no lack of trained scientists who could easily have extended the work
of the American college, and added to it a field of advanced work
resembling closely the activity of the European universities. Most
of these men had received their higher academic training in European
universities, and quite a number of them came from Johns Hopkins.
But there were two obstacles: first, lack of experimental-research
facilities; second, lack of leisure for scientific research. Rowland
and his followers recognized the existence of these obstacles, and
demanded reform. Most of the energy of the teachers of physical
sciences was consumed in the lecture-room; they were pedagogues,
“pouring information into passive recipients,” as Barnard described it.
My own case was a typical one. How could I do any research as long as
I had at my disposal a dynamo, a motor, an alternator, and a few crude
measuring instruments only, all intended to be used every day for the
instruction of electrical-engineering students? When the professor of
engineering died, in the summer of 1891, a part of his work, theory
of heat and hydraulics, was assigned to me. The professor of dynamics
died a little later, and his work also was transferred to me. I was to
carry the additional load of lecture-room work temporarily, but was
relieved from it, in part only, after several years. As a reward my
title was advanced to adjunct professor, with an advance of salary to
two thousand five hundred dollars per annum. But in return for this
_royal_ salary I had to lecture three to four hours each forenoon,
and help in the electrical laboratory instruction in the afternoons.
While this pedagogic load was on my back scientific research could
not be seriously thought of. My young colleagues in other colleges
were similarly situated. This overloading of young scientists with
pedagogic work threatened to stunt, and often did stunt, their growth
and also the growth of the rising American university. “Let chairs be
founded, sufficiently but not luxuriously endowed, which shall have
original research for their main object and ambition,” was the historic
warning which Tyndall addressed to the American people in 1873, but
in 1893 there was little evidence that it was heeded anywhere outside
of Johns Hopkins University. But there they had Rowland and a number
of other stars of the first magnitude who had succeeded Joseph Henry,
Barnard, and Draper as leaders of the great movement in favor of higher
scientific research. In 1883 Rowland delivered a memorable address as
vice-president of one of the sections of the American Association for
the Advancement of Science. It was entitled, “A Plea for Pure Science,”
and described the spirit not only of Johns Hopkins of those days but
also of all friends of higher learning in science. That spirit was
advocated here by Tyndall in 1872-1873, and under Rowland’s leadership
it was bound to win our battle for higher ideals in science. The
people of the United States owe a great debt of gratitude to Johns
Hopkins for the leadership in that great movement which, as we see
to-day, has produced a most remarkable intellectual advancement in
this country. Nearly thirty years ago I heard Rowland say in a public
address: “They always say in Baltimore that no man in that city should
die without leaving something to Johns Hopkins.” When he said it
he knew that Johns Hopkins was very poor. It is poorer to-day than
ever, and no rich man in the United States should die without leaving
something to Johns Hopkins, the pioneer university of the United States.
Rowland said once that lack of experimental facilities and of time
was not a valid excuse for neglecting entirely scientific research. I
agreed with that opinion; neglect breeds indifference, and indifference
degenerates into atrophy of the spirit of inquiry. The alternating
current machine of the electrical engineering laboratory at Columbia
was free in the evenings, and so was my time; that is, if my wife
should not object, and, being a noble and unselfish woman, she did not
object. With the assistance of several enthusiastic students, among
them Gano Dunn, to-day one of the most distinguished engineers in the
United States, I started investigating the passage of electricity
through various gases at low pressures, and published two papers in
the _American Journal of Science_. I soon discovered that most of my
results had been anticipated by Professor J. J. Thomson, of Cambridge,
who, in all probability, had received his inspiration from the same
source from which I had received mine. He not only had anticipated me
but, moreover, he showed a much better grasp of the subject than I had,
and had much better experimental facilities. I decided to leave the
field to him, and to watch his beautiful work from the outside. It was
a wise decision, because it prepared me to understand the epoch-making
discoveries in this field which were soon to be announced, one in
Germany and one in France. I turned my attention to another field.
I must mention, however, one of the results which Thomson had not
anticipated and which created quite an impression among astronomers. I
noticed a peculiar appearance in the electrical discharge proceeding
from a small metal sphere which was located in the centre of a large
glass sphere containing air at low pressure. The discharges looked very
much like the luminous corona of the sun which astronomers observe
during eclipses, and which was always a mysterious puzzle in solar
physics. Pasting a tin-foil disk on the glass sphere, so as to hide
the metal sphere and see only the discharge proceeding from it, I
photographed the appearance of the discharge and obtained the pictures
given opposite page 294. The resemblance of these photographs to those
of the two types of the solar corona is most striking. This is what I
said about it at that time:
“The bearing which these experimental results may have upon the theory
of the solar corona I prefer to leave to others to decide. That they
may prove a suggestive guide in the study of solar phenomena seems not
unreasonable to expect.”
[Illustration: ELECTRICAL DISCHARGES REPRESENTING TWO TYPES OF
SOLAR CORONÆ]
[Illustration: SOLAR CORONA OF 1922
Photographed by the Lick Observatory Expedition
to Australia]
In a communication read later before the New York Academy of Sciences
I was much bolder, having previously discussed the subject with my
friends at Johns Hopkins and with the late Professor Young, the famous
astronomer at Princeton. I soon found myself advocating strongly the
electromagnetic theory of solar phenomena. A German professor, Ebert by
name, a well-known authority on electrical discharges in gases, took
me very seriously indeed, which was very flattering, but he claimed
priority. I had no difficulty in establishing my priority through the
columns of _Astronomy and Astro-Physics_, one of whose editors was
George Ellery Hale, to-day the distinguished director of Mount Wilson
Observatory. I was indeed fortunate to make his acquaintance during
that period when both he and I were very young men. His influence
prevented me from running wild with my electromagnetic theory of
solar phenomena. Thanks to the splendid astro-physical researches
at the Mount Wilson Observatory in California under Doctor Hale’s
direction, we know to-day that enormous electrical currents circulate
on the surface of the sun, and we know also from other researches that
negative electricity is shot out from all hot bodies, even from those
not nearly as hot as the sun, and that the solar corona is, in all
probability, closely related to this electrical activity on the sun.
After giving up the subject of electrical discharges in gases I
looked around for another problem of research which I could manage
with my meagre laboratory facilities. Rowland had found distortions
in an alternating current when that current was magnetizing iron in
electrical power apparatus. This distortion consisted of the addition
of higher harmonics to the normal harmonic changes in the current.
This reminded me of harmonics in musical instruments and in the human
voice. Helmholtz was the first to analyze the vowels in human speech by
studying the harmonics which they contained. The vowel o, for instance,
sung at a given pitch, contains in addition to its fundamental
pitch--say one hundred vibrations per second--other vibrations the
frequencies of which are integral multiples of one hundred, that is
two, three, four, ... hundred vibrations per second. These higher
vibrations are called harmonics of the fundamental. Helmholtz detected
these harmonics by the employment of acoustical resonators; it was an
epoch-making research. I proceeded to search for a similar procedure
for the analysis of Rowland’s distorted alternating currents, and I
found it. I constructed electrical resonators based upon dynamical
principles similar to those in the acoustical resonators employed by
Helmholtz. These electrical resonators play a most important part in
the radio art of to-day, and a few words regarding their operation
seem desirable. In fact, there is to-day a cry from the Atlantic
to the Pacific on the part of millions of people who wish to know
what they are really doing when they are turning a knob on their
radio-receiving sets in order to find the correct wave length for a
certain broadcasting station. I am responsible for the operation, and I
owe them an explanation of it.
The mass and form of an elastic body, say a tuning-fork, and its
stiffness determine the pitch, the so-called _frequency_ of vibration.
When a periodically varying force, say a wave of sound, acts upon the
tuning-fork, the maximum motion of the prongs will be produced when the
pitch or frequency of the moving force is equal to the frequency of the
tuning-fork. The two are said then to be in resonance, that is, the
motion of the fork resonates to or synchronizes with the action of the
force. Every elastic structure has a frequency of its own. The column
of air in an organ-pipe has a frequency of its own; so has the string
of a piano. One can excite the motion of each by singing a note of the
same frequency; a note of a considerably different frequency excites
practically no motion at all. Acoustical resonance phenomena are too
well known to need here any further comment. There are also electrical
resonance phenomena very similar to those of acoustical resonance. If
you understand one of them there is no difficulty in understanding the
other.
If an electrical conductor, say a copper wire, is coiled up so as
to form a coil of many turns, and its terminals are connected to a
condenser, that is to conducting plates which are separated from
each other by insulating material, then the motion of electricity in
that conducting circuit is subject to the same laws as the motion of
the prongs of a tuning-fork. Every motion, whether of electricity
or of matter, is determined completely by the force which produces
the motion, and by the forces with which the moving object reacts
against the motion. If the law of action of these several forces
is the same in the case of moving matter as in the case of moving
electricity, then their motions also will be the same. The moving
forces are called the _action_ and the opposing forces are called the
_reaction_, and Newton’s third law of motion says: _Action is equal to
the opposing reaction_. I always considered this the most fundamental
law in all physical sciences. It is applicable to all motions no
matter what the thing is which moves, whether ponderable matter or
imponderable electricity. Twenty-six years ago a student of mine,
Albert R. Gallatin, brother of the present park commissioner of New
York, presented a large induction coil to the electrical laboratory
at Columbia College in recognition of my services to him, because,
he said, this formulation of the fundamental law in the electrical
science, which I have just given, made everything very clear to him.
This was most encouraging to a young professor, and it goes without
saying that ever since that time he and I have been warm friends.
He is a banker and I am still a professor, but the interest in the
fundamental principles in physical sciences are a strong bond of union
between us.
The electrical force which moves the electricity in the circuit, just
described, experiences two principal reactions. One reaction is due
to the lines of electrical force which, attached to the electrical
charge on the condenser plates, are crowded into the insulating
space between these plates. This reaction corresponds to the elastic
reaction of the prongs of the tuning-fork, and follows the same law.
In the case of the tuning-fork the _elastic reaction is proportional
to the displacement_ of the prongs from their normal position; in the
electrical case the reacting force is proportional to the electrical
charges which have been pulled apart, the negative from the positive,
and driven to the plates of the condenser. Call this separation
_electrical displacement_, and the law can be given the same form as
above, namely: _The reacting force is proportional to the electrical
displacement_. The greater the distance between the plates, and
the smaller their surface, the greater is the reaction for a given
electrical displacement. By varying these two quantities we can vary
the electrical yielding, the so-called capacity, of the electrical
condenser. This is what you do when you turn the knob and vary the
capacity of the condenser in your receiving set.
The moving prongs have a momentum, and a change in the momentum opposes
a reacting force, the so-called inertia reaction, which is equal to the
rate of this change. This was discovered by Galileo over three hundred
years ago. We experience the operation of this law every time we bump
against a moving object. The Irish sailor who, after describing the
accident which made him fall from the mast, assured his friends that
it was not the fall which hurt him but the sudden stop, appreciated
fully the reacting force due to a rapid change of momentum. Every boy
and girl in the public schools should know Galileo’s fundamental law,
and they would know it if by a few simple experiments it were taught
to them. But how many teachers really teach it? How many of my readers
really know that law? Just think of it, what an impeachment it is of
our modern system of education to have so many intelligent men and
women, boys and girls, ignorant of so fundamental a law as that which
Galileo discovered so long ago!
The moving electricity has a momentum. The magnetic lines of force
produced by this motion are a measure of this momentum. Their change
is opposed by a reacting force equal to the rate of this change. This
was discovered by Faraday nearly a hundred years ago. The larger the
number of turns in the coil of wire the larger will be the momentum for
a given electrical motion, that is, for a given electrical current. But
how can anybody understand very clearly this beautiful law, discovered
by Faraday, who does not understand Galileo’s simpler discovery? The
fact that electricity, just like matter, has inertia, and that both
obey the same law of inertia, is one of the most beautiful discoveries
in science. Whenever I thought that so many intelligent and cultured
people knew nothing about it I rebelled against the educational system
of modern civilization.
The motion of electricity in the conductor described above overcomes
reacting forces which follow the same laws as the motion of the elastic
prongs of the tuning-fork. The motion of one has, therefore, an analogy
in the motion of the other. In an electrical circuit having a coil
and a condenser the moving electricity has a definite inertia and a
definite electrical stiffness; hence it will have a definite pitch
or frequency for its vibratory motion, just like a tuning-fork; it
will act as a resonator. It is obvious, therefore, that an electrical
resonator, the pitch of which can be adjusted by adjusting its coil
or its condenser or both, is a perfect parallel to the acoustical
resonator. By means of an electrical resonator of this kind, having an
adjustable coil and an adjustable condenser, I succeeded in detecting
every one of the harmonics in Rowland’s distorted alternating currents,
in the same manner in which Helmholtz detected the harmonics in the
vowel sounds, but with much greater ease, because the pitch of an
electrical resonator can be very easily and accurately changed by
adjusting its coil and condenser. There are millions of people to-day
who are doing that very thing when they are turning the knobs on
their radio receiving sets, adjusting them to the wave-length of the
transmitting station. The expression, “adjusting them to the pitch
or frequency of the transmitting station,” is much better, because
it reminds the operator of the analogy existing between acoustical
and electrical resonance. The procedure was inaugurated thirty years
ago in the “cowshed” of old Columbia College. I called it “electrical
tuning” and the name has stuck to it down to the present time. The
word “tuning” was suggested by the operation which the Serbian
bagpiper performs when he tunes up his bagpipes, which I watched with
a lively interest in my boyhood days. Those early impressions had made
acoustical and electrical resonance appear to me later as obvious
things.
The results of this research were published in the _American Journal
of Science_ and also in the _Transactions of the American Institute
of Electrical Engineers for 1894_. They, I was told, had never been
anticipated; and they confirmed fully Rowland’s views concerning
the magnetic reaction of iron when subjected to the magnetic action
of an alternating current. When Helmholtz visited this country in
1893, I showed him my electrical resonators and the research which I
was conducting with their assistance. He was quite impressed by the
striking similarity between his acoustical resonance analysis and
my electrical resonance analysis, and urged me to push on the work
and repeat his early experiments in acoustical resonance, because my
electrical method was much more convenient than his acoustical method.
Helmholtz was always interested in the analysis as well as in the
synthesis of vibrations corresponding to articulate speech. The
telephone and the phonograph were two inventions which always enjoyed
his admiring attention. During his visit in America he looked forward
with much pleasure to meeting Graham Bell and Edison. The simplicity of
their inventions astonished him, because one would hardly have expected
that a simple disk could vibrate so as to reproduce faithfully all the
complex vibrations which are necessary for articulation. He spent a
Sunday afternoon as my guest at Monmouth Beach and in the course of
conversation I told him what impression the telephone had made upon me
when I first listened through it. It happened during the period when I
was serving my apprenticeship as greenhorn, and when I was trying hard
to master the articulation of the English language. The telephone plate
repeated perfectly everything spoken at the other end, and I said to
myself: “These Americans are too clever for me; they can make a plain
steel plate articulate much better than I can ever expect to do it
with all my speaking organs. I had better return to Idvor and become
a herdsman again.” Helmholtz laughed heartily and assured me that the
articulating telephone plate had made a similar impression upon him,
although he had spent several years of his life studying the theory of
articulation. “The phonograph disk is just as clever as the telephone
disk,” said Helmholtz, “perhaps even more so, because it has to dig
hard while it is busily talking.”
My scientific friends in New York saw in the construction of my
electrical resonator and in its employment for selective detection
of alternating currents of definite frequency a very suitable means
for practising harmonic telegraphy, first suggested by Graham Bell,
the inventor of the telephone. They finally persuaded me to apply for
a patent and I did so. I often regretted it, because it involved me
in a most expensive and otherwise annoying legal contest. Two other
inventors had applied for a patent on the same invention. One of them
was an American, and the other a French inventor, and each of them was
backed by a powerful industrial corporation. A college professor with
a salary of two thousand five hundred dollars per annum cannot stand a
long legal contest when opposed by two powerful corporations; but it
is a curious psychological fact that when one’s claim to an invention
is disputed he will fight for it just as a tigress would fight for her
cub. The fight lasted nearly eight years and I won it. I was declared
to be the inventor, and the patent was granted to me. But a patent is
a piece of paper worth nothing until somebody needs the invention.
I waited a long time before that somebody came, and when he finally
showed up I had almost forgotten that I had made the invention. In the
meantime I had nothing but a piece of paper for all my pains, which
nearly wrecked me financially.
Just about that time the newspapers reported that a young Italian
student by the name of Marconi, while experimenting with Hertzian
waves, had demonstrated that a Hertzian oscillator will send out
electrical waves which will penetrate much longer distances when one
of its sides is connected to earth. “Of course it will,” said I, “the
grounded oscillator takes the earth into closer partnership.” When as
a herdsman’s assistant on the pasturelands of my native Idvor I stuck
my knife into the ground and struck its wooden handle, I knew perfectly
well that the ground was a part of the vibrating system, and that the
sound-producing stroke was taken up by the ground much better than when
I struck the knife-handle without sticking the knife into the ground.
But I also knew that unless the boy who was listening pressed his ear
against the ground he would not hear very much. It was, therefore,
quite obvious to me that the best detector for a Hertzian oscillator
which is grounded must be another Hertzian oscillator which is also
connected to the ground. Grounding of the sending and of the receiving
Hertzian oscillators was in fact the fundamental claim of the Marconi
invention. Marconi, in my opinion, was unwittingly imitating the young
herdsmen of Idvor when, figuratively speaking, he stuck his electrical
knives into the ground for the purpose of transmitting and receiving
electrical vibrations, but the imitation was a very clever one; very
obvious indeed as soon as it was pointed out, like all clever things.
Every now and then we are told that wireless signals might be sent
some day to the planet Mars. The judgment of a former herdsman of
Idvor considers these suggestions unscientific for the simple reason
that we cannot get a ground on the planet Mars and, therefore, cannot
take it into close partnership with our Hertzian oscillators. Without
that partnership there is no prospect of covering great distances. A
very simple experiment will illustrate this. Scratch the wood of a
pencil and ask your friends who are sitting around a table whether
they hear the scratching. They will say “No.” Put the pencil on the
table and scratch it again; your friends will tell you that they can
hear it faintly. Ask them to press their ears against the table and
they will tell you that the scratching sound is very loud. In the
third case the pencil, the table, and the ears of your friends are all
one closely interconnected vibratory system. Every herdsman of Idvor
would interpret correctly the physical meaning of this experiment. “If
Marconi had waited just a little longer I should have done his trick
myself,” I said jokingly to Crocker, and then I temporarily dismissed
the matter from my mind as if nothing had happened. But I was fairly
confident that my electrical resonators would some day find a useful
application in this new method of signalling, and Crocker was even more
hopeful than I was. I turned my attention to another problem and would
have completed its solution, if my work had not been interrupted by the
announcement of a most remarkable discovery made in Germany, I mean the
discovery of the Roentgen rays.
I cannot describe the effects of this epoch-making discovery without
referring again to great Helmholtz. It was due to his initiative
that Hertz took up the research of electrical oscillations, which
suggested to Marconi their technical application. This started a new
technical art, wireless telegraphy, which developed into the radio
art. Without Helmholtz, not only the experimental verification of the
Faraday-Maxwell electromagnetic theory but also the radio art might
have been delayed quite a long time. I shall point out now that the
great discovery of the Roentgen rays also was due in a great measure to
the initiative of Helmholtz.