spoken in a uniform, drawling tone, which might, I should have thought,
have excluded the idea of imposition. Some of them are indeed far from
distinct, yet the results are not less remarkable; and when we consider
the amount of study and experience which must have been applied to
the combination of all these arrangements, it seems surprising that
physicists have not given more attention to such an interesting machine.
As for the mechanical execution, it is impossible to admire too highly
the simple and ingenious manner in which all the complicated movements
of the different vocal organs have been connected with the keyboard,
of which the mechanism has been so calculated as only to produce the
precise action of the organ which is required for any given effect. For
this purpose, the notes of the keyboard regularly increase in length,
so as to produce at a single touch different mechanical effects on the
rods which act upon the mechanism; and since most of the notes are
required to react simultaneously on the whole mechanism, the rods which
transmit the movement are fastened to a series of jointed levers which
cross the notes of the keyboard at right angles. Pegs of different
length are fastened to the notes at this junction, so as to produce the
simultaneous action of the different organs of the machine.
The public will believe that the assertions of ventriloquism are
unfounded when I add that I myself have made the machine speak.
APPENDIX.
_The Perrodon System of Telephonic Alarum._--Captain Perrodon, of
the French Artillery, has lately improved the system invented by MM.
Dutertre and Gouault, by a self-acting call. For this purpose he has
fastened a spring contact before the diaphragm, combined with the
diaphragm and the electro-magnetic system so as to form a vibrator. The
vibrations thus produced are strong enough to resound in an ordinary
telephone, so as to make the call audible in spite of external noises.
The system has been arranged in different ways. In one arrangement, a
small plate of tinfoil is glued to the outer surface of the diaphragm,
and the end of the telephone coil wire is connected, below the inner
surface of the mouthpiece, with a silver wire soldered to a spring
plate, which constitutes the contact of the vibrator. This spring
plate, slightly curved, is fixed below one of the binding-screws of
the telephone, and terminates at its free end in a regulating screw
by which the interval between the contacts can be regulated, and the
instrument can be arranged as a telephonic organ. To do this, the
screw can be withdrawn, and inserted in a nut which establishes direct
connection between the line and the telephone coil. It is easy to
adapt an ordinary telephone to this system.
In another arrangement M. Courtot’s mirror telephone has been employed,
and a sort of spring pedal is inserted in the wood of the mouthpiece,
which terminates in a bent silver wire, supporting an index adapted
to make a contact with a square plate soldered to the diaphragm. The
battery is placed in connection with the spring of the pedal, and
one end of the telephone coil-wire communicates as before with the
diaphragm. When a call is to be made, the pedal must be pressed, and
the battery immediately communicates with the silver wire which, with
the diaphragm, constitutes the vibrator, and an electric vibration
is sent through the circuit, and produces the call. For receiving,
the pedal is allowed to revert to its normal position, and the index
of the pedal, touching the contact in connection with the diaphragm,
establishes direct communication between the two telephones, while
breaking the contact of the silver wire with the diaphragm, so that the
battery cannot act.
It appears that experiments made at the musketry school at Orleans for
a distance of 370 miles have been very successful.
_M. Varey’s Microphone Speaker._--M. Varey has recently arranged
a successful microphonic speaker, in which the principle of the
microphone represented in fig. 39 is maintained. The system of three
vertical carbons is arranged inside a sort of snuff-box, of which the
lid is made of a thin plate of mica, horn, or ebonite. The snuff-box
is provided with two hinged arms, so that it may be placed in the
most convenient position for speaking, and at the same time the
sensitiveness of the instrument can be regulated. A small battery,
consisting of two Gaiffe cells of chloride of silver, is placed in the
pedestal on which the instrument stands, and sets the microphone at
work without further trouble. In this way the speaker can be used like
an ordinary telephone, and is not affected by vibrations of air. Only
vibrations of sound react upon it.
_Microphonic Speaker by Fitch._--Mr. Pope states that this speaker
has produced excellent results in America. It is merely Edison’s
carbon telephone reduced to its simplest form. It consists of a small
cylindrical box, which has a mouthpiece like the one represented
fig. 28. The box contains two carbon disks of the same diameter as
itself, and is lined with a kind of felt. Metal wires, inlaid in a
groove scooped on the circumference of the carbons, place them in
communication with the circuit and battery, and transmission takes
place by means of the vibrations of the upper carbon, which is directly
influenced by the voice without the intervention of any diaphragm.
These vibrations, which can be freely developed in consequence of the
elasticity of the felt pad which supports the lower carbon, produce
on the surface of contact of the two carbons the modifications of
intensity of current necessary for the reproduction of speech, in the
same way as other microphones.
An induction coil is necessarily employed for a long circuit, and
the effects of induction in the adjacent wires are modified by two
rheostats introduced into the circuit at its two extremities.
_Further remarks on the theory of the Telephone._--Following the
example of a certain sceptic in the Académie des Sciences, Colonel
Navez continues to maintain the theory first formed as to the mode
in which the telephone acts, in spite of the clearest proofs of its
insufficiency; but most scientific men who consider the question have
come round to our opinion, and admit the concurrence of several causes
in the reproduction of speech by this remarkable instrument. Mr.
Fleeming Jenkin writes to this effect in the new edition of a treatise
on Electricity and Magnetism.
He observes that a singular fact has been discovered by several
persons, who have ascertained that not merely non-magnetic and
non-conducting bodies can be substituted for the diaphragms of
receiving telephones, but that they will act without a diaphragm at
all. In this case it is evident that we have to do with the sounds
discovered by Page, and that they are produced by the magnet itself,
in which each molecular movement constitutes the source of the sound
produced. This sound becomes articulate as soon as its increase and
decrease can follow the increasing or decreasing action of the voice
which produces it at the sending station. It is certain that when the
transmitted currents are due to the action of the Bell diaphragm, the
sounds due to the Page effects ought to correspond with those which
would be given by iron diaphragms adapted to the receiving instruments;
so that, when a telephone has an iron diaphragm, there are in fact two
voices, that of the diaphragm, which is strong, and that of the magnet,
which is weak. When a disk of wood is substituted for one of iron, it
acts as a sounding board for the Page effect, and when the disk is of
metal, induction is developed by the magnetic modifications, and tends
to produce vibration, thus developing a third source of sound, which
may be called the Ampère effect. Finally, a fourth source of sound
may result from the induced effects produced in the wire itself in
consequence of changes in the intensity of current. These sounds, first
observed by M. de la Rive, have since been studied by Mr. Fergusson of
Edinburgh (vide ‘Telegraphic Journal’ of November 1, 1878).
Mr. Fleeming Jenkin’s opinion only differs from mine in his ascribing
the energy of sound acquired by a telephone with an iron diaphragm to
the preponderance of sounds in the latter, whereas I consider it to
be chiefly due to the increase of energy in the whole magnetic system
produced by the reaction of the two magnetic parts on each other. If
the two effects could be taken singly, it is probable that the sounds
produced by each of them separately would be similar, since in magnetic
effects the reaction and action are equal. But as they are combined,
it becomes difficult to assign to each the share which belongs to
it in the general effect observed. Besides, it is quite possible
that the sounds of the diaphragm may appear to be stronger and more
distinct because it is nearer to the ear than the magnet, and because
the effects of magnetisation and demagnetisation are then more easily
produced in consequence of the mass of the magnetic body being smaller.
Mr. Fleeming Jenkin goes on to say that the question of the
displacement of surface in the diaphragm and magnet is very complex,
but that he thinks it impossible to deny the existence of such
displacement, since the air which acts as the vehicle of sound between
the ear and the source of sound is placed in vibration; yet this
displacement maybe effected quite otherwise than by flexion. Suppose
that the magnetic molecules of these bodies are drawn together by
magnetisation, which tends to diminish the intermolecular space which
separates them, the points of surface of the substance corresponding
to these intervals will be elevated in a manner equivalent to a
displacement of surface, and the effect of this will be the same as a
flexion movement. At the moment of demagnetisation a depression instead
of an elevation will take place, and the vibratory movements will
thus be produced without any electro-magnetic attraction, and it is
precisely these vibrations which Mr. Fleeming Jenkin terms molecular
vibrations. He evidently does not mean that such attractions cannot
take place: they may react, together with the molecular vibrations,
when the electric force is capable of producing them. He adds that the
reproduction of sounds by a condenser, by simple coils, and by a carbon
microphone, has convinced him that the action just analysed requires
generalisation.
We have recently seen an article by Mr. Hughes in the ‘Telegraphic
Journal,’ Nov. 15, 1878, in which, to our surprise, he not only opposes
all the theories he has hitherto held, but cites experiments which
are quite inconclusive, since they were performed under conditions in
which electro-magnetic effects must necessarily be displayed. He made
use of voltaic currents produced by a battery of three Daniell cells.
In order to estimate the transverse effects resulting in such a case
from attraction, the experiments he mentions are wholly unnecessary:
they may be felt with the hand. On the other hand, he has evidently
forgotten that the currents employed in a Bell telephone have no
influence on a very sensitive galvanometer.
_M. Pollard’s Microphone._--This microphone, which has been arranged in
several ways, essentially consists of a carbon rod kept in a horizontal
position by a wire, and resting on two other vertical carbons. The
upright of the arm which holds the wire can revolve together with
this arm, and is thus able to regulate the pressure of the horizontal
carbon on the two vertical carbons. It appears that this instrument
is extremely sensitive, and that the regulation effected on the two
contacts is better than when it is effected on one only. It is fair to
add that M. Voisin previously sent me the sketch of a somewhat similar
arrangement.
M. Dutertre has also made use of such an arrangement in what he calls
the Dolmen microphone. Three pieces of coke in the form of a dolmen,
that is, two uprights, supporting a third and horizontal carbon, are
placed in circuit. M. Gouault has informed me that speech was well
transmitted by this instrument, and it is, like that of Mr. Blyth,
which succeeded it, of wonderful simplicity.
This microphone, as well as one composed of two pieces of lead-pencil
placed in a watch-case, and connected by a piece of money, were
exhibited to the Industrial Society at Rouen, February 1, 1878, of
which an account was published in the Bulletin of that society.
_M. Ader’s Electrophone._--M. Ader has recently constructed a
remarkable telephonic instrument, which reproduces speech and song in a
quite exceptional and simple way. It consists of a drum 15 centimètres
in diameter, covered with parchment at one end only. Six small tin
armatures, one centimètre in length and two millimètres in width,
are fixed in the centre of the parchment in a circle six centimètres
in diameter. Six microscopic electro-magnets, whose distance from
the armatures can be regulated by a screw, are placed opposite the
armatures within a wooden circle. The magnets are horseshoe, with
branches 12 millimètres long and 4 millimètres in diameter, including
the coils, and the magnetic core is 1½ millimètre thick. They are all
in connection, and act simultaneously under the sole influence of the
battery current. The sender is the same as that of M. Ader described
before. With this instrument speech may be heard at a distance of six
or seven yards, and songs are much more distinctly heard than in the
singing condenser. Owing to the simplicity of the arrangement, the
instrument is not costly.
The extraordinary effects of this telephone are due to the small size
of the electro-magnets, which, as we believe, produce much more rapid
magnetic effects than those of larger size. M. Ader has also made a
small ordinary telephone based on this principle, of which the sounds
are much stronger than in others.
_Modification of Bell Telephone._--Mr. Gower has recently made a new
system of telephone without a battery, which not only reproduces
speech loudly enough to be heard at the distance of eight or nine
yards from the instrument, but will also transmit it when the speaker
is at a moderate distance from the sending instrument. In this latter
case, indeed, the receiving telephone must be brought close to the
ear. Although this double problem had already been solved by the use
of telephones with microphonic senders, the results furnished by the
instruments in question are still more curious, since they are obtained
without batteries, and are even more distinct.
In this new system, which is only an improvement on Bell’s square
model, the horseshoe magnet is of a peculiar form, which renders it
more powerful. It is formed of a kind of half-circle of magnetised
steel, with its two ends turned back, so as to form a diameter of the
circle, only this diameter is divided in the centre: so that the two
poles of the magnet are placed one before the other, as in Faraday’s
electro-magnet. The poles are tipped with iron, terminating in front in
two thin iron plates, on which are placed the electro-magnetic coils,
which are oblong, and constitute the magnetic core. The diaphragm,
thicker than the ordinary diaphragms, is of tin, and is fixed firmly
to the edges of the circular box which encloses the whole, and which
forms a kind of sounding-box. The box is made of copper, and the
diaphragm is so firmly fastened to it as to become homogeneous with it,
and to give out a sound when the box is touched, which is not the case
in ordinary telephones. This is one of the conditions which make the
instrument a better conductor of sound. The magnet is also much more
powerful. It is magnetised by a current from a powerful Gramme machine,
which acts upon it for almost twenty minutes. The instrument has,
strictly speaking, no mouthpiece: the lid of the box which supports the
diaphragm, and is separated from it by a space of two millimètres, has
merely a hole bored in it above the centre of the diaphragm, and into
this hole either a tin trumpet, 50 centimètres in length, is screwed,
when the instrument is required to reproduce or transmit speech to a
distance, or an acoustic tube when it is to be used like an ordinary
telephone. The remarkable part of the system is that the instrument
can itself give a very loud call by only breathing into it instead of
speaking.
For this purpose a small oblong opening is made in the diaphragm at a
half diameter from its centre, and behind this the reed of an harmonium
is applied to a square copper plate fixed on the diaphragm itself. On
using the bellows the expelled air passes through this little hole,
and, on reaching the reed, sets it in vibration, and produces a sound
of which the acuteness depends on the conditions of the vibrating
plate. This addition to the diaphragm in no way alters its properties
in the reproduction of speech, so that, after using the bellows,
conversation may begin, and the receiving telephone repeats what is
said after emitting a sound somewhat resembling the note of a bugle.
The instrument is then provided with the speaking tube of which we
have spoken.
Nothing can be more remarkable than this power of listening to
conversation while seated in an armchair six or seven yards from
the instrument, nor is it necessary to move in order to reply. The
correspondent, indeed, must be close to the acoustic tube in order
to speak and listen, and he must speak rather loud in order to be
heard at any distance from the other station. But the listener
receives the sounds so amplified that it might be supposed that a
giant was speaking, and conversation held in a low tone may even be
distinguished. These results are really extraordinary, and even to
those familiar with such effects this incessant progress is surprising.
These results may be ascribed to the following causes:--
1. First, that the conditions of the magnet are better than those of
ordinary instruments.
2. That the diaphragm is also thicker, larger, and better stretched.
3. That the box is of metal, and calculated to act as a sounding-box.
4. The speaking trumpet magnifies the sounds.
5. The acoustic tubes concentrate the sound waves on the centre of the
diaphragm.
_Note on some fresh Experiments with Telephones without any Diaphragm._
In a paper published March 4, 1878, I made some suggestions on
the theory of the sounds produced in the telephone, and on the
contradictory assertions of physicists as to the transmission of speech
by ordinary telephones when devoid of diaphragm. These remarks induced
M. Ader to undertake some experiments which not only demonstrate the
truth of my opinion, but bring to light some fresh facts which may be
of great importance to acoustic science.
M. Ader has in fact not only succeeded in making a telephone without
a diaphragm speak, but he has made it speak more loudly and with less
alteration of the voice than we find to be the case with a small model
of the ordinary telephone. No one, therefore, can now maintain that the
sounds produced by the magnetic cores are so faint that they cannot be
taken into account among the effects produced, and that it is at any
rate impossible for them to reproduce articulate sounds.
To obtain this result, M. Ader reduced the size of the magnetic core to
that of a simple iron wire, one millimètre in diameter, and he fastened
it by one of its ends to a small wooden board. Under these conditions,
it was enough to fasten a small helix of fine wire on this iron wire,
and to apply the board to the ear in order to hear speech distinctly,
with the aid of a microphonic speaker actuated by a voltaic current.
But the range of sound was considerably increased if a mass of metal
was applied to the free end of the iron wire: in this case it was
possible to hear when the wooden board was removed to a distance of ten
or fifteen centimètres from the ear.
If the wire is in contact with masses of metal at each end, the effect
is further increased; but the two masses must not be in metallic
communication with each other, and must be to some extent insulated by
a more or less elastic medium. If the metallic masses are soldered to
the wire, the effects are still greater.
M. Ader was also able to reproduce speech by using a simple coil
without a magnetic core, but in this case the spirals must be open, and
not pressed together. If they are steeped in gum, no sound is heard,
but speech will become instantly audible if a wire or a magnetised
needle is inserted in the coil, or even if a second metallic helix is
placed in the circuit: always provided that one of the ends of these
magnetic organs rests upon, or is fastened to, the board on which the
coil is fixed.
M. Ader has likewise obtained a very distinct reproduction of speech
at a distance of two or three yards from the instrument by inserting
between the two stretched membranes of two tambourines a bent wire
which acts as a spring and passes through an electro-magnetic coil.
Under these conditions, magnetisation of the wire in a greater or less
degree affects its elasticity and causes vibrations which are magnified
by the membranes, and transmitted sounds are reproduced with intensity.
Unfortunately articulate speech is less distinct with this system than
with the one I described before.
M. Ader has often had occasion to make one curious remark, namely,
that the _timbre_ of the voice and its high or low key varies with the
degree of tension given to the wire; but if the fundamental note of
the wire is deadened by pressing it between the fingers, the sounds
reproduced then become dull and monotonous. They are also somewhat
fainter.
Signor Carlo Resio has also observed that in a telephone sender the
variations of intensity in the current correspond with the vibrations
caused by speech, and these are reproduced by corresponding variations
in a liquid column, which may thus act as a telephone receiver,
and consequently may reproduce speech without any electro-magnetic
organ, as in a microphone speaker. Under these conditions, however, a
layer of water is inserted between the platinum electrodes and the
surrounding air, and consequently this liquid layer must be put in
vibration under the influence of varying intensities of current.
Mr. Edison has also now made a practical application of the chemical
telephone we have mentioned before. The trials made with it have been
very satisfactory, showing that sounds transmitted in this way can be
heard in a large room.
PRINTED BY
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LONDON
FOOTNOTES
[1] Mr. Gray, in an article inserted in the _Telegrapher_ of October
7, 1876, enters into full details of this mode of transmitting sounds
by the tissues of the human body, and he gives the following as the
conditions in which it must be placed to obtain a favourable result: 1.
The electricity must be of a high tension, in order to have an effect
perceptible to the ear.
2. The substance employed to touch the metallic plate must be soft,
flexible, and a good conductor, up to the point of contact: it must
then interpose a slight resistance, neither too great nor too small.
3. The disk and the hand, or any other tissue, must not only be in
contact, but the contact must result from rubbing or gliding over the
surface.
4. The parts in contact must be dry, so as to maintain the required
degree of resistance.
[2] He cites the following names in his account of electric
telephony:--Page, Marrian, Beatson, Gassiot, De la Rive, Matteucci,
Guillemin, Wertheim, Wartmann, Janniar, Joule, Laborde, Legat, Reiss,
Poggendorf, Du Moncel, Delezenne, Gore, &c. Vide Mr. Bell’s paper, in
the _Journal of the Society of Telegraphic Engineers_ in London, vol.
vi. pp. 390, 391.
[3] This statement is disputed by Mr. Elisha Gray, owing, as we shall
see, to a misunderstanding as to the word _undulatory_ current.
[4] _Elisha Gray._ Eng. Pat. Spec. No. 2646, Aug. 1874.