THE STOPPER, OR CORK.--THE FILTER.
Vessels and their Covers.--Corks.--Mode of bottling Wine.--Conical
Corks and Stoppers.--Self-fitting Candles.--Candle-fixers.--The
Vent-peg.--The Blow-guns and their Missiles.--The Serpula and its
Conical Stopper.--The Filter.--The Bosjesman procuring Water.--How
to make a simple Filter.--The Earth as a Filter.--The Sea-mouse, or
Aphrodite, and its filtering Apparatus.--The Duck’s Beak, and its
beautiful Structure.--The Jaw of the Greenland
Whale.--Fork-grinder’s Respirator.--How Insects
breathe.--Spiracles, and their general Structure.--Spiracle of the
Fly.--Experiment upon a Cockroach, and its Result.
THE STOPPER, OR CORK.
This object, as depicted in the illustration, is a product of civilised
life, though, as soon as a savage could make a vessel, he seems to have
made a Cover for it if it were of large diameter, or a Stopper if the
opening were small. Even the very Bosjesman, who is quite unable to make
a clay vessel, and uses empty ostrich eggs by way of water-bottles, is
yet capable of making plugs with which he can stop up the apertures.
Then the Kafir, with his gourd vessels, whether they be for water or
snuff, makes a plug that fits tightly enough to exclude the air, as well
as to retain the contents.
The invention of glass bottles necessarily brought with it the
introduction of a new kind of plug, and a material for such a plug was
found in the bark of the cork-tree, a species of oak. This bark
possesses the capability of compression to a very great extent, and,
being highly elastic, it expands as soon as the pressure is removed.
Thus, in bottling wine, the corks are always made much too large to go
into the mouths of the bottles. They are first dipped in a cup
containing the same wine, and are then compressed violently by a machine
worked by a handle, and which, being practically a powerful pair of
nut-crackers with a rounded gripe, must suit the shape of the cork. It
is then taken out of the machine, and, before it has had time to expand,
is rapidly fitted to the neck of the bottle, and driven home with a
wooden mallet. Expansion then takes place, and the bottle is rendered
air-tight, so that no damage is done to the wine.
If the whole of the wine were to be drunk when the cork was removed,
this plan would be amply sufficient. But there are many cases where the
bottle is opened, and only part of the wine consumed. To re-cork the
bottle would be too troublesome, and to leave it uncorked would spoil
the wine. So the Conical Stopper was invented, which fits the neck of
any ordinary wine-bottle, according to the depth to which it is
introduced, and, by a slight screwing movement, sufficient compression
is obtained to render the bottle air-tight. One of these Conical
Stoppers is shown in the illustration on page 352. Sometimes they are
made of cork, and sometimes of india-rubber; but the principle is the
same in either case.
Perhaps some of my readers may have seen the Self-fitting Candles, which
require no paper to make them fit the candlestick. These are enlarged at
the base, which is made in a conical form, and slightly grooved. The
“Candle-fixers” that are so much in use at the present day are made
exactly on the same principle, being hollow cones of paper, which take
the place of the solid cone.
The Vent-peg of casks is another instance of the cone used as a stopper.
Another example is to be found in the Blow-guns and Arrows of tropical
America. In some districts the base of the arrow is fitted with a
conical appendage of light cotton, rather larger than the tube, but
capable of compression, so that it exactly fits the tube when pressed
into it. In other districts the cone is hollow, and made of some thin
and elastic bark.
Some years ago one of our most eminent gun-makers hit upon the same idea
while making improved missiles for the game of “Puff and Dart,” and very
much surprised he was when I showed him the South American arrow, not
only with the same hollow cone at the base, but having also spiral
wings along the shaft, so as to give it a rotatory motion as it passed
through the air. The hollow cones of his darts were made of
india-rubber, but the shape of the two was identical.
* * * * *
IF the reader will refer to the left-hand figure of the illustration, he
will see a beautiful example of the Conical Stopper as existing in
Nature.
This is the “Stopper,” as it is popularly called, and, scientifically,
the “infundibuliform operculum.” I prefer the former term myself, as
being less liable to misapprehension.
The Serpula lives in a shelly tube of its own construction, and has the
power of protruding itself when it desires to obtain food, and of
withdrawing itself within the tube when alarmed. This movement is
performed so rapidly, that the eye can scarcely follow it, and the
mechanism by which it is done has already been described when treating
of War and Hunting.
[Illustration: ANTENNA OF SERPULA.]
[Illustration: CONICAL STOPPER.]
When it withdraws itself, the Stopper closes the mouth of the tube with
perfect exactness, so as to leave the inhabitant in safety. The reader
will see, on referring to the illustration, how exactly similar is the
Conical Stopper of Art to that of Nature, and how the inventor of that
article, as well as of the self-fitting candle, the candle-fixer, the
blow-gun arrow, and the vent-peg, might have found prototypes of their
inventions in Nature, if they had only known where to look for them.
THE FILTER.
Even in a state of uncivilisation man has been driven to invent a Filter
of some kind.
The simplest kind of Filter is that which is used by the Bosjesman
women when procuring water for the use of their families. When, as often
happens, the only water to be obtained is to be found in muddy pools
which have been trampled and perturbed by thirsty animals, the women
have recourse to a simple, though rather repulsive, expedient.
Each woman is furnished with empty ostrich egg-shells by way of
water-vessels, and she also takes a couple of hollow reeds. Over the end
of one of these reeds she ties a bundle of grass, and then plunges it as
deeply as she can into the mud. After a little while she sucks up the
water through the tube, the grass acting as a filter, and she then
discharges it by the second tube into the egg-shells. In this way the
women will obtain water, where none but themselves could have procured
it. As to the repulsive mode of obtaining it, no one can be fastidious
when dying of thirst. Sir S. Baker mentions that when he was on his
travels he managed in a halt to save up enough water for a bath for
himself and his wife. He was about to throw away the soapy water, when
the vessel was snatched from his hands by two of his attendants, and the
contents eagerly drunk.
The different varieties of the Filter which we use at the present day
are too familiar to need description. Whether they be made principally
of charcoal, which is a powerful disinfectant, or of merely stones,
gravel, and sand, they are all constructed on the same principle,
namely, the straining out solid substances, and allowing only the pure
water to pass through the interstices.
* * * * *
AS to the Filters of Nature, they are almost innumerable. In the first
place, the Earth itself is the primary filter of all, taking into itself
all kinds of decomposing substances, separating them for the use of
vegetation, and delivering the pure, bright, and sparkling spring water
which we so highly and rightly value. The whole human body, again, is
practically a collection of the most elaborate and effective filters
that the mind of man can conceive. But we will pass to the more obvious
examples of filters as seen in animal life.
On the upper left-hand portion of the illustration may be seen a long,
fat, hairy creature, called popularly the Sea-mouse, and known to
zoologists as _Aphrodite aculeata_. Although it inhabits the mud--and
sea-mud is about as noisome a substance as can be imagined--it is
clothed with a garment of such beauty that the rainbow itself can
scarcely rival, and not surpass it. The hairs with which it is so
profusely covered glitter and sparkle with every imaginable hue, among
which red and green seem to be predominant.
These hairs occupy the sides of the body, but in the upper surface there
is a thick coating of felted hairs, interwoven with each other so
closely that they can with difficulty be separated. These hairs form a
natural filter, strain away the mud from the water, and allow the latter
to pour itself upon the organs of respiration. If, therefore, a specimen
be examined when it is first brought up by the dredge, the felted hair
will always be found to contain a considerable amount of mud, and much
washing is needed before the creature can be introduced into an aquarium
where the water is intended to be transparent.
[Illustration: APHRODITE. DUCK’S BEAK.]
[Illustration: FILTER.]
I may here mention that the name of Aphrodite is a singularly happy one.
It signifies something that arises from the foam of the sea, and was
given to the goddess of beauty, because in the ancient myths she was
said to have sprung from the foam of the sea. Unpoetical as it may
appear, the German word Meerschaum, which is so familiar to us in
connection with pipes, is the exact equivalent of Aphrodite.
* * * * *
BELOW the Aphrodite is a figure representing the filtering apparatus
which is found in the beak of the duck. This singularly beautiful
apparatus is well worthy of examination, and the more important details
of its structure can easily be made out by the unassisted eye.
In the first place, the upper half of the beak, or upper mandible, as
it is scientifically called, is furnished along its edges with a row of
curved horny projections, very like the teeth of a comb, and each of
them coming to a point. There are some fifty or sixty of these teeth on
each side, and they are regularly graduated in size, being longest in
the middle of the beak, and becoming very short at either end. They are
set diagonally, with the tips pointing backwards. The edges of the lower
mandible are turned up in a sort of fold, on the outside of which is a
row of grooves corresponding with the teeth of the upper mandible, and,
like them, being set diagonally.
These teeth and grooves would of themselves make a very efficient
filter, but they are further aided by the tongue. This is thick, fleshy,
and very mobile; so much so, indeed, that when the mouth is opened the
tongue is automatically thrust forward. The edges of the tongue are,
like those of the mandibles, furnished with a filtering apparatus.
Instead, however, of being horny and stiff like those of the mandibles,
they are membranous and exceedingly delicate. Indeed, in order to see
them properly, it is necessary to place the tongue under water, so that
the membranous filaments shall be floated apart instead of clinging
together by their own weight.
The whole of this apparatus is abundantly supplied with nerves, and is
evidently a most exquisite instrument of touch. The reader will now
understand the peculiar movements of a duck’s beak while feeding.
Although the bird can and does eat solid food, such as barley, and, by
reason of its superior width of beak, will very much defraud the poultry
in a yard where ducks and hens are kept together, it is chiefly fitted
for extracting nourishment from water, and will find abundant
subsistence where a hen would die of starvation.
When the beak is plunged into the water, the mandibles are rapidly
opened and shut, the tongue incessantly working backwards and forwards
between them. Consequently, not only are the solid parts of the water
strained between the comb of the upper beak and the grooves of the
lower, but they undergo a further sifting or filtering from the delicate
fibrils which fringe the edge of the tongue.
* * * * *
ANOTHER familiar example of the Filter is to be found in the jaw of the
Greenland Whale. In this animal, as well as in its congeners, the
“whalebone,” or “baleen,” as it is more properly called, is so formed
that it allows liquids to pass through it, while it retains solids.
Feeding as it does upon small marine matters, it would starve but for
the filtering power of the baleen, which enables the animal to take into
its vast mouth the sea-water with its inhabitants, and to expel the
water through the plates and fibres of the baleen, while retaining the
animals.
The process of filtering, as well as the structure of the baleen, is so
familiar that it does not need further description.
* * * * *
WE will now proceed to another filter, which is used in the air, and not
in water, namely, the Mouth-guard or Respirator of the fork-grinder.
There is, perhaps, no trade which is more destructive of human life than
that of the fork-grinder was until the peculiar respirator was made
obligatory. The minute particles of steel thrown off by the grindstone
fill the air, and were necessarily inhaled. Now, the human lungs are
capable of enduring very bad treatment, but the introduction of
steel-dust into them is more than they can bear. Consequently the
duration of human life was very short, consumption almost invariably
setting in at an early age, and carrying off the men before they had
achieved middle age.
Nor did the mischief end there. It was bad enough that life should be
shortened, but far worse that it should be wasted, as was mostly the
case. The men, knowing what their fate must be, were simply reckless,
and plunged into all kinds of debauchery, under the plea of “a short
life and a merry one.” They knew no better, and could scarcely be blamed
for their mode of living. And, as a matter of course, each succeeding
generation was worse, smaller, and feebler than the preceding.
Then there came the invention of the Magnetic Respirator, by which the
fork-grinder’s trade was rendered as healthy as any other. It was made
of steel-wire gauze, and magnetised, so that the floating particles of
steel were not only stopped in their progress to the lungs, but arrested
by the magnetism, and, so to speak, taken prisoners by it.
Even a well-made respirator of several layers, like those which are used
by persons suffering from weak lungs, would have been useful, but the
addition of magnetism doubled the efficacy while greatly diminishing the
cost, a single layer of wire being quite adequate to the office, and
was, in fact, quite a stroke of genius.
The value of this invention is at once shown by the many complaints
which the workmen made when the Respirator was first introduced. They
complained that the apertures of the Respirator became so choked that
they could not breathe. This was perfectly true, but the complaint
showed the real value of the instrument.
[Illustration: SPIRACLE OF FLY.]
[Illustration: RESPIRATOR OF FORK-GRINDER.]
It was necessary for the workmen, every now and then, to clear off the
innumerable particles of steel which adhered to the magnetised wires,
and impeded respiration. But they never seemed to realise the fact that,
if it had not been for these wires, all the particles would have been
drawn into the lungs, and gradually choked them up, brought on
inflammation, and extinguished their life altogether. And, with the
usual repugnance to new ideas which is inherent in undeveloped minds,
the men stoutly resisted the introduction of the Respirator, and did
their best to reject an invention which doubled the length of their
lives, and enabled them to find long happiness in the world instead of
brief pleasure ended by sure and painful death.
* * * * *
NOW, we will see how the principle of the Respirator is carried out in
Nature.
On the left hand of the illustration is drawn one of the most perfect
Respirators, or air-filters, if we may use the term, that can be
imagined. Perhaps some of my readers may know that insects do not
breathe as we do. They have no lungs, but their entire system is
permeated by air-vessels, just as is our system with blood-vessels, and
therefore the air, instead of being restricted to the lungs, is conveyed
to every part of the insect, the air-vessels extending to the very tips
of the wings and antennæ, and to the claws of the feet.
Neither does the insect receive the air through mouth or nostrils as we
do. Along the sides of the body are certain oval apertures called
“spiracles,” from the Latin word _spiro_, which signifies breathing.
These spiracles can easily be seen by examining an ordinary silkworm.
They are situated in the soft and flexible skin which connects the rings
or segments of which all insects are composed, and pass directly into
two large air-tubes which run on either side of the body.
It is evident that since an insect is so thoroughly permeated with air,
it must be furnished with means to render that air as pure as possible,
and at all events to preserve the respiratory system from being choked
with dust or other adventitious substances.
How important the air is to an insect can easily be seen by dipping it
in oil, or even brushing an oiled feather on its sides so as to fill up
the spiracles. A man under the hands of the hangman or garotter could
not die more swiftly, so much does an insect depend on air. In fact, an
insect is almost wholly composed of air-tubes, but for which the great
thick-bodied dor-beetles could never use their organs of flight.
Of course, although the spiracles can act as filters as far as the air
is concerned, they cannot be analysts, and consequently insects are
peculiarly sensitive to a bad atmosphere. There is, for example, the
well-known “laurel-bottle” of entomologists. A few young laurel-leaves
are crushed and placed in a bottle. As soon as an insect is introduced,
it breathes the prussic acid which is exhaled from the leaves, and at
once dies.
So it is with the more delicate “death-bottle,” into which a little
cyanide of potassium is introduced, and covered with plaster of Paris.
The plaster prevents the poison from touching the insects and damaging
their beautiful colours. It permits the deadly vapour to roll through
its interstices; consequently, even the large-bodied moths, which are
tenacious of life almost beyond credibility, can barely run round the
bottle, when they roll over, and expire almost without a struggle, the
venomous atmosphere having saturated the entire body.
All entomologists know that the spiracles act as sieves, preventing any
extraneous objects from gaining admission into the breathing-tubes. But,
unless they have had personal experience, they cannot appreciate the
efficacy of the spiracle when acting as a respirator. Even the
microscope, though it may magnify the object to any extent, does not
show the wonderful filtering power of the spiracle. The figure in the
illustration represents a spiracle of the common “blue-bottle” fly, and
any one who wishes to examine such an object for himself can have but
little difficulty in doing so, especially in the warm season of the
year.
How effectual is the barrier thus interposed by Nature between the
external world and the interior of the insect may be inferred from the
following narrative:--
Many years ago, while absorbed in the comparative anatomy of insect
structure, I believed myself to have hit upon a plan for injecting the
minutest of tubes with mercury. So I took a male cockroach, placed a
vessel of mercury in the receiver of an air-pump, and suspended the
cockroach exactly over it. As the reader will fully have surmised, my
idea was, first to exhaust the air from the inside of the insect, then
to plunge it into the mercury, and then to admit the air, which, at a
pressure of fifteen pounds to the square inch, was likely to drive the
mercury into the smallest of tubes. Such a plan was very successful with
ordinary tissues, and might succeed with insects.
Accordingly, I exhausted the air from the vessel in which the cockroach
was placed, and kept it in a state of exhaustion for a whole day, so as
to prove that every particle of air was withdrawn from the insect. I
then plunged the cockroach deeply beneath the mercury, and admitted the
air, hoping that the severe pressure would drive the mercury into the
respiratory vessels. But not one particle of the mercury could pass
through the wonderful filter with which the cockroach had been provided,
and, except that I had learned the power of the spiracle, I might have
saved both the time and trouble.
It is worthy of notice that, almost countless as are the species of
insects, no two of them possess exactly the same structure of the
spiracles, the individuality being marked as clearly in these tiny
organs as in the entire insect.
USEFUL ARTS.