attention, is an instrument which not only registers the different
vibrations produced by speech on a vibrating plate, but reproduces the
same words in correspondence with the traces registered. The first
function of this instrument is not the result of a new discovery.
Physicists have long sought to solve the problem of registering
speech, and in 1856 Mr. Leo Scott invented an instrument well known to
physicists under the name of Phonautograph, which completely solved
the difficulty: this instrument is described in all the more detailed
treatises on physics. But the second function of the Edison instrument
was not realised nor even mentioned by Mr. Scott, and we are surprised
that this able inventor should have regarded Mr. Edison’s invention as
an injurious act of spoliation. We regret on his own account, since no
one has wished to deprive him of the credit he deserves, that he should
have published a pamphlet on the subject, couched in terms of such
asperity, which proves nothing, and only states facts which were well
known to all physicists. If any other person could claim the invention
of the phonograph, at least in its most curious property of reproducing
speech, it would certainly be M. Charles Cros; for in a sealed paper
deposited at the Académie des Sciences, April 30, 1877, he pointed
out the principle of an instrument by means of which speech might be
reproduced in accordance with the marks traced on a register like that
of the phonautograph.[19] Mr. Edison’s patent, in which the principle
of the phonograph is first indicated, is dated July 31, 1877, and he
was still only occupied with the repetition of the Morse signals. In
this patent Mr. Edison described a mode of registering these signals by
means of indentations traced with a stylus on a sheet of paper wound
round a cylinder, and this cylinder had a spiral groove cut on its
surface. The tracings thus produced were to be used for the automatic
transmission of the same message, by passing it again under a stylus
which should react on a current breaker. In this patent, therefore,
nothing is said of the registration of speech or of its reproduction;
but, as the ‘Telegraphic Journal’ of May 1, 1878, observes, the
foregoing invention gave him the means of solving this double problem
as soon as it was suggested to him. If we may believe the American
journals, this suggestion soon came, and it was the result of an
accident.
In the course of some experiments Mr. Edison was making with the
telephone, a stylus attached to the diaphragm pierced his finger at
the moment when the diaphragm began to vibrate under the influence of
the voice, and the prick was enough to draw blood. It then occurred
to him that if the vibrations of the diaphragm enabled the stylus to
pierce the skin, they might produce on a flexible surface such distinct
outlines as to represent all the undulations produced by the voice, and
even that the same outlines might mechanically reproduce the vibrations
which had caused them, by reacting on a plate capable of vibrating in
the same way as that which he had already used for the reproduction
of the Morse signals. From that moment the phonograph was discovered,
since there was only a step between the idea and its realisation, and
in less than two days the instrument was made and tried.
This is an ingenious story, yet we would rather believe that the
discovery was made in a more serious spirit. In fact, such an inventor
as Mr. Edison, who had discovered the electro-motograph, and had
applied it to the telephone, was already on the way to discover the
phonograph, and we think too well of his powers to attach much credit
to this American romance. Besides, Mr. Edison was well acquainted with
Mr. Scott’s phonautograph.
Mr. Edison’s phonograph was only patented in January 1877.
Consequently, when we look at the principle of the invention, M. Cros
undoubtedly may claim priority; but it is a question whether the
system described in his sealed paper, and published in the _Semaine
du Clergé_, October 8, 1877, would have been capable of reproducing
speech. Our doubt seems justified by the unsuccessful attempts of the
Abbé Leblanc to carry out M. Cros’ idea. When we have to do with such
undulating and complex vibrations as those involved in the reproduction
of articulate words, it is necessary that the stereotyping should in
some sense be effected by the words themselves, and their artificial
reproduction will necessarily fail to mark the slight differences
which distinguish the delicate combinations of speech. Besides, the
movements performed by a point confined to a groove that follows a
sinusoidal curve cannot be effected with all the freedom necessary for
the development of sounds, and the friction exerted on the two edges of
the groove will often be of a nature to stifle them. A distinguished
member of the Société de Physique, when I exhibited the phonograph to
that society, justly said that Mr. Edison’s whole invention consisted
in the thin metallic sheet on which the vibrations are inscribed; this
sheet permits the movements of the vibrating plate to be directly
stereotyped, and thereby the problem is solved. It was necessary to
find such an expedient, and it was done by Mr. Edison, who is therefore
the inventor of the phonograph.
After M. Cros, and before Mr. Edison, MM. Napoli and Marcel Deprez
attempted to make a phonograph, but with so little success that they
believed at one time the problem to be insoluble, and threw doubts
on Mr. Edison’s invention when it was announced to the Société de
Physique. They subsequently resumed their labours, and lead us to
hope that they may eventually produce a phonograph of more perfect
construction than that of Mr. Edison. We shall have more to say on this
subject.
In conclusion, the mechanical reproduction of speech was first effected
by Mr. Edison, and in so doing he has accomplished one of the most
curious and important discoveries of our time, since it has shown that
this reproduction was much less complicated than had been supposed. Yet
the theoretical consequences of the discovery must not be exaggerated,
since I do not consider it by any means proved that our theories on the
voice are incorrect. There is in fact a great difference between the
reproduction of a sound which has been uttered, and the mode in which
the same sound was produced. The reproduction may be easily effected,
as M. Bourseul has remarked, as soon as a mode has been discovered of
transmitting the vibrations of air, however complex they may be; but in
order to produce the complex vibrations of speech by the voice, several
special organs must be exercised--first, the muscles of the throat;
secondly, the tongue, the lips, and even the teeth--and for this reason
an articulating machine is necessarily very complex.
Surprise was expressed that the speaking machine, which was brought
from America two years ago, and exhibited at the Grand Hôtel, Paris,
was so extremely complicated, since the phonograph solved the problem
in such a simple way. This is because the latter instrument only
reproduces speech, while the former utters it, and the inventor of
the speaking machine had to employ in his mechanism all the organs
which are necessary in our organism for the reproduction of speech.
The problem was infinitely more complex, and this invention has
not attracted all the attention it deserved. We shall speak of it
presently. We must now describe the phonograph and the different
applications which have been, or which may be, made of it.
_Description of Phonograph, and mode of using it._--The first and best
known model of this instrument, which we represent in fig. 66, simply
consists of a registering cylinder R, set in motion with the hand by
a winch M, before which a vibrating plate is placed, furnished on its
face with a telephone mouthpiece E, and on the reverse side with a
tracing point. This tracing point, which is seen at _s_ in the section
of the instrument given in fig. 68, is not fixed directly on the plate;
it rests on a spring _r_, and a caoutchouc pad _c_ is placed between
it and the vibrating disk. This pad is formed of the end of a tube
which is designed to send the vibrations of the plate to the point _s_
without stifling them. Another pad _a_, placed between the plate L L
and the rigid support of the point, moderates in some degree these
vibrations, which, without this precaution, would generally be too
powerful.
[Illustration: FIG. 66.]
The cylinder, of which the axis A A (fig. 66) is cut at one end
like a screw, to enable it to make a lateral progressive movement
simultaneously with the rotatory movement effected on itself, has on
its surface a narrow screw-thread coinciding with that of the axis, and
when the tracing point is inserted, it is able to pass along it for a
distance corresponding to the time occupied in turning the cylinder.
A sheet of tinfoil or of very thin copper is carefully applied to the
surface of the cylinder, and it should be slightly pressed down upon
it, so as to show a faint tracing of the groove, and to allow the point
of the vibrating disk to be placed in a proper position. The point
rests on the foil under a pressure which must be regulated, and for
this purpose, as well as to detach the cylinder when it is desired
to place or take away the tinfoil, there is the articulated system
S N which sustains the support S of the vibrating disk. This system
consists of a jointed lever in which there is a nut screw for the screw
R. The handle N at the end of the lever allows the tracing system to
be turned aside when the screw R is loosened. In order to regulate the
pressure of the tracing point on the sheet of tinfoil, it is enough to
turn the screw R loosely in its socket, and to tighten it as soon as
the right degree of pressure is obtained.
This is the simple system by which speech can engrave itself on a
plate in durable characters, and it works in the following manner.
[Illustration: FIG. 67.]
The speaker stands before the mouthpiece E, as before a telephone or
an acoustic tube, and speaks in a strong, emphatic voice, with his
lips pressed against the walls of the mouthpiece, as we see in fig.
67; at the same moment he turns the handle of the cylinder, which is
provided with a heavy fly-wheel in order that the movement may be
regular. Influenced by the voice, the plate L L begins to vibrate, and
sets the tracing point at work, which presses on the tinfoil at each
vibration, and produces a furrow whose depth varies along its course in
correspondence with the unequal vibrations of the disk. The cylinder
which moves at the same time presents the different parts of the groove
of which we have spoken to the tracing point in succession; so that
when the spoken sentence comes to an end, the design which has been
pricked out, consisting of a succession of reliefs and depressions,
represents the registration of the sentence itself. The first part of
the operation is therefore accomplished, and by detaching the sheet
from the instrument the words may be put away in a portfolio. We have
now to see how the instrument is able to reproduce what has been so
easily inscribed.
For this purpose it is only necessary to repeat the process, and the
identical effect will be reproduced in an inverse sense. The tracing
stylus is replaced at the end of the groove it has already traversed,
and the cylinder is again set in motion. When the engraved track passes
again under the point, it has a tendency to raise it and to impart to
it movements which must necessarily be the repetition of those which
first produced the tracing. The vibrating plate is obedient to these
movements, and begins to vibrate, thus producing the same sounds, and
consequently the same words; yet since there is necessarily a loss of
power in this double transformation of mechanical effects, the speaking
tube C is attached to the mouthpiece E in order to intensify the
effects. Under these conditions the words reproduced by the instrument
may be heard in all parts of a hall, and it is startling to hear this
voice--somewhat shrill, it must be admitted--which seems to utter its
sentences from beyond the grave. If this invention had taken place
in the middle ages, it would certainly have been applied to ghostly
apparitions, and it would have been invaluable to miracle-mongers.
[Illustration: FIG. 68.]
As the height of the notes of the musical scale depends on the number
of vibrations effected by a vibrating substance in a given time,
speaking will be reproduced in a tone of which the pitch will depend
on the velocity of rotation given to the cylinder on which the tinfoil
is wound. If the velocity is the same as that which was used in
registration, the tone of the words reproduced is the same as that
in which they were uttered. If the velocity is greater, the tone is
higher; if less, the tone is lower; but the accent of the speaker may
always be recognised. Owing to this peculiarity the reproduction of
songs is nearly always defective in instruments turned by the hand;
they sing out of tune. This is not the case when the instrument is
moved by a well-regulated system of clockwork, and in this way a
satisfactory reproduction of a duet has been obtained.
The words registered on tinfoil can be often reproduced; but the sounds
become fainter and more indistinct at each repetition, since the
tracings in relief are gradually effaced. The reproduction on copper
is more successful, but if intended to be permanent the sheets must
be stereotyped, and in this case the instrument must be differently
arranged.
An attempt has been made to obtain speech from the phonograph by taking
the words registered inversely to their true direction. In this way the
sounds obtained were necessarily quite unlike the words uttered; yet
Messrs. Fleeming Jenkin and Ewing have observed that not only are the
vowels unchanged by this inverse action, but consonants, syllables, and
even whole words may be reproduced with the accent they would have if
spoken backwards.
The sounds produced by the phonograph, although fainter than those of
the voice which produced the registered tracing, are strong enough to
react on the ordinary string telephone, and even on a Bell telephone;
and as in this case the sounds do not go beyond the instrument, and can
only be heard by the person who is using it, it is easy to ascertain
that the sound has not been produced by trickery.
Mr. Edison presented his phonograph to the Académie des Sciences
through me, March 11, 1878, and when his agent, M. Puskas, caused
the wonderful instrument to speak, a murmur of admiration was heard
from all parts of the hall--a murmur succeeded by repeated applause.
A letter appeared in the newspapers from one of the persons present,
in which he said that ‘the learned Academy, generally so cold, had
never before abandoned itself to such enthusiasm. Yet some members
of a sceptical turn of mind, instead of examining the physical fact,
ascribed it to moral causes, and a report soon ran through the room
which seemed to accuse the Academy of having been mystified by a
clever ventriloquist. Certainly the spirit of ancient Gaul is still
to be found among the French, and even in the Academy. One said
that the sounds emitted by the instrument were precisely those of a
ventriloquist. Another asked if the movements of M. Puskas’ face and
lips as he turned the instrument did not resemble the grimaces of a
ventriloquist. A third admitted that the phonograph might emit sounds,
but believed that it was much helped by the manipulator. Finally, the
Academy requested M. du Moncel to try the experiment, and as he was not
accustomed to speak into the instrument, it was unsuccessful, to the
great joy of the incredulous. Some members of the Academy, however,
desiring to ascertain the real nature of the effects, begged M. Puskas
to repeat the experiments before them in the secretary’s office under
such conditions as they should lay down. M. Puskas complied with this
request, and they were absolutely satisfied with the result. Yet others
remained incredulous, and it was necessary that they should make the
experiment for themselves before they accepted the fact that speech
could be reproduced in so simple a way.’
The anecdote I have just related cannot be interpreted to the discredit
of the Académie des Sciences, since it is especially bound to preserve
the true principles of science intact, and only to accept startling
facts after a careful examination. Owing to this attitude, all which
emanates from the Academy can be received with complete confidence; and
we cannot approve too highly of reserve which does not give way to the
first impulse of enthusiasm and admiration.
The failure of my experiment at the Academy was simply due to the fact
that I spoke at too great a distance from the vibrating disk, and that
my lips did not touch the sides of the mouthpiece. Some days later, at
the request of several of my colleagues, I made repeated trials of
the instrument, and I soon succeeded in making it speak as well as the
supposed ventriloquist; but I learned at the same time that practice
is necessary to ensure success. Some words are reproduced more readily
than others; those which include many vowels and many _r_’s come out
better than those which abound in consonants, and especially in _s_’s.
It is therefore not surprising that, even in the case of an experienced
manipulator like Mr. Edison’s agent, some of the sentences uttered by
him are more audible than others.
The simultaneous repetition of several sentences in different languages
by registering one over the other is one of the most surprising effects
of the phonograph. As many as three different sentences have been
obtained; but in order to distinguish them through the confused sounds
which result from placing one over the other, it is necessary that
different persons, giving special attention to a particular sentence,
should thus separate them and understand their sense. Vocal airs may,
in the same way, be registered over the word tracings, and in this case
it is more easy to distinguish them.
There are several models of phonographs. The one represented in fig.
66 has been chiefly used for public experiments, but there is a small
model, generally sold to the public, in which the cylinder is much
longer, and serves at once for register and fly-wheel. This instrument
gives good results, but can only be used for short sentences. In this
model, as indeed in the other, the words are more easily registered
by fastening a small tube in the form of a prolonged speaking-trumpet
to the mouthpiece; the vibrations of the air are thus concentrated
on the vibrating disk, and act with greater energy. The tenuity of
the vibrating disk adds to the efficiency of the instrument, and the
tracing point may be fitted directly to this disk.
[Illustration: FIG. 69.]
I need not describe particularly the phonograph which acts by
clockwork. The instrument resembles the one represented fig. 66, except
that it is mounted on a rather high table, to give room for the descent
of the weight which moves the clockwork; the mechanism is applied
directly to the axis of the cylinder, supplying the place of the winch,
and is regulated by a small fly-wheel. The wheel used in an English
system has been adopted, but we prefer that of M. Villarceau, which has
small wings.
Since it is always difficult to fit the tinfoil to the cylinder, Mr.
Edison has tried, with good success, to obtain the tracing on a plane
surface of tinfoil, by means of the arrangement represented fig. 69.
In this new model, the plate on which the tin or copper sheet is to
be applied has a spiral grooving, of which one end corresponds to the
centre of the plate, and the other to its outer edges. The plate is set
in motion by a powerful system of clockwork, of which the velocity is
regulated with reference to the length of the turns of the spiral. The
vibrating disk is arranged as in the former instrument, and is placed
above this plate; the tracing point may, by means of a movement of
progression imparted to the system, follow the spiral groove from the
centre of the plate to its circumference.
It must not be supposed that all the tinfoil used for phonographic
registration is equally good. The foil must be of a definite thickness,
and combined with a definite amount of lead. That which is used for
wrapping chocolate, and indeed all foil of French manufacture, is too
thin and too exclusively made of tin to produce good results, and
M. Puskas was obliged to import some from America to continue his
experiments. The relative proportion of lead and tin has not yet been
defined, and the selection of foil has been made empirically; but as
the use of the phonograph becomes more general, this proportion must be
ascertained, and it may easily be done by analysing the composition of
the foil which gives the best results.
[Illustration: FIG. 70.]
The arrangement of the tracing point is also of much importance for
the successful action of the phonograph. It must be very slender and
very short (not exceeding a millimètre in length), so as to register
distinctly the smallest vibrations of the vibrating disk without
deviating from the normal direction of the cylinder, which might be
the case, if it were long, on account of the unequal friction exerted
on the tinfoil. It must also be made of a metal which has no tendency
to tear the metallic sheet. Iron appears to combine most of the
conditions demanded.
The phonograph is still in its infancy, and it is probable that it may
soon be enabled to register speech without the necessity of speaking
into a mouthpiece. According to the newspapers, Mr. Edison has already
discovered a way of collecting, without the aid of an acoustic tube,
the sounds uttered at a distance of three or four feet from the
instrument, and of printing them on a metallic sheet. From this there
is only a step to the power of inscribing a speech uttered in a large
hall at any distance from the phonograph; and if this step is taken,
phonography may be substituted with advantage for shorthand. We add
in a note the instructions given by M. Roosevelt to the purchasers of
phonographs, so as to enable them to work the instrument.[20]
_Considerations on the theory._--Although the explanation we have given
will make the effects of the phonograph intelligible, it leads to a
curious question which has greatly interested physicists--namely, how
it is that the tracing made on so yielding a surface as tin can, when
retraced by the stylus, of which the rigidity is relatively great,
produce a vibratory movement without being completely destroyed. To
this we reply that the retracing is effected with such extreme rapidity
that the effects of active force which are developed only manifest
themselves locally, and that under these conditions the mechanical
effects exerted are as energetic in soft as in hard substances. The
curious experiment, related in so many books on physics, must be
remembered, of a plank pierced when a candle serves as the projectile
of a gun. The various accidents caused by the discharge of paper
waddings must also be remembered. Under such conditions the motion
imparted to the molecules which receive the shock has not time to be
transmitted to the whole mass of the substance to which they belong,
and these molecules are compelled to separate from it, or at any rate
to produce, when the substance is capable of vibration, a centre of
vibration which diffuses waves throughout its surface, and produces
sounds.
Several scientific men, among others Messrs. Preece and Mayer, have
carefully studied the form of the tracing left by the voice on the
tinfoil of the phonograph, and they observe that it greatly resembles
the outline of the singing flames so well shown by Herr Koenig’s
instruments. Mr. Mayer wrote on this subject in the ‘Popular Science
Monthly Review’ of April 1878.
He said that he had been successful in reproducing a splendid tracing
on smoked glass, which gave in profile the outline of the vibrations
of sound registered on the tinfoil with their varying curves. For this
purpose he fastened to the spring support of the tracing point of
the phonograph a slender rod, terminating in a point, which pressed
obliquely against the plate of smoked glass, and, since the latter was
in a vertical position, a movement imparted to the rod enabled it to
produce a sinusoidal tracing. By this arrangement, when the phonograph
was at work, two systems of tracings were produced at the same moment,
of which one was the profile of the other.
Mr. Mayer had not, at the time he wrote, been long enough in possession
of the instrument to make many experiments with it, but from a study of
some of its curves it appeared to him that the registered outlines bore
a strong resemblance to those of Koenig’s singing flames.
[Illustration: FIG. 71.]