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