TESTIMONY OF CONTEMPORARY WITNESSES.
1. Professor G. Quincke.
2. Professor C. Bohn.
3. Herr Léon Garnier.
4. Ernest Horkheimer, Esq.
5. Dr. R. Messel, F.C.S.
6. Herr Heinrich Holt.
7. Herr Heinrich F. Peter.
8. Mr. Stephen M. Yeates.
9. Dr. William Frazer.
Professor G. Quincke,
_Professor of Physics in the University of Heidelberg_.
[Professor Quincke, whose name is so well known in connection
with his researches in molecular physics and in many problems
of the highest interest to those acquainted with electrical
science, was one of those present at the Naturforscher
Versammlung held at Giessen in 1864, where Reis’s Telephone
was publicly exhibited by its inventor, see page 93, _ante_.
His testimony, coming from so high authority, is therefore of
exceptional value.]
“Dear Sir,
“I was present at the Assembly of the German Naturalists’ Association
(Naturforscher Versammlung) held in the year 1864 in Giessen, when
Mr. Philipp Reis, at that time teacher in the Garnier Institute at
Friedrichsdorf, near Frankfort-on-the-Main, showed and explained to the
assembly the Telephone which he had invented.
“I witnessed the performance of the instruments, and, with the
assistance of the late Professor Böttger, heard them for myself.
“The apparatus used consisted of two parts--a transmitter and a
receiver. The transmitter was a box, one side of which was furnished
with a tube into which the speaking was to be done. At the top or the
side of the box there was a circular opening, covered by a tympanum of
membrane, upon which was fastened a piece of platinum. This piece of
platinum was in communication with one pole of the galvanic battery.
Over the membrane, resting upon the platinum, and in contact with
it, was a piece of metal furnished with a platinum point, also in
connection with one pole of the battery.
“The receiver consisted of a common knitting needle of steel,
surrounded by a magnetising coil of insulated wire, which also formed a
part of the circuit, the whole resting on a resonant box.
“I listened at the latter part of the apparatus, and heard distinctly
both singing and talking. I distinctly remember having heard the words
of the German poem, ‘Ach! du lieber Augustin, Alles ist hin!’” &c.
“The members of the Association were astonished and delighted, and
heartily congratulated Mr. Reis upon the success of his researches in
Telephony.
(Signed) “Dr. G. Quincke, Professor.
“Heidelberg, 10th March, 1883.”
* * * * *
Professor C. Bohn.
[Professor C. Bohn, of Aschaffenburg, was formerly Secretary
to the German “Naturforscher” Association, was also Secretary
to the Physical Section of this Society (vide p. 93). In that
capacity he had every opportunity of knowing what was going on
in science; hence the following (translated) letter, addressed
to the author of this book, is of peculiar value.]
“Most esteemed Sir,
“I willingly answer, as well as I am able to do so, the questions put
by you. In order to explain that my recollections may not have all
the sharpness that might be wished, I make the following prefatory
statement. I have, about 1863, held numerous conferences with Mr.
Reis and with my deceased colleague, Professor H. Buff, of Giessen,
and on these occasions have argued the question how it is that the
transmission of thoughts to a distance by the sensation of the ear has
a distinctly less value than transmission by that which is written....
“And now to your questions. I was not at Stettin in 1863. At the
experiments at Giessen in the Naturforscher Assembly on 21st
September, 1864, I was present; the short notice about them in
the journal (‘Tagesblatt’) is from my pen. I was Secretary of the
Assembly and of the Physical Section. I remember, however, almost
absolutely nothing about _these_ experiments. But I remember well that
_previously_--therefore probably as early as 1863--having jointly made
the experiments with Reis’s telephone in Buff’s house in Giessen....
I have _myself_, as speaker and as hearer, at least twice, in the
presence of Reis, made the experiments.
“It was known to me (in 1863-64) that Reis intended to transmit words,
and certainly spoken words as well as those sung. My interest in the
matter was, however, a purely scientific one, not directed to the
application as a means of profit.
“With great attention the sense of the words was understood. I have
understood such myself, without knowing previously what would be
the nature of the communication through the telephone. Words sung,
especially well accentuated and peculiarly intoned, were somewhat
better (or rather less incompletely) understood than those spoken in
the ordinary manner. There was indeed a boy (son of Privy-Councillor
Ihering, now of Göttingen, then of Giessen), who was known as specially
accomplished as a speaker. He had a rather harsh North-German dialect,
and after the first experiments hit on the right way to speak best,
essential for understanding. I myself _did not_ understand Professor
Buff through the telephone. Whether the speaker could be recognized
by his voice I doubt. We knew beforehand each time who speaks. Yet I
remember that a girl could be distinguished from that boy by the voice.
“The ear was at times laid upon the box of the apparatus, also upon the
table which supported the telephone. Then it was attempted to hear at a
distance, with the ear in the air; in this respect, when singing, with
good result. At times the lid was taken off, or the same was connected
more or less tightly or loosely with the lower part. The result of
these changes I can no longer give with distinctness....
“Should you desire further information, I am ready to give you it
according to my best knowledge.
“Hochachtungsvoll ergebenster,
“Dr. C. Bohn.
“Aschaffenburg,
“_10th September, 1882_.”
* * * * *
Léon Garnier.
[Herr Léon Garnier, Proprietor and Principal of the Garnier
Institute at Friedrichsdorf, is the son of the late Burgomaster
Garnier, who founded the establishment, and who, as previously
narrated, encouraged Philipp Reis in his work and offered him
the post of teacher of Natural Science. Herr Léon Garnier owns
the small collection of instruments which Reis left behind, and
which are preserved in the Physical Cabinet attached to the
Institute, where also may be seen the gravitation machine--an
ingenious combination of the principles of Atwood’s and Morin’s
machines--and the automatic weather-recorder invented by Reis,
both, however, very greatly out of repair. Herr Garnier has
furnished to a friend the following particulars about Reis and
his invention.]
“I knew Philipp Reis, now deceased, during his life-time.... About the
year 1859, he was employed by my father, then proprietor and director
of the Friedrichsdorf Garnier Institute, as teacher of mathematics and
natural sciences. He employed his hours of leisure in experimenting
for himself in a house occupied by himself, and in which he had
established a physical laboratory with a view mainly of realizing
an idea which he had conceived sometime before of transmitting the
human voice over divers metallic conductors by means of a galvanic
current.... I remember especially, that, standing at the end of
the wire or conductor, Mr. Reis speaking through his instrument, I
distinctly heard the words: ‘Guten Morgen, Herr Fischer’ (Good morning,
Mr. Fischer); ‘Ich komme gleich’ (I am coming directly); ‘Passe auf!’
(Pay attention!); ‘Wie viel Uhr ist es?’ (What o’clock is it?); ‘Wie
heisst du?’ (What’s your name?) We often spoke for an hour at a time.
The distance was about 150 feet.
“Léon Garnier.”
* * * * *
Ernest Horkheimer, Esq.
“Manchester, _Dec. 2, 1882_.
“Professor S. P. Thompson,
“Dear Sir,
“In reply to your favour of 31st instant, I shall be very happy to
give you all the information I can with respect to the telephonic
experiments of my late friend and teacher Mr. Philipp Reis. I would
express my gratification at finding that you are trying to put my old
teacher’s claims on their just basis. I have always felt that in this
race for telephonic fame, his claims have been very coolly put aside
or ignored. That he did invent the Telephone there is not the remotest
doubt. I was, I think, a great favourite of his; and at the time his
assumption was that I was destined for a scientific career, either
as a physicist or a chemist; and I believe that he said more to me
about the telephone than to any one; and I assisted him in most of his
experiments prior to the spring of 1862.
“Philipp Reis intended to transmit speech by his telephone--this
was his chief aim; the transmitting of musical tones being only an
after-thought, worked out for the convenience of public exhibition
(which took place at the Physical Society at Frankfort-on-the-Main). I
myself spent considerable time with him in transmitting words through
the instruments. We never (in my time) got the length of transmitting
complete sentences successfully, but certain words, such as ‘_Wer da?_’
‘_gewiss_,’ ‘_warm_,’ ‘_kalt_,’ were undoubtedly transmitted without
previous arrangement. I believe Reis made similar experiments with his
brother-in-law.
[Illustration: Fig. 35.]
[Illustration: Fig. 36.]
“I recollect the instrument in the shape of the human ear very well:
it was Reis’s earliest form of transmitter. The transmitter underwent
a great many changes, even during my time. The form you sketch (Fig.
9, p. 20) was almost the oldest one, and was soon superseded by the
funnel-shape (Fig. 35). The back was always closed by a tympanum
of bladder, and many a hundred bladders were stretched, torn, and
discarded during his experiments. I recollect him stating to me that
he thought a very thin metal tympanum would eventually become the
proper thing, and one was actually tried, coated over on one side with
shellac, and on the other likewise, except at the point of contact
(Fig. 36). I believe it was made of very thin brass, but at the time
the experiments were not satisfactory. Talc was also tried, but without
success, the platinum contacts being in all cases preserved.
“I remember very well indeed the receiver with a steel wire, surrounded
by silk-covered copper wire. The first one was placed on an empty
cigar-box, arranged thus:--
[Illustration: Fig. 37.]
“The wire was a knitting-needle and the copper wire was spooled on a
paper case.
[Illustration]
“The spiral was supported by a little block of wood, so as to allow the
knitting-needle not to touch it anywhere. Later on a smaller cigar-box
was invented as a cover--thus; (Fig. 38)--having two holes cut into it
like the _f_-holes in a violin.
[Illustration: Fig. 38.]
“The practice was to place the ear close to the receiver, more
particularly so when the transmission of words was attempted.
“The spiral was, during the early experiments, placed on a violin--in
fact, a violin which I now possess was sometimes used, as it was of a
peculiar shape, which Reis thought would help the power of tone.
“I have already enumerated some of the words which were transmitted,
but there were many more; on one occasion a song, known in this country
as ‘The Young Recruit’ (Wer will unter die Soldaten) was transmitted,
the air and _many_ of the words being clearly intelligible.
“I do not recollect seeing the receiver shewn in the woodcut (Fig.
21), but Reis often said that he would make such a one, although the
sketch he made for me then differed in some details from your woodcut.
Reis intended to keep me fully informed of all he could achieve,
but, immediately after leaving his tuition, I fell ill, and was laid
up for a very long time. Shortly afterwards I left for England, and
then he died, and I never saw him again. The electromagnet form was
certainly strongly in his mind at the time we parted, and he drew many
alternative suggestions on paper, which have probably been destroyed;
but the electromagnets in all of them were placed upright, sometimes
attached to the top of a hollow box, and sometimes to the bottom of a
box arranged thus (Figs. 39, 40); but, to my recollection, they never
got beyond the stage of drawings, whatever he may have done after he
and I parted company.
[Illustration: Fig. 39.]
[Illustration: Fig. 40.]
“In conclusion, I beg to send you herewith a photograph of Philipp
Reis (see Fig. 12, p. 23), holding in his hand the instrument I helped
him to make, and which photograph he took of himself, exposing the
camera by a pneumatic arrangement of his own, and which formed part
of a little machine which he concocted for turning over the leaves of
music-books.
“The instrument used by Reis at the Physical Society may have been
the square block form: I believe that this cone-form was not quite
completed then. At the Saalbau (Hochstift), however, I am _sure_ the
instrument shown in my photograph was employed; not with a tin cone,
but a wooden one. I send you herewith a sketch of what I remember that
instrument to have been. I am not absolutely certain whether in the
instrument there was not an electromagnet introduced, but I think not.
My recollection leads me to suppose that the electromagnet arrangement
was added subsequently. Thinking it over again, I should, however,
think that the instrument in the photo must have been one in which a
bent lever was placed behind the tympanum, and that the rectangular
patch seen above was a wooden casing to shelter the parts. There may
be some confusion in my mind as to the position of this box, but I
somehow think the rectangular patch is only part of a larger box which
is not apparent in the photograph. I have no idea where the original
instrument is now, but I should hardly think it could be in existence.
Reis used to take some instruments to pieces to utilise parts in
subsequent experiments, and I recollect how keen he used to be about
the bits of platinum, which he always described as ‘ein sehr kostbares
Metall.’ What always was a great puzzle was the attaching of the
platinum plate to the membrane, which he did generally by sealing-wax,
saying at the same time: ‘Es ist nicht recht so, aber ich weiss nicht
wie es anders gemacht werden kann!’
“Believe me, my dear Sir, yours truly,
“Ernest Horkheimer.”
* * * * *
Dr. Rudolph Messel.
[The following letter from Dr. Rudolph Messel, F.C.S.,
addressed to the author of this book, in reply to enquiries
concerning Reis and his inventions, speaks for itself. Dr.
Messel’s letter differs from almost all the others here
reprinted in having been specially written for the purpose of
being inserted in this volume.--S. P. T.]
“36, Mark Lane, London, _30th April, 1883_.
“Dear Professor Thompson,
“At last I find a moment to comply with your request. My knowledge
of Philipp Reis dates from 1860, when I was a pupil at Professor
Garnier’s School at Friedrichsdorf, of which school Reis was one of
the undermasters. Reis, naturally communicative, was very fond of
talking to us boys about his scientific researches. And it was on the
occasion of one of our daily walks together that he told me how, when
an apprentice at Beyerbach’s (colour-manufacturer), in Frankfurt-a.-M.,
he was one day amusing himself in watching the behaviour of a small
magnetic compass. This compass he found, on being placed near to
the base of various iron columns in the warehouse, was attracted.
Disturbed by the entrance of one of the principals, who imagined
that Reis ought to employ his time more profitably, he withdrew to a
stage where he could pursue his experiments unobserved. Much to his
surprise, he now found that the pole attracted by the base was repulsed
at the top of the columns, which observation led him to examine
other pieces of iron on the premises. He next built up a column with
all the weights in the warehouse, and having verified his previous
observations, he communicated what he believed to be his first and
great discovery either to Professor Böttger or to Dr. Oppel. Great was
his disappointment to learn at this interview that he had unwittingly
stumbled across a well-known physical fact: but his disappointment
stimulated in him the desire to learn more of the marvellous laws and
mysteries of nature. That Reis evoked a similar desire in those with
whom he came in contact need not cause surprise, and thus it came
about that Horkheimer, Küster, Schmidt, and myself, soon enjoyed the
privilege of private instructions in physics, and of being permitted
to witness his telephonic experiments amongst others. I was, however,
very young, and am sorry that much that I then saw and heard has been
forgotten, Reis insisted that his transmitter (which he called the
‘ear’) should be capable of performing the functions of that organ, and
he never tired of drawing diagrams of the numerous curves of sounds to
explain how necessary it was that the transmitter should follow these
curves before perfect speaking could be attained, and which kind of
curves the instrument so far could reproduce. Numerous experiments
were made with transmitters, exaggerating or diminishing the various
component parts of the ear. Wooden and metallic apparatus, rough and
smooth, were constructed in order to find out what was essential, and
what was not.
[Illustration: Fig. 41.]
“One form of transmitter was at that time constructed which I miss
amongst the various woodcuts you were good enough to send me, and one
which Reis based great hopes upon. The instrument was very rough,
however, consisting of a wooden bung of a beer-barrel (which I had
hollowed out for an earlier telephone--it was not turned inside
like others), and this was closed with a membrane. The favourite
‘Hämmerchen’ was replaced by a straight wire, fixed in the usual way
with sealing-wax, and the apparatus stood within a sort of tripod,
membrane downwards, the pin just touching the surface of a drop of
mercury contained in a small cup forming one of the terminals of the
circuit. The apparatus started off with splendid results, but may
probably have been abandoned on account of its great uncertainty,
thus sharing the fate of other of his earlier instruments. In my
belief it is to these mechanical imperfections, due principally to
the want of sufficient means at his command, that we must look to
find the reason why Reis’s telephone did not come to an earlier fame.
Thus Reis informed me that he intended to exhibit it once at some
scientific meeting at Cassel, but notwithstanding a perfect rehearsal
it was impossible to show the working to the audience; the failure
was attributed by Reis to atmospheric influence (stretching of the
diaphragm), and he felt much grieved at having lost his chance. To
make matters worse, the early transmitters had no adjusting screws,
and the contact was only regulated by a piece of bent wire, and the
‘hammer’ was fixed to the membrane. Philipp Schmidt should recollect
what I state, as many experiments were made when only he, Reis, and
myself were present, he being at one and I at the other end of the
apparatus. The wire was stretched from Reis’s house, in the main road,
through the yard to a hayloft, near the garden or field. We transmitted
musical sounds (organ, &c.), singing popular songs (‘Wer will unter die
Soldaten,’ ‘Ich hatt’ einen Kameraden,’ &c.) and speaking, or, more
correctly, reading. We had a book, and were to find out what part of
the page the reader was just transmitting. We frequently used a sort
of ‘Exercier Reglement,’ a soldiers’ instruction book, or something of
that sort. I have a distinct recollection of electromagnetic receivers
being used, but not of their construction, except that the use of
one of them was accompanied by a rattling and disturbing noise. The
knitting-needle put in the _f_ of a violin was, however, the more
favoured receiver, but at this time, in Reis’s mind, all seemed to
hinge on the electromagnet, as it had before, and, I dare say, did
again afterwards on the transmitter. I left Friedrichsdorf in ’62, and
rarely saw Reis after that, except a few times at Mechanicus Albert’s
(who made some of his apparatus), and at Professor Böttger’s, to whom
he introduced me. Reis attended Professor Böttger’s lectures at the
Physikalischer Verein, when in Frankfort, prior to his settling down
at Friedrichsdorf; but I do not know that any particularly intimate
relation existed between them. Dr. Poppe, director of the Gewerbeschule
(Trade School), now deceased, on whose advice he chiefly relied,
was then one of his more intimate friends, Professor Oppel being
occasionally consulted about more intricate mathematical problems. Of
the ‘meteorological recorder’ invented by Reis I recollect but its
existence, but nothing at all of a ‘fall-machine’ of his construction.
The velocipede I only recollect, because he lent it to me for a
masquerade. At his suggestion we altered it into a large musical-box,
putting Herr Peter inside, who played on the clarinet when I turned
a handle. Dr. Kellner states that its chief merit consisted in being
able to go downhill, and that poor Reis came back (uphill) puffing
away, dragging his velocipede behind him. Kellner no doubt could give
valuable information on Reis’s theory of electricity, his conviction
that there was only one kind of electricity, his acoustic researches,
and those on radiation of electricity, his galvanoplastic experiments,
&c., &c.
“In personal appearance Reis was not very refined, but he had a
striking countenance and a very powerful look. Though occasionally
very irritable, especially with dunces, he was always warm-hearted,
and showed great kindness to those who cared to understand him. Reis’s
views of the telephone may, of course, have changed after I knew
him, and looking at his later instruments, one of which I possess, I
cannot help thinking they did; at any rate, I do not see how, in these
instruments, the current got interrupted at all, and the instruments
must have acted like microphones, whether known or unknown to him. When
listening to the instrument he frequently said to me, “You understand
it is a ‘molekular Bewegung’ (molecular motion).
“I am sorry that, owing to the lapse of time, I am unable to throw
more light on Reis’s original labours in a field of physical science
which promised so much for the future; but insufficient as are my
recollections, they may not be without public interest, and at any rate
I am glad of this opportunity of offering my humble tribute of regard
and affection to the memory of my old teacher and friend.
“Yours truly,
“Rudolph Messel.”
* * * * *
Heinrich Hold.
[Herr Hold, formerly a colleague of Philipp Reis in the Garnier
Institute at Friedrichsdorf, but now proprietor of a leather
factory in the same place, was teacher of mathematics. He was
in his younger days a fellow-student of Professor Tyndall
at Halle, and was well acquainted with physical science in
general. His intimate connection with Reis, and close knowledge
of Reis’s work, enable him to confirm the testimony of others
in many important points.]
To Professor S. P. Thompson in Bristol.
“Esteemed Sir,
“I have much pleasure in furnishing you with the following particulars
concerning my late colleague Philipp Reis, the inventor of the
Telephone. He was himself educated at the Garnier’s Institute in
Friedrichsdorf where I was also teacher of mathematics. I knew him very
well during his life-time. Among his numerous original researches,
his invention of the telephone was the principal one. His idea was
to reproduce the tones both of musical instruments and of the human
voice by means of electricity, using a covered wire wound in a spiral
round an iron core, the same being placed upon a resonant box. In
this he succeeded, inasmuch as with an apparatus, which he showed
to the Physikalischer Verein in Frankfurt-a.-M., in the year 1861,
he reproduced music, singing, single words and short sentences; all
of which were distinctly audible over a short distance from his
dwelling-house through the yard to the barn. Every voice was not
equally well adapted for speaking into the apparatus, neither could
every ear understand the telephone language equally well. Words spoken
slowly, and singing, both in a middle tone, were the most easy to
reproduce. I helped Mr. Reis to make many of his experiments, and have
spoken and sung into the telephone, the same being generally heard and
understood. I have also heard and understood short sentences when I was
standing at the end station. A brother-in-law of Mr. Reis, who is now
paymaster in the Imperial Navy at Wilhelmshavn, generally conducted the
speaking and singing in the telephone.
“Heinrich Hold.”
* * * * *
Heinrich Friedrich Peter.
[Herr Peter is still Music-teacher in the Garnier Institute,
and has a vivid recollection of his former colleague Philipp
Reis, and of the experiments with the telephone.]
“Dear Sir,
“The following particulars concerning Reis’s Telephone I have several
times narrated. I was teacher of music in Garnier’s Institute at the
time when Mr. Reis invented the telephone, in the year 1861. I was much
interested in his experiments, and visited him daily, giving him help
and making suggestions. His first idea was to imitate the construction
of the human ear. He constructed a funnel-shaped instrument, the back
of which was covered with a skin of isinglass, upon which was fastened
a piece of platinum, against which rested a platinum point. As receiver
of the electric current he used a common knitting-needle, surrounded
by a coil of insulated green wire, which was at first merely laid on a
table. At first the tones were very much interfered with by a buzzing
noise. At my suggestion he placed the spiral upon my violin as a
resonant-box; whereupon the tones were perfectly understood, though
still accompanied by the buzzing noise. He continued experimenting,
trying various kinds of membranes, and made continual improvements
in the apparatus. I was present and assisted at the experiments at
Frankfort-on-the-Main, on the 26th of October, 1861; and after the
meeting broke-up, I saw the members of the Society as they came and
congratulated Mr. Reis on the success of his experiments. I played
upon the English horn, and Philipp Schmidt sang. The singing was
heard much better than the playing. At an experiment which we made
at Friedrichsdorf, in the presence of Hofrath Dr. Müller, Apothecary
Müller, and Professor Dr. Schenk, formerly Director of Garnier’s
Institute, an incident occurred which will interest you. Singing was
at first tried; and afterwards his brother-in-law, Philipp Schmidt,
read long sentences from Spiess’s ‘Turnbuch’ (Book of Gymnastics),
which sentences Philipp Reis, who was listening, understood perfectly,
and repeated to us. I said to him, ‘Philipp, you know that whole
book by heart;’ and I was unwilling to believe that his experiment
could be so successful unless he would repeat for me the sentences
which I would give him. So I then went up into the room where stood
the telephone, and purposely uttered some nonsensical sentences, for
instance: ‘Die Sonne ist von Kupfer’ (The sun is made of copper),
which Reis understood as, ‘Die Sonne ist von Zucker’ (The sun is made
of sugar); ‘Das Pferd frisst keinen Gurkensalat’ (The horse eats no
cucumber-salad); which Reis understood as ‘Das Pferd frisst....’ (The
horse eats ...). This was the last of these experiments which we tried.
Those who were present were very greatly astonished, and were convinced
that Reis’s invention had opened out a great future.
“H. F. Peter, Musiklehrer.”
* * * * *
Stephen Mitchell Yeates, Esq.
[Illustration: Fig. 42.]
[Mr. Yeates is a well-known instrument-maker in the city of
Dublin, and in 1865, purchased from Mr. W. Ladd, of London,
a Reis’s Telephone of the form shown in Reis’s Prospectus
(Fig. 29). Mr. Yeates, after a few experiments, rejected the
knitting-kneedle receiver, and replaced it by the instrument
shown in Fig. 42, which consisted of an electromagnet mounted
above a sound-box, having a vibrating armature furnished
with an adjusting screw to regulate its distance from the
poles of the electromagnet. This instrument worked, even when
the armature was in absolute contact with both poles of the
electromagnet, and as the magnet did not during the experiments
lose its hold on the armature, it was clear that the effects
were due to alterations in the intensity of the magnetism of
the magnet. The apparatus was shewn at the November meeting
of the Dublin Philosophical Society, when singing and words
were transmitted. With a careful adjustment it was possible
to distinguish all the quality of the note sung into the
transmitter and to distinguish the difference between any
two voices. The instruments were then sold to the late Rev.
Mr. Kernan, who was then Professor of Physics in Clongowes
Wood College. The following recent letter from Mr. Yeates
corroborates the above facts.]
“2, Grafton Street, Dublin,
“_March 1st_, 1883.
“Dear Sir,
“There are several residing at present in Dublin who were present at my
telephonic experiments in 1865; three of them, namely, Dr. W. Frazer,
Mr. A. M. Vereker, and Mr. E. C. Tuke, took an active part in the
experiments, and remember all the circumstances connected with them.
The voice of each was instantly recognised in the receiver; in fact,
this point attracted special attention at the time.
“I had no knowledge at that time that Reis had used an electromagnetic
receiver, nor did I know that Reis was the inventor of the instrument
which I got from Mr. Ladd.
“The original instrument made by me is, I believe, still in the Museum
at Clongowes Wood College. The President kindly lent it to me some
time ago, and I returned it to him again after showing it to Professor
Barrett. I have a cut of this receiver, which I will send to you if it
will be of any use to you.
“Yours truly,
“S. M. Yeates.”
* * * * *
William Frazer, Esq., M. D.,
“20, Harcourt Street, Dublin,
“_March 13_, 1883.
“Dear Sir,
“I have a distinct recollection of the Telephone. We had a small
private club meeting once each month for scientific purposes. On
referring to my note-books, I find that there was a meeting on Thursday
evening, October 5th, 1865. It was held in Nassau Street, at the
residence Mr. Horatio Yeates, now in Australia, and brother of Mr.
Stephen Yeates. The Telephone was upstairs, in the third story of the
house, and the voice heard in the hall. Mr. Vereker, of the Bank of
Ireland, Mr. John Rigby, of rifle celebrity, the two Mr. Yeates, and, I
think, Mr. Tuke, were present with myself. There were some others, whom
I cannot now recollect, but our club was small.
“Rigby sang ‘Patrick’s Day’ and ‘God save the Queen,’ and various
questions were asked and answered. The separate words were most
distinct, the singing less so; but there was no difficulty in
recognising the individual who spoke by his voice.
“Being much interested in the subject, I got Mr. Yeates to allow the
apparatus to be shewn at a Conversazione (Presbyterian Young Men’s)
at the Rotunda on October 12, at 8 P.M. His assistant, Mr. Tuke, took
charge of it that night. It was placed in a side room off the main
round room of the buildings.
“I exhibited at the October 5th meeting of our club a specimen termed
‘Locust gum,’ probably derived from some _Robinia_, but really can tell
you nothing more about it. There is merely a brief note of it in my
private memoranda.
“Yours, dear Sir,
Believe me very truly,
“William Frazer,
“Fellow and Examiner, Royal College of Surgeons,
“Ireland, Member of Council, Royal Irish
“Academy, &c.”
“Silvanus P. Thompson, Esq., University College, Bristol.”
APPENDIX I.
COMPARISON OF REIS’S TRANSMITTERS WITH RECENT INSTRUMENTS.
Any one who compares together the many different forms of Reis’s
Transmitters cannot fail to notice that amidst the great variety of
form, two essential points are preserved throughout, the presence
of which is fundamental. These two essentials are, firstly, the
tympanum to collect the voice-waves, and, secondly, an electric
mechanism, consisting of two or more parts in loose or imperfect
contact with each other, and so arranged in combination with the
tympanum that the motions of the latter should alter the degree of
contact, and consequently interrupt, to a greater or less degree,
the current of electricity flowing between the contact-pieces. It
was of course familiar to all electricians, long before Reis, that a
bad, or imperfect, or loose contact in a circuit offered a resistance
and interrupted the flow of an electric current. In all ordinary
telegraphic and electric apparatus great care was taken to avoid loose
and imperfect contacts by using clamping-screws and solid connectors.
But Reis, having made up his mind (see p. 77) that the action due to
the magnetising current must vary in a manner corresponding with, and
therefore proportional to, the vibrations of the voice, utilised this
property of imperfect contacts which alter their resistance according
to the degree of contact, by arranging his mechanism so as to apply
the voice to vary the degree of contact. This was the essence of his
transmitters. In other words, he applied the voice to control or
moderate the strength of the current generated by a battery. His
“interruptors” may therefore with propriety be called “electric current
contact regulators;” and put into technical language, the essence of
this part of his invention lay in the combination with a tympanum of
electric current regulators working upon the principle of variable
contact.
In another appendix is discussed the precise nature of that which
occurs at a point of variable or imperfect contact, and which results
in a corresponding change of electrical resistance when the degree of
contact is varied. Suffice it to say here that it is impossible to vary
the degree of contact between two bodies which are lightly pressing one
against the other, and through which an electric current is flowing,
without altering the resistance offered to the current by this joint in
the circuit. If the two surfaces are pressed together, so that there is
a good contact, the current flows more freely, finding less resistance.
If, on the other hand, by altering the pressure or the amount of
surface exposed, we change the degree of contact and cause fewer atoms
of one piece to touch those of the other piece, the current meets with
greater obstruction and cannot flow with such strength as before: it is
partially “interrupted,” to use the expressive term employed by Reis.
Now this operation of varying the degree of pressure in order to vary
the resistance of the interrupter or contact regulator, was distinctly
contemplated by Reis. We find his definite instructions, for example
(see p. 75), for arranging the relative lengths of the two parts of
the curved lever in one of his transmitters, so that the movement of
one contact-piece may act on the other contact-piece with the greatest
possible _force_; in other words, he shortened his lever at the working
end, sacrificing its range of motion in order to get a greater range of
pressure at the contact-point.
It has often been said, but incorrectly, that Reis intended his
“interruptors” or contact regulators to make and break the electric
circuit abruptly in the manner of a telegraphic key worked by hand.
No doubt in the mouth of a professional telegraph operator the words
“interrupting” the circuit, and “opening” and “closing” the circuit,
do now-a-days receive this narrow technical meaning. But Reis was not
a professional telegraph operator: he did not (see p. 87) even know
the signals of the Morse code, and it is self-evident that he did not
use the terms in any such restricted or unnatural sense as abrupt
“make-and-break,” because he proposed at the outset to interrupt the
current in a manner represented by the gradual rise and fall of a
_curve_, stating emphatically in his very first memoir on telephony (p.
55), that to reproduce any tone or combination of tones all that was
necessary was “to set up vibrations whose curves are like those” of the
given tone or combination of tones. Moreover, in the construction of
almost all his transmitters, even in the very first--the model of the
human ear--he purposely introduced certain parts which could have no
other effect than to prevent the occurrence of complete breaks in the
continuity of the current. In fact, instead of using rigid supports
for his interruptor, he mounted one or both of the contact-parts
with springs, so that one should follow the movement of the other
with a gentle pressure never amounting to absolute break, except
perhaps in the accidental case of a too loud shout. By employing these
following-springs, he introduced, in fact the element of _elasticity_
into his interruptor; and clearly he introduced it for the very purpose
of avoiding abrupt breaking of the contact. In the first form Fig. 5,
p. 16 (the “ear”), there was one spring; in the fourth form, Figs.
9 and 10, p. 21 (the “bored block”), there were two springs, one of
steel, curved, and one, a straight but springy strip, of copper; in
the eighth form (the “lever” form), Fig. 14, p. 25, there were two
springs; in the ninth form, Fig. 15, p. 26, there was a springy strip
of brass. In the final form, Figs. 17 and 18, p. 27 (the “square-box”
pattern), there was, it is true, a springy strip of copper, but the
light adjustment of contact was in this form obtained, not by a spring,
but by the inertia of the upper contact-piece which by its own weight
pressed gently upon the lower contact-piece. In every one of these
forms, except the last, there was moreover an adjusting-screw to
determine the exact degree of initial pressure between the contact
surfaces. Doubtless the difficulty of adjusting this screw to give the
exact degree of contact, enhanced as that difficulty was in consequence
of the liability of the membraneous tympanum to become flaccid by the
moisture of the breath, induced Reis to think that the later form of
the apparatus in which this adjustment was no longer retained would be
more easy to use, or, as he says in his Prospectus, more accessible
to others. Yet undoubtedly the absence of the spring at the contacts
led some persons to fancy that the instrument was intended to be
shouted or sung to so loudly that every vibration should make the
upper contact-piece jump up from the lower, and as Professor Müller
even suggests (p. 98), produce a spark! But such a manner of using the
instrument would entirely defeat Reis’s most fundamental principle,
that the interruptions should be such as to correspond to the
_undulating curve_ which represents the pressure due to vibration of
the sound-wave; the possibility of representing the degree of pressure
by a curve being one of the two principles set forth in his paper “on
Telephony” (p. 55), in which he remarks, that “Taking my stand on the
preceding principles, I have succeeded in constructing an apparatus by
means of which I am in a position to reproduce ... even to a certain
degree the human voice.” Reis was perfectly well aware, as his curves
show, that a complicated sound-wave does not consist invariably of
_one_ condensation followed by _one_ rarefaction, but that there are
all sorts of degrees of condensation which may follow one another, and
all capable of being represented by a curve. If all sounds consisted of
one rarefaction following immediately after each one condensation there
might be some propriety in proposing that after each “make” of contact
there should be a “break” in the sense of an abrupt or complete breach
in the continuity of the current. But, obviously, the fact that one
condensation may follow another without a rarefaction between (which
Reis’s curves show that he knew) must be amply sufficient to prove
that on Reis’s own principle _his interruptor was meant to produce
variations in the degree of contact in exact correspondence with the
variations in the degree of pressure_, whatever these might be. Had he
not meant this, he could not have talked about “taking his stand” on
the principle of representing varying pressures by an undulatory curve.
Now, from what has been adduced, the following points are clear:--
_Firstly_, that the contact-regulator which Reis combined with the
tympanum was meant to interrupt the current, more or less, according to
the varying movements imparted to it by the voice.
_Secondly_, that Reis intended such interruptions or variations of
contact to be proportional to, or to “correspond” with, the variations
indicated by the undulatory curve of varying pressures.
_Thirdly_, that for the purpose of preventing the occurrence of abrupt
breaks in the continuity of the circuit, he used springs and adjusting
screws, and in one form availed himself of the inertia of the moving
parts to attain a similar end.
It is also clear from his own prospectus, that he was aware that for
the simpler and ruder purpose of transmitting musical airs, in which
the number of the vibrations is the only consideration and where each
single condensation is actually followed by a rarefaction, actual
abrupt breaks in the continuity of the circuit are admissible. Reis
chose this simple case as the one capable of being readily grasped by
a general audience, though it was obviously only a partial explanation
of the action of the apparatus in the simplest case that could be
presented.
* * * * *
Turning now to some of the more modern transmitters, we will
inquire how far Reis’s fundamental principles are involved in their
construction. We will first take Berliner’s transmitter, of which Fig.
43 is a drawing, reproduced from the sketch in the specification of his
British Patent. This transmitter consists of a tympanum of thin metal
to collect the sound-waves, and behind it is attached an interrupter
or current regulator, identical in almost every respect with that of
Reis. One of the contact-pieces, marked _E_, circular in form, is fixed
to the centre of the tympanum, and vibrates with it, precisely as in
Reis’s latest, and in some also of his earlier instruments. Against
this there rests in light contact a second contact-piece, in the form
of a small blunt spike, _F_, screwed into a short arm, loosely jointed
to the part _N_, where the circuit is connected. As in Reis’s latest
transmitter (Fig. 17, p. 27), so here, the contact-pieces are kept in
contact by gravity. When any person talks to the tympanum it vibrates,
and, as a result, the degree of contact between the two surfaces is
varied, resulting in a greater or less interruption of the current, the
inertia of the upper contact-piece, serving to prevent complete abrupt
“break” of the circuit, except under unusually strong vibrations. In
fact, if the speaker talks too loudly when speaking into Berliner’s
transmitter, he will cause abrupt breaks to occur instead of partial
interruptions; and a rattling noise comes in to confuse the speech
at the receiving end of the line. But this is precisely what occurs
in a Reis’s transmitter if one talks too loudly to it. It is obvious
that if Berliner’s transmitter is a “make-and-break” instrument, so
is Reis’s, because the principle of action is identical: and it is
also obvious that if Berliner’s instrument is capable of varying the
resistance at the contact-points by interrupting the current in a
manner corresponding to the pressures of the air in the sound-waves, so
also is Reis’s instrument.
[Illustration: Fig. 43.]
It is a fact that in Berliner’s instrument it is usual to make the
contact-pieces, or one of them, of hard artificial coke-carbon, as
this substance will neither fuse nor rust. But Berliner’s transmitter
will transmit speech perfectly if the contact parts be of brass,
silver, platinum, carbon, or almost any other good conductor. In most
of Reis’s instruments the contact-pieces were usually of platinum; but
they work quite as well if artificial coke-carbon is substituted. In
fact, Reis’s principle of variable and elastic contact is applicable
to contact-pieces of _any material that is a good enough conductor of
electricity_ and hard enough for the purpose. The main improvement in
Berliner’s transmitter is the substitution of the metal tympanum for
the membraneous one, which was liable to become flabby with moisture.
[Illustration: Fig. 44.]
We pass on to Blake’s transmitter, which is the one more generally
used in Great Britain than any other. The drawing, Fig. 44, of this
instrument is taken from the specifications of Blake’s British Patent,
and shews all that concerns the contact-parts. It does not show the
accessories, the induction-coil, or the form of adjusting screw and
frame peculiar to this instrument. Inspection of the figure shows that
this transmitter consists of a mouthpiece in the form of a conical
hole bored through a stout plank of wood, and closed at the back by a
metal tympanum of exactly the same size as that of Reis, behind which
the interruptor is placed, precisely as in some of Reis’s instruments.
In this interruptor both the contact-parts are supported on springs,
resembling, even in the curve given to them, the springs Reis used.
The first of the contact-pieces is a small metal spike. Concerning it
Mr. Blake remarks (page 4 of Specification):--“It is desirable that
it should be formed of, or plated with, some metal, like platinum or
nickel, which is not easily corroded. It may be attached directly to
the diaphragm, but I prefer to support it independently, as shewn, upon
a light spring.” ... “This method of supporting the electrode _ensures
its contact_ with the other electrode _under some circumstances
when otherwise they would be liable to be separated and the circuit
broken_.” In fact this spring serves functions precisely identical with
those of the springs used by Reis. The second of the contact-pieces
may be described as a mass of metal at the end of a spring. Of it
the patentee remarks:--“This weight may be of metal which may serve
directly as the electrode, but I have obtained better results by
applying to it, at the point of contact with the other electrode, a
piece of gas-coke or a hard-pressed block of carbon.” As a matter
of fact, a mass of silver or of nickel or of platinum will transmit
talking perfectly, but these metals, though better conductors, are more
liable to corrode and fuse, and may require therefore more frequent
renewal, than gas-coke. Since, then, it is immaterial to the action
of a Blake transmitter what substance is used for the contact-pieces,
it is clear that the principle of employing an interruptor mounted on
springs is the real feature of the instrument. Reis also mounted his
interrupters with springs, and for the very same purpose. The function
of the weight on the second spring of the Blake transmitter is to
resist the movement of the tympanum, and to “modify by its inertia
the variations of pressure” between the two contact-pieces. In other
words, it acts partly as Berliner’s transmitter, by inertia. So did
one of Reis’s instruments, as we have seen. In the Blake instrument
there is the happy idea of applying both the spring-principle and
the inertia-principle at once. Yet, in spite of this, if the speaker
shouts too loudly into a Blake transmitter, he will cause abrupt breaks
between the contact-pieces instead of producing partial interruptions
in the contact, and in that case speech will, as heard at the other
end of the line, be spoiled by a rattling noise. It is possible, also,
with Reis’s instruments to spoil the articulation by shouting too
loudly, and causing actual abrupt breaks in the continuity. If Blake’s
interruptor can be worked as a make-and-break in this sense, so can
Reis’s: for there is not one of the features which is essential to
Blake’s instrument that cannot be found in Reis’s also.
By way of further carrying out the comparison between Reis’s methods
of combining his tympanum with his contact-regulator, and the methods
adopted by later inventors, we give, in Fig. 45, ten comparative
sketches, the first five of which illustrate Reis’s methods. In these
sketches the only liberty taken is that of representing no more of
the instruments than the actual parts wanted in the comparison. No.
1 represents the working-parts of Reis’s first model ear, with its
curved lever, platinum-tipped spring, and adjusting screw. No. 2
shows the springs, screw, and contact-pieces of Reis’s bored-block
transmitter (“fourth form:” compare Figs 9 and 10, p. 21). No. 3 shows
the curved lever, the springs, and the adjusting screw of Reis’s eighth
transmitter (“lever” form). No. 4 gives the working parts of Reis’s
ninth transmitter, described in detail on p. 27. No. 5, in which the
tympanum is placed in a vertical position, merely for convenience of
comparison with the other figures, shows the working parts of Reis’s
final form of instrument, in which gravity and the inertia of the upper
contact-piece enabled him to dispense with the adjustment of spring
and screw. No. 6 shows in profile Berliner’s transmitter, which may
be instructively compared with No. 5. No. 7 shows the working part
of Blake’s transmitter, which should be compared with Nos. 2 and 4:
even the curve of the springs imitates that adopted by Reis. Nos.
8, 9, and 10 are forms of transmitter devised by Edison. No. 8 is
copied from Fig. 10 of the specification of Edison’s British Patent.
It will be seen that here there is an interruptor placed on each side
of the tympanum, and that each interruptor consists of a short spike
mounted on a spring and furnished with an adjusting-screw. “Platina
foil disks,” says the inventor, are to be secured to each side of the
diaphragm, and against these disks, as in Reis’s instruments, press
the contact-points of the interruptors. The patentee also states (p.
7 of his Specification), that for these contact-points “any substance
not liable to rapid decomposition” may be used. This term includes
all the substances used by Reis, and a great many others. It will
therefore be seen that this whole device is nothing more than a Reis
transmitter with the contact parts duplicated. Yet this instrument
was intended by Edison to transmit speech, and will, like Reis’s
instrument, transmit speech if properly used. No. 9 of the set of
sketches is taken from Fig. 25 of Edison’s British Specification,
but omits the induction-coil and other accessories, retaining the
parts wanted for comparison. The patentee thus describes the parts
figured. “The tension-regulator [meaning thereby the interruptor or
contact-regulator] is made of platina-foil upon the surface of two soft
rubber tubes; one on the diaphragm, the other on the adjusting-screw.”
It is interesting to note here how the ingenuity of the later inventor
led him to vary the construction adopted by the original inventor in
substituting an elastic cushion of soft rubber for the springs of the
older instruments. But the principle of combining a tympanum with a
contact-regulator, which was Reis’s fundamental notion, is here also
the leading idea; and the further idea of obviating abrupt breaks
in the current by applying elastic supports is also carried out.
Edison even copies Reis in having an adjusting-screw, and he applies
the very same substance--platinum foil--which Reis used in his very
first and his very last transmitter. Edison’s transmitter transmits
speech very fairly, even without any of such later accessories as
induction-coils; and why should it not? It is constructed on the very
lines, nay, with details almost identical with those prescribed by Reis
in describing his invention. It embodies those fundamental ideas which
Reis set before him when he said, “Taking my stand upon the preceding
principles, I have succeeded.”
[Illustration: Fig. 45.]
The last of the ten sketches of Fig. 45 is taken from Edison’s first
American Patent specification [No. 203,014, filed July 20, 1877],
and shows a duplicated interrupter with springs and adjusting-screws
combined with a tympanum. Further comment on this arrangement
is needless, save to remark that in this patent for “_speaking_
telegraphs,” Edison himself describes the contact-apparatus which Reis
termed an “interrupter,” as a “circuit-closer,” or in another place
as “circuit-breaking connections,” and, in his British Patent quoted
above, as a “tension-regulator.” It is evident that if Reis could
transmit speech by an interrupter which closed and opened the circuit
(always in proportion to the vibrations) there is no reason why Edison
seventeen years afterwards should not accomplish the same result by a
similar means. But it has lately been fashionable to deny that any such
device as an interrupter mounted on springs can transmit speech at all!
We have now compared with Reis’s transmitters several of the more
modern inventions. It would be possible to carry comparison further
were that course needed. We have not thought it worth while to rake
up Edison’s now discarded lamp-black button transmitter; and we have
not yet spoken of Crossley’s transmitter nor of Theiler’s transmitter,
nor of their parent the Hughes’ microphone, nor of dozens of other
forms. In some of these there is no specific “tympanum,” but only
a sounding-board of pine-wood, and in most of them the points of
loose-contact, where interruption more or less complete may occur, are
multiplied. But they all come back in the end to Reis’s fundamental
idea, namely that of setting the voice to vary the degree of contact
in a mechanism which he called an interruptor, and which others have
called a current-regulator (or, less correctly, a tension-regulator)
which, because the degree of contact between its parts was varied,
caused those parts to offer more or less resistance to the flow of the
current, and thereby threw it into vibrations corresponding to those of
the sound-wave impressed upon the tympanum. There is not a practical
transmitter used in any of the telephone exchanges of Great Britain
to-day that does not embody this principle.
Reis did, indeed, penetrate to the very heart the principles necessary
to be observed in a successful telephone. He was master of the
situation. For, as in every practical transmitter in use to-day, so in
his transmitter, there was _a loose contact in the circuit so arranged
that the voice could act upon it, and thereby regulate the strength of
the current_. If you eliminate this part of the apparatus,--screw up
the loose-contacts of your transmitters, so that your voices cannot
affect them,--what will your telephones be worth? No: the essential
principle of the transmitter--“Das Telephon” emphatically as its
inventor styled it--is _variable contact_; and that all-essential
principle was invented and applied for the purpose of transmitting
speech by Philipp Reis in 1861.
If this does not suffice as a claim for the invention of the Telephone
transmitter, it may well be wondered what will. We can dispense with
all other features save this one. We can even dispense with the
tympanum or diaphragm which Reis introduced, and can operate on the
contact-parts without the intervention of this part of the combination.
We can use the very metals which Reis used, and dispense with
lamp-black and all the fallacious rubbish that has been subsequently
devised about semi-conductors, whatever that term may mean. We can
even dispense with springs and adjusting screws. _But with the
principle of variable contact we can not dispense._ That which alone is
indispensable Philipp Reis discovered.
APPENDIX II.
ON THE VARIATION OF ELECTRIC RESISTANCE AT A POINT OF IMPERFECT CONTACT
IN A CIRCUIT.
Ever since electricians had experimented with voltaic currents, and
especially since the introduction of the electric telegraph, it had
been a familiar fact that a loose or imperfect contact in the circuit
caused a resistance to the flow of the current and interrupted it
more or less completely. To obviate the occurrence of loose or
imperfect contacts, binding-screws were invented; and many were the
precautions taken to make tight contacts at joints in the line, the
resistance of which it was desirable to maintain at a minimum. Young
telegraphists were particularly instructed to press their keys well
down in signalling, because a light contact would offer some resistance
which, on an increase of pressure, would disappear. In fact, it was
generally well known that the resistance of two pieces of metal or
other conducting material in contact with one another might be made
to vary by varying the goodness or badness of the contact with the
application of more or less force. This fact was known to apply to
good conductors, such as copper and other metals, and it was known
to apply also to non-metallic conductors, such as plumbago. Plumbago
points were used by Varley for the contacts of relays; it having been
found that points of platinum were liable to become fused together
with the passage of the current, and by so sticking rendered the
instrument useless. Since plumbago was known to be infusible, it was
hoped that a plumbago contact would prove more reliable. In practice,
however, the plumbago relay did not turn out so well. True it did not
fuse, or stick, or rust; but it was even more liable than platinum to
form imperfect contacts, the resistance of the light contact being so
high that a sufficient current did not pass. It is not known whether
other non-metallic substances were tried; probably not, because of
non-metallic substances plumbago is one of the few that are good
conductors.
According to Edison (British Patent, No. 792, 1882), compressed
graphite is a substance of _great conductivity_. According to Faraday
(‘Exp. Res.’ vol. i. p. 24), retort-carbon is an _excellent conductor_.
Both graphite and retort-carbon agree with the metals in the property
that the electric resistance offered at a point of contact between
them varies when the pressure at the contact is varied. It is indeed
remarkable through what wide ranges of resistance the contact between
two good conductors may vary. The resistance of contact between two
pieces of copper may be made to vary in a perfectly continuous manner
by changes of pressure through a range, according to Sir W. Thomson,
from a small fraction of one _ohm_, up to a resistance of many
thousand _ohms_. The same is true of silver, brass, and many other
good conductors, including graphite and retort-coke, though with the
latter materials the range of resistances is not so great. With partial
conductors, such as oxide of manganese, sulphide of copper, sulphide
of molybdenum, &c., and with bad conductors, such as lamp-black and
selenium, whose conductivity is millions of times less than that of
graphite, copper, and other good conductors, it is impossible to get
equally wide variations of resistance, as the amount of pressure at a
point which will bring the bad conductors into intimacy of contact,
will not turn them into good conductors. Platinum being in the category
of good conductors, is amongst those substances which yield a very
wide range of electrical resistances at the contact-points which are
submitted to varying pressures.
With the very highest conductors, such as silver and copper, the
electrical range of contact-resistance is higher than with those of
lesser conductivity, such as lead, platinum, graphite, and retort-coke.
But though the range of variation in electrical resistance at contacts
is highest for the best conductors, there comes in another element,
namely, the range of distance through which the contact-pieces, or
either of them, must be moved in order to pass through the range of
variations of resistance. This is quite a different matter, for here
the best conductors have the smallest range, and some that are not
so good a greater range. In any case the available range of motion
is very small--to be measured in minute fractions,--millionth-parts,
perhaps,--of an inch. So far as experiments go, however, silver has the
smallest range of all, then gold, then copper. Platinum and nickel have
a considerably wider range, plumbago and retort-coke a still wider one.
It is an extremely difficult matter to decide what is the precise
nature of that which goes on at a point of contact between two
conductors when the pressure at the point is altered. The principal
suggestions hitherto advanced have been that the change of resistance
observed is due:--
(_a_) To the mere changes in the amount of surface in contact.
(_b_) To a change in the resistance of the substance of the
conductor itself.
(_c_) To the formation of a minute voltaic “arc,” or electric
discharge.
(_d_) To the change in the thickness of the intervening film of
air.
(_e_) To the change in resistance of the parts in contact
consequent on the evolution of heat by the current.
It is admitted that this last suggestion, though it might account for
a difference between different substances, in so far as they differ
from one another in the effect of heat upon their specific resistance,
implies as a preliminary fact that the amount of surface in contact
shall be varied by the pressure. No convincing proof has yet been given
that the alleged layer of air or other gases has any real part to play
in the phenomena under discussion. Nor can the hypothesis, that minute
voltaic arcs are formed at the contact be regarded as either proven or
probable.
The only two theories that have really been investigated are (_a_) and
(_b_) of the above series. Of these two (_b_) is certainly false, and
(_a_) is probably, at least to a very large extent, true.
It is often said by persons imperfectly acquainted with the scientific
facts of the case, that carbon is used in telephone-transmitters,
because the resistance of that substance varies with the pressure
brought to bear upon it, whilst with metals no such effect is observed.
This statement, taken broadly, is simply false. Mr. Edison has,
indeed, laid claim to the “discovery” (_vide_ Prescott’s ‘Speaking
Telephone,’ p. 223), that “semi-conductors,” including powdered carbon
and plumbago, vary their resistance with pressure. All that Mr. Edison
did discover was that certain substances, whose properties of being
conductors of electricity had been known for years, conducted better
when the contact between them was screwed up tightly than when loose.
The experiments made to test this alleged “property” of carbon are
absolutely conclusive. The author of this book has shown[39] that when
a rod of dense artificial coke-carbon, such as is used in many forms of
telephone transmitters, such as Crossley’s for example, is subjected
to pressure varying from less than one dyne per square centimetre up
to twenty-three million times that amount, the resistance of the rod
did not decrease by so much as one per cent. of the whole. In this
case any doubt that might have been introduced by variable contact was
eliminated at the outset by taking the precaution of electro-plating
the contacts.
In 1879, Professors Naccari and Pagliani, of the University of Turin,
published an elaborate series of researches[40] on the conductivity of
graphite and of several varieties of coke-carbon, and found, even with
great changes of pressure, that the changes of electric resistance were
practically too small to be capable of being measured, and that the
only changes in resistance appreciable were due to changes of contact.
In January 1882, Mr. Herbert Tomlinson communicated to the Royal
Society[41] the results of experiments on a number of electric
conductors. The change of conductivity by the application of stress
was found to be excessively small. For carbon it was less than
one-thousandth part of one per cent. for an increase of fifteen lbs.
on the square inch in the pressure. For iron it was slightly greater,
and for lead nearly twice as great, but with all other metals less. If
this alleged property were the one on which the action of telephone
transmitters depended, then lead ought to be twice as good a substance
as graphite; whereas it is not nearly so good.
Professor W. F. Barrett, in 1879,[42] made some experiments on the
buttons of compressed lamp-black used in Edison’s transmitter, and
found that when an intimate contact was satisfactorily secured at the
beginning, “pressure makes no change in the resistance.”
In the face of all this precise evidence, it is impossible to maintain
the theory that the electric resistance of plumbago or of any other
such conductor varies under pressure. The only person who has seriously
spoken in favour of the theory is Professor T. C. Mendenhall, but in
his experiments he took no precautions against variability of contacts,
so that his conclusions are invalid.
More recently still, Mr. O. Heaviside and Mr. Shelford Bidwell have
experimented on the variations of resistance at points of contact.[43]
Mr. Heaviside’s experiments were confined to contacts between pieces of
carbon, and though extremely interesting as showing that the resistance
of such contacts are not the same, even under constant pressure, when
currents of different strength are flowing, do not throw much light on
the general question, because they leave out the parallel case of the
metals. Mr. Bidwell’s very careful researches were chiefly confined to
carbon and bismuth. The choice is unfortunate, because bismuth the
most fusible and worst conductor amongst metals (save only quicksilver)
is the one metal _least_ suited for use in a telephone transmitter. Mr.
Bidwell’s conclusions, so far as they are comparative between carbon
and “the metals,” are therefore necessarily incomplete.
Professor D. E. Hughes, whose beautiful invention, the Microphone,
attracted so much attention in 1878, has lately thrown the weight
of his opinion in favour of the view that with carbon contacts
the effect is due chiefly to an electric discharge or arc between
the loosely-contiguous parts. But Professor Hughes’s innumerable
experiments entirely upset the false doctrine that a “semi-conductor”
is necessarily required for the contact-parts. Speaking recently,[44]
he has said: “I tried everything, and everything that was a conductor
of electricity spoke.” In 1878, in a paper “On the Physical Action of
the Microphone,” Professor Hughes stated:[45] “the best results as
regards the human voice were obtained from two surfaces of solid gold.”
Hughes also found carbon impregnated with quicksilver in its pores to
increase its conducting power to work better than non-metallised carbon
of inferior conductivity. Quite lately Mr. J. Munro has constructed
successful transmitters of metal gauze, having many points of
loose-contact between them.
It seems, therefore, much the most probable in the present state
of investigations, that the electric resistance of a contact for
telephonic purposes is determined solely by the number of molecules
in contact at the surface, and by the specific conductivity of those
molecules. The element of fusibility comes in to spoil the constancy
of the surfaces in action; and hence the inadmissibility of general
conclusions with respect to all metals drawn from the behaviour of
the most fusible of them. At a mere point in contact physically with
another point, there may be hundreds or even millions of molecules
in contact with one another, all acting as so many paths for the flow
of the electric current. An extremely small motion of approach or
recession may suffice to alter very greatly the number of molecules in
contact, and the higher the specific conductivity of the substance,
and the denser its molecules, the shorter need be the actual range of
motion to bring about a given variation in the resistance offered. Just
as in a system of electric lamps in parallel arc, the resistance of
the system of lamps increases when the number of lamps through which
the current is flowing is diminished, and diminishes when the number
of lamps connecting the parallel mains is increased; so it is with the
molecules at the two surfaces of contact. Diminishing the number of
molecules in contact increases the resistance, and _vice versâ_. Each
molecule as it makes contact with a molecule of the opposite surface
diminishes, by so much relatively to the number of molecules previously
in contact, the resistance between the surfaces. Each molecule as it
breaks from contact with its opposite neighbour adds to the resistance
between the contact-surfaces. It may therefore be that the variations
of resistance which are observed at contacts between all conductors,
from the best to the worst, are all made up, though they _appear_ to
pass through gradual and continuous changes, of innumerable minute
makes-and-breaks of molecular contact. The very minuteness of each
molecular make-or-break, and the immense number that actually must
occur at every physical “point” of contact, explain why the effect
seems to us continuous. We owe, moreover, to Mr. Edison[46] the
experimental proof that actual abrupt makes-and-breaks of contact _can_
produce an undulating current when they recur very rapidly. Whether the
heating action of the current itself may not also operate in changing
the conductivity of the molecules which happen at the moment to be in
contact is another matter. It may be so; but if this should hereafter
be demonstrated, it will but confirm the contact-theory of these
actions as a whole.
Assuming, then, broadly, that the observed resistance at a point of
contact is due to the number of molecules in contact and to their
individual resistances, it is evident that the property of varying
resistance at contact ought to be most evident, _ceteris paribus_,
in those substances which are the best conductors of electricity.
Unfortunately, the _cetera_ are not _paria_, for the question of
fusibility comes in to spoil the comparison; and carbon, which has less
fusibility than the metals, is commonly credited with giving a better
result than any. This common opinion is, however, based on comparisons
made without taking into consideration the question of range of motion
between the parts in contact, and without taking into consideration the
point that whilst some forms of carbon are excellent conductors, others
do not conduct at all. In a telephonic transmitter so arranged that
the actual range of motion shall be very small, the metals are just as
good as carbon--some of them better. I have heard from a transmitter
with contacts of pure bright silver better articulation than with
any carbon transmitter. And this is exactly what theory would lead
one to expect. As to the suggestion that plumbago makes a successful
transmitter, because it is a “semi-conductor”--whatever that term may
mean[47]--it is one of those suggestions which are peculiarly fitted
to catch the unscientific mind as affording an easy explanation for an
obscure fact; unfortunately, like a good many other similarly catching
suggestions, _it is not true_. The very best conductor--_silver_--will
serve to transmit articulate speech: and so will the one of the very
worst conductors--_lamp-black_! So much for this fallacious doctrine of
semi-conductors!
Reis used for his contact-points substances which, by reason of
their non-liability to fuse or oxidize, were customary in electrical
apparatus, and chiefly platinum. In his earliest transmitter (model
ear), and in his last, platinum was used. In his lever-form of
transmitter, so minutely described by von Legat, the material is not
specified. The lever-shaped contact-piece was to be a conductor, and
as light as possible, and since all metallic parts are particularly
described as metallic, whilst this is not so described, the obvious
inference is that this was non-metallic. The number of light,
non-metallic conductors is so few that the description practically
limits choice to some form of hard carbon. No other materials are
named by Reis, but Pisko says (p. 103) that brass, steel, or iron
might be used for contacts. Any one of these materials is quite
competent, when made up into properly-adjusted contact-points, to vary
the resistance of a circuit by opening and closing it in proportion
to the vibrations imparted to the contact-points. That is what
Reis’s transmitter was intended to do, and did. That is what all the
modern transmitters--Blake’s, Berliner’s, Crossley’s, Gower-Bell’s,
Theiler’s, Johnson’s, Hunning’s do, even including Edison’s now
obsolete lamp-black button transmitter. Mr. Shelford Bidwell has very
well summarized the action of the current-regulator in the following
words: “The varying pressure produces alterations in the resistance at
the points of contact in exact correspondence with the phases of the
sound-waves, and the strength of a current passing through the system
is thus regulated in such a manner as to fit it for reproducing the
original sound in a telephone.”
Reis constructed an apparatus consisting of a tympanum in combination
with a current-contact-regulator, or “interruptor,” which worked
on this principle of variable contact, and he called it “The
Telephone” (see pp. 57, 85). The very same apparatus we now-a-days
call a “Telephone-transmitter,” or simply a “transmitter.” It is
curious to note that Reis seems to have regarded his receiver or
“reproducing-apparatus” as no new thing. He says explicitly (p. 56)
that his receiver might be replaced by “any apparatus that produces
the well-known galvanic tones.” “_The_ Telephone” was with Reis
emphatically the _transmitter_. Bell in 1876 invented an instrument
which would act either as transmitter or receiver, and which, though
never now used as transmitter, is still called “a Telephone.” Edison’s
“sound-telegraph,” or “telegraphic apparatus operated by sound,” was
patented in 1877. In his specification _he never called his transmitter
a “telephone_;” that name he reserved exclusively for his receiver.
He found it, however, convenient a year later to rechristen his
transmitter as the “_carbon telephone_,” though throughout the whole
of his specification _neither “carbon” nor “telephone” are mentioned_
in connection with the transmitter! Within that year Hughes had
brought out another instrument--“The Microphone”--which, like Reis’s
instrument, embodied the principle of variable contact. Hughes’s
instrument, usually constructed with contacts made of loose bits of
coke-carbon, was simply a Reis’s Telephone minus the circular tympanum;
and the really important new fact it revealed, was that very minute
vibrations, such as those produced by the movements of an insect,
when transmitted immediately through the wooden supports, sufficed to
vary the resistance of a telephonic circuit, though far too slight in
themselves to affect it if they had to be first communicated to the air
and then collected by a tympanum. Put a specific tympanum to a Hughes’s
microphone, and you get a Reis’s telephone. Take away the tympanum from
a Reis’s telephone, and you get a Hughes’s microphone. Hughes is not
limited to one material, nor is Reis. But the fundamental principle of
the electrical part of each is identical. The Blake transmitter (Fig.
44), and the Berliner transmitter, and also Lüdtge’s microphone,[48]
which was even earlier than that of Hughes, are all embodiments of the
same fundamental principle of variable contact which Reis embodied in
his “Telephone.”
The numerous experiments which Reis made, and the many forms of
instruments which he devised, prove his conviction of the importance of
his invention to have been very deeply rooted. He had indeed penetrated
to the very soul of the matter. He did not confine himself to one
kind of tympanum, he tried many, now of bladder, now of collodion,
now of isinglass, and now of thin metal. He varied the forms of his
instruments in many ways, introducing the element of elasticity by
springs and adjusting-screws. Though he chiefly employed one metal for
his contact-pieces, he did not limit himself to that one, but left
us to infer that the principle of variable contact was applicable to
any good conductor, metallic or non-metallic. He knew better, indeed,
than to limit himself in any such fashion; better, indeed, than some
of the eminent persons who are now so willing to ignore his claims.
Modern practice has taught us to improve the tympanum part of Reis’s
invention, and to obviate the inconveniences to which a membrane is
liable: in that part we have gone beyond Reis. But in the question of
contact-points for opening and closing the circuit in correspondence
with the vibrations, we are only beginning to find how much Reis was
a-head of us. We have been thrown off the track--blinded perhaps--by
the false trail of the “semi-conductor” fallacy, or by the arbitrary
and unnatural twist that has been given by telegraphists to Reis’s
expression, “opening and closing the circuit,” forgetting that he
practically told us that this operation was to be proportional to, “in
correspondence with,” the undulations of the tympanum. When we succeed
in freeing ourselves from the dominance of these later ideas, we shall
see how much we still have to learn from Philipp Reis, and how fully
and completely he had grasped the problem of the Telephone.
FOOTNOTES:
[39] ‘Philosophical Magazine,’ April 1882.
[40] ‘Atti del R. Istituto Veneto di Scienze,’ vol. vi. ser. 5.
[41] Proc. Roy. Soc. No. 218, 1882.
[42] See Proc. Roy. Dubl. Soc. Feb. 17, 1879.
[43] Vide ‘The Electrician,’ Feb. 10, 1883.
[44] Journal Soc. Telegr. Engin. and Electricians, vol. xii. p. 137.
[45] Proc. Physical Soc. vol. ii. p. 259, 1878.
[46] ‘Journal Soc. Telegraphic Engineers,’ vol. iv. p. 117, 1874.
[47] The term “semi-conductor” is very rarely used by electricians, who
prefer the term “partial conductor” as being more correct. Moreover,
electricians, from Faraday downwards, are practically agreed in calling
plumbago a good conductor, and worthy of being classified by reason of
its high conductivity along with the metals. The substances known as
“semi-conductors” are those given in Ferguson’s ‘Electricity,’ p. 49
(edition of 1873), namely, alcohol, ether, dry-wood, marble, paper,
straw, and ice. Mascart and other eminent authorities agree in this
classification. It would tax even Mr. Edison’s unrivalled ingenuity to
make of these materials a transmitter that should alter its resistance
by pressure!
[48] Lüdtge’s German Patent, dated Jan. 12, 1878, describes a “Universal
Telephone” in which a tympanum was applied to convey vibrations to an
interruptor made of hard coke-carbon.
APPENDIX III.
COMPARISON OF REIS’S RECEIVERS WITH RECENT INSTRUMENTS.
The receivers invented by Reis for the purpose of reconverting into
audible mechanical vibrations the varying electric currents transmitted
from the speaking end of the line were of two classes, viz.:
(1.) Those in which the magnetic expansion and contraction of a rod
of steel or iron, under the influence of the varying current, set up
mechanical vibrations and communicated them to a sound-board.
(2.) Those in which the current by passing round the coils of an
electro-magnet caused the latter to vary the force with which it
attracted its armature, and threw the latter into corresponding
mechanical vibrations.
The first of these principles is embodied in the “knitting-needle”
receiver described above and depicted in figures 22 & 23 on page 33.
This receiver differs wholly from the later instruments of Bell, and
others, and depended for its action upon the phenomenon of magnetic
expansion discovered by Page and investigated by Joule. It was well
known before Reis’s time that when a needle or bar of iron was
magnetised it grew longer, and when demagnetised it grew shorter.
Page detected the fact by the “tick” emitted by the bar during the
act of magnetisation or demagnetisation. Joule measured the amount
of expansion and contraction. To these discoveries Reis added two
new facts; _first_, that if the degree of magnetisation be varied
with rapid fluctuations corresponding to those of the sound waves
impressed on the transmitter, the expansion and contraction of the
rod followed these fluctuations faithfully, and therefore emitted at
the receiving end sounds similar to those uttered at the transmitter.
_Secondly_, by employing a needle of _steel_ instead of the bar of
iron used by Page, Reis obtained an instrument which once used could
never become completely demagnetised on the cessation of the current;
it was thenceforth a _permanent magnet_, and all that the fluctuating
currents could do was to vary its degree of magnetisation. Reis
carefully explained in his memoir “On Telephony,” how the frequency of
such fluctuations in the magnetising current could act in reproducing
the pitch, and further, how the amplitude of the fluctuations set
up vibrations of corresponding amplitude in the rod: he added with
significance, that the quality of the reproduced note depended upon
a number of variations of amplitude occurring in a given time. His
theory of these actions was that the atoms (or perhaps our modern
word _molecules_ would more correctly represent what Reis spoke of as
atoms) of the rod or needle were pushed asunder from one another in
the act of magnetisation, and that on the cessation of the magnetising
influence of the current, these same atoms strove to return to their
previous position of equilibrium, and thus the oscillations of the
atoms led to the vibration of the needle as a whole. Whether all Reis’s
speculations as to the behaviour of the atoms under varying degrees of
magnetising force are justified in the present aspect of science or
not, is, however, not of any great importance; the important point is,
that, whether his theory be right or wrong, the instrument he devised
will perform the function he assigned to it: it will reproduce speech,
not loudly, but in reality far more articulately than many of the
telephonic receivers in use under the names of Bell, Gower-Bell, &c.
One very curious point in connection with this “knitting-needle”
receiver of Reis, is its extremely bad acoustical arrangements. It
was laid horizontally upon a small sounding-box covered by a lid. If
the _end_ of the needle had been made to press on the resonant-board
(as indeed appears to have been done at first with the violin, p. 29)
the vibrations would have been much more directly reinforced. But
when merely supported by two wooden bridges the direct communication
was largely lost. The pressure of the lid downwards upon the spiral,
as recommended by Reis, is no doubt an important matter acoustically.
It is strange that a man who had grappled in so masterly a way with
the acoustical problem of the transmitter, and had solved it by
constructing that transmitter on the lines of the human ear, should not
have followed out to the same extent those very same principles in the
construction of his receiver. An extended surface he did employ, in
the shape of a sounding-board; but it was not applied in the very best
manner in this instrument.
The second principle applied by Reis in the construction of his
telephone-receivers, was that of the electro-magnet. He arranged an
electro-magnet so that the fluctuating currents passing round the coils
set up corresponding variations in the degree of force with which it
attracted its armature of iron, and so forced the latter to execute
corresponding mechanical vibrations. This principle is common both to
the receiver of Reis, and to the later receivers of Yeates, Bell, and
Edison. Reis’s armature was an iron bar of oval section; Yeates’s an
iron strip screwed to a sound-board, Bell’s was an iron plate, and
Edison’s an iron plate also.
For the better comparison of Reis’s electro-magnetic receiver with
those of more modern date, we here present in Fig. 46 a comparative
view of a number of different forms of receiver in which Reis’s
principle of causing an electro-magnet to set up vibrations in an
armature is applied. In this set of figures, _A_ and _B_ are the
suggested forms mentioned in the letter of Mr. Horkheimer, p. 119,
and show an electro-magnet, opposite the poles of which is placed an
armature (a bar) which must be of iron or other metal capable of having
magnetism induced in it, and which, by reason of its attachment to an
elastic spring, is capable of being made to oscillate to and fro when
attracted with a varying force. Reis clearly recognised the necessity
of further providing a sufficient resounding surface by means of
which the surrounding air could be set in motion: for in the case of
these two suggestions the electro-magnet and its elastically-mounted
armature were placed within a cigar box. _C_ is a plan of the receiving
instrument previously described and figured in Plate II. and in figures
21 and 34 on pages 32 and 109. In this instrument the electro-magnet
was horizontal, the armature, a bar of iron of oval section (which in
the original drawing in plate II. appears to have been in reality a
hollow bar or tube) attached to a thin lever described as a plank,
pivoted like a pendulum to an upright support, but prevented by a
set-screw and a controlling spring from vibrating in the manner
of a pendulum. Such an arrangement, in fact, vibrates in perfect
correspondence with any vibrations that may be forced upon it by the
electro-magnet. The broad flat surface of the lever--he specially
directed that it should be broad and light--transfers the vibrations
to the air, and is aided by the surface of the sounding-board on which
the apparatus stands. This apparatus has, therefore, all the elements
of a successful receiver, except only that its shape renders it
inconvenient for portability. But by reason, firstly of its armature
of iron, secondly of the elastic mounting of that armature, thirdly of
the extended surface presented, it is admirably adapted to serve as an
instrument for reproducing speech.
[Illustration: Fig. 46.]
Fig. 46 _D_ represents the excellent electro-magnetic receiver devised
in 1865 by Yeates (compare Fig. 42, p. 128) to work with the Reis
transmitter, and is in many respects identical with the preceding form.
The armature, a strip of iron, was attached at one end by a very stiff
steel spring to a pine-wood sounding-board over a hollow box, from the
base of which rose the metal pillar which supported the electro-magnet.
This receiver also contains all the elements of a successful receiver,
the armature being of a material capable of inductive action, and
elastically supported; whilst the sound-box provided adequate surface
to communicate the vibrations to the air.
We now come to the more modern instruments of Gray, Bell, and
Edison. So far the receivers of Reis and of Yeates were intended for
reproducing any sound; but now for the first time, ten years after the
date of these early telephonic receivers, we meet with instruments
devised with the express purpose of receiving only certain selected
tones.
For the purposes of multiple acoustic telegraphy, that is to say for
the purpose of signalling the “dots” and “dashes” of the Morse code
in a number of different fixed musical notes, each of which is to
be signalled out and repeated by a receiver adapted to vibrate in
that note alone, it is clear that the instruments of Reis, adapted
as they were to transmit and receive _any_ sound that a human ear
can hear, would not answer. Accordingly those experimenters, who
from about the year 1873 to the year 1870, applied themselves to
multiple telegraphy--foremost amongst them being Mr. Elisha Gray and
Prof. Graham Bell--dropped the use of the tympanum in the transmitter
and devised new transmitters and new receivers, in most of which
the ruling idea was that of employing a vibrating tongue or reed,
tuned up to one particular note. Now it is obvious that a receiver
which, like those of Reis, is adapted to receive _any_ tone, can
also receive a musical note. But for the operation of “selective”
reception, a receiver must be employed, not only tuned to one note,
but tuned to the very note emitted by the particular transmitter
with which it is to be in correspondence. Elisha Gray found this out
very early in his researches. In the winter of 1873-4[49] he was
transmitting musical tones by a sort of tuning-fork interruptor, and
received them on an instrument shown in Fig. 46 E, which represents
a form of electro-magnet mounted for the purpose. It was “a common
electro-magnet, having a bar of iron rigidly fixed at one pole,
which extends across the other pole, but does not touch it by about
one sixty-fourth part of an inch. In the middle of this armature a
short post is fastened, and the whole is mounted on a box made of
thin pine, with openings for acoustic effects.” It was, in fact,
very similar to Yeates’s receiver just described, and Gray found it
capable of receiving not only simple musical tones but composite tones,
and even harmonies and discords. In fact, like Reis’s and Yeates’s
receivers, it could receive anything that the transmitter sent to
it, even including speech. Now this did not suit Gray, who wished to
have selective receivers, one to take up note A, another note C, &c.
Accordingly in 1870 we find Gray taking out a fresh patent[50] for
selective receivers, which he also called harmonic analysers, each
of which consisted of “a tuned bar or reed suitably attached to an
electro-magnet, and the whole mounted upon a resonant box.” Fig. 46 _F_
is reproduced from Gray’s British patent. “A vibrating tongue reed,
or bar” of steel “is united with one pole of the magnet. The free end
of the reed passes close to, but does not touch the other pole of the
magnet.” Gray further says that the reed is made with parallel sides
and tuned by cutting it away at one point, as this mode prevents false
nodal vibrations from occurring.
Selective receivers for multiple telegraphy were also invented by
Graham Bell. The form shown in Fig. 46 _I_ is transcribed from Fig. 15
of Bell’s Specification to his British Patent, No. 4765, of the year
1876 (dated 9th December), which the inventor thus describes: “It is
preferable to employ for this purpose an electro-magnet _E_, Fig. 15,
having a coil upon only one of its legs. A steel spring armature _A_ is
firmly clamped by one extremity to the uncovered leg _h_ of the magnet,
and its free end is allowed to project above the pole of the covered
leg.” In fact the arrangement was almost identical with, but not quite
as good mechanically as that patented seven months previously by Gray.
The inventor further said that a number of these instruments might be
placed on one circuit, and that if one of them were set in vibration,
only those would respond which were in unison with its note; and
further that “the duration of the sound may be used to indicate the dot
or dash of the Morse alphabet, and thus a telegraphic despatch may be
indicated by alternately interrupting and renewing the sound.”
Anything more totally different from Reis’s telephone than these
selective harmonic telegraphs with their tuned tongues can hardly be
imagined. Reis was not aiming at selective harmonic telegraphy; he
wanted his one instrument to transmit every sound that a human ear
could hear. He did not dream of using a tuned bar or reed; his typical
structure was the tympanum of the ear. In fact, as we have seen above,
the tuned reed or tongue was introduced into telegraphy for the
purpose of transmitting single selected notes to the exclusion of all
others.
Strange though it may seem, a tongue receiver like those of Graham
Bell and of Gray just described can be used for receiving speech!
It is true, as Gray remarks, that a thick bar of steel, cut away as
described, is best adapted for its own tone only. But Bell’s thin
steel tongue, though it has its own fundamental note (and so has every
tympanum, for that matter) when left free to vibrate in its own time,
will reproduce _any_ other note or sound that may be _forced_ upon it
by the varying attraction of the electro-magnet. There is, indeed, the
whole difference between “free” and “forced” vibrations. One of the
strangest delusions that has somehow grown up in recent telephonic
discussions is the almost incredible proposition that a tongue cannot
talk because it is a tongue. It would be equally veracious to affirm
that an ear (_i.e._ a tympanum) cannot hear because it is an ear.
But leaving harmonic telegraphy and its “tuned bars,” both Gray and
Bell applied themselves to the old problem of transmitting human
speech. What was their very first step? They threw away their “tuned
bars” and “steel springs,” and returned _to the tympanum_! Elisha Gray
devised the receiver shown in Fig. 46, _G_, taken from his caveat of
date February 14, 1876.[51] In that document Gray says: “My present
belief is that the most effective method of providing an apparatus
capable of responding to the various tones of the human voice, is
a _tympanum_, drum, or diaphragm,” stretched across one end of a
chamber. He adds that in the receiver there is (see Fig. 46, _G_) an
electro-magnet, acting upon a diaphragm to which is attached a piece of
soft iron, and which diaphragm is stretched across a vocalising chamber.
Graham Bell’s receiver (the American specification of which was
filed the same day as Gray’s caveat) is shown (in the form patented
in Great Britain, Dec. 9, 1876) in Fig. 46 _H_, which is taken from
Fig. 19 of Bell’s British patent. “The armature,” says the inventor,
“is fastened loosely by one extremity to the uncovered leg, _h_, of
the electro-magnet _E_, and its other extremity is attached to the
centre of a stretched membrane.” The armature, in fact, was capable of
vibrating like a pendulum on its pivot, but was elastically restrained
by its attachment to the tympanum; the armature would therefore vibrate
in perfect correspondence with any vibrations forced upon it by the
electro-magnet. This instrument as also that of Gray, was admirably
adapted to receive speech, for it embodied the three essential points
which Reis had already discovered: viz., firstly, that the armature
must be of iron, or capable of being acted upon by magnetic induction;
secondly, that it must be elastically mounted; thirdly, that it
should present an extended surface. Bell’s form of receiver had the
advantage over Reis’s (compare p. 158), that its extended surface was
a true tympanum of membrane, and not a mere broad thin plank. Being a
tympanum, it therefore realised Reis’s fundamental notion of imitating
the human ear more fully than even Reis’s own receiver did.
Figures 46, _J_, _K_, and _L_ represent the more recent types of
receiver of Bell and Edison. Fig. 46 _J_ is reproduced from Fig. 20
of Bell’s British Patent, and shows the substitution of a thin steel
plate, attached to a frame, in front of the electro-magnet, for the
membrane and iron armature. This form of instrument also embodies
Reis’s three principles--but with this improvement, the armature
capable of inductive action, the elastic mounting, and the extended
surface, are here all united in one organ, the thin flexible tympanum
of steel. Apart from this unification of parts there is absolutely
nothing in this form of Bell’s receiver, that Reis did not invent
fourteen years before. Bell’s great and most signal improvement was not
this beautiful mechanical modification of the Reis receiver, but lay in
the entirely new suggestion to use such a receiver _as a transmitter_
to work by magneto-electric induction. Two of Reis’s receivers (Fig.
21) if coupled up with a battery will talk together as transmitter
and receiver: but Reis did not know and never suggested this. Two of
Yeates’s receivers (Fig. 42) if coupled up with a battery will talk
together as transmitter and receiver; but Yeates did not know and
never suggested this. Bell did discover this, and thereby invented a
transmitter which, though now abandoned as a transmitter, for want of
loudness, was more reliable than the anterior transmitters of Reis
had been. He made another discovery, presently to be alluded to--that
of putting a permanent magnet into the transmitter, to enable him to
dispense with the battery; but beyond this and the other mechanical
simplifications previously mentioned, all that he discovered may be
summed up by saying that he found out that a receiver constructed on
Reis’s principles could work as a transmitter also. That was Bell’s
really great and important discovery which took all the world by storm
at the Centennial Exhibition of 1876.
Bell subsequently added to his claims the substitution of a permanent
magnet with an iron pole-piece, in place of the simple electro-magnet,
thus enabling him to transmit his fluctuating currents without the
trouble of using a battery, and the Bell transmitter, thus modified,
is used to this day as a receiver, Reis had in his “knitting-needle”
telephone, employed a permanent magnet of steel to serve as a receiver,
he had not, however, applied it as Bell did to attract a plate of thin
steel.
Fig. 46, _K_, exhibits a form of electro-magnetic receiver described
in Edison’s British Specification, No. 2909, 1877, Fig. 24. This
instrument, though patented seven months after Bell’s instrument,
differs from it in no point of importance. Its armature was a thin
plate of iron, elastic, and having an extended surface; being, in fact,
a tympanum.
No one can examine the set of receiving instruments collected in Fig.
46 without being struck with the extraordinary similarity of design
which pervades the entire series. In every one of the set there is an
electro-magnet, the function of which is to set an armature[52] into
vibration by attracting it with a variable force. In every one the
armature is of a material capable of magnetic induction; that is to
say, iron, steel, or equivalent material. In every one of them the
armature is either elastically mounted, or is in itself elastic. In
every one of them (save only the two quite recent forms, _F_ and _I_,
which were intended not to speak, but to emit only one fixed musical
note) there is an extended surface (either a sound-board or a tympanum)
to communicate the vibrations to the air. Lastly, every one of these
forms, when connected with the line through which the telephonic
currents are being transmitted, is perfectly capable of reproducing
articulate speech. But the inventor who had the genius to discover all
these essential points, and to combine them in an instrument, and to
use it to reproduce articulate speech, is surely the true inventor of
the system. The inventor of the system embodying these essential points
was Philipp Reis.
FOOTNOTES:
[49] See Prescott’s ‘Speaking Telephone,’ p. 158.
[50] ‘British Patent,’ No. 1874, of the year 1876 (dated 4th May).
[51] Prescott, ‘Speaking Telephone,’ p. 203.
[52] Yet Bell’s claim (British Patent Specification) runs: “I claim
the production of any given sound or sounds from the _armature_ of the
receiving instrument.”
APPENDIX IV.
ON THE DOCTRINE OF UNDULATORY CURRENTS.
“_In this Specification the three words ‘oscillation,’
‘vibration’ and ‘undulation,’ are used synonymously._”--Graham
Bell, U.S. Patent, No. 174,465, filed Feb. 14, 1876.
In the preceding appendices it has been demonstrated that all that
is essential in both transmitter and receiver of a Telephonic system
was to be found existing in 1863 in the Telephone of Reis. There
yet remains to be met the _doctrinaire_ objection that as Reis
never explicitly mentions an undulatory current as distinguished
from an intermittent one, he never intended to use such a current.
This objection is advanced only by those persons who have committed
themselves to the idea that speech cannot be transmitted by a
transmitter which opens and closes the circuit.
It is certain that Reis did not in any of his writings explicitly
name an undulatory current: but it is equally certain that, whether
he mentioned it or not, he both used one and intended to use one. He
did not concern himself as to the precise manner in which the current
fluctuated provided only he attained the end in view--namely, that
the vibrations of the armature of the receiver should be similar to
those of the transmitter. This he did lay down with great clearness
and emphasis as his guiding principle; and he cared not about the
intermediate question as to how the current did the work. He told the
world that the electromagnet at the receiving end must be magnetised
and demagnetised correspondingly with the vibrations imparted by the
air to the tympanum of his transmitter, in order that the armature
might be set into vibrations similar to those of the speaker’s
voice. If the tympanum of the transmitter vibrated or oscillated or
undulated--the terms are synonymous--so must the armature of the
receiver. Graham Bell has told us precisely the same thing: “The
current traversing the coils of the electromagnet _E_ occasions an
increase and diminution in its intensity” [that is to say, magnetises
and demagnetises it], “and the armature _A_^1 is thrown into vibration”
... “and thus imparts to the air at _n_^1 a facsimile copy of the
motion of the air that acted upon the membrane _n_.” Bell agrees then
absolutely in every detail with what Reis said on this point. That
sound-waves should be transmitted by a Telephone requires indeed a
process of several stages. (1.) The sound-waves must strike upon the
tympanum of the transmitter and make it undulate, or, oscillate, or
vibrate--whichever term you please--in a corresponding manner. (2.)
The undulating tympanum must act upon the circuit, and either itself
induce undulating or vibrating currents (Bell’s plan, by magnetic
induction), or else throw a current already flowing there, into
undulations, or vibrations, or oscillations (Reis’s plan, by varying
contact-resistance), but in either case these undulations of the
current must correspond to the original undulations of the air-waves.
(3.) The undulating, or vibrating, or oscillating current must run
round the coils of the electromagnet and cause its magnetic force
to undulate, or oscillate, or vibrate by demagnetising it and then
magnetising it, but this also must be in a manner corresponding to the
original undulations. (4.) Further, the armature of the receiver must
be set into undulations, or vibrations, or oscillations corresponding
to those of the force of the electromagnet, and therefore to the
undulations of the current that is magnetising and demagnetising it,
and therefore identically corresponding with the original undulations
of the sound-waves. (5.) The armature must communicate its vibrations
to the air and to the ear of the listener. Of these successive stages
Reis explicitly told the world that his instrument was to do the
first one and the last three, and he several times emphasized the
statement, that the final undulations of the last stage were to be
similar to the original undulations of the first stage. The air at the
listening end, the armature of the receiver, and the magnetism of the
magnet, were all to be set by the fluctuations of the current into
undulations corresponding with those of the tympanum at the speaker’s
end, and of the waves of his voice. It is perfectly clear therefore,
that he regarded as self-evident the intermediate stage, and he did not
dwell upon the necessity of the point, that his transmitting-current
must also vibrate, because this was obviously so, and was only an
intermediate matter of secondary moment. He chose rather to point out
the necessity of unification between the first and last stages, leaving
it to common sense to see that the “interruption” or the “opening and
closing” of the circuit must be effected in a manner corresponding to
the undulations of the impressed sound-wave. Had the “interruptions”
not been of the nature of corresponding variations of contact, the
current could not have been set into corresponding vibrations, and the
armature of the electromagnet could not have reproduced the vibrations
of the transmitter. Clearly Reis’s whole conception of telephony
included as a minor and intermediate step the fact that the current
was, by the action of the transmitter, caused to vary in strength in
correspondence with the undulations of the tympanum--that, in fact,
it was made to undulate by the action of the tympanum and of the
interruptor which opened and closed the circuit in obedience to the
undulations of the tympanum and in proportion to them.