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