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Title: Principles of electricity
Author: Maynard Shipley
Release date: February 25, 2025 [eBook #75464]
Language: English
Original publication: Girard: Haldeman-Julius Company, 1925
Credits: Bob Taylor, Tim Miller and the Online Distributed Proofreading Team at https://www.pgdp.net (This file was produced from images generously made available by The Internet Archive)
*** START OF THE PROJECT GUTENBERG EBOOK PRINCIPLES OF ELECTRICITY ***
Transcriber’s Note
Italic text displayed as: _italic_
LITTLE BLUE BOOK NO. 133
Edited by E. Haldeman-Julius
Principles of
Electricity
Maynard Shipley
HALDEMAN-JULIUS COMPANY
GIRARD, KANSAS
Copyright, 1925,
Haldeman-Julius Company.
PRINTED IN THE UNITED STATES OF AMERICA
PRINCIPLES OF ELECTRICITY
CONTENTS
Chapter Page
1. “What Is Electricity?” 5
2. Magnetic Phenomena 13
3. Pioneers in Electromagnetic Theory 19
4. Theories of Electricity 30
5. Modern Magnetic Theory 41
6. Proofs that Electrons Are Atoms of Electricity 44
7. The Discovery of Wireless Telegraphy 55
PRINCIPLES OF ELECTRICITY
CHAPTER 1
“WHAT IS ELECTRICITY?”
Many persons who have devoted no time to the study of physics wonder
what the force is that drives the street-car along—turning its wheels,
while at the same time furnishing incandescent lamps (light) for the
passengers. They have been told, of course, that the “power” used is
“electricity”, generated by dynamos “at the power-house”, and conveyed
to the rapidly moving car by the overhead wire.
“Electricity: yes, but what is electricity?” This is a natural and
perfectly legitimate question for a layman to ask.
Scientists and philosophers are asking the same question. But they
understand quite well that it is like asking: “What is matter?” Very
probably the average inquirer does not ask the question, “What is
electricity?” in the same spirit. We can answer one question no better
than the other, if the ultimate nature of either matter or electricity
is what the inquirer has in mind.
For matter, in the last analysis, is electricity. Yet the same person
who might ask: “What is electricity?” would not think of asking: “What
is matter?” He thinks he knows what matter is—his common sense tells
him that _matter is what it appears to be_. “Matter’s matter, and
there’s an end of it.”
And just so the physicist insists upon his common-sense right to
reply: “Electricity is electricity.” It is what it appears to him to
be. And it appears to be a form of _energy_, or a _mode of
motion_.
Thales, the reputed founder of Greek science and philosophy, would
call electricity “the soul of the universe”, because it “endows all
things with motion”. This “soul”, interpenetrating all matter—if not
constituting it—is by nature always moving—it is self-moving; motion
is part of its very essence. In the lodestone, said Thales, “it moves
iron.”[1]
As has been said so many times before, Thales was the first to call
attention to the fact that amber (fossilized resin), when rubbed
with wool or fur, possesses the curious property of attracting small
particles, such as straw, pith, lint, dried leaves, etc.;—though there
is no reason to suppose that he was the discoverer of this phenomenon.
He called the amber _elektron_; and today we call the indivisible
corpuscles, or natural unit charges of negative electricity,
_electrons_—the true _atoms_ of electricity.
But hard rubber, or sealing-wax, is just as “mysterious” as the
lodestone (magnetite—natural magnetic iron). Rub the sealing-wax with
fur, and it will exhibit all the peculiar properties of the lodestone.
Rub glass with silk, and it, too, becomes a lodestone in effect. The
ancient Greek philosophers could not explain these phenomena in precise
terms.
Empedocles (born between 500 and 480 B. C.) accounted for the
attraction of iron to the magnet on the hypothesis that “emanations”
or “effluences” from the magnet penetrate into the “symmetrical pores”
of the iron, drawing the iron itself and holding it fast. The concept
“electricity” was unknown to the Greeks. But it is possible that
Empedocles had in mind some such “effluence” or “emanation” as the
“fluid” electricity of Benjamin Franklin (1706-1790) and his successors.
The soul-force (“moving power”) of Thales—always moving and causing
movement—and the “effluences” of Empedocles have become the “field
of force” of Faraday, Sir J. J. Thomson, and Sir Oliver Lodge. The
self-moving “soul” of nature, manifest in the lodestone, or acting
on the lodestone, or on the particles said to be “attracted” by the
lodestone, is but a synonym for the lines of force of the magnetic
field of modern physics. Thales and Empedocles spoke in the language
(terminology) of their day and age. The “emanations” of Empedocles are
the “corpuscles” of Thomson—a body becoming positively electrified
by “losing some of its corpuscles”, and hence capable of drawing
negatively charged particles to itself.
Electricity and magnetism are related but not identical. A moving
magnet can induce an electric current in a wire, and an electric
current can produce magnetism in iron. The construction of telegraph
and telephone instruments depends on the fact that an electric current
can produce magnetism and that magnetism can produce an electric
current.
We know _effects_ which we call “electricity”, just as we know the
phenomena associated with living protoplasm without knowing what “life”
is. It may be that “life” and “electricity”, as well as “electricity”
and “magnetism”, are all different aspects of the same thing.
Today we say, in the words of Dr. Charles P. Steinmetz (“Relativity and
Space”, Pages 18-19):—
“The space surrounding a magnet is a magnetic field. If we electrify a
piece of sealing-wax by rubbing it, it surrounds itself by a dielectric
or electrostatic field, and bodies susceptible to electrostatic
forces—such as light pieces of paper—are attracted. The earth is
surrounded by a gravitational field, the lines of gravitational force
issuing radially from the earth. If a stone falls to the earth, it is
due to the stone’s being in the gravitational field of the earth and
being acted upon by it.”
Again:—“Suppose we have a permanent bar magnet and bring a piece of
iron near it. It is attracted, or moved; that is, a force is exerted on
it. We bring a piece of copper near the magnet, and nothing happens. We
say that the space surrounding the magnet is a _magnetic field_.
A _field_, or _field of force_, we define as ‘a condition
in space exerting a force on a body susceptible to this field’. Thus,
a piece of iron being magnetizable—that is, susceptible to a magnetic
field—will be acted upon; a piece of copper, not being magnetizable,
shows no action.... To produce a field of force requires energy, and
this energy is stored in the space we call the field. Thus we can go
further and define the field as ‘_a condition of energy storage in
space exerting a force on a body susceptible to this energy_’.”
Thales said that the “divine moving power”, the soul of nature, under
certain conditions “moves iron”, through the mysterious properties
of the lodestone. Modern science, borrowing from Aristotle the term
_energia_, substitutes for “soul of nature” the single word
_energy_. Aristotle declared that “not capacity, but energy ...
is the first principle anterior to and superior to anything else”
(_Metaphysics_ xii, 7: cf. also _Physics_ ii, 9, 6).
Modern science describes in more precise phrases what _occurs_
when a body susceptible to the influence of the magnet is brought into
proximity to a lodestone (magnetite). It gives us a picture of “lines
of force” (energy) in a defined “field”. But it tells us no more about
what energy _is_ than Thales tells us what his “moving power” is.
Dr. Steinmetz tells us that “energy is the only real existing entity,
the primary conception, which exists for us because our senses respond
to it” (_Op. cit._, Page 23). For Thales the universal “moving
power” of nature operates _on_ or _in_ all matter; for the
physicist of today the moving power (energy) is matter—man’s perception
of matter being the response of his senses to the vibrations of energy.
“All sense perceptions are exclusively energy effects,” and “energy is
the only real existing entity.”
Thales may or may not have considered the cosmos as “matter”
_and_ “soul” or “moving power”. In any event the pre-Socratic
Ionian philosophers recognized no distinction between matter and soul
in our modern sense. The moving power of nature (soul) was as much a
material substance as gross matter itself, only more rarefied, more
elusive. It was equivalent to the “energy”—electricity—of modern
science.
Here we have, then, the answer to the question: “What is electricity?”
It is _energy_—“the only real existing entity, the primary
conception, which exists for us because our senses respond to it.” “All
sense perceptions are exclusively energy effects.” This is the answer
to the question: “What are the Hertzian waves, used in ‘wireless’?” It
is the answer also to the question: “What is light?” as well as “What
is electricity?” By carrying the explanation of the beam of light
and the electromagnetic wave (like that of the radio communication
station or that surrounding a power transmission line) back to the
_energy_ field (or, less accurately, the field of force), we have
carried it back, as Dr. Steinmetz well declared, as far as possible,
“to the fundamental or primary conceptions of the human mind, the
perceptions of the senses.”
All that we know of the world is derived from the _perceptions of our
senses_, which are for us the only _real facts_, all things
else being conclusions from them; and “all sense perceptions are
exclusively _energy_ effects.” Electricity is an energy effect,
perceived by our senses. No other definition or explanation can or need
be given, since _energy is the primary conception_. And this
explains also what matter is, since _energy_ and _matter_ are
interchangeable—or equivalent—terms. What we call electricity is one
of the _effects of energy_ on our senses. In itself, it _is_
energy, the stuff that matter is made of; at once the “moving power”
and the thing moved.
Everything has been said that can be said now as to what electricity
_is_: our concern in the remainder of this volume will be to
discover what electricity _does_ and how it acts.
* * * * *
The reader of this little book who may be more or less familiar
with larger volumes dealing with electricity, energy, electrons,
electromagnetic waves or oscillations, magnetic and dielectric fields
(usually combined), light-waves, etc., will notice that no mention
has been made of the classical ether hypothesis, the universal
_plenum_ in which energy is said to be stored, and in which
transverse waves of light are said to occur, ether atoms or vibrations
moving at right angles (perpendicularly) to the light-beam.
Now, transverse waves can exist only in rigid (solid) bodies. The
universal ether of space, referred to in the text-books, must—for
reasons which I need not discuss here—be a solid body of a rigidity
much greater than that of steel, while at the same time possessing
a very great elasticity so that bodies (such as the planets) moving
through it meet with no resistance, no friction. The electron theory of
Lorentz, Larmor, Thomson, Lodge and others is based upon the assumption
that such a _plenum_, or medium, is a real substance. As a matter
of fact, it is not known that any such medium (or ether) does exist,
and it is now recognized that while light is a _wave_, a periodic
phenomenon, like an alternating current, it is not necessarily a
wave _motion_ of something or in something, any more than it is
necessary to assume the alternating current or voltage wave to be a
motion of matter.
Electrical engineers make no assumption regarding the existence of an
ether filling all space and interpenetrating all matter—have no need
for an ether as the hypothetical carrier of the electric wave. And just
so the physicist of today has no real need for the classical assumption
that the light-wave is a wave motion of or in something of great
rigidity yet highly elastic and frictionless, filling all space. Light
is now known to be a high-frequency electromagnetic wave, and cannot
logically be considered as a wave motion of a hypothetical ether. “The
ether thus vanishes, following the phlogistin and other antiquated
conceptions.”[2] As Prof. A. S. Eddington remarks in his “Report on
the Relativity Theory of Gravitation” (1920), “Light does not cause
electromagnetic oscillations; it _is_ the oscillations.”
We know nothing whatever about the so-called ether of space; but we can
formulate very clearly “The Principles of Electricity” without the aid
of that hypothesis.[3]
FOOTNOTES:
[1] If a light piece of iron is placed near a magnet, it moves to the
magnet and clings to it; but if the magnet is the lighter of the two
bodies, it moves toward the piece of iron.
[2] Steinmetz, Dr. Charles P., “Four Lectures on Relativity and Space,”
Pages 21-22, London and New York, 1923. See Lecture II, “Conclusions
from the Relativity Theory,” Pages 12-45. See also, Campbell, Dr.
Norman R., “Modern Electrical Theory. Supplementary Chapters:
Relativity,” Cambridge University Press, 1923.
CHAPTER 2
MAGNETIC PHENOMENA
It was long ago observed that if glass is rubbed by silk, or a piece of
sealing-wax or hard rubber by fur or wool, an effect occurs similar to
that noted by Thales when amber is rubbed by similar materials—i. e.,
light bodies such as bits of dry paper, pith, etc., will cling to the
surface of the substance. After coming in contact with the attracting
substance, the bits of paper, straw, etc., are then repelled.
If a ball made of pith be suspended at the end of a silk thread, and
a glass rod which has just been rubbed with silk be brought close to
the ball, the pith-ball immediately flies to the rod, clinging to it
for a time. Then it jumps away, and instead of hanging vertically,
seems to be pushed away from the glass by a mysterious force. A second
ball, treated like the first, and brought near the first, is violently
repelled. But if one ball is charged from the glass and one from the
wax, they attract instead of repelling each other. Two pieces of glass
or two pieces of wax repel each other.
A similar attraction and repulsion was early observed between the poles
of the magnet. This influence seems to be transmitted by some invisible
agency or medium across the intervening space between the bodies, and
in this respect the force does not differ from that acting between the
moon and the earth, or the earth and the sun. And just so, if a light
piece of iron is placed near a magnet, it moves to the magnet and
clings to it; but if the magnet is the lighter of the two bodies, it
moves toward the piece of iron.
Although Thales had attempted to explain the cause or nature of
magnetic attraction as long ago as the end of the seventh century B.
C., or in the first quarter of the sixth century (about 2,500 years
ago), it was not until the year 1582 A. D. that Dr. William Gilbert
(1540-1603), of Colchester, physician to Queen Elizabeth, made the
first experimental study of magnetic phenomena. It is to Dr. Gilbert
that we owe the name _electricity_ as applied to this force,
derived from his _vis electrica_.
By 1600, Dr. Gilbert had published his epochal work “_De
Magnete_”, which not only contained the first rational treatment
of magnetic and electrical phenomena, but was also virtually the
first scientific work published in England. It is to this truly
great treatise that must be traced the beginnings of the science of
electricity.[4]
Throwing aside, as useless, mere philosophical speculation as to
the nature of magnets, Gilbert explained in his book how practical
experiments should be carried out. He insisted that it is to nature
herself that we must apply for the answers to problems in “natural
history”. Gilbert’s particular objective was not, however, discovery of
the laws of magnetism or electricity; what he most desired to learn was
_the composition of the earth_: he wished to know through actual
research just what is its innermost constitution. His experiments
led him to the conclusion that _the earth is a magnet_. It may,
indeed, be considered a huge spheroidal lodestone.
Gilbert told his readers to take a piece of lodestone (natural magnetic
iron) of convenient size, turn it on a lathe to the form of a ball,
then place on the _terella_ (as he called the spherical lodestone)
a piece of iron wire. It will then be observed that the ends of the
wire “move round its middle point.”[5]
Lodestones, fragments of magnetite (Fe_{3}O_{4}), are said to have
been first discovered at Magnesia, in Asia Minor,—hence the word
_magnetism_. Some of the earliest references to the lodestone
relate to its property of lying in a north-and-south direction when an
elongate stone is freely suspended, one particular end always pointing
northward, just as the great magnet the earth, or the mariner’s
compass-needle, has two opposite magnetic poles. The location of the
poles of a disk-shaped stone is readily found by turning it round in
the presence of a compass-needle.[6]
Iron and steel are more strongly magnetic than any other metals. While
only one kind of iron ore is naturally magnetic—forming magnets—the
property of magnetism may always be given to any kind of iron or steel.
One need only strike an iron bar while it is lying in a north-south
position, or rub the iron with a magnet, and it becomes a magnet. If it
is desired to make a _permanent_ magnet, steel must be employed. A
compass-needle is therefore made of magnetized steel. If balanced upon
a pivot, the positive pole of the needle will point (roughly) towards
the earth’s north geographical pole.[7]
A compass-needle is also a “dipping needle”, unless the suspended
magnetized needle lies about half way between the earth’s magnetic
poles. The north magnetic pole lies below the earth’s surface—at an
unknown depth—at the extreme northeastern corner of the continent of
North America; and the corresponding south magnetic pole on the edge of
the Antarctic continent—King George’s Land—about 2,300 miles south of
Australia. These magnetic poles do not correspond even roughly with the
geographic poles, nor does the magnetic equator by any means correspond
with the geographic equator.
Only a small section of the magnetic equator runs north of the true
(geographic) equator—e. g., from the coast of Brazil to the coast of
Kamerun (Africa).
According to Prof. T. J. J. See, “the whole magnetic system has been
pushed southward 200 miles by bodily displacement of both poles towards
the ocean hemisphere.” This eminent physicist-astronomer also stated
(in 1922) that his researches led him to the discovery that the two
magnetic poles are at unequal depths in the earth, the North Pole
being much deeper than the South Pole, “with the result that the total
magnetic forces in the southern hemisphere are considerably stronger
than in the northern hemisphere.”[8]
It was long ago discovered that if one starts northward from the
magnetic equator, the compass-needle soon begins to dip downward (and
northward). At the southern border of the United States, the downward
inclination amounts to about 57 degrees. At the borders of North
Dakota and Maine the dip is about 76 degrees. By the time Hudson Bay
is reached the needle assumes a vertical position. This means that it
is here suspended immediately over the north magnetic pole itself.
At the magnetic equator in Peru, a needle suspended by a thread is
exactly balanced. Dr. See states that at the North and South Poles
there is a downward pull—by the magnetic force—of just one millionth
of the gravitational force, while in Peru the total magnetic force is
precisely one ten millionths of gravitation.
It has been found that both the North and the South Poles are anything
but fixed in position. They “wander about in their subterranean
region”. In the course of centuries, the compass-needle swings from
west of north, and then to the east. Even the amount of the dip slowly
changes, in a periodic way, and at every point on the earth. For
example, in 1576, the north end of the needle at London dipped at an
angle of 71 degrees 50 minutes. By 1720 the angle had increased to 74
degrees 42 minutes—almost up and down. Since then, the dip at London
has continually decreased. At the present time we are puzzled by the
fact that the inclination of the dip is 66½ degrees at London and more
than 70 degrees at Washington.
It has long been known that variations in magnetic declination of the
delicately mounted needles, in observatories, are directly correlated
with solar disturbances. The late Dr. A. Wolfer (sometime director of
the Zurich Observatory) was the first to show us how closely the curve
of the sun-spot activity rises and falls with the fluctuations of
magnetic declinations.
Before attempting to explain the peculiarities of magnetic action in
terms of the modern electromagnetic theory, it will be well to recall
certain stages of progress in the development of this theory. This plan
will permit elucidation of the theory itself by “easy steps”.
FOOTNOTES:
[3] Cf. Whittaker, E. T., “A History of the Theories of the Ether and
Electricity from the Age of Descartes to the Close of the Nineteenth
Century,” Dublin and London, 1910. See also, Comstock and Troland,
“The Nature of Matter and Electricity,” New York, 1917; Steinmetz,
Dr. Charles P., “Elementary Lectures on Electric Discharges, Waves
and Impulses and Other Transients,” New York, 1914; and Starling, Dr.
Sydney G., “Electricity,” London and New York, 1922.
[4] On the Continent, experimental work in other fields was already
in progress, thanks to the genius of Descartes, Galileo and other
founders of modern science. Gilbert, like Harvey, spent some years
in Italy, coming under the direct influence of the great Italian
physicist-astronomer-physician Galileo. Harvey was in Padua (1598-1602)
during Galileo’s professoriate. The introduction of scientific methods
in England at this time may well be credited to Italian and French
influences.
[5] Gilbert’s book is usually referred to simply as “The Magnet,”
but the full title is: “Concerning the Magnet and Magnetic Bodies,
and Concerning the Great Magnet the Earth: A New Natural History
(Physiologia) Demonstrated by Many Arguments and Experiments.”
[6] Magnetite does not always possess polarity. It is called
“lodestone” only when it does. It occurs not only in the form of more
or less massive stones, but also as loose sand and in earthy forms.
[7] The fact that a lodestone possesses two “poles” was discovered in
the thirteenth century by Petrus Peregrinus, of Picardy, while he was
experimenting with a spherical lodestone and a needle.
[8] From notes taken at a lecture by Dr. See before the California
Academy of Sciences in 1922. Dr. See, in charge of the United States
Naval Observatory at Mare Island (California), presented in the
lecture “A New Theory of the Ether,” in which he outlined the grounds
upon which he based his new theory of a direct connection between
magnetism and universal gravitation. It is highly interesting, in
this connection, to learn that Dr. Albert Einstein, in collaboration
with Professor Eddington (of Cambridge)—working on the principle of
Relativity—has discovered a connection between the earth’s power of
attraction (gravitation) and electricity.
CHAPTER 3
PIONEERS IN ELECTROMAGNETIC THEORY
The Danish physicist, Hans Christian Örsted, professor of natural
philosophy at the University of Copenhagen, showed us, more than a
century ago, that a magnetic needle can be deflected by an electric
current. He had been led by theoretical considerations to assume that
there must be a correlation between electric and magnetic forces. While
yet a young man, Örsted endeavored by persevering experimentation to
prove the correctness of his theory. While he did not expect a parallel
action of the two forces, he was firmly convinced that magnetism and
electricity were inseparable twins.
He noted that both heat and light radiated from a conductor when heated
to incandescence. He also assumed that magnetic forces are radiated
from a conductor traversed by electricity.
In 1820, while lecturing before his class, he became convinced that
the apparatus he was then using could be made to demonstrate the
correctness of his views. He asked his pupils to accompany him to his
laboratory, where, as he predicted, a slight deflection of the magnetic
needle, turned at right angles to the electric current, was shown
when placed close to the copper wire. Some months afterwards, with
a stronger current (made up of twenty cells), he obtained much more
intense effects. Investigating these in detail, he found that they met
all the requirements of his theory. So, on July 21, 1820, he sent out
to the scientific world his now famous circular, “_Experimenta circa
effectum conflictus electrici in acum magneticum_” (Experiments on
the effect of the electrical conflict in the magnetic needle).
Örsted showed, furthermore, how changes in the position of the magnetic
needle occurred with variation of the position of the conductor
(copper wire) in regard to it. He demonstrated also that the magnetic
effect was not weakened by insulators—that it would penetrate various
materials, whether these were conductors of electric currents or not.
He showed that the magnetic field created by the electric current does
not have any influence on a needle of non-magnetic material—i. e.,
brass, glass, etc. It is, in fact, chiefly in the fact that it cannot
be insulated that magnetism differs from electricity. It will freely
pass through air, stone, mica, glass, clay, brick, or any insulating
material.
It is well worthy of especial mention that Örsted employed the term
“_conflictus_” to designate the electric current, many decades
before the origin of the electron theory of matter. For, on modern
theories of electricity, it is the movement to and fro of electric
particles (electrons) through the conductor, and their impact
(“_conflictus_”) that produces what we call electrical phenomena.
Örsted’s fundamental discovery of the mutual effects between
electricity and magnetism led to further discoveries which made
possible the construction of telegraph and telephone instruments,
since these depend on the fact that _an electric current can produce
magnetism, and that magnetism can produce an electric current_.
If we wind around an iron bar a number of turns of insulated wire,
and an electric current is allowed to pass through the coil, the bar
becomes a strong electromagnet. But it remains a magnet only as long
as the current is passing. Now, the magnetic effects obtained with
the electromagnet are identical with those obtained from a permanent
magnet—such as the familiar horseshoe magnet, commonly seen on the
flywheel of the Ford automobile, or in the ordinary telephone generator
for calling up “Central”. In the case of a telegraph instrument, it is
important that the iron is a temporary magnet. On the other hand, a
permanent magnet is an essential part of every Bell telephone receiver.
This permanency is secured by employing a bar of steel instead of a
piece of iron—a temporary magnet.
The power produced from a dynamo—or electric generator—depends
upon the fact that when a magnet is put into a coil of wire, only
a momentary current of electricity passes through the wire, in one
direction. If the magnet is withdrawn, a current starts in the opposite
direction. Copper wire coiled about an iron core forms the “armature”
of the dynamo. The rotating coils are said to “cut the magnetic
field.” On this principle of electricity, intense electric currents
are produced, furnishing the “power” for the electric motors in
electric cars, elevators, musical instruments, etc., and for electric
lights—incandescent and arc.
Dynamos may contain either permanent magnets or electromagnets. They
produce the magnetic field in which the “armature” or conductor—the
coils of wire wound around the iron core—rotates. A machine with
permanent magnets is usually termed a _magneto_, and is never
made in large sizes. The current for the electromagnets may be
derived wholly from an outside source, or part of the current which
it generates may be used for that purpose. The current generated in
the armature winding is alternating, but may be rectified to a direct
current by a _commuter_ if desired; otherwise it is conveyed to
the line circuit by _collector_ or slip rings and brushes.
We owe much of our knowledge of magnetism and electricity to Michael
Faraday (1791-1867), who brilliantly covered the whole field of these
sciences. Faraday was distinguished alike as a chemist and as an
experimenter in electricity and magnetism.
Örsted had shown that magnetism could be produced by a current of
electricity, but it remained for Faraday to produce current electricity
by a magnetic “field of force”, thus laying the foundation for those
modern industries which derived motive force for their machinery from
the gigantic dynamos of our “power houses”.
But I must here introduce a few facts concerning the contributions
to electric theory and practice of the great French mathematician
and physicist, André Marie Ampère (1775-1836). His discoveries in
electrodynamics aided greatly in laying a broad foundation for this
science. Very notable was the influence exercised by Ampère on the
development of electrodynamics. And it was he who first clearly
established the fact that magnetic action is a peculiar form of
electromotive action, and that, in phenomena of this class, “action and
reaction are equal and opposite.”
From these considerations it was natural for him to suppose that
magnetism might be made to produce electricity, as it had already been
shown that electricity might be made to imitate all the effects of
magnetism. Numerous attempts were made to effect this predicted result,
but for some years all such efforts proved to be fruitless.
Meanwhile the French physicist and astronomer, François Arago
(1785-1853), was also conducting experiments with the object of
producing electricity by magnetism. One of his experiments actually
involved the effect sought, but it was not clearly recognized. Arago
observed that the rapid revolution of a conducting plate in the
neighborhood of a magnet gave rise to a force acting on the magnet. But
it was not recognized by either Arago or other physicists of the day
that the forces involved were electric currents—produced by the rapidly
revolving conducting plate.
Faraday, in 1831, after several years of preoccupation with other
problems, returned to his task of discovering electrodynamical
induction, begun in 1825. After a number of fruitless efforts, he was
finally rewarded with success, but not in the form which had been
anticipated. It was observed that at the precise time of making or
breaking the contact which closed the galvanic circuit, a momentary
effect was induced in a neighboring wire, which, however, disappeared
instantly.[9]
Faraday then discovered that a similar effect could be induced
merely by moving the wire nearer to or farther away from the closed
circuit—instead of suddenly making or breaking the contact of the
“inducing circuit”. Later he found that the effects were increased by
the proximity of soft iron, and that when the soft iron was affected by
an ordinary magnet instead of the voltaic wire, the same effect still
recurred. The momentary electric current was produced either by moving
the magnet or by moving the wire with reference to the magnet. Finally,
it was found that the earth itself might be substituted for a magnet,
not only in this experiment but also in others. Mere motion of a wire,
under proper conditions, produced the effect.
Here, then, was the true explanation of Arago’s experiment: by the
rapid revolution of the plate the momentary effect became continuous.
Without using the magnet, a revolving plate became an electrical
machine. A revolving globe was found to exhibit electromagnetic action,
the circuit being complete in the globe itself without the addition of
any wire. It was later found by Faraday that mere motion of the wire of
a galvanometer produced an electrodynamic effect upon the needle.[10]
Meanwhile, Ampère, “by a combination of mathematical skill and
experimental ingenuity, first proved that two electric currents act
on one another, and then analyzed this action into the resultant of a
system of push-and-pull forces between the elementary parts of these
currents.”[11]
Örsted having shown that electric currents produced certain effects on
magnets without being in actual contact, and Ampère having demonstrated
that magnets can in their turn be supplemented by electric currents,—a
magnetic needle being deflected not only by a current passing through a
wire, but also by another magnet brought into its neighborhood, and two
electric currents acting on one another at a distance—the question now
arose as to whether or not electrical attraction and repulsion could be
reduced to an action at a distance proportional to the inverse square
of the distance.
As early as 1773, Henry Cavendish (1731-1810)—one of the foremost
chemists and experimentalists of his day—answered this question
affirmatively by experiment.[12] Coulomb (1736-1806)—inventor of the
torsion balance—showed that ponderable matter charged with electricity
followed the same formula for attraction and repulsion as gravitating
bodies did. Poisson (1781-1840) worked out the difficult mathematics of
fluids actuated by repelling forces depending on the inverse square of
the distance. Laplace (1749-1827) had very early become convinced that
the actions of ponderable substances in which electric currents were
flowing could be reduced to an action at a distance proportional to the
inverse square of the elements of the electric current.
Faraday regarded the electric field as full of lines of electric force,
in a state of tension, and naturally repelling each other. To him, as
to a number of his contemporaries, the idea of “action at a distance”
was repugnant; though such a possibility seemed to be indicated by the
action of gravitation—the relation of the forces between two charged
bodies to the distance between them being very similar to that of the
gravitational forces between two bodies to the distance between them.
But Faraday, like the great Descartes long before him, rejected the
theory of action at a distance in favor of “action through a medium.”
Ampère had sought for some sort of mechanism for the transmission of
electromagnetic currents. His own discoveries and those of Örsted
led him to formulate the hypothesis that the field in the vicinity
of a magnetic body is produced by a number of exceedingly small
circular currents which flow undamped in or around the molecules
and that magnetization consists merely of the bringing of these
molecular currents into a parallel direction. But it was difficult for
some physicists, even in Ampère’s day, to accept the hypothesis of
undiminished currents _possessing no resistance_.
If we transform the idea of the “molecular currents” of Ampère into
the language of today, substituting for these molecular currents
electrons revolving in atoms, it can be shown that the great French
scientist was substantially correct in his assumptions. In 1915 Dr.
Albert Einstein and W. J. de Haas astonished the world of physicists by
showing experimentally—by means of a most ingenious apparatus—that the
“molecular currents” or revolving electrons really exist.
In 1919, Professor Kramerlingh-Onnes, at the University of Leyden, was
able to produce what he called _imitations of ampere currents_—i.
e., “undiminished currents producing no resistance.” It was
demonstrated that the resistance of pure gold and pure platinum differ
very little if at all from nil at low temperatures. But wires of these
metals, of absolute purity, are difficult to obtain, so mercury was
selected for the experiments. The resistance of the metal at the lowest
attainable temperature of liquefied helium,-271.5° C., (at a pressure
of 3 mm. of the mercury column), proved to be immeasurably small. The
resistance down to a position shortly below 4.2° K. (Kelvin’s absolute
scale) suddenly dropped from a measurable amount to a value practically
nil. It was found that the induced current remained in a state of
circulation, and that the decrease in the strength of the current
amounted to less than 1 per cent per hour, from which it followed that
the “time of relaxation” must amount to more than four days![13]
At the absolute zero of temperature, it is supposed that the orbits of
electrons in atoms are perfect circles, whatever their paths may be at
measurable temperatures. This motion of the electrons remains when all
heat has disappeared, since it is not this motion of the revolution of
the electrons in their orbits that is associated with the energy of
heat. Heat is _a mode of motion of the atoms themselves_, not of
their contained electrons; though increase of heat doubtless results in
an increase in the average orbital velocity of the electrons.
Since Ampère’s day we have learned at all events, that an electric
current means the flow of electrons, either from atom to atom, or
passing between the atoms, along conductors. In 1920, Lord Kelvin came
to the conclusion that at the absolute zero resistance of metals must
be infinitely great, the degrees of dissociation of the electron being,
he supposed, nil at the zero hour. If any free electrons remained, he
believed they would lose their power of motion, condensing like a vapor
upon the metal atoms and freezing fast to them (to borrow a phrase
from Kamerlingh-Onnes). The experiments of the celebrated Holland
physicist show that the resistance of metals decreases with lowering of
temperature, and would probably become nil at the absolute zero with
employment of a perfectly pure platinum wire. If this is true, then
would a current of electricity, once set up in a conductor, continue
forever?
FOOTNOTES:
[9] _Philosophical Transactions_, Page 127, 1832; First Series,
Article 10.
[10] One of the first electrical experimenters to devise the instrument
known as a “galvanometer” was Professor Schweigger, of Halle. There are
now eight or more varieties of this instrument (or apparatus) in use.
It enables the investigator to measure extremely minute electrodynamic
actions, or the very weakest intensity of an electric current, as well
as to detect its presence or direction, usually by the deflection of a
magnetic needle.
[11] Maxwell, Clerk, “On Action at a Distance,” (_Scientific
Papers_, Vol. II, Page 317).
[12] The scientific papers of Cavendish were published (in 1879)
under the title, “The Electrical Researches of the Hon. Henry
Cavendish,” edited by Clerk Maxwell. Cavendish anticipated many later
investigations of British and Continental writers, including Ohm’s
law—i. e., the proportionality between the electromotive force and
the current in the same conductor; and anticipated also Faraday’s
discovery of the specific inductive capacity of different substances,
even measuring its numerical value in several substances. He had also
arrived at the conceptions of electrical capacity and of “potential.”
[13] See _Die Naturwissenschaften_ (Berlin), January 28, 1921.
CHAPTER 4
THEORIES OF ELECTRICITY
The science of electricity is based upon observation of those phenomena
of attraction and repulsion which are comprehended under the term
_electrostatics_. Statical electricity, so named from a Greek
word (statikos), which means “causing to stand (or stay),”—also called
_frictional electricity_—is the electricity of stationary charges
caused by rubbing together unlike bodies, such as glass and silk (noted
in Chapter II). In such cases equal and opposite charges of electricity
are always produced. The term _statical electricity_ applies
properly, however, to the electricity of all stationary charges,
however produced.
The electricity upon the surface of glass is called positive
electricity; that upon rubber, negative electricity. When silk is
rubbed upon glass it receives a negative charge from the glass and
confers a positive charge upon the silk. Wool or fur rubbed on wax or
rubber receives a positive charge in exchange for a negative charge;
“equal and opposite charges of electricity are always produced.” A
piece of glass and a piece of silk attract one another; two pieces of
silk or two pieces of glass or wax repel one another, because a body
which is positively charged is attracted by one negatively charged
and repelled by one negatively charged, and vice versa. A piece of
glass rubbed by a piece of silk, under suitable conditions, attracts
any other body with which it has not been in contact. The piece of
silk will do likewise. In all these cases, the attraction or repulsion
becomes weaker with increase of distance between the attracting and
repelling bodies.
A third body which has been in contact with a piece of glass or a piece
of silk acquires to some extent the properties of the glass or silk
with which the third body has been in contact. And, conversely, the
glass or silk with which the third body has been in contact attracts
or repels with less force than before. If a hand is drawn over the
surface of an object after it has been charged with electricity, the
electricity disappears. It has been conducted through the hand and
the body to the earth. This phenomenon shows that the human body is
a _conductor_ of electricity. But most metals are much better
conductors. Moist air and damp wood are rather poor conductors, while
dry air, dry wood, porcelain, glass, hard rubber and sealing-wax are
_non-conductors_, or _insulators_.
The term _dielectric_ is used in preference to _insulation_
when reference is made to the property of transmitting
_induction_—a process quite distinct from ordinary transmission
of an electric current. In _electrostatic induction_, a body
electrostatically charged induces in a neighboring conductor a like
charge in the parts farthest from the charged body, and an unlike
charge in the nearer parts; the repelled like charge being removed by
connecting any part of the conductor momentarily with the earth, while
the bound unlike charge spreads over the whole surface of the conductor
and remains there even when the inducing body is moved away, or its
charge neutralized, if the conductor is properly insulated.
_Dielectric strength_ refers to the ability of an insulating
material to resist rupture by high voltage, measured by the voltage
necessary to effect a disruptive discharge through it. _Insulation
resistance_, on the other hand, refers to the _ohmic_
resistance _offered_ by an insulating material to an impressed
voltage, tending to induce a breakage of current through it. The term
_dielectric_ is used as a synonym for _insulator_, in the
sense that a charge on one part of a non-conductor is not communicated
to any other part. A charge given to a conductor spreads to all parts
of the body. A dielectric possesses the property of transmitting
electric force by _in_duction but not by _con_duction. A
charge on one part of a non-conductor or dielectric is not communicated
to any other part.
Jeans suggests that since the presence of magnetic energy is always
associated with charges in motion, whereas electrostatic energy is
present when all the charges are at rest relatively to each other, it
may be proper to identify electrostatic energy with potential energy,
and magnetic energy with kinetic energy[14]—i. e., energy due to motion
of particles, rather than to energy of position, as of a coiled spring.
Statical energy is distinguished from “current electricity” by the
fact that it accumulates on various bodies—is stored up—and as soon
as proper connections are made, it discharges instantly. Statical
electricity is used by physicians in electrical treatment of diseases
and in X-ray work. Machines have been constructed that will produce
very strong charges of statical electricity.
If a sufficiently large charge of electricity accumulates upon an
insulated conductor in an electrical machine, it finally discharges
itself, passing through the air to the nearest body. A flash of
lightning is the result of an overcharge of statical electricity
accumulated upon cloud particles, and may pass from cloud to cloud
or descend to the earth.[15] Careful drivers of gasoline-tank wagons
allow an iron or steel chain to drag on the roadway from a metallic
connection, which conducts any surplus “static” to the ground. Failure
to provide for such an emergency sometimes results in a terrific
explosion with consequent loss of life.
About the beginning of the nineteenth century, the Italian scientist,
Alessandro Volta (1745-1827),—and other physicists—discovered what
has been called, after Volta, _voltaic electricity_, a current
generated by chemical action between metals and different liquids as
arranged in a voltaic battery. The term “volt”—the electromotive force
which performs work at the rate of one joule per second (one watt) in
producing a current of one ampere—was similarly derived.
It was learned that if two different metals, such as copper and
zinc amalgam, are placed in a weak acid solution (such as one part
H_{2}SO_{4} to four parts H_{2}O), and connected by a wire fastened
securely to the metals, a current of electricity (about two volts) will
pass through the wire. Carbon (a non-metal) and a metal upon which the
solution acts chemically may be used instead of two metals. There must
be chemical action between the liquid and one metal, or there will be
no current. Such a combination constitutes a _cell_, and two or
more cells make a _battery_. The current starts with the zinc,
is conducted by the solution to the copper, and thence by wire back
to the zinc, completing a _circuit_. The zinc constitutes the
negative pole (or electrode), the copper or carbon the positive pole
(or electrode).
A cell frequently employed, where a weak (about 1.1 volts) but constant
electromotive force (“E. M. F.”) is required, is one devised by the
English physicist, John D. Daniell (1790-1845). In this cell a copper
sulphate solution containing a copper electrode is placed in contact
(by means of a porous wall or partition—usually an unglazed porcelain
cup) with a zinc sulphate solution containing a zinc electrode. The
zinc electrode is negative to the copper. At each electrode there
exists a potential difference between solution and electrode.[16] The
two electrodes being connected externally by a wire, a current of
electricity will flow through the wire from the copper to the zinc, and
zinc will dissolve at the anode (positive pole) and copper deposited
on the cathode (negative pole). The current in this case, as in the
preceding, is said to be produced by _voltaic action_ and the
cell is a primary battery. Voltaic action and _electrolysis_—the
process of chemical decomposition (or dissociation of compounds or
molecules)—by the action of an electric current produced externally (as
by a dynamo) and forced through the cell, are essentially identical
phenomena, and obey the same laws.[17]
The familiar _dry cell_ contains no liquid which might be spilled,
and is very useful for certain purposes, as in automobiles, and in
operating door-bells. It is merely a voltaic cell whose chemical
contents are made practically solid (or paste-like) by the use of some
absorbent, as gelatine, sawdust, etc. In cells of the Leclanché type,
a mixture of plaster of Paris, flour, and sal ammoniac takes the place
of the solution which acts chemically upon one of the contained metals.
When used up, a dry cell must be replaced by an entirely new cell. Two
or more dry cells constitute a _dry battery_.
We have seen that there are two types of charged bodies, of which
charged glass and charged silk are familiar examples. It was Dufay
(1699-1739) who discovered that there were two kinds of electricity,
one of which he called _vitreous_ (from glass) and the other
_resinous_ (from resin—amber). The terms “positive” and “negative”
in relation to electricity were first applied by Benjamin Franklin,
in 1756. To the electricity of the glass rod Franklin gave the name
“positive” and to that of the sealing-wax (or hard rubber, amber, etc.)
the name “negative.” These names are now universally in use—though
French physicists still speak of vitreous and resinous electricity.
I have spoken also of a positive pole (or electrode) and a negative
pole (or electrode). The electrodes constituting the two poles of a
current are also called the anode and the cathode, the former being the
positive electrode and the latter the negative electrode.[18]
When it was learned that electrical charges could be distinguished by
two opposing terms—positive and negative—it was natural to suppose that
there were two distinct kinds of electricity, or “fluids.” This was
the view taken by the French chemist Dufay. But the German electrician
Æpinus (1724-1802), in his great pioneer work, “_Tentamen Theoriae
Electriciatis et Magnetismi_” (An Attempt at a Theory of Electricity
and Magnetism—1759), considered the mathematical consequences of the
hypothesis of a single fluid, attracting all matter but repelling
itself. It soon became apparent, however, that he must assume either
the existence of two electrical fluids or the mutual repulsion of
material particles. He chose the latter theory. He explained the
phenomena of the opposite poles as results of the excess and deficiency
of a “magnetic fluid,” which was dislodged and accumulated in the
ends of the body, by the repulsion of its own particles, and by the
attraction of iron and steel, as in the case of induced electricity.[19]
Æpinus, who was unquestionably one of the greatest physicists of the
eighteenth century, devised a method of examining the nature of the
electricity at any part of the surface of a body, by which means he was
enabled to ascertain its distribution. He found that the distribution
was in agreement with the attractions and repulsions which objects
exert when they are in the neighborhood—“electrical atmosphere”—of
electrified bodies. Today we say that such bodies are electrified by
induction.
The Æpinian theory of electricity and of magnetism was modified and
presented in a new form (in 1788) by Coulomb, with two fluids instead
of one. His first task, before reducing the theory to calculation,
was to determine the law of the forces involved—not being satisfied,
for example, with Newton’s assumption that the attractive force of
magnetism is inversely to the _cube_ of the distance. Mayer in
1760, and Lambert a few years later, had found the law to be that of
the inverse square. Coulomb desired experimental confirmation of this
law before accepting it as established. This he secured by means of
his torsion-balance (about 1784).[20]
It was in pursuance of this investigation that Coulomb brought to light
for the first time the fact that the directive magnetic forces which
the earth exerts upon a needle is a constant quantity, parallel to the
magnetic meridian, and passing through the same point of the needle
whatever be its position.
Barlow, who had adopted the two-fluid hypothesis, showed that the
magnetic “fluids” were collected at the surface of spheres (of iron),
the surface being the only part in which there could be detected any
magnetism. He demonstrated that a shell of iron produces the same
effect as a solid ball of the same diameter. Poisson’s later analysis
(1824) showed that this was a consequent to be expected. Merz has well
said that what Laplace did for Newton was done by Poisson (1781-1840)
“for Coulomb’s elementary law of electric and magnetic action, and
on a still larger scale by Gauss, who worked out the mathematical
theory and applied it to the case of the magnetic distribution on the
earth’s surface. In England, already before Coulomb’s researches were
published, Cavendish had, likewise by a combination of experiment and
calculation, established the elementary formulae and properties of
electrical phenomena.”[21]
Benjamin Franklin, the first American to gain international renown as a
scientist, adopted and developed a “one-fluid theory of electricity.”
On this supposition the parts of the fluid repel each other, and
the excess in one surface of the glass—for example—repels the fluid
from the other surface. The fluid itself was regarded by Franklin as
positive, the part of the other (negative electricity) being taken by
ordinary matter, the particles of which were supposed to repel each
other and attract the positive fluid, just as the particles of the
negative fluid did on the two-fluid theory.
On both the two-fluid and the one-fluid theories, as we have seen, the
particles of the positive fluid repelled each other by forces varying
inversely as the square of the distance between them—as shown by both
Æpinus and Coulomb. This is true also of the particles of the negative
fluid. The particles of the positive fluid attracted those of the
negative fluid. In Franklin’s one-fluid theory it was the ordinary
particles of matter which attracted the positive fluid and repelled
one another. Both theories from their very nature imply, as Sir J. J.
Thomson long ago (1906) pointed out, the idea of action at a distance.
In his very interesting book, “Matter and Energy” (1912), Professor
Soddy says: “All electrical phenomena can be explained as well on the
one-fluid as on the two-fluid idea, but our ignorance at the present
time as to whether there are two kinds of electricity or one is
fundamental. Until the question is settled, the hopes that have been
entertained that, through the study of electricity, we shall be able to
arrive at a philosophical explanation of matter, are likely to prove
unfounded.”
Our modern view of electrification bears a close resemblance to the
one-fluid theory of Franklin, whether we suppose there is one kind of
electricity, or two kinds. At all events, if there be such a separate
force, or such units of energy, as “positive” electricity, it has never
been isolated, as have been the negative atoms or electrons. Negative
electrification is but a collection of these negative corpuscles
or unit charges. The particles of the “electric fluid” of Franklin
correspond to these electrons.
“Instead of taking, as Franklin did, the electric fluid to be positive
electricity, we take it to be negative,” says J. J. Thomson, in
his “Corpuscular Theory of Matter” (1906). And “the transference
of electrification from one place to another is effected by this
motion of corpuscles from the place where there is a gain of positive
electrification to the place where there is a gain of negative.
A positively electrified body is one that has lost some of its
corpuscles.”[22]
FOOTNOTES:
[14] Jeans, J. H., “Electricity and Magnetism,” Page 483, 1911.
[15] Benjamin Franklin was first to show (in a letter to Peter
Collinson, written October 19, 1752) that lightning and electricity are
one and the same thing. He was also inventor of the lightning-rod.
[16] “Potential” is analogous to level (or pressure) in hydrostatics or
mechanics.
[17] For further explanation, see Shipley, Maynard, “The A. B. C. of
the Electronic Theory of Matter,” Little Blue Book Series, No. 603.
[18] See, in this connection, Shipley, _Op. cit._
[19] A very similar hypothesis was read before the Royal Society by
Henry Cavendish, in 1771, the work of Æpinus being unknown to him at
the time.
[20] By means of this instrument very minute forces can be accurately
measured, such as electrostatic or magnetic attraction and repulsion,
by the torsion (turning or twisting) of a wire or filament, the angle
of torsion being proportional to the amount of force exerted.
[21] Merz, Henry, “History of European Thought in the Nineteenth
Century,” Vol. I, Page 362.
[22] For a recent work on modern electrical theory, see Starling,
Sydney G., (head of the department of physics in the West Ham Municipal
College, London), “Electricity,” London, 1922. For the pioneer work of
Ampère, see his “_Theorie des Phenomenes Electrodynamiques_,” 1826.
CHAPTER 5
MODERN MAGNETIC THEORY
We have already shown how the magnetism of a magnet is converted into
electricity, by means of rotating coils cutting the lines of magnetic
force in the “field.” The energy used to drive the machinery may, of
course, be derived either from water-power or by steam. Gravity gives
energy to falling water; chemical energy produced by the oxidation
of coal becomes heat energy, which in turn causes the expansion of
steam, which produces energy of motion in a piston; and this motion,
transmitted to the parts of an engine to a dynamo, produces electrical
energy. When the electric current from the dynamo has been conducted
to any desired point by cables, another motor, acting in the opposite
sense, causes the electricity to change back again into the original
mechanical energy, less the loss due to imperfections in the operation.
Here we have, then a clear picture of what is meant by the phrase,
_transformation of energy_.
But another question naturally arises at this point. We know that with
a finite quantity of magnetism we can produce an unlimited quantity of
electricity. Yet we add no new material, no source of supply, to the
dynamo. Let the rotating coils continue to cut the lines of magnetic
force in the magnetic field, and the magnetism of the magnet will be
transformed into current electricity—furnishing a literally exhaustless
supply from the great storehouse of nature. For us the energy of
the universe is infinite in quantity. The reservoir of energy is
exhaustless, and the dynamo is man’s open sesame.
But just here the very interesting question arises: Is the
inexhaustible supply of electric current with the expenditure of a
limited quantity of magnetism fully explained by saying that it is due
to the rotational movement of the coil? Can the mere rotation of a
metal in a magnetic field actually _create_ an endless supply of
available energy? Not likely! As Dr. Gustave Le Bon well says: “Such a
metamorphosis would be as marvelous as transformation of lead into gold
by simply shaking it in a bottle. Another interpretation must be sought
for the phenomenon.”
Now, a current of electricity is known to be a stream of electrons
(negative charges) flowing along or in a conductor; and an electron
is an atom of—_energy_. But where was this energy stored? “In
the all-pervasive ether,” say many physicists. “There is no ether,”
say others. The electromagnetic field represents energy storage _in
space_—not in a universal, incomprehensible, paradoxical something
called “ether.”
A field of _energy_ is intelligible. It takes the place of the
conception of action at a distance and of the ether. No “ether” need
be postulated as the carrier of the field energy in space. It is its
own carrier. “Energy is the only real existing entity, the primary
conception, which exists for us because our senses respond to it”
(Steinmetz).
“Lines of force,” says Dr. N. R. Campbell, the famous English
physicist, “are just lines of force, independent for their existence of
all surrounding bodies, and there is no more to be said about them....
Our Electrical theory, so far from providing additional support for
the conception of the ether filling all space, does not require such a
conception at all.”
Dr. Le Bon finds the exhaustless source of electricity in the interior
of atoms. The atoms in one pound of earth contain enough energy to run
all the factories, mills, railroads, etc., and light all the cities and
villages of the United States, for a month, Steinmetz tells us. “It
would,” he states further (“Relativity and Space,” Page 45), “supply
the fuel for the biggest transatlantic liner for 300 trips from America
to Europe and back. And if this energy of one pound of dirt could be
let loose instantaneously, it would be equal in destructive powers to
over a million tons of dynamite.”
From the above statement, we may well understand Dr. Le Bon’s
interpretation of the work of a dynamo: “Matter being easily
dissociated and constituting an immense reservoir of intra-atomic
energy, it is enough to admit that the lines of force seized upon by
the conducting body (the coils), which cuts them and causes them to
flow in the form of an electric current, are constantly replaced at the
expense of the intra-atomic energy. This latter being relatively almost
inexhaustible, a single magnet can furnish an almost infinite number of
lines of force.”
It can be shown that the kinetic energy of one kilogram (2.2 pounds)
weight of matter is about 9000 millions of millions of kilogram-meters,
or 25 thousand million kilowatt-hours (a kilowatt-hour = 1000 watt
hours). This means, in other words, that the quantity of energy in the
atoms of 2.2 pounds of ordinary matter is thousands of million times
greater than the energy of an equal quantity of coal, _released by
chemical combustion_.
Estimating the total energy consumed during the year on earth for
heat, light, power, etc., as about 15 millions of millions (=
15,000,000,000,000) of kilowatt-hours, Steinmetz tells us that 600
kilograms, or less than two-thirds of a ton, of “dirt,” if it could be
disintegrated into energy, would supply all the heat, light and energy
demand of the whole earth for a year.
Several eminent physicists are now specializing on the problem of how
to liberate and control intra-atomic energy for man’s uses—or abuses.
Bearing in mind the present intellectual, moral and economic status of
our “leaders of thought” and their followers, and remembering that one
pound of common soil contains intra-atomic energy equal in destructive
power to more than a million tons of dynamite, let us hope that the
secret of releasing and “controlling” intra-atomic energy will not be
discovered in our day and age.
CHAPTER 6
PROOF THAT ELECTRONS ARE ATOMS OF ELECTRICITY
THE ZEEMAN EFFECT
Heinrich Hertz demonstrated in 1887 that he could produce in the
“ether”—or at least in space—what are now known as “wireless waves,”
by allowing a charge of electricity to oscillate to and fro. Larmor and
Lorentz were, at the same time, endeavoring to formulate a theory which
would account for the production of the far shorter light-waves.
Lorentz supposed that each atom contained one or more infinitesimal
particles, or electric charges (electrons), whose excessively rapid
vibrations caused the emission of light-rays. Maxwell showed that there
must be a close connection between light and electricity, a theory
converted into demonstrable fact by the work of Hertz.
That there is a similar relation between light and magnetism was the
firm conviction of Faraday. In 1845, he placed a block of very dense
glass between the poles of the most powerful electromagnet produceable
at the time. Before turning on the switch, he allowed a beam of light
to pass through the glass, producing “polarization”—a modification
of light-rays resulting from their reflection (in this case from a
crystalline substance), imparting to the beam a definite direction—the
plane of vibration or plane of polarization. When the switch was
closed, permitting the flow of the electric current, which produced
the magnetic field, the beam of light was “rotated.” That is, the beam
of light was “plane-polarized” by the crystal, and “rotated” by the
magnetic field; i. e., now changed into two “circularly polarized”
rays, one a left-handed motion and the other a right-handed motion (in
the direction of the hands of a watch).
This could be accounted for only on the theory that light is affected
by magnetism, since the beam was not rotated by the glass alone—in
itself a very important discovery. But the experiment did not yield
Faraday an answer to the question uppermost in his mind: namely, can
a magnetic field change the rate of vibration of a light-emitting
particle? That is to say, in effect, can a magnetic field cause a ray
of light to shift its normal place in the spectrum?
It was not until 1862, seventeen years after the experiment just
described, that Faraday attempted to solve this important theoretical
problem. He now placed a sodium flame in front of the slit of the
spectroscope, which normally yields two characteristic yellow lines
(the D lines of the spectrum), and observed them with the best
spectroscope at his command, under the most powerful electromagnetic
field which he could produce. No change from the normal could be
detected. Other observers tried the same experiment, but with negative
results. We know that his theory was well founded, and that only the
lack of a better spectroscope and a more powerful magnet prevented his
discovery of what is now known as the Zeeman effect—a discovery which
has already thrown a flood of light on a number of difficult physical
problems.[23]
Working with much more powerful apparatus, but following the same
method of procedure employed by the immortal Faraday, Dr. Pieter
Zeeman, of Leyden, succeeded, in 1896, in experimentally demonstrating
the close relationship between light and magnetism. Dr. H. A. Lorentz,
then Professor of Physics in the University of Leyden, now mathematical
physicist at the Norman Bridge Laboratory of Physics, Pasadena,
California, had predicted the nature of the change in the spectral
lines to be expected, and this knowledge was used by Dr. Zeeman as a
check on his results.
Using a Rowland grating, instead of a less efficient prism
spectroscope, Dr. Zeeman found that when a relatively weak electric
current was applied, the two sodium lines were merely widened. In a
still more powerful magnetic field, each of the lines was decomposed
into two or three components, when the lines of force were parallel
to the line of sight.[24] Moreover, the rays of the components of
each line “were not those of natural light,” but were “polarized in
a characteristic way,” i. e., were circularly polarized in opposite
directions—“the direction of the vibration depending in a simple manner
on the direction of the magnetic lines of force.”[25]
The same effect has more recently been produced in the case of the
spectral rays of nearly—if not quite—all the other elements. The
process, as described by Dr. George Ellery Hale, is very simple: “We
place our iron ore or spark between the poles of a powerful magnet,
and photograph its spectrum. The lines behave in the most diverse way,
some splitting into triplets, others into quadruplets, quintuplets,
sextuplets, etc. One chromium line is resolved by the magnet into
twenty-one components.... The distance between the components of a line
is directly proportional to the strength of the magnetic field.”[26]
The meaning of this splitting and polarization of light-rays in the
magnetic field is that, as Lorentz had predicted, there are present
in the luminous vapor vibrating particles negatively charged, or
“electrons.” Measurement of the distances apart of the components of
the triple line reveals the relation between the charge and the mass of
the particles.[27]
It is interesting to add that the disturbances in the magnetic field,
as observed by Zeeman, were precisely of the amount calculated by
Lorentz purely on theoretical grounds, and the mass of the electron
was found by this method to be 1/1840 that of the hydrogen atom. By
a different method, Sir J. J. Thomson obtained a value of 1/1800 the
mass of the hydrogen atom; while Dr. Robert A. Millikan, by means of
his famous “electrical balance,” derived a value of 1/1845 that of the
hydrogen atom.[28]
In his monograph of 1913, Zeeman remarked that in discoveries of optics
“we may always cherish the hope that they will lead ultimately to
applications to astronomy.” So far as study of solar phenomena and the
Zeeman effect are concerned, this hope has been fully realized, and
attempts are being made to extend the applications of this method of
investigation to other stellar bodies. Of the general value of Zeeman’s
discovery, Dr. Hale writes: “The complex phenomena of the Zeeman effect
(as revealed in a comparative study, with powerful spectrographs, and
an intense magnetic field, of the lines of a long list of elements)
furnish material available for wide generalization, important in
their bearing on theories of radiation and atomic structure” (_Op.
cit._, Page 36).
Discovery by Hale and his co-workers at Mount Wilson of the Zeeman
effect in sun-spots led to the very important conclusion that these
disturbances represent whirling vortices of electrons, producing a
magnetic field. “The strength of the magnetic field produced, which is
measured by the degree of separation of the triple lines, increases
with the diameter of the spot.... It has long been known that sun-spots
usually occur in pairs, and our study of the Zeeman effect indicates
that the two principal spots in such a group are almost invariably of
opposite polarity” (Hale, Op. cit., Pages 28-31).
The sun, like the earth is now known to be a magnet, whose general
magnetic field is about 80 times as intense as that of the earth. At
the distance of the earth the solar magnetic field is not appreciable,
“since the effect of one pole counteracts the equal and opposite effect
of the other pole.”
Were it not for our knowledge concerning the Zeeman effect, it would
not yet be known for a certainty that the sun is a vast magnetic globe,
since this fact could not be assumed to be a source of the sun’s
gravitational power. “Indeed,” says Dr. Hale,[29] “its attraction
cannot be felt by the most delicate instruments at the distance of
the earth, and would still be unknown were it not for the influence
of magnetism on light. Auroras, magnetic storms, and such electric
currents as those that recently deranged several Atlantic cables are
due, not to the magnetism of the sun or its spots, but probably to
streams of electrons, shot out from highly disturbed areas of the solar
surface surrounding great sun-spots, traversing 93 million miles of the
ether of space, and penetrating deep into the earth’s atmosphere.”
By means of the famous 150-foot tower telescope at Mount Wilson,
which produces at a fixed point in a laboratory an image of the sun
about sixteen inches in diameter, the magnetic phenomena of sun-spots
are being studied to great advantage, the enlarged sun-spots making
possible separate observation of their various parts. “This analysis
is accomplished with a spectroscope 80 feet in length, mounted in
a subterranean chamber beneath the tower.” By this means the very
important discovery was made by Director Hale that the entire sun,
rotating on its axis, is a great magnet. “Hence,” says Dr. Hale, “we
may reasonably infer that every star, and probably every planet, is
also a magnet, as the earth has been known to be since the days of
Gilbert’s ‘_De Magnete_.’ Barnett has succeeded in producing
magnetism by rapidly whirling masses of metal in the laboratory” (Hale,
“The New Heavens,” Pages 69-70).
More recently (October, 1922), Hale, Ellerman and Nicholson, all of the
Mount Wilson Observatory, have detected _invisible_ sun-spots by
searching for evidences of the Zeeman effect in promising regions, such
as areas of flocculi following a large spot. “A special polarizing
apparatus permits very small magnetic fields to be found by the
alternate widening to red and violet of the iron triplet Lambda 6173,”
say Hale and Adams (“Summary of the Year’s Work at Mount Wilson,”
Publications of the Astronomical Society of the Pacific, October, 1922,
Pages 269-70 [Vol. XXXIV, No. 201]). “The results confirm the view that
a spot represents a vortex, which becomes visible only when the cooling
due to the expansion (of gases) is sufficiently great to produce a
perceptible decrease in the brightness of the photosphere.”
From what has been said, it is evident that Dr. Zeeman’s desire to
see the results of his discovery applied to the study of astronomical
problems has been fully realized.
THE STARK EFFECT
Lorentz’s prediction regarding the effect of a strong magnetic field
on spectral rays, and the movements of electrons in the field having
been confirmed so brilliantly by Zeeman, it remained to ascertain what
effect, if any, would be exerted by electrical force on light-rays.
The answer to this problem was given by Prof. Johannes Stark, at
Aix-la-Chapelle, in 1913, by his skillful demonstration of the
electrical decomposition of the spectral rays of hydrogen, helium and
lithium.[30]
Stark’s task was a more difficult one than Zeeman’s, owing to the fact
that he had to deal with luminescent gases, which, being conductors,
exhaust the electrical field almost before any observations can be
made, even hurriedly. This condition gives rise to difficulties in
connection with the application of the electric field. But these were
very ingeniously met by employment of highly evacuated tubes and the
light emitted by the “canal rays”—positively charged particles similar
to the alpha rays.[31] Where the rays issue from the perforated
electrode (or “canal”), the conduction of electricity is weak, and
Stark was able to apply intense electric fields in a small space. It
was then found that the diffuse rays of the spectrum produced were
strongly influenced, while the “sharp” rays were less so.
The attentive reader will note that this result was in marked contrast
with the _magnetic_ decomposition produced in the Zeeman
experiment, in which the rays did not differ one from another in
respect to the degree of their decomposition. In all the details there
is a difference between the electric and magnetic decompositions, and
analogy existing only in this, namely, that in both cases polarized
rays were obtained. In both cases the results produced were due
to disturbance of the _motions of electrons_, giving rise to
broadening, displacement or other modifications of spectral laws. Both
“effects” confirm the theoretical view of Maxwell, namely, that light
is an electromagnetic phenomenon.
Faraday’s famous question is thus more than answered in the
affirmative: not only is the rate of vibration of “atoms” (electrons)
changed by a magnetic field, but also under the action of an
electrostatic field, producing _decomposition_ of certain spectral
lines, which are usually _polarized_, as in the Zeeman effect.
As a result of his intensive investigations of the Zeeman effect, Dr.
Henri A. Deslandres, Director of the Astrophysical Observatory at
Meudon (a southern suburb of Paris), proposed a new general formula
which represents the series relationship of the component lines and
heads of bands both for emission and absorption spectra. According to
his experimentally-derived law, “the origin of these radiations may be
found in the transverse and longitudinal vibrations of the atoms.”
The lamented Dr. P. S. Epstein, a gifted pupil of Sommerfeld, who—like
Mosely—fell a martyr to the World War, succeeded in applying the
quantum dynamics to the Stark effect, whereby the motions of the
electron in producing the H-beta (in the blue-green) and H-gamma (in
the violet) lines observed, “are accounted for with great accuracy”
(Loring, “Atomic Theories,” Page 67).
It may be said in conclusion, that the most promising attempts fully
to explain the phenomena of the Zeeman and Stark effects seem to be
made from the point of view of Planck’s Quantum Theory of Light. On the
other hand, it must be admitted that there has not been, so far as I
can ascertain, any theory proposed which explains _all_ of the
phenomena involved.
FOOTNOTES:
[23] For a good summary of the main results concerning the Zeeman
effect, see von Auerbach, Felix, “_Moderne Magnetik_,” Leipsic,
1921. An excellent account of the quantum treatment of the Zeeman
effect may be found in Chapter XV (Series Spectra) of Dr. N. R.
Campbell’s “Modern Electrical Theory, Supplementary Chapters,”
Cambridge University Press, 1921.
[24] It seems that this phenomenon had previously been observed by
M. Fievez. (Cf. Michelson, Dr. Albert A., “Light Waves and Their
Uses,” Page 107.) “He thought that each separate line was doubled or
quadrupled.” Lockyer, in 1866, observed that some of the lines in a
sun spot spectrum were widened. Prof. Charles Young and W. M. Mitchell
observed that some of the lines were even double, but it was not
suspected that these phenomena were caused by a strong magnetic field
in sun-spots, brought about by free electrons being driven around
in a vortex movement. In fact, Mitchell referred to the doublets as
“reversals.”
[25] Zeeman, “_Les Lignes Spectrales et les Theories Modernes_,”
_Scientia_, January 1, 1921, Page 18 (Vol. XIX, No. CV—I).
[26] Hale, “Ten Years Work of a Mountain Observatory,” Pages 29-30,
Washington, D. C. (Carnegie Institution of Washington), 1915. See also,
Babcock, Harold D., “The Zeeman Effect for Chromium,” _Contributions
from Mount Wilson Observatory_, Vol. II, Paper No. 52; also “The
Correspondence between Zeeman Effect and Pressure Displacement for the
Spectra of Iron, Chromium and Titanium,” Arthur S. King, Loc. cit.,
Paper No. 46; and “The Zeeman Effect on the Sun,” Adriaan van Maanen,
_Publications of the Astronomical society of the Pacific_, Page
24, Vol. XXXIV, No. 197 (February, 1922).
[27] Zeeman, _Loc. cit._, Page 18. See also the classical
monograph by the same author, “Researches in Magneto-Optics,” London,
1913.
[28] Millikan, _Physical Review_, 2, 143 (1913); “The Electron,”
1917 (revised edition, 1924). See also, _Proceedings of the National
Academy of Sciences_, 3, 314 (1917).
[29] “The New Heavens,” Page 70, New York, 1922.
[30] Cf. Stark, “_Die Atomionen chemischere Elemente und ihre
Kanastrahlenspektra_,” Berlin, 1913. See also, “_Elektrische
Spektralanalyse chemischen Atome_,” Leipsic, 1914.
[31] Called “canal rays” by the German physicist, Eugen Goldstein, who,
in 1886, first obtained them by the use of a perforated cathode; that
is, he used a metallic tube for a cathode, through which tube, called
by Goldstein a “canal,” the rays issued.
CHAPTER 7
THE DISCOVERY OF WIRELESS TELEGRAPHY
The experimental foundation for the discovery of wireless telegraphy
was laid by the researches of Faraday.[32]
Accepting Faraday’s physical views as a point of departure, James
Clerk Maxwell (1831-1879), Professor of Experimental Physics in the
University of Cambridge, began (about 1860) the development of his
constructive speculations in electrical theory which culminated in the
now universally accepted electromagnetic theory of light.[33]
Fourteen years after the publication of Maxwell’s classic treatise,
Heinrich Hertz (1859-1894)—a brilliant pupil of Helmholtz
(1821-1894)—succeeded in producing electrical discharges from a Leyden
jar, which oscillations in turn gave rise to electromagnetic waves of
far greater length than any previously known.[34]
Hertz demonstrated also that the velocity of propagation of these
waves was the same as that of light-waves—approximately 186,000 miles
a second, equivalent to about seven times the circumference of the
earth in one second. It was shown that the only difference between the
Hertzian (“wireless”) waves, for example, and the light-waves, is in
their respective length, or, reciprocally, their rates of vibration per
second. Hertz later demonstrated that these invisible waves produced by
a Leyden jar could be reflected, refracted, and polarized, as in the
case with the far shorter light-waves or rays.[35] These results had
been predicted by Maxwell.
In this great discovery the foundation for wireless telegraphy and
wireless telephony was laid—for Hertz had found what are now known
as “wireless” or radio waves—destined, perhaps, to revolutionize our
methods of obtaining power for machinery, and for transportation, as
they have already revolutionized our methods of communication. Hertz
had done more than this: for his investigations made possible a far
more satisfactory research into the structure of atoms.
“If we were asked to pick out one date that stands out more
prominently than others in our acquisition of knowledge bearing upon
the structure of matter,” says Dr. Albert C. Crehore, “it might be this
epoch-making work of Hertz.”[36]
While it is true that the waves that Hertz discovered and measured
“differ from light-waves merely in wave-length or period of vibration
and quality,” on the other hand the difference in wave-length is so
great that no instrument had as yet been devised to measure or detect
waves that were meters long, as compared with light-waves but a minute
fraction of a centimeter in length.
It was Hertz’s task—following up Maxwell’s prediction—to devise an
instrument which would detect waves not cognizable by our senses alone.
For this purpose he used a simple loop of wire with the ends brought
near together, each terminating in a metal ball. When these balls were
brought almost into contact, a small electrical spark was seen to pass
between the balls when the “oscillator”—the apparatus used to generate
the oscillating currents, or electric waves, of high frequency—was set
in operation.[37]
Hertz not only proved that the speed of electric waves is the same as
that of light, and that they are subject, under certain conditions, to
“interference” as are light-waves, but he also succeeded in actually
measuring the length of the waves produced by his crude apparatus.
This was accomplished by producing what are known as “standing waves,”
analogous to the sound-waves produced by an organ-pipe. Moving his
detector slowly along the wire, Hertz observed that the spark would
appear when a certain interval of space was reached, and as he
continued to move the detector the sparks would disappear and reappear
at regular distances. He rightly concluded that these points of
disappearance and reappearance of the spark corresponded to the nodes
and loops of the “standing waves,” representing the wave-length of the
electrical undulations.
It has since been established that the difference in wave-length
between the electric undulations produced by Hertz and those of
light-waves may be enormous or quite moderate. Professor Michelson
tells us that “a telegraphic wave”, which is practically an
electromagnetic disturbance, may be as long as 1000 miles. The waves
produced by the oscillations of a condenser, like a Lyden jar, may be
as short as 100 feet; the waves produced by a Hertz oscillator may
be as short as one-tenth of an inch. Between this and the longest
light-wave there is not an enormous gap, for the latter has a length of
about 1/1000 inch. Thus the difference between the Hertz vibrations and
the longest light-wave is less than the difference between the longest
and shortest light-waves, for some of the shortest oscillations are
only a few millionths of an inch long. Doubtless even this gap will
soon be bridged over.[38]
The Hertz apparatus was greatly improved by Auguste Righi, in the
University of Bologna. In the same class in physics was Marconi, who
began his fruitful experiments in 1895, one year after Sir Oliver
Lodge had perfected the coherer. Lodge’s coherer, used by Marconi in
his early work, consisted of a glass tube containing a pinch of nickel
and silver filings in equal parts. Crude as this detector was, judged
by present-day standards, it materially improved the conductivity of
contact metals in the case of Hertzian waves.
In 1899 wireless communication was established across the English
Channel, and in 1902 Marconi sent the first wireless message from
England to America. Today, wireless waves measuring miles from crest to
crest are being employed in the transmission of messages from points
separated by thousands of miles, and the human voice has already been
carried across the Atlantic by radiophone, but only in one direction.
The wireless sending and receiving station of the Dutch government,
at Kootmyck, in the Province of Gelderland, is equipped to employ
a 12,000-meter wave-length in sending and receiving simultaneously
messages between Holland and Java, 7,500 miles distant. It has the
same capacity as our Long Island (Rocky Point) station, and is
therefore one of the biggest in the world.
On December 19, 1922, a long distance phonograph which records sounds
made hundreds of miles away was demonstrated to the Society of Western
Engineers, by E. H. Colpitts, of the Western Electric Company. The
transmission of electric power by radio is as yet but a dream; but it
is a dream which may come true within the next five years.[39]
Signals are now being received from stations situated at distances as
great as 12,000 miles, made possible, it is believed by the existence
of an electrical conducting layer—electrified dust expelled by the
sun—some 150 miles in depth, the bending of the radio-waves around the
earth being caused by diffraction. Some unknown factor is operating
to give the signals a strength millions of times greater than can be
accounted for at present by any plausible theory, according to Prof. J.
A. Fleming (Fifth Henry Truman Wood Lecture before the Royal Society of
Arts, London, 1922).
It is not reasonable to assume that no other electromagnetic waves
remain to be discovered. We may yet hear “the roar of the sun-spots,”
though Edison’s experiments along this line were unsuccessful. What,
indeed, were the mysterious “signals” occasionally reported as having
been received at Marconi wireless stations—registered, it was reported
in the press, “only when a minimum of sixty-five-mile wave-lengths had
been established,” but waves issuing from the mighty sun, 93,000,000
miles distant? However, Marconi tells us that one of the “signals”
comes as three short raps—“S” in the Morse code. He believes that these
“signals” may have been sent out from Mars or Venus. Similar mysterious
“signals” were reported by wireless stations in different parts of the
world during the apposition of Mars in August, 1924.
“Outside of the radio-waves that are floating about there may be
hundreds of others which we have not as yet been able to register....
There may be many other waves coming to us from the sun, of which we
have no knowledge today.... The human ear cannot hear below eight
vibrations per second and not higher than about 30,000 vibrations per
second. Certain animals can hear below and above that scale. By means
of our vacuum tubes certain researches indicate that a tremendous
amount of noise goes on below the eight vibrations per second, and
still more noise above the 30,000 vibrations. Entirely new worlds lie
in these two directions, of which nothing is known today. The vacuum
tube is likely to solve these mysteries and take us into the uncharted
worlds, far into the unknown, within the next few years.”[40]
In March, 1922, the late Dr. Charles P. Steinmetz said that he
considered well founded the supposition that performances of low-power
radio sending apparatus in transmitting messages to surprising
distances gave an indication that the radiations peculiar to wireless
transmission pass with equal ease through the earth or through the
“ether.”
Such radiations would be in accordance with accepted electrical laws,
as the ground, to which both the sending antennae and the receiving
set are connected, would act as a return circuit for the current.
Similarly, water might serve as a medium for radio conversations
between ships, or between ships and the land.
Moreover, it was announced during the same month that wireless
telephony had been revolutionized by the successful performances of
the duplex transmitters which the General Electric Company had just
completed. Conversations were held between New York and passengers
aboard the steamer “America,” which, at the time, was at a distance of
360 miles from shore.
The three-electrode audion or vacuum tube was perfected in 1912,
making radio-telephony possible. In 1921, Reginald A. Heising, a young
physicist working for a degree of Master of Science at the University
of Wisconsin, conceived the brilliant idea of putting into the vacuum
tube the amount of energy produced by the voice, and then getting it
out many times amplified in the form of high-frequency power in the
antenna. This problem he soon solved, so far as the principle of the
modulation system was concerned, and in 1922 the practical problem was
worked out and the method all but perfected.
All these great utilitarian advances have been made possible by
the researches of men interested in the advancement of knowledge
for its own sake. As has been pointed out recently by Dr. Hale
(“The New Heavens,” Pages 87-88), “Faraday, studying the laws of
electricity, discovered the principles which rendered the dynamo
possible. Maxwell, Henry and Hertz, equally unconcerned with material
advantage, made wireless telegraphy possible.... Wireless telephony and
transcontinental telephony without wires were both rendered possible by
studies of the nature of the electric discharge in vacuum tubes.”
In an interview in December, 1922, Dr. Nikola Tesla gave it as his
opinion, based upon experiments already carried out in his own
laboratory in New York City, that power flashed through space by radio
will soon be employed in all the world’s activities.
“Besides bridging enormous distances in flight and wireless
conversation,” he said, “modern science will span the earth with power
flashed through the air by radio. Airplanes and ships and trains will
carry no fuel, but will run by transmitted energy. With wireless power
no one—explorers, travelers, campers—need be cut off from civilization
and its comforts.”
“Not only that, but we shall see at great distances by aid of wireless
energy. And seeing our neighbors across the oceans will make for a
united social and political world.”
FOOTNOTES:
[32] See his “Experimental Researches in Electricity,” _Everyman’s
Library Series_.
[33] Maxwell, James Clerk, “Treatise on Electricity and Magnetism,”
1873.
[34] The theoretical investigation of the mode of discharge of a
condenser had been given by Sir William Thomson (later Lord Kelvin) in
1853, in the _Philosophical Magazine_ for June of that year.
[35] When all the atoms and molecules of a substance vibrate in one
plane, e. g., as the plane of a train of waves would be if drawn
on this page, the wave is said to be _polarized_. Ordinarily,
light-rays are sent out from particles vibrating in different planes;
they may be vertical or horizontal, or diagonal, or they may move in a
curved path—circles or ellipses. Ordinary light-vibrations are mixed up
together, vibrating in all planes, and special devices—“polarizers”—are
required in order to separate any one particular vibration from the
rest.
[36] Crehore, Dr. Albert C., “The Mystery of Matter and Energy,” Page
28, New York, 1917.
[37] By means of an induction coil coupled to a circuit containing
capacity terminals, thus forming an “oscillatory circuit.”
[38] Michelson, Dr. A. A., “Light Waves and Their Uses,” Pages 160-61.
The gap was closed during the year 1924, heat-waves being measured
which were of such great length as to merge into the shortest Hertzian
or “wireless” waves.
[39] See an interesting article on this question in _Science and
Invention_, December, 1922, Page 744 (Vol. X, Whole No. 116).
[40] Gernback, H., Editorial in _Science and Invention_, December,
1922.
Transcriber’s Notes
pg 24 Changed: conducting plate in the neighborhod of a magnet
to: conducting plate in the neighborhood of a magnet
pg 25 Changed: was affected by on ordinary magnet
to: was affected by an ordinary magnet
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