Claremont Hill, St. Helier’s, Jersey,
April 26, 1899.”
_Reply from Prof. D. E. Hughes_:--
40, Langham-street, W., April 29, 1899.
DEAR SIR: In reply to yours of the 26th
inst., in which you say that Sir William Crookes has
told you “that he saw some experiments of mine on
aërial telegraphy, in about December, 1879, of which
he thinks I ought to have published an account,” and
of which you ask for some information, I beg to reply
with a few leading experiments that I made on this
subject from 1879 up to 1886:--
“In 1879, being engaged upon experiments with my
microphone, together with my induction balance, I
remarked that at some time I could not get a perfect
balance in the induction balance, through apparent
want of insulation in the coils, but investigation
showed me that the real cause was some loose contact
or microphonic joint excited in some portion of
the circuit. I then applied the microphone in
the circuit, and found that it gave a current or
sound in the telephone receiver, no matter if the
microphone was placed direct in the circuit, or
placed independently at several feet distance from
the coils, through which an intermittent current was
passing. After numerous experiments, I found that
the effect was entirely caused by the extra current
produced in the primary coil of the induction balance.
“Further researches proved that an interrupted
current, in any coil, through which an electric
current was sent, gave out at each interruption of
the primary current, such intense extra currents,
that the whole atmosphere in the room (or in several
rooms distant) would have a momentary invisible
charge, which became evident if a microphonic joint
was used as a receiver to a telephone. This led me
to experiment upon the best form of a receiver for
these invisible electric waves, which evidently
permeated great distances, and through all apparent
obstacles, such as walls, &c. I found that all
microphonic contacts or joints were extremely
sensitive. Those formed of a hard carbon such as
coke, or a combination of a piece of coke resting
upon a bright steel contact, were very sensitive and
self-restoring; whilst a loose contact between metals
was equally sensitive, but would cohere, or remain in
full contact, after the passage of an electric wave.
“The sensitiveness of these microphonic contacts
in metals has since been rediscovered by Mons. Ed.
Branly, of Paris, and by Prof. Oliver Lodge, in
England, by whom the name of ‘coherer’ has been given
to this organ of reception; but, as we wish this
organ to make a momentary contact and not cohere
permanently, the name seems to me ill-suited for the
instrument. The most sensitive and perfect receiver
that I have yet made does not cohere permanently,
but recovers its original state instantly, and,
therefore, requires no tapping or mechanical aid to
the separation of the contacts after momentarily
being brought into close union.
“I soon found that, whilst an invisible spark would
produce a thermo-electric current in the microphonic
contacts (sufficient to be heard in the telephone in
its circuit), it was far better and more powerful to
use a feeble voltaic cell in the receiving circuit,
the microphonic joint then acting as a relay, by
increasing and diminishing the resistance at the
contact, by the influence of the electric wave
received through the atmosphere.
“I will not describe the numerous forms of the
transmitter, and receiver, that I made in 1879,
all of which I wrote down in several volumes of
manuscripts in 1879 (but these have never been
published), most of which can be seen here at my
residence at any time; but I will confine myself
now to a few salient points. I found that very
sudden electric impulses, whether given out to the
atmosphere through the extra current from a coil, or
from a frictional electric machine, equally affected
the microphonic joint, the effect depending more on
the sudden high potential effect than any prolonged
action. Thus, a spark obtained by rubbing a piece of
sealing-wax was equally as effective as a discharge
from a Leyden jar battery of the same potential. The
rubbed sealing-wax, or charged Leyden jar, had no
effect, until they were discharged by a spark,--and
it was evident that this spark, however feeble, acted
upon the whole surrounding atmosphere in the form of
waves, or invisible rays, of which I could not at
the time determine. Hertz, however, by a series of
original and masterly experiments, proved in 1887-9,
that they were real waves similar to light, but of
a lower frequency, though of the same velocity. In
1879, whilst making these experiments on aërial
transmission, I had two different problems to solve:
1st, What was the true nature of these electric
aërial waves, which seemed, whilst not visible, to
spurn all idea of insulation, and to permeate all
space to a distance undetermined. 2nd, To discover
the best receiver that could act upon a telephone or
telegraph instrument, so as to be able to utilise
(when required) these waves for the transmission of
messages. The second problem came easy to me, when
I found that the microphone, which I had previously
discovered in 1877-8, had alone the power of
rendering these invisible waves evident, either in
a telephone or galvanometer, and up to the present
time I do not know of anything approaching the
sensitiveness of a microphonic joint as a receiver.
Branly’s tube, now used by Marconi, was described in
my first Paper to the Royal Society (May 8, 1878),
as the microphone tube, filled with loose filings
of zinc and silver, and Prof. Lodge’s coherer is
an ordinary steel microphone, used for a different
purpose from that in which I first described it.
“During the long-continued experiments on this
subject, between 1879 and 1886, many curious
phenomena came out which would be too long to
describe. I found that the effect of the extra
current in a coil was not increased by having an
iron core as an electromagnet--the extra current
was less rapid and, therefore, less effective. A
similar effect of a delay was produced by Leyden jar
discharges. The material of the contact-breaker of
the primary current had also a great effect. Thus,
if the current was broken between two, or one, piece
of carbon, no effect could be perceived of aërial
waves, even at short distances of a few feet. The
extra current from a small coil, without iron, was as
powerful as an intense spark from a secondary coil,
and at that time my experiments seemed to be confined
to the use of a single coil of my induction balance,
charged by six Daniell cells. With higher battery
power, the extra current invariably destroyed the
insulation of the coils.
“In December, 1879, I invited several persons to see
the results then obtained. Amongst others who called
on me and saw my results were:--
“December, 1879.--Mr. W. H. Preece, F.R.S.; Sir
William Crookes, F.R.S.; Sir W. Robert Austen, F.R.S.;
Prof. W. Gryll Adams, F.R.S.; Mr. W. Groves.
“February 20, 1880.--Mr. Spottiswoode, Pres.R.S.;
Prof. Huxley, F.R.S.; Sir George Gabriel Stokes, F.R.S.
“November 7, 1888.--Prof. Dewar, F.R.S.; Mr. Lennox,
Royal Institution.
“They all saw experiments upon aërial transmission,
as already described, by means of the extra current
produced from a small coil and received upon a
semi-metallic microphone, the results being heard
upon a telephone in connection with the receiving
microphone. The transmitter and receiver were in
different rooms, about 60 ft. apart. After trying
successfully all distances allowed in my residence
in Portland-street, my usual method was to put the
transmitter in operation and walk up and down Great
Portland-street with the receiver in my hand, with
the telephone to the ear.
“The sounds seemed to slightly increase for a
distance of 60 yards, then gradually diminish, until
at 500 yards I could no longer with certainty hear
the transmitted signals. What struck me as remarkable
was that, opposite certain houses, I could hear
better, whilst at others the signals could hardly
be perceived. Hertz’s discovery of nodal points in
reflected waves (in 1887-9) has explained to me what
was then considered a mystery.
“At Mr. A. Stroh’s telegraph instrument manufactory,
Mr. Stroh and myself could hear perfectly the
currents transmitted from the third story to the
basement, but I could not detect clear signals at
my residence about a mile distant. The innumerable
gas and water pipes intervening seemed to absorb or
weaken too much the feeble transmitted extra currents
from a small coil.
“The President of the Royal Society, Mr.
Spottiswoode, together with the two hon. secretaries,
Prof. Huxley and Prof. G. Stokes, called upon me on
February 20, 1880, to see my experiments upon aërial
transmission of signals. The experiments shown were
most successful, and at first they seemed astonished
at the results, but towards the close of three hours’
experiments Prof. Stokes said, ‘that all the results
could be explained by known electromagnetic induction
effects, and therefore he could not accept my view of
actual aërial electric waves unknown up to that time,
but thought I had quite enough original matter to
form a Paper on the subject to be read at the Royal
Society.’
“I was so discouraged at being unable to convince
them of the truth of these aërial electric waves,
that I actually refused to write a Paper on the
subject, until I was better prepared to demonstrate
the existence of these waves; and I continued my
experiments for some years, in hopes of arriving at
a perfect scientific demonstration of the existence
of aërial electric waves, produced by a spark from
the extra currents in coils, or from frictional
electricity or secondary coils. The triumphant
demonstration of these waves was reserved to Prof.
Hertz, who by his masterly researches upon the
subject in 1887-9 completely demonstrating not only
their existence but their identity with ordinary
light, in having the power of being reflected and
refracted, &c., with nodal points, by means of which
the length of the waves could be measured, Hertz’s
experiments were far more conclusive than mine,
although he used a much less effective receiver than
the microphone or coherer.
“I then felt it was now too late to bring forward my
previous experiments, and through not publishing my
results, and means employed, I have been forced to
see others remake the discoveries I had previously
made as to the sensitiveness of the microphonic
contact, and its useful employment as a receiver for
electric aërial waves. Amongst the earliest workers
in the field of aërial transmission I would draw
attention to the experiments of Prof. Henry, who
describes in his work, published by the Smithsonian
Institute, Washington, D.C., U.S.A., Vol. I., p.
203 (date unknown, probably about 1850), that he
magnetised a needle in a coil at 30 ft. distance, and
magnetised a needle by a discharge of lightning at
eight miles distance.
“Marconi has lately demonstrated that by the use of
the Hertzian waves and Branly’s coherer he has been
enabled to transmit and receive aërial electric waves
to a greater distance than previously ever dreamed
of by the numerous discoverers and inventors who
have worked silently in this field. His efforts at
demonstration merit the success he has received;
and if (as I have lately read) he has discovered
the means of concentrating these waves on a single
point desired without diminishing its power, then
the world will be right in placing his name on the
highest pinnacle in relation to aërial electric
telegraphy.--Yours, &c.,
D. E. HUGHES.”