics, and non-conductors or electrics, more
commonly called dielectrics. These, however, are relative terms, as no
substance is either a perfect conductor or a perfect non-conductor.

The metals, beginning with silver as the best, are conductors. Ebonite,
paraffine, shellac, etc., are insulators, or very poor conductors. The
best conductors offer some resistance to the passage of the current and
the best insulators conduct to some extent. If we make a comparison of
electric conductors we find that the metals that conduct heat best also
conduct electricity best. This, it seems to me, is a confirmation of the
atomic theory of electricity so far as it means anything. If a good
conductor, as silver, is subjected to intense cold by putting it into
liquid air, its conductivity is greatly increased. It is well known
that heating a conductor ordinarily diminishes its power to conduct
electricity. This shows that, in order that electrical motion of the
atom may have free play, the heat motion must be suppressed.



CHAPTER VI.

ELECTRIC CURRENTS.


The simplest form of an electric machine is one in which the operator is
a prominent part of the operation. Electricity, like magnetism, operates
in a closed circuit, even when it is static--so-called. Take a stick of
sealing-wax, say, in your left hand, and rub it with a piece of fur or
silk with your right hand, and you have the simplest form of electric
machine--the one that was known to the ancients, and the one from which
the science, great as it is to-day, had its beginnings. The stick of
sealing-wax is one element of the battery, and the piece of fur or silk
is the other, while your hands, arm and body form the conductor that
connects the two poles, and the friction is the exciting agent and may
be said to take the place of the fluid of a battery. The electrical
conditions are not wholly static, as a slow current is passing around
through your arms and body from one pole to the other. Even if the
conditions were wholly static there would be polarized lines of force,
in a state of strain, reaching around in a closed circuit.

If we rub the wax with the fur and then take it away the wax has a
charge of electricity and will attract light objects. If we had rubbed a
piece of metal or some good conductor it would have been warmed instead
of electrified. In both cases the particles of the substances have been
affected, and if the atomic theory is correct--and it seems
plausible--in the former case the atoms are partly put into electrical
motion and partly into a state of electrical strain that we call static
(standing) electricity; while in the latter case the atoms are put into
the peculiar motion that belongs to heat. The former we call
electricity, and the latter we call heat. The electro-atomic motion
under some circumstances readily turns to heat, which seems to be the
tendency of all forms of energy. The electric light is a result of this
tendency. All non-conductors, or electrics, have a complex molecular
structure, and, while their atoms when subjected to friction are put
into a state of electrostatic strain, they are not able readily to
respond as a conductor of dynamic electricity. The electric-light
filament in the incandescent lamp is a much poorer conductor than the
copper wire that leads up to it. The copper wire is readily responsive
to the electrical influence, but the carbon filament is not. So
electrical action that freely passes along the wire, is resisted and
becomes heat action in the filament, and light is the attendant of
intense heat. But, to go back to the sources of electricity.

Frictional electric machines have been constructed in great variety.
All, however, embrace the essentials set forth in the sealing-wax
experiment, and would be difficult to describe without cuts. Let us,
therefore, consider another source of electricity, which was the
outgrowth of the discovery of Galvani (or rather his wife), and reduced
to concrete form by Volta. We refer to the galvanic or voltaic battery.
If we put a bar of zinc into a glass vessel and pour sulphuric acid and
water into it, there will be a boiling, and an evolution of hydrogen
gas, and energy is released in the form of heat, so that the fluid and
the glass vessel become heated. Now let us put a bar of copper or a
stick of carbon into the glass, but not in contact with the zinc;
connect the ends (that are not immersed) of the two elements--copper and
zinc--with a metal wire or any conductor, and a new condition is set up.
Heat is no longer evolved to the same extent, but most of the energy
becomes electrical in character, and an electrical chain of action takes
place in the circuit that has now been formed. Taking the zinc as the
starting point, the so-called current flows from the zinc through the
fluid to the copper and from the copper through the wire to the zinc.

A chain of polarized atomic activity is established in the circuit,
similar to the closed circuit of magnetic lines of force, only the
latter is static, while the former is dynamic.

You ask what is the difference? Well, it is much easier to ask a
question than it is to answer it. You will remember that in the chapter
on magnetism it was stated that the molecules of a magnet were little
natural magnets, and that their attractions were satisfied within
themselves; that when their local attachments were broken up and all
their like poles turned in one direction they could act upon other
pieces of iron outside of the magnet. Outside and between the poles
there are magnetic lines of force reaching out from one pole to the
other. If we put a piece of iron across the poles these lines of force
are gathered up and pass through the iron. This is purely a static
condition. Let us go back to the cell of battery. When the elements are
in position (the copper, the acidulated water and the zinc), and the two
wires attached to the two metals which are the two poles of the battery
not yet connected, there is a condition induced in these two wires that
did not exist before the acidulated water was poured in, although the
circuit is not yet established. If we test the two wires we find a
difference of potential--a state of strain, so to speak--that did not
exist before the acid acted on the zinc and liberated what was stored
energy. It is in a static condition, like the magnet, and electrical
lines of force are reaching out from both wires so that the ether is in
a state of strain between the two poles. The air molecules may partake
of it, but we have to bring in the ether as a substance, because the
same conditions would practically exist if the two wires were in a
vacuum. If now we connect the two wires, we have established a metallic
circuit between the two poles of the battery, the static conditions are
relieved, the lines of force are gathered up into the wire, and the
phenomenon that we call a current is established and we have dynamic or
moving electricity.

Having established the so-called electric current we will now try to
show you that there really is no current. The idea of a current involves
the idea of a fluid substance flowing from one point to another. When
you were a boy did you never set up a row of bricks on their ends, just
far enough apart so that if you pushed one over they all fell one after
another? Now, imagine rows of molecules or atoms, and in your
imagination they may be arranged like the bricks, so that they are
affected one by the other successively with a rapidity that is akin to
that of light-waves, and you can conceive how a motion may be
communicated from end to end of a wire hundreds of miles in length in a
small fraction of a second, and no material substance has been carried
through the wire--only energy. We do not mean to say that the row of
bricks illustrates the exact mode of molecular or atomic motion that
takes place in a conductor. What we mean is, that in some way motion is
passed along from atom to atom.

To give you a better conception of an electric current, let us go back
of the galvanic cell to the electric machine. If both poles of the
machine are attached to rods terminating in round knobs we can set the
machine in action and keep up a steady stream of disruptive discharges
that will, if their frequency is great enough, perform the function of a
current, and we have dynamic electricity from a statical machine; when
the acid of the galvanic battery breaks down a molecule of zinc, energy
is set free, and in the battery we have what corresponds to a disruptive
discharge of infinitesimal proportions. This discharge would have been
immediately converted into heat energy if the copper element had been
left out of the battery, but as it is, it impresses itself on the atomic
"brick" next to it, which establishes a chain of atomic movement
throughout the circuit. This may constitute, if you please, a line of
electrical force. But as thousands of these disruptive discharges are
taking place simultaneously as many different lines of force are
established. You must not conceive of these chains of atoms as simply
thrown down like the bricks and left lying there, but that the atom is
active; that it has the power to pick itself up again in an
infinitesimally short time and is again knocked down (following the
illustration of the bricks) by the next discharge along its line or
chain of atoms.

If you could get a mental picture of this action you would see that the
whole conductor is in a most violent state of atomic motion of a
peculiar kind. At the same time a part of this electrical motion is
being converted into a heat motion of the atoms, and finally it all
returns to heat unless some of it is stored up somewhere as potential
energy. If the current has driven a motor that has wound up a weight, a
part is stored up in the weight, which has the ability to do work if it
is allowed to run down. If it drives machinery as it runs down, the
mechanical motion is the expression of the stored energy. When the
weight has run down the energy will be represented by the heat created
by friction of the journals of the wheels and pulleys and the heating of
the air. If the weight is allowed to fall suddenly it will heat the air
to some extent, but mostly the earth and the weight itself will be
heated. If the source of energy (the battery) is great and the pressure
high and the conductor is too small to carry the energy developed in the
battery as electricity, heat is developed, and if the heat is
sufficiently intense, light also.

We have seen (Vol. II) that heat motion when it reaches a sufficiently
high rate throws the ether into a vibratory motion that we call light.
However, this vibratory motion of the ether is set up long before it
reaches the luminous stage; in other words, there are dark rays of the
ether. We find that the electro-atomic motions of a conductor have the
power to impress themselves upon the ether.

    [Illustration: Fig. 1.

    A is the primary line; _a_, the battery: _b_, the key. B is the
    secondary line in which is placed the galvanometer _c_.]

Let us try another experiment to show that this is the case, not only,
but that the impressed ether can transfer these impressions to still
another conductor. Suppose we stretch two parallel wires for, say, half
a mile, or any distance, only a few feet apart, and make of each a
complete circuit by rounding the end of the course and returning the
wire to the starting point (as shown in Fig. 1). Put in one of these
circuits a battery, and a circuit-breaker (a common telegraph-key), and
in the other circuit a galvanometer (an instrument for detecting the
presence and measuring the intensity of a galvanic current, by means of
a dial and a deflecting needle or pointer). Now if we touch the key and
close the circuit in A, the needle of the galvanometer in B will swing
in one direction from zero on the dial; and if we release the key,
breaking the circuit in A, the needle will swing back in the opposite
direction. In neither case will the needle stay deflected, but will at
once return to zero.

This shows that when the battery current was allowed to complete its
circuit through wire A by closing its key, an electrical action was
instantly felt in wire B, although there was no material connection
between them other than the air, which is a non-conductor.

The current in the second circuit is called an induced current. Why this
current? According to one theory, when we close the primary circuit the
surrounding ether is thrown into a peculiar state of strain that we will
call magnetic or electrical lines of force. When the ether wave strikes
the second wire there is a molecular movement from a state of rest to a
state of static strain. During the time that the molecules are moving
from the normal to the strained position in sympathy with the ether we
have the condition of a dynamic current, which lasts only a moment. This
state of strain continues till the circuit is opened (breaking the
wire-line), when all the electrical lines of force vanish and the
molecular strain of the second wire is relieved, and we again have the
conditions, momentarily, for a current of the opposite polarity, and the
needle will swing in the opposite direction because the molecules or
atoms have, in their recoil to the natural state, moved in an opposite
direction.

Going back to Fig. 1, let us further study the phenomena under other
conditions. In our first circuit (A) there is a battery and a
circuit-breaker, which is a common telegraph-key. Now close the key so
that a current will be established. (Remember that "current" is only a
name for a condition of dynamic charge.) Place a piece of soft iron
across the wire at right angles with the direction of the wire, when of
course it will be at right angles with the direction of the current, and
you will find now that the iron is more or less magnetic, depending upon
the amount of current passing through the wire. If we wind a number of
turns of insulated wire through which the current is passing around the
iron the magnetism will be increased. In practice there are a certain
number of turns and a certain sized wire that will give the best results
with a given number of cells of battery (or a given voltage or
pressure), operating in a closed circuit of a given resistance. All
these questions are worked out mathematically in many standard books on
the subject. It is not the intention in these talks to develop the
science mathematically but to set out the fundamental physical facts and
applications of electricity.

Under the conditions above named magnetism is developed in the soft iron
bar. If we open the key the current will cease and the magnetism will
vanish--that is to say, the molecules will turn back to their neutral
position by their own attractions, as has been described in a previous
chapter. Magnetism developed in this way is called electromagnetism.
(See Chap. IV.) If we use a piece of hardened steel instead of the soft
iron it will become magnetic and remain so when the circuit is opened,
because the natural tendency of the molecules to turn back to the
neutral position is not great enough to overcome the coercive force, or
molecular friction, of hardened steel, as has been also described in a
previous chapter. To make the best electromagnet we need qualities of
iron just the opposite from those of the permanent magnet. For the
former we need the purest of soft iron, well annealed (heated to redness
and slowly cooled, making it less brittle), so that its molecules are
free to turn; while for the latter we need hardened steel, so that when
the molecules are once wrenched into the magnetic condition they cannot,
of themselves, turn back to the neutral state. The great value of the
electromagnet lies in its ability to readily discharge, or go back to
the neutral state, when the current is broken.

Let us now go back to the beginning of our experiment. When we closed
the key and established the current through the wire we found that a
piece of iron held at right angles to the wire, although not touching
it, became magnetic. We have already said that when the circuit was
open, the battery being in circuit, there were electrical lines of force
established in the ether, between the two poles of the battery, and that
they were gathered up into the conducting wire when the circuit was
closed. We now find that there are other lines of force of a different
nature established in the ether when the circuit is closed. These we
call magnetic lines of force, or the magnetic field of the charged wire,
and they are established at right angles to the direction of the
current. These magnetic lines of force acting through the ether from an
electrically charged conductor are able to break up the natural
molecular magnetic rings, referred to in Chapter IV, and turn all their
like poles in the same direction--thus making one compound magnet of the
iron which in the neutral state consisted of millions of little natural
magnets whose attractions were satisfied by a joining of their unlike
poles.

Most writers account for all of the phenomena of induced currents in a
second wire as coming directly from these magnetic lines of force
developed upon closing the circuit.

So much for theory based upon a set of facts that make the theory seem
probable. If you don't like it give us a better one. If it is correct
the writer claims no credit; it is merely a compilation of suggestions
from many sources, including his own experience. We are simply seeking
after truth. The man who is an earnest seeker after scientific truth
cannot afford to pursue his investigations with any prejudice in favor
of one theory more than another, unless the facts sustain him, and then
he is not acting from prejudice, but is led by the facts. Many people
make pets of their theories; and they become attached to them as they do
their children; and they look upon a man who destroys them by a
presentation of the facts as an enemy. I once knew a lady who became so
attached to her family doctor that, she said, she would rather die under
his treatment, if necessary, than to be cured by any other doctor. There
are many people who are imbued with this kind of spirit not only in
matters scientific, but in matters religious as well. Such people are
not the kind who contribute to the world's progress, but are the
hindrances that have to be overcome.



CHAPTER VII.

ELECTRIC GENERATORS.


Of the sources of electricity we have mentioned two: Friction, and
Galvanism or chemical action. There are hundreds of forms of the latter
species of apparatus for generating electrical energy, so we will
mention only a few of the more prominent ones. It is not our intention
to go into the chemistry of batteries. There are too many exhaustive
works on this subject lying on the shelves of libraries that are
accessible to all. All galvanic batteries act on one general
principle--the generation of electricity by the chemical action of acid
on metal plates; but the chemistry of their action is very different. In
all batteries the potential energy of one element is greater than the
other. The acid of the battery dissolves the element of greater
potentiality, and its energy is freed and under right conditions takes
on the form of electricity. The potential of zinc, for instance, is
greater than that of copper, and the measure of the difference is called
the "electromotive force," the unit of which is the "volt."
Electromotive force is another name for pressure; the symbol for which
is _E.M.F._

If we were to put two zinc plates in the battery fluid and connect them
in the ordinary way there would be no electricity evolved (assuming that
they were perfectly homogeneous), because they are both of the same
potential, or have the same possible amount of stored electrical energy
measured by its working power. If one of the zinc plates were softer
than the other, a feeble current would be developed, for one would be
more readily acted upon by the acids than the other. The battery that
has been most used in America for telegraphic purposes is called the
gravity-battery. It is constructed by putting a copper plate in some
form at the bottom of a jar, usually of glass, and filling it partly
full of the crystals of sulphate of copper, commonly called "bluestone."
Zinc, usually cast in some open form, so as to expose a large surface to
the solution, is suspended in the upper part of the jar, which is then
filled with water till it covers the zinc. The zinc is the positive
metal, but it is called the negative pole. The energy developed by the
zinc passes from zinc to copper and out on the circuit from the copper
pole. Hence the copper came to be called the positive pole, although in
relation to zinc it is negative. Copper would, however, be positive to
some other metal whose potential was less. So you see that metals are
relative, not absolute, in their character as positive and negative
elements.

The galvanic battery has been almost entirely superseded in this country
for telegraphic purposes by the dynamo, a machine developing electrical
currents by mechanical power. Another form of battery that is
extensively used for some kinds of heavy current work is called the
storage-battery. The man who did the most, perhaps, to bring the
storage-battery to its present state of perfection was Planté, a
Frenchman, who died only a short time ago. Although very many types of
battery have been developed, it is found that, after all, the lines on
which he developed it make the most efficient battery. There is a common
notion that electricity is stored in the storage-battery. Energy is
stored, that will produce electricity when it is set free, just the same
as energy is stored in zinc. The storage-battery, when ready for action,
is one form of acid or primary battery. It has been made by passing a
current of electricity through it until the chemical relations of the
two lead plates have been changed so that the potential of one is
greater than that of the other. A simple storage-battery element is made
up of two plates of lead held out of contact with each other by some
insulating substance the same as the elements of an ordinary battery.
The cell is filled with dilute sulphuric acid, and there will be no
electrical action till the cell has been charged by running a current of
electricity through it and forming a lead oxide on one plate. Now, take
off the charging battery and connect the two poles, and electricity will
flow until the oxide has partly changed back into spongy metallic lead,
when it must be renewed by recharging.

I remember perfectly well the first galvanic battery I ever saw, for it
was of my own construction. It is now nearly fifty years ago, and yet it
seems but yesterday--such is the flight of time. I related to you in
another chapter how I made a voltaic battery--or pile, as it was
called--by cutting up my mother's boiler and her stove-zinc, and the
domestic incident that followed. Well, a little later I made a real
galvanic battery as follows: I lived in the country and far from town or
city, and my facilities were extremely limited, so that I pursued my
scientific investigations under great difficulties. My only text-book
was an old Comstock's Philosophy. In the book was a crude cut of a Morse
register and a short description of its construction, including the
battery. I determined to make a register, and I did. It was all
constructed of wood except the magnet and its armature and the
embossing-point, which latter was made of the end of a nail. The thing
that seemed out of reach was the electromagnet. I had no money; and
there was no one that believed I could do it, and if I could "what good
would come of it?" I made friends with a blacksmith by keeping flies off
a horse while he nailed the shoes on, and "blowing the bellows" and
occasionally using the "sledge" for him. When I thought the obligation
had accumulated a sufficient "voltage" (to express it electrically) I
communicated to the blacksmith the situation and what I wanted.

The good-natured old fellow was not long in bending up a U magnet of
soft iron and forging out an armature. The next step was to wind the U
with insulated wire. The only thing that I had ever seen of the kind was
an iron wire called "bonnet" wire that was wrapped with cotton thread.
This, however, was not available, so I captured a piece of brass
bell-wire and wound strips of cotton cloth around it for insulation--and
in that way completed the magnet.

Now everything was ready but the battery. I went at its construction
with a feeling almost akin to awe, for I could not believe that it would
do as described in the book. I procured a candy-jar from the grocer and
found some pieces of sheet zinc and copper. These I rolled together into
loose spirals and placed one inside the other so that they would not
touch, when I was ready for the solution. The druggist trusted me for a
half pound of "blue vitriol," and I put it into my battery and filled it
with water. I waited awhile for it to dissolve, and then connected my
magnet in circuit, when--to my astonishment and delight--it would lift a
pound or more. It was a great triumph. I never have had one since that
gave me the same satisfaction. But I had my triumph all to myself. I was
still the same "tinker" (a name I had long carried), and a nuisance to
be endured but not encouraged.

The dynamo is the form of generator now in general use where heavy
currents of electricity are needed. It is aptly described by a writer in
Modern Machinery, Mr. John A. Grier, as a thing that when "at rest is a
lifeless piece of mechanism; in action it has a living spirit as full of
mystery as the soul of man." This is a poetic way of describing it that
conveys to the mind a sense of the power and beauty of natural law in
action, that would not come from a mere recital of the cold scientific
facts. The facts, however, are necessary: but let us draw from them all
the poetry and all the practical lessons that we can as we go along; for
it is this blending of the poetic with the practical that lends a charm
to our every-day "grind," and lightens the load of many a weary hour.

The dynamo is a machine that converts mechanical into electrical energy,
and the great practical value of energy in this form is that it can be
distributed through a conductor economically for many miles. We can
transmit mechanical power by means of a rope or cable for a limited
distance, but at tremendous loss through friction. We can transmit power
through pipes by compressed air or steam, but there is a great loss,
especially in the case of steam, by condensation from cold. None of
these methods are available for long distances. Another advantage
electricity has over other forms of energy is the speed with which it
can be transmitted from one place to another. In this respect it has no
rival except light. But we have not been able to harness light and make
it available to carry either freight or news, except in the latter case
for a short distance by flashing it in agreed signals.

The heliostat can be used when the sun shines to transmit news by
flashes of sunlight chopped up into the Morse code and thrown from point
to point by a moving mirror. But this is limited as to distance;
besides, the sun does not always shine. It has the disadvantage in that
respect that the old semaphore-telegraph did that was in use in
Wellington's day. These semaphores were constructed in various ways, but
a common form was that of moving arms that could be seen from hill to
hill or point to point. By a code of moving signals news was repeated
from point to point and it can be easily imagined that many mistakes
occurred, to say nothing of the time it required for repetition. When
the battle of Waterloo was fought--so the story goes--news was sent to
England by means of the semaphore-telegraph. The dispatch read,
"Wellington defeated--" At that point in the message a thick fog came up
and lasted for three days, so that no further news could be sent or
received. In the telegraphic parlance of to-day the line was "busted."
For three long days all London was in deep mourning, when finally the
fog lifted, which repaired the telegraphic line, and the balance of the
dispatch was received--"the French at Waterloo." Mourning changed to
rejoicing and the English have rejoiced ever since when they think of
either Wellington or Waterloo.

But to return to the dynamo. The name dynamo is an abbreviation for
dynamo-electric machine. A machine for producing dynamic electricity.
There are many forms of the dynamo, just as there are in the evolution
of every important machine, and there will be many more. But the
fundamental, underlying principle of them all is contained in an
experiment made by Faraday. Faraday took the soft iron "keeper" of a
permanent magnet and wound insulated wire around it and brought the two
ends of the wire close together. He now placed the keeper, with the
wire wound around it, across the poles of the permanent magnet, and
wrenched it away suddenly, when he observed a spark pass between the
ends of the wires. This would occur when he approached the poles as well
as when he took it away. He discovered that the currents were momentary
and occurred at the moment of approach or recession, and that the
currents developed by the approach were of opposite polarity to those
occurring at the recession. When the "keeper" was put on the poles of
the magnet it was magnetized by having its molecular rings broken up and
the poles of the little natural magnets all turned in one direction.
During the time that the molecules of the keeper are changing they are
in a dynamic or moving condition. By some mysterious action of the ether
between the iron and the wire wrapped around it there is a corresponding
molecular action in the wire that is dynamic for a moment only, and
during that moment we have the phenomenon of an electric current. When
the magnet and soft iron are separated this molecular state of strain is
relieved and the molecules of both the iron and the wire wound about it
return to normal, and in the act of returning we have a dynamic or
moving condition, resulting in a current, only in the opposite
direction. (See Chap. VI.)

Now mount the permanent magnet in a frame and mount the soft iron with
the wire on it (which in this shape is an electromagnet) on a revolving
arm and so set it on the arm that its ends will come close to, but not
touch, the poles of the permanent magnet. Now revolve the arm, and every
time the electromagnet or keeper approaches the permanent magnet a
current of one polarity will be momentarily developed in the wire of the
electromagnet, which is moving. When it is opposite the poles, it has
reached the maximum charge and, now, as it passes on it discharges and a
current of the opposite polarity is developed in the wire. The more
rapidly we revolve the arm the more voltage (electrical pressure) the
current it develops will have.

It will be plain to all that we might make the electromagnet stationary
and revolve the permanent magnet and get the same result. If the
permanent magnet were strong enough and the electromagnet the right size
as to iron, windings, etc., and we revolve the arm with sufficient
rapidity, we could get an alternating current of electricity that would
produce an electric light. I have not and cannot here give you the
construction of a modern alternating-current dynamo. I have simply
described the simplest form of dynamo, and all of them operate upon the
fundamental principle of a permanent magnetic field and an
electromagnet, moving in a certain relation to each other. The field
may revolve or the electromagnet may revolve, whichever is the most
convenient to construct. The field-magnet may be a permanent magnet or
an electromagnet, made permanent during the operation of the dynamo by a
part of the current generated by the machine being directed through a
coil surrounding soft iron; or the field-current may come from an
outside source. This is the kind of field-magnet universally used for
dynamo work, as a much stronger magnetism is developed in this way than
it is possible to obtain from any system of permanent steel magnets.

The usual construction is to have a stationary field-magnet and then a
series of electromagnets mounted and revolving upon a shaft in the
center of the magnetic field. The rotating part is called the armature,
and is so wound with insulated wire that successive induced currents are
created in the armature windings and discharged through brushes which
rest on revolving segments that connect with the armature windings.
These induced currents succeed each other with such rapidity as to
amount in practice to a steady current. However, the separate pulsations
are easily heard in any telephone when the circuit is near to that of a
dynamo circuit. The dynamo current is not nearly so steady as the
battery current, although both are probably made up of separate
discharges. In the dynamo there is a discharge every time the
electromagnet of the armature cuts through the lines of force of the
magnetic field, and in the galvanic battery every time a molecule is
broken up and its little measure of energy is set free. In the dynamo
the pulsations are so far apart as to make a musical tone of not very
high pitch, but in the galvanic battery the pitch of the tone, if there
is one, would require a special ear to hear it--one tuned, it may be, up
near the rate of light vibration.

There are two types of dynamo, one generating a direct and the other an
alternating current. (By alternating we mean first a positive and then a
negative current impulse.) We cannot enter into a technical description
of the dynamo in a popular treatise such as this.

The dynamo has evolved from the germ discovered by Faraday, till to-day
it is a machine, the construction of which requires the highest class of
engineering skill. When in action it seems like a great living presence,
scattering its energy in every direction in a way that is at once a
marvel and a blessing to mankind. But we must not give all the credit to
the dynamo. As the moon shines with a reflected light, so the dynamo
gives off energy by a power delegated to it by the steam-engine that
rotates it, and the steam-engine owes its life to the burning coal, and
the burning coal is only giving up an energy that was stored ages ago
by the magic of the sunbeam; and the sun--? Well, we are getting close
on to the borders of theology, and being only scientists we had better
stop with the sun.

There is still another way of generating electricity besides those that
we have named; which are friction, chemical action, and the
magneto-electric mode of generating a current. Electricity may be
generated by heat. If we connect antimony and bismuth bars together and
apply heat at the junction of the metals and then connect the free ends
of the two bars to a galvanometer, it will indicate a current. These
pairs can be multiplied, and in this way increase the voltage or
pressure, and, of course, increase the current, if we assume that there
is resistance in the circuit to be overcome. If there were absolutely no
resistance in the circuit--a condition we never find--there would be no
advantage in adding on elements in series.

Substances differ in their resistance to the passage of electricity--the
less the resistance the better the conductor. The German electrician, G.
S. Ohm (1789-1854), investigated this and propounded a law upon which
the unit for resistances is based, and this unit takes his name and is
called the "ohm."

Any two metals having a difference of potential will give the phenomena
of thermo-electricity. Antimony and bismuth having a great difference
of potential are commonly used. The use made of thermal currents is
chiefly for determining slight differences of temperature. An apparatus
called the thermo-electric pile has been constructed out of a great
number of pairs of antimony and bismuth bars. This instrument in
connection with a galvanometer makes a most delicate means of
determining slight changes of temperature. If one face of a thermopile
is exposed to a temperature greater than its own, the needle will move
in one direction; if to a temperature lower than its own, the needle
will be deflected in the opposite direction. If both faces of the pile
are exposed to the same changes of temperature simultaneously, of course
no electrical manifestations will occur.

The earth is undoubtedly a great thermal battery that is kept in action
by the constant changes of temperature going on at the earth's surface,
caused by its rotation every twenty-four hours on its axis. The sun, of
course, is at some point heating the earth, which at other points is
cooling, making a constant change of potential between different points.
If we heat a metal ring at one point a current of electricity will flow
around it--especially if it is made of two dissimilar metals--until the
heat is equally distributed throughout the ring.

Some years ago, when the Postal Telegraph Company first began operations
between New York and Chicago, the writer made observations twice a day
for some time of the temperature and direction of the earth-current. The
first two wires constructed gave only two ohms resistance to the mile,
which facilitated the experiments. I found that in almost every instance
the current flowed from the point of higher temperature to the lower. If
the temperature in New York were higher at the time of observations than
in Chicago the current would flow westward, and if the conditions were
reversed the current would be reversed also.



CHAPTER VIII.

ATMOSPHERIC ELECTRICITY.


Nature has another mode of generating electricity, called atmospheric.
The normal conditions of potential between the earth and the upper
atmosphere seem to be that the atmosphere is positively electrified and
the earth negatively. These conditions change, apparently from local
causes, for short periods during storms. In some way the sun's rays have
the power directly or indirectly to give the globules of moisture in the
air a potential different from that of the earth.

In clear weather we find the air near to the earth in a neutral
condition, but gradually assuming the condition of a positive charge as
we ascend; so that the upper air and the earth are oppositely charged
like the two sides of a Leyden jar or two leaves of a condenser. This
condition is intensified and localized when a thunder-cloud passes over
the earth. The moisture globules have been charged with potential energy
by the power of the sun's rays when evaporation took place; but in this
state the energy is neither heat nor electricity, but a state of strain
like a bent bow or a wound-up spring. When these moisture globules
condense into drops of water the potential energy is set free and
becomes active either as heat or electricity. The cloud gathers up the
energy into a condensed form, and when the tension gets too great a
discharge takes place between the cloud and the earth or from one cloud
to another, which to an extent equalizes the energy.

In most cases of thunder and lightning it is only a discharge from cloud
to cloud unequally charged. This does not relieve the tension between
the earth and the cloud, but distributes it over a larger area. The
reason for this constant electrical difference between the earth and the
upper regions of atmosphere is not well understood, except that
primarily it is an effect of the sun's rays. Evaporation may and
probably does play a part, and the same causes that give rise to the
auroral display may contribute in some way to the same result.
Evaporation does not always take place at the earth's surface. Cloud
formations may be evaporated in the upper air into invisible moisture
spherules, and charged at the time with potential energy. If we go up
into a high mountain when the conditions are right, we can witness the
effect of this condition of electrical charge or strain between the
upper regions of the atmosphere and the earth, and the tendency to
equalize the potentials between the clouds and the earth. Often one's
hair will stand on end, not from fright, but from electricity passing
down from the upper regions to the earth. When the tension is very great
a loud hissing sound as of many musical tones of not very good quality
may be heard, and a brush or fine-pointed radiation of electricity may
be seen from every point, even from your finger-ends. The thunder is not
usually so loud on high mountains for two reasons--one because the air
is rare, but the chief reason is that the mountain acts as a great
lightning-rod and gradually discharges the cloud or atmosphere, for
often the phenomena may occur when the sky is clear.

I remember being on top of what is called the Mosquito Range, between
Alma and Leadville in Colorado, during the passage of a thunder shower.
There was no heavy thunder, but a constant fusillade of snapping sounds,
accompanied by flashes not very intense. I could feel the shocks, but
not painfully. A part of the time I was in the cloud and became for the
time being a veritable lightning-rod. After the cloud passed it crawled
down the mountainside as if clinging to it, all the time bombarding it
with little electric missiles. After the cloud left the mountain and
passed over the valley I could hear loud thunder, because the charge
would have to accumulate quite a quantity, so to speak, before it could
discharge. These heavy discharges when the cloud is some distance from
the earth would be dangerous to life, while the light ones, when the
cloud is in contact with the earth, are not.

Many wonderful and destructive effects come from these lightning
discharges and many lives are lost every year from this cause. I do not
suppose it is possible to be on one's guard continually, but many lives
are needlessly lost either from ignorance or carelessness. Although
there is a just prejudice against lightning-rods as ordinarily
constructed, it is still just as possible to protect your house and its
inmates from the destroying effects of lightning as from rain. If, for
instance, we lived in metal houses that had perfect contact all round
them with moist earth, or better, with a water-pipe that has a large
surface contact with the earth, the lightning would never hurt the house
or the inmates. In such a case you simply carry the surface of the earth
to the top of your house, electrically speaking, and neutralization
takes place there in case the lightning strikes the house. A house that
is heated with hot water can easily be made lightning-proof by a little
work at the top and bottom of the heating system. All the heavy metal of
the house should be a part of the lightning-rod. Points should be
erected at the chimneys, and if there is a metal roof they should be
connected with it. Then connect the roof with rods from several points
with the ground. Here is where most rods fail. The ground connection is
not sufficient. The earth is a poor conductor, and we have to make up by
having a large metal surface in contact with it. It is best to have the
rod connected with the water pipe, if there is one, and have it
connected with metal running all around the house as low down as the
bottom of the cellar, for sometimes there is an upward stroke, and you
never can tell where it is coming up. If you have a heating system it
should be thoroughly grounded and the top pipe connected with the rods
at the chimneys. These rods need not be insulated as is the usual
practice.

If you are outdoors during a thunder-storm never get under a tree, but
if you are twenty or thirty feet away it may save your life, because, if
it comes near enough to strike you, it will probably take the tree in
preference. It seeks the earth by the easiest passage. An oil-tank and a
barn are dangerous places, if the one has oil in it and the other is
filled with hay and grain. A column of gas is rising that acts as a
conductor for lightning. Of course if the barn is properly protected
with rods it will be safe. Sometimes a cloud is so heavily charged that
the lightning comes down like an avalanche, and in such a case the rods
must have great capacity and be close together to fully protect a
building.

There is a popular notion that rods draw the lightning and increase the
damage rather than otherwise. This is a mistake. Points will draw off
electricity from a charged body silently. It would be possible to so
protect a district of any size in such a way that thunder would never be
heard within its boundaries if we should erect rods enough and run them
high enough into the upper air. The points--if they were close enough
together--would silently draw off the electricity from a cloud as fast
as it formed, and thus effectually prevent any disruptive discharge from
taking place.



CHAPTER IX.

ELECTRICAL MEASUREMENT.


Having given a short account of some of the sources of electricity, let
us now proceed to describe some of the practical uses to which it is
put, and at the same time describe the operation of the appliances used.
Before proceeding further, however, we ought to tell how electricity is
measured. We have pounds for weight, feet and inches for lineal measure,
and pints, quarts, gallons, pecks and bushels for liquid and dry
measure, and we also have ohms, volts, ampères and ampère-hours for
electricity.

When a current of electricity flows through a conductor the conductor
resists its flow more or less according to the quality and size of the
conductor. Silver and copper are good conductors. Silver is better than
copper. Calling silver 100, copper will be only 73. If we have a mile of
silver wire and a mile of iron wire and want the iron wire to carry as
much electricity as the silver and have the same battery for both, we
will have to make the iron wire over seven times as large. That is, the
area of a cross-section of the iron wire must be over seven times that
of the silver wire. But if we want to keep both wires the same size and
still force the same amount of current through each we must increase the
pressure of the battery connected with the iron wire. We measure this
pressure by a unit called the "volt," named for Volta, the inventor or
discoverer of the voltaic battery. The volt is the unit of pressure or
electromotive force. (In all these cases a "unit" is a certain amount or
quantity--as of resistance, electromotive force, etc.--fixed upon as a
standard for measuring other amounts of the same kind.)

The iron wire offers a resistance that is about seven times greater than
silver to the passage of the current. To illustrate by water pressure:
If we should have two columns of water, and a hole at the bottom of each
column, one of them seven times larger than the other, the water would
run out much faster from the larger hole if the columns were the same
height. Now, if we keep the column with the larger hole at a fixed
height a certain amount of water will flow through per second. If we
raise the height of the column having the small hole we shall reach a
point after a time when there will be as much water flow through the
small hole per second as there is flowing through the large hole. This
result has been accomplished by increasing the pressure. So, we can
accomplish a similar result in passing electricity through an iron wire
at the same rate it flows through a silver wire of the same size, by
increasing the pressure, or electromotive power; and this is called
increasing the voltage.

The quality of the iron wire that prevents the same amount of current
from flowing through it as the silver is called its resistance. The unit
of resistance, as mentioned in the last chapter, is called the ohm, and
the more ohms there are in a wire as compared with another, the more
volts we have to put into the battery to get the same current.

The unit for measuring the current is called the "ampère," named after
the French electrician, A. M. Ampère (1789-1836).

Now, to make practical application of these units. The volt is the
potential or pressure of one cell of battery called a standard cell,
made in a certain way. The electromotive force of one cell of a Daniell
battery is about one volt. One ohm is the resistance offered to the
passage of a current having one volt pressure by a column of mercury one
millimeter in cross-section and 106.3 centimeters in length. Ordinary
iron telegraph-wire measures about thirteen ohms to the mile. Now
connect our standard cell--one volt--through one ohm resistance and we
have a current of one ampère. Unit electromotive force (volt) through
unit resistance (ohm) gives unit of current (ampère). It is not the
intention to treat the subject mathematically, but I will give you a
simple formula for finding the amount of current if you know the
resistance and the voltage. The electromotive force divided by the
resistance gives the current. C = E/R or current (ampères) equals
electromotive force (volts) divided by the resistance (ohms).

But still further: One ampère of current having one volt pressure will
develop one watt of power, which is equal to 1/746 of a horse-power.
(The watt is named in honor of James Watt, the Scottish inventor of the
steam-engine--1786-1813). In other words, 746 watts equal one
horse-power. By multiplying volts and ampères together we get watts.

If we want to carry only a small current for a long distance we do not
need to use large cells, but many of them. We increase the pressure or
voltage by increasing the number of cells set up in series. If we have a
wire of given length and resistance and find we need 100 volts to force
the right amount or strength of current through it, and the
electromotive force of the cells we are using is one volt each, it will
require 100 cells. If we have a battery that has an E. M. F. of two
volts to the cell, as the storage-battery has, fifty cells would
answer. If we want a very strong current of great volume, so to speak,
for electric light or power, and use a galvanic battery, we should have
to have cells of large surface and lower resistance both inside and
outside the cells.

When dynamos are used they are so constructed that a given number of
revolutions per minute will give the right voltage. In fact, the dynamo
has to be built for the amount of current that must be delivered through
a given resistance. The same holds good for a dynamo as for a galvanic
battery. If any one factor is fixed, we must adapt the others to that
one in order to get the result we want. There are many other units, but
to introduce them here would only confuse the reader. The advanced
student is referred to the text-books.

With this much as a preliminary we are prepared to take up the
applications of electricity, which to most people will be more
interesting than what has gone before.



CHAPTER X.

THE ELECTRIC TELEGRAPH.


In the year 1617 Strada, an Italian Jesuit, proposed to telegraph news
without wires by means of two sympathetic needles made of loadstone so
balanced that when one was turned the other would turn with it. Each
needle was to have a dial with the letters on it. This would have been
very nice if it had only worked, but it was not based on any known law
of nature.

Many attempts at telegraphing with electricity were made by different
people during the eighteenth century. About 1748 Franklin succeeded in
firing spirits by means of a wire across the Schuylkill River, using, as
all the other experimenters had done, frictional electricity. In 1753 an
anonymous letter was written to Scott's Magazine describing a method by
which it was possible to communicate at a distance by electricity. The
writer proposed the use of a wire for each letter of the alphabet, that
should terminate in pith balls at the receiving end, and under the balls
were to be strips of paper corresponding to the letters of the
alphabet. The message was to be sent by discharging static electricity
through the wire corresponding to the first letter of a word when the
paper would be attracted to the pith ball and read by the observer. Then
the wire corresponding to the second letter of the word was to be
charged in like manner, and so on till the whole message was spelled
out. This was the first practical (i.e., possible) suggestion for a
telegraph. The writer also proposed to have the wires strung on
insulators, which was a great advance over the other attempts.

The communication was anonymous, as no doubt, like many others, the
author feared the ridicule of his neighbors. It requires a vast amount
of moral courage to stand up before the world and openly advocate some
new theory that has never come within the experience of any one before.
It requires much now, but it required more then; for a man in those days
would have been roasted for what in these days he would be toasted. The
rank and file of humanity have been opposed to innovations in all ages,
but no progress could have been made without innovations. There always
has to be a first time. Galileo is said to have been forced to retract,
on his knees, some theory he advanced about the motion of the earth, and
its relation to the sun and other heavenly bodies. Notwithstanding this
retraction the seed-thought sown by Galileo took root in other minds,
which led to the triumph of scientific truth over religious fanaticism.

The writer in Scott's Magazine did not have the opportunity to put his
ideas into practice, so the glory of the invention fell to others. Such
men as this unknown writer are made of finer stuff, and they stand alone
on the frontier of progress. They do not fear the bullets of an enemy
half so much as the gibes of a friend. Much of their work is done
quietly and without notice, and when something of real importance is
worked out theoretically and experimentally, some one seizes upon it and
proclaims it from the housetops and attaches to it his name; but perhaps
years after the real inventor (the man who taught the so-called inventor
how to do it) is dead, some one writes a book that reveals the truth,
and then the hero-loving people erect a monument to his memory.

Such a man was our own Professor Joseph Henry, so long the presiding
genius at the Smithsonian Institution at Washington. He worked out all
the problems of the present American telegraphic system and demonstrated
it practically. Everything that made the so-called Morse telegraph a
success had long before been described and demonstrated by Henry. Yet
with the modest grace that was ingrained in the man he yielded all to
the one who was instrumental in constructing the first telegraph line
between Baltimore and Washington. Great credit is due to such men as
Morse and Cyrus W. Field--neither of them inventors, but promoters of
great systems of communication that are of unspeakable benefit to
mankind. Henry pointed out the way, and Morse carried it into effect.
Morse has had no more credit than was due him, but has Henry had as much
as is due him? No great invention was ever yet the work, wholly, of one
man. We Americans are too apt to forget this.

I shall always remember Henry as a most unassuming, kindly, genial man,
and I shall never forget his kindness to me. In 1874 I began my
researches in telephony, having applied for a patent for an apparatus
for transmitting musical tones telegraphically. This consisted of a
means of transmitting musical tones through a wire and reproducing them
on a metal plate (stretched on the body of a violin to give it
resonance) by rubbing the plate with the hand--the latter being a part
of the circuit. The examiner refused the application at first on the
ground that the inventor or operator could not be a part of his machine.
I took my apparatus and went to Washington, first calling upon Professor
Henry, never having met him before. He received me most kindly, and
allowed me to string wires from room to room in the institute, and when
he had witnessed the experiments he seemed as delighted as a child. I
now brought the patent office official over to the Smithsonian and soon
convinced him that the inventor could be a part of his own machine.

The same year I went abroad, and Henry gave me a letter to Tyndall. It
was very fortunate for me that he did, for Tyndall was very shy at
first, and it was only Henry's letter that gave me a hearing for a
moment. The history of the few days that followed this first interview
with Tyndall at the Royal Institution would make very interesting
reading, if I felt at liberty to publish it. Suffice it to say that he
was convinced in a few minutes after he had reached the experimental
stage that not all my work had been anticipated by Wheatstone, as he
asserted before seeing the experiments. Wheatstone had transmitted the
tones of a piano, mechanically, from one room to another by a wooden rod
placed upon the sound-board and terminating in another room in contact
with another sound-board. But this was very different from transmitting
musical tones and melodies from one city to another through a wire, as I
could do with my electrotelephonic apparatus.

It is a curious fact that the world is divided into two great classes,
leaders and followers. Or we might say, originators and copyists; the
former division being very small, while the latter is very large. As
late as 1820 the European philosophers were trying to construct a
telegraphic system based upon two ideas, announced a long time before,
to wit, the use of static or frictional electricity, and a wire for
every letter. It does not seem to have occurred to any one to devise a
code consisting of motions differently related as to time, and to use
simply one wire.

In 1819 Oersted discovered the effect of a galvanic current on a
magnetic needle, and published a pamphlet concerning his discovery. This
stimulated others, and Ampère applied it to the galvanometer the same
year. Arago applied it to soft iron, and here was the germ of the
electromagnet. We see that as far back as 1820 we had the galvanic
battery and the electromagnet, the two great essentials of the modern
telegraph.

However, there remained another great discovery to be made before these
elements could be utilized for telegraphic purposes. One cell of battery
was used, and the magnet was made by winding one layer of wire spirally
around the iron, so that each spiral was out of touch with its neighbor.
Barlow of England, a Fellow of the Royal Society, tried the effect of a
current through a wire 200 feet long, and found that the power was so
diminished that he was discouraged, and in a paper gave it as his
opinion that galvanism was of no use for telegraphing at a distance.
This paper stimulated others, and it was reserved for our own Joseph
Henry, already referred to, to show not only how to construct a magnet
for long-distance telegraphy, but also how to adapt the battery to the
distance. He showed us that by insulating the wire and using several
layers of whirls, instead of one, and by using enough cells of battery
coupled up in series to get more voltage, as we now express it, it was
possible to transmit signals to a distance. He not only set forth the
theory, but he constructed a line of bell-wire 1060 feet long and worked
his magnet by making the armature strike a bell for the signals, which
is the basis of the modern "sounder."

Nothing was needed but to construct a line and devise a code to be read
by sound, to have practically our modern Morse telegraph. This line was
constructed in 1831. In 1835 Henry, who was then at Princeton,
constructed a line and worked it as it is to-day worked, with a relay
and local circuit, so that at that period all the problems had been
worked out. But, like the speaking-telephone in its early inception, no
one appreciated its real importance. Henry himself did not think it
worth while to take out a patent. Two years later the Secretary of the
Treasury sent out a circular letter of inquiry to know if some system of
telegraphic communication could not be devised. The learned heads of
the Franklin Institute of Philadelphia, the oldest scientific society in
America, advised that a semaphore system be established between New York
and Washington, consisting of forty towers with swinging arms, the same
as used in the days of Wellington. Among other replies to the circular
letter of the secretary was one from Samuel F. B. Morse. Morse was not a
scientist or even an inventor, at least not at that time. He was an
artist of some note. In 1832, while crossing the ocean, Morse, in
connection with one Dr. Jackson of Boston, devised a code of telegraphic
signs intended to be used in a chemical telegraph system.

Some years later Morse adapted Henry's signal-instrument to a recorder,
called the Morse register, and this was the instrument used in the early
days of the Morse telegraph.

What Morse seems to have really invented was the register, which made
embossed marks on a strip of paper, and the code of dots and dashes
representing letters, now known as the Morse alphabet, although this
latter is questioned. Morse took his apparatus to Washington and
exhibited it to the members of Congress in the year 1838, but it was
four years before a bill was passed that enabled him to try the
experiment between Baltimore and Washington. We will let him describe in
his own words the closing day of Congress. He says:

"My bill had indeed passed the House of Representatives and it was on
the calendar of the Senate, but the evening of the last day had
commenced with more than 100 bills to be considered and passed upon
before mine could be reached. Wearied out with the anxiety of suspense,
I consulted one of my senatorial friends. He thought the chance of
reaching it to be so small that he advised me to consider it as lost. In
a state of mind which I must leave you to imagine, I returned to my
lodgings to make preparations for returning home the next day. My funds
were reduced to the fraction of a dollar. In the morning, as I was about
to sit down to breakfast, the servant announced that a young lady
desired to see me in the parlor. It was the daughter of my excellent
friend and college classmate, the commissioner of patents, Henry L.
Ellsworth. She had called, she said, by her father's permission, and in
the exuberance of her own joy, to announce to me the passage of my
telegraph bill at midnight, but a moment before the Senate adjourned.
This was the turning-point of the telegraph invention in America. As an
appropriate acknowledgment of the young lady's sympathy and kindness--a
sympathy which only a woman can feel and express--I promised that the
first dispatch by the first line of telegraph from Washington to
Baltimore should be indited by her; to which she replied: 'Remember,
now, I shall hold you to your word.' About a year from that time the
line was completed, and, everything being prepared, I apprised my young
friend of the fact. A note from her inclosed this dispatch: 'What hath
God wrought?' These were the first words that passed on the first
completed line in America."

The first telegraph-line in America was put into operation in the spring
of 1844 at the beginning of Polk's administration. I remember as a boy
having the two cities, Baltimore and Washington, pointed out to me on
the map, and how the story of the telegraph impressed me. Congress
appropriated $30,000 for the construction of the line, and $8000 to keep
it running the first year. It was placed under the control of the
postmaster-general, and the line was thrown open to the public. The
tariff was fixed at one cent for every four words. It was open for
business on April 1, 1844, and for the first few days the revenue was
exceedingly small. On the morning of the first day a gentleman came in
and wanted to "see it work." The operator told him that he would be glad
to show it at the regular tariff of one cent for four words. The
gentleman grew angry and said that he was influential with the
administration, and that if he did not show him the working free of
charge he would see to it that he lost his job. His bluff did not
succeed. The operator referred him to the postmaster-general, and thus
the stormy interview ended. No patrons came in for the next three days,
but a great number stood around hoping to see the instrument start up,
but no one was willing to invest a cent--probably from fear of being
laughed at.

On the fourth day the same gentleman who had threatened the young man
with dismissal came back and invested a cent, and this was the first and
only revenue for four days. The message that was sent only came to
one-half cent, but as the operator could not make change the stranger
laid down the cent and departed. His name ought to be known to fame as
the first man patron of the telegraph.

    [Illustration: Fig. 2.

    A gives a diagram view of a Morse telegraph-line with three
    stations. B is the battery; C C C, the transmitting keys in the
    three offices; D D D, the relay magnets; E E E, the armatures
    that are actuated by the magnets.]

The operation of the Morse telegraph is very simple if we grant all that
has gone before. All that is needed is the wire, the battery, and the
key, as shown in Fig. 2 (page 99), and a relay--an extra electromagnet
which receives the electric current and by its means puts into or out of
action a small local battery on a short circuit in which is placed the
receiving or recording apparatus. Thus we have a wire starting from the
earth in New York and passing through a battery, a key and a relay, and
thence to Boston on poles, with insulators on which the wire is strung,
and through another instrument, key and battery in Boston, the same as
at the New York end, and into the ground, leaving the earth to complete
one-half of the circuit. When the keys at both ends are closed the
batteries are active and the armatures or "keepers" are attracted so
that the armature levers rest on the forward stops. (See diagram Fig.
2.) If either one of the keys is opened the current stops flowing and
the magnetism vanishes from all the electromagnets on the line, and a
spring or retractile of some kind pulls the armatures away from the
magnets and the levers rest on their back stops. In this way all the
levers of all the magnets are made to follow the motions of any key. If
there are more than two magnets in circuit (and there may be twenty or
more) they all respond in unison to the working of one key, so that when
any one station is sending a dispatch all the other stations get it.

But there is a "call" for each office, so that the operator only heeds
the instrument when he hears his own call. Operators become so expert in
reading by sound that they may lie down and sleep in the room, and,
although the instrument is rattling away all the time, he does not hear
it till his own call is made, when he immediately awakes.

In the old days messages were received on slips of paper by the Morse
register by means of dots and dashes. Gradually the operator learned to
read by sound, till now this mode of receiving is almost universal the
world over. Reading by sound was of American origin. It is a spoken
language, and when one becomes accustomed to it it is like any other
language. This code language has some advantages over articulate speech,
as well as many disadvantages. A gentleman who was connected with a
Louisville telegraph office told me that one of the best operators he
ever knew was as deaf as a post. He would receive the message by holding
his knee against the leg of the table upon which the sounder was
mounted, and through the sense of feeling receive the long and short
vibrations of the table, and by this means read as well or better than
through the ear, because he was not distracted by other sounds.

A story is told of the late General Stager that at one time he was on a
train that was wrecked at some distance from any station. He climbed a
telegraph pole, cut the wire and by alternately joining and separating
the ends sent a message, detailing the story of the wreck, to
headquarters, and asked for assistance. He then held the two ends of the
wire on each side of his tongue and tasted out the reply--that help was
coming. Any one who has ever tasted a current knows that it is very
pronounced.

A story similar to this is told of the early days when the Bain chemical
system was used between Washington City and some other point. This
system made marks on chemically-prepared paper; as the current passed
through it left marks on the paper from the decomposition of the
chemicals. Some of the preparations emitted an odor during the time that
the current passed. The occurrence to which we refer took place at
presidential election time. At some station out of Washington an
operator was employed who had a blind sister, and this sister knew the
Morse alphabet well before she became blind. One evening a signal came
to get ready for a message containing the returns from the election. In
the hurry, and just as the message had started, the lamp was upset and
they were in total darkness--at least, the brother was. The sister, poor
girl, had been in darkness a long time. The blind sister leaned over the
stylus through which the current flowed to the paper and smelled out as
well as spelled out the message, and repeated it to her astonished
brother.

By the old semaphore system the motions were sensed through the eye as
well as the early method of cable signaling. It will be seen from the
above that the Morse code may be communicated through any one of the
five senses.



CHAPTER XI.

RECEIVING MESSAGES.


With but few exceptions the Morse code is the one almost universally
used the world over. As it is used in Europe, it is slightly changed
from our American code, but they all depend upon dots, dashes, and
spaces, related in different combinations, for the different letters.
Notwithstanding its universal use it is not free from serious
difficulties in transmission unless it is repeated back to the sender
for correction; and then in some cases it is impossible to be sure,
owing to difficulties of punctuation and capitalizing, and the further
difficulty of running the signals together, caused, it may be, by faulty
transmission, induced currents from other wires, "swinging crosses" or
atmospheric electricity. Sometimes it is a psychological difficulty in
the mind of the receiving-operator. The telegraph companies have to
suffer damages from all these and many other unforeseen causes.

Prescott tells some curious things that happened in the early days,
growing out of the peculiarities of the receiving-operator. At one time
he was reporting by telegraph one of Webster's speeches made at Albany
in 1852 in which there were many pithy interrogative sentences, and he
was desirous of having the interrogation-points appear. So to make sure,
whenever he wished an interrogation-point he said "question" at the end
of almost every sentence. Next day he was horrified on reading the
speech to see the ends of the sentences bristling with the word
"question."

Some time back in the fifties a gentleman in Boston telegraphed to a
house in New York to "forward sample forks by express." The message when
received by the New York merchant read: "Forward sample for K. S. by
express." The New York merchant did not know who K. S. was, nor did he
gather from the dispatch what kind of sample he wanted. So he went to
the telegraph office to have the matter cleared up. The Boston operator
repeated the message, saying "sample forks." "That's the way I received
it and so delivered it--sample for K. S.," said New York. "But," says
Boston, "I did not say for K. S.; I said f-o-r-k-s." New York had read
it wrong in the start and could not get it any other way. "What a fool
that Boston fellow is. He says he did not say for K. S., but for K. S."
Boston had to resort to the United States mail before the mystery was
solved.

Curiously enough, the old method of recording the dots and dashes on
the paper strip was not so reliable as the present mode of reading by
sound. A man can put his individuality to some extent into a sounder,
and when one becomes used to his style it is much easier to read him
accurately by sound than by the paper impressions. Some people never
could learn to read either by paper or sound. An instance of this kind
is given of a middle-aged man who was employed by a railroad company as
depot master and telegraph operator, in the old days of the paper strip.
One day he rushed out and hailed the conductor of a train that had just
pulled into the station, and told him that ---- train had broken both
driving-wheels and was badly smashed up. The conductor could read the
mystic symbols, so he took the tape and deciphered the dispatch as
follows: "Ask the conductor of the Boston train to examine carefully the
connecting-rods of both driving-wheels, and if not in good condition to
await orders." It is further related of this same operator that when he
got into real difficulty with his "tape" he used to run over to the
regular commercial office to have his messages translated. One day he
rushed into his neighbor's office trailing the tape behind him and
saying: "I am sure an awful accident has happened by the way the message
was rattled off." A playful dog had torn off a large part of the strip
as it trailed along, so only a part was left. It read, "Good morning,
Uncle Ben. When are you----" The dog had swallowed the balance of the
dispatch.

Sometimes the Morse code is not only funny but disastrous. A gentleman
wanted to borrow money of some capitalists who, not knowing his
financial standing, telegraphed to a banker who they knew could post
them. They received an answer, "Note good for large amount." The
gentleman borrowed a "large amount," but afterward when it came to be
investigated it was found that the dispatch was originally written
"not," instead of "note," which made "all the difference in the world."

It has been stated that any one of the five senses may be called into
service to interpret the Morse code into words and ideas. A story is
told by Mr. Prescott that he says is true, as he knew the party. A
friend of his, by name Langenzunge, who knew the Morse code, had served
under General Taylor (who at this time was President) at Palo Alto, in
Mexico. The general had just promised him an office; soon after he left
Washington for the west over the Baltimore and Ohio on a freight train;
the President was taken seriously ill, and his friend hearing of it was
troubled not only because he loved the old general, but on account of
the change in his own prospects. The train stopped somewhere on the
Potomac at midnight and remained there for four hours. Uneasy and sad,
he wandered down the track and climbed a pole, cut the wire and placed
the ends each side of his tongue and tasted out the fatal message--"Died
at half-past ten." The shock (not the electric) was so great that he
almost fell from the pole.

What a situation! A man climbs a pole at midnight miles from the sick
friend he loves, puts his tongue to inanimate wire, and is told in
concrete language--through the sense of taste--that his friend is dead.
This is only one of the many, many wonderful episodes of the telegraph.



CHAPTER XII.

MISCELLANEOUS METHODS.


"It never rains but it pours." Almost simultaneously with the
demonstration of the Morse telegraph other types were devised. There
were the needle systems of Cooke and Wheatstone, the chemical telegraph
of Alexander Bain, and soon the printing telegraph of House, and later
that of Hughes. The latter is in use on the continent of Europe, and a
modification of it has a very limited use on some American lines. The
Bain telegraph used a key and battery the same as the Morse system, but
it did not depend upon electromagnetism as the Morse system does. When
in operation a strip of paper was made to move under an iron stylus at
the receiving-end of the line. The paper was saturated with some
chemical that would discolor by the electrolytic action of the current.
When a message was sent the paper was set to moving by a clock mechanism
or otherwise, under the stylus that was pressing on the paper as it
passed over a metal roller or bed-plate. The transmitting-operator
worked his key precisely as in sending an ordinary message by the Morse
system. The effect was to send currents through the receiving-stylus
chopped into long or short marks, or the dots and dashes of the Morse
code, and recorded on the tape in marks that were blue or brown,
according to the chemical used. A few lines were established in this
country on the Bain system, but it never came into general use.

A number of systems, called "automatic," grew out of the Bain system.
Bain himself devised, perhaps, the first automatic telegraph. The
fundamental principle of all automatic telegraphs depends upon the
preparation of the message before sending, and is usually punched in a
strip of paper and then run through between rollers that allow the
stylus to ride on the paper and drop through the holes that represent
the dots and lines of the Morse alphabet. Every time the stylus drops
through a hole in the paper it makes electrical contact and sends a
current, long or short, according to the length of the hole. The object
of the automatic system was to send a large amount of business through a
single wire in a short time. It does not save operators, as the messages
have to be prepared for transmission, and then translated at the
receiving-end and put into ordinary writing for delivery.

The automatic system is not used except for special purposes, and the
one that seems to be the most favored is that of Wheatstone. The system
is in use in England and in America to a limited degree.

Early in the history of the telegraph a printing system was devised.
Wheatstone and others had proposed systems of printing telegraphs in
Europe, but these never passed the experimental stage. The first
printing telegraph introduced in America was invented by Royal E. House
of Vermont, and first introduced in 1847 on a line between Cincinnati
and Jeffersonville, a distance of 150 miles. In 1849 a line for
commercial use was established between New York and Philadelphia, and
for some years following many lines were equipped with the House
printing telegraph instrument. The late General Anson Stager was a House
operator at one time. All printing telegraph instruments, while
differing greatly in detail, have certain things in common, to wit: a
means for bringing the type into position, an inking device, a printing
mechanism, a paper feed, and a means for bringing the type-wheels into
unison. There are two general types of printing instruments, the
step-by-step, and the synchronously moving type-wheels. The House
printer was a step-by-step instrument and consisted of two parts, a
transmitter and a receiver. The transmitter consists of a keyboard like
a piano, with twenty-eight keys. These keys are held in position by
springs. Under the keys is a cylinder having twenty-eight pins on it
corresponding to the twenty-six letters of the alphabet and a dot and a
space. This cylinder was driven by some power. In those days it was by
man-power. It was carried by a friction, so that it could be easily
stopped by the depression of any one of the keys that interfered with
one of the pins. One revolution of the cylinder would break and close
the current twenty-eight times, making twenty-eight steps.

The receiving-instrument consisted of a type-wheel and means for driving
it. It was somewhat complicated, and can only be described in a general
way. If the cylinder of the transmitter was set to rotating it would
break and close twenty-eight times each revolution. (There were fourteen
closes and fourteen breaks, each break and each close of the current
representing a step.) The type-wheel of the receiver was divided into
twenty-eight parts, having twenty-six letters and a dot and space, each
break moved it one step and each close a step; so that if the cylinder,
with its twenty-eight pins, started in unison with the type-wheel, with
its twenty-eight letters and spaces, they would revolve in unison. The
keys were lettered, and if any one was depressed the pin corresponding
to it on the cylinder would strike it and stop the rotation of the
cylinder, which stopped the breaking and closing of the circuit, which
in turn stopped the rotation of the type-wheel--and not only stopped it,
but also put it in a position so that the letter on the type-wheel
corresponding to the letter on the key that was depressed was opposite
the printing mechanism. The printing was done on a strip of paper, which
was carried forward one space each time it printed. The printing
mechanism was so arranged that so long as the wheel continued to rotate
it was held from printing, but the moment the type-wheel stopped it
printed automatically.

The messages were delivered on strips of paper as they came from the
machine.

In 1855 David E. Hughes of Kentucky patented a type-printing telegraph
that employed a different principle for rotating the type-wheel. The
electric current was used for printing the letters and unifying the
type-wheels with the transmitting-apparatus. The transmitter, cylinder,
and the type-wheel revolved synchronously, or as nearly so as possible,
and the printing was done without stopping the type-wheel. Whenever a
letter was printed the type-wheel was corrected if there was any lack of
unison.

This type of machine in a greatly improved form is still used on some of
the Western Union lines, especially between New York, Boston,
Philadelphia, and Washington. It is also in use in one of its forms in
most of the European countries.



CHAPTER XIII.

MULTIPLE TRANSMISSION.


Although the printing and automatic systems of telegraphing are used in
America to some extent, the larger part is done by the Morse system of
sound-reading and copying from it, either by pen or the typewriter. In
the early days only one message could be sent over one wire at the same
time, but now from four to six or even more messages may be sent over
the same wire simultaneously without one message interfering with the
other. Like most other inventions, many inventors have contributed to
the development of multiple transmission, till finally some one did the
last thing needed to make it a success. The first attempts were in the
line of double transmission, and many inventors abroad have worked on
this problem.

Moses G. Farmer of Salem, Mass., proposed it as early as 1852, and
patented it in 1858. Gintl, Preece, Siemens and Halske and others abroad
had from time to time proposed different methods of double transmission,
but no one of them was a perfect success. When the line was very long
there was a difficulty that seemed insurmountable. In the common
parlance of telegraphy, there was a "kick" in the instrument that came
in and mutilated the signals. About 1872 Joseph B. Stearns of Boston
made a certain application of what is called a "condenser" to duplex
telegraphy that cured the "kick," and from that time to this it has been
a success. Farther along I will tell you what occasioned this "kick" and
how it was cured. If this or some other method could be applied as
successfully to cure the many chronic "kickers" in the world it would be
a great blessing to mankind.

It has always been a mystery to the uninitiated how two messages could
go in opposite directions and not run into one another and get wrecked
by the way. If you will follow me closely for a few minutes I will try
to tell you.

We have already stated that an electromagnet is made by winding an
insulated wire around a soft iron core. If we pass a current of
electricity through this wire the core becomes magnetic, and remains so
as long as the current passes around it. In duplex telegraphy we use
what is called a differential magnet. A differential electromagnet is
wound with two insulated wires and so connected to the battery that the
current divides and passes around the iron core in opposite directions.
Now if an equal current is simultaneously passed through each of the
wires of the coil in opposite directions the effect on the iron will be
nothing, because one current is trying to develop a certain kind of
polarity at each pole of the magnet, while the current in the other wire
is trying to develop an opposite kind in each pole. There is an equal
struggle between the two opposing forces, and the result is no
magnetism. This assumes that the two currents are exactly the same
strength.

If we break the current in one of the coils we immediately have
magnetism in the iron; or if we destroy the balance of the two currents
by making one stronger than the other we shall have magnetism of a
strength that measures the difference between the two.

Without specifically describing here the entire mechanism--since this is
not a text-book or a treatise--we may say that a duplex telegraph-line
is fitted with these differentially wound electromagnets at every
station. When Station A (Fig. 3) is connected to the line by the
positive pole of its battery, Station B will have its negative pole to
line and its positive to earth. When A depresses his key to send a
message, half the current passes by one set of coils around his
differential magnet through a short resistance-coil to the earth, and
the other half by the contrary coil around the magnet to the line, and
so to Station B. The divided current does not affect A's own station,
being neutralized by the differential magnet, but it does affect B,
whose instrument responds and gives him the message.

Now B may at the same time send a message to A by half of his own
divided current from his own end of the line.

    [Illustration: Fig. 3.

    Represents a duplex 500-mile telegraph-line. A and B are the two
    terminal stations; B B´, the batteries; K K´, the keys; D D´,
    the small resistance-coils, equal to the battery-resistance when
    the latter is not in circuit; R R´, resistances each equal to
    the 500-mile line; and C C´, condensers giving the artificial
    lines R R´ the same capacity as the 500-mile line.]

The puzzle to most people is: How can the signals pass each other in
different directions on the same wire? But the signals do not have to
pass each other. In effect, they pass; but in fact, it is like going
round a circle--the earth forming half. A sends his message over the
line to B. B sends his message to A through the earth and up A's
ground-wire. The operative who is sending with positive pole to line
_pushes_ his current through--so to speak--while the operative who is
sending with the negative pole to line _pulls_ more current in the same
direction through the line whenever he closes his key.

This may not be a strictly scientific statement; but, as long as we
speak of a "current" flowing from positive to negative poles (which is
the invariable course electricity takes), it is the way to look at the
matter understandingly.

The short "resistance-coil" at each end, fortified by a "condenser" made
of many leaves of isolated tin-foil, to give it capacity, offers
precisely the same resistance to the current as the 500 miles of wire
line; so that the twin currents that run around the differential magnet
exactly neutralize each other and make no effect in the office the
message starts from; while one of them takes to the earth, and the other
to the line to carry the message.

This condenser is necessary, because the short resistance-coil affects
the current immediately, while the long line with its greater amount of
metal does not give the same amount of resistance till it is filled from
end to end, which requires a fraction of a second. During this time,
however, more current is passing through the differential coil connected
with the line than through the short resistance-coil; and the unequal
flow causes the relay armature to jump, or "kick." The condenser, with
the many leaves of tin-foil, supplies the greater metal surface to be
traversed by the short line current, causes the flow to be equal in both
circuits at all times, and thus cures the "kick." It is this quality of
a condenser that enables us to give to an artificial line of any
resistance all the qualities, including capacity, and exhibit all the
phenomena of a real line of any length, and it was this quality that
enabled Mr. Stearns to take the "kick" out of duplex transmission and
thus change the whole system, which created a new era in telegraphy.

We have just spoken of the "capacity" of a circuit, and stated that it
was determined by the mass of metal used. This capacity is measured by a
standard of capacity that is arbitrary and consists of a condenser,
constructed so that a given amount of surface of tin-foil may be plugged
in or out. The practical unit of capacity is called the micro-farad, the
real unit is the farad, and takes its name from Faraday.

But let us go back to multiple systems of transmission. There are many
other systems of simultaneous transmission aside from the duplex, and
all of them are classed under the general head of multiple telegraphy.
First there is the quadruplex, that sends two messages each way
simultaneously, making one wire do the work of four single wires--as
they were used at first. The quadruplex is very extensively used by the
Western Union Telegraph Company and others. It would be difficult to
explain it in a popular article, so we will not attempt it. There is
another form of multiple telegraph that was used on the Postal Telegraph
line when it first started--which was invented and perfected by the
writer--that can be more easily explained.

In 1874 I discovered a method of transmitting musical tones
telegraphically, and the thing that set my mind in that direction was a
domestic incident. It is a curious fact that most inventions have their
beginnings in some incident or observation that comes within the
experience of some one who is able to see and interpret the meaning of
such incidents or observations. I do not mean to say that inventions are
usually the result of a happy thought, or accident; the germ may be, but
the germ has to have the right kind of soil to take root in and the
right kind of culture afterward. It is a rare thing that an invention,
either of commercial or scientific importance, ever comes to perfection
without hard work--midnight oil and daylight toil; and it is rarely, if
ever, that a discovery or an invention based upon a discovery does not
have, sooner or later, a practical use, although we sometimes have to
wait centuries to find it put. We had to wait forty-four years after
the galvanic battery was discovered before it became a useful servant of
man. It was fifty years or more after the discovery by Faraday of
magneto-electricity before it found a useful application beyond that of
a mere toy, but now it is one of the most useful servants we have, as
shown in its wonderful development in electric lighting and electric
railroads, to say nothing of its heating qualities and the useful
purpose it serves in driving machinery. The interesting discoveries of
Professor Crookes in passing a current of electricity through tubes of
high vacua waited many years before they found a practical use in the
X-ray, that promises to be of great service in medicine and surgery.

The transmission of musical harmonies telegraphically, while in itself
of great scientific interest, was of no practical use, but it led to
other inventions, of which it is the base, that are transcendently
useful in every-day life. The transmission of harmonic sounds by
electricity underlies the principle of the telephone. There is a vast
difference, in principle, between the transmission of simple melody,
which is a combination of musical tones transmitted successively--one
tone following another--and the transmission of harmony, which involves
the transmission of two or more tones simultaneously. The former can be
transmitted by a make-and-break current. In the latter case one tone
has to be superposed upon another and must be transmitted with a varying
but a continuously closed current. I make a distinction between a closed
circuit and a closed current. In the case of the arc-light the circuit
is open (that is, broken), technically speaking, but the current is
still flowing. The reason why the Reiss and other metallic contact
telephone transmitters cannot successfully be used for telephone
purposes is that metal points will not allow of sufficient separation of
the transmitting points without breaking the current as well as the
circuit. Carbon contacts admit of a much wider separation without
actually stopping the flow of the current, which latter is a necessity
for perfect telephonic transmission, and it was the use of carbon that
made that form of transmitter a success.

There are other forms, or at least one other form that does not depend
upon the length of the voltaic arc formed when the electrodes are
separated. Of this we will speak another time. Now let us go back to the
domestic incident referred to above.

One evening in the winter of 1873-4 I came home from my laboratory work
and went into the bathroom to make my toilet for dinner. I found my
nephew, Mr. Charles S. Sheppard, together with some of his playmates,
taking electrical "shocks" from a little medical induction-coil that I
heard humming in the closet. He had one terminal of the coil connected
to the zinc lining of the bathtub--which was dry at that time--while he
held the other in his left hand, and with his right was taking shocks
from the lining of the tub by rubbing his hand against the zinc. I
noticed that each time he made contact with the tub, as he rubbed it for
a short distance, a peculiar sound was emitted from under his hand, not
unlike the sound made by the electrotome that was vibrating in the
closet. My interest was immediately aroused, and I took the electrode
out of his hand and for some time experimented with it, going to the
cupboard from time to time to change the rate of vibration of the
electrotome, and thus change the quality of the sound. I noticed that
the sound or tone under my hand, if it could be so called, changed with
each change of the rate of vibration. The thing that most interested me
was that the peculiar characteristics of the noise were reproduced. In
those few minutes I laid out work enough for years of experiment, and as
a result I was late to dinner.

This discovery opened up to my mind the possibility of three things--the
transmission of music and of speech or articulate words through a
telegraph-wire, and the transmission of a number of messages over a
single wire. I constructed a keyboard consisting of one octave and made
a set of reeds tuned to the notes of the scale, and then when some one
would play a melody I could reproduce it in two ways: One by placing my
body in the circuit and rubbing a metal plate--it might be the bottom of
a tin pan, a joint of stovepipe or otherwise--anything that was metal
and would vibrate would give the effect. Another way was to connect an
electromagnet (having a diaphragm or reed across its poles) in the
circuit at the receiving-end and mount it on some kind of a soundboard.
I made a great number of different kinds of receivers that were capable
of receiving either musical or articulate sounds, as has many times been
proven by experiment. I carried two sets of experiments along together;
the one looking toward a system of multiple telegraphy and the other the
transmission of articulate speech. Let us first look into the multiple
telegraph and take the other up under the head of the telephone.

When the electrical keyboard was completed I found that I could transmit
not only a melody but a harmony; that more than one tone could be
transmitted simultaneously. This discovery opened up a long series of
experiments with the view of sending a number of messages simultaneously
by means of musical tones differing in pitch. I had already demonstrated
that several tones could be transmitted at once, but they would speak
all alike (with the same loudness) on the receiving-instrument. I now
went to work on an instrument that responded for one note only and
succeeded beyond my expectations. I made three different kinds of
receiving-instruments. The first was a steel strap about eight inches
long by three-eighths wide. This strap was mounted in an iron frame in
front of an electromagnet. A thumbscrew enabled me to stretch the strap
till it would vibrate at the required pitch. If, for instance, the
sending-reed vibrated at the rate of 100 times per second and the strap
of the receiver was stretched to a tension that would give 100
vibrations per second when plucked, it would then respond to the
vibrations of the sending-reed but not to those of another reed of a
different rate of vibration. If we take mounted tuning-forks tuned in
pairs of different pitches, say four pairs, so that each fork has a mate
that is in exact accord with it, and place them all in the same room,
and sound one of them for a few seconds and then stop it, upon examining
the other forks you will find all of them quiet except the mate of the
one that was sounded. This one will be sounding. If we now sound four of
the forks and then stop them the other four will be sounding from
sympathy because the mate of each one of them has been sounded. If only
two forks differing in pitch are sounded only two of the others will
sound in sympathy. In the first case only one set of sound-waves were
set up in the air, and the fork that found itself in accord with this
set responded. When four forks differing in pitch were sounded there
were four sets of tone-waves superposed upon each other existing in the
air, so that each of the remaining forks found a set of waves in
sympathy with its own natural rate of vibration and so responded.

Now apply this principle to the harmonic telegraph and you can
understand its operation. At the transmitting-end of a line of
wire there are a certain number of forks or reeds kept vibrating
continuously. These reeds each have a fixed rate of vibration
and bear a harmonic relation to each other so as not to have
sound-interference or "beats." At the receiving-end of the line
there are as many electromagnets as there are transmitting-reeds, and
each magnet has a reed or strap in front of it tuned to some one of the
transmitting-reeds, so that each transmitting-reed has a mate in exact
harmony with it at the receiving-end of the line. Keys are so arranged
at the transmitting-end as to throw the tones corresponding to them to
line when depressed. In other words, when the key belonging to battery B
and vibrator 1 is depressed (see Fig. 4) the effect is to send
electrical pulsations through the line corresponding in rate per second
to that of the vibrator. The same is true of battery B´ and vibrator 2.
During the time any key is depressed--we will say of tone No. 1--this
tone will be transmitted through the line and be reproduced by its
mate--the one tuned in accord with it--at the receiving-station. By a
succession of long and short tones representing the Morse code a message
can be sent. Numbers two, three and four might be sending at the same
time, but they would not interfere with number one or with each other.
In 1876-7 the writer succeeded in sending eight simultaneous messages
between New York and Philadelphia by the harmonic method.

    [Illustration: Fig. 4.

    In this diagram, 1 and 2 are tuned reeds; 1A 2A are receivers
    tuned to the reeds 1 and 2 respectively; 1 and 1A are in unison,
    also 2 and 2A, but the two groups (the 1s and the 2s) differ
    from each other in pitch.]

There were two ways of reading by the harmonic method. One was by the
long and short tone-sounds and the other by the ordinary sounder.

The vibration of the receiving-reed was made to open and close a local
circuit like a common Morse relay and thus operate the sounder. It is
useless to try to send a message if the sender and receiver are out of
tune with each other in this system.

What is true in science is true in life. If we are out of tune with our
surroundings we only beat the air, and our efforts are in vain. We get
no sympathetic response.



CHAPTER XIV.

WAY DUPLEX SYSTEM.


A novel form of double transmission was invented by the writer soon
after the completion of the harmonic system, and was an outgrowth of it.
It is still in use on some of the railroad-lines. An ordinary railroad
telegraph-line has an instrument in circuit in every office along the
road, chiefly for purposes of train-dispatching. As we have heretofore
explained, whenever any one office is sending, the dispatch is heard in
all of the offices. The "Way duplex" system permits of the use of the
line for through business simultaneously with the operation of the local
offices. That is to say, any station along the line may be telegraphing
with any other station by the ordinary Morse method, and at the same
time messages may be passing back and forth between the two end offices.

This is accomplished by the following method: At each end of the line
there is a tuned reed, such as we have described in our last chapter,
that is kept constantly in vibration by a local battery during working
hours. This vibrator is so arranged in relation to the battery that
whenever the key belonging to it is depressed the current all through
the line is rendered vibratory. There is also in circuit at each end of
the line a harmonic relay, that is tuned in accord with the vibrating
reed of the sender. If either key belonging to this part of the system
is opened, as in the act of sending a message, these harmonic relays,
being tuned in sympathy with the sending-vibrator, will respond, thus
sending Morse characters made up of a tone broken into dots and dashes.
This tone can be read directly from the relay, or, as is usually the
case, it causes the sounder to operate in the common way.

You will at once inquire why the ordinary Morse instruments in the local
offices are not affected by these vibratory signals, and also why the
harmonic instruments at the end office are not affected by the working
of the local offices. The local office does not open the circuit
entirely, but simply cuts out a resistance by the operation of the
special harmonic key. When a resistance is thrown into an electric
circuit it weakens the current in proportion to the amount of resistance
interposed. You will see that there is some current still left in the
line when the key is open, but the spring of the relay at the local
office is so adjusted as to pull the armatures away from the magnets
whenever the current is weakened by throwing in the resistance, so that
by this means an ordinary Morse telegraphic relay may be worked without
ever entirely opening the circuit. In the Way duplex system there is a
resistance at each station that is cut in and out by the operation of
its key, which causes all the instruments in the line to work
simultaneously except the two harmonic relays located one at each end of
the line. These will not respond to anything but the vibratory signal.

In order to prevent the Morse relays at the local offices from
responding to the vibratory current a condenser is connected around
them. This condenser serves two purposes: It enables the short impulses
of the vibrating current to pass around the relays without having to be
resisted by the coils of the magnets, and between the pulsations each
condenser will discharge through the relay at the local offices, and
thus fill in the gap between the pulsations, producing the effect on the
relay of a steady current. When a line is thus equipped it may be
treated in every respect as two separate wires, one of them doing way
business and the other through business. It is a curious blending of
science and mechanism.

Another interesting application was made of the system of transmission
by musical tones--by Edison, some years ago. We refer to the
transmission of messages to and from a moving railroad-train with the
head office at the end of the line. In this case the message was
transmitted a part of the distance through the air;--another instance of
wireless telegraphy. The operation was as follows: One of the wires
strung on the poles nearest to the track was fitted up with a vibrator
and key at the end of the line similar to that of the Way duplex just
described. In one of the cars was another battery, key and vibrator, and
as only one tone was used, no tone-selecting device or harmonic relay
was needed, but instead an ordinary receiving-telephone was used to read
the long and short sounds sent over the lines. One end of the battery in
the car was connected through the wheels to the earth, while the other
end was connected to the metal roof of the car. Being thus equipped, we
will suppose our train to be out on the road forty or fifty miles from
either end of the line, moving at the rate of forty miles an hour. The
operator at Chicago, say, wishes to send a message to the moving train;
he operates his key in the ordinary manner, which makes the current on
the line vibratory during the time the key is depressed. These
electrical vibrations cause magnetic vibrations, or ether-waves, to
radiate in every direction from the wire, at right angles to the
direction of the current, like rays of light. When they strike the roof
of the car they create electrical impulses in the metal by induction
(described in Chap. VI). These impulses pass through a telephone located
in the car to the ground. A Morse operator listening, with the telephone
to his ear, will hear the message through the medium of a musical tone
chopped up into the Morse code. In like manner the operator in the car
may transmit a message to the roof of the car and thence through the air
to the wire, which will be heard, by any one listening, in a telephone
which is connected in that circuit,--and, as a matter of fact, it will
be heard from any wire that may be strung on any of the poles on either
side of the road.

Some years ago an experiment of this kind was made on one of the roads
between Milwaukee and Chicago.

What wonderful things can be done with electricity! As a servant of man
it is reliable and accurate--seeming almost to have the qualities of
docility--when under intelligent direction, that is in accord with the
laws of nature; but under other conditions it changes from the willing
servant to a hard master, hesitating not to destroy life or property
without regard to persons or things.



CHAPTER XV.

TELEPHONY.


In the foregoing chapters I have described the method of transmitting
musical tones telegraphically and its applications to multiple
telegraphy, as well as to a mode of communicating with a moving
railroad-train. As I stated in a former chapter, after discovering a
method of transmitting harmony as well as melody, I had in mind two
lines of development, one in the direction of multiple telegraphy, and
the other that of the transmission of articulate speech. I will not
attempt to give the names of all the people who have contributed to the
development of the telephone (as this alone would fill a volume) but
only describe my own share in the work--leaving history to give each one
due credit for his part. While I do not intend, here, to enter into any
controversy regarding the priority of the invention of the telephone, I
wish to say that from the time I began my researches, in the winter of
1873-4, until some time after I had filed my specification for a
speaking or articulating telephone, in the winter of 1875-76, I had no
idea that any one else had done or was doing anything in this direction.
I wish to say further that if I had filed my description of a telephone
as an application for a patent instead of as a caveat, and had
prosecuted it to a patent, without changing a word in the specification
as it stands to-day, I should have been awarded the priority of
invention by the courts. I am borne out in this assertion by the highest
legal authority. In law, a _caveat_ (Latin word, meaning "Let him
beware") is a warning to other inventors, to protect an incomplete
invention; whereas in fact the invention to be protected may be
complete. An _application_ for a patent is presumed by the law to be for
a completed invention; but it may be, and very often is, incomplete. It
would often make a very great difference if decisions were rendered
according to the facts in the case rather than according to rules of law
and practice, that sometimes work great injustice to individuals.

As has been said in another chapter, in the summer of 1874 I went to
Europe in the interest of the telephone, taking my apparatus, as then
developed, with me. I came home early in the fall and resumed my
experimental work. Many interesting as well as amusing things occurred
during these experiments.

I remember that in the fall or early winter of 1874 I was in Milwaukee
with my apparatus carrying on some experiments on a wire between
Milwaukee and Chicago. I had my musical transmitter along, and one
evening, for the entertainment of some friends at the Newhall House, a
wire was stretched across the street from the telegraph office into one
of the rooms of the hotel. A great number of tunes were played at the
telegraph-office by Mr. Goodridge, who was my assistant at that time,
which were transmitted across the street, as before stated. In those
days it was a common practice in telegraphy to use one battery for a
great number of lines. For instance, starting with one ground-wire which
connected with, say, the negative pole of the battery, from the positive
pole two, three or a half-dozen lines might be connected, running in
various directions, connecting with the ground at the further end, thus
completing their circuits. For use in transmitting tones across the
street that evening we connected our line-wire on to the telegraph
company's battery, which consisted of 100 or more cells, and which had
four or five more lines radiating from the end of the battery to
different parts of Wisconsin. Our line was tapped on to the battery
(without changing any of its connections) twenty cells from the
ground-wire. In transmitting, each vibration would momentarily shut off
these twenty cells from the lines that were connected with the whole
battery. The effect of this (an effect that we did not anticipate at the
time) was to send a vibratory current out on all the lines that were
connected with that single battery as well as across the street. A great
many familiar tunes were played during the course of an hour or two
which, unconsciously for us, were creating great consternation
throughout the State of Wisconsin, in many of the offices through which
these various lines passed.

Next morning reports and inquiries began to come in from various towns
and cities west, northwest and north, giving details of the phenomena
that were noticed on the instruments located in the various offices
along the lines. They reported their relays as singing tunes; one party
said he thought the instruments were holding a prayer-meeting from the
fact that they seemed to be singing hymn-tunes for quite a while, but
this notion was finally dissipated, because they grew hilarious and sang
"Yankee Doodle."

One operator, up in the pine woods of northern Wisconsin, did not seem
to take the cheerful view of it that some of the others did. He was
sitting alone in the telegraph-office that evening when he thought he
heard the notes of a bugle in the distance; he got up and went to the
door to listen, but could hear nothing; but on coming back into the room
he heard the same bugle notes very faintly. He was inclined to be
somewhat superstitious and grew very nervous; finally, on looking
around, he located the sound in his relay, but this did not help matters
with him. With superstitious awe he listened to the instrument for a few
moments, while it gave out the solemn tones of "Old Hundred," then it
suddenly jumped into a hilarious rendering of "Yankee Doodle." This was
too much for our nervous friend, and hastily putting on his overcoat, he
left the office for the night.

On another occasion, when I was giving a lecture in one of the cities
outside of Chicago, where exhibitions of music transmitted from Chicago
were given, one of the operators along the line was very much astonished
by his switchboard suddenly becoming musical. Orders had been given for
the instruments in all the local offices to be cut out of the particular
line that I was using. Hence the instrument in this particular office
was not in the circuit through which the tunes were being transmitted.
The wire, however, ran through his switchboard, and owing probably to a
loose connection, or an induced effect, there was a spark that leaped
across a short space at each electrical pulsation that passed through
the line, thus reproducing the notes of the various tunes played.

You will remember in one of the chapters on sound (Volume II.), it is
stated that a musical tone is made up of a succession of sounds
repeated at equal intervals, and that the pitch of the tone is
determined by the number of sound-impulses per second. Applying this law
to the sparks, you will be able to see how the switchboard played tunes
for the operator.

In the foregoing experiments in transmitting musical tones
telegraphically, I used a great many different varieties of receivers.
Some of them were designed with metal diaphragms mounted over single
electromagnets, not unlike the receiver of an ordinary telephone. These
instruments would both transmit and receive articulate speech when
placed in circuit with the right amount of battery to furnish the
necessary magnetism. However, they were not used in that way at the time
they were first made--in 1874. These I called common receivers, as they
were designed to reproduce all tones equally well. I designed and
constructed another form of receiver, based somewhat upon the theory of
the harmonic telegraph.

This consisted of an electromagnet of considerable size, mounted upon a
wooden rod about ten feet long. Mounted upon this rod were also
resonating boxes or tubes made of wood of the right size to have their
air-cavities correspond with the various pitches of the
transmitting-reeds, so that each tone would be re-enforced by some one
of these air-cavities, thus giving a louder and more resonant effect to
the musical notes.

Here were two types of receiver, one that would receive one sound as
well as another, but none of them so loud, while the other was
constructed on the principle of selection and re-enforcement, so that a
particular note would be sounded by the box having a cavity
corresponding to the pitch of the tone, and was much louder and of much
better quality than I could get from the diaphragm receiver. One of
these receivers pointed to the harmonic telegraph and the other to the
speaking telephone. I knew that I had a receiver that would reproduce
articulate speech or anything else that could be transmitted.

My first conceptions of an articulate speech-transmitter were somewhat
complicated. I conceived of a funnel made of thin metal having a great
number of little riders, insulated from the funnel at one end and
resting lightly in contact with the funnel at the other end. These
riders were to be made of all sizes and weights so as to be responsive
to all rates of vibration. In the light of the present day we know that
such an arrangement would have transmitted articulate speech, but
perhaps not so well as a single point would do when properly adjusted.
My mind clung to this idea till in the fall of 1875, when an observation
I made upon the street changed the whole course of my thinking and
solved the problem. The incident I refer to took place in Milwaukee,
where I was then experimenting. One day while out on an errand I noticed
two boys with fruit-cans in their hands having a thread attached to the
center of the bottom of each can and stretched across the street,
perhaps 100 feet apart. They were talking to each other, the one holding
his mouth to his can and the other his ear. At that time I had not heard
of this "lovers' telegraph," although it was old. It is said to have
been used in China 2000 years ago.

The two boys seemed to be conversing in a low tone with each other and
my interest was immediately aroused. I took the can out of one of the
boy's hands (rather rudely as I remember it now), and putting my ear to
the mouth of it I could hear the voice of the boy across the street. I
conversed with him a moment, then noticed how the cord was connected at
the bottom of the two cans, when, suddenly, the problem of electrical
speech-transmission was solved in my mind. I did not have an opportunity
immediately to construct an instrument, as I had a partner who was
furnishing money for the development of the harmonic telegraph and would
not listen to any collateral experiments. I remember sitting down by
this partner one day and telling him what I could do in the way of
transmitting speech through a wire. I told him I thought it would be
very valuable if worked out. He gave me a look that I shall never
forget, but he did not say a word. The look conveyed more meaning than
all the words he could have said, and I did not dare broach the subject
again.

However, as soon as I found opportunity, without saying a word to
anybody except my patent lawyer, I filed a description, accompanied by
drawings, of a speaking telephone which stands in history to-day as the
first complete description on record of the operation of the speaking
telephone. It described an apparatus which, when constructed, worked as
described, and it is a matter of history that the first articulate
speech electrically transmitted in this country was by a transmitter
constructed on the principle described, and almost identically after the
drawings in my caveat. While the transmitter described in this caveat
was not the best form, it would transmit speech, and it contained the
foundation principle of all the telephone transmitters in use to-day.

There are two methods of transmitting speech. One is known as the
magneto method and the other that of varying the resistance of the
circuit. My first transmitter was devised on the latter principle.

I append to this extracts from my specification filed Feb. 14, 1876:

     _To All Whom It May Concern:_--Be it known that I, Elisha Gray
     of Chicago, in the County of Cook and State of Illinois, have
     invented a new art of transmitting vocal sounds
     telegraphically, of which the following is a specification: It
     is the object of my invention to transmit the tones of the
     human voice through a telegraphic circuit, and reproduce them
     at the receiving-end of the line, so that actual conversations
     can be carried on by persons at long distances apart. I have
     invented and patented methods of transmitting musical
     impressions or sounds telegraphically, and my present invention
     is based upon a modification of the principle of said
     invention, which is set forth and described in letters patent
     of the United States, granted to me July 27, 1875, respectively
     numbered 166,095 and 166,096, and also in an application for
     letters patent of the United States, filed by me, Feb. 23,
     1875. * * * My present belief is that the most effective method
     of providing an apparatus capable of responding to the various
     tones of the human voice is a tympanum, drum, or diaphragm,
     stretched across one end of the chamber, carrying an apparatus
     for producing fluctuations in the potential of the electric
     circuit and consequently varying in its power. * * * The
     vibrations thus imparted are transmitted through an electric
     circuit to the receiving-station, in which circuit is included
     an electromagnet of ordinary construction, acting upon a
     diaphragm to which is attached a piece of soft iron, and which
     diaphragm is stretched across a receiving vocalizing chamber
     _C_, somewhat similar to the corresponding vocalizing chamber
     _A_.

     The diaphragm at the receiving-end of the line is thus thrown
     into vibrations corresponding with those at the
     transmitting-end, and audible sounds or words are produced.

     The obvious practical application of my improvement will be to
     enable persons at a distance to converse with each other
     through a telegraphic circuit, just as they now do in each
     other's presence, or through a speaking-tube.

     I claim as my invention the art of transmitting vocal sounds or
     conversations telegraphically through an electric circuit.

This specification was accompanied by cuts of the transmitter and
receiver connected by a line-wire and showing one person talking to the
transmitter and another listening at the receiver. These cuts may be
seen in various books on the subject of telephony.



CHAPTER XVI.

HOW THE TELEPHONE TALKS.


Everybody knows what the telephone is because it is in almost every
man's house. But while everybody knows what it is, there are very few
(comparatively speaking) that know how it works. If you remember what
has been said about sound and electromagnetism it will not be hard to
understand.

When any one utters a spoken word the air is thrown into shivers or
vibrations of a peculiar form, and every different sound has a different
form. Therefore, every articulate word differs from every other word,
not only as a shape in the air, but as a sensation in the brain, where
the air-vibrations have been conducted through the organ of hearing;
otherwise we could not distinguish between one word and another. Every
different word produces a different sensation because there is a
physical difference, as a shape or motion, in the air where it is
uttered. If one word contains 1000 simultaneous air-motions and another
1500 you can see that there is a physical or mechanical difference in
the air.

The construction of the simplest form of telephone is as follows: Take a
piece of iron rod one-half or three-quarters of an inch long and
one-quarter inch thick, and after putting a spool-head on each end to
hold the wire in place wind it full of fine insulated copper wire;
fasten the end of this spool to the end of a straight-bar permanent
magnet. Then put the whole into a suitable frame, and mount a thin
circular diaphragm (membrane or plate) of iron or steel, held by its
edges, so that the free end of the spool will come near to but not touch
the center of the diaphragm. This diaphragm must be held rigidly at the
edges.

Now if the two ends of the insulated copper wires are brought out to
suitable binding-screws the instrument is done.

The permanent steel magnet serves a double purpose. When the telephone
was first used commercially, the instrument now used as a receiver was
also used as a transmitter. As a transmitter it is a dynamo-electric
machine. Every time the iron diaphragm is moved in the magnetic field of
the pole of the permanent magnet, which in this case is the free end of
the spool (the iron of the spool being magnetic by contact with the
permanent magnet), there is a current set up in the wire wound on the
spool; a short impulse, lasting only as long as the movement lasts. The
intensity of the impulse will depend upon the amplitude and quickness
of the movement of the diaphragm. If there is a long movement there will
be a strong current and vice versa. If a sound is uttered, and even if
the multitude of sounds that are required to form a word, be spoken to
the diaphragm, the latter partakes in kind of the air-motions that
strike it. It swings or vibrates in the air, and if it is a perfect
diaphragm it moves exactly as the air does, both as to amplitude and
complexity of movement. You will remember that in the chapter on
sound-quality (Vol. II) it was said that there were hundreds and
sometimes thousands of superposed motions in the tones of some voices
that gave them the element we call quality.

All these complex motions are communicated by the air to the diaphragm,
and the diaphragm sets up electric currents in the wire wound on the
spool, corresponding exactly in number and form, so that the current is
molded exactly as the air-waves are. Now, if we connect another
telephone in the circuit, and talk to one of them, the diaphragm of the
other will be vibrated by the electric current sent, and caused to move
in sympathy with it and make exactly the same motions relatively, both
as to number and amplitude.

It will be plain that if the receiving diaphragm is making the same
motions as the transmitting diaphragm, it will put the air in the same
kind of motion that the air is in at the transmitting end, and will
produce the same sensation when sensed by the brain through the ear. If
the air-motion is that of any spoken word it will be the same at both
ends of the line, except that it will not be so intense at the
receiving-end; it is the same relatively. And this is how the telephone
talks.

I have said that the permanent magnet had two functions. In the case of
the transmitter it is the medium through which mechanical is converted
into electrical energy. It corresponds to the field-magnet of the
dynamo, while the diaphragm corresponds to the revolving armature, and
the voice is the steam-engine that drives it. In the second place, it
puts a tension on the diaphragm and also puts the molecules of the iron
core of the magnet in a state of tension or magnetic strain, and in that
condition both the molecules and the diaphragm are much more sensitive
to the electric impulses sent over the wire from the transmitter. This
fact was experimented upon by the writer as far back as 1879 and
published in the Journal of the American Electrical Society. At the
present day this form of telephone is used only as a receiver.

Transmitters have been made in a variety of forms, but there are only
two generic methods of transmission. One is the magneto method--the one
we have described--and the other is effected by varying the resistance
of a battery current. The former will work without a battery, as the
voice acting on the wire around the magnet through the diaphragm creates
the current; in the latter the current is created by the battery but
molded by the voice. In the latter method the current passes through
carbon contacts that are moved by the diaphragm. Carbon is the best
substance, because it will bear a wider separation of contact without
actually breaking the current. When carbon points are separated that
have an electric current passing through them, there is an arc formed on
the same principle as the electric arc-light.

Great improvements in details have been made in the telephone since its
first use, but no new principles have been discovered as applied to
transmission.

We have spoken in another place regarding the various claimants to the
invention of the telephone, but here is one that has been overlooked. A
young man from the country was in a telegraph-office at one time and was
left alone while the operator went to dinner. Suddenly the sounder
started up and rattled away at such a rate that the countryman thought
something should be done. He leaned down close to the instrument and
shouted as loudly as possible these words: "The operator has gone to
dinner." From what we know now of the operation of the telephone I have
no doubt but that he transmitted his voice to some extent over the wire.
This young man's claims have never been put forward before, and we are
doing him tardy justice. But his claim is quite as good as many others
set forth by people who think they invent, whenever it occurs to them
that something new might possibly be done, if only somebody would do it.
And when that somebody does do it they lay claim to it.

In the early days of the telephone it was not supposed that a vocal
message could be transmitted to a very great distance. However, as time
went on and experiments were multiplied the distance to which one could
converse with another through a wire kept on increasing.

In these days, as every one knows, it is a daily occurrence that
business men converse with each other, telephonically, for a distance of
1000 miles or more; in fact, it is possible to transmit the voice
through a single circuit about as great a distance as it is possible to
practically telegraph. This leads us to speak of another telegraphic
apparatus which we have not heretofore mentioned, and that is the
telegraphic repeater. It is a common notion that messages are sent
through a single circuit across the continent, but this is not the
case, although the circuits are very much longer than they were some
years ago. The repeater is an instrument that repeats a message
automatically from one circuit to another. For instance, if Chicago is
sending a message to New York through two circuits, the division being
in Buffalo, the repeater will be located at Buffalo and under the
control of both the operator at Chicago and the operator in New York.
When Chicago is sending, one part of the repeater works in unison with
the Chicago key and is the key to the New York circuit, which begins at
Buffalo. When New York is sending the other part of the repeater
operates, which becomes a key which repeats the message to the Chicago
line. In this way the practical result is the same as though the circuit
were complete from New York to Chicago. At the present day some of the
copper wires and perhaps some of the larger iron wires are used direct
from Chicago to New York without repetition, but all messages between
New York and San Francisco are automatically repeated at least twice and
under certain conditions of weather oftener. I can remember that in wet
weather in the old days, with such wires as they had then (being No. 9
iron with bad joints, which gave the circuit a high resistance) that
these repeaters would be inserted at Toledo, Cleveland, Buffalo and
Albany in order to work from Chicago to New York. Under such conditions
the transmission would necessarily be slow, because an armature time
will be lost at each repeater. Regarding each repeater as a key, when
Chicago depresses his key the armature of the next repeater must act,
and then the next successively, and all of this takes time, although
only a small fraction of a second.

The repeater was a very delicate instrument and had to be handled by a
skilled operator. Every wire must be in its place or the instrument
would fail to operate. I remember on one occasion in Cleveland that
along in the middle of the night the repeater failed to work. The
operator knew nothing of the principle of its operation, so that when it
failed he had to appeal to some of his superiors.

At this time there was no one in the office who knew how to adjust it,
so they had to send up to the house of the superintendent and arouse him
from his sleep and bring him down to the office. He looked under the
table and found that one of the wires had loosened from its binding-post
and was hanging down. He said immediately, "Here's the trouble; I should
think you could have seen it yourself." The operator replied, "I did see
that, but I didn't think one wire would make any difference." He learned
the lesson that all electricians have had to learn--that even one wire
makes all the difference in the world. But this operator was no worse
in that respect than some of his superiors. One of the heads of the
Cleveland office at one time in the early days wanted to give some
directions to the office at Buffalo. He told the operator at the key to
tell Buffalo so and so, when the operator replied: "I can't do it;
Buffalo has his key open." The official immediately said with severity:
"Tell him to close it." He forgot that it would be as difficult for him
to tell him to close it, as it would have been to have sent the original
message.

But let us go back to the telephone. While it is possible to send a
message from New York to San Francisco by telegraph, it is not possible
to telephone that distance, because as yet no one has been able to
devise a repeater that will transfer spoken words from one line to
another satisfactorily. But unless the printer and publisher bestir
themselves some one may accomplish the feat before this little book
reaches the reader. If this proves to be true, let the writer be the
first to congratulate the successful inventor.



CHAPTER XVII.

SUBMARINE CABLES.


The first attempts at transmitting messages through wires laid in water
were made about 1839. These early experiments were not very successful,
because the art of wire-insulation had not attained any degree of
perfection at that time. It was not until gutta-percha began to be used
as an insulator for submarine lines that any substantial progress was
made.

The first line, so history states, that was successfully laid and
operated was across the Hudson River in 1848. This line was constructed
for the use of the Magnetic Telegraph Company.

In the following year experiments with gutta-percha insulation were
successfully made, and about 1850 a cable was laid across the English
Channel between Dover and Calais (twenty-seven miles), consisting of a
single strand of wire having a covering of gutta-percha. The insulation
was destroyed in a day or two, which demonstrated the fact that all
submarine cables must be protected by some kind of armor. In 1851
another cable was laid between these two points, containing four
conductors insulated with gutta-percha, and over all was an armor of
iron wire. Twenty-one years later this cable was still working, and for
all we know is working now. After this successful demonstration other
cables were laid for longer distances.

These short-line cables served to demonstrate the relative value of
different material for insulating purposes under water, and it has been
found that gutta-percha possesses qualities superior to almost every
other material as an insulator for submarine cables, although there are
many better materials for air-line insulation. Gutta-percha when exposed
to air becomes hardened and will crack, but under water it seems to be
practically indestructible.

Ocean telegraphy really dates from the laying of the first successful
Atlantic cable. There were many problems that had to be solved, which
could be done only by the very expensive experiment of laying a cable
across the Atlantic Ocean. In the first place a survey had to be made of
the bottom of the ocean between the shores of America and Great Britain.
The most available route was discovered by Lieutenant Maury of the
United States Navy, who made a series of deep-sea soundings, and
discovered that, from Newfoundland to the west coast of Ireland the
bottom of the ocean was comparatively even, but gradually deepening
toward the coast of Ireland until it reached a depth of 2000 fathoms. It
was not so deep but that the cable could be laid on the bottom, nor so
shallow as to be in danger of the waves, icebergs or large sea-animals.

The water below a certain depth is always still and not affected by
winds or ocean currents. At many other points in crossing the ocean,
high mountains and deep valleys are encountered, possessing all the
topographical features of dry land--as the ocean bed is only a great
submerged continent.

The beginning of the laying of the first Atlantic cable was on Aug. 7,
1857. On the morning of Aug. 7, 1858, a year later, after a series of
mishaps and adverse circumstances that would have discouraged most men,
the country was electrified by a dispatch from Cyrus W. Field of New
York (to whom the final success of the Atlantic cable is mainly due),
that the cable had been successfully laid and worked. But this cable
worked only from the 10th of August to the 1st of September, having sent
in that time 271 messages. The insulation became impaired at some point,
when an attempt to force the current through by means of a large battery
only increased the difficulty.

The failure of this first cable served to teach manufacturers and
engineers how to construct cables with reference to the conditions under
which they are to be used. It was found that in the deep sea a much
smaller and less expensive cable could be used than would answer at the
shore ends, where the water is shallow. The shore ends of an ocean cable
are made very large, as compared to the deep-sea portions, so as to
resist the effect of the waves and other interfering obstacles. It was
further learned that the most successful mode of transmitting signals
through the cable was with a small battery of low voltage, and by the
use of very delicate instruments for receiving the messages. It is not
possible to employ such instruments on cables as are used on land-lines,
while it would not be a difficult feat to transmit even twice the
distance over land-lines strung on poles, using the ordinary Morse
telegraph.

The water of the ocean is a conductor, as well as the heavy armor that
surrounds the insulation of the cable. When a current is transmitted
through the conducting wires, in the center of the cable, they set up a
countercharge in the armor and the water above it, somewhat as an
electrified cloud will induce a charge in the earth under it, of an
opposite nature. This countercharge, being so close to the conducting
wire, has a retarding effect upon the current transmitted through it.
An ordinary land-line that is strung on poles that are high up from the
ground has this effect reduced to a minimum, but the greater the number
of wires clustered together on the same poles the more difficult it
becomes to send rapid signals through any one of them.

The instrument used for receiving cable messages was devised by Sir
William Thompson, now Lord Kelvin. One form consists of a very short and
delicate galvanometer-needle carrying a tiny mirror. This mirror is so
related to a beam of light thrown upon it that it reflects it upon a
graduated screen at some distance away, so that its motions are
magnified many hundred times as it appears upon the screen. An operator
sits in a dark room with his eye on the screen and his hand upon the key
of an ordinary Morse instrument. He reads the signal at sight, and with
his key transmits it to a sounder, which may be in another room, where
it is read and copied by another operator. Another form of
receiving-instrument carries, instead of the mirror, a delicate
capillary glass tube that feeds ink from a reservoir, and by this means
the movements of the needle are recorded on a moving strip of paper. The
symbols (representing letters) are formed by combinations of zigzag
lines. This instrument is the syphon-recorder.



CHAPTER XVIII.

SHORT-LINE TELEGRAPHS.


Early in the history of the telegraph short lines began to be used for
private purposes, and as the Morse code was familiar only to those who
had studied it and were expert operators on commercial lines, some
system had to be devised that any one with an ordinary English education
could use; as the expense of employing two Morse operators would be too
great for all ordinary business enterprises. These short lines are
called private lines, and the instruments used upon them were called
private-line telegraph-instruments. Of course they are now nearly all
superseded by the telephone, but they are a part of history.

One of the earliest forms of short-line instruments was called the
dial-telegraph. One of the first inventors, if not the first, of this
form of instrument was Professor Wheatstone of England, who perfected a
dial-telegraph-instrument about the year 1839. The receiving-end of this
instrument consisted of a lettered dial-face, under which was clockwork
mechanism and an escape-wheel controlled by an electromagnet. Each time
the circuit was opened or closed the wheel would move forward one step,
and each step represented one of the letters of the alphabet, so that
the wheel, like the type-wheel of a printing telegraph, had fourteen
teeth, each tooth representing two steps. As the reciprocating movement
of the escapement had a pallet or check-piece on each side of the wheel,
its movement was arrested twenty-eight times in each revolution. These
twenty-eight steps correspond to the twenty-six letters of the alphabet,
a dot and a space. On the shaft of the escape-wheel is fastened a hand
or pointer, which revolves over a dial-face having the twenty-six
letters of the alphabet, also a dot and space. The pointer was so
adjusted that when the escape-wheel was arrested by one of the pallets
it would stop over a letter, showing thus, letter by letter, the message
which the sender was spelling out.

The transmitter consisted of a crank with a knob and a pointer on it,
which was mounted over a dial that was lettered in the same way as the
face of the receiving-instrument. A revolution of this crank would break
and close the circuit twenty-eight times; that is to say, there were
fourteen breaks and fourteen closes of the circuit. If now the
transmitting-pointer and the receiving-pointer are unified so that they
both start from the same point on the dial, and the transmitting-crank
is rotated from left to right, the receiving-pointer will follow it up
to the limit of its speed. In transmitting a message the sender would
turn his crank, or pointer, to the first letter of the word he wished to
transmit, making a short pause, and then move on to the next letter, and
so on to the end of the message, making a short pause on each letter.
The end of a word was indicated by turning the pointer to the space-mark
on the dial. The receiving-operator would read by the pauses of the
needle on the various letters. This was a system of reading by sight.

There have been many forms of this dial-telegraph worked out by
different inventors at different times, and quite a number of them were
used in the old days. It was a slow process of telegraphing, but it was
suited to the age in which it flourished. One of the difficulties of a
dial-telegraph consisted in the readiness with which the transmitter and
receiver would get out of unison with each other; and when this happened
of course a message is unintelligible, and you have to stop and unify
again.

About 1869 the writer invented a dial-telegraph to obviate this
difficulty. In this system a transmitter and receiver were combined in
one instrument, and instead of a crank there were buttons arranged
around the dial in a circle, one opposite each letter. When not in
operation the pointers of both instruments at both stations stood at
zero. In the act of transmitting the operator would depress the button
opposite the letter he wished to indicate, when immediately the pointers
of both instruments would start up and move automatically, step by step,
until the pointer came in contact with the stem of the depressed button,
when it would be arrested, and at the same time cut out the automatic
transmitting-mechanism and cause both needles to remain stationary
during the time the button was depressed. Upon releasing the button the
pointers both fall back to zero at one leap.

The first private line equipped by this instrument was for Rockefeller,
Andrews & Flagler, which was the firm name of the parties who afterward
organized the Standard Oil Company. This line was built between their
office on the public square in Cleveland and their works over on the
Cuyahoga flats.

It seemed, however, to be the fate of the writer to make new inventions
that would supersede the old ones before they were fairly brought into
use. Very soon after the dial-telegraph began to be used, printing
telegraph instruments for private-line purposes superseded them. About
1867 a printing instrument was devised for stock reporting, which in one
of its forms is still in use. Soon after the invention of this form of
printer a company was organized to operate not only these
stock-reporting lines, but short lines for all sorts of private
purposes. Following the invention of the stock-reporting instrument
there were several adaptations made of the printing telegraph for
private-line purposes. Among others the writer invented one known as
"Gray's automatic printer," a cut and a description of which may be
found on page 684 in "Electricity and Electric Telegraph," by George B.
Prescott, published in 1877. This instrument was adopted by the Gold and
Stock Telegraph Company as their standard private-line printer. It was
first introduced in the year 1871, and at the time the telephone began
to be used there were large numbers of these printers in operation in
all of the leading cities and towns in the United States. While this has
been superseded to a large extent by the telephone, there are still a
few isolated cases where it is used.

Short lines have multiplied for all sorts of purposes, until to-day the
money invested in them largely exceeds the amount invested in the
regular commercial telegraphic enterprises.

The invention of the telephone created such a demand for short-line
service that some scheme had to be devised not only to make room for the
necessary wires, but to so cheapen the instruments as to bring them
within reach of the ability of the ordinary man of business.

This problem has been solved (but not without many difficulties) by the
inauguration of what is known as the "central station." By this system
one party simply controls a single wire from his office or residence to
the central station; here he can have his line connected with any other
wire running into this same station, by calling the central operator and
asking for the required number. It is useless to tell the public that
very often this number is "busy," and here is the great drawback to the
central-station system. This is especially true in large cities, where
there are a great number of lines. The switchboards in large cities are
necessarily very complicated affairs, and it requires a number of
operators to answer the many calls that are constantly coming in. Each
central-station operator presides over a certain section of the board,
and as this section has to be related in a certain way to every other
section, it is easy to see wherein arises the complication.

In large cities the central stations themselves have to be divided and
located in different districts, being connected by a system of trunk
lines.



CHAPTER XIX.

THE TELAUTOGRAPH.


So far we have described several methods of electrical communication at
a distance, including the reading of letters and symbols at sight (as by
the dial-telegraph and the Morse code embossed on a strip of paper);
printed messages and messages received by means of arbitrary sounds, and
culminating in the most wonderful of all, the electrical transmission of
articulate speech.

None of these systems, however, are able to transmit a message that
completely identifies the sender without confirmation in the form of an
autograph letter by mail.

In 1893 there was exhibited in the electrical building at the World's
Fair an instrument invented by the writer called the Telautograph. As
the word implies, it is a system by which a man's own handwriting may be
transmitted to a distance through a wire and reproduced in facsimile at
the receiving-end. This instrument has been so often described in the
public prints that we will not attempt to do it here, for the reason
that it would be impossible without elaborate drawings and
specifications. It is unnecessary to state that it differs in a
fundamental way from other facsimile systems of telegraphy. Suffice it
to say that as one writes his message in one city another pen in another
city follows the transmitting-pen with perfect synchronism; it is as
though a man were writing with a pen with two points widely separated,
both moving at the same time and both making exactly the same motions.
By this system a man may transact business with the same accuracy as by
the United States mail, and with the same celerity as by the electric
telegraph.

A broker may buy or sell with his own signature attached to the order,
and do it as quickly as he could by any other method of telegraphing,
and with absolute accuracy, secrecy and perfect identification.

In 1893, when this apparatus was first publicly exhibited, it operated
by means of four wires between stations, and while the work it did was
faultless, the use of four wires made it too expensive and too
cumbersome for commercial purposes; so during all the years since then
the endeavor has been to reduce the number of wires to two, when it
would stand on an equality with the telephone in this respect. It is
only lately that this improvement has been satisfactorily accomplished,
and, for reasons above stated, no serious attempt has been made to
introduce it as yet; but it has been used for a long enough time to
demonstrate its practicability and commercial value. Companies have been
organized both in Europe and America for the purpose of putting the
telautograph into commercial use.

By means of a switch located in each subscriber's office the wires may
be switched from a telephone to a telautograph, or vice versa, in a
moment of time. By this arrangement a man may do all the preliminary
work of a business transaction through the telephone, and when he is
ready to put it into black and white switch in the telautograph and
write it down. For ordinary exchange work this is undoubtedly the true
way to use the telautograph, because one system of wires and one
central-station system will answer for both modes of communication, and
in this way an enormous saving can be made to the public. There is no
question in the mind of any one who is familiar with the operation of
both the telephone and telautograph but that some day they will both be
used, either in the same or separate systems, as they each have
distinctly separate fields of usefulness,--the telephone for desultory
conversation, the telautograph for accurate business transactions. The
question may arise in the minds of experts how the two systems can be
worked in the same set of cables, and this leads us to discuss the
phenomena of induction.

Every one who has listened at a telephone has heard a jumble of noises
more or less pronounced, which is the effect of the working of other
wires in proximity to those of the telephone. If, when a Morse telegraph
instrument is in operation on one of a number of wires strung on the
same poles, we should insert a telephone in any one of the wires that
were strung on the same poles or on another set of poles even across the
street, we could hear the working of this Morse wire in the telephone,
more or less pronounced, according to the distance the wire is from the
Morse circuit. This phenomenon is the result of induction, caused by
magnetic ether-waves that are set up whenever a circuit is broken and
closed, as explained in Chapter VI.

The telephone is perhaps the most sensitive of all instruments, and will
detect electrical disturbances that are too feeble to be felt on almost
any other instrument, hence the telephone is preyed upon by every other
system of electrical transmission, and for this reason has to adopt
means of self-protection. It has been found that the surest way to
prevent interference in the telephone from neighboring wires is to use
what is called a metallic circuit--that is to say, instead of running a
single wire from point to point and grounding at each end, as in
ordinary telegraph systems, the telephone circuit is completed by using
a second wire instead of the earth.

As a complete defense against the effects of induced currents the wires
should be exactly alike as to cross-section (or size) and resistance.
They should be insulated and laid together with a slight twist. This
latter is to cause the two wires so twisted to average always the same
distance from any contiguous wire.

One factor in determining the intensity of an induced current is the
distance the wire in which it flows is from the source of induction. A
telephone put in circuit at the end of the two wires that are thus laid
together will be practically free from the effects of induced currents
that are set up by the working of contiguous wires--for this reason:
Whenever a current is induced in one of the slack-twisted wires it is
induced in both alike; the two impulses being of the same polarity meet
in the telephone, where they kill each other. In order to have a perfect
result we must have perfect conditions, which are never attained
absolutely, but nearly enough for all practical purposes.

In the early days of telephony great difficulty was experienced in using
a single wire grounded at each end in the ordinary way, if it ran near
other wires that were in active use. As time passed on and the electric
light and electric railroad came into operation these difficulties were
immensely increased, till now in large cities the telephone companies
are fast being driven to the double-wire system, which will soon become
universal for telephonic purposes the world over, except perhaps in a
few country places where there is freedom from other systems of
electrical transmission. To successfully work the telephone and
telautograph through the same cables, these protective devices against
induction must be very carefully provided and maintained.



CHAPTER XX.

SOME CURIOSITIES.


Until within recent years it was never supposed that a sunbeam would
ever laugh except in poetry. But the modern scientist has taken it out
of the realm of poetry and put it into the prosy play of every-day life.
The Radiophone, invented by A. G. Bell, is an instrument by which
articulate or other sounds are transmitted through the medium of a ray
of light. It has as yet no practical application and has never gone
beyond the experimental stage, but as a bit of scientific information it
is very interesting.

If we introduce into an electric circuit a piece of selenium, prepared
in a certain way, its resistance as an electric conductor undergoes a
radical change when a beam of sunlight is thrown upon it. For instance,
a selenium cell, so called, that in the dark would measure 300 ohms
resistance, would have only about 150 ohms when exposed to sunlight.
This amount of variation in a short circuit of low resistance would
produce a considerable change in the strength of a current passing
through it from a battery of a given voltage.

If now we connect a selenium cell to one pole of a battery, and thence
through a telephone and back to the other pole, we have completed an
electric circuit, of which the selenium cell is a part, and any
variation of resistance in this cell, if made suddenly, will be heard in
the telephone. Let the diaphragm of a telephone transmitter have a very
light, thin mirror on one side of it, and a beam of sunlight be thrown
upon it and reflected from that on to the selenium cell, which may be
some distance away. Then, if the diaphragm is thrown into vibration by
an articulate word or other sound, the light-ray is also thrown into
vibration, which causes a vibratory change of resistance in the selenium
cell in sympathy with the light-vibrations; and this in turn throws the
electric current into a sympathetic vibratory state which is heard in
the telephone. So that if a person laughs or talks or sings to the
diaphragm, the sunbeam laughs, talks and sings and tells its story to
the electric current, which impresses itself upon the telephone as
audible sounds--articulate or otherwise. Instead of the telephone,
battery and selenium cell, a block of vulcanite or certain other
substances may be used as a receiver; as a light-ray thrown into
vibration has the power to produce sound or sympathetic vibration in
certain substances.

Another curious application of the selenium cell has been attempted, but
has scarcely gone beyond the domain of theory. This apparatus, if
perfected, might be called a Telephote. It is an apparatus by which an
illuminated picture at one end of a line of many wires is reproduced
upon a screen at the other end. The light is not actually transmitted,
but only its effects. Suppose a picture is laid off into small squares
and there is a selenium cell corresponding to each square and for each
selenium cell there is a wire that runs to a distant station in which
circuit there is a battery. At the distant station there are little
shutters, one for each wire, that are controlled by the electric current
and so adjusted that when the cell at the transmitting-end is in the
dark the shutter will be closed. Now if a strong light be thrown upon
the picture at the transmitting-end, and each square of the picture
reflects the light upon its corresponding selenium cell, the high lights
of the picture will reflect stronger light than the shadows, and
therefore the wires corresponding to the high-light squares will have a
stronger current of electricity flowing through them, because the
resistance of the circuit is less than the ones connected with the
darker shadows. So that the degree of current-strength in the various
wires will correspond to the intensity of light reflected by the
different sections of the picture. The shutters are so adjusted that the
amount of opening depends upon the strength of current. The shutters
corresponding to the high lights of the picture will open the widest and
throw the strongest light upon the screen, from a source of light that
is placed behind the shutters. The shutters that open the least will be
those that are operated upon by the shadows of the picture. Inasmuch as
a picture thrown on a screen from a source of light is wholly made up of
lights and shadows, the theory is that this apparatus perfectly
constructed would transmit any picture to a distance, through
telegraph-wires. It must not be understood that the rays of light are
transmitted through the wires as sound-vibrations are. Light, per se,
can be transmitted only through the luminiferous ether, as we have seen
in the chapter on light in Volume II.

While we are talking about these curious methods of telegraphic
transmission, I wish to refer to an apparatus constructed by the writer
in 1874-5, for the purpose of receiving musical tones or compositions
transmitted from a distance through a wire by electricity. (A cut of
this apparatus is shown on page 875 of "Electricity and Electric
Telegraph," by Prescott, issued in 1877.) It consists of a disk of
metal rotated by a crank mounted on a suitable stand. The electric
circuit passes through the disk to the hand of the operator in contact
with it, thence running through the line-wire to the distant station.
Now, if a tune is played at that station, upon an electrical key-board,
as described in a previous chapter, and the disk rotated with the
fingers in contact with it, the tune or other sounds will be reproduced
at the ends of the fingers. After the telephone was invented and put
into use I used this revolving disk as a receiver for speech as well as
music, and by this means persons may carry on an oral conversation
through the ends of their fingers. This apparatus has been confounded in
the minds of some people with Edison's electromotograph. The phenomena
of the electromotograph were produced by chemical effects, while that of
the apparatus just described is electrostatic in its action. The
electrostatic disk was made in the winter of 1873-4, while Edison's
electrochemical discovery was made some time later.



CHAPTER XXI.

WIRELESS TELEGRAPHY.


Broadly speaking, "Wireless Telegraphy" is any method of transmitting
intelligible signals to a distance without wires; and this includes the
old Semaphore systems of visual signals, such as flags and long arms of
wood by day, and lights by night; also the Heliograph (an apparatus for
flashing sunlight), and Sound Signals, made either through the air or
water. Electrical conduction, either through rarefied air or the earth,
also comes under this heading.

The name "Wireless Telegraphy," however, is specifically applied to a
system of signaling by means of ether-waves induced by electrical
discharges of very high voltage. Ether-waves of a greater or less degree
are always set up whenever there are sudden electrical disturbances,
however slight. Ether-waves, electrically induced, are probably as old
as the universe. When "there were thunders and lightnings" from the
cloud that hovered over Mount Sinai in the time of Moses, ether-waves of
great power were sent out through the camp of Israel. But the people of
those days had no "coherer" or telephone or any other means of
converting these waves into visual or audible signals. Thousands of
years had to elapse before the intellect of man could grasp the meaning
of these natural phenomena sufficiently to harness them and make them
subservient to his will.

Many people have been powerfully "shocked"--some even killed--by the
impact of ether-waves set up by powerful discharges of lightning between
the clouds and the earth--when they were not in the direct path of the
lightning-stroke.

The history of Electro-Wireless Telegraphy, like that of all inventions,
is one of successive stages, and all the work was not done by one man.
The one who gets the most credit is usually the one who puts on the
finishing touches and brings it out before the public. He may have done
much toward its development or he may have done but little.

In the year 1842 Morse transmitted a battery current through the water
of a canal eighty feet wide so as to affect a galvanometer on the
opposite side from the battery. This was wireless telegraphy by
_conduction_ through water.

In 1835 Joseph Henry produced an effect on a galvanometer by ether-waves
through a distance of twenty feet by an arrangement of batteries and
circuits like that shown in Fig. 1, Chapter VI. This was called
_induction_, and is still so called when electrical effects are produced
from one wire to another through the ether for short distances. All
induction-coils and transformers (see Chapter XXIV) are operated by
effects produced through the ether from the primary to the secondary
coil--but through very short distances.

In 1880 Professor Trowbridge transmitted an electrical current through
the earth for one mile so as to produce signals in a telephone. In
1881-2 Professor Dolbear used for a short distance (fifty feet)
substantially the same arrangement as Marconi now uses, except that the
former used a telephone as a receiver. He used an induction-coil having
one end of the secondary wire connected with the earth, while the other
was attached to a wire running up into the air. At the receiving-end a
wire starting from the earth extended into the air, passing through a
telephone, which acted as a receiver. In 1886 he used a kite to elevate
the wire, through which electrical discharges of high voltage were made
into the air to produce ether-waves--the receiver being 2000 feet away.
Dolbear's experiments were public fourteen years ago, but at that time
there was no interest in such matters, so that his work received little
or no attention. In 1887 Dr. Hertz of Germany made some experiments in
producing and detecting ether-waves, and he did a great deal to awaken
an interest in the subject, so that others began investigations that
have led to its present use as a means of telegraphing to a distance of
many miles.

In 1891 Professor Branly of Paris invented the coherer. In 1894 it was
improved by Lodge and by him used as a detector of ether-waves. In 1896,
ten years after Dolbear had used it with the kite at the
transmitting-end and telephone at the receiving-end, Marconi, an
Italian, substituted the coherer of Branly for the telephone of Dolbear.
This coherer is constructed and operated as follows:

It consists of a glass tube, of comparatively small diameter, loosely
filled with metal filings of a certain grade. This body of metal-dust is
made a part of a local battery circuit in which is placed an ordinary
electric bell or telegraphic sounder. The resistance of this body of
filings is so great that current enough will not pass through it to ring
the bell or actuate the sounder until an ether-wave strikes it and the
wire attached to it, when the metal particles are made to cohere to such
an extent that the conductivity of the mass is greatly increased; so
that a current of sufficient volume will now pass through the
bell-magnet to ring it. Before the next signal comes the filings must be
made to de-cohere; and to accomplish this a little "tapper," that works
automatically between the signals, strikes the glass tube with a
succession of light blows.

Briefly stated, the wireless system of Marconi, in its essentials,
consists of a powerful induction-coil with one end of the secondary wire
connected with the earth, while the other extends into the air a greater
or less distance according to the distance it is desired to send
signals. The greater the distance the higher the wire should extend into
the air. At the receiving-end a wire of corresponding height is erected,
also connected with the earth. In this wire--as a part of its
circuit--is placed the coherer. In a local circuit that is connected to
the upright wire in parallel with the coherer is placed a battery, a
sounder, or a bell, that is rung when the filings cohere.

When an ether-wave is set up by a discharge of electricity into the air
it strikes the perpendicular wire of the receiver, and that portion of
the wave that strikes is converted into electricity, which is called an
induced current. It is this current, as it discharges through the
coherer to the earth, that causes the filings to unite so as to close
the local circuit and operate the sounder. To send a message it is only
necessary to make the discharges into the air, at the sending-end,
correspond to the Morse alphabet.

While Marconi has done more than any other man to improve and popularize
wireless telegraphy, history shows that he invented none of the
essential elements so far as the system has been made public.

What he seems to have really done was to substitute the coherer of
Branly and Lodge, with its adjuncts, for the telephone of Dolbear. There
is no doubt but that Marconi has done much to improve and enlarge the
capacity of the apparatus and to demonstrate to the world some of its
possibilities. He has been an indefatigable worker and deserves great
credit; but without the work of those who preceded him he could not have
succeeded: the honors should be divided.

This system has been used at various times for reporting yacht-races,
and between ships. It is said also to have been used to some extent in
the South African War. There is much to be done yet, however, before it
can be made entirely reliable for defensive work in time of war. As it
is now, all an enemy would have to do to destroy its usefulness would be
to set an ether-wave-producer to work automatically anywhere within the
"sphere of influence" of the system--to speak diplomatically--when it
would render unintelligible any message that should be sent. To make the
system of the greatest value some sort of selective receiver must be
invented that will select signals sent from a transmitter that is
designed to work with it.

There is no doubt but that wireless telegraphy will some time play an
important part in many spheres of usefulness.

There is another mode (already referred to) for transmitting signals
electrically without wires through the earth instead of through the air,
but in this case it is not through the medium of induction, but
conduction. It has been explained in former chapters that earth-currents
are constantly flowing from one point to another where the potentials
are unequal. Sometimes these inequalities of potential are caused by
heat and sometimes by electricity, as in the case of a thunder-storm. If
a cloud is heavily charged with positive electricity, say, the earth
underneath will have an equal charge of negative electricity. Let us
illustrate it by the tides. As the moon passes over the ocean it
attracts the water toward it and tends to pile up, as it were, at the
nearest point between the earth and the moon. Suppose that (while the
water is thus piled up at a point under the moon) we could suddenly
suspend the attraction between the earth and the moon--the water would
begin immediately to flow off by the force of gravitation until it had
found a common level. Suppose in the place of the moon we have a cloud
containing a static charge of positive electricity--it attracts a
negative charge to a point on the earth nearest the cloud. If now a
discharge takes place between the earth and cloud the potential between
the two will suddenly become equalized and the static charge that was
accumulated in the earth is released and it dissipates in every
direction, seeking an equilibrium, following the analogy of the water;
the difference being that in one case the movement is very slow, while
in the other it is as "quick as lightning."

About eighteen years ago I had a short telephone-line between my house
and that of one of my neighbors. This line was equipped with what was
known in those days as magneto-transmitters, such as we have described
in a previous chapter on the subject of telephony. When a line is
equipped in this way no batteries are needed, as the voice generates the
current, on the principle employed in the dynamo-electric machine. Often
on summer evenings, when the sky appears to be cloudless, we can see
faint flashes of lightning on the horizon, an appearance which is
commonly called "heat-lightning." As a matter of fact, I do not suppose
there is any such thing as heat-lightning, but what we see is the effect
of very distant storm-clouds. Often at such times I have held the
telephone receiver to my ear and could hear simultaneously with each
flash a slight sound in the telephone. This effect could be produced in
the earth by a simple discharge between two or more clouds, which would
distribute the electrical discharge over a greater area. And because my
line had connection with the earth it could have been disturbed
electrically by conduction instead of induction; or it may have been the
effect of ether-waves set up by the lightning discharges. There is no
doubt in my mind but that both of these effects (ether-waves and
conduction through earth) may be felt when a discharge takes place
between a cloud and the earth.

If we could, by operating an ordinary telegraphic key, cause the
lightning to discharge from cloud to earth, and some one was listening
at a telephone in a circuit that was grounded at both ends 100 miles or
more distant from the cloud, the man who controlled the discharges by
the key could transmit the Morse code through the earth to the man who
was listening at the telephone. Thousands of people might be listening
at telephones in every direction from the transmitting-station, and they
would all get the same message. If the receiving-station is near to the
point where there is a heavy discharge from the clouds to the earth the
earth-current is very strong--flowing out in every direction. For some
years I had an underground line between my house and laboratory, and no
part of the line between the two stations was above ground. Many and
many times during the prevalence of a thunder-storm have the
telephone-bells been made to ring at both ends of the line by a
discharge from the cloud to the earth, and in some cases the discharge
was several miles away. The wires could not have been affected so
powerfully in any other way than through the earth.

It will be seen by the foregoing statements that it is possible to
transmit messages through the earth for long distances, but the
difficulty in the way of its becoming a general system is twofold.
First, we cannot always have a thunder-cloud at hand from which to
transmit our signals, and, secondly, the signals would be received alike
at every station simultaneously.



CHAPTER XXII.

NIAGARA FALLS POWER--INTRODUCTION.


As our readers know, Niagara Falls is situated upon the Niagara River,
which is the connecting-link between Lake Erie and Lake Ontario. The
surface of Lake Erie lies 330 feet above that of Lake Ontario. The high
level upon which Lake Erie is situated abruptly terminates at
Queenstown, which is near the point where the Niagara River empties into
Lake Ontario. From Lake Erie to the falls the level of the river is
gradually lowered a little less than 100 feet, and most of this (making
"the rapids") occurs in the last mile above the point where it takes a
perpendicular plunge of 165 feet into a narrow gorge extending for seven
miles, through which the river runs, gradually falling also 100 feet in
that distance. The river above the falls is broad, varying from one to
three miles in width, but below that point it is suddenly narrowed up to
a distance of from 200 to 400 yards.

It is supposed that at one time the fall was situated at the bluff
overlooking Queenstown, near Lake Ontario, and at that time was very
much higher than it is at present. Through long ages of time the water
has gradually eaten away the rock, thus forming the gorge. It is
estimated by different geologists that the time required to wear away
the rock back to the present position of the fall has required from
15,000 to 35,000 years. Some authorities place the rate of wear at three
feet per annum and others not more than one. It is well known, however,
that this erosion is constantly going on, and if nothing is done to
check it the time will come when the gorge will extend up to Lake Erie
and drain it, practically, to the bottom. This is a matter, however,
that the people of this and those of several succeeding generations need
not worry about.

In the early days, before the country was settled and the banks of the
river were lined with trees, and no houses, hotels or horse-cars were to
be seen; when the puffing of the locomotive was not heard echoing from
shore to shore; when no bridges spanned the river to mar its beauty, and
when nature was the only architect and beautifier, Niagara Falls must
have been one of the most attractive spots on the earth; at least it is
the place of all places where the mighty energies of nature are gathered
together in one grand exhibition of sublime power. Here for ages this
same grand exhibition had been going on, and although there was no
human eye to see it, those of us who believe that nature is not a thing
of chance, but that it was planned by an intelligence infinitely
superior to that of any man, can easily imagine that the Great Architect
and beautifier of this same nature, not only plans but enjoys the work
of His own hand. Why not? For ages the same sun, in his daily round, has
reflected that beautifully colored rainbow, here the product of sunshine
and mist. The same water, through these successive ages, has been lifted
to the clouds by the power of the sun's rays, and has been carried back
to the fountain-heads on the wings of the wind, and there has been
condensed into raindrops, that have fallen on land, lake and river, and
in turn has been carried over this same waterfall in its onward course
toward the sea, only again to be caught up into the clouds; and thus
through an eternal round it has been kept moving by that mighty engine
of nature, the sun. It is said that "the mill will never grind with the
water that has passed." This is true only in poetry. As a matter of
fact, "the water that has passed" may often return to help the mill to
grind again.

Water-powers have been utilized in a small way for many years for the
purpose of generating electricity through the medium of the dynamo, but
nowhere in the world has the application of the force been made for this
purpose on such a grand scale as at Niagara Falls. When one stands on
the bank of the river and sees the great waterfall as it plunges over
the precipice, exerting a force of from five to ten million horse-power,
one is overwhelmed in contemplation of its possibilities as a source of
energy that may be converted into work, mechanical and chemical, through
the medium of electricity.

The genius of man has devised a way by which some of this constantly
wasting energy may be converted into electricity and distributed to
different points to perform various kinds of work. But the amount
utilized as yet is scarcely a drop when compared with that which might
be if the whole torrent could be set to work in the same manner as a
very small portion of it now is.



CHAPTER XXIII.

NIAGARA FALLS POWER--APPLIANCES.


Some years ago a company was formed for the purpose of utilizing, to
some extent, this greatest of all water-powers. A tunnel of large
capacity was run from a point a short distance below the falls on a
level a little above the river at that point. The general direction of
this tunnel is up the river; it is about a mile and one-half in length,
terminating at a point near the bank of the river a mile or more above
the falls. Above the end of this tunnel an upright pit comes to the
surface, where a power-house of large dimensions has been constructed of
solid masonry. It is long enough at present to contain ten dynamos of
mammoth size. Along the side of this power-house a deep broad canal is
cut, which communicates with the river at that point, and through which
flows the water that is to furnish the power. Of course the water level
of this canal is the same as that of the river.

The foundations of the power-house extend to the bottom of the tunnel,
which at that point is 180 feet below the surface of the ground. To put
it in other words, the cellar or pit under the power-house is 180 feet
deep and communicates with the great tunnel, which has its outlet below
the falls.

Each of the ten dynamos is driven by a turbine water-wheel situated near
the bottom of the pit heretofore described. The turbine-wheel is on the
lower end of a continuous shaft, which reaches from a point near the
bottom of the tunnel to a point ten or fifteen feet above the floor of
the power-house (which is about on a level with the surface of the
ground).

This shaft is incased in a water-tight cylinder of such diameter as will
admit a sufficient amount of water, and connects with the turbine wheel
at the bottom in the ordinary way. The water is admitted into the top of
this cylinder from the canal, so that the wheel is under the pressure of
a falling column of water over 140 feet high. The water, forcing its way
out at the bottom through the turbine, revolves it and its long,
upward-reaching shaft with great power, and enables it to work the
dynamos in the power-house above, as will be described. The water
discharges through the wheel in such a manner as to lift the whole
shaft, thus taking away the tremendous end-thrust downward that would
otherwise interfere greatly with the running of the machine through
friction. After the water has done its work it flows off through the
tunnel into the river below the falls.

To the upper end of the power-shaft is attached a great revolving
umbrella-shaped hood; to the periphery (circumference) of this hood is
attached a forged steel ring, 5 inches in thickness, about 12 feet in
diameter and from 4 to 5 feet in width. The whole of the revolving
portion--including the ring upon which are mounted the field-magnets,
the hood, and the shaft running to the bottom of the pit, where the
turbine wheel is attached--weighs about thirty-five tons.

The dynamos belong to the alternating type, and are comparatively simple
in construction. In a previous chapter upon the dynamo it was stated
that the fundamental feature was the relation that the field-magnet and
the armature sustained to each other, and that in some cases the
field-magnet revolves while the part that is technically called the
armature remains stationary. In other cases the armature revolves and
the field-magnets are stationary. In the latter case brushes and
commutators are used, to catch and transfer the generated electricity,
while in the former these are not needed, which simplifies the
construction of the machine.

As we have stated, the dynamos used at Niagara are constructed with
revolving field-magnets that are bolted on to the inner surface of the
steel ring that is carried by the hood, so that there are no brushes
connected with the machine except the small ones used to carry the
current to the field-magnets.

The current for power purposes is generated in a large stationary
armature about ten feet in diameter and of the same depth as the
revolving ring. The revolutions of the ring send out currents of
alternating polarity, and each of the ten machines will furnish
electrical energy equal to 5000 horse-power, so that when the work that
is now under way is completed 50,000 horse-power can be furnished in the
form of electricity. About 35,000 horse-power is now actually delivered
to the various industrial enterprises. The dynamos are set horizontally,
since the shaft which connects them with the turbine wheel stands in a
perpendicular position.

Not all of the energy that is developed by the water-wheel is converted
into electricity, but some of it appears as heat. In order to prevent
the heat from becoming so great as to be dangerous to the machine it
must be constructed in such a way as to admit of sufficient ventilation
for cooling purposes. The armature is so constructed that there are
air-passages running all through it, and on top of the revolving hood
are two bonnet-shaped air-tubes set in such a way as to force the air
down through the armature, which carries off the heat and warms the
power-house, on the principle of a hot-air furnace. This great
machine--which, in a way, is so simple in its construction--when in
action conveys to the mind of the beholder a sense of wonderful power.
It is only when we stand in the presence of such exhibitions as may be
seen in this power-house, devised and executed by the genius of man, and
in that greater presence, the mighty Falls of Niagara, that we get
something of a conception of the power of the silent yet potent energy
of the great king of daylight, the sun.

There are very many interesting details that work in connection with
this great power-plant, some of which we will describe, in a general
way.

Standing within a few feet of each one of the great dynamos is a very
beautifully constructed piece of machinery called the governor. The
governor regulates the speed of the dynamos by partially opening and
closing the water-gates that regulate the flow of water into the
turbines. The question may be asked, why is there any regulation needed,
if there is always an even head of water? There are two reasons--one
because the load on the dynamo is constantly changing, and another that
the head of water changes, although this latter fluctuation is in long
periods. If the circuit leading out from the dynamo is broken, the
rotating part of the dynamo will move with great ease and little power,
as compared with what is required when the circuit is closed, and the
current is going out and doing work. The increased amount of energy that
will be required to keep the dynamo moving at a certain rate of speed
when the load is on--in other words, when the circuit is closed--will
depend upon the amount of current that is going out from the dynamo to
perform work at other points. As the amount of current used outside for
the various purposes is constantly changing, it follows that the load on
the dynamo is constantly changing also. As the load changes, the speed
will change, unless the amount of water that is flowing into the turbine
is changed in a like proportion; hence the necessity for a governor that
will perform this work. You can easily imagine that it will require a
great amount of power to move the gate up or down with such a pressure
of water behind it. It is not possible here to explain the operation of
the governor in detail, as that could not be done without elaborate
drawings; suffice it to say that the whole thing is controlled by a
small ball governor such as we see used in ordinary steam-engines for
regulating steam-pressure.

The rising or falling of the balls of this governor to only a very
slight extent will bring into action a power that is driven by the
turbine itself, which is able to move the water-gate in either direction
according as the balls rise or fall. For instance, if the balls rise
beyond their normal position, it shows that the dynamo is increasing in
speed, and immediately machinery is brought into action that shuts the
water off in a small degree, just enough to bring the speed back to
normal. If the balls drop to any extent, it shows that the load is too
great for the amount of water, and that the dynamo is decreasing in
speed; immediately the power is brought into action, now in the opposite
direction, and the water-gate is opened wider. These slight variations
of speed are constantly going on, and the constant opening and closing
of the gate follows with them. It is a beautiful piece of machinery, and
is beautifully adapted to the work it has to perform. It is continually
standing guard over this greater piece of machinery that is exerting an
energy of 5000 horse-power and prevents it from going wrong, both in
doing "that which it should not do and leaving undone that which it
should do." It is a machine that, when in action, points a moral to
every thinking person who beholds it. Every man has such a governor if
he only has the inclination to use it.

I have said further back that the water-head varies, but usually at long
periods. This variation is chiefly caused by changes of wind, and it is
very much greater than one would suppose without studying the causes.
Lake Erie lies in an easterly and westerly direction, and when the wind
blows constantly for a time from the west, with considerable force, the
water piles up at the eastern end of the lake, which causes the level of
the Niagara River to rise to a very sensible extent. It is not so
noticeable above the falls as below, because of the great difference in
the width of the river at these two points. Sometimes the river below
the falls, as it flows through the narrow gorge, will vary in height
from twenty to forty feet. When the wind stops blowing from the west and
suddenly changes and blows from the east, it carries the water of the
lake away from the east toward the west end, which will produce a
corresponding depression in the Niagara River. No doubt there is an
effect produced by the difference of annual rainfall, but the effect
from this cause is not so marked as that from the changing winds.

Another appliance used in the power-house, chiefly for handling heavy
loads and transferring them from one point to another, is called the
electric crane. It is mounted upon tracks located on each side of the
power-house. The crane spans the whole distance, and runs on this track
by means of trucks from one end of the power-house to the other. Running
across this crane is another track which carries the lifting-machinery,
consisting of block and tackle, able to sustain a weight of fifty tons.
Situated at one end of the crane are one or more electric motors, which
are able, under the control of the engineer, to produce a motion in any
direction, which is the resultant of a compound motion of the two cars
acting crosswise to each other together with the perpendicular motion of
the lifting-rope connected with the block and tackle. It seems like a
thing endowed with human reason, when we see it move off to a distant
part of the building, reach down and pick up a piece of metal weighing
several tons, carry it to some other portion of the building and lower
it into place, to the fraction of an inch. While the machine itself does
not reason, there is a reasoning being at the helm, who controls it and
makes it subservient to his will. The machine is to the engineer who
manipulates it what a man's brain is to the man himself. The brain is
the instrument through which the unseen man expresses his will and
impresses his work upon men and things in the visible world.



CHAPTER XXIV.

NIAGARA FALLS POWER--APPLIANCES.


In the last chapter I described some of the appliances used in
connection with the power-house. There are many things that are
commonplace as electrical appliances when used with currents of low
voltage and small quantity, that become extremely interesting when
constructed for the purpose of handling such currents as are developed
by the dynamos used at Niagara. For instance, it is a very commonplace
and simple thing to break and close a circuit carrying such a current as
is used for ordinary telegraphic purposes, but it requires quite a
complicated and scientifically constructed device to handle currents of
large volume and great pressure. If such a current as is generated by a
dynamo giving out 5000 horse-power under a pressure of 2200 volts should
be broken at a single point in a conductor, there would be a flash and a
report, attended with such a degree of heat and such power for
disintegration that it would destroy the instrument.

The circuit-breakers used at Niagara are constructed with a very large
number of contacts made of metal sleeves, or tubes, say one inch in
diameter, so constructed that one will slide within the other; the
sleeves being slotted so as to give them a little spring that secures a
firm contact. These are all connected together electrically, on each
half of the switch, as one conductor, so that when the switch is closed
the current is divided into as many parts as there are points of contact
in the switch. Suppose there are 100 of these contact-points, a
one-hundredth part of the current would be flowing through each one of
them. If, now, these points are so arranged that they can be all
simultaneously separated, the spark that will occur at each break will
be very small as compared with what it would be if the whole current
were flowing through a single point, and it would be so small that there
would be no danger attending the opening of the switch. These switches
are carefully guarded, being boxed in and under the control of a single
individual.

There is another apparatus that is a necessary part of every
manufacturing or other kind of plant that uses electricity from this
power-house, and this is called the transformer. Many of you are
familiar with the box-shaped apparatus that is used in connection with
electric lighting when the alternating current is used. Where simply
heating effects are required, such as in electric lighting, for
instance, the alternating current can be used to greater advantage than
the direct current when it has to be carried to some distance, owing to
the fact that it may be a current of high voltage. A greater amount can
be carried through a small conductor; thus greatly reducing the cost of
an electrical plant that distributes power to a distance. A transformer
is an apparatus that changes the current from one voltage to another.

In the ordinary electric-light plant, such as is used in a small town or
village, the current that is sent out from the power-station has a
pressure of from 1000 to 1500 volts, according to the distance to which
it is sent. It would not do, however, for the current to enter a
dwelling at this high pressure, because it is dangerous to handle, and
the liability to fires originating from the current would be greatly
increased. At some point, therefore, outside of the building, and not a
great distance from it, a transformer is inserted which changes the
voltage, say, from 1000 down to 50 or 100, according to the kind of
lamps used. Some lamps are constructed to be used with a current of
fifty volts and others for 100 or more. The lamp must always be adapted
to the current or the current to the lamp, as you choose. The human body
may be placed in a circuit where such low voltage is used without
danger, but it would be exceedingly dangerous to be put in contact with
a pressure of 1000 or more volts, such as is used for lighting purposes.

In principle the transformer is nothing more or less than an
induction-coil on a very large scale. The ordinary induction-coil, such
as is used for medical purposes, is ordinarily constructed by winding a
coarse wire around an iron core. This core is usually made of a bundle
of soft iron wires, because the wires more readily magnetize and
demagnetize than a solid iron core would. Around this coil of coarse
wire, which we call the primary coil, is wound a secondary coil of finer
wire. If now a battery is connected with the primary coil, which is made
of the coarse wire, and the circuit is interrupted by some sort of
mechanical circuit-breaker, each time the primary or battery circuit is
opened there will be a momentary impulse in the secondary circuit of a
much higher voltage; and at the moment the primary circuit is closed
there will be another impulse in this secondary circuit in the opposite
direction. The latter impulse is called the initial and the former the
terminal impulse. A current created in this manner is called an
_induced_ current. The initial current is not so strong as the terminal
in this particular arrangement.

If we should take hold of the two wires connected with the two poles of
the battery and bring them together so as to close the circuit, and then
separate them so as to break it we should scarcely feel any
sensation--if there were only one or two cells, such as are ordinarily
used with such coils. But if we connect these wires to the coils of the
induction apparatus and then take hold of the two ends of the secondary
coil and break and close the primary circuit we should feel a painful
shock at each break and close, although the actual amount of current
flowing through the secondary wire is not as great as that which flows
through the primary; but the voltage (or electromotive force) is higher,
and thus is able to drive what current there is through a conductor of
higher resistance, such as the human body. For this reason there is more
current forced through the body, which is a poor conductor, than can be
by a direct battery current which has a lower voltage. If now we should
take a battery of a number of cells, so as to get a voltage equal to
that given off by the secondary coil, and connect it with the fine-wire
coil instead of the coarse-wire coil--thus making what was before the
secondary coil the primary--by breaking and closing the battery circuit
as before we shall get a secondary or induced current in the coarse-wire
coil, but it will be a current of low voltage, and will not produce the
painful sensation that the secondary coil did.

We have now described the principle of a transformer as it is worked out
in an ordinary induction-coil. As has been stated, at Niagara Falls the
current comes from the dynamos with an electromotive force or pressure
of 2200 volts. For some purposes this voltage is not high enough, and
for other purposes it is too high; therefore it has to be transformed
before it is used! For some purposes this transformation takes place in
the power-house, and for others it takes place at the establishment
where it is used. For instance, take the current that is sent to
Buffalo, a distance of from twenty to thirty miles. The current first
runs to a transformer connected with the power-house, where it is
"stepped-up" (to use the parlance of the craft) from a voltage of 2200
to 10,000. It is carried to Buffalo through wire conductors that are
strung on poles, and is there "stepped-down" again through another
transformer to the voltage required for use at that place. The object of
raising the voltage from 2200 to 10,000 in this case is to save money in
the construction of the line of conductors between the two points. If
the voltage were left at 2200--the conductors remaining the same as they
are now--the loss in transmission would be very great, owing to the
resistance which these wires would offer to a current of such
comparatively low voltage as 2200. To overcome this difficulty--if the
voltage is not increased--it would be necessary to use conductors that
are very much larger in cross-section (thicker) than the present ones
are. And as these conductors are made of copper the expense would be too
great to admit of any profit to the company.

If we go back to an illustration we used in one of the early chapters on
electricity we can better explain what takes place by increasing the
voltage. If we have a column of water kept at a level say of ten feet
above a hole where it discharges, that is one inch in diameter, a
certain definite amount of water will discharge there each minute. If
now we substitute for the hole that is one inch in diameter one that is
only one-half inch in diameter a very much smaller amount of water will
discharge each minute, if the head is kept at the same point--namely,
ten feet. But if now we raise the column of water we shall in time reach
a height which will produce a pressure that will cause as much water to
discharge per minute through the one-half-inch hole as before discharged
through the one-inch hole with only the pressure of a ten-foot column.
This is exactly what takes place when the voltage is "stepped-up," which
is equivalent to an increase of pressure.

It will be seen from the foregoing that these transformers have to be
made with reference to the use the current is to be put to. In general
shape they are alike in appearance, the difference being chiefly in the
relation the primary sustains to the secondary coils. There is another
kind of transformer that is used when it is necessary to have the
current always running in the same direction. This transformer, as
heretofore explained, does not change the voltage of the current, but
simply transforms what was an alternating into a direct current. By
alternating current we mean one that is made up of impulses of
alternating polarity--first a positive and then a negative. The direct
current is one whose impulses are all of one polarity. The direct
current is required for all purposes where electrolysis (chemical
decomposition by electricity, as of silver for silver-plating, etc.) is
a part of the process. The alternating current may be used without
transformation in all processes where heat is the chief factor. For
motive power either current may be used, only the electromotors have to
be constructed with reference to the kind of current that is used.

The rotary transformer, which may be driven by any power, consists of a
wheel carrying a rotating commutator so arranged with reference to
brushes that deliver the current to the commutator and carry it away
from the same, that the brushes leading out from the transformer will
always have impulses of the same polarity delivered to them. In the
parlance of the craft, the transformers that are used to change the
voltage from high to low, or vice versa, are called "static
transformers," simply because they are stationary, we suppose. The
others are called rotary, or moving transformers, to distinguish them
from the other forms. The operation of the latter is purely mechanical,
while the former is electrical. In some instances where the static
transformers are very large they develop a great amount of heat, so much
that it is necessary to devise means for dissipating it as fast as
created. In some instances this is done by air-currents forced through
them, but in others, where they are very large, oil is kept circulating
through the transformer from a tank that is elevated above it, the oil
being pumped back by a rotary pump into the tank where it is cooled by a
coil of pipe located in the oil, through which cold water is continually
circulating. By this means cold oil is constantly flowing down through
the transformer, where it absorbs the heat, which in turn is pumped back
into the tank, where it is cooled.

Having now traced the energy from the water-wheel through the various
transformations and having described in a very general way the apparatus
both for generating electricity and for transforming it to the right
voltage necessary for the various uses to which it is put, we will
proceed in our next chapter to follow it out to the points where it is
delivered, and trace it through its processes, and the part it plays in
creating the products of these various commercial establishments.



CHAPTER XXV.

ELECTRICAL PRODUCTS--CARBORUNDUM.


The production of electricity in such enormous quantities as are
generated at Niagara Falls has led to many discoveries and will lead to
many more. Products that at one time existed only in the chemical
laboratory for experimental purposes, have been so cheapened by
utilizing electrical energy in their manufacture, as to bring them into
the play of every-day life. Still other products have only been
discovered since the advent of heavy electrical currents. A substance
called carborundum, which was discovered as late as 1891, has now become
the basis of an industry of no small importance. It is a substance not
unlike a diamond in hardness, and not very unlike it in its composition.
The chief use to which it is put is for grinding metals and all sorts of
abrasive work. It is manufactured into wheels, in structure like the
emery-wheel, and serves the same purpose. It is much more expensive than
the emery-wheel, but it is claimed that it will do enough more and
better work to make it fully as economical.

It was my pleasure and privilege to visit the factory at Niagara Falls,
and through the courtesy of Mr. Fitzgerald, the chemist in charge of the
works, I learned much of the manufacture and use of carborundum. The
crude materials used in the manufacture of carborundum are, sand, coke,
sawdust and salt; the compound is a combination of coke and sand. It
combines at a very high heat, such as can be had only from electricity.
When cooled down the product forms into beautiful crystals with
iridescent colors. The predominating colors are blue and green, and yet
when subjected to sunlight it shows all the colors of the solar spectrum
to a greater or less degree. The crystals form into hexagonal shapes,
and sometimes they are quite large, from a quarter to a half inch on a
side. The salt does not enter into the product as a part of the
compound, neither does the sawdust. The salt acts as a flux to
facilitate the union of the silica and carbon. The sawdust is put into
the mixture to render it porous so that the gases that are formed by the
enormous heat can readily pass off, thus preventing a dangerous
explosion that might otherwise occur. In fact, these explosions have
occurred, which led to the necessity of devising some means for the
ready escape of the gases.

The process of manufacture as it is carried on at Niagara is
interesting. The visitor is first taken into the rooms where are stored
the crude material, the sand, coke, sawdust and salt. The sand is of the
finest quality and very white. The coke is first crushed and screened,
the part which is reduced to sufficient fineness is mixed by machinery
with the right proportion of sand, salt and sawdust. The coarser pieces
of coke are used for what is called the core of the furnace, which will
be described later on.

This mixture is carried to the furnace-room, which has a capacity for
ten furnaces, but not all of these will be found in operation at one
time. Here the workmen will be taking the manufactured material from a
furnace that has been completed, and there another furnace is in process
of construction, while a third is under full heat, so that one sees the
whole process at a glance. These furnaces are built of brick, about
sixteen feet in length and about five feet in width and depth. The ends
and bed of the furnace are built of brick, and might be called
stationary structures. The sides are also built of brick laid up loosely
without mortar; each time the material is placed in the furnace, and
each time the furnace is emptied, the side-walls are taken down.

A furnace is made ready for firing by placing a mass of the mixture on
the bottom, and building the sides up about four feet high (or half the
height when it shall be completed). A trough, about twenty or twenty-one
inches wide and half as deep, is scooped out the whole length of the
pulverized stuff, and in this is placed what has before been referred to
as the core of the furnace, namely, pure coke broken into small pieces,
but not pulverized, as in the case of the other mixture. The amount used
is carefully weighed, so as to have the core the proper size that
experiment has proved to give the best results. The core is filled in
and rounded over till it is in circular form, being about twenty-one
inches in diameter. At each end of the furnace the core connects with a
number of carbon rods--about sixty in all--that are thirty inches long
and three inches in diameter. These carbon rods are connected with a
solid iron frame that stands flush with the outer end of the furnace. On
the inside the spaces between the rods are packed full of graphite,
which is simply carbon or coke with all the impurities driven out, so as
to make good electrical connections with the core. This core
corresponds, electrically speaking, to the filament in an ordinary
incandescent lamp, only it is fourteen feet long and twenty-one inches
in diameter. The mixed material is now piled up over this core, and the
walls at the sides are built up until the whole structure stands about
eight feet from the floor--a mass of the fine pulverized mixture, with
a core of broken coke electrically connected at the ends. It is now
ready for the application of electricity, which completes the work.

Let us go back to the transformer-room and examine the electrical
appliances that bring the current down to a proper voltage to produce
the heat necessary to cause a union between the silica of the sand and
the carbon of the coke, which results in the beautiful carborundum
crystals that we have heretofore described.

The current is delivered from the Niagara Power Company under a pressure
of 2200 volts. The conductors run first into the transformer-room, which
adjoins the furnace-room, and is there transformed down from 2200 volts
to an average of about 200 volts. The transformers at these works have a
capacity of about 1100 horse-power. About 4 per cent of this power is
converted into heat in the process of transformation, making a loss in
electrical energy of a little over 40 horse-power. This heat would be
sufficient to destroy the transformer if some arrangement were not
provided to carry it off. We have already described how this is done
through the medium of a circulation of oil. Because of the low voltage
and enormous quantity of the current passing from the transformer to the
furnace very large conductors are required. The two conductors running
to the furnace have a cross-section of eight square inches, and this
enormous current, representing over 1000 horse-power, is passed through
the core of the furnace, and is kept running through it constantly for a
period of twenty-four to thirty-six hours.

Let us consider for a moment what 1000 horse-power means; as this will
give us some conception of the enormous energy expended in producing
carborundum. A horse-power is supposed to be the force that one horse
can exert in pulling a load, and this is the unit of power. However, a
horse-power as arbitrarily fixed is about one-quarter greater than the
average real horse-power. If 1000 horses were hitched up in series, one
in front of the other, and each horse should occupy the space of twelve
feet, say, it would make a line of horses 12,000 feet long, which would
be something over two miles. Imagine the load that a string of horses
two miles long could draw, if all were pulling together, and you will
get something of an idea of the energy expended during the burning of
one of these carborundum furnaces.

Within a half hour after the current is turned on a gas begins to be
emitted from the sides and top of the furnace, and when a match is
applied to it, it lights and burns with a bluish flame during the whole
process. It is estimated that over five and one-half tons of this gas
is thrown off during the burning of a single furnace. This gas is called
carbon monoxide, and is caused by the carbon of the coke uniting with
the oxygen of the sand. When we consider the vast amount of material
that comes away from the furnace in the form of gas it is easy to see
why it is necessary to introduce sawdust or some equivalent material
into the mixture, in order to give the whole bulk porosity, so that the
gas can readily escape. We should also expect that after five and
one-half tons had been taken away from the whole bulk that it would
shrink in size. This is found to be the case. The top of the mass of
material sinks down to a considerable extent by the end of the time it
has been exposed to this intense heat. Gradually, after the current has
been turned on, the core becomes heated, first to a red, and afterwards
to an intense white heat. This heat is communicated to the material
surrounding the core, producing various effects in the different strata,
owing to the fact that it is not possible to keep a uniform heat
throughout the whole bulk of material. Some of it will be "overdone" and
some of it "underdone." The material which lies immediately in contact
with the core will be overheated, and that, which at one stage was
carborundum, has become disintegrated by overheating.

The silica of the compound has been driven off, leaving a shell of
graphitic substance formed from the coke.

After the current is shut off and the furnace has cooled down, a
cross-section through the whole mass becomes a very interesting study.
The core itself, owing to the intense heat it has been subjected to, has
had the impurities driven out of the coke, leaving a substance like
black lead, that will make a mark like a lead-pencil, and is really the
same substance, known as plumbago, in one of its forms. It is the carbon
left after the impurities have been driven out of the coke. Surrounding
the core for a distance of ten or twelve inches, radiating in every
direction, beautifully colored crystals of carborundum are found, so
that a single furnace will yield over 4000 pounds of this material.
Beyond this point the heat has not been great enough to cause the union
between the carbon and silica, which leaves a stratum of partly-formed
carborundum; outside of that the mixture is found to be unchanged.

These carborundum crystals are next crushed under rollers of enormous
weight, after which the crushed material is separated into various
grades for use in making grinding-wheels of different degrees of
fineness. This crushed material is now mixed with certain kinds of clay,
to hold it together, and then pressed into wheels of various sizes in a
hydraulic press, and afterward carried into kilns and burned the same
as ordinary pottery or porcelain. These wheels vary in size from one to
sixteen inches. The substances used as a bond in manufacturing wheels
are kaolin, a kind of clay, and feldspar.

While carborundum has already a large place as a commercial product,
there is no doubt but that the uses to which it will be put will vastly
increase as time goes on. This product may be called an artificial one,
and never would have been known had it not been for the intense heating
effects that are obtained from the use of electricity. It certainly
never could have been brought into play as one of the useful agencies in
manufacturing and the arts. It is not known to exist as a natural
product, which at first thought would seem a little strange in view of
the evidences of intense heat that at one time existed in the earth. Its
absence in nature is explained by Mr. Fitzgerald by the fact that "the
temperatures of formation and of decomposition lie very close
together."



CHAPTER XXVI.

ELECTRICAL PRODUCTS--BLEACHING-POWDER.


Another industry that has assumed large proportions at Niagara Falls,
owing to the vast quantity of electricity produced there, is the
manufacture of a commercial product called bleaching-powder, or chloride
of lime. Every one knows that chloride of sodium is simply common salt,
so extensively used wherever people and animals exist. Simple and
harmless as it is, while it exists as a compound of the original
elements, when separated into those elements they are each very
unpleasant and even dangerous substances to handle. Salt is one of the
most common substances in nature. It is found in many parts of the world
in solid beds, and is one of the prominent constituents of sea-water.

Salt is a compound of chlorine and a metal called sodium. Sodium in its
pure state has a strong affinity for oxygen, so much so that when a lump
of it is thrown into water it takes fire and burns violently with a
yellow flame. Chlorine, the substance with which it unites to form
common salt, is a greenish-colored gas, the fumes of which are very
offensive and very dangerous even to breathe, if the quantity is very
considerable.

It is a curious fact in nature that two such substances as chlorine and
sodium, both of them so difficult and dangerous to handle, should unite
together to form such a useful and harmless compound as common salt. The
important element in bleaching-powder is the chlorine which it contains.
It is extensively used in the manufacture of paper and in all other
materials where bleaching is required. The object of combining it with
lime, forming a chloride of lime, is simply to have a convenient method
of holding the chlorine in a safe and convenient manner until it is
needed for use.

The chemical works at Niagara Falls manufacture bleaching-powder on a
very large scale. The part that electricity plays is to separate the
chlorine from the sodium as it exists in common salt. At the works I was
first taken into a room where a large quantity of salt was stored. A
belt with little carrier-buckets on it picked up this salt and carried
it into another room, where it was thrown into a vast mixing-vat
containing water. The salt was mixed with water until a saturated
solution was obtained. In a large room, covering one-half acre or more
of ground, were assembled a great number of shallow vessels, about 4 by
5 feet square and 1 foot deep. These vessels were sealed up so that they
were gas-tight. Communicating with all of these vessels were pipes
connecting with the great tank containing the saturated solution of
salt.

From the top or cover of each vessel is a pipe running to a main pipe
that carries off the chlorine gas into another room as fast as it is
formed. Through each one of these vessels a current of electricity
passes; the whole system consuming about 2000 horse-power. The electric
current, as it passes through the brine, separates the chlorine from the
sodium, the chlorine passing in the form of gas up through the pipes,
before mentioned, into the main pipe, where it is carried into another
large room and discharged into a system of gas-tight chambers. Upon the
floor of these chambers is spread a coating of unslacked lime ground
into a fine powder. The lime has a strong affinity for the chlorine gas
and rapidly absorbs it, forming chloride of lime. When the lime is fully
saturated with the chlorine the gas is turned off from that chamber,
which is then opened up and the chloride taken out for shipment. A new
coating of lime is now spread in the chamber and the gas is turned on
and the process repeated.

There are a number of these chambers, so that the operation in all of
its phases is going on continuously. The room where the chlorine gas is
formed is thoroughly ventilated, a precaution which is very necessary in
case any one of the vats should spring a leak, as they sometimes do.

In each one of these vats where the electrolytic process is going on
there are two products constantly passing off; one, as before mentioned,
is chlorine gas, and the other caustic soda in solution. The solution in
the vat is constantly being renewed by the saturated solution of salt
from the reservoir before mentioned. There is one stream continuously
coming into the vat and two going out, caused by the decomposing power
of the electric current. The solution of caustic soda is carried to
large evaporating-pans, where the water is driven out of it, leaving the
caustic soda in dry, white sticks of crystalline formation. In this
process the electric current, which comes from the power-house with an
energy of 2000 horse-power, has to be transformed twice; first, to bring
it to the proper voltage for the work of decomposition, and, secondly,
to change it from an alternating to a direct current, by which all
electrolytic processes are carried on.

You will notice that the electrical energy expended in this
establishment is double that used in the manufacture of carborundum.

The caustic soda, which is one of the products from the decomposition of
salt, is taken to another establishment, where, by still another
electrical process, metallic sodium is manufactured. The process here
being a secret one, the writer did not have the privilege of examining
the details.



CHAPTER XXVII

ELECTRICAL PRODUCTS--ALUMINUM.


Another comparatively new article of manufacture now produced in large
quantities at Niagara Falls is aluminum. Until within the last few years
this metal was not used to any extent by manufacturers, because of the
great expense attending its production. Now, however, it is produced in
such quantities as to make it about as cheap as brass, bulk for bulk.
Aluminum is a very light metal, with a color somewhat lighter than
silver; its specific gravity being about one-third that of iron.
Aluminum is found in one of its compounds in great quantities in nature,
especially in certain kinds of clay and in a state of silicate, as in
feldspar and its associated minerals. It is found in great quantities in
southern Georgia, where it is mixed with the red oxide of iron that
abounds in that region. Here, it exists as alumina, which is an oxide of
aluminum. Before it is taken to the reduction-works the alumina is
separated from all other substances. It is a white powder, tasteless,
and not easily acted upon by acids.

Electricity is the chief agent in the production of metallic aluminum.
The reduction company buys this alumina, which has been separated from
the clay or ores where it is mined. In a large room there are located a
great number of iron vats or crucibles, lined with carbon, about two or
two and one-half feet deep, five or six feet long and four feet wide.

Immediately over each vat is constructed a metal framework, through
which are inserted a large number of carbon rods about eighteen or
twenty inches long and from two to two and one-half inches in diameter.
This framework is electrically insulated from the iron crucibles. The
framework and the carbons are connected with the positive conductor of
the electric current, and the vat or crucible with the negative. These
conductors are very large, something like a foot in width and an inch in
thickness, and made of some good conductor of electricity. They have to
be very large because they carry a current equal to 3050 horse-power.
The current is one of great volume, but very low voltage; the
electromotive force at each vat or crucible being only about seven
volts. As the process is electrolytic, and not simply a heating process,
the direct current must be used, and therefore the current coming from
the power-house must be transformed twice; first to bring it to a
proper voltage and secondly to change it from an alternating to a direct
current. These iron vats or crucibles are connected up in series,
electrically, and then they are filled with the alumina and certain
other materials, which act either as a flux or as a means of increasing
the conductivity of the mixture; just what this substance is, is
probably one of the secrets of the process. When all of the crucibles
are filled with the mixture the current is turned on and is kept on
continuously night and day seven days in the week. All of the material
in the different crucibles is heated to redness, when the process of
separation takes place. The oxygen of the alumina is thrown off as a
gas, and other residuum floats to the top of the crucible and is skimmed
off.

Metallic aluminum in a melted state sinks to the bottom of the crucible,
where it is dipped out from time to time with large iron ladles and
poured into sand and molded into blocks similar to that of pig iron.
From time to time, as the metal is dipped out, fresh alumina with the
other substances are thrown in on top of the crucible, so that the
process is continually going on, day and night, week in and week out.
The heat in the process of reducing alumina, as we have before seen, is
not the chief factor; it simply serves to reduce the compound to a fluid
state so that the electrolytic action can readily take place.

Therefore it is not necessary to be brought to a white heat, as it is in
the case of the production of carborundum, described elsewhere.

It was extremely interesting to observe the wonderful magnetic effects
that were produced in iron when brought into proximity with these
enormous electrical conductors. The voltage was so low that one could
handle them with impunity. The iron crucibles became so magnetic that a
heavy bar of iron seven or eight feet long would cling to their sides,
so that it would be held in an upright position. Bars of iron would
cling to the conductor at any point along its length, and, although
these conductors were carrying an energy of over 3000 horse-power, they
produced no perceptible effect upon the human body. The reason for this
lies in the fact, first, that the body is not made of magnetic material,
and, secondly, the pressure is so low that the body--being a poor
conductor--would not easily allow the low-pressure current to pass
through it.

Aluminum is fast becoming an important article of commerce, and it is
destined to become more and more so on account of its extreme lightness
as compared to other metals.

It is found to be valuable also when used as an alloy with many of the
other metals. One of the great drawbacks to its more extensive use lies
in the fact that as yet no satisfactory method has been devised for
soldering it. Undoubtedly in time this difficulty will be solved, when
its use will be greatly increased. It is estimated that in its various
compounds aluminum forms about one-twelfth of the crust of the earth.



CHAPTER XXVIII.

ELECTRICAL PRODUCTS--CALCIUM CARBIDE.


Another important use to which electricity is put at Niagara Falls is
the manufacture of a new product, called calcium carbide. Like
carborundum and aluminum, this product could not have been produced in
commercial quantities in advance of a means for producing electricity in
enormous volume.

Calcium carbide is a compound of calcium and carbon. Calcium is a white
metal not found in the natural state, but exists chiefly as a carbonate
of lime, which is ordinary limestone, including the various forms of
marble. As a pure metal it is hard to obtain and very hard to maintain,
as it readily oxidizes when in contact with the air. The symbol for
calcium carbide is CaC_{2}, which means that a molecule of this carbide
is compounded of one atom of calcium and two atoms of carbon. Ca stands
for calcium and C for carbon. When the symbol has no figure following
it, it means that one atom only enters into the compound; but if a
figure follows, it means that as many atoms enter in as the figure
represents.

The process of manufacturing calcium carbide is as follows: Ordinary
lime before it is slacked is ground to a fine powder; then it is mixed
with powdered coke or carbon in the proper quantities, so that when a
chemical union takes place the proportion will be as before stated, one
atom of calcium to two of carbon. As is well known, lime is procured by
exposing ordinary limestone to a red heat for some hours together. The
heat disengages the carbon dioxide, leaving only a combination of
calcium and oxygen, which is common lime.

The mixture of ground lime and coke is put into a crucible that
surrounds the arc of an electric light of enormous dimensions; the
carbon conductors amounting to an area of one square foot or more. In
order to cause the carbon to unite with the calcium a very intense heat
is required, such a heat as can be obtained only in the arc of an
electric light. When the enormous current is turned on (amounting to
over 3000 horse-power) the mixture is melted, and after an exposure to
this intense heat for a given length of time the oxygen of the unslacked
lime is thrown off and the carbon unites with the calcium, which remains
in the proportions of one atom of calcium to two of carbon, as before
stated. This, it will be noted, is purely a heat process, and an intense
one at that. No electrolytic action being required, the alternating
current is used without transformation to the direct current, as is
necessary in the manufacture of bleaching-powder and aluminum, both of
which are electrolytic processes.

When the operation is completed the current is turned off and the
compound allowed to cool. In cooling it assumes a slate color, which is
slightly iridescent when exposed to light. It also crystallizes to a
certain extent.

The value of this new product consists in its ability to evolve
Acetylene gas in large quantities. A molecule of acetylene gas is
composed of two atoms of carbon to two of hydrogen. To evolve the gas it
is necessary only to pour water upon the calcium carbide, when a union
takes place between the carbon of the carbide and the hydrogen of the
water in the proportions above stated. If there is water enough the
whole of the carbon will pass off with the gas, leaving a residuum of
slacked lime.

The value of acetylene gas lies in its very intense illuminating power.
This is due to the fact that the gas is very rich in carbon as compared
with other illuminating gases. It burns with a pure white light when
properly mixed with air or oxygen, but if there is a lack of air it
burns with a smoky flame. In this case the carbon is not all consumed
and escapes into the air in the form of soot or smoke, but when burned
with the proper mixture of oxygen or common air it becomes one of the
most brilliant of illuminants. Acetylene, like most other gases, becomes
explosive when mixed with air in certain proportions. Whether it is more
dangerous to handle than ordinary illuminating gases the writer is not
prepared to say, as he has not had the opportunity to make a thorough
comparison between it and other gases from an experimental standpoint.

Experiment, after all, is the only sure road to absolute knowledge.
Theories are beautiful in books and lectures, but they often fail in the
laboratory.

Acetylene is now being introduced as an illuminating gas for domestic
and other purposes. Several methods of handling it have been proposed.
One is to condense it into strong metal cylinders and deliver it in that
form; another is to erect generators at convenient places and generate
the gas as it is used. A very ingenious contrivance has been invented
for regulating the generation of the gas. A certain amount of the
calcium carbide is placed in a gas-tight vessel containing water. As
soon as the water comes in contact with the carbide the evolution of the
gas begins. When the pressure on the inside of the vessel has reached a
certain degree it is made, through mechanical contrivances, to lift the
carbide out of the water and thus stop the evolution of the gas. When
the pressure is relieved through the consumption of the gas at the
burners it allows the carbide to drop into the water, when the evolution
of the gas begins again.

Of course there is the same objection to this mode of lighting that
attends all open burners; it is constantly discharging into the air the
products of combustion, chiefly carbon dioxide, which is poisonous to
animal life. As has been explained in some of the chapters on heat, in
Volume II, the illuminating property of any gas is determined by the
number of carbon particles that are contained in it, which become heated
to incandescence as soon as they come in contact with the oxygen of the
air, and remain so, for a brief period, during their passage between the
two extremes of the flame. While acetylene equals electricity in its
illuminating properties, the latter still stands without a rival when
considered from a sanitary standpoint, as the use of electricity does
not in any degree vitiate the air in a room where it is used.

We have now given somewhat in detail the following processes that are
carried on at Niagara Falls through the agency of electricity, viz.: The
reduction of aluminum from its oxide alumina; the production of the new
and useful compound called carborundum; the formation of calcium carbide
used for the production of acetylene gas, and a large chemical works,
where bleaching-powder is made. In addition to these works, there is an
establishment for the production of sodium from caustic potash, which is
one of the products arising from the decomposition of salt in the
bleaching-powder works. There is also another establishment for the
production of phosphorus made from the bones and shells obtained from
the phosphate beds that abound in some of the southern states, on the
coast of the Atlantic Ocean. There is in process of construction a plant
for the purpose of manufacturing chlorate of potash by an electrical
process. In addition to these establishments mentioned, the electricity
is furnished for power purposes to the Niagara Electric Light Company;
to the electric railway between Niagara and Buffalo; to the Niagara
Falls Railway, on the opposite side of the river; to the Niagara Power
and Conduit Company of Buffalo, and the Niagara Development Company.
This is only a small beginning of the uses to which electricity will be
put as an agent for the development of heat, light and power as well as
for the production of all substances where electrolysis is the chief
factor. Sixteen companies or more are now using electricity from the
Niagara power-house,--the whole amounting to about 35,000 horse-power.



CHAPTER XXIX.

THE NEW ERA.


When we consider the number of new products for whose existence we are
indebted to electricity, and the number of old products that have
heretofore existed experimentally, in the laboratory of the chemist
only, that have now been brought into play as useful agents in the
various arts and industries, we begin to realize that this is truly an
electrical age and the dawning of a new era. How many, many things there
are, familiar to the children of to-day, that were not even imagined by
the children of twenty-five to fifty years ago. Fifty years ago the only
useful purpose to which electricity was put was that of transmitting
news from city to city by the Morse telegraphic code. It will be
fifty-seven years the first of April, 1901, since the first
telegraph-line was thrown open to the public. Less than thirty years ago
but little advance had been made in the use of electrical appliances
beyond the perfection of certain private-line instruments, and a means
for multiple transmission. About twenty years ago there were evidences
of the beginning of a new era in electrical development. At no time in
the history of the world has wonder succeeded wonder with such rapidity,
producing such astounding results that have revolutionized all our modes
of doing business and all of the operations of commercial and domestic
life, as during the last two decades. We set our watches by time
furnished by electricity from one central point of observation. We read
the tape from hour to hour, upon which is recorded the commercial pulse
of the world, as it throbs in the marts of trade, by means of this same
speedy messenger. We enter a street-car that is lighted and heated, and
at the same time propelled by the same wonderful agent. In our homes and
on our streets night is turned into day by a light that outrivals all
other illuminants.

When we wish to speak to a friend who may be a mile or a thousand miles
away we step to the end of a wire that comes within the walls of our
dwelling and we talk to him as though face to face, and means are at
hand by which we may write a letter to that same friend and deliver it
to him in our own handwriting and over our own signatures, so quickly
that it will appear before him in full form and completeness as soon as
the last period is made at the end of the last line.

One sees, and hears, and lives more in a single day in this age of
electricity and steam than he did in twelve months sixty years ago. And
yet there are those who cry out against modern inventions and modern
civilization, and are constantly quoting the days of their grandfathers
and great-grandfathers when "life was simple" and there was "time to
rest." "Why are we tormented with this thought-stimulating age?" they
say. "Why are our emotions called into action by modern music and modern
art? Why are we called upon to help the downtrodden and oppressed, and
to help to elevate mankind to a higher level? Why cannot we be left
alone in peace and quiet, to live in the easiest way?"

If this be good philosophy, then the swine, if he were a reasoning
being, ought to be ranked among the greatest of philosophers--when he
seeks a wallow in the sunshine and sleeps away his useless existence. If
he is useful it is because some other being of a higher order uses him
to help along his own existence. The man in these days who does not
"keep up with the procession" is soon trodden under foot and some other
man uses him as a stepping-stone to elevate himself.

Yet this is a selfish motive, after all. The world is now rapidly
advancing in light, in knowledge, in power to use the infinite gifts
that the Creator has hidden in nature; but hidden only to stimulate and
reward our seeking. Every man can help in this grand progress,--if not
by research and positive thought-power, at least by grateful acceptance
and realization of what is gained. _Look forward!_ As Emerson puts it:
"To make habitually a new estimate--that is elevation."



INDEX.


  Acetylene gas at Niagara, 230.

  Alexandria, temple with loadstone, 20.

  Amber--elektron, 6.

  Ampère, theory of magnetism, 25.
    unit of electrical current, 85.
    galvanometer, 93.

  Aluminum at Niagara, 223.

  Arabians, magnetic needle, 21.

  Arago, germ of electromagnet, 93.

  Aristotle mentions torpedo, 6.
    refers to magnet, 20.

  Atmospheric electricity, Ch. VIII, 77.

  Atoms and molecules, 39.
    of substances differ in weight, 42.
    relations to heat, 42.

  Aurora Borealis, 35.


  Bain chemical telegraph register, 101.

  Barlow on galvanism in telegraphy, 93.

  Bell, Alexander Graham, radiophone, 171.

  Bleaching-powder at Niagara, 218.

  Branly invents the coherer, 179.


  Cables, submarine. See Submarine Cables.

  Calcium-carbide at Niagara, 228.

  Capacity of a circuit, 118, 119.

  Caustic soda, 221.

  Chinese, magnetic needle, 21.

  Chlorine and sodium, 219.

  Circuit-breaker at Niagara, 199.

  Closed circuit and current, 122.

  Coherer (wireless telegraphy), 179.

  Columbus, compass variations, 22, 34.

  Condenser in resistance-coil, 118.
    in Morse relays, 131.

  Conductors and non-conductors of electricity, 47.
    relation to electric light, 50.
    different resistances, 74, 83.

  Cooke, needle telegraph, 108.

  Crookes, Prof., X-ray, 121.

  Cuneus and the Leyden jar, 8.

  Curiosities, Ch. XX, 171.


  Daniell battery, 85.

  Differential magnet, 115.

  Dinocares and the loadstone, 20.

  Dolbear, Amos E., wireless telegraphy, 178.

  Dupay discovers positive and negative electricity, 8.

  Duplex telegraphy, 114.

  Dynamo-electric machines, 67.
    invented by Faraday, 14, 69.
    usual construction, 70.
    at Niagara, 192.

  Double transmission, 115.


  Earth electric currents, in telegraphy, 99, 116, 182.

  Earth magnetism, 32.
    effects of, on iron, 35.
            Aurora, 35.
            telegraph-lines, 36.
    from sun's heat, 75.

  Edison, Thomas, railway telegraphy, 131.
    electromotograph, 175.

  Electric currents, Ch. VI, 49.
    not currents but atomic motion, 54.
    induction of, 56.
        guarded against, 169.
    at Niagara, 193.

  Electric generators, Ch. VII, 62.
    frictional, 49.
    galvanic batteries, 62.
    storage-batteries, 64.
    dynamos, 67, 192.
    metal heating, 74.

  Electricity, science of, 6.
    achievements of, 16.
    eras in science of, 18.
    theory of, Ch. V, 39.
    not a fluid, a form of energy, 40.
    static and dynamic, 46.
    measurement of, Ch. IX, 83.

  Electric light, cause of, 50.

  Electric machines, 49.
    frictional, 51.
    galvanic or chemical, 51.
    mechanical, 70.

  Electromagnet invented by Faraday, 14.
    commercial value, 23.
    theory of (soft iron), 26.
    permanent (steel), 28.
    condition of use, 30.
    the earth a, 32.
    germ of, 93.
    differential, 115.

  Electromotograph, 175.

  Ellsworth, Miss, sends first telegraphic message, 96.

  Ether, lines of force, 31.
    nature of, 40.

  Ether, impressed by atomic motion, 56.
    inducing electric action, 56.


  Farad, unit of capacity, 118.

  Faraday, Michael, 14.

  Farmer, Moses G., double transmission, 114.

  Field, Cyrus W., lays first Atlantic cable, 156.

  Field of a magnet, 31.

  Fitzgerald, Niagara Falls chemist, 210.

  Franklin catches the lightning, 8.
    identity of lightning and electricity, 10.
    kite experiment, 11.
    electric firing-telegraph, 88.

  Frode, history of Iceland, 21.


  Gadenhalen uses magnetic needle 868 A.D., 21.

  Galileo's seed-thought, 89.

  Galvani, Luigi, and galvanism, 12.

  Galvanic batteries, 62.
    author's experience, 65.

  Galvanometer, 75, 93.

  Gilbert, Dr., frictional electricity, 7.

  Gintl, double transmission, 114.

  Gray, Elisha, constructs voltaic pile, 65.
    electrically transmits music, 91.
    experiments on transmission of music, articulate speech,
            and multiple messages, 123.
    files telephone caveat, 135.
    musical experiments, 136.
    speech receivers, 139.
    boys' telephone, 141.
    first telephone specification on record, 143.
    dial-telegraph, 161.
    automatic-printing telegraph, 163.
    telautograph, 165.
    electric musical receiver, 175.

  Gray, Stephen, electrician, 8.

  Grier, John A., quoted, 67.

  Guyot of Provence mentions mariner's compass, 21.


  Halske, double transmission, 114.

  Harmonic telegraphy, 120.
    receivers, 125.
    relay, 130.

  Hawksbee, Francis, electrician, 7.

  Heat, a mode of motion, 40.
    related to atoms, 42.
    begins and ends in matter, 44.
    electrical and mechanical energy the same, 46.

  Henry, Joseph, first practical telegrapher, 90.
    constructs long-distance line, 94.
    produces induction, 177.

  Heraclea and the loadstone, 20.

  Hertz experiments in ether-waves, 178.

  Homer refers to loadstone, 20.

  Horse-power, 214.

  House, Royal E., printing telegraph, 108, 110.

  Hughes, David E., printing telegraph, 108, 112.


  Induction, 56.
    guarded against, 169.
    produced by Henry, 177.


  Keeper of a magnet, 31.

  Kelvin, Lord (Sir W. Thompson), cable message receiver, 158.

  "Kick," in telegraphy, 115, 118.

  Kleist and the Leyden jar, 8.


  "Let her buzz," 3.

  Leyden jar invented, 8.

  Lightning, electricity; Franklin, 8.
    restoration of equilibrium, 78.

  Lightning-rods, 80.
    dangerous conductors, 81.

  Loadstone, 20, 21.


  Maury, Lieut., deep-sea soundings, 155.

  Magnes, Magnesia, 20.

  Magnet, electro. See Electromagnet.

  Magnetic earth poles, 23, 32.

  Magnetic lines of force, 31, 34, 60.

  Magnetic needle, 21.
    variation of, 22.
    dip of, 22.
    action of, 33.

  Magnetism, history of, 20.
    and electricity mutually dependent, 24.
    theories of, 24.
    in iron and steel, 25.
    in the earth, 32, 36.
    and sun-spots, 37.

  Magnetization, limit of, 31.

  Marconi, wireless telegraphy, 178-180.

  Measurement of electricity, 83.
    ampère, unit of, 85.
    method of, 86.

  Mercury luminous by shaking, 7.

  Micro-farad, unit of capacity, 119.

  Molecules of iron and steel natural magnets, 25.
    and atoms, 39.

  Morse, S. F. B., devises code of telegraphic signals, 95.
    induces Congress to construct line, 96.
    transmits battery current through water, 177.

  Motion universal, 38.
    causes sound, heat, light, and electricity, 39.

  Multiple transmission, Ch. XIII, 114.
    duplex, 116.
    quadruplex, 118.

  Multiple transmission, musical, 120.

  Musical message receivers, 125, 139.

  Musical tones transmitted, 91, 92, 120, 136.

  Muschenbroeck, Prof., and the Leyden jar, 8.

  Newton, Sir Isaac, electrician, 8.


  Niagara Falls Power, Chs. XXII to XXVIII, 186 to 233.
    Introduction--rock, water, power, 186.
    Appliances:
      tunnel, power-house, 190.
      shaft, dynamos, 192.
      current, 193.
      governor, 194.
      water-head, 195.
      crane, 196.
      circuit-breaker, 199.
      transformer, 200.
      electromotive force, 204.
    Electrical Products--Carborundum, 209.
      materials, 210.
      furnaces, 211.
      electric current, 213.
      horse-power, 214.
      method of work, 215.
    Bleaching-powder, 218.
      chlorine and sodium, 219.
      method of work, 220.
      caustic soda, 221.
    Aluminum, 223.
      crucibles and methods, 224.
      magnetic effects, 226.
    Calcium carbide, 228.
      process, 229.
      acetylene gas, 230.
    Other products, 232.

  Oersted, galvanic current on magnetic needle, 93.

  Ohm, G. S., resistance unit, 74.


  Patents--Caveat and application, 135.

  Planté, storage-battery plates, 64.

  Pliny mentions electrical properties of amber, 67.
    loadstone, 20.

  Preece, double transmission, 114.

  Prescott, Geo. B., quoted, 104, 106, 163, 174.

  Ptolemy Philadelphus and loadstones, 20.

  Pythagoras refers to natural magnets, 20.


  Radiophone, 171.

  Railway train telegraphy, 131.

  Richman, Prof., killed, 12.

  Reiss, metallic telephone transmitters, 122.

  Resistance, unit of, 74.
    -coil, 118.


  Siemens, double transmission, 114.

  Selenium in radiophone, 172.

  Shephard, Charles S., induction-coil, 122.

  Stager, Gen. Anson, telegrapher, 110.

  Stearns, Joseph B., cures the "kick" in double transmission, 115.

  Storage-battery, 24.

  Strada, loadstone telegraph, 88.

  Submarine cables, Ch. XVII, 154.
    first lines, 154-5.
    Maury's deep-sea soundings, 155.
    first Atlantic, 156.
    retardations, 157.
    receiver, 158.

  Sun-spots and magnetic storms, 37.


  Telautograph, Ch. XIX, 165.

  Telegraph:
    heliostat, 68.
    semaphore, 68.
    loadstone, 88.
    Franklin's electric firing, 88.
    electrically dropped balls, 88.
    electric transmission of musical tones, 91.
      of signals, 94.
    Morse register, 95.
    first line, 97.
    description, 98.
    reading by various senses, 100.
    Bain, chemical recorder, 101.
    Cooke needle, 108.
    Wheatstone needle, 108.
    House printing, 108, 110.
    Hughes printing, 108, 112.
    automatic systems, 109, 112.
    multiple transmission, 114.
    musical transmission, 120.
    musical receivers, 125.
    Way duplex, 129.
    from moving railway trains, 131.
    repeater, 150.
    short-line dials, 159.
    printing, 163.
    wireless, Ch. XXI, 176.

  Telegraphic messages, receiving, 103.

  Telephone, Chs. XV, XVI, 134, 145.
    author's first experiment, 91.
    experiments, 123.
    caveat, 135.
    speech receivers, 139.
    boys' telephone, 141.
    first specification of, on record, 143.
    how telephone talks, 145.
    simple construction, 146.
    two methods of transmission: magneto and varied
            resistance, 142, 149.
    limit of transmission, 153.
    central station, 164.
    affected by heat-lightning, 183.

  Telephote, 173.

  Thales of Miletus first described electrical properties of amber, 6.

  Theophrastus mentions amber, 6.

  Thermo-electric pile, 75.

  Torpedo, the, 6.

  Transformers at Niagara, 200.

  Transmission, multiple, Ch. XIII, 114.

  Trowbridge, Prof., telephones through the earth, 188.

  Tunnel at Niagara, 190.

  Tyndall, and Gray's experiments, 92.


  Unrest of the universe, 38.


  Volt, unit of electrical pressure, 85.

  Volta, Alessandro, and the voltaic pile, 13.


  Watt, James, 86.
    unit of electrical power, 86.

  Way duplex system, Ch. XIV, 129.

  Wheatstone transmits musical tones mechanically, 92.
    needle telegraph, 108.
    dial-telegraph, 159.

  Wireless telegraphy, Ch. XXI, 176.
    signaling by ether-waves, 176.
    Morse and Henry, 177.
    Trowbridge, Dolbear, Hertz, 178.
    Branly, Marconi, 179.
    Marconi's system, 180.
    by earth-currents, 182.

  Wolimer, King of Goths, a natural battery, 7.





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