its nature, by means of which words spoken by the human voice can be,
so to speak, stored up and reproduced at will over and over again
hundreds, it may be thousands, of times. What will be thought of a
piece of mechanism by means of which a message of any length can be
spoken on to a plate of metal--that plate sent by post to any part of
the world and the message absolutely respoken in the very voice of the
sender, purely by mechanical agency? What, too, shall be said of a
mere machine, by means of which the old familiar voice of one who is
no longer with us on earth can be heard speaking to us in the very
tones and measure to which our ears were once accustomed?”
The first Edison machine was the climax of research in the realm of
sound. As long ago as 1856 a Mr. Leo Scott made an instrument which
received the formidable name of Phonautograph, on account of its
capacity to register mechanically the vibrations set up in the
atmosphere by the human voice or by musical instruments. A large metal
cone like the mouth of an ear-trumpet had stretched across its smaller
end a membrane, to which was attached a very delicate tracing-point
working on the surface of a revolving cylinder covered with blackened
paper. Any sound entering the trumpet agitated the membrane, which in
turn moved the stylus and produced a line on the cylinder
corresponding to the vibration. Scott’s apparatus could only record.
It was, so to speak, the first half of the phonograph. Edison, twenty
years later, added the active half. His machine, as briefly described
in the _Times_, was simple; so very simple that many scientists must
have wondered how they failed to invent it themselves.
A metal cylinder grooved with a continuous square-section thread of
many turns to the inch was mounted horizontally on a long axle cut at
one end with a screw-thread of the same “pitch” as that on the
cylinder. The axle, working in upright supports, and furnished with a
heavy flywheel to render the rate of revolution fairly uniform, was
turned by a handle. Over the grooved cylinder was stretched a thin
sheet of tinfoil, and on this rested lightly a steel tracing-point,
mounted at the end of a spring and separated from a vibrating
diaphragm by a small pad of rubber tubing. A large mouthpiece to
concentrate sound on to the diaphragm completed the apparatus.
To make a record with this machine the cylinder was moved along until
the tracing-point touched one extremity of the foil. The person
speaking into the mouthpiece turned the handle to bring a fresh
surface of foil continuously under the point, which, owing to the
thread on the axle and the groove on the cylinder being of the same
pitch, was always over the groove, and burnished the foil down into it
to a greater or less depth according to the strength of the impulses
received from the diaphragm.
[Illustration: _A unique group of Phonographs. 1. The oldest
phonograph in existence, now in South Kensington Museum. 2. Tinfoil
instrument. 3. A cheaper form of the same. 4. A “spectacle-form”
graphophone. 5. An exactly similar instrument, half-size scale. 6. A
doll fitted with phonograph._]
The record being finished, the point was lifted off the foil, the
cylinder turned back to its original position, and the point allowed
to run again over the depressions it had made in the metal sheet. The
latter now became the active part, imparting to the air by means of
the diaphragm vibrations similar in duration and quality to those that
affected it when the record was being made.
It is interesting to notice that the phonograph principle was
originally employed by Edison as a telephone “relay.” His attention
had been drawn to the telephone recently produced by Graham Bell, and
to the evil effects of current leakage in long lines. He saw that the
amount of current wasted increased out of proportion to the length of
the lines--even more than in the proportion of the squares of their
lengths--and he hoped that a great saving of current would be effected
if a long line were divided into sections and the sound vibrations
were passed from one to the other by mechanical means. He used as the
connecting link between two sections a strip of moistened paper, which
a needle, attached to a receiver, indented with minute depressions,
that handed on the message to another telephone. The phonograph
proper, as a recording machine, was an after-thought.
Edison’s first apparatus, besides being heavy and clumsy, had in
practice faults which made it fall short of the description given in
the _Times_. Its tone was harsh. The records, so far from enduring a
thousand repetitions, were worn out by a dozen. To these defects must
be added a considerable difficulty in adjusting a record made on one
machine to the cylinder of another machine.
Edison, being busy with his telephone and electric lamp work, put
aside the phonograph for a time. Graham Bell, his brother, Chichester
Bell, and Charles Sumner Tainter, developed and improved his crude
ideas. They introduced the Graphophone, using easily removable
cylinder records. For the tinfoil was substituted a thin coating of a
special wax preparation on light paper cylinders. Clockwork-driven
motors replaced the hand motion, and the new machines were altogether
more handy and effective. As soon as he had time Edison again entered
the field. He conceived the solid wax cylinder, and patented a small
shaving apparatus by means of which a record could be pared away and a
fresh surface be presented for a new record.
The phonograph or graphophone of to-day is a familiar enough sight;
but inasmuch as our readers may be less intimately acquainted with its
construction and action than with its effects, a few words will now be
added about its most striking features.
In the first place, the record remains stationary while the trumpet,
diaphragm and stylus pass over it. The reverse was the case with the
tinfoil instrument.
The record is cut by means of a tiny sapphire point having a circular
concave end very sharp at the edges, to gouge minute depressions into
the wax. The point is agitated by a delicate combination of weights
and levers connecting it with a diaphragm of French glass 1/140 inch
thick. The reproducing point is a sapphire ball of a diameter equal to
that of the gouge. It passes over the depressions, falling into them
in turn and communicating its movements to a diaphragm, and so
tenderly does it treat the records that a hundred repetitions do not
inflict noticeable damage.
It is a curious instance of the manner in which man unconsciously
copies nature that the parts of the reproducing attachment of a
phonograph contains parts corresponding in function exactly to those
bones of the ear known as the Hammer, Anvil, and Stirrup.
To understand the inner working of the phonograph the reader must be
acquainted with the theory of sound. All sound is the result of
impulses transmitted by a moving body usually reaching the ear through
the medium of the air. The quantity of the sound, or loudness, depends
on the violence of the impulse; the tone, or note, on the number of
impulses in a given time (usually fixed as one second); and the
quality, or _timbre_, as musicians say, on the existence of minor
vibrations within the main ones.
If we were to examine the surface of a phonograph record (or
phonogram) under a powerful magnifying glass we should see a series
of scoops cut by the gouge in the wax, some longer and deeper than
others, long and short, deep and shallow, alternating and recurring in
regular groups. The depth, length, and grouping of the cuts decides
the nature of the resultant note when the reproducing sapphire point
passes over the record--at a rate of about ten inches a second.
The study of a tracing made on properly prepared paper by a point
agitated by a diaphragm would enable us to understand easily the cause
of that mysterious variation in _timbre_ which betrays at once what
kind of instrument has emitted a note of known pitch. For instance,
let us take middle C, which is the result of a certain number of
atmospheric blows per second on the drum of the ear. The same note may
come from a piano, a violin, a banjo, a man’s larynx, an organ, or a
cornet; but we at once detect its source. It is scarcely imaginable
that a piano and a cornet should be mistaken for one another. Now, if
the tracing instrument had been at work while the notes were made
successively it would have recorded a wavy line, each wave of exactly
the same _length_ as its fellows, but varying in its _outline_
according to the character of the note’s origin. We should notice that
the waves were themselves wavy in section, being jagged like the teeth
of a saw, and that the small secondary waves differed in size.
The minor waves are the harmonics of the main note. Some musical
instruments are richer in these harmonics than others. The fact that
these delicate variations are recorded as minute indentations in the
wax and reproduced is a striking proof of the phonograph’s mechanical
perfection.
Furthermore, the phonograph registers not only these composite notes,
but also chords or simultaneous combinations of notes, each of which
may proceed from a different instrument. In its action it here
resembles a man who by constant practice is able to add up the pounds,
shillings, and pence columns in his ledger at the same time, one wave
system overlapping and blending with another.
The phonograph is not equally sympathetic with all classes of sounds.
Banjo duets make good records, but the guitar gives a poor result.
Similarly, the cornet is peculiarly effective, but the bass drum
disappointing. The deep chest notes of a man come from the trumpet
with startling truth, but the top notes on which the soprano prides
herself are often sadly “tinny.” The phonograph, therefore, even in
its most perfect form is not the equal of the exquisitely sensitive
human ear; and this may partially be accounted for by the fact that
the diaphragm in both recorder and reproducer has its own fundamental
note which is not in harmony with all other notes, whereas the ear,
like the eye, adapts itself to any vibration.
Yet the phonograph has an almost limitless répertoire. It can justly
be claimed for it that it is many musical instruments rolled into one.
It will reproduce clearly and faithfully an orchestra, an
instrumental soloist, the words of a singer, a stump orator, or a
stage favourite. Consequently we find it every where--at
entertainments, in the drawing-room, and even tempting us at the
railway station or other places of public resort to part with our
superfluous pence. At the London Hippodrome it discourses to audiences
of several thousand persons, and in the nursery it delights the
possessors of ingeniously-constructed dolls which, on a button being
pressed and concealed machinery being brought into action, repeat some
well-known childish melody.
It must not be supposed that the phonograph is nothing more than a
superior kind of scientific toy. More serious duties than those of
mere entertainment have been found for it.
At the last Presidential Election in the States the phonograph was
often called upon to harangue large meetings in the interests of the
rival candidates, who were perhaps at the time wearing out their
voices hundreds of miles away with the same words.
Since the pronunciation of a foreign language is acquired by constant
imitation of sounds, the phonograph, instructed by an expert, has been
used to repeat words and phrases to a class of students until the
difficulties they contain have been thoroughly mastered. The sight of
such a class hanging on the lips--or more properly the trumpet--of a
phonograph gifted with the true Parisian accent may be common enough
in the future.
As a mechanical secretary and substitute for the shorthand writer the
phonograph has certainly passed the experimental stage. Its daily use
by some of the largest business establishments in the world testify to
its value in commercial life. Many firms, especially American, have
invested heavily in establishing phonograph establishments to save
labour and final expense. The manager, on arriving at his office in
the morning, reads his letters, and as the contents of each is
mastered, dictates an answer to a phonograph cylinder which is
presently removed to the typewriting room, where an assistant, placing
it upon her phonograph and fixing the tubes to her ears, types what is
required. It is interesting to learn that at Ottawa, the seat of the
Canadian Government, phonographs are used for reporting the
parliamentary proceedings and debates.
There is therefore a prospect that, though the talking-machine may
lose its novelty as an entertainer, its practical usefulness will be
largely increased. And while considering the future of the instrument,
the thought suggests itself whether we shall be taking full advantage
of Mr. Edison’s notable invention if we neglect to make records of all
kinds of intelligible sounds which have more than a passing interest.
If the records were made in an imperishable substance they might
remain effective for centuries, due care being taken of them in
special depositories owned by the nation. To understand what their
value would be to future generations we have only to imagine ourselves
listening to the long-stilled thunder of Earl Chatham, to the golden
eloquence of Burke, or the passionate declamations of Mrs. Siddons.
And in the narrower circle of family interests how valuable a part of
family heirlooms would be the phonograms containing a vocal message to
posterity from Grandfather this, or Great-aunt that, whose portraits
in the drawing-room album do little more than call attention to the
changes in dress since the time when their subjects faced the camera!
_Record-Making and Manufacture._--Phonographic records are of two
shapes, the cylindrical and the flat, the latter cut with a volute
groove continuously diminishing in diameter from the circumference to
the centre. Flat records are used in the Gramophone--a reproducing
machine only. Their manufacture is effected by first of all making a
record on a sheet of zinc coated with a very thin film of wax, from
which the sharp steel point moved by the recording diaphragm removes
small portions, baring the zinc underneath. The plate is then flooded
with an acid solution, which eats into the bared patches, but does not
affect the parts still covered with wax. The etching complete, the wax
is removed entirely, and a cast or electrotype _negative_ record made
from the zinc plate. The indentations of the original are in this
represented by excrescences of like size; and when the negative block
is pressed hard down on to a properly prepared disc of vulcanite or
celluloid, the latter is indented in a manner that reproduces exactly
the tones received on the “master” record.
Cylindrical records are made in two ways, by moulding or by copying.
The second process is extremely simple. The “master” cylinder is
placed on a machine which also rotates a blank cylinder at a short
distance from and parallel to the first. Over the “master” record
passes a reproducing point, which is connected by delicate levers to a
cutting point resting on the “blank,” so that every movement of the
one produces a corresponding movement of the other.
This method, though accurate in its results, is comparatively slow.
The _moulding_ process is therefore becoming the more general of the
two. Edison has recently introduced a most beautiful process for
obtaining negative moulds from wax positives. Owing to its shape, a
zinc cylinder could not be treated like a flat disc, as, the negative
made, it could not be detached without cutting. Edison, therefore,
with characteristic perseverance, sought a way of electrotyping the
wax, which, being a non-conductor of electricity, would not receive a
deposit of metal. The problem was how to deposit on it.
Any one who has seen a Crookes’ tube such as is used for X-ray work
may have noticed on the glass a black deposit which arises from the
flinging off from the negative pole of minute particles of platinum.
Edison took advantage of this repellent action; and by enclosing his
wax records in a vacuum between two gold poles was able to coat them
with an infinitesimally thin skin of pure gold, on which silver or
nickel could be easily deposited. The deposit being sufficiently thick
the wax was melted out and the surface of the electrotype carefully
cleaned. To make castings it was necessary only to pour in wax, which
on cooling would shrink sufficiently to be withdrawn. The delicacy of
the process may be deduced from the fact that some of the sibilants,
or hissing sounds of the voice, are computed to be represented by
depressions less than a millionth of an inch in depth, and yet they
are most distinctly reproduced! Cylinder records are made in two
sizes, 2-1/2 and 5 inches in diameter respectively. The larger size
gives the most satisfactory renderings, as the indentations are on a
larger scale and therefore less worn by the reproducing point. One
hundred turns to the inch is the standard pitch of the thread; but in
some records the number is doubled.
Phonographs, Graphophones, and Gramophones are manufactured almost
entirely in America, where large factories, equipped with most perfect
plant and tools, work day and night to cope with the orders that flow
in freely from all sides. One factory alone turns out a thousand
machines a day, ranging in value from a few shillings to forty pounds
each. Records are made in England on a large scale; and now that the
Edison-Bell firm has introduced the unbreakable celluloid form their
price will decrease. By means of the Edison electrotyping process a
customer can change his record without changing his cylinder. He takes
the cylinder to the factory, where it is heated, placed in the mould,
and subjected to great pressure which drives the soft celluloid into
the mould depressions; and behold! in a few moments “Auld Lang Syne”
has become “Home, Sweet Home,” or whatever air is desired. Thus
altering records is very little more difficult than getting a fresh
book at the circulating library.
THE PHOTOGRAPHOPHONE.
This instrument is a phonograph working entirely by means of light and
electricity.
The flame of an electric lamp is brought under the influence of sound
vibrations which cause its brilliancy to vary at every alteration of
pitch or quality.
The light of the flame is concentrated through a lens on to a
travelling photographic sensitive film, which, on development in the
ordinary way, is found to be covered with dark and bright stripes
proportionate in tone to the strength of the light at different
moments. The film is then passed between a lamp and a selenium plate
connected with an electric circuit and a telephone. The resistance of
the selenium to the current varies according to the power of the light
thrown upon it. When a dark portion of the film intercepts the light
of the lamp the selenium plate offers high resistance; when the light
finds its way through a clear part of the film the resistance weakens.
Thus the telephone is submitted to a series of changes affecting the
“receiver.” As in the making of the record speech-vibrations affect
light, and the light affects a sensitive film; so in its reproduction
the film affects a sensitive selenium plate, giving back to a
telephone exactly what it received from the sound vibrations.
One great advantage of Mr. Ruhmer’s method is that from a single film
any number of records can be printed by photography; another, that, as
with the Telegraphone (see below), the same film passed before a
series of lamps successively is able to operate a corresponding number
of telephones.
The inventor is not content with his success. He hopes to record not
merely sounds but even pictures by means of light and a selenium
plate.
THE TELEPHONOGRAPH.
Having dealt with the phonograph and the telephone separately, we may
briefly consider one or two ingenious combinations of the two
instruments. The word Telephonograph signifies an apparatus for
recording sounds sent from a distance. It takes the place of the human
listener at the telephone receiver.
Let us suppose that a Reading subscriber wishes to converse along the
wires with a friend in London, but that on ringing up his number he
discovers that the friend is absent from his home or office. He is
left with the alternative of either waiting till his friend returns,
which may cause a serious loss of time, or of dictating his message, a
slow and laborious process. This with the ordinary telephonic
apparatus. But if the London friend be the possessor of a
Telephonograph, the person answering the call-bell can, if desired to
do so, switch the wires into connection with it and start the
machinery; and in a very short time the message will be stored up for
reproduction when the absent friend returns.
The Telephonograph is the invention of Mr. J. E. O. Kumberg. The
message is spoken into the telephone transmitter in the ordinary way,
and the vibrations set up by the voice are caused to act upon a
recording stylus by the impact of the sound waves at the further end
of the wires. In this manner a phonogram is produced on the wax
cylinder in the house or office of the person addressed, and it may be
read off at leisure. A very sensitive transmitter is employed, and if
desired the apparatus can be so arranged that by means of a
double-channel tube the words spoken are simultaneously conveyed to
the telephone and to an ordinary phonograph, which insures that a
record shall be kept of any message sent.
The _Telegraphone_, produced by Mr. Valdemar Poulsen, performs the
same functions as the telephonograph, but differs from it in being
entirely electrical. It contains no waxen cylinder, no cutting-point;
their places are taken respectively by a steel wire wound on a
cylindrical drum (each turn carefully insulated from its neighbours)
and by a very small electro-magnet, which has two delicate points that
pass along the wire, one on either side, resting lightly upon it.
As the drum rotates, the whole of the wire passes gradually between
the two points, into which a series of electric shocks is sent by the
action of the speaker’s voice at the further end of the wires. The
shocks magnetise the portion of steel wire which acts as a temporary
bridge between the two points. At the close of three and a half
minutes the magnet has worked from one end of the wire coil to the
other; it is then automatically lifted and carried back to the
starting-point in readiness for reproduction of the sounds. This is
accomplished by disconnecting the telegraphone from the telephone
wires and switching it on to an ordinary telephonic earpiece or
receiver. As soon as the cylinder commences to revolve a second time,
the magnet is influenced by the series of magnetic “fields” in the
wires, and as often as it touches a magnetised spot imparts an impulse
to the diaphragm of the receiver, which vibrates at the rate and with
the same force as the vibrations originally set up in the distant
transmitter. The result is a clear and accurate reproduction of the
message, even though hours and even days may have elapsed since its
arrival.
As the magnetic effects on the wire coil retain their power for a
considerable period, the message may be reproduced many times. As soon
as the wire-covered drum is required for fresh impressions, the old
one is wiped out by passing a permanent magnet along the wire to
neutralise the magnetism of the last message.