Musical and harmonic sounds explained--Power of breaking glasses
with the voice--Musical sounds from the vibration of a column
of air--and of solid bodies--Kaleidophone--Singular acoustic
figures produced on sand laid on vibrating plates of glass--and
on stretched membranes--Vibration of flat rulers and cylinders
of glass--Production of silence from two sounds--Production
of darkness from two lights--Explanation of these singular
effects--Acoustic automaton--Droz’s bleating sheep--Maillardet’s
singing-bird--Vaucanson’s flute-player--His pipe and
tabor-player--Baron Kempelen’s talking-engine--Kratzenstein’s
speaking-machine--Mr. Willis’s researches.
Among the discoveries of modern science, there are few more remarkable
than those which relate to the production of harmonic sounds. We
are all familiar with the effects of musical instruments, from the
deep-toned voice of the organ to the wiry shrill of the Jew’s harp.
We sit entranced under their magical influence, whether the ear is
charmed with the melody of their sounds, or the heart agitated by the
sympathies which they rouse. But though we may admire their external
form, and the skill of the artist who constructed them, we never think
of inquiring into the cause of such extraordinary combinations.
Sounds of all kinds are conveyed to the organ of hearing through the
air; and if this element were to be destroyed, all nature would be
buried in the deepest silence. Noises of every variety, whether they
are musical or discordant, high or low, move through the air of our
atmosphere at the surface of the earth with a velocity of 1090 feet
in a second, or 765 miles per hour; but in sulphurous acid gas sound
moves only through 751 feet in a second, while in hydrogen gas it moves
with the great velocity of 3000 feet. Along fluid and solid bodies,
its progress is still more rapid. Through water it moves at the rate
of 4708 feet in a second, through tin at the rate of 8175 feet, and
through iron, glass, and some kinds of wood, at the rate of 18,530 feet.
When a number of single and separate sounds follow each other in rapid
succession, they produce a continued sound, in the same manner as a
continuous circle of light is produced by whirling round a burning
stick before the eye. In order that the sound may appear a single one
to the ear, nearly sixteen separate sounds must follow one another
every second. When these sounds are exactly similar, and recur at equal
intervals, they form a musical sound. In order to produce such sounds
from the air, it must receive at least sixteen equally distant impulses
or strokes in a second. The most common way of producing this effect is
by a string or wire A B, Fig. 40, stretched between the fixed points A,
B. If this string is taken by the middle and pulled aside, or if it is
suddenly struck, it will vibrate between its two fixed points, as shown
in the figure, passing alternately on each side of its axis A B, the
vibrations gradually diminishing by the resistance of the air till the
string is brought to rest. Its vibrations, however, may be kept up, by
drawing a rosined fiddle-bow across it, and while it is vibrating it
will give out a sound corresponding to the rapidity of its vibrations,
and arising from the successive blows or impulses given to the air by
the string. This sound is called the fundamental sound of the string,
and its acuteness or sharpness increases with the number of vibrations
which the string performs in a second.
[Illustration: _Fig. 40._]
If we now touch the vibrating string A´ B lightly with the finger,
or with a feather at the middle point C, Fig. 40, it will give out a
more acute but fainter sound than before, and while the extent of its
vibrations is diminished, their frequency is doubled. In like manner,
if we touch the string A´´ B´´, Fig. 40, at a point C, so that A´´ C is
one-third of A´´ B´´, the note will be still more acute, and correspond
to thrice the number of vibrations. All this might have been expected;
but the wonderful part of the experiment is, that the vibrating string
A´ B´ divides itself at C into two parts A´ C, C B´, the part A´ C
vibrating round A and C as fixed points, and the part C B´ round C and
B´, but always so that the part A´ C is at the same distance on the
one side of the axis A´ B´ as at A _m_ C, while the part C B is on
the other side, as at C _n_ B. Hence the point C, being always pulled
by equal and opposite forces, remains at rest as if it were absolutely
fixed. This stationary point is called a _node_, and the vibrating
portions A´_m_ C, C _n_ B´ loops. The very same is true of the string
A´´ B´´, the points C and D being stationary points; and upon the
same principle a string may be divided into any number of vibrating
portions. In order to prove that the string is actually vibrating in
these equal subdivisions, we have only to place a piece of light paper
with a notch in it on different parts of the string. At the nodes C and
D it will remain perfectly at rest, while at _m_ or _n_ in the middle
of the loops it will be thrown off or violently agitated.
The acute sounds given out by each of the vibrating portions are called
_harmonic sounds_, and they accompany the fundamental sound of the
string in the very same manner as we have already seen that the eye
sees the accidental or harmonic colours while it is affected with the
fundamental colour.
The subdivision of the string, and consequently the production of
harmonic sounds, may be effected without touching the string at all,
and by means of a sympathetic action conveyed by the air. If a string
A B, for example, Fig. 40, is at rest, and if a shorter string A´´ C,
one third of its length, fixed at the two points A´´ and C, is set
vibrating in the same room, the string A B will be set vibrating in
three loops like A´´ B´´, giving out the same harmonic sounds as the
small string A´´ C.
It is owing to this property of sounding bodies that singers with great
power of voice are able to break into pieces a large tumbler glass, by
singing close to it its proper fundamental note; and it is from the
same sympathetic communication of vibrations that two pendulum clocks
fixed to the same wall, or two watches lying upon the same table, will
take the same rate of going, though they would not agree with one
another if placed in separate apartments. Mr. Ellicott even observed
that the pendulum of the one clock will stop that of the other, and
that the stopped pendulum will, after a certain time, resume its
vibrations, and in its turn stop the vibrations of the other pendulum.
The production of musical sounds by the vibrations of a column of air
in a pipe is familiar to every person, but the extraordinary mechanism
by which it is effected is known principally to philosophers. A column
of air in a pipe may be set vibrating by blowing over the open end of
it, as is done in Pan’s pipes; or by blowing over a hole in its side,
as in the flute; or by blowing through an aperture called a reed,
with a flexible tongue, as in the clarionet. In order to understand
the nature of this vibration, let AB, Fig. 41, be a pipe or tube, and
let us place in it a spiral spring AB, in which the coil or spire are
at equal distances, each end of the spiral being fixed to the end of
the tube. This elastic spring may be supposed to represent the air in
the pipe, which is of equal density throughout. If we take hold of
the spring at _m_, and push the point _m_ towards A and towards B in
succession, it will give us a good idea of the vibration of an elastic
column of air. When _m_ is pushed towards A, the spiral spring will
be compressed or condensed, as shown at _m_ A, No. 2, while at the
other end it will be dilated or rarefied, as shown at _m_ B, and in
the middle of the tube it will have the same degree of compression as
in No. 1. When the string is drawn to the other end of the tube B, the
spring will be, as in No. 3, condensed at the end B, and dilated at
the end A. Now when a column of air vibrates in a pipe AB, the whole
of it rushes alternately from B to A, as in No. 2, and from A to B as
in No. 3, being condensed at the end A, No. 2, and dilated or rarefied
at the end B, while in No. 3 it is rarefied at A and condensed at B,
preserving its natural density at the middle point between A and B. In
the case of the spring the ends AB are alternately pushed outwards and
pulled inwards by the spring, the end A being pushed outwards in No. 2,
and B pulled inwards, while in No. 3 A is pulled inwards and B pushed
outwards.
[Illustration: _Fig. 41._]
That the air vibrating in a pipe is actually in the state now
described, may be shown by boring small holes in the pipe, and putting
over them pieces of a fine membrane. The membrane opposite to the
middle part between A and B where the particles of the air have the
greatest motion, will be violently agitated, while at points nearer the
ends A and B it will be less and less affected.
[Illustration: _Fig. 42._]
Let us now suppose two pipes, AB, BC, to be joined together as in Fig.
42, and to be separated by a fixed partition at B; and let a spiral
spring be fixed in each. Let the spring AB be now pushed to the end
A, while the spring BC is pushed to C, as in No. 1, and back again,
as in No. 2, but always in opposite directions; then it is obvious
that the partition B is in No. 1 drawn in opposite directions towards
A and towards C, and always with forces equal to each other: that is,
when B is drawn slightly towards A, which it is at the beginning of
the motion, it is also drawn slightly towards C; and when it is drawn
forcibly towards A, as it is at the end of the motion of the spring,
it is also drawn forcibly towards C. If the partition B, therefore, is
moveable, it will still remain fixed during the opposite excursions
of the spiral springs; nay, if we remove the partition, and hook the
end of one spiral spring to the end of the other, the node or point of
junction will remain stationary during the movements of the springs,
because at every instant that point is drawn by equal and opposite
forces. If _three_, _four_, or _five_ spiral springs are joined in a
similar manner, we may conceive them all vibrating between their nodes
in the same manner.
Upon the very same principles we may conceive a long column of air
without partitions dividing itself into two, three, or four smaller
columns, each of which will vibrate between its nodes in the same
manner as the spiral spring. At the middle point of each small
vibrating column, the air will be of its natural density, like that
of the atmosphere; while at the nodes B, &c. it will be in a state of
condensation and rarefaction alternately.
If, when the air is vibrating in one column in the pipe AB, as in Fig.
41, No. 2, 3, we conceive a hole made in the middle, the atmospheric
air will not rush in to disturb the vibration, because the air within
the pipe and without it has exactly the same density. Nay, if, instead
of a single hole, we were to cut a ring out of the pipe at the middle
point, the column would vibrate as before. But if we bore a hole
between the middle and one of the ends, where the vibrating column
must be either in a state of condensation or rarefaction, the air must
either rush out or rush in, in order to establish the equilibrium.
The air opposite the hole will then be brought to the state of the
external air, like that in the middle of the pipe; it will become the
middle of a vibrating column: and the whole column of air, instead of
vibrating as one, will vibrate as two columns, each column vibrating
with twice the velocity, and yielding harmonic sounds along with the
fundamental sound of the whole columns, in the same manner as we have
already explained with regard to vibrating strings. By opening other
holes we may subdivide a vibrating column into any number of smaller
vibrating columns. The holes in flutes, clarionets, &c. are made for
this purpose. When they are all closed up, the air vibrates in one
column; and by opening and shutting the different holes in succession,
the number of vibrating columns is increased or diminished at pleasure,
and consequently the harmonic sounds will vary in a similar manner.
Curious as these phenomena are, they are still surpassed by those
which are exhibited during the vibration of solid bodies. A rod or
bar of metal or glass may be made to vibrate either longitudinally or
laterally.
An iron rod will vibrate longitudinally, like a column of air, if we
strike it at one end in the direction of its length; or rub it in
the same direction with a wetted finger, and it will admit the same
fundamental note as a column of air _ten_ or _eleven_ times as long,
because sound moves so much faster in iron than in air. When the
iron rod is thus vibrating along its length, the very same changes
which we have shown in Fig. 41, as produced in a spiral spring, or
in a column of air, take place in the solid metal. All its particles
move alternately towards A and towards B, the metal being in the one
case condensed at the end to which the particles move, and expanded
at the end from which they move, and retaining its natural density
in the middle of the rod. If we now hold this rod in the middle, by
the finger and thumb lightly applied, and rub it in the middle either
of AB or BC with a piece of cloth sprinkled with powdered rosin,
or with a well-rosined fiddle-bow drawn across the rod, it will
divide itself into two vibrating portions AB, BC, each of which will
vibrate, as shown in Fig. 42, like the two adjacent columns of air,
the section of the rod, or the particles which compose that section
at B, being at perfect rest. By holding the rod at any intermediate
point between A and B, so that the distance from A to the finger and
thumb is one-third, one-fourth, one-fifth, &c. of the whole length AC,
and rubbing one of the divisions in the middle, the rod will divide
itself into 3, 4, 5, &c. vibrating portions, and give out corresponding
harmonic sounds.
[Illustration: _Fig. 43._]
A rod of iron may be made to vibrate laterally or transversely, by
fixing one end of it firmly, as in a vice, and leaving the other free,
or by having both ends free or both fixed. When a rod, fixed at one
end and free at the other, is made to vibrate, its mode of vibrating
may be rendered evident to the eye; and for the purpose of doing
this, Mr. Wheatstone has contrived a curious instrument, called the
_Kaleidophone_, which is shown in Fig. 43. It consists of a circular
base of wood AB, about _nine_ inches in diameter and one inch thick,
and having four brass sockets firmly fixed into it at C, D, E, and F.
Into these sockets are screwed four vertical steel rods C, D, E, and
F, about thirteen or fourteen inches long; one being a square rod,
another a bent cylindrical one, and the other two cylindrical ones of
different diameters. On the extremities of these rods are fixed small
quicksilvered glass beads, either singly or in groups, so that when
the instrument is placed in the light of the sun or in that of a lamp,
bright images of the sun or flame are seen reflected on each bead. If
any of these rods is set vibrating, these luminous images will form
continuous and returning curve lines in a state of constant variation,
each different rod giving curves of different characters, as shown in
Fig. 44.
[Illustration: _Fig. 44._]
The Melodion, an instrument of great power, embracing five octaves,
operates by means of the vibrations of metallic rods of unequal
lengths, fixed at one end and free at the other.[19] A narrow and thin
plate of copper is screwed to the free extremity of each rod, and at
right angles to its length; and its surface is covered with a small
piece of felt, impregnated with rosin. This narrow band is placed near
the circumference of a revolving cylinder, and, by touching the key,
it is made to descend till it touches the revolving cylinder, and
gives out its sound. The sweetness and power of this instrument are
unrivalled; and such is the character of its tones, that persons of a
nervous temperament are often entirely overpowered by its effects.
[19] See _Edinburgh Encyclopædia_, Art. SCIENCE, Curiosities in, Vol.
xvii., p. 563.
The vibrations of plates of metal or glass of various forms exhibit
a series of the most extraordinary phenomena, which are capable of
being shown by very simple means. These phenomena are displayed in an
infinite variety of regular figures assumed by sand or fine lycopodium
powder, strewed over the surface of the glass plate. In order to
produce these figures, we must pinch or damp the plate at one or more
places, and when the sand is strewed upon its surface, it is thrown
into vibrations by drawing a fiddle-bow over different parts of its
circumference. The method of damping or pinching plates is shown in
Fig. 45. In No. 1, a square plate of glass AB, ground smooth at its
edges, is pinched by the finger and thumb. In No. 2, a circular plate
is held by the thumb against the top _c_ of a perpendicular rod, and
damped by the fingers at two different points of its circumference.
In No. 3 it is damped at three points of its circumference; _c_ and
_d_ by the thumb and finger, and at _e_ by pressing it against a fixed
obstacle _a b_. By means of a clamp like that at No. 4, it may be
damped at a greater number of points.
[Illustration: _Fig. 45._
N^o 1 N^o 2
N^o 3 N^o 4
]
[Illustration: _Fig. 46._
N^o 1 N^o 2
N^o 3 N^o 4
]
If we take a _square_ plate of glass, such as that shown in Fig. 46,
No. 1, and, pinching it at its centre, draw the fiddle-bow near one of
its angles, the sand will accumulate in the form of a cross, as shown
in the figure, being thrown off the parts of the plate that are in a
state of vibration, and settling in the nodes or parts which are at
rest. If the bow is drawn across the middle of one of the edges, the
sand will accumulate as in No. 2. If the plate is pinched at N, No. 3,
and the bow applied at F and perpendicular to AB, the sand will arrange
itself in three parallel lines, perpendicular to a fourth passing
through F and N. But if the point N, where it is pinched, is a little
farther from the edge than in No. 3, the parallel lines will change
into curves as in No. 4.
If the plate of glass is circular, and pinched at its centre, and also
at a point of its circumference, and if the bow is applied at a point
45° from the last point, the figure of the sand will be as in Fig. 47,
No. 1. If with the same plate, similarly pinched, the bow is drawn over
a part 30° from the pinched point of the circumference, the sand will
form six radii as in No. 2. When the centre of the plate is left free,
a different set of figures is produced, as shown in No. 3 and No. 4.
When the plate is pinched near its edge, and the bow applied 45° from
the point pinched, a circle of sand will pass through that point, and
two diameters of sand, at right angles to each other, will be formed as
in No. 3. When a point of the circumference is pressed against a fixed
obstacle, and the bow applied 30° from that point, the figure in No. 4
is produced.
[Illustration: _Fig. 47._
No. 1. No. 2.
No. 3. No. 4.]
If, in place of a solid plate, we strew the sand over a stretched
membrane, the sand will form itself into figures, even when the
vibrations are communicated to the membrane through the air. In order
to make these experiments, we must stretch a thin sheet of wet paper,
such as vegetable paper, over the mouth of a tumbler-glass with a
footstalk, and fix it to the edges with glue. When the paper is dry, a
thin layer of dry sand is strewed upon its surface. If we place this
membrane upon a table, and hold immediately above it, and parallel
to the membrane, a plate of glass vibrating so as to give any of the
figures shown in Fig. 47, the sand upon the membrane will imitate
exactly the figure upon the glass. If the glass plate, in place of
vibrating horizontally, is made to vibrate in an inclined position, the
figures on the membrane will change with the inclination, and the sand
will assume the most curious arrangements. The figures thus produced
vary with the size of the membrane, with its material, its tension, and
its shape. When the same figure occurs several times in succession, a
breath upon the paper will change its degree of tension, and produce
an entirely new figure, which, as the temporary moisture evaporates,
will return to the original figure, through a number of intermediate
ones. The pipe of an organ at the distance of a few feet, or the notes
of a flute at the distance of half a foot, will arrange the sand on the
membrane into figures which perpetually change with the sound that is
produced.
The manner in which flat rulers and cylinders of glass perform their
vibrations is very remarkable. If a glass plate about twenty-seven
inches long, six-tenths of an inch broad, and six hundredths of an
inch thick, is held by the edges between the finger and thumb, and has
its lower surface, near either end, rubbed with a piece of wet cloth,
sand laid upon its upper surface will arrange itself in parallel lines
at right angles to the length of the plate. If the place of these lines
is marked with a dot of ink, and the other side of the glass ruler is
turned upwards, and the ruler made to vibrate as before, the sand will
now accumulate in lines intermediate between the former lines, so that
the motions of one-half the thickness of the glass ruler are precisely
the reverse of those of the corresponding parts of the other half.
As these singular phenomena have not yet been made available by the
scientific conjuror, we must be satisfied with this brief notice of
them; but there is still one property of sound, which has its analogy
also in light, too remarkable to be passed without notice. This
property has more of the marvellous in it than any result within the
wide range of the sciences. _Two loud sounds may be made to produce
silence, and two strong lights may be made to produce darkness!_
If two equal and similar strings, or the columns of air in two equal
and similar pipes, perform exactly 100 vibrations in a second,
they will produce each equal waves of sound, and these waves will
conspire in generating an uninterrupted sound, double of either of
the sounds, heard separately. If the two strings or the two columns
of air are not in unison, but nearly so, as in the case where the
one vibrates 100 and the other 101 times in a second, then at the
first vibration the two sounds will form one of double the strength
of either; but the one will gradually gain upon the other, till at
the fiftieth vibration it has gained half a vibration on the other.
At this instant the two sounds will _destroy one another_, and an
interval of perfect silence will take place. The sound will instantly
commence, and gradually increase till it becomes loudest at the
hundredth vibration, where the two vibrations conspire in producing
a sound double of either. An interval of silence will again occur at
the 150th, 250th, 350th vibration, or every second, while a sound of
double the strength of either will be heard at the 200th, 300th, and
400th vibration. When the unison is very defective, or when there is
a great difference between the number of vibrations which the two
strings or columns of air perform in a second, the successive sounds
and intervals of silence resemble a rattle. With a powerful organ, the
effect of this experiment is very fine, the repetition of the sounds
_wow_--_wow_--_wow_--representing the double sound and the interval
of silence which arise from the total extinction of the two separate
sounds.
The phenomenon corresponding to this in the case of light is perhaps
still more surprising. If a beam of _red_ light issues from a luminous
point, and falls upon the retina, we shall see distinctly the luminous
object from which it proceeds; but if another pencil of red light
issues from another luminous point, anyhow situated, provided the
difference between its distance and that of the other luminous point
from the point of the retina, on which the first beam fell, is the
258th thousandth part of an inch, or exactly _twice_, _thrice_, _four_
times, &c., that distance; and if this second beam falls upon the
same point of the retina, the one light will increase the intensity
of the other, and the eye will see _twice_ as much light as when it
received only one of the beams separately. All this is nothing more
than what might be expected from our ordinary experience. But if
the difference in the distances of the two luminous points is only
_one-half_ of the 258th thousandth part of an inch, or 1½, 2½, 3½,
4½, times that distance, _the one light will extinguish the other and
produce absolute darkness_. If the two luminous points are so situated,
that the difference of their distances from the point of the retina is
intermediate between 1 and 1½, or 2 and 2½, above the 258th thousandth
part of an inch, the intensity of the effect which they produce will
vary from absolute darkness to double the intensity of either light. At
1¼, 2¼, 3¼ times, &c., the 258th thousandth of an inch, the intensity
of the two combined lights will be equal only to one of them acting
singly. If the lights, in place of falling upon the retina, fall upon
a sheet of white paper, the very same effect will be produced, a black
spot being produced in the one case, and a bright white one in the
other, and intermediate degrees of brightness in intermediate cases. If
the two lights are _violet_, the difference of distances at which the
preceding phenomena will be produced will be the 157th thousandth part
of an inch, and it will be intermediate between the 258th and the 157th
thousandth part of an inch for the intermediate colours. This curious
phenomenon may be easily shown to the eye, by admitting the sun’s light
into a dark room through a small hole about the 40th or 50th part of
an inch in diameter, and receiving the light on a sheet of paper. If
we hold a needle or piece of slender wire in this light, and examine
its shadow, we shall find that the shadow consists of bright and dark
stripes succeeding each other alternately, the stripe in the very
middle or axis of the shadow being a bright one. The rays of light
which are bent into the shadow, and which meet in the very middle of
the shadow, have exactly the same length of path, so that they form a
bright fringe of double the intensity of either; but the rays which
fall upon a point of the shadow at a certain distance from the middle,
have a difference in the length of their paths, corresponding to the
difference at which the lights destroy each other, so that a _black_
stripe is produced on each side of the middle bright one. At a greater
distance from the middle, the difference becomes such as to produce a
bright stripe, and so on, a bright and a dark stripe succeeding each
other to the margin of the shadow.
The explanation which philosophers have given of these strange
phenomena is very satisfactory, and may be easily understood. When a
wave is made on the surface of a still pool of water, by plunging a
stone into it, the wave advances along the surface, while the water
itself is never carried forward, but merely rises into a height and
falls into a hollow, each portion of the surface experiencing an
elevation and a depression in its turn. If we suppose two waves equal
and similar to be produced by two separate stones, and if they reach
the same spot at the same time, that is, if the two elevations should
exactly coincide, they would unite their effects, and produce a
wave twice the size of either; but if the one wave should be just so
far before the other, that the hollow of the one coincided with the
elevation of the other, and the elevation of the one with the hollow
of the other, the two waves would obliterate or destroy one another,
the elevation as it were of the one filling up half the hollow of the
other, and the hollow of the one taking away half the elevation of the
other, so as to reduce the surface to a level. These effects will be
actually exhibited by throwing two equal stones into a pool of water,
and it will be seen that there are certain lines of a hyperbolic form
where the water is quite smooth, in consequence of the equal waves
obliterating one another, while, in other adjacent parts, the water is
raised to a height corresponding to both the waves united.
In the tides of the ocean we have a fine example of the same principle.
The two immense waves arising from the action of the sun and moon upon
the ocean produce our spring-tides by their combination, or when the
elevations of each coincide; and our neap-tides, when the elevation of
the one wave coincides with the depression of the other. If the sun and
moon had exerted exactly the same force upon the ocean, or produced
tide waves of the same size, then our neap-tides would have disappeared
altogether, and the spring-tide would have been a wave double of the
wave produced by the sun and moon separately. An example of the effect
of the equality of the two waves occurs in the port of Batsha, where
the two waves arrive by channels of different lengths, and actually
obliterate each other.
Now, as sound is produced by undulations or waves in the air, and
as light is supposed to be produced by waves or undulations in an
ethereal medium, filling all nature, and occupying the pores of
transparent bodies, the successive production of sound and silence by
two loud sounds, or of light and darkness by two bright lights, may be
explained in the very same manner as we have explained the increase
and the obliteration of waves formed on the surface of water. If this
theory of light be correct, then the breadth of a wave of _red_ light
will be the 258th thousandth part of an inch, the breadth of a wave of
green light the 207th thousandth part of an inch, and the breadth of a
wave of violet light the 157th thousandth part of an inch.
Among the wonders of modern skill, we must enumerate those beautiful
automata by which the motions and actions of man and other animals have
been successfully imitated. I shall therefore describe at present some
of the most remarkable acoustic automata, in which the production of
musical and vocal sounds has been the principal object of the artist.
Many very ingenious pieces of acoustic mechanism have been from time to
time exhibited in Europe. The celebrated Swiss mechanist, M. le Droz,
constructed for the King of Spain the figure of a sheep, which imitated
in the most perfect manner the bleating of that animal; and likewise
the figure of a dog watching a basket of fruit, which, when any of the
fruit was taken away, never ceased barking till it was replaced.
The singing-bird of M. Maillardet, which he exhibited in Edinburgh
many years ago, is still more wonderful.[20] An oval box, about three
inches long, was set upon the table, and in an instant the lid flew up,
and a bird of the size of the humming-bird, and of the most beautiful
plumage, started from its nest. After fluttering its wings, it opened
its bill and performed four different kinds of the most beautiful
warbling. It then darted down into its nest, and the lid closed upon
it. The moving power in this piece of mechanism is said to have been
springs which continued their action only four minutes. As there was
no room within so small a figure for accommodating pipes to produce
the great variety of notes which were warbled, the artist used only
one tube, and produced all the variety of sounds by shortening and
lengthening it with a moveable piston.
[20] A similar piece of mechanism had been previously made by M. le
Droz.
Ingenious as these pieces of mechanism are, they sink into
insignificance when compared with the machinery of M. Vaucanson, which
had previously astonished all Europe. His two principal automata were
the flute-player, and the pipe and tabor-player. The flute-player
was completed in 1736, and wherever it was exhibited it produced the
greatest sensation. When it came to Paris it was received with great
suspicion. The French savants recollected the story of M. Raisin,
the organist of Troyes, who exhibited an automaton player upon the
harpsichord, which astonished the French court by the variety of
its powers. The curiosity of the king could not be restrained, and
in consequence of his insisting upon examining the mechanism, there
was found in the figure a pretty little musician five years of age.
It was natural, therefore, that a similar piece of mechanism should
be received with some distrust; but this feeling was soon removed
by M. Vaucanson, who exhibited and explained to a committee of the
Academy of Sciences the whole of the mechanism. This learned body
was astonished at the ingenuity which it displayed; and they did not
hesitate to state, that the machinery employed for producing the sounds
of the flute performed in the most exact manner the very operations
of the most expert flute-player, and that the artist had imitated the
effects produced, and the means employed by nature, with an accuracy
which exceeded all expectation. In 1738, M. Vaucanson published a
memoir, approved of by the Academy, in which he gave a full description
of the machinery employed, and of the principles of its construction.
Following this memoir, I shall therefore attempt to give as popular a
description of the automaton as can be done without lengthened details
and numerous figures.
The body of the flute-player was about 5½ feet high, and was placed
upon a piece of rock, surrounding a square pedestal 4½ feet high by 3½
feet wide. When the panel which formed the front of the pedestal was
opened, there was seen on the right a clock movement, which, by the
aid of several wheels, gave a rotatory motion to a steel axis about
2½ feet long, having cranks at six equidistant points of its length,
but lying in different directions. To each crank was attached a cord,
which descended and was fixed by its other end to the upper board of a
pair of bellows, 2½ feet long and 6 inches wide. Six pair of bellows
arranged along the bottom of the pedestal were then wrought, or made to
blow in succession, by turning the steel axis.
At the upper face of the pedestal, and upon each pair of bellows is a
double pulley, one of whose rims is 3 inches in diameter, and the other
1½. The cord which proceeds from the crank coils round the smaller
of these pulleys, and that which is fixed to the upper board of the
bellows goes round the larger pulley. By this means the upper board of
the bellows is made to rise higher than if the cords went directly from
them to the cranks.
Round the larger rims of three of these pulleys, viz. those on the
right hand, there are coiled three cords, which, by means of several
smaller pulleys, terminate in the upper boards of other three pair of
bellows placed on the top of the box.
The tension of each cord when it begins to raise the board of the
bellows to which it is attached, gives motion to a lever placed above
it between the axis and the double pulley in the middle and lower
region of the box. The other end of this lever keeps open the valve in
the lower board of the bellows, and allows the air to enter freely,
while the upper board is rising to increase the capacity of the
bellows. By this means there is not only power gained, in so far as the
air gains easier admission through the valve, but the fluttering noise
produced by the action of the air upon the valves is entirely avoided,
and the nine pair of bellows are wrought with great ease, and without
any concussion or noise.
These nine bellows discharge their wind into three different and
separate tubes. Each tube receives the wind of three bellows, the upper
boards of one of the three pair being loaded with a weight of four
pounds, those of the second three pair with a weight of two pounds,
and those of the other three pair with no weight at all. These three
tubes ascended through the body of the figure and terminated in three
small reservoirs placed in its trunk. These reservoirs were thus united
into one, which, ascending into the throat, formed by its enlargement
the cavity of the mouth terminated by two small lips, which rested
upon the whole of the flute. These lips had the power of opening more
or less, and by a particular mechanism, they could advance or recede
from the hole in the flute. Within the cavity of the mouth there is a
small moveable tongue for opening and shutting the passage for the wind
through the lips of the figure.
The motions of the fingers, lips, and tongue of the figure were
produced by means of a revolving cylinder, thirty inches long and
twenty-one in diameter. By means of pegs and brass staples fixed in
fifteen different divisions in its circumference, fifteen different
levers, similar to those in a barrel organ, were raised and depressed.
Seven of these regulated the motions of the seven fingers for stopping
the holes of the flute, which they did by means of steel chains rising
through the body, and directed by pulleys to the shoulder, elbow, and
fingers. Other three of the levers communicating with the valves of the
three reservoirs, regulated the ingress of the air, so as to produce a
stronger or a weaker tone. Another lever opened the lips so as to give
a free passage to the air, and another contracted them for the opposite
purpose. A third lever drew them backwards from the orifice of the
flute, and a fourth pushed them forward. The remaining lever enabled
the tongue to stop up the orifice of the flute.
Such is a very brief view of the general mechanism by which the
requisite motions of the flute-player were produced. The airs which it
played were probably equal to those executed by a living performer, and
its construction, as well as its performances, continued for many years
to delight and astonish the philosophers and musicians of Europe.
Encouraged by the success of this machine, M. Vaucanson exhibited in
1741 other automata, which were equally, if not more, admired. One of
these was the automaton duck, which performed all the motions of that
animal, and not only ate its food, but digested it;[21] and the other
was his pipe and tabor-player, a piece of mechanism which required
all the resources of his fertile genius. Having begun this machine
before he was aware of its peculiar difficulties, he was often about
to abandon it in despair, but his patience and his ingenuity combined,
enabled him not only to surmount every difficulty, but to construct an
automaton which performed complete airs, and greatly excelled the most
esteemed performers on the pipe and tabor.
[21] See Letter XI.
The figure stands on a pedestal, and is dressed like a dancing
shepherd. He holds in one hand a flageolet, and in the other the stick
with which he beats the tambourine as an accompaniment to the airs of
the flageolet, about twenty of which it is capable of performing. The
flageolet has only three holes, and the variety of its tones depends
principally on a proper variation of the force of the wind, and on the
different degrees with which the orifices are covered. These variations
in the force of the wind required to be given with a rapidity which
the ear can scarcely follow, and the articulation of the tongue was
required for the quickest notes, otherwise the effect was far from
agreeable. As the human tongue is not capable of giving the requisite
articulations to a rapid succession of notes, and generally slurs
over one-half of them, the automaton was thus able to excel the best
performers, as it played complete airs with articulations of the tongue
at every note.
In constructing this machine, M. Vaucanson observed that the flageolet
must be a most fatiguing instrument for the human lungs, as the muscles
of the chest must make an effort equal to fifty-six pounds in order to
produce the highest notes. A single ounce was sufficient for the lowest
notes: so that we may, from this circumstance, form an idea of the
variety of intermediate effects required to be produced.
While M. Vaucanson was engaged in the construction of these wonderful
machines, his mind was filled with the strange idea of constructing
an automaton containing the whole mechanism of the circulation of
the blood. From some birds which he made, he was satisfied of its
practicability; but as the whole vascular system required to be made
of elastic gum or caoutchouc, it was supposed that it could only be
executed in the country where the caoutchouc tree was indigenous.
Louis XVI. took a deep interest in the execution of this machine.
It was agreed that a skilful anatomist should proceed to Guiana to
superintend the construction of the blood-vessels, and the king
had not only approved of, but had given orders for, the voyage.
Difficulties, however, were thrown in the way, Vaucanson became
disgusted, and the scheme was abandoned.
The two automata which we have described were purchased by Professor
Bayreuss of Helmstadt; but we have not been able to learn whether or
not they still exist.
[Illustration: _Fig. 48._]
Towards the end of the eighteenth century a bold and almost successful
attempt was made to construct a _talking automaton_. In the year 1779,
the Imperial Academy of Sciences at St. Petersburgh proposed, as the
subject of one of their annual prizes, an inquiry into the nature
of the vowel sounds, A, E, I, O, and U, and the construction of an
instrument for artificially imitating them. This prize was gained by
M. Kratzenstein, who showed that all the vowels could be distinctly
pronounced by blowing through a reed into the lower ends of the pipes
of the annexed figures, as shown in Fig. 48, where the corresponding
vowels are marked on the different pipes. The vowel I is pronounced by
merely blowing into the pipe _a b_, of the pipe marked I, without the
use of a reed.
[Illustration: _Fig. 49._]
About the same time that Kratzenstein was engaged in these researches,
M. Kempelen of Vienna, a celebrated mechanician, was occupied with the
same subject. In his first attempt he produced the vowel sounds, by
adapting a reed R, Fig. 49, to the bottom of a funnel-shaped cavity
A B, and placing his hand in various positions within the funnel.
This contrivance, however, was not fitted for his purpose, but after
long study, and a diligent examination of the organs of speech, he
contrived a hollow oval box, divided into two portions attached by a
hinge so as to resemble jaws. This box received the sound which issued
from the tube connected with the reed, and by opening and closing the
jaws, he produced the sounds, A, O, OU, and an imperfect E, but no
indications of an I. After two years’ labour he succeeded in obtaining
from different jaws the sounds of the consonants P, M, L, and by means
of these vowels and consonants, he could compose syllables and words,
such as _mama_, _papa_, _aula_, _lama_, _mulo_. The sounds of two
adjacent letters, however, ran into each other, and an aspiration
followed some of the consonants; so that, instead of _papa_, the word
sounded _phaa-ph-a_; these difficulties he contrived with much labour
to surmount, and he found it necessary to imitate the human organs of
speech by having only one mouth and one glottis. The mouth consisted
of a funnel, or bell-shaped piece of elastic gum, which approximated,
by its physical properties, to the softness and flexibility of the
human organs.[22] To the mouth-piece was added a nose made of two tin
tubes, which communicated with the mouth. When both these tubes were
open, and the mouth-piece closed, a perfect M was produced; and when
one was closed and the other open, an N was sounded. M. Kempelen could
have succeeded in obtaining the four letters D, G, K, T, but, by using
a P instead of them, and modifying the sound in a particular manner,
he contrived to deceive the ear by a tolerable resemblance of these
letters.
[22] Had M. Kempelen known the modern discovery of giving glue any
degree of softness, by mixing it with molasses or sugar, which is
always absorbing moisture from the atmosphere, he might have obtained
a still more perfect imitation of the human organs.
There seems to be no doubt that he at last was able to produce entire
words and sentences, such as _opera_, _astronomy_, _Constantinopolis_,
_Vous êtes mon ami, Je vous aime de tout mon cœur, Venez avec moi à
Paris, Leopoldus secundus, Romanorum imperator semper Augustus_, &c.,
but he never fitted up a speaking figure; and probably, from being
dissatisfied with the general result of his labours, he exhibited only
to his private friends the effects of the apparatus, which was fitted
up in the form of a box.
This box was rectangular, and about three feet long, and was placed
upon a table, and covered with a cloth. When any particular word was
mentioned by the company, M. Kempelen caused the machine to pronounce
it, by introducing his hands beneath the cloth, and apparently giving
motion to some parts of the apparatus. Mr. Thomas Collinson, who had
seen this machine in London, mentions, in a letter to Dr. Hutton, that
he afterwards saw it at M. Kempelen’s own house in Vienna, and that he
then gave it the same word to be pronounced which he gave it in London,
viz. the word _Exploitation_, which, he assures us, it again distinctly
pronounced with the French accent.
M. Kratzenstein seems to have been equally unsuccessful; for though he
assured M. de Lalande, when he saw him in Paris, in 1786, that he had
made a machine which could speak pretty well, and though he showed him
some of the apparatus by which it could sound the vowels, and even such
syllables as _papa_ and _mama_, yet there is no reason to believe that
he had accomplished more than this.
The labours of Kratzenstein and Kempelen have been recently pursued
with great success by our ingenious countryman, Mr. Willis, of
Cambridge. In repeating Kempelen’s experiment, shown in Fig. 49, he
used a shallower cavity, such as that in Fig. 50, and found that he
could entirely dispense with the introduction of the hand, and could
obtain the whole series of vowels by sliding a flat board C D over the
mouth of the cavity. Mr. Willis then conceived the idea of adapting to
the reed cylindrical tubes, whose length could be varied by sliding
joints. When the tube was greatly less than the length of a stopped
pipe in unison with the reed, it sounded I, and by increasing the
length of the tube, it gave E, A, O, and U, in succession. But what was
very unexpected, when the tube was so much lengthened as to be 1½ times
the length of a stopped pipe in unison with the reed, the vowels began
to be again sounded in an inverted order, viz. U, O, A, E, and then
again in a direct order, I, E, A, O, U, when the length of the tube was
equal to twice that of a stopped pipe, in unison with the reed.
[Illustration: _Fig. 50._]
Some important discoveries have been recently made by M. Savart
respecting the mechanism of the human voice;[23] and we have no doubt
that, before another century is completed, a _Talking_ and a _Singing
machine_ will be numbered among the conquests of Science.
[23] See _Edinburgh Journal of Science_, No. viii., p. 200.