OSCILLATION.--UNITED STRENGTH.--THE DOME.
Connection of Oscillation with Centrifugal Force.--Equality of Time
in Oscillation.--The Spider.--The Stone and String.--Pendulum of
the Clock, and its Effect on the Machinery.--Acceleration and
Retardation.--Compensating Pendulums.--The Metronome, and its Use
in Music.--A simple Metronome.--Value of the Instrument in
War.--The Escapement, and its Connection with the Pendulum.--Mode
of Action.--Larva of Burying-beetle.--Earthworms and
Serpents.--Union is Strength.--The Hippopotamus Rope and its
Structure.--The Spider-web.--Distinction between the
Threads.--Principle of the Dome.--The Arch, and its Connection with
the Dome.--Esquimaux Huts.--Receiver of the Air-pump, and its Power
of Resistance.--The Human Skull and the Egg.--Accidental
Resemblance.--The Salad-dressing Bottle.--The Medusa, Strobila, and
Hydra.
A portion of our last chapter dealt of Centrifugal Force. We will now
proceed to another well-known power, which seems to be a variation, or
perhaps a division, of the same power. I mean the principle of
OSCILLATION, which has done so much for the present state of the world.
I mention the connection of the two principles because it is evident
that, if Oscillation were continued in one direction, it would be
converted into centrifugal force. In fact, it can only be considered as
centrifugal force interrupted.
The chief point in this subject is the equal time occupied by the
oscillating body, no matter what may be the “arc” distance through which
it sways, provided that the length of the line remains the same. The
discovery of this principle by Galileo in a church at Florence is too
well known to need repetition.
This principle may be observed by any one, and at almost any time. The
Spider at the end of its line illustrates it, and so does a stone tied
to a string, both of which objects are shown in the illustration.
* * * * *
IN various departments of Art, Oscillation is absolutely invaluable. We
will take, for instance, the best known of these examples, namely, the
Pendulum, by which the movements of clocks are regulated. Without some
mode of regulation, the works would run down rapidly, and the clock
rendered incapable of measuring time. But, in the Pendulum, we possess a
means of making a clock go at any desirable rate, and be faster and
slower at pleasure; a long Pendulum working slowly, and a short one
rapidly.
[Illustration: SPIDER.]
[Illustration: OSCILLATING WEIGHT.]
[Illustration: METRONOME.]
[Illustration: PENDULUM.]
How the Pendulum affects the working of a clock may be seen by reference
to the right-hand figure of the illustration. The movements of the clock
are connected with the Pendulum by means of an ingenious piece of
mechanism called an “escapement,” because it only allows the wheel shown
in the illustration to move one cog at each swing of the Pendulum.
Now, as in the latitude of London a pendulum which is a trifle more than
thirty-nine inches in length swings once in a second, it is evident
that, by lengthening or shortening the Pendulum, we have the rate of the
clock entirely under command.
For example, if a Pendulum be required to swing once in two seconds, it
must be four times as long as that which swings once in one second,
while to swing once in three seconds it must be nine times as long, the
length being measured by the square of the time of vibration.
We are thus able to “regulate” clocks by lengthening the Pendulum if
they be too fast, and shortening them if they be too slow. The reader
will probably have remarked that the conditions of the atmosphere--such
as heat, cold, moisture, or dryness--must have an effect on the length
of the Pendulum, and thus alter the rating of the clock. So they do, and
in consequence the Compensating Pendulums have been invented, some of
them being made of metallic rods of different powers of expansion,
mostly brass and steel, while others carry a quantity of mercury in a
glass tube near the bottom of the Pendulum.
* * * * *
ANOTHER familiar example of the Pendulum is the Metronome, which is
simply a Pendulum with a weight at the top as well as counterpoise below
the bottom, the weight moving up or down so as to decrease or hasten the
pace. Generally a bell is added to it, which is struck at the beginning
of each bar.
The exactness of its beats is perfect, as is known to all musicians, and
is calculated to take the conceit out of players who are apt to
disregard their time. I knew one lady, a really good pianiste, before
whom I placed my Metronome. Before she had played many bars she broke
down, exclaiming that the horrid bell always said “ting” in the wrong
place. However, she soon acknowledged the value of the instrument, and
was glad to use it.
A very good Metronome may be made by fastening a bullet to the end of a
piece of tape, and swinging it backwards and forwards, regulating the
tape according to the time required. Such a Metronome is very portable,
and extremely useful where the conveyance of the clockwork instrument
would be troublesome. Moreover, its beats can be seen by a great number
of persons. I have often used it myself.
Such a Metronome is used in the army, in order to regulate the pace of
the soldier’s step, it being of the last importance that the pace should
always be the same. Otherwise it would be impossible to calculate the
time which ought to be consumed in marching a certain distance, and the
military calculations on which depends the success or failure of a
campaign would be wholly upset, half an hour too soon or too late
meaning failure.
THE ESCAPEMENT.
As we are on the subject of the pendulum and Escapement, we will say a
few words about the latter piece of mechanism. It is here given on a
larger scale than in the previous illustration, so that its action may
be more easily understood. Whether in watch or clock, the Escapement is
exactly the same in principle.
[Illustration: LARVA OF BURYING-BEETLE.]
[Illustration: ESCAPEMENT OF WATCH.]
First there is the escapement wheel, the circumference of which is
furnished with a number of very deep cogs, varying as to the work which
they have to do. Then there comes the escapement itself, which swings on
its pivot, and is regulated in its oscillations by the pendulum. As it
swings backwards and forwards, it is evident that only one tooth of the
wheel can “escape,” and only that in one direction.
We can reverse a steam-engine, but the man has yet to be found who can
reverse a clock, _i.e._ enable it to continue going in the opposite
direction. The only mode would be to enable one set of cogs to flatten
themselves, so as to pass the escapement, and a second set to start up
in exactly the opposite direction. Or perhaps there might be two
parallel escapement wheels, capable of being connected or disconnected
with the clock at pleasure. As, however, a reverse movement is quite
needless, no such invention seems to have been made.
* * * * *
ON the left hand is seen an example of the same principle as shown in
Nature. It represents a larva or grub of the Burying-beetle. It has no
legs available for locomotion, and yet it can get along with tolerable
speed.
Many years ago, when living in Wiltshire, I was much struck with this
fact. There had been an epidemic among sheep, which killed them off so
fast that the farmers would at last not even bury them, but took off the
skins, and left the bodies to moulder as they best might.
It was very unpleasant for the farmers, but just the contrary for the
Burying-beetles, which simply swarmed in the deserted carcasses. If one
of them were tapped with a stick, hundreds of these larvæ came scuttling
out, displaying an activity which was really remarkable in creatures
practically legless.
In reality this movement is achieved by an apparatus very similar in its
action to that of the escapement. The rings, or “segments,” of which the
body is composed, are furnished with rows of sharp points, arranged very
like the cogs of the escapement wheel. By alternately elongating and
contracting the body, these points catch against surrounding substances,
and force the creature onwards, only allowing of movement in one
direction.
Perhaps the reader will remember that in an earlier part of this work it
has been mentioned that the various worms propel themselves by the same
means. So do the Serpents, the edges of the scales serving the same
purpose as the hairs of the worms and the hooks of the grub.
UNION IS STRENGTH.
ON the left hand of the accompanying illustration we have an example of
the wonderful power obtained by uniting together a number of
comparatively weak objects. It represents a portion of the rope attached
to the harpoon with which the natives of some parts of Africa attack and
kill the hippopotamus.
Considering that a full-grown hippopotamus weighs several tons, and, in
spite of its enormous size, is as active as a tiger, we can infer the
strength of the rope which must be needed to hold such an animal when
excited with rage and pain.
A few years ago the female hippopotamus at the Zoological Gardens, when
deprived of her cub, actually tried to leap over the lofty iron barrier,
and so far succeeded as to throw her weight on the uppermost bar.
Fortunately it was made of well-wrought iron, and was only bent by her
weight. Had it been made of cast-iron, like most railings, she would
have snapped it like glass.
Now, the fibres of which the rope is composed are individually feeble,
but, when they lend their strength to each other, their strength is
amazing. It is well shown by a lasso in my possession, made of the
fibres of the aloe-leaf. It is scarcely as thick as a man’s little
finger, and yet it is strong enough to resist the efforts of the most
powerful wild bull. I have some of the separate fibres, and it is
interesting to notice how fibres so slight when separate should be so
strong when united. Part of the rope has been unlaid, so as to show the
manner in which it has been put together.
[Illustration: HIPPOPOTAMUS ROPE.]
[Illustration: SPINNERET OF SPIDER.]
Towards the harpoon itself, a number of small cords laid loosely side by
side are used, so as to prevent the hippopotamus from severing the rope
with his chisel-like teeth, which he would assuredly do if it were
single. The multitudinous cords become entangled among the teeth, and
baffle his efforts; but still their unity is their strength; and, though
the animal may sever one or two of them, the others retain their hold
until he dies under a shower of spears.
* * * * *
ON the right-hand side of the illustration is the Spinneret of the
ordinary garden Spider, showing the many orifices from which the silken
threads emerge. It is a remarkable point, and one which, I believe, is
seldom noticed, that the Spider can at pleasure combine all these fibres
into a single cord, or issue and keep them separate, just as is the case
with the hippopotamus rope.
The latter operation may be seen whenever a large fly gets into the web.
The Spider darts at it, bites it, and then, ejecting a loose mass of
fibres, rolls it up in a moment, as in a shroud, carries it off and
hangs it in a convenient place, and mends the broken meshes of the web.
But both kinds of the cords of the net are made differently from the
winding-up fibres, the former being fixed together, and the latter kept
separate.
PRINCIPLE OF THE DOME.
We are all familiar with Domes, especially when the Dome of St. Paul’s
is the most conspicuous object in our metropolis. Few persons, however,
except professional architects and builders, seem to ask themselves the
principle on which the Dome is constructed.
The strength of the arch is well known, and the Dome is practically a
number of arches, affording material support to each other, and so
enormously increasing the strength of the edifice.
A good idea of the Dome principle may be formed by taking two croquet
hoops, placing them at right angles to each other, tying them together
at the intersection, and pushing the ends in the ground. Even by this
very simple arrangement considerable strength can be obtained; but, if
the hoops be sufficiently multiplied to form a close Dome, it will be
evident that the strength will be correspondingly increased.
So strong, indeed, is the Dome, that it could be made without mortar or
cement, although, of course, its strength is increased by their use. A
very good example of a Dome thus constructed is found in the “igloo,” or
snow-hut of the Esquimaux, which has already been described.
As to the example which I have selected, it would have been easy enough
to have chosen one of the great Domes of the world, such as St. Peter’s
at Rome, St. Maria del Fiore at Florence, St. Paul’s of London, or St.
Geneviève or the Invalides of Paris.
I have, however, selected the present example on account of the thinness
of its walls, the fragility of its material, and the enormous pressure
which it has to undergo. This is the “Receiver” of the Air-pump. It is
made of glass not thicker than an ordinary tumbler, and yet, even when
exhausted of air, it will resist the pressure of the atmosphere for
days together.
When it is remembered that the Receiver is deprived of its internal air,
and therefore has to resist a pressure equal to fifteen pounds on every
square inch of its surface, it may be imagined how strong the Dome is.
Were the top or either side to be flat, it would be crushed as soon as a
vacuum was formed sufficient to deprive it of the support of the air
within.
* * * * *
A GLANCE at the illustration will show how the Receiver is modelled on
the same plan as the Human Skull, the outlines being curiously similar.
It is this formation which imparts such strength to so thin a set of
bones as those which compose the human skull as enables them to protect
a sensitive organ like the brain, on which both reason and life itself
depend.
[Illustration: HUMAN SKULL.]
[Illustration: RECEIVER OF AIR-PUMP.]
Eggs also form good examples of the wonderful strength obtained by this
principle, their thin shells protecting the yolk and the white, as well
as the chick through its progress to maturity.
* * * * *
THE last subject in this chapter is a curious example of an evidently
accidental resemblance in form.
The figure on the right of the accompanying illustration will at once be
recognised as one of those Salad-dressing Bottles which try to conceal
by their shape the small volume of their contents.
That on the left represents one of the many forms through which the
Medusa passes before it attains its perfect form. It was long thought
to be a separate creature, and was known under the scientific name of
Strobila. Modern researches have, however, made the discovery that it is
one of the transitional stages between the creature known as the
Trumpet-hydra (_Hydra tuba_) and the Medusa, popularly known as
Jelly-fish.
The former almost exactly resembles the Hydra of our fresh waters. It is
a tiny transparent gelatinous bag--so transparent as to be scarcely
perceptible, and with some thirty or forty long and delicate tentacles
hanging from its open end. These tentacles are used in catching the
minute creatures on which it feeds. It is fixed, and, to use Mr. Rymer
Jones’s simile, looks like a beautiful silk-like pencil waving amidst
the water. Its length is not quite half an inch.
[Illustration: TRUMPET-HYDRA.]
[Illustration: SALAD-DRESSING BOTTLE.]
That it should be identical with the remarkable form shown in the
illustration seems impossible, but such is the case. Its body becomes
contracted as if tied with strings, and every segment thus formed
develops a set of tentacles, breaks away, and swims off in the form of a
Medusa. The upper segment is exhibited as undergoing this process.
The figure is magnified so as to show the structure better, its right
length being about one-third of an inch. A full and graphic history of
this creature and its manifold changes may be found in Mr. Rymer Jones’s
“Aquarian Naturalist.”
It is not likely that the inventor of the Salad-dressing Bottle ever saw
a Hydra, but the resemblance is strangely exact.
ACOUSTICS.
CHAPTER I.
PERCUSSION.--THE STRING AND REED.--THE
TRUMPET.--EAR-TRUMPET.--STETHOSCOPE.
The Science of Sound.--Rhythmical Vibrations.--The Drum.--Primitive
Drums.--The Solid and Hollow Log.--The Bass Drum and
Kettle-drum.--African Drums.--Gnostic Gems and the Ashanti
Drum.--Tympanum, or Drum of the Human Ear, and its Mechanism.--An
artificial Tympanum.--The String.--The Bow and the Harp.--The
Harpsichord and the Zither.--The Bow and the Violin.--The
Cricket.--The Vibrator, or Reed.--The Jew’s Harp and
Harmonium.--The Cicada and its Song.--Harmonics upon Strings.--The
Æolian Harp.--Harmonics upon the Trumpet.--The Trombone.--Trachea
of the Swan.--The Ear-trumpet.--The Sea-shell.--The
Stethoscope.--Savage Food.--The Aye-aye.--The Siren and its
Uses.--Echo and Whispering Gallery.
In a work of this nature it would be absolutely impossible, not to say
out of place, to give an account of so elaborate a subject as Acoustics,
_i.e._ the science of Sound. Suffice it to say, that all sounds are
produced by the vibration of air, and that the fewer vibrations, the
lower is the sound, and _vice versâ_.
When such vibrations are produced regularly, they form Musical sounds,
but, if irregularly, the sounds can be only distinguished under the term
of Noise. The earliest germ of music lies in certain savage races, who,
as long as they can maintain a rhythmical beat on any resonant
substance, do not particularly care what it is. A hollow tree is a
splendid instrument in their opinion, but, if this cannot be had, a dry
log of wood will answer the same purpose.
Some tribes, more ingenious than others, cut a deep groove upon the
upper surface of a log, hollow it through this groove, and then hammer
away at it to their hearts’ content. The next move was to cut off a
section of the trunk of a tree, hollow it, set it on end, and then beat
it on the sides.
Lastly, some one hit upon the idea that if the open upper part of the
hollowed log were covered with a tightly stretched membrane, and that if
the membrane, instead of the log, were beaten, the resonance would be
increased. In consequence, the real Drum was invented, and seems to have
existed from time immemorial in parts of the world so distant that they
could not have had any communication with each other.
Take, for example, the well-known “Bass Drum” of our bands, which is
shown on the right hand of the figure. We make it a very ornamental
article, with frame of metal, and heraldic decorations of all kinds.
[Illustration:
BONES AND DRUM OF EAR.
_a_ TUBE OF EAR.
_b_ DRUM.
_c_ HAMMER.
_d_ ANVIL.
_e_ STIRRUP.]
[Illustration: DRUMS.]
Lying against it is one of a pair of Kettle-drums, such as are always
seen in mounted bands. They look very easy to play, but, if the reader
will try a pair, he will soon find his mistake.
But there are savage tribes of Western Africa who make Drums of such
wonderful power that their sullen roar is heard for miles around, as
their slow, triple beat summons the tribe to arms like the fiery cross
of the Highland clans. As to shape, lightness, and beauty, our Drums are
infinitely superior to theirs, but, so far as I can gather from personal
and written narratives of African travellers, none of our Drums surpass
theirs in richness, depth of tone, and power of carrying sound.
Sometimes these Drums, instead of being mere cylinders, are carved into
the most strange and fantastical patterns. I possess one of these
curious Drums, brought from Ashanti, and carved out of a solid piece of
wood.
The strange point in it is, that it represents a double head carrying,
after all negro fashions, a sort of vessel upon it. One part of the head
represents a human head (not that of a negro), while the other merges
gradually into an eagle’s head and beak. It is, in fact, a Gnostic gem,
and would pass muster as such if it had been engraved on chalcedony,
cornelian, or other semi-precious stones which are employed in the
seal-engraver’s art.
Upon this composite head is placed the Drum itself, which is also cut
out of the solid block, and which, after the fashion of West African
Drums, has a hole on one side.
This remarkable instrument was given to me by an old merchant captain,
who brought it himself from West Africa, and who, when I made his
acquaintance, had actually painted it all kinds of colours, planted it
in his garden, and was using the Drum as a flower-pot. Of course, as
soon as it came into my possession, I put it in “pickle,”--i.e. a strong
solution of alkali,--brushed off the paint, and placed it in my museum,
where it is now.
* * * * *
ON the left hand of the illustration on page 514 is given a sort of map
or chart of the human Ear, with its internal Drum, or Tympanum, as it is
scientifically termed.
It is by the vibration of this Drum that hearing is made possible, the
vibrations of the air being transmitted to the Drum by means of a
beautiful bony apparatus, termed the Hammer, Anvil and Stirrup.
Sometimes the action of the Drum is partially checked, and then the
sufferer is said to be “hard of hearing.” Sometimes it is broken, or its
action totally clogged, and then he is said to be “stone deaf.” There
have been cases where an artificial tympanum has been inserted, and
answered its purpose fairly well.
THE STRING AND REED.
It has previously been mentioned that all sounds are owing to vibrations
of the air. But there are many ways of producing these vibrations, and
each mode gives a different quality of tone. We have already seen, by
means of the drum, how sound is produced by percussion. We shall now see
how sounds can be produced by the vibrations of a String.
If the string of a bow be pulled and smartly loosed, the result is a
distinctly musical sound, higher or lower according to the length and
tension of the string. Perhaps some of my readers may recall the passage
in Homer’s “Odyssey,” where Ulysses strings the fatal bow:--
“Heedless he heard them; but disdained reply,
The bow perusing with exactest eye.
Then, as some heavenly minstrel, taught to sing
High notes responsive to the trembling string,
To some new strain when he adapts the lyre,
Or the dumb lute refits with vocal wire,
Relaxes, strains, and draws them to and fro;
So the great master drew the mighty bow,
And drew with ease. One hand aloft displayed
The bending horns, and one the string essayed.
From his essaying hand the string let fly,
Twanged short and sharp, like the shrill swallow’s cry.”
The Harp is, in fact, nothing but a magnified bow, with a number of
strings of graduated length and tension. Some very beautiful experiments
have been made on this subject by the Rev. Sir F. A. G. Ouseley,
Professor of Music at Oxford, who stretched a string of sixty-four feet
in length, and found that although, when vibrating, it must produce a
note, there was no human ear that could distinguish it. Yet, if combined
with other musical instruments, it would probably do its work well. The
theory of the vibrations will be briefly described on another page.
These vibrations may be produced in various manners. The string may be
pulled with the fingers, as in the harp, the guitar, the zither, or even
the violin, &c., in pizzicato passages.
The old harpsichord, now an instrument vanished into the shadows of the
past, pulled the strings with little strips of quill, acting like the
thumb-ring of the zither-player. The “plectrum” of the ancients acted in
the same manner, and the Japanese have at the present day a sort of
guitar played with a plectrum. I have heard it, but cannot particularly
admire the effect, the notes appearing to be without feeling, and as if
they were played on a barrel-organ.
Sometimes, as in our modern pianos, the strings are struck by hammers
instead of being pulled by fingers, plectrum, or goose-quill.
The most ingenious mode of causing musical vibration is the Bow, which
is too familiar to need a detailed description. Suffice it to say that
it really is a modified bow, the place of the string being supplied by a
flat band of horsehair, which is drawn over the string, and so causes it
to vibrate. In order to enable the bow to grip the string, it is rubbed
with resin almost as often as a billiard-player chalks his cue.
Some skill is required even in producing a sound by the bow. It looks as
if any one could do it, but a novice, if he extorts any sound at all,
never rises above a squeak. When I took my first violin lessons, nearly
thirty years ago, I was so horrified at the discordant sounds elicited
from the instrument, that I retired to the topmost garret of the house
in order not to hurt any one’s feelings except my own.
[Illustration: CRICKET.]
[Illustration: CICADA.]
[Illustration: VIOLIN.]
[Illustration: JEW’S HARP.]
* * * * *
ON the left hand of the illustration is seen a well-known example of the
imitation of Nature by Art. This is the common Cricket, whose loud
shrill call is more familiar than agreeable.
Some years ago, while engaged on my “Insects at Home,” I gave much time
to the examination of the structures by which such a sound can be
produced. On the under side of the wing-covers, or “elytra,” as they are
scientifically termed, are notched ridges, which, when examined with a
moderate power of the microscope, have something of this appearance
~~~~~~~. The friction of these notches produces the musical sound,
which, as the reader will see, is exactly analogous to the friction of
the bow upon the string.
* * * * *
NEXT we come to the Vibrator, sometimes called the Reed. It is
introduced into various musical instruments, such, for example, as the
harmonium, the clarionet, the oboe, the bassoon, and various organ
pipes.
The simplest form of the Vibrator is shown in the Jew’s Harp, as it is
popularly called, though it is not a harp, and has nothing to do with
Jews.
[Illustration: VIBRATING STRINGS.]
[Illustration: ÆOLIAN HARP.]
The word is really a mistaken pronunciation of “jaw’s harp,” because the
instrument is held against the teeth, while its tongue is vibrated by
strokes of the finger. These vibrations affect the air within the mouth,
and, by expanding or contracting the mouth, the sound is lowered or
raised according to the laws of Acoustics. Of course, the range of notes
is very small, being limited to those of the common chord, and even they
being attainable only by a practised performer. Very good effects,
however, have been produced by means of a series of Jew’s Harps, set to
different tones by loading the end of the tongue with sealing-wax or
similar substances.
* * * * *
AN apparatus constructed on the same principle is to be found in the
vocal organs of the male Cicada. If one of these insects be examined on
the lower surface, two curious and nearly circular flaps will be seen,
just at the junction of the thorax with the abdomen. It is by the action
of these two little vibrators that the insect is able to produce a sound
so loud, that in calm weather it may be heard at the distance of a mile.
* * * * *
THE accompanying illustration is, in fact, a sort of chart as to the
vibration of sound.
On the right is shown the ÆOLIAN HARP, with its upper lid raised, so as
to show the structure of the strings. These are all tuned to the same
note, the present D being generally accepted as being most free from
false tuning, and less liable for the errors of “temperament.” Several
of the strings are an octave lower than the others, but the tonic is
always the same.
The instrument is placed in a current of air, generally in a window,
with the sash let down upon it, and the air-currents set the strings
vibrating in a most wonderful manner.
There is no need for human fingers to touch them, but they automatically
divide themselves into the component parts of the common chord, and
produce octaves, fifths, and thirds _ad infinitum_.
On the left hand of the same illustration is exhibited a string of the
same length and tension, vibrating in two different ways. The upper
figure shows it divided into three portions, each of which gives the
fifth above the tonic, and all of which, when sounding simultaneously,
give a fulness and richness to the tone which could only be attained
otherwise by three distinct instruments. All players of stringed
instruments know how invaluable are these harmonics, without which many
passages of well-known music could not be played, and which are produced
by “damping,” and not pressing the strings.
So, if the string be lightly touched, or damped at the crossing portion
at either end, the result will be that the string divides itself into
three portions, and all three resound simultaneously.
The lower string is vibrating in thirds, having divided itself into four
portions. If it were damped in the middle, it would divide itself into
two portions, and sound octaves.
The subject is a most interesting one, but our space is nearly
exhausted, and we must pass to another branch of it.
* * * * *
IN all brass instruments furnished with a mouthpiece, and not with a
reed, the notes are obtained by vibrations of the enclosed air, caused
by the movement of the lips. They are all set to some definite tonic,
sometimes C natural, but mostly to a flat tone, such as B flat or E
flat.
Taking the ordinary military trumpet or bugle as an example, we have
(when we have learned how to play it), first, the tonic. By alteration
of the lips we get the octave above the tonic. Then comes the fifth;
then the third, which is, in fact, another octave; and then a few other
notes, the truth of which depends on the ear of the player.
Now, all these notes are obtained by means of the lips, which set the
column of air vibrating, and divide it into harmonics. The apparently
complicated bugle-calls of the army are nearly all formed from four
notes only, _i.e._ (taking C as the tonic) C G C E G.
* * * * *
[Illustration: TRACHEA OF SWAN.]
[Illustration: TROMBONE.]
The Trombone, which is shown on the right hand of the illustration, has
the advantage of being lengthened at will, and thus giving the performer
a fresh tonic, and consequently another series of harmonics. Valved and
keyed instruments have a similar advantage, the one acting by
lengthening, and the other by shortening, the column of air. The former
is infinitely the better plan, as it sets more harmonics vibrating, and
consequently gives a greater richness of tone.
A familiar example of this is to be found in the Ophicleide and
Euphonium. The former is eight feet in total length, and alters its
tonic by eleven keys, which shorten the column of air. The latter is of
the same length, but, by the employment of valves, can be made sixteen
feet in length. Consequently the euphonium has practically killed the
ophicleide, just as the ophicleide killed the serpent. The
cornet-à-pistons, the brass contra-basso, the flugel horn, the tenor
sax-horn, &c., are all constructed on the same principle.
* * * * *
ON the left hand of the illustration is shown the wonderful apparatus by
means of which the Swan produces its far-resounding cry. The windpipe,
or “trachea,” as it is technically named, passes down the neck,
protected by the bones, until it reaches the chest. There it leaves
them, enters the cavity of the chest, and contorts itself in such a
manner as to obtain greater length, just as is the case with the
trombone and valved instruments.
ACOUSTICS AS AIDS TO SURGERY.
We have already seen how the air-vibrations poured in at the small end
of the trumpet can make resonant notes. We have now to see how the
reverse process can be employed, and sounds poured into the larger end
be conveyed to the ear.
[Illustration: EAR-TRUMPET.]
[Illustration: CONCHA OF HUMAN EAR.]
The Ear-trumpet is a familiar example of such an instrument, and, as it
is shown in the illustration, there is no need of further description.
It is rather remarkable, by the way, that the length of tube does not
seem to interfere with the conveyance of sound, as may be seen by the
speaking-tubes which are now so common in private houses, hotels, and
offices.
I know of one church in which there is a special seat for deaf persons.
The reading-desk and pulpit are both fitted with the large ends of
Ear-trumpets. From them pass tubes under the flooring, and so into the
seat, where they can be applied to the ear of the deaf worshippers.
* * * * *
ON the right hand is the “Concha,” as it is called, of the human ear,
which is evidently constructed for the purpose of collecting and
concentrating sounds. Instinctively, if we wish to near any sound more
distinctly, we place the open hand behind the ear, so as to enlarge its
receptive capacity, and send a greater volume of sound into the ear.
The well-known experiment of holding a shell to the ear so as to hear
the murmur of the sea is due to the same cause, the shell collecting,
though in a mixed manner, all the surrounding sounds, and making a
murmur which really resembles the distant wash of the waves upon the
shore.
[Illustration: SAVAGE TAPPING TREE.]
[Illustration: SURGEON USING STETHOSCOPE.]
Then, if we examine the various animals which need acute hearing, either
to seize prey or escape from enemies, we shall find that they have large
and mobile ears, which can be directed so as to catch the expected
sound. The hare, rabbit, and deer are examples of the latter, while the
former are well represented by the domestic cat, whose ears are always
pricked forward when she hears the scratchings of a mouse.
* * * * *
ANOTHER most useful appliance is the STETHOSCOPE, which enables the
skilful surgeon to investigate the interior of the body almost as
clearly as if it were transparent. It is perfectly simple, being nothing
but a trumpet-shaped piece of wood, formed as shown in the illustration.
Sometimes it is hollow, and sometimes solid, but the result is the
same, sound being transmitted through wood in a most remarkable manner.
For example, if one end of the longest scaffolding pole be slightly
scratched with a pin, the sound will be distinctly heard by any one who
places his ear against the other end, though the person who uses the pin
can scarcely hear the sound himself. The surgeon, therefore, places the
broad end of the Stethoscope upon the patient, and the other upon his
ear, taps more or less lightly with his fingers, and by the sounds
transmitted through the Stethoscope ascertains the condition of the
internal organs.
* * * * *
ON the left hand is an illustration of the mode in which the Australian
savage, without the least idea of the theory of Acoustics, utilises the
sound-conducting power of wood. If he wishes to know whether or not a
hollow tree is tenanted by an animal of which he is in pursuit, he
places his ear against the tree, taps it smartly with his tomahawk, and
listens for the movement of the animal inside.
So delicate is this test, that it is employed even when the native is
hunting for the large beetle-grubs on which they feed, and which are
accounted a luxury even by Europeans, when they have once overcome the
prejudice attaching itself to eating, without cookery, fat white grubs
as thick and long as a man’s finger.
The Aye-aye is said to eat in exactly the same manner, tapping with its
long finger the trunks and branches of trees and, if it hears a maggot
inside, gnawing it out.
MEASUREMENT OF SOUND.
Of late years we have had an instrument which enables us to measure the
vibrations of sound as accurately as the barometer measures the weight
of the atmosphere, the thermometer the temperature, and the photometer
the power of light. This is the Siren, which is shown on the right hand
of the accompanying illustration.
To explain this instrument fully would require ten times the space which
we have at command, and necessitate a great number of drawings. I will,
therefore, endeavour to explain its principle in as brief terms as
possible.
The reader will observe that at the lower part of the instrument there
is a disc pierced with a number of holes, and that above these are two
dials. Below the perforated disc, and therefore unseen, is a circular
plate, also pierced with holes. When a pipe is attached to the lower
part of the instrument, and air propelled through it, the disc begins to
revolve, every revolution being recorded by the dials, after the fashion
of the ordinary gas-meter.
[Illustration: GNAT.]
[Illustration: HUMBLE-BEE.]
[Illustration: SIREN.]
As the pressure is increased, the air, passing through the holes,
assumes a rhythmical beat, which soon becomes metamorphosed into musical
notes. It is evident, therefore, that, by means of this instrument, the
number of vibrations which produce a definite tone can be measured with
absolute accuracy by any one who has an ear capable of appreciating a
musical note.
It is by means of the Siren that the much-disputed tonic of C will be
settled, the Continental and the English C being greatly at variance,
and even the English C having been advanced almost a tone since the time
of Handel. Much is it to be wished that Italy, the home of song, and
England, the patron of song, could unite in their tonic, instead of
having systems so widely different that an Italian singer is at a loss
with the English pitch, as is an English singer with the Italian pitch.
The Siren is even brought into the service of entomologists, enabling
them to measure by the sound the rapidity with which a flying insect
moves its wings. By means of this instrument we know the origin of the
sharp, piercing “ping” of the Gnat, and the heavy, dull boom of the
Humble-bee, both of which insects are given in the illustration.
Before taking leave of this subject, I may mention that the instrument
is called the Siren because it sings as well under water as in the air,
provided that water instead of air be driven through it.
ECHO.
Our last page will be given to the phenomenon called by the name of
ECHO, which consists in the power of solid substances, whether natural
or artificial, of reflecting the waves of sound thrown against them,
just as a mirror reflects the waves of light.
[Illustration: WHISPERING GALLERY.]
Very often the Echo is naturally formed, as shown in the illustration,
by rocks which cast back the sound--waves thrown against them. This is
the case in several parts of Dovedale in Derbyshire, where a pistol shot
is reverberated backwards and forwards in a most wonderful manner, and a
trumpet blast repeats itself over and over again.
At Walton Hall, the residence of the late C. Waterton, Esq., there is a
wonderful Echo, nearly half a mile from the house. Mr. Waterton had
discovered the Echo, which proceeded from the walls of the house, and,
having found its focus, placed on it a large stone, called the
Echo-stone. Any one sitting on this stone, and singing, speaking, or
whistling towards the house, heard every sound repeated, as if in
mockery.
The celebrated Whispering Gallery in St. Paul’s Cathedral is nothing but
an ordinary Echo, though so intensified by the process of radiation,
that the sound is transmitted from one side of the dome to the other,
just as light or heat is reflected from concave mirrors.
INDEX.
A.
Aard-vark, 182, 227
Abattis, 109
Acaleph, 15
Acorn Barnacles, 90
Acoustics, 513
Acrida viridissima, 231
Actinurus, 461
Adze, 234
Æolian Harp, 518
Aërostatics, 436
Air-gun, 77
Aloe, 252
Amentum, 502
Amphidotus cordatus, 224
Anchor, 39
Angler-fish, 91, 416
Antherozoids, 368
Ant-bear, 100
Ant-lion, 52
Anthidium manicatum, 237
Ants, 391, 409
Ants’ Nest, 214
Aphides, 391
Aphrodite aculeata, 353
Apple-parer, 456
Aquarium, 393
Archer-fish, 78
Architecture, 159
Argus Star-fish, 89
Armadillo, 189
Armour, 120
Art, 472
Artesian Well, 433
Arundinaria Schomburgkii, 28
Ascalaphus, 111
Ascidian, 497
Aspidomorpha excelsum, 198
Auger, 254
B.
Baited Traps, 97
Ball-and-socket Joint, 313
Balloon, 436
Bamboo, 28
Band Saw, 244
Barea, 147
Barometer, 444
Basket-urchin, 89
Bats, 399
Battering-ram, 153
Beak of Duck, 354
Beaver, 233
Beds, 400
Bee, 220
Beroë, 15
Bessemer Process, 299
Bicycle, 503
Binocular Microscope, 287
Birdlime, 98
Blow-gun, 75
Boat, 5
Boat-hook, 44
Boatman, 12
Boiling Water, 445
Bombardier-beetle, 156
Bombyx mori, 179
Bosjesman, 308
Bot-fly, 396
Bower, 410
Bower-birds, 410
Bowsing of Rope, 318
Brachinus crepitans, 156
Bradawl, 249
Brocken Spectre, 295
Brown-tailed Moth, 180
Brushes, 340
Buffer of Train, 369
Bullet-making Machine, 157
Bunday, 69
Burdock, 117
Burial, 419
Burying-ants, 420
Burying-beetle, 507
Buttons, 346
Buttresses, 196
C.
Cache, 397
Callipers, 274
Caltrops, 110
Camel, 424
Camera obscura, 277
Candle, 351
Carriage Spring, 363
Cassava Press, 447
Catapult, 361
Catchpoll, 104
Cathedral, 166
Centrifugal Force, 500
Cephalotus, 98
Chaff-cutter, 320
Chameleon-fly, 11
Chinese Paper Lantern, 378
Chinese Repeating Cross-bow, 365
Chinese Stink-pot, 155
Chirodota, 470
Chisel, 232
Chœtodon, 78
Chromatrope, 305
Cicada, 243, 518
Circular Saw, 247
Cistern, 422
Clam Shell, 260
Clasp, 347
Climbing-spur, 134
Cloth-dressing Machine, 339
Club, 52
Cnidæ, 371
Coffee-making Machine, 329
Coluber natrix, 106
Combs, 343
Compass, 491
Concealment, 144
Condenser, 428
Contouring-glass, 272
Coracle, 22
Cordon Saw, 244
Cork, 350
Corrugation, 480
Cossus ligniperda, 237
Crab, 261
Crab-pot, 103
Creeper, 203
Cricket, 388, 517
Crow-oyster, 348
Crushing Instruments, 320
Cuckoo-spit, 146
Culex pipiens, 9
Cupping, 330
Cuttle-bone of Sepia, 166
Cydippe, 15
D.
Daddy Long-legs, 337
Dagger, 58
Dam, 210
Dandelion Seed, 439
Decticus griseus, 231
Deer-trap, 104
Dew, 426
Diamond Drill, 459
Digging-stick, 223
Dionea muscipula, 97
Dipsacus fullonum, 339
Disguise, 147
Divers, 382
Diving-bell, 383
Diving Dress, 384
Dog-fish Skin, 265
Dome, 510
Doors and Hinges, 172
Drag, 43
Dragon-fly, 455
Dragon-fly Trachea, 376
Drainage, 492
Driver-ant, 201
Drosera, 100
Drum, 514
Dutch Rush, 264
E.
Ear, 515
Ear-trumpet, 521
Earth-worm, 44
Earwig, 261
Eaves, 184
Echeneis remora, 333
Echinococcus, 40
Echinus, 315
Echo, 525
Echo-stone, 526
Eel-pot, 103
Egg-hatching Machine, 395
Eider-duck, 401
Elastic Springs, 360
Elateridæ, 387
Electric Eel, 486
Electric Light, 488
Electric Ray, 485
Electric Tourniquet, 463
Electricity, 482
Elk, 131
Elk-yard, 131
Emperor-moth, 104
Epeira diadema, 87, 345
Equisetum, 264
Ermine-moth, 180
Escapement, 507
Ether Spray, 428
Eumenes, 311
Eye, 277
Eye of Spider, 288
F.
Fairy Martin, 169
Fall-trap, 140
Fan, 416
Feather Mail, 125
Fencers, 317
File, 263
Filter, 352, 425
Fire, 412
Fire-fly, 489
Fire-guard, 419
Fish-hook Spiculæ, 117
Fish-scales, 189
Fish-tank, 393
Fishing-frog, 91, 416
Flying Dragon, 440
Flying Frog, 441
Flying Squirrel, 440
Foot of Aard-vark, 227
Foot of Mole, 226
Foot of Mole-cricket, 226
Fork-grinders, 356
Fort, 129
Fountains, 430
Frog, 484
Furnarius fuliginosus, 310
Fur of Beaver, 186
G.
Gad-fly, 254, 406
Galleria alvearia, 151
Galleria-moth, 151
Garden Spider, 87, 345
Gecko, 334
Geometra Caterpillar, 149
Geranium, 478
Gerris, 467
Gills of Fish, 414
Gimlet, 252
Gin, 95
Girder, 193
Glow-worm, 342, 439
Gnat, 9
Goat-moth, 237
Goby, 334
Gold-tailed Moth, 180
Goose-grass, 116
Gossamer Spider, 437
Grallina Australia, 310
Grasping Tools, 258
Grass-blade, 250
Grass-snake, 106
Grass-wrack, 473
Grasshopper, 337, 388
Great Green Grasshopper, 231
Grindstone, 325
Gyrinus natator, 22
Gyroscope, 503
H.
Hammer and Anvil, 515
Hammock, 402
Hand, 450
Harpoon, 71
Heart or Hairy Urchin, 224
Hedgehog, 110
Hemerobius, 397
Hen-coop, 393
Hippopotamus, 508
Hippopotamus Tooth, 234
Hirundo Ariel, 169
Hoof of Elephant, 364
Hoof of Horse, 363
Hookah, 377
Hooks, 115, 398
Hooks and Eyes, 346
Hoop-shaver Bee, 237
House-fly, 343, 456
Human Spine, 369
Hydra, 512
Hydrant, 430
Hymedesmia, 117
Hyponomeuta padella, 180
I.
Ice, 457
Ice-house, 179
Ichneumon-fly, 174, 249, 338
Injecting Syringe, 65
Iris of Eye, 293
Ita Palm-tree, 162
J.
Janthina communis, 48
Japanese Fishing-rod, 460
Japanese Singlethorn, 124
Jaws of Crocodile, 366
Jaws of Pike, 105
Jaws of Shark, 106
Jaws of Whale, 355
K.
Kedge, 41
Kite, 500
Knee-joint, 316
Kris, 239
L.
Lace-wing Fly, 397
Lagopus vulgaris, 150
Lamp, 412
Lampern, 335
Lampetra fluviatilis, 335
Lancet, 83, 239
Lappet-moth, 149
Laurel-bottle, 358
Lazy-tongs, 454
Leaf cutter Bees, 231
Leaf-insect, 149
Leaf-rollers, 362
Leech, 335
Lighthouses, 207
Limnæa stagnalis, 6
Limpet, 245, 332
Loadstone, 490
Lobster, 261, 497
Locust, 231
Long-tailed Titmouse, 401
Lophius, 416
Low-pressure Engine, 429
Lump-sucker, 334
M.
Maelström, 1
Magdeburg Hemispheres, 331
Magic Lantern, 294
Magnetic Respirator, 356
Main Gauche, 73
Mangle, 324
Mangrove-tree, 143
Manuring, 492
Mare’s Tail, 264
Mason Wasp, 170
Mat, 404
Meadow Orchis, 100
Measure, 267
Medusa, 372, 512
Megachile, 231
Metronome, 506
Microgaster alvearius, 174
Microgaster glomeratus, 174
Milk, 390
Mines, 443
Mining, 430
Misericorde, 120
Mole, 496
Mole-cricket, 227
Mont Cenis Tunnel, 267
Mop, 502
Mortar, 217
Moselekatze, 162
Moss, 371
Mountains, 216
Mouse-trap, 97
Movable Gas-lamp, 376
Mud-patten, 466
Mud Walls, 181
Multiplying-glass, 288
Muscles of Leg, 449
Mussel-shell, 35, 259
Myrapetra scutellaris, 181
Myrmeleo, 52
Myrmica Kirbyi, 184
N.
Nature-printing, 475
Nautilus, 2, 464
Needle-gun, 367
Nemertes Borlasii, 93
Nerves, 486
Net, 85
Northern Crown, 297
Norton Tubes, 433
Notonecta glauca, 13
Nshiego Mbouvé, 160
Nut-crackers, 321
Nuthatch, 256
O.
Octopus, 463
Odynerus murarius, 170
Œstrus bovis, 254
Ophion, 174
Optics, 276
Orchis morio, 100
Oscillation, 504
Ostracion, 122
Orang-outan, 161
Oven-bird, 310
Owl’s Eye, 284
P.
Paddle-wood Tree, 198
Paint, 219
Palm-leaf, 418
Paper, 472
Parachute, 438
Parasol, 407
Pea-shooter, 74
Pelecinus, 338
Pelicans, 393
Pelopœus, 312
Pendulum, 505
Pensile Oriole, 402
Perfume Spray, 428
Periwinkle, 245
Phantasmascope, 305
Philetærus socius, 135
Pholas dactylus, 200
Phryganea, 192
Physa fontinalis, 8
Physalis pelagicus, 46
Pichiciago, 123
Piddock, 200
Pied Grallina, 310
Pill Millipede, 123
Pincers, 258
Pinna pectinata, 35
Pinna-shell, 35
Pistolograph, 361
Pitfall, 50
Plane, 235, 250
Pneumatic Peg, 330
Poison, 62
Polar Bear, 137
Polistes, 481
Polynoe, 71
Porches, 183
Porcupine, 110
Porcupine Ant-eater, 110
Porthesia auriflua, 180
Porthesia chrysorrhœa, 180
Portuguese Man-of-war, 46, 372
Pouch-shell, 8
Pressure of Atmosphere, 329
Printing-press, 317
Proboscis of Fly, 379
Processionary Moth, 180
Projectiles, 74
Propolis, 220
Pseudoscope, 287
Ptarmigan, 150
Pucunha, 76
Puff and Dart, 75, 351
Pulley, 452
Pyramids, 216
Q.
Quilt Armour, 126
R.
Radius, 194
Rain-cloud, 429
Ranjows, 109
Rat-tail Maggots, 385
Rattan, 204
Razor, 236
Receiver of Air-pump, 511
Reduvius personatus, 146
Reed, 518
Reverted Spikes, 102
Ribbon Saw, 244
Ring and Staple, 415
Ringed Tissues, 378
Robber-crab, 405
Rocket, 462
Rod and Line, 90
Rolling-mill, 322
Rosemary, 408
S.
Sabella, 218
Saddle-back, 348
Sailing Raft, 5
Salad-dressing Bottle, 511
Sand-paper, 265
Saturnia pavonia minor, 104
Saw, 239
Saw-fly, 241
Sawyer-beetle, 248
Scale Armour, 123
Scales of Butterfly’s Wings, 187
Scaling-fork, 133
Scarabæus, 494
Scissors, 228
Screw, 498
Sea-anemone, 8
Sea-basket, 89
Sea-mouse, 353
Sea-urchin, 315
Seed-drills, 336
Sepia officinalis, 167
Serpula, 44, 135, 219, 352
Sewage, 496
Sewing, 406
Shark-tooth Sword, 56
Shears, 228
Sheep-fly, 396
Shell of Tortoise, 188
Ship-worm, 200
Short-tailed Manis, 124, 188
Sialis armata, 275
Siamese Link, 448
Silkworm, 158
Silkworm Cocoon, 179
Siren, 523
Sirex gigas, 252
Skidor, 466
Skip-jack Beetle, 387
Skull, 210, 511
Slates, 188
Sling, 502
Sloth, 398
Slug, 245
Smoke-jack, 499
Snow-house of Esquimaux, 163
Snow-house of Seal, 163
Snow-shoe, 464
Spade, 223
Spear, 58
Spectroscope, 297
Spider, 509
Spider-crab, 147
Spiked Defences, 107
Spiracles of Fly, 357
Spiral, 498
Spiral Spring, 371
Spiral Tissues, 375
Spirit-level, 271
Spokeshave, 236
Spout-hole, 434
Sprat-sucker, 71
Spring, 430
Spring-bow, 142
Spring-gun, 142
Spring-jack, 386
Spring Solitaire, 371
Spring-tails, 388
Spring-trap, 95
Squirrel, 456
Stag-beetle, 248
Star-fish, 332
Steam-blast, 443
Steelyard, 450
Stereoscope, 286
Stereotype, 479
Stethoscope, 522
Stickleback, 218
Still, 425
Stinging Jelly-fish, 372
Stinging-nettle, 67
Stipple, 477
Stoat, 150
Stone-fly, 192
Stopper, 350
Stove, 413
Stratiomys, 11
Stratiomys chamæleon, 11
String, 515
Subterranean Dwelling, 213
Suckers of Cuttle-fish, 332
Suckers of Water-beetle, 332
Sucking Eggs, 445
Sucking-fish, 333
Sucking Sugar-cane, 445
Sumpitan, 75
Sundew, 100
Surgical Cradle, 405
Suspension-bridge, 202
Swallow-tailed Butterfly, 468
Sword, 56
Sword-grass, 57
Synapta, 40, 470
Synovia, 454
T.
Tachina, 172
Tail of Scorpion, 66
Tailor-bird, 406
Tearing Weapons, 112
Teazle, 339
Teeth, 327
Telegraph, 487
Terebella, 218
Teredo, 200
Termite, 153, 182, 394
Thaumatrope, 302
Thigh-bone, 314
Thornback-crab, 147
Throwing-stick, 79
Ties, 194
Tiger-beetle, 134
Tiger-claw, 112
Tiger-moth, 403
Tiles, 187
Tillage, 492
Tipula, 337
Toggle, 316
Tools, 222
Tools of Measurement, 267
Top, 503
Torpedo, 485
Tortoise, 229
Toucan, 346
Trachea of Animals, 380
Trachea of Insects, 376
Trap-door Spider, 175
Traveller’s Tree, 423
Tree-caddis, 111
Trench, 150
Trichiosoma lucorum, 242
Tripod Wheel-bearer, 461
Triquetra, 219
Troglodytes calvus, 160
Trombone, 520
Trunk-fish, 122
Trypoxylon aurifrons, 312
Tunnel, 168, 199
Turbine Pump, 497
Turkish Bath, 426
Turtle, 229
U.
Ulna, 194
Umbrella, 407
Useful Arts, 308
V.
Vallisneria Plant, 38
Varnish, 219
Velella, 2
Venus Fly-trap, 97
Vertebræ of Snake, 314
Victoria Regia, 196
Violet Snail, 48
Voltaic Pile, 484
W.
Walls, 177
Walrus, 41, 136
Waraus, 162
Wart-biter, 231
Wasp, 474
Wasp-comb, 167
Water-boatman, 13
Water-fall, 431
Water-gnat, 467
Water-lily, 382
Water Main, 497
Water-ram, 434
Water-snail, 6
Water-spider, 383
Water-tank, 423
Water Telescope, 291
Water Turbine, 463
Wax, 220
Wax-moth, 151
Weaver-bird, 169, 185
Webbed Feet, 467
Wet-bulb Thermometer, 428
Wheat Straw, 27
Wheel, 469
Wheel Animalculæ, 306
Whelk, 245
Whirlwig-beetle, 22, 292
Whispering Gallery, 626
Wind, 442
Window, 190
Woodpecker, 256
Woolly Bear, 110
Wurble-fly, 396
Z.
Zarabatana, 76
Zoetrope, 305
Zostera marina, 473
* * * * *
THE END.
PRINTED BY J. S. VIRTUE AND CO. LIMITED, CITY ROAD, LONDON.
* * * * *
Typographical errors corrected by the etext transcriber:
Bombadier-beetle=> Bombardier-beetle {pg 144}
very ong after=> very long after {pg 262}
the Multipying-glass=> the Multiplying-glass {pg 290}
fills the air=> fill the air {pg 356}
cook their flood=> cook their food {pg 412}
If the hand move towards=> If the hand move towards {pg 444}
protecting the yelk=> protecting the yolk {pg 511}