John Lord.

Beacon Lights of History, Volume 14 The New Era; A Supplementary Volume, by Recent Writers, as Set Forth in the Preface and Table of Contents online

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conducting circuit on the axis of the disc, and the other end on its
circumference, he succeeded in drawing off a continuous electric current
generated from magnetism, and thus produced the first dynamo. This was
in 1831. Faraday produced many other dynamos besides this simple
disc machine.

Although the disc dynamo in its original form was impracticable as a
commercial machine, yet it was not only the forerunner of the dynamo,
but was, in point of fact, the first machine ever produced that is
entitled to be called a dynamo. He generously left to those who might
come after him the opportunity to avail themselves of his wonderful
discovery. "I have rather, however," he says, "been desirous of
discovering new facts and new relations dependent on magneto-electric
induction than of exalting the force of those already obtained, being
assured that the latter would find their development hereafter." How
profoundly prophetic! Could the illustrious investigator see the
hundreds of thousands of dynamos that are to-day in all parts of the
world engaged in converting millions of horse-power of mechanical energy
into electric energy, he would appreciate how marvellously his
successors have "exalted the force" of some of the effects he had so
ably shown the world how to obtain.

Faraday lived to see his infant dynamo, the first of its kind, developed
into a machine not only sufficiently powerful to maintain electric arc
lights, but also into a form sufficiently practicable to be continuously
engaged in producing such light, in one of the lighthouses on the
English coast. Holmes produced such a machine in 1862, or some years
before Faraday's death. It was installed under the care of the Trinity
House, at the Dungeness Lighthouse, in June, 1862, and continued in use
for about ten years. When this machine was shown to Faraday by its
inventor, the veteran philosopher remarked, "I gave you a baby, and you
bring me a giant."

The alternating-current transformer is another gift of Faraday to the
commercial world. As is well known, this instrument is a device for
raising or lowering electric pressure. The name is derived from the fact
that the instrument is capable of taking in at one pressure the electric
energy supplied to it, and giving it out at another pressure, thus
transforming it. Faraday produced the first transformer during his
investigations on voltaic-current induction. The modern
alternating-current transformer, though differing markedly in minor
details from Faraday's primitive instrument, yet in general details is
essentially identical with it. The enormous use of both step-up and
step-down transformers - transformers which respectively induce currents
of higher and of lower electromotive forces in their secondary coils
than are passed through their primaries - shows the great practical value
of this invention. The wonderful growth of the commercial applications
of alternating currents during the past few decades would have been
impossible without the use of the alternating-current transformer.

It is an interesting fact that it was not in the form of the step-down
alternating-current transformer that Faraday's discovery of
voltaic-current induction was first utilized, but in the form of a
step-up transformer, or what was then ordinarily called an induction
coil. As early as 1842, Masson and Bréguet constructed an induction
coil by means of which minute sparks could be obtained from the
secondary, in vacuo. In 1851, Ruhmkorff constructed an induction coil so
greatly improved, by the careful insulation of its secondary circuit,
that he could obtain from it torrents of long sparks in ordinary air.
The Ruhmkorff induction coil has in late years been greatly improved
both by Tesla and Elihu Thomson, who, separately and independently of
each other, have produced excellent forms of high-frequency
induction coils.

Induction coils have long been in use for purposes of research, and in
later years have been employed in the production both of the Röntgen
rays used in the photography of the invisible, and the electro-magnetic
waves used in wireless telegraphy.

Röntgen's discovery was published in 1895. It was rendered possible by
the prior work of Geissler and Crookes on the luminous phenomena
produced by the passage of electric discharges through high vacua in
glass tubes. Röntgen discovered that the invisible rays, or radiation,
emitted from certain parts of a high-vacuum tube, when high-tension
discharges from induction coils were passing, possessed the curious
property of traversing certain opaque substances as readily as light
does glass or water. He also discovered that these rays were capable of
exciting fluorescence in some substances, - that is, of causing them to
emit light and become luminous, - and that these rays, like the rays of
light, were capable of affecting a photographic plate. From these
properties two curious possibilities arose; namely, to see through
opaque bodies, and to photograph the invisible. Röntgen called these
rays X, or unknown rays. They are now almost invariably called by the
name of their distinguished discoverer.

Let us briefly investigate how it is possible both to see and to
photograph the invisible. Shortly after Röntgen's discovery, Edison,
with that wonderful power of finding practical applications for nearly
all discoveries, had invented the fluoroscope, - a screen covered with a
peculiar chemical substance that becomes luminous when exposed to the
Röntgen rays. Suppose, now, between the rays and such a screen be
interposed a substance opaque to ordinary light, as, for example, the
human hand. The tissues of the hand, such as the flesh and the blood,
permit the rays to readily pass through them, but the bones are opaque
to the rays, and, therefore, oppose their passage; consequently, the
screen; instead of being uniformly illumined, will show shadows of the
bones, so that, to an eye examining the screen, it will seem as though
it were looking through the flesh and blood directly at the bones. In a
similar manner, if a photographic plate be employed instead of the
screen, a distinct photographic picture will be obtained.

Both the fluoroscope and the photographic camera have proved an
invaluable aid to the surgeon, who can now look directly through the
human body and examine its internal organs, and so be able to locate
such foreign bodies as bullets and needles in its various parts, or make
correct diagnoses of fractures or dislocations of the bones, or even
examine the action of such organs as the liver and heart.

About 1886, Hertz discovered that if a small Leyden jar is discharged
through a short and simple circuit, provided with a spark-gap of
suitable length, a series of electro-magnetic waves are set up, which,
moving through space in all directions, are capable of exciting in a
similar circuit effects that can be readily recognized, although the two
circuits are at fairly considerable distances apart. Here we have a
simple basic experiment in wireless telegraphy, which, briefly
considered, consists of means whereby oscillations or waves, set up in
free space by means of disruptive discharges, are caused to traverse
space and produce various effects in suitably constructed receptive
devices that are operated by the waves as they impinge on them.

At first a doubt was expressed by eminent scientific men as to the
practicability of successfully transmitting wireless messages through
long distances, since these waves, travelling in all directions, would
soon become too attenuated to produce intelligible signals; but when it
was shown, from theoretical considerations, that these waves when
traversing great distances are practically confined to the space between
the earth's surface and the upper rarified strata of the atmosphere, the
possibility of long-distance wireless telegraphic transmission was
recognized. To increase the distance, it was only necessary either to
increase the energy of the waves at the transmitting station, or to
increase the delicacy of the receiving instruments, or both.

It has been but a short time since both the scientific and the financial
worlds were astounded by the actual transmission of intelligible
wireless signals across the Atlantic, and the name of Marconi will go
down to posterity as the one who first accomplished this great feat.

The principal limit to the distance of transmission lies in the delicacy
of the receiving instruments. The most sensitive are those in which a
telephone receiver forms a part of the receiving apparatus. The almost
incredibly small amount of electric energy required to produce
intelligible speech in an ordinary Bell telephone receiver nearly passes
belief. The work done in lifting such an instrument from its hook to the
ear of the listener, would, if converted into electric energy, be
sufficient to maintain an audible sound in a telephone for 240,000
years! Even extremely attenuated waves may therefore produce audible
signals in such a receiver.

The electric motor was another gift of Faraday to commercial science,
although in this case there are others who can, perhaps, justly claim to
share the honor with him. Faraday's early electric motor consisted
essentially in a device whereby a movable conductor, suspended so as to
be capable of rotation around a magnet pole, was caused to rotate by the
mutual interaction of the magnetic fields of the active conductor and
the magnet. The magnet, which consisted of a bar of hardened steel, was
fixed in a cork stopper, which completely closed the end of an upright
glass tube. A small quantity of mercury was placed in the lower end of
the tube, so as to form a liquid contact for the lower end of a movable
wire, suspended so as to be capable of rotating at its lower extremity
about the axis of the tube. On the passage of an electric current
through the wire, a continuous rotary motion was produced in it, the
direction of which depends both on the direction of the current, and on
the polarity of the end of the magnet around which the rotation occurs.

The great value of the electric motor to the world is too evident to
need any proof. The number of purposes for which electric motors are now
employed is so great that the actual number of motors in daily use is
almost incredible, and every year sees this number rapidly increasing.

The above are the more important machines or devices that have been
directly derived from Faraday's great investigation as to the production
of electricity from magnetism. Let us now inquire briefly as to what
useful processes or industries have been rendered possible by the
existence of these machines.

Apparently one of the most marked requirements of our twentieth-century
civilization is that man shall be readily able to extend the day far
into the night. He can no longer go to sleep when the sun sets, and keep
abreast with his competitors. Of all artificial illuminants yet
employed, the arc and the incandescent electric lights are
unquestionably the best, whether from a sanitary, aesthetic, or truest
economical standpoint. Now, while it is a well-known matter of record
that both arc and incandescent lights were invented long before
Faraday's time, yet it was not until a source of electricity was
invented, superior both in economy and convenience to the voltaic
battery, that either of these lights became commercial possibilities.
Such an electric source was given to the world by Faraday through his
invention of the dynamo-electric machine, and it was not until this
machine was sufficiently developed and improved that commercial electric
lighting became possible. The energy of burning coal, through the
steam-engine, working the dynamo, is far cheaper and more efficient for
producing electricity than the consumption of metals through the
voltaic pile.

It is characteristic of the modesty of Faraday that when, in
after-life, he heard inventors speaking of their electric lights, he
refrained from claiming the electric light as his own, although, without
the machine he taught the world how to construct, commercial lighting
would have been an impossibility.

The marvellous activity in the electric arts and sciences, which
followed as a natural result of Faraday giving to the world in the
dynamo-electric machine a cheap electric source, naturally leads to the
inquiry as to whether at a somewhat later day a yet greater revolution
may not follow the production of a still cheaper electric source. In
point of fact such a discovery is by no means an impossibility. When a
dynamo-electric machine is caused to produce an electric current by the
intervention of a steam-engine, the transformation of energy which takes
place from the energy of the coal to electric energy is an extremely
wasteful one. Could some practical method be discovered by means of
which the burning of coal liberates electric energy, instead of heat
energy, an electric source would be discovered that would far exceed in
economy the best dynamo in existence. With such a discovery what the
results would be no one can say; this much is certain, that it would,
among other things, relegate the steam-engine to the scrap-heap, and
solve the problem of aerial navigation.

What is justly regarded as one of the greatest achievements of modern
times is the electrical transmission of power over comparatively great
distances. At some cheap source of energy, say, at a waterfall, a
water-wheel is employed to drive a dynamo or generator, thus converting
mechanical energy into electrical energy. This electricity is passed
over a conducting line to a distant station, where it is either directly
utilized for the purpose of lighting, heating, chemical decomposition,
etc., or indirectly utilized for the purpose of obtaining mechanical
power for driving machinery, by passing it through an electric motor.
The electric transmission of power has been successfully made in
California over a distance of some 220 miles, at a pressure on
transmission lines of 50,000 volts.

The high pressures required for the economical use of transmission lines
necessitates the employment of transformers at each end of the line;
namely, step-up transformers at the transmitting end, to raise the
voltage delivered by the generators, and step-down transformers, at the
receiving end, to lower it for use in the various translating devices.
These transformers are employed in connection with alternating-current
dynamos. Faraday not only gave to the world the first electric
generator, but also the first transformer, and one of the first electric
motors, and without these gifts the electric transmission of power over
long distances, which has justly been regarded as one of the most
marvellous achievements of our age, would have been an impossibility.

In high-tension circuits over which such pressures as 50,000 volts is
transmitted, no little difficulty is experienced from leakage and
consequent loss of energy. This leakage occurs both between the line
conductors and at the insulators placed on the pole lines forming the
line circuit. The insulators are made either of glass or porcelain, and
are of a peculiar form known as triple petticoat pattern. The loss on
such lines, due to leakage between wires, is greater than that which
takes place at the pole insulators, and is diminished by keeping the
circuit wires as far apart as possible.

In the early history of the art, electric transmission of power was
effected by means of direct-current generators and motors, - generators
and motors through which the current always passed in the same
direction. Such generators and motors, however, possessed inconveniences
that prevented extensive commercial transmission of power, since, as we
have seen, high pressure was necessary for efficiency in such
transmission, and the collecting-brushes and commutators employed in all
direct-current generators and motors to carry the current from the
machine or to the motor, were a constant source of trouble and danger.

When the alternating-current motor first same into general use, it was
employed, in connection with the alternating-current generator, in
electric transmission systems; but such motors also possess the
inconvenience of not readily starting from a state of rest, with their
full turning power, or torque, and of therefore being unsuitable where
the motor requires to be frequently stopped or started. Had these
difficulties remained unsolved, long-distance electric transmission of
power, so successful in operation to-day, and which bids fair to be
still more successful in the near future, would have been impossible.
Fortunately, these difficulties were overcome by the genius of Nikola
Tesla, in the invention of the multiphase alternating-current motor, or
the induction motor, as it is now generally called. Although Baily,
Deprez, and Ferraris had accomplished much before Tesla's time, yet it
was practically to the investigations and discoveries made by Tesla,
between 1887 and 1891, that the induction motor of to-day is due.

Another requirement of our twentieth-century civilization is rapid
transit, either urban or inter-urban, and this is afforded by various
systems of electric street railways or electric traction generally,
including electric locomotives and electric automobiles. The wonderful
growth in this direction which has been witnessed in the last few
decades would have been impossible without the electric generator and
motor, both gifts of Faraday to the world. Their application in this
direction must, therefore, go to swell the debt our civilization owes to
the labors of this great investigator.

In the system of electric street-car propulsion very generally employed
to-day, a single trolley wheel is employed for taking the driving
current from an overhead conductor, suspended above the street. The
trolley wheel is supported by a trolley pole, and is maintained in good
electric contact with the trolley wire, or overhead conductor. By this
means the current passes from the wire down the conductor connected with
the trolley pole, thence through the motors placed below the body of the
car, and from them, through the track or ground-return, back to the
power station. A small portion of the current is employed for lighting
the electric lamps in the car. In some systems an underground trolley
is employed.

An important device, called the series-parallel controller, is employed
in all systems of electric street-car propulsion. It consists of means
by which the starting and stopping of the car, and changes, both in its
speed and direction, are placed under the control of the motorman. A
separate controller is placed on both platforms of the car. The
series-parallel controller consists essentially of a switch by means of
which the several motors, that are employed in all street cars, can
be variously connected with each other, or with different electric
resistances, or can be successively cut out or introduced into the
circuit, so that the speed of the car can be regulated at will, as the
handle of the controller is moved by the motorman to the various notches
on the top of the controller box. As generally arranged, the speed
increases from the first notch or starting position to the last notch,
movements in the opposite direction changing connections in the opposite
order of succession, and, therefore, slowing the car. There is, however,
no definite speed corresponding to each notch, for this will vary with
the load on each car, and with the gradient upon which it may
be running.

But there is another valuable gift received by the world as a result of
this great discovery of Faraday; namely, that most marvellous instrument
of modern times, the speaking telephone. This instrument was invented in
1861, by Philip Ries, and subsequently independently reinvented in 1876,
by Elisha Gray and Alexander Graham Bell.

As is well known, it is electric currents and not sound-waves that are
transmitted over a telephone circuit. The magneto-electric telephone in
its simplest form consists of a pair of instruments called respectively
the transmitter and the receiver. We talk into the transmitter and
listen at the receiver. Both transmitter and receiver consist of a
permanent magnet of hardened steel around one end of which is placed a
coil of insulated wire. In front of this coil a diaphragm, or thin
plate, of soft iron, is so supported as to be capable of freely
vibrating towards and from the magnet pole.

The operation of the transmitting instrument is readily understood in
the light of Faraday's discovery. It is simply a dynamo-electric machine
driven by the voice of the speaker. As the sound-waves from the
speaker's voice strike against the diaphragm, which has become magnetic
from its nearness to the magnet pole, electric currents are generated in
the coil of wire surrounding such pole, since the to-and-fro motions
cause the lines of electro-magnetic force to pass through the wire on
the moving coil. The operation of the receiving instrument is also
readily understood. It acts as an electric motor driven by the
to-and-fro currents generated by the transmitter. As these currents are
transmitted over the wire, they pass through the coil of wire on the
receiving instrument, and reproduce therein the exact movements of the
transmitting diaphragm, since, as they strengthen or weaken the
magnetism of the pole, they cause similar motions in the diaphragm
placed before it. Consequently, one listening at the receiving diaphragm
will hear all that is uttered into the transmitting diaphragm. It was
thus, by the combination of the dynamo and motor, both of which were
given by Faraday to the world, that we have received this priceless
instrument, which has been so potent in its effects on the civilization
of the Twentieth century.

The electric telegraph had its beginnings long before Faraday's time. As
early as 1847, Watson had erected a line some two miles in length,
extending over the housetops in London, and operated it by means of
discharges from an ordinary frictional electric machine. In 1774, Lesage
had erected in Geneva an electric telegraph consisting of a number of
metallic wires, one for each letter of the alphabet. These wires were
carefully insulated from each other. When a message was to be sent over
this early telegraphic line an electric discharge was passed through the
particular wire representing the letter of the alphabet to be sent; this
discharge, reaching the other end, caused a pithball to be repelled and
thus laboriously, letter by letter, the message was transmitted. How
ludicrously cumbersome was such an instrument when contrasted with the
Morse electro-magnetic telegraph of to-day, which requires but a single
wire; or with the harmonic telegraph of Gray, which permits the
simultaneous transmission of eight or more separate messages over a
single wire; or with the wonderful quadruplex telegraphic system of
Edison which permits the simultaneous transmission of four separate and
distinct messages over a single wire, two in one direction, and two in
the opposite direction at the same time; or with the still more
wonderful multiplex telegraph of Delaney, which is able to
simultaneously transmit as many as seventy-two separate messages over a
single wire, thirty-six in one direction and thirty-six in the opposite
direction. These achievements have been possible only through the
researches and discoveries of Oersted, Faraday, and hosts of other
eminent workers; for, it was the electro-magnet, rendered possible by
Oersted, together with the magnificent discoveries of Faraday, and
others since his time, that these marvellous advances in
electro-telegraphic transmission of intelligence have become
possibilities.

Before completing this brief sketch of some of the effects that
Faraday's work has had on the practical arts and sciences, let us
briefly examine the generating plants that are either in operation or
construction at Niagara Falls.

Some idea of the size of the Niagara Falls generating plant on the
American side may be gained from the fact that there have already been
installed eleven of the separate 5,000 horse-power generators. The
remaining capacity of the tunnel will permit of the installation of
50,000 additional horse-power, or 105,000 horse-power in all.

On the Canadian side of the Falls another great plant is about to be
erected with an ultimate capacity of several hundred thousand
horse-power. Here, however, the size of the generating unit will be
double that on the American side, or 10,000 horse-power. These
generators will be wound to produce an electric pressure of 12,000


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Online LibraryJohn LordBeacon Lights of History, Volume 14 The New Era; A Supplementary Volume, by Recent Writers, as Set Forth in the Preface and Table of Contents → online text (page 23 of 26)