And now comes one of the most remarkable episodes in the history of
electricity,—a chapter of mingled shame and glory. In the village of
Eberly’s Mills, Cumberland County, Pa., lived a genius by the name of
Daniel Drawbaugh, who had made a study of telephony up to the very
point Bourseul had left it. He had transmitted musical sound, sound of
the voice, and other sounds in the same pitch. He had said that this
was all that could be done till some means was discovered of holding
up the constant onward flow of the electric current along a conducting
wire by introducing into such flow a variable resistance such as would
impart to simple pitch of voice the quality or _timbre_ of human
speech. Drawbaugh achieved this in his simple workshop as early as
1859–60, according to evidence furnished to the United States Supreme
Court at the celebrated trial of the cases which robbed him of the
right to his prior invention. He did it by introducing into the circuit
a small quantity of powdered charcoal confined in a tumbler, through
which the current was passing. The charcoal, being a poor conductor and
in small grains, offered just that kind of variable resistance to the
current necessary to reproduce the tones and syllables of speech. He
transmitted speech between his shop and house, and proved the success
he had met with before audiences in New York and Philadelphia. But he
neglected to care for the commercial side of his discovery, though many
of his patents antedated those which contributed to deprive him of
deserved honor and profit.
In 1861, Reis, of Germany, came into notice as the inventor of a
telephone which transmitted sound very clearly, but failed to reproduce
syllabified speech. However, the principle and shape of his transmitter
and receiver were accepted by those who followed him. Two men now
came upon the scene who had reached the conclusion already arrived at
by Drawbaugh, and who became rivals over his head for the honor and
profit of an invention by means of which the quality of the voice in
speaking could be transmitted. These two were Elisha Gray, of Chicago,
and Alexander Graham Bell, of Boston. Their respective devices seem
to have been akin, and to have been presented to the patent office
almost simultaneously; so nearly so, at least, as to make them a part
of that long, costly, and acrimonious legal contention over priority of
invention which did not end till 1887.
Both Bell and Gray reached the conclusion that the transmission of
articulate speech was impossible unless they could produce electrical
undulations corresponding exactly with the vibrations of the air
or sound waves. They brought this similarity about by introducing
a variable resistance into the electric current by means of an
interposing liquid, just as Drawbaugh had done years before with
his tumbler of powdered charcoal. Bell exhibited his instrument
with comparative success at the Centennial Exhibition in 1876 in
Philadelphia; but much had yet to be done to perfect a telephone of
real commercial value.
The years 1877–78 were years of great activity among electricians,
whose prime object was to perfect a telephone transmitter and receiver,
by means of whose mutual operations at opposite ends of a circuit all
the modulations of speech could be preserved and passed. To this end
Berliner introduced into a transmitter or sender the then well-known
principle of the microphone (Gr. _mikros_, small, _phone_, sound),
which magnified the faint sounds by the variation in electrical
resistance, caused by variation of pressure at loose contact between
two metal points or electrodes. Edison quickly followed with a
similar transmitter or sender, in which one of the electrodes was of
soft carbon, the other of metal. Then came (1878) Hughes and Blake
with senders, in which both of the electrodes were of hard carbon.
Subsequently came other and rapid modifications of the sender, both in
the United States and Europe, till the form of telephone now in popular
use was arrived at, and which, strange to say, is, in its method of
securing the necessary variable resistance in the circuit, quite like
that employed by Mr. Drawbaugh; to wit, the introduction of fine carbon
granules into a small metal cup just behind the vibrating diaphragm
or disk of the sender. The circuit goes into the diaphragm in front,
passing through the carbon granules and out through the back of the
instrument. The action of talking into the sender causes the granules
to be agitated, thus opening and closing the circuit and producing
the conditions necessary to the transmission of articulate speech.
The diaphragm or disk is the very thin covering of the cup containing
the granules. It is sometimes made of carbon, but generally of hard
metal, as steel. On being struck by the sound waves of the voice, it
vibrates to correspond. The same vibrations are reproduced in the
receiver at the opposite end of the circuit, and thus one listens to
the phenomenon of transmitted human speech. The current for telephonic
purposes is furnished by one or more batteries or cells, whose effect
is heightened by the presence of an induction coil. The tendency now
is to make “bipolars”—two contacts at the diaphragm—in place of a
single contact. This style is becoming more in vogue in order to meet
the demands of long-distance work. To each telephone is attached a
generator or device for ringing a little bell as a signal that some one
wishes to communicate. To such perfection have telephones been brought
that it is quite possible to converse intelligibly at the distance
of a thousand miles, with a less satisfactory service at twice or
thrice that distance. The possibilities of clear speech-transmission
at indefinite distance are without measure. Like the telegraph, the
telephone has opened an immense and profitable industry, involving
hundreds of millions of dollars. At the end of the century it is,
unfortunately, monopolistic; but the time is near when a reasonable
charge for service will enable every business house to communicate with
its customers, and when even the remote corners of counties will be
brought into touch with their capitals and with one another. Along the
lines of civilizing contact the telephone fairly divides the wonders
of the century with the telegraph, while for intimate intellectual
communication it is a triumph of genius without parallel. It is the
dispenser of speech in city, town, and village; in factory and mine,
in army and navy; throughout government departments; and in Budapest,
Hungary, it is a purveyor of general news, like the newspaper, for the
“Telephone Gazette” of that city has a list of regular subscribers,
to whom it transmits, at private houses, clubs, cafes, restaurants,
and public buildings, its editorials, telegrams, local news, and
advertisements.
A very natural outgrowth of the telephone was that curious invention
known as the phonograph (Gr. _phone_, sound, and _graphein_, to write).
It is not only an instrument for writing or preserving sound, but for
reproducing it. As a simple recorder of sound, it was an instrument
dating as far back as 1807, when Dr. Young showed how a tuning-fork
might be made to trace a record of its own vibrations. But Young’s
thought had to go through more than half a century of slow evolution
before the modern phonograph was reached; for in the phonautograph
of Scott, the logographs of Barlow and Blake, and the various other
attempts up to 1877 to make and preserve tracings of speech, there were
no successful means of reproducing speech from those tracings hit upon.
[Illustration: A GRAPHOPHONE.]
In that year (1877), Edison, in striving to make a self-recording
telephone by connecting with its diaphragm or disk a stylus or metal
point which would record its vibrations upon a strip of tinfoil,
accidentally reversed the motion of the tinfoil so that the tracings
upon it affected the stylus or tracing-point in an opposite direction.
To his surprise, he found that this reverse motion of the tinfoil,
tickling, as it were, the stylus oppositely, reproduced the sounds
which had at first agitated the diaphragm. It was but a step now to
the production of his matured phonograph in 1878. He made a cylinder
with a grooved surface, over which he spread tinfoil. A stylus or fine
metal point was made to rest upon the tinfoil, so as to produce a
tracing in it, following the grooves in the cylinder when the latter
was made to revolve. This stylus was connected with the diaphragm of an
ordinary telephone transmitter. When one spoke into the transmitter,
that is, set the diaphragm to vibrating, the stylus impressed the
vibratory motions of the diaphragm, or, in other words, the waves
of the exciting sound, in light indentations upon the tinfoil. In
order to reproduce the sounds thus registered in the tinfoil of the
cylinder, it was made to revolve in an opposite direction under the
point of the stylus, and as the stylus was now affected by precisely
the same indentations it had first made in the tinfoil, it carried
the identical vibrations it had recorded back to the diaphragm of the
telephone, and thus reproduced in audible form the speech that had
at first set the diaphragm to vibrating. The speech thus reproduced
was that of the original speaker in pitch and quality. Ingenious and
wonderful as Edison’s machine was, it was susceptible of improvement,
and soon Bell and others came forward with a phonograph in which the
recording cylinder was covered with a hardened wax. This was called
the graphophone. Again, Berliner improved upon the phonograph by using
for his tracing surface a horizontal disk of zinc covered with wax.
By chemical treatment, the tracings made in the wax were etched into
the zinc, and thus made permanent. Edison made further and ingenious
improvements upon his phonograph by attaching hearing tubes for the
ear to the sound receiver, and by the employment of an electric motor
to revolve the wax cylinder. By the attachment of enlarged trumpets
and other devices, every form of modern phonograph has been rendered
capable of reproducing in great perfection the various sounds of
speech, song, and instrument, and has become a most interesting source
of entertainment.
V. DYNAMO AND MOTOR.
Dynamo is from the Greek _dunamis_, meaning power. Motor is from the
Latin _motus_, or _moveo_, to move. Dynamo is the every-day term
applied to the dynamo-electric machine. Motor is the every-day term
applied to the electric motor. The dynamo and motor are quite alike
in principle of construction, yet direct opposites in object and
effect. Perhaps it might be well to designate both as dynamo-electric
machines, and to say that, when such machine is used for the conversion
of mechanical energy or power of any kind into electrical energy or
power, it is a dynamo. When a reverse result is sought, that is, when
electrical energy or power is to be converted into mechanical energy or
power, the machine that is used is a motor. In practical use for most
purposes they are brought into coöperation, the dynamo being at one
end of an electric system, making and sending forth electricity, the
motor being at the other end, taking up such electricity and running
machinery with it. Both machines were epoch-making in the midst of a
wondrous century, and both were results of those marvelous evolutions
in electrical science which characterized the earlier years of the
century.
We have seen how the simple glass cylinder or sulphur roll became, when
rubbed, a generator of electricity. In a later chapter of electrical
history, we saw a new and more powerful generator of electricity in
the voltaic cell, by means of opposing metals acted upon chemically
by acids. The greatest, grandest, most powerful, and most economic
of all generators of electricity was yet to come in the shape of the
dynamo. We see its beginnings in those investigations of Faraday which
led to the discovery of the induction coil and the principles of
magneto-electric induction. In 1831, he invented a simple yet, for that
date, wonderful machine, which was none the less the first dynamo in
principle, because he modestly called it “A New Electrical Machine.” He
mounted a thin disk of copper, about twelve inches in diameter, upon a
central axis, so that it would revolve between the opposite poles of a
permanent magnet. As the disk revolved, its lower half cut the field
of force of the magnet, and a current was induced which was carried
away by means of two collecting brushes, fastened respectively to the
axis and circumference of the disk. This was the first electric current
ever produced by a permanent magnet. The Faraday machine and others
that derived the mechanical energy which was converted into electric
current from a permanent magnet were classed as magneto-generators.
Soon the electro-magnet took the place of the permanent magnet,
because it produced a much stronger field of force. But then the
electro-magnet had to have a current to excite it. This current was
supplied by a magneto-generator, placed somewhere on the dynamo. Now
came the thought, suggested by Brett in 1848, that the induced currents
of the dynamo could themselves be turned to account for increasing
the strength of the electro-magnets used in inducing them. This was a
most progressive step in the history of the dynamo. It led to rapid
inventions, whose principle was based on the fact that every dynamo
carried within the cores of its magnets enough of unused or residual
magnetism to render the magnets self-exciting the moment the machine
started. So the outside means of magnetizing the fields of force of the
dynamo passed away.
The dynamo speedily grew in size and importance. The electro-magnets
or fields of force were greatly increased in number, size, and power.
There were great improvements in the construction and efficiency
of the wire coils or armatures which cut the fields of force, and
a corresponding increase in their number. Commutators and brushes
underwent like improvement. So, at last, the well-nigh perfect and
all-powerful dynamo of the end of the century was evolved, with a
capacity for delivering, in the form of electricity, ninety per cent
of the mechanical energy which set it in motion. In the application of
steam to machinery, eighty per cent, and sometimes more, of the energy
supplied by a ton of coal is lost.
[Illustration: A DYNAMO.]
With the perfection of the dynamo, its uses multiplied. It became a
prime factor in electric lighting. Trolley systems sprang up in city,
town, and village, taking the place of horse and traction cars. In
certain places, as in the Baltimore tunnel, the dynamo superseded the
engine for hauling freight and passenger cars. The mighty dynamos which
convert the inexhaustible energy of Niagara Falls into electricity
send it many miles away to Buffalo, to be applied to lighting and to
every form of machinery. The end of the century sees a power plant in
operation in New York city capable of furnishing one hundred thousand
horse-power, or enough to supply the lighting, rapid transit, and
thousand and one mechanical needs of the entire municipality. The
essential parts of an ordinary dynamo are: (1.) The electro-magnets,
which, however numerous, are arranged in circular form upon part of
the framework of the machine. (2.) The iron coils or armatures, mounted
in a circle upon a wheel. When the wheel revolves, the armatures pass
close in front of the electro-magnets, cutting through their fields
of force, and thereby inducing electric current. (3.) The commutator,
which consists usually of a series of copper blocks arranged around the
axle of the armatures, and insulated from the axle and from each other.
The current passes from the armatures to the commutator. If the current
be an alternating one, the commutator changes it into a continuous one,
and the reverse may also be accomplished. (4.) The brushes, which are
thin strips of copper or carbon, are brought to bear at proper points
upon the commutator, making connection with each coil or sets of coils.
They carry the corrected current to the outside line or lines. (5.) The
outside line or lines, to carry the current away to the motor. (6.) The
pulley for strap-belting, by means of which the water or steam power
used is made to turn the dynamo machine.
But we must not forget the motor as a companion of the dynamo, as its
indispensable brother, in turning to practical account the electricity
sent to it. As we have seen, the motor is the reverse of the dynamo, at
least in its effects. It is fed by the dynamo, and it imparts its power
to the machinery which it is to set in motion. It is to the dynamo
what the water-wheel is to the water. In one sense it is an even older
invention than the dynamo, but its extended commercial application was
not possible until the dynamo had reached certain stages of perfection.
It is generally agreed that the first motor of importance was that
constructed by Professor Jacobi, through the liberality of the Czar
Nicholas, of Russia. Jacobi used two sets of electro-magnets, by
means of whose mutual attraction and repulsion he rotated a wheel on
a boat with a power equal to that of eight oarsmen. But as Jacobi’s
electro-magnets required an electric current to magnetize them, and as
there were then no means of producing such current except by the costly
use of the voltaic battery, his invention was unripe as to time.
In 1850, Professor Page, of the Smithsonian Institution, constructed
a motor which worked ingeniously, but was still open to the
objection of cost in supplying the necessary electric current for
the electro-magnets. Though various inventions came about having
for their object a commercially successful motor, such a thing was
impossible till Gramme produced his improved and effective dynamo
in 1871. This dynamo was found to work equally well as a motor, and
hence it became necessary for electricians to greatly enlarge their
understanding of the nature of electro-magnetic induction. They soon
discovered many curious things respecting the behavior of induced
currents, with the result that rapid and simultaneous improvements
were made in both dynamos and motors. One of the most curious of these
discoveries was that a motor automatically regulates the amount of
current that passes through its circuit in proportion to the work it
is called upon to do; that is, if the work the machine has to do is
decreased, the motor attains a higher speed, which higher speed induces
a counter electro-motive force sufficient to check up the amount of
current passing through the motor. So when the motor is required to do
increased work, the machine slows up; but with this slowing up, the
counter electro-motive force decreases, and consequently the current
passing through the motor increases.
As with the dynamo, one of the marvels of the motor is its efficiency.
In perfect machines, ninety to ninety-five per cent of the electrical
energy supplied can be converted into mechanical energy. For this
reason it has become a competitor with, and even successor of, steam
in countless cases, and especially where water-power can be commanded.
A prime motor, in the shape of a water-wheel, may be made to drive
scores of secondary motors in places hundreds of miles away. The power
developed by the waterfall at Lauffen, Germany, is transmitted one
hundred miles to Frankfort, with a loss of only twenty-five per cent of
the original horse-power.
[Illustration: THE GOLDEN CANDLESTICK.]
In its adaptation for practical use, the motor, like the dynamo,
assumes all sizes and embraces a host of ingenious devices, yet its
power and usefulness always centre around, or are contained in, its two
efficient parts, its armatures and fields of force. We have seen how
in the dynamo the armatures became the source of induced currents by
being made to cut the fields of force of electro-magnets. Now, a dynamo
can be made to work in an opposite way; that is, by making the magnetic
fields of force rotate in front of the coils or armatures. In the
motor, the field of force is mostly established by the current directly
from the dynamo. This current passes also through the armature, which
begins to rotate, owing to the force of the field upon it. This
rotation of the armature through the field of force produces in the
armature conductors an electro-motive force, which is the measure of
the power of the motor, be the same great or small.
VI. “AND THERE WAS LIGHT.”
[Illustration: ANCIENT LAMP.]
Mention of the “candlestick of pure gold” (Ex. xxv. 31) may lead to the
inference that the primitive artificial light was that of the candle.
But “candlestick” in connection with the lighting of the temple is
clearly a misnomer. The lamp was the original artificial light-giver,
unless we choose to except the torch; and if less indispensable than
in patriarchal times, it is still a favorite dispenser of nightly
cheer. Prior to the middle of the eighteenth century, the lamp had
practically no evolution. It was the same in principle at that date as
when it illuminated the desert tabernacle. Even the splendid enameled
glass or decorated Persian pottery lamps of Damascus and Cairo, and the
magnificent brass or bronze lamps of Greece, Rome, and the European
cathedrals, gave forth their dull, unsteady flame and noisome smoke
by means of a crude wick lying in a saucer or similar receptacle of
melted lard, tallow, oil, or some such combustible liquid. A prime
improvement was made in lamp-lighting in 1783, by Leger, of Paris, who
devised the flat, metallic burner, through which he passed a neatly
prepared wick. A further improvement was made in 1784 by Argand, of
Paris, who introduced a burner consisting of two circular tubes,
between which passed a circular wick. The inner tube was perforated
so as to admit of a draught of air to feed the flame on the inside of
the wick. In order to similarly feed the flame on the outside of the
wick, he invented the lamp chimney, which was at first a crude thing of
metal. It, however, soon gave way to the glass chimney, which has up
to the present taken on many improved forms, designed to secure more
perfect combustion and a brighter, steadier glow.
[Illustration: TALLOW DIP.]
[Illustration: MODERN LAMP.]