THE PRINCIPLE OF THE SPRING.--THE ELASTIC SPRING.--ACCUMULATORS.--THE
SPIRAL SPRING.
Springs and their various Structure.--The Elastic Spring.--The
Boy’s Catapult and its Powers.--The Pistolograph, its Principle,
and Uses to which it can be put.--Leaf-rolling Caterpillars, and
their Way of Work.--The Carriage Spring.--The Horse’s Hoof and its
complex Structure.--Fungi and their united Power.--The Chinese
Cross-bow.--The ancient Balista.--Skull of the Crocodile.--Bones of
young Children.--The Spiral Spring and its many Uses.--The
Toy-gun.--The Needle-gun.--Valved Brass Instruments.--Watch and
Clock Springs.--The Bed Spring.--Parallels in Nature and
Art.--Buffers of Railway Carriages.--Spring Solitaires.--The Bell
Spring.--Spiral Springs in Vegetable Tissues.--Poison Cells of
various Marine Animals.--Effects of the Spiral Springs.
ELASTIC SPRINGS.
Here we come upon a subject so large, that it is difficult to define its
exact requisite limits. The principle of the elastic spring pervades all
Nature, and the numerous adaptations in Art are closely, though perhaps
not directly, attributable to the wide distribution of the spring in
Nature.
There is, for example, the simple elasticity which enables a tree, when
bowed by the wind, to spring back so soon as the pressure is removed,
and which, indeed, is the power which enables a bow to propel an arrow.
Then there are spiral springs innumerable, many of them so minute that
they can only be seen by the aid of the microscope, and there are many
springs which exhibit their elasticity by their power of extension and
shortening, just as is done with the elastic fabrics which are so much
in vogue at the present day, and which seem so necessary to ordinary
comfort that we feel disposed to wonder how our forefathers managed
without them.
We will now proceed to examine some of these springs in detail.
* * * * *
THERE is one form of elastic spring which has of late years become more
familiar than agreeable, namely, the toy which is learnedly called a
“catapult,” though it has little in common with the ancient weapon whose
name it bears.
As may be seen by reference to the illustration, it consists of one or
more india-rubber straps attached to a fork-like handle, and carrying a
small pouch in which is contained the missile. Although it is not
remarkable for accuracy, it can throw a stone or a bullet a considerable
distance, and its power can be very quickly increased by adding to the
number of the straps. Thus a catapult has been made which was capable of
sending a small pistol bullet through a wooden board, so that the
child’s toy might really become a dangerous weapon.
Indeed, cases are known where the catapult has hurled a stone with fatal
effect upon human beings. In my own neighbourhood there are many
examples of glass being pierced by stones thrown from catapults just as
if they had been subjected to bullets shot from firearms, the holes
being quite small and round.
The power of accumulating force by increasing the number of springs was
utilised by Mr. Scaife, when he invented his wonderful photographic
machine which he termed the “Pistolograph,” on account of the sound
which was produced when the portrait was taken.
The idea was simple enough, though the practice of it was not so easy.
He wished to be able to take a photograph with an exposure of the least
possible time, and thus to attain freedom and action, instead of the
dull stiffness which generally characterizes photograph portraits. The
mode which he adopted was by introducing a peculiarly sensitive film,
which would take an impression in a mere moment, and then arranging the
machine so that an exposure of more than a moment was impossible.
This was done by covering the lens with an exactly fitting door,
revolving on a pivot. The axis on which the door revolved was attached
to a number of india-rubber bands, exactly like those which are used for
confining papers. As the power of the springs increased with their
number, it naturally followed that the rapidity of the revolution was in
exact ratio with the number of the bands, so that the duration of
exposure to light could be measured with tolerable accuracy.
So wonderfully well did this plan succeed that photographs of eclipses
were taken with perfect accuracy, a matter of great importance when time
has to be considered. Horses were also taken at full gallop, so as to
display their action, and the crowning achievement was the photographing
of a cannon in the act of firing, and the bursting of a charged shell.
So rapid is the action of the instrument, that in several cases where a
cannon or mortar had been photographed, even the track of the ball or
shell is visible.
[Illustration: LEAF-ROLLING NESTS.]
[Illustration: CATAPULT.]
It necessarily followed that when the springs caused the circular cover
to revolve with such rapidity, they made it close with a sharp report,
and so gave rise to the name of the machine. Moreover, as it had to be
used for rapidly moving objects, it was not fixed on a pedestal, but was
held in the hands, while aim was taken at the object, just as with a
pistol. When the observer thought that he had his aim correct, he
touched a trigger, round spun the cover, and the photograph was taken.
* * * * *
ON the right hand of the illustration is seen the Catapult, made with
several springs, and on the left is shown an example of the Accumulator
as formed by Nature.
The reader may probably be acquainted with the Leaf-rolling
Caterpillars, of which there are so many. I had often inspected these
curled leaves, and, on comparing them with the size of the
caterpillars, had noticed that the muscular strength of the insect was
quite inadequate to the work which was done. That much of it was owing
to the “bowsing” system, which has already been described when treating
of the Toggle-joint, was very probable, but that some other force must
be employed was evident.
On unrolling a leaf, the hidden force was at once explained, and showed
itself to be a system of accumulators exactly like those of the
pistolograph or the catapult. The caterpillar spins successive belts of
silken threads, and affixes them to the leaf, as shown in the
illustration. These threads are nearly as elastic as the india-rubber
bands of the catapult, and accordingly draw the leaf together. Another
set of belts is added above the former, and, as they harden and contract
in the air, they roll the leaf still further. The first row is then
shortened and tightened, and a third and fourth row are added in the
same fashion. So elastic are these belts, that if the leaf be carefully
handled it can be almost wholly unrolled, and will spring back again as
soon as the force is removed.
* * * * *
ANOTHER form of accumulated force may be seen in the ordinary Carriage
Spring, one of which is shown in the illustration. It is made of a
number of strips of elastic steel lying upon each other, and suffered to
play upon each other by means of slots and rivets. The weight being
placed in the centre, it is evident that this very ingenious spring is
really an elastic girder, yielding to sudden pressure, and recovering
itself when that pressure is removed.
* * * * *
INGENIOUS as is this spring, it has many parallels in Nature, one of
which is here given.
It is popularly thought the hoof of the horse is a solid mass of horn
destined to protect the feet against hard and rough ground. Such
certainly seems to be the opinion of farriers, who, in shoeing horses,
act exactly as if the horn of the hoof were structureless; whereas it is
a marvel of complicated mechanism. On looking at the exterior of a
horse’s hoof, it will be seen to be marked with a vast number of very
fine, but easily visible longitudinal lines, looking as if they were
scratches from a very fine needle. If the hoof be removed from the
foot, and examined upon the interior, it will be seen that each of the
apparent scratches signifies the edge of a very thin plate of horn, not
so thick as the paper on which this book is printed. The hoof, in fact,
is built up of multitudinous plates of horn, set side by side, and each
acting as a separate spring. It is this beautiful structure which allows
the horse to tread without a jar being sent through its whole system by
every step which it takes.
A similar structure is to be found in all hoofed quadrupeds, and is
especially noticeable in the case of the Elephant. All those who have
watched the walk of an Elephant, no matter what its size may be, must
have been struck with the curious noiselessness of its movements. Its
weight may be measured by tons, and yet the enormous animal steps as
noiselessly as a cat. On examining one of the hoofs, after it is removed
from the foot, the cause of this marvellously silent tread is perfectly
evident. The whole of the hoof is composed of nearly parallel horny
plates, and by their united action they produce the required result.
[Illustration: HORSE-HOOF.]
[Illustration: CARRIAGE SPRING.]
Each plate in itself is very feeble, but, when united as they are at the
ends, they afford mutual support to each other. Similarly the separate
feathers in a couch would be crushed by a comparatively slight weight,
but when a number are confined together they support each other, and
form the soft, yielding couch with which we are so familiar. Horsehair,
when used as the stuffing for a couch or chair, acts in the same way,
and so do the fine filaments of wool when used under the name of
“flock.”
Another good example of the power of accumulated force, although it has
no direct relation to the spring, is the well-known fact that fungi,
which are separately so fragile, are capable of lifting and retaining in
the air stones so large that two men could hardly carry them. Were the
stones laid down upon the fungi, the latter would be crushed, but, as
they grow beneath the stones, they accumulate their powers, and slowly,
but certainly, raise the weight from the ground.
* * * * *
THIS very principle of accumulated force has long been used in weapons
of war, and I possess several examples of such weapons. One of them is a
Chinese repeating Cross-bow, which was taken at the capture of the Peiho
Fort, and was really a formidable wall-instrument, carrying a reserve of
arrows, and delivering them with great rapidity. In point of fact, it
consists of three bows, placed upon each other, and playing upon each
other just as do the portions of a carriage spring. Such strength is
thus obtained, that the bow cannot be drawn by hand, but is worked with
a lever, as shown in the illustration. The whole machinery of the
weapon, including the self-notching and self-supplying system, is very
interesting, but is outside our present object. The very powerful bow of
the ancient Balista was made on the same principle, and was strong
enough to throw large stones and wooden beams.
[Illustration: JAWS OF CROCODILE.]
[Illustration: CHINESE CROSS-BOW.]
I also have bows in my collection which are strengthened on the same
principle, though not exactly in the same manner. There are several
Indian, Chinese, and Japanese bows which are curved almost like the
letter C, and have to be reversed when strung. These bows are of no very
great size, but possess wonderful elasticity. They owe the latter
quality to sundry layers of sinew which have been affixed to the back
when wet, and which add enormously to the power of the bow, while they
very little enlarge its dimensions.
Another bow, made by the natives of Vancouver’s Island, has the back
strengthened by a number of cords spun from sinew fibres, and possessing
the strength and elasticity to which we are accustomed in the strings of
the harp, guitar, or violin.
* * * * *
WE will now turn to a parallel in Nature. This is to be found in the
lower jaw of the Crocodile, as is pointed out by Professor Owen, in his
work on the “Skeleton and the Teeth.”
All persons who have a smattering of anatomy are aware that even in the
human body the most solid bones of the adult were originally composed of
several pieces, and that they only become fused together in course of
time. The jaw-bones, for example, were once so composed, and in the
Crocodile the junction is never completed, the pieces of bone remaining
separate, but being pressed firmly against each other during life.
I have now before me the skull of a Gangetic Crocodile, in which,
although the animal was an adult when killed, the bones of the long
lower jaw are so loose that unless they were tied together the jaw would
fall to pieces.
This analogy between Art and Nature is thus described by Professor Owen
in the work which has just been mentioned:--
“The purpose of this subdivision of the lower jaw-bone has been well
explained by Conybeare and Buckland, by the analogy of its structure to
that adopted in binding together several parallel plates of elastic wood
or steel to make a crossbow, and also in setting together thin plates of
steel in the carriage spring.”
Dr. Buckland also adds: “Those who have witnessed the shock given to the
head of a Crocodile by the act of snapping together its thin, long jaws,
must have seen how liable to fracture the lower jaw would be were it
composed of one bone only.... The splicing and bracing together of thin
flat bones of unequal length and of varying thickness afford
compensation for the weakness and risk of fracture that would otherwise
have attended the elongation of the parts.”
A good example of the value of this structure of bone may be found in
young children. Before they are old enough to take care of themselves
they are perpetually falling down, and never hurting themselves. I have
seen a little girl of five years old roll from top to bottom of a lofty
staircase. It looked as if the child must be killed, but she was only
giddy with her many revolutions, and a little bruised about the elbows.
The reason of this curious immunity from injury is, that the bones,
especially those of the skull, are not completely united, and so act on
the principle of the compound spring.
THE SPIRAL SPRING.
This subject is so large, and there are so many examples, both in Art
and Nature, that it is not very easy to make selections which will
sufficiently answer the purpose.
[Illustration: WATER-LILY. LILY. POISON-CELL OF HELIANTHOID.
ANTHEROZOIDS.]
[Illustration: SPIRAL SPRING. BED SPRING. WATCH SPRING.]
The upper left-hand figure of the illustration represents the ordinary
Spiral Spring made of wire, and used for its power of resuming its shape
when compressed. In early childhood most boys have had practical
experience of this spring in the toy guns and cannons with which they
are supplied. The spring is compressed by the ramrod, and held in its
place by a catch. If a pellet be placed in the gun, and the catch
released by pulling the trigger, the spring flies back to its former
shape, and drives the pellet.
An exactly similar spring is used in the well-known “Needle-gun,” the
spring driving a needle through the explosive mixture, and so igniting
the charge.
Our brass instruments would be very badly off without the spiral spring,
which is placed under the pistons. The elasticity allows the pistons to
be pressed down, and when the fingers are raised the pistons spring up
again.
Another form of this instrument is seen on the right of the ordinary
spring. This is used in the manufacture of spring mattresses and
couches, and is made thinner in the centre, so as to allow of greater
elasticity.
Below them is the spring which is used for watches and clocks, one end
being fastened to the rim of the barrel, and the other to the pivot.
When the latter is turned the spring becomes “wound up,” and, when
released, keeps the works going by pressing against them. Of the
“pall-and-ratchet” wheel, by which the movements are retarded, we shall
treat in another place.
* * * * *
ON the left hand of the illustration are a few figures of the Spiral
Spring as seen in Nature.
On the extreme left of the group is a spiral cell taken from the
flower-stem of the Water-lily. As the reader will see, it is composed of
a number of fibres laid parallel to each other, and twisted into a
hollow spiral. In order to exhibit its shape the better, the spiral has
been partially uncoiled.
On the extreme right is a corresponding spiral cell from the common
Lily, in which the spring power is given by two fibres twisted in
opposite directions. The reader will now understand and admire the
mechanism by which these plants attain their great strength and
elasticity, the stems being made of myriads of these spiral fibres.
The oval body on the upper part of the illustration is a poison-cell of
a marine polyp, and is given here as an example of an animal spiral
spring, the others all belonging to the vegetable world.
We shall see more of its structure a little further on, and will not now
examine it in detail.
The two remaining figures represent the remarkable objects called
Antherozoids, _i.e._ the living creatures of anthers. They exist in vast
numbers in the non-flowering plants, and inhabit those parts which
correspond with the anthers of the flowering plants. When placed in
water they have a curious way of coiling and twisting themselves
spirally, so as to make their way through the water in a tortuous, but
tolerably rapid, course. This movement is effected by the contraction
and expansion of the spirally twisted filament. The upper figure
represents a group of Antherozoids in their cells, and the lower is a
much more magnified figure of a single Antherozoid as it appears when
free, and in the act of moving through the water.
* * * * *
ON the accompanying illustration are many examples of Spiral Springs,
both natural and artificial. We will take these in their order.
The upper left-hand figure represents the “Buffer,” by which the
carriages of railway trains are prevented from jarring against each
other.
Perhaps some of my readers may be old enough to remember the days of the
old railway carriages that were connected by short chains, and furnished
with buffers that were merely padded. As the train started a separate
jerk was given to every carriage by the tightening of the chains, and,
as it stopped, all the carriages bumped against each other in a most
unpleasant manner. Now, however, the buffers are furnished with powerful
springs, and are pressed strongly against each other by means of
screw-bolts, so that they form one continuous line.
In fact--and here is another analogy between Art and Nature--a train,
when properly made up, bears a close resemblance to a human spine, the
carriages being analogous to the vertebræ, and the spring buffers to the
elastic cartilages between the vertebræ.
Nowadays, owing to this arrangement, the whole train moves together, and
can be started and stopped so gently that the passengers are hardly
aware of movement or stoppage. For example, one of my friends was in a
train which came into collision with some obstacle. The carriages in
front were dashed to pieces, and several of the passengers killed. His
carriage, however, which was nearly at the end of the train, and had the
benefit of all the springs, was hardly shaken, and the inmates did not
know for some little time that an accident had occurred.
[Illustration:
BUFFER OF RAILWAY ENGINE. MOSS DISCHARGING SPORES.
SUPPORTING SPRING OF RAILWAY CARRIAGE. TENTACLE, WITH SPRINGS.
SPRING SOLITAIRE. SPRING-CELL OF MADREPORE. SPRING-THREAD OF
SEA-ANEMONE. SPRING-CELL OF CORYNACTIS.
BELL SPRING.]
Below the buffer is a Wheel Spring, made exactly on the same principle,
but set perpendicularly instead of horizontally.
* * * * *
THE two figures beneath the wheel spring represent an object very
familiar to us, namely, a Spring Solitaire, one figure showing it as
open, and the other as closed. In this article the clasp is held in its
place by a spring, and is only released by pressure.
* * * * *
BELOW the solitaire is a very prosaic application of the Spiral Spring,
namely, that by which a house-bell is kept in vibration after the force
of the pull has ceased, and which renders the bell, as Dickens happily
remarks, so greedy to ring after it has been pulled.
I made and employed a spring of a similar character in closing the door
of my parrot’s cage. Polly is a wonderfully clever bird, and a capital
talker. First, she had a cage with upright bars, two of which could be
slid upwards by way of a door. She soon found out the trick of the bars,
and used to escape, carefully replacing the bars afterwards.
When she was transferred to a metal cage, she discovered that the door
slid upwards, and began at her old tricks. So I took a piece of
galvanised iron wire, coiled it into a spiral spring, fastened one end
to the upper part of the door, and the other by a hook to a staple at
the bottom of the cage. Consequently, when Polly lifted the door, and
loosened her grip for a fresh hold, the door closed itself again. So,
after awhile, Polly gave up the door, and now never tries to open it.
* * * * *
PASSING to the upper right-hand corner of the illustration, there is
shown a portion of Moss as it appears when magnified, and discharging
its spores. When they are ripe a vast number of little spiral springs
are let loose, and shoot the sporules into the air.
* * * * *
BELOW the moss are four figures, which are, in fact, the same object
differently magnified, and seen from different points of view. These
peculiar organs are technically termed “cnidæ,” from a Greek word which
signifies a nettle. The appropriateness of the name we shall presently
see.
I have already mentioned that the tentacles of various marine animals
are furnished with poison-cells. The object of these cells is to
capture and kill the prey, and the mode of doing so is very remarkable.
On the right and left of the illustration are two such bodies, in which
is seen a sort of elastic wire coiled spirally, apparently without
regularity, but really possessing a most beautiful order. That on the
left is the poison-cell of a Madrepore, and the other is the same organ
in a Corynactis. No sooner is the tentacle touched than the poison-cells
are mechanically acted upon. They are turned inside out, and the coiled
spring darts forth with wonderful violence.
Slight as is the dart, so fine that it cannot be seen except with the
aid of a tolerably powerful microscope, it is a terrible weapon.
Although it is projected with sufficient force to bury itself to its
base even through so tough an object as the human skin, it could inflict
but little injury, and would, indeed, scarcely be felt. But it carries
with it a most irritant poison, which is apparently contained in the
little capsule. These cnidæ are very plentiful in the tentacles of the
Stinging Jelly-fish, or Stanger, as it is often called, and are charged
with a terrible poison.
As is the case with all such poisons, its effects differ according to
the constitution of the being that is poisoned. There are some persons,
for example, who care no more for the sting of a bee than for the prick
of a needle, and there are those whom a single bee-sting will bring
almost to the gates of death. So with the tentacles of the Stinging
Jelly-fish and those of the Portuguese Man-of-war, and there are persons
who are scarcely affected with the sting of the scorpion.
So it is with nettles. When I was a boy at school it was thought
necessary to wear an oak-leaf, or at least a portion of an oak-leaf, on
the 29th of May, and all who did not possess this talisman might be
flogged with nettles by those who did. As the school was situated in the
north of England, where the oak puts forth its leaves late in the
season, it was no easy matter to obtain a veritable oak-leaf, and we
used to take any leaf that we could procure, and cut it round the edges
into the similitude of a suitable oak-leaf.
The effect of the nettles upon the boys was most curiously diversified.
Some cared nothing whatever for them; others suffered sharp but brief
pangs; while others, of whom I was one, endured the most lancinating
pain at the time, and for hours afterwards a hot, burning, fevered skin,
and a heavy, dull ache, accompanied by throbbings of the brain so
violent that it appeared as if the head would burst asunder at every
heart-beat.
The fact of this inequality has been throughout life a valuable lesson
to me, _i.e._ that a punishment which will nearly, if not quite, kill
one man, will be no punishment at all to another.
Of course I cannot answer for the effects of these very minute cnidæ
upon others, but I can state that they nearly killed _me_, and that if I
had been forced to swim another hundred yards, I should have collapsed,
sunk, and had a coroner’s jury return a verdict of “Found drowned in
consequence of cramp.”
On me the effects were as follows:--First a slight, and then a severe,
tingling on the parts which had been struck. Then sharp, darting pangs.
Then a sudden shock as if a bullet had passed through the breast from
one side to the other. Consequent collapse, and suspension of the office
of both heart and lungs. I once had to walk nearly two miles after being
stung by one of these dread animals, and how often I fell before
reaching my lodgings I dare not say, but certainly once in every two
hundred yards.
Even after partial recovery I should not have known my own face. It was
that of an old and wearied man of seventy, grey, wrinkled, and withered;
and many months elapsed before I felt myself sure that the weird-like
bullet would not drive through my breast, and leave me lying on the
ground gasping and speechless.
These dreaded tentacles can sting as fiercely when separated from the
animal as when they are conjoined to it, as I can also testify from
personal experience.
I have a natural alacrity in damaging myself, and there is scarcely a
representative bone in the body that I have not fractured or dislocated,
or both. Fortunately the cerebral vertebræ have hitherto escaped. I have
broken the right leg, right arm, two ribs, and right collar-bone;
dislocated the right ankle, and smashed nearly every bone of the right
hand. At present, the damage to the left side is restricted to two ribs;
and I hope that the Genius of Ossifraction may now be content with his
work.
But I equally seem to have a natural affinity for the tentacles of the
Stangers, which deliver their envenomed darts just as fiercely when they
are separated from the Medusa as when they are connected with it.
A curious example of this fact befell me in the present year (1875).
Seeing that there had been a steady southern gale, which made Lundy
Island and Hartland and Baggy Points indiscernible, I dreaded my old
foes, and, instead of bathing from the “Pebble Ridge,” took to the great
“Nassau” Baths at Westward Ho. I sadly missed the roll of the waves, and
the placid rapture of lying with outspread arms as the vast Atlantic
billows came rolling in, flinging up the great grey boulders as if they
were corks, and letting them roll down the ridge again with a
thundering, and yet soothing, sound. Three miles or more inland may the
thunder of the Pebble Ridge be heard; and at night, even though a storm
be raging, tearing the leaves off the trees in whirling showers,
flinging great branches into the air like ostrich plumes, and howling so
that one person can hardly hear another speak, the dull, low, continuous
thunder of the Pebble Ridge is heard over all. I have often remained
awake at Bideford, simply on account of the deep roar of the Pebble
Ridge, as the rising tide rolled its vast waves along the coast from
Baggy Point, through Westward Ho and Clovelly, to Hartland.
When there is a heavy sea, the “undertow” of these waves is so great
that even had no such things as Stangers existed, I should not have
ventured upon the Pebble Ridge. One of my friends, a strong swimmer, was
nearly drowned off that ridge by the undertow; and not long before I
visited Westward Ho a promising young man lost his life within a few
yards of that treacherous shore.
Much against my will, I went to the new bath, which is always supplied
with a running current of sea-water; and I had hardly swum the length of
the bath before I felt the familiar nettle-like sting in my foot.
Fortunately it was only caused by a small fragment of a Stanger’s
tentacle, which had been severed from the animal and pumped into the
bath, and no harm ensued.
USEFUL ARTS.