by James P. Rybak, W0KSD
y the year 1887, the 36-year-old
Oliver Lodge was already regarded in
Great Britain as a highly accomplished
scientist. A professor of physics at the
newly-established University College in
Liverpool, he was known for his brilliant
scientific mind and ability to explain
complex scientific principles in a manner
that could be understood by virtually
anyone. In 1887, the Royal Society of
Arts asked Lodge to prepare a series of
lectures, to be given the following year,
concerning how buildings might best be
protected from lightning damage.
The designers of the lightning protection
systems of that time assumed that
lightning was a continuous direct current
discharge. They believed that protection
from lightning could be obtained by
placing copper rods above the buildings
and connecting them to the earth by
means of heavy copper grounding
cables with a very low dc resistance.
The lightning protection "experts" could
and chose what seemed to be higher resistance "alternate paths" to ground.
lightning protection systems was typically blamed poor ground connections.
Lodge had had an interest in learning more about the subject for several years.
He now planned to conduct a series of experiments on electrical discharges prior to
the low-resistance path provided by the copper conductors.
These laboratory investigations proved to be extremely important. They would
Lodge's world-wide reputation as an outstanding scientist.
In addition to demonstrating the effects of inductance in circuits with time-varying
German scientist Heinrich Hertz. Lodge also discovered the phenomenon of
electrical resonance and found that the "coherer" effect provided a very useful
means for detecting the presence of electromagnetic waves.
It was commonly known in 1887 that a lightning discharge is produced when the
that cloud and the earth to increase until the intervening air breaks down electrically
and becomes a conductor. Lodge visualized this as being much the same process
as when the voltage across a capacitor increases until the breakdown of the
(capacitor) produces an oscillatory current rather than a direct current.
The physicist decided to
path" experiments to
attempt to confirm his
theories prior to giving
his first lecture on
lightning in March of
1888. He used Leyden
jar discharges to
simulate lightning. The
jars were usually
charged using a Voss
machine that generated
static electricity through
friction. One of the
arrangements used by
Oliver Lodge is shown
as Figure 1.
The Voss machine was connected to the terminals, A. These, in turn, were
connected to the inner conducting surfaces of two Leyden jars. The outer
conducting surfaces of the jars were connected to an adjustable spark gap, B. A
long loop of very low resistance copper wire, L, was connected across this spark
gap. The wire Lodge first used was approximately 12 meters in length but had a
resistance of only 0.025 ohm.
conductors normally connected to lightning rods.
The electrical charge stored in the Leyden jars could flow either through the very
high resistance path through the air between the spark-gap terminals at B. It would
seem that the obvious path for the charge to follow would be through the low
resistance wire loop. Surprisingly, Lodge was able to produce very large sparks
across the spark-gap, B, even though the dc resistance of the wire across the gap
When Lodge gave his first lecture on lightning to the Royal Society of Arts, he
argued that since (as he believed) lightning discharges have a very high oscillatory
frequency, it is necessary to take inductive reactance effects into account when
predicting which path the discharges will follow. Inductance was not a very well
understood or accepted concept in those days.
Michael Faraday in England and Joseph Henry in the United States, independently
years earlier. Sir William Thomson (Lord Kelvin) in 1853 had recognized the
influence which inductance (Thomson called it "electro-dynamic capacity") has in
causing the discharge of a Leyden jar to be oscillatory.
Oliver Heaviside later demonstrated the importance of inductive effects in the
The concept of inductance, however, did not receive general acceptance or
understanding until Sir William Thomson (Lord Kelvin) publicly endorsed
Heaviside's inductance theories in 1889. Lodge's lectures on lightning, however,
occurred prior to Thomson's endorsement.
Lodge maintained that, at the frequencies involved in the oscillatory lightning
discharge, the inductance of the conducting cables resulted in a very high
opposition to current flow. Therefore, the alternate path actually followed by a
lightning discharge did indeed exhibit the lowest total opposition or impedance to
the current flow even if its dc resistance was not the lowest.
Those in attendance who did not subscribe to Lodge's inductance theories were
Particularly questionable, they argued, was the idea that a lightning discharge is
Years later, Lodge realized that lightning is not an oscillatory discharge but is
actually a rapidly pulsating unidirectional (dc) discharge.
the inductive reactance on the flow of these pulsating lightning currents is the same
as Lodge predicted for
The issue could not be
the March lectures, and
the critics wanted more
to be performed. Further
discussions on lightning
were scheduled for the
meeting of the British
Association to be held at
Oliver Lodge continued
his "alternate path"
experiments during the
electrical oscillations produced by the Leyden jar discharges. He now replaced the
loop of wire he had been using with a pair of long wires, each approximately 29
meters in length (Figure 2). The wires, L and L', were terminated in spark-gaps.
He found that the Leyden jars discharged in the usual manner at spark-gap A, but
Oscillatory currents were produced in the part of the circuit consisting of the Leyden
inductance of the spark-gap wires at A determined the frequency of the
spark occurred at B1, B2, or B3. The spark at B3 always was the longest.
The electrical waves produced by the oscillations at A traveled along the wires and
what he called the "recoil impulse" or "recoil kick" at the end of the wires where the
waves were reflected.
wave had their maximum values and were in phase. This produced a voltage twice
as large as the voltage at spark gap A.
More importantly, Lodge determined that the discharge at B3 was the most intense
multiple of one-half wavelength) for the oscillations produced.
the wires. Oliver Lodge had discovered electrical resonance (or "syntony" as he
later would call it
In addition, the scientist was able to demonstrate that standing waves existed along
the wires. In a darkened room, he observed a visible glow along the wires at one-
half wavelength intervals corresponding to the voltage peaks. He also performed a
number of other experiments concerning the characteristics of discharging Leyden
jars during that spring and summer of 1888.
Oliver Lodge clearly knew that he had produced and detected the electromagnetic
he presented these observations as part of the findings in his study of lightning
conductors, however, Lodge went on vacation in that summer of 1888. It was while
on vacation that Lodge read of Hertz's similar work with electromagnetic waves.
Lodge then added a postscript to his own paper acknowledging Hertz's work in an
of electrical radiation seems working itself out splendidly."
Lodge presented his findings to the British Association meeting in Bath in
the results Hertz recently had published, chaired the meeting. Interestingly enough,
FitzGerald had told Lodge in 1878 that it never would be possible for anyone to
produce the electromagnetic waves predicted by James Clerk Maxwell. By 1882,
however, FitzGerald had corrected his erroneous belief.
FitzGerald suggested that electromagnetic waves might be produced by
discharging a capacitor through a very small resistance.
Those in attendance and, later, other knowledgeable people, recognized that
Lodge's findings were equivalent to those of Hertz and had been arrived at
however, would always receive the world's principal acclaim and recognition
because his work was published slightly before that of Lodge.
The electromagnetic waves generated by Hertz were radiated into space whereas
man helped confirm the validity of what the other had done. Lodge and Hertz
corresponded and exchanged scientific papers. They always maintained great
respect and regard for each other as scientists and as human beings.
died in 1894, Lodge wrote a magnificent tribute to his achievements.
In 1894, Lodge discovered that a nonconducting tube containing metal filings
findings were based on an observation made in 1890 by Edouard Branly (1846-
1940). Branly had discovered that the resistance measured across the ends of a
such a tube normally was very high. However, if an electromagnetic wave was
generated nearby, the metal particles became fused together and the resistance
dropped to a low value. The resistance remained low until the tube was tapped and
the fused particles returned to their original, separated condition.
had observed the
metal spheres in
light contact with
each other when
electromagnetic wave, the "coherer effect." Similarly, he called any detector of
electromagnetic waves based on this effect, a "coherer." He quickly realized that
the "filings tube coherer" represented the most convenient form for utilizing the
coherer effect to detect electromagnetic waves.
Perhaps Lodge's most important improvements to the filings tube coherer were the
evacuation of the air from the tube and the development of an automatic "tapping
back" device which utilised a rotating spoke wheel driven by a clockwork
mechanism. The mechanical impulses provided by the tapping back device
restored the filings tube coherer to its non-conducting state at regular intervals,
independent of the detection of electromagnetic waves. This filings tube coherer
detector was considerably more sensitive than was the simple wire loop "resonator"
with a spark gap that Heinrich Hertz had used as the detector of electromagnetic
waves in his experiments. It also was more convenient to use than was the metal-
sphere coherer detector Lodge had previously developed.
Lodge used his improved filings tube coherer, together with a Hertzian wave
oscillator, as part of a demonstration for a commemorative lecture entitled "The
Work of Hertz" given in London at a meeting of the Royal Institution in June of
1894. A sensitive mirror galvanometer was connected to the coherer so that the
moving beam of light.
Later that same month, Lodge used a small portable
electromagnetic waves at the annual "Ladies' Conversazione" of the Royal Society
He also demonstrated essentially the same apparatus at a meeting of the British
Association held at Oxford in August of 1894. In that demonstration, however, he
replaced the mirror galvanometer with a more sensitive marine galvanometer of the
type normally used for the detection of submarine cable telegraphy signals. Lodge's
source of electromagnetic waves, located in another building some 55 meters
away, consisted of a Hertzian oscillator energized by an induction coil. A telegraph
key connected to the primary winding of the induction coil was used by Lodge's
assistant to send both long and short duration trains of waves, corresponding
somewhat to Morse code dots and dashes.
Those in attendance witnessed
55 meter distance.
Lodge clearly had all the necessary elements of an elementary wireless telegraphy
signaling of a sort in all three of these demonstrations, there is no indication that the
sending of any true messages was accomplished or even attempted with this
apparatus. It was not his intent to do so. Oliver Lodge never considered using his
equipment for communicating, although the idea of wireless telegraphy had been
suggested two years earlier by William Crookes.
The first two demonstrations were performed simply to show that electromagnetic
Oxford was to propose that perhaps there exists an analogy between the way a
coherer responds to electromagnetic waves and the way the eye responds to
Oliver Lodge later admitted that, at the time, he had not seen any advantage in
replace the well developed and comparatively easy process of telegraphing with the
use of connecting wires.
He, like virtually all of his contemporaries, believed at the time that electromagnetic
light is nothing more than electromagnetic waves with very short wavelengths.)
Consequently, Lodge assumed that the maximum possible range attainable using
wireless signaling would be very limited. These reasons help to explain why, in
Lodge's own words, ". . . stupidly enough no attempt was made to apply any but the
feeblest power so as to test how far the disturbance could really be detected."
recognized what they had in their hands, might have earned the principal credit for
the development of wireless telegraphy.
In all fairness, however, one should never think that Lodge was lacking in either
when conducting experiments had been demonstrated time and time again. But he
was first and foremost a scientist and teacher, more concerned with theory than
While Oliver Lodge is remembered for numerous significant scientific
achievements, including his contributions to the development of wireless
telegraphy, it might be said that he let "the two big ones" slip through his fingers.
Had he proceeded with his alternate path experiments a little more rapidly, Lodge
might be the one whom we today credit with having experimentally verified
Maxwell's predictions. Similarly, if Lodge had realized the potential of wireless
communication, Marconi might have had to share with him the unofficial but
commonly used title "Father of Radio."
Those wishing to read about other aspects of Oliver Lodge's life are referred to the
University Press, Liverpool, 1990.
November12, 1897, pp. 86-91.
and July 6, 27, 1894, pp. 153-155, 186-190, 204-205, 271-272, 362.
November 12, 1897, pp. 86-91.
Crookes, William; "Some Possibilities of Electricity," The Fortnightly Review,
February 1,1892, pp. 173-181.
1908, pg. 84.
pp. 62-66 and 95.