present day, the lower corresponds with 264 complete vibrations per
second, the higher with 528. It will be observed, too, that all the
harmonies are determined by some simple ratio in the rates of vibration:
the interval of the _fourth_ is 3, 4; that of the _fifth_ is 2, 3, etc.
Another easily discoverable fact is that the loudness of the sound
depends upon the amplitude of the vibrations. This is sufficiently
obvious by a few experiments with a tuning fork; and by close
examination of such tracings as have been mentioned, we shall soon
become aware of another circumstance—namely, that the vibrations not
simple, but that the larger or general movement has one or more sets of
small vibrations within it. In Fig. 319_a_, A is the curve that would be
traced by the tuning-fork in a state of simple vibration; B and C are
tracing such as are given by a fork in two of its modes of vibration.
The fork gives out its proper or fundamental note in both cases; but the
ear recognizes a difference in the quality of the sound due to the
smaller and more numerous vibrations. Differences of the same kind are
recognized in the notes produced by different musical instruments; but
these are usually more complicated, and their forms are characteristic
of the particular quality of the tone, which is thus shown to be due to
the superposing of several related systems of vibration upon the
fundamental one. Thus three out of the four qualities of sound
recognized by the ear have had their physical causes assigned. As for
the fourth—namely, the distinction we perceive among the different
vowels sung on the same note—it has a physical origin identical with the
last. For since parts of the vocal organs assume different positions in
enunciating the different vowels, they constitute for the time being so
many varied musical instruments, and the graphical traces of the sounds
(for they can be obtained) show a corresponding modification. Here, in
Fig. 319_b_, for example, are represented the tracings of the vibrations
given to the air in various vowel sounds. It is also through the
vibrations conveyed by the air to the little membrane called the drum of
the ear that the sensations of sound are received, and of the nature of
these vibrations a few words must be said presently. In considering the
different qualities of sound, we have so far confined ourselves to
sustained musical notes, as, for instance, the vowel sounds in singing.
This has been done to show the relations of rapidity of vibration to
pitch and for simplicity of illustration of the superposition of
vibrations, etc. Two other remarks must be added—viz., that the
vibrations of musical tones are _isochronous_—that is, whether the note
be loud or soft, the same time is taken up in each vibration
corresponding with the same fundamental note. Other vocal sounds than
sustained vowel notes are found to be due to still more complicated
combinations of vibrations of shorter duration, and _noises_, as
distinguished from musical sound, are formed also by the superposition
of a greater or less number of systems of vibrations, the rapidities of
which are wanting in harmonic relations such as we have pointed out
belong to the musical scale. Even in noises, however, there is often one
or more predominant systems of vibrations which a musical ear can
detect. If the reader will hold a pencil or penholder at one end and tap
with it on the edge of the table, passing in quick succession to parts
progressively nearer where the pencil is held, he will hardly fail to
recognize a rising pitch in the little noises.
[Illustration:
FIG. 319_a_.—_Traces of Vibrations of a Tuning-Fork._
]
[Illustration:
FIG. 319_b_.—_Phonautographic Tracings of Different Vowel Sounds._
]
[Illustration:
FIG. 319_c_.—_Diagram._
]
[Illustration:
FIG. 319_d_.—_Phases of Sound Waves._
]
A word or two must be said as to the way in which sound is transmitted
through the air. This progression is commonly spoken of as a wave
motion, but it must not be thought of as taking place in the form
familiar to us as waves on water; still less must the reader confound it
with the sinuous lines shown in the graphical representations of
vibrations given in the figures. It is rather a series of rapid
pulsations of the particles of the air taking place in the direction in
which the sound is propagated, and resembling waves on water only by
presenting periodical phases in uniform succession. The difference may
be illustrated from what may be seen in a field of wheat when the wind
is blowing over it. The stalks bend down, and rise again when the breeze
has passed, and thus the general appearance of the waves of the sea is
produced. If we confine our attention, however, to the motion of the
several ears of the wheat in a file of stalks, we shall obtain a clearer
notion of what takes place in the so-called waves of sound. The
positions of the stalks at some one instant of time may be represented
by the diagram, Fig. 319_c_. Each stalk is swinging backwards and
forwards like an inverted pendulum, and the successive phases of these
vibrations bring the adjacent ears nearest to each other about _i_, and
farthest apart at _a_ and _a´_. The places of these, and of all the
intermediate degrees of approximation and retreat, pass along the file.
Instead of the ears of wheat swinging on their elastic stalks, suppose
particles of air approaching and receding by virtue of the elasticity by
which they resist compression and recover from it, and you will obtain
an elementary idea of what takes place in the transmission of sound.
Fig. 319_d_ is a picture of a column of air acted upon by a tuning-fork.
The swiftly advancing prong is compressing the air in front of it, and
in swinging back it will tend to leave a vacuum behind it by which the
air is partially rarefied; and these alternate condensations and
rarefactions will travel along through the air by virtue of its
elasticity, and the mechanical action by which they are able to agitate
a stretched membrane (or other elastic body), so that its vibrations
will correspond with them in period and magnitude, may be easily
understood. The vibration produced is a simple one, but any number of
other systems may pass at the same time, and each one will be propagated
as if the rest did not exist, just as we may see different systems of
undulations moving on the surface of water. It should be observed that
the velocity of propagation is the same whatever may be the period or
the magnitude of the vibrations. The high and the low, the loud and the
soft notes of a piece of music played at a distance, all take the same
time in reaching the ear. Light as are the particles of air, the
mechanical actions which a number of them carrying strong vibratory
impulses will produce, may be illustrated by the rattling of window
panes by a loud peal of thunder, and may be bodily felt by a person
standing close to a very large bell while the hour is striking.
We have referred to instruments for registering sound, and even vocal
sounds, before anything has been said of the construction of the
phonograph, and it is, in fact, many years since the problem was solved
of recording the vibrations produced by speech. Mr. Leo Scott, in 1856,
invented an instrument, called the _Phonautograph_, which did this. It
consisted of a cone of sheet zinc like a large ear-trumpet, across the
smaller end of which was stretched a membrane, having attached to it a
very light style, which left a record of the vibrations of the membrane
on a blackened cylinder properly disposed to receive the tracing. When
any sound was produced near the open end of the cone, the impulses
reflected from its internal surface were concentrated on the membrane,
throwing it into corresponding vibrations. Now, this process could be
reversed if the tracing could be made to give back again to the style
its original movements, these transferred to the membrane would throw
the air within the cone into corresponding vibrations, and the sounds
that gave rise to the tracing would be reproduced. Yet Mr. Scott seems
to have suggested no such possibilities for his instrument; but a few
years after the invention of the phonautograph, M. Cros deposited at the
Academy of Sciences in Paris a sealed paper, which was opened after Mr.
Edison had patented the phonograph (1877), and found to contain
suggestions of how this might be done, but describing no experiments in
which any approach had been made towards realizing the conditions laid
down. To Mr. Edison belongs the honour of solving the problem by the
invention of the phonograph, which was patented by him in 1877. The
device which he happily hit upon for converting the phonautograph into a
phonograph was very simple in principle, and consisting merely in
substituting a sheet of tinfoil for the blackened paper in Scott’s
apparatus, the mechanism required for reproducing articulate human
speech was thus found, contrary to all expectations that had previously
been entertained, to be essentially of a remarkably simple character,
for the arrangement of the parts was even more direct than in the
phonautograph itself. This is not derogatory to the merit of the
inventor, for every invention depends upon something previously
attained, and the discovery of suitable materials for the various parts
of the machine, and the many delicate adjustments of their forms and
disposition to secure the required object, demanded the application of
very remarkable experimental skill. The phonograph differs from the
phonautograph by giving up what it has registered in the original form
and material, and thus it is a speaking machine. It is a speaking
machine which _reproduces_ articulate speech, not produces it. Much
ingenuity has been devoted to the construction of speaking machines
which should be capable of _producing_ the sounds of the human voice. By
throwing into vibration the air contained in cavities of certain shapes,
it was long ago found possible to produce sounds closely resembling
those of a voice singing particular vowels, and a real speaking machine
that could articulate words was exhibited in America before the
phonograph had been brought out. It was constructed by Mr. Faber, and
formed a very complicated arrangement, in which all the organs of human
speech were imitated. There were bellows acting like the lungs; a larynx
with various diaphragms, a mouth with movable tongue and lips, and a
tube to resemble the cavity of the nose. The positions and connections
of these parts were determined by levers acted from a key-board, like
that of a piano, and by certain pedals. By moving these in proper order,
the machine pronounced words distinctly enough, but in a strange
drawling tone. So like, however, were the sounds to those of the human
voice, that some accused the exhibitors of imposition, and unjustly
credited ventriloquism instead of mechanism with the results. It will be
observed that it is the function of the phonograph to reproduce, not
produce, human speech, and the mechanical arrangements of the instrument
are simplicity itself compared with Faber’s speaking machine.
[Illustration:
FIG. 319_e_.—_Edison’s Original Phonograph._
]
[Illustration:
FIG. 319_f_.—_Diagrammatic Section of Phonograph._
]
[Illustration:
FIG. 319_g_.—_The Graphophone._
]
Fig. 319_e_ shows the form of the phonograph as designed by Mr. Edison
in 1877. It had a brass cylinder (A) upon which a narrow helical groove
was cut, and was mounted upon an axle (B), having a narrow screw-thread
corresponding with the groove on the cylinder, and working in the
upright (C), so that when the handle was turned the cylinder revolved,
and at the same time advanced in the direction of its axis. A heavy
fly-wheel (D) was attached, in order that the rate of motion might be
nearly uniform. A sheet of tinfoil, or of very thin copper, was wrapped
round the brass cylinder, and on this metallic foil rested the steel
point attached to the vibrating diaphragm, which was mounted in the ring
(F). This point was always adjusted so as to be over the helical groove
in the cylinder, and made to touch the tinfoil with a regulated
pressure. E shows the manner of firmly supporting the diaphragm in such
a manner that it could be readily removed from the cylinder when the
latter had to be covered afresh with tinfoil, or the cylinder adjusted
for reproducing the sounds. The relation of the diaphragm and point to
the tinfoil is shown in Fig. 319_f_, which represents the apparatus in
section. The tracing point (_t_) is not attached directly to the
vibrating diaphragm, but to an adjustable spring (_s_), and interposed
between the spring and the thin metallic diaphragm is a little pad,
formed of a ring of small india-rubber tubing. When the mouthpiece (M)
is spoken into, the sound vibrations reach the diaphragm (_g g_) through
the opening (_o_), and the movements thus communicated to the point
(_t_) which indents the tinfoil to various depths, and with varying
frequency, as the handle is turned, bringing the whole length of the
groove in succession to be operated upon. When the instrument is
required to reproduce the speech so easily recorded, all that is
necessary is to allow the indentations to re-act on the point that made
them. The cylinder is re-adjusted to the tracing point at the end at
which it began, the cylinder is set in motion, and the traces made on
the tinfoil move the point up and down, the vibrating disc (_g_)
following its movements, and thus communicating to the air a system of
impulses which are the counterparts in period, force and succession of
those that originally entered at _o_. It was usual to attach a conical
mouthpiece to the ring (F) in order to concentrate the reproduced
sounds, which might then be heard in all parts of a large room. When, in
reproducing the sounds, the cylinder was turned with the same velocity
as when the words were spoken, the pitch of the voice issuing from the
instrument was the same. If it were turned quicker, the pitch was
raised; if slower, lowered. The words registered on the tinfoil could be
reproduced two or three times, but with decreasing distinctness, as the
tracings gradually become obliterated. However, the sheet could be
removed from the cylinder, and the speech reproduced at any place at any
time afterwards by means of a similar instrument, and a method of
stereotyping was proposed for preserving the records. The original
phonograph was greatly improved when well regulated clockwork was used
for imparting motion instead of the winch. Mr. Edison contrived a
modification of the machine, which made it much easier of manipulation,
by substituting for the cylinder a flat plate on which a spiral groove
was cut. The plate was turned by clockwork, while the vibrating point
was made to follow the groove from the centre to the circumference. The
phonograph in its original form reproduced speech with peculiarities of
its own. The quality was metallic, and reminded one of the intonation of
the street Punch. It will easily be understood that the disc itself must
necessarily have its own systems of vibration, and these will be further
modified by the action of all the other parts. Mr. Edison’s expectations
of the capabilities of the instrument not being realized, he turned his
attention, after several unsuccessful attempts at its improvement, to
the electric light and other subjects, at the same time declaring his
conviction that the perfection of the instrument would be but a matter
of time; in fact, within a very few years afterwards such improvements
were made on Mr. Edison’s instrument as went far to justify this
prophecy. These were the work of Dr. Chichester Bell and Mr. Tainter,
who, after long continued experiments, found in paraffin wax, with a
small admixture of some other substances, a better material for
receiving the impressions. A cutting style made to act upon this cuts
out a fine groove, the bottom of which is not a series of indentations,
but a continuous wavy curve, representing every degree of inflection the
vibrating diaphragm. In the new form of the instrument, FIG. 319_g_,
which was called the _graphophone_, to distinguish it from Edison’s, the
cylinder does not move forward: it is the diaphragm that advances
parallel to the revolving axle. The cylinder is driven by a treadle,
like a sewing-machine, and there is an ingenious arrangement by which
the speed is controlled so that it can be maintained quite uniform. The
movement of cylinder and style can be instantly arrested by touching a
button, and as readily re-started. Quite recently Mr. Edison has
returned to improving the phonograph by using rather thick, solid
cylinders of wax, which are previously prepared for use by the
instrument itself paring them down to a truly cylindrical and perfectly
uniform surface, the result being a great increase of clearness in the
speech and tones of music. Mr. Edison’s new instruments are driven by
small electro-motors, and the speed is regulated by a centrifugal
governor. It is said that these wax cylinders are capable of giving out
the same record for a thousand times without perceptible sign of
deterioration; and when the cylinders are required to receive a fresh
impression, a former one can easily be pared off. The machines can be
arranged so as to sound loud enough to be heard by a large assembly; but
the quality of the tones of speech or music is most perfect when
conveyed from the receiving chamber in front of the diaphragm to one or
both of the auditor’s ears by means of a short elastic tube. Half a
dozen persons can thus hear the record on the cylinder with such
marvellous distinctness as to be able to recognize the tones of a known
voice. The very latest form of the instrument, as it has just left Mr.
Edison’s hands, is represented in Fig. 319_h_. In this one single very
small diaphragm serves both for recording and reproducing the sounds.
This is made of extremely thin glass, to which is attached a small
projection made of celluloid, which acts on a bar that carries the
recording point. The configuration of this point is most ingenious and
peculiar, for it is, in fact, double, one part being shaped like a
gouge, which cuts into the walls of the minute depression traced on the
wax cylinder, while a style-shaped part impresses the wax with punctured
indentations. The shaping of its forms is a difficult and delicate
operation, for they are very small and are cut in sapphire. The
reproduced speech given out by this instrument is said to possess the
properties of sharpness and clearness in a remarkable degree. The
machine is provided also with a sapphire cutting edge, by which an old
record may be pared off by the very motion of the cylinder in receiving
a new one. This phonograph is put in movement by ingenious mechanical
devices, for giving uniform rotation from such motive power as may be
supplied by the foot or by water or by clockwork. This improved
instrument lays claim to practical utility, and its manufacture will, it
is stated, be shortly commenced on a large scale.
Quite recently there has been established in America a big manufactory
of phonographs in the form of a toy, which is sure to become very
popular everywhere. Here they turn out daily several hundred _real
speaking dolls_, which contain clockwork actuating a phonographic
cylinder impressed with the words of some childish story or simple
rhyme, such as “Jack and Jill,” “Mary Had a Little Lamb,” etc. Each doll
of course repeats its little tale as often as the clockwork is set
going. These toys are adapted to all nationalities; for, besides many
English, there are a number of French, German, Italian, etc., girls
employed doing nothing all day long but addressing appropriate words to
each little automaton’s waxen cylinder.
[Illustration:
FIG. 319_h_.—_Edison’s Perfected Phonograph._
]
The capabilities of the phonograph suggest some curious applications
that may be made of it. For example, the songs of a fine singer may
thus, in all their modulations, reach people in distant lands, or be
made audible to future generations. Thousands of people in England have
heard with their ears, through Mr. Edison’s instruments lately brought
over by Col. Gournaud, songs and speeches, and pieces of concerted
music, sung, said, or played in America months before. Music can be
bottled up, so to speak, without the consent of the originators; and,
indeed, it is said that an eminent _prima donna_ has applied for an
injunction to restrain certain _phonographers_ from reproducing her
vocal triumphs with their instruments. A speech of Mr. Gladstone’s,
delivered in England, has been phonographically heard in New York with
great applause. There is no reason but what, with a loud speaking
phonograph uttering an orator’s very words and tones, while
instantaneous photographs of his successive gestures and attitudes are
projected on a screen, a true and lively impression of his eloquence
might be conveyed centuries after his decease. One is almost led to
speculate as to the consequences if these nineteenth century inventions
had been antedated by a few thousand years: what stores of knowledge we
might now possess! and how pleasant it would be thus
To hear each voice we feared to hear no more!
Behold each mighty shade revealed to sight,
The Bactrian, Samian sage, and all who taught the right!
[Illustration:
FIG. 320.—_The Domestic Aquarium._
]
AQUARIA.
Under the date of May 28th, 1665, the curious gossiping diary of Samuel
Pepys contains this entry: “Thence to see my Lady Pen, where my wife and
I were shown a fine rarity; of fishes kept in a glass of water, that
will live so for ever—and finely marked they are, being foreign.” This
doubtless refers to the now well-known gold fishes, which about the time
alluded to were introduced into Europe from China, where they had
probably been for ages reared and kept in captivity, chiefly for the
sake of ornament. Perhaps the reader may be disposed to think that,
therefore, the aquarium cannot be distinctively a nineteenth century
invention, nor at all a modern invention, in principle at least; but
merely the “glass of water,” or the globe of gold fish on a larger
scale. Such a notion would be quite incorrect, for the principles which
are embodied in the modern aquarium were not recognized and applied
until quite recently. Aquatic animals kept for a period in vessels in
which the water is changed from time to time cannot be considered as
properly forming an aquarium. The beauty and value of a well-regulated
aquarium depend not merely on the opportunities it affords of studying
the habits of the animals; the spectacle it presents has a far wider
interest, as illustrating and confirming the conclusions of science
regarding certain great principles which govern the whole animal and
vegetable life of this terraqueous globe. Perhaps in the whole range of
nature nothing is more wonderful than the direct interdependence of
animal and vegetable life, and the exact balance between them, which
preserves the composition of the atmosphere unchanged. The constituents
of the atmosphere have an immediate relation to both forms of life. No
animal can live without a supply of oxygen gas, which it absorbs and
replaces by carbonic acid gas. The latter, on the other hand, is
absorbed by plants, for these, under the influence of light, decompose
the carbonic acid, returning the oxygen to the atmosphere, thus
purifying the air by again fitting it for the respiration of animals.