WATER, AND MEANS OF PROCURING IT.
The Necessity of Water to Man.--Composition of the Human
Body.--Natural and Artificial Distillation.--The Traveller’s
Tree.--Pitcher-plants and Monkey-pots.--Stomach of the Camel, and
its Analogy to the Honey-comb.--Dewdrops.--Use of the Still at
Sea.--Perspiration and its cooling Properties.--The Turkish
Bath.--Perfume and Ether Spray.--Condenser of the Low-pressure
Steam-engine.--The Dry and Wet Bulb Thermometer.--Ice produced in a
red-hot Vessel.--Power of Water.--How Fountains are made.--Modern
System of Hydrants.--Hydraulic Mining.--The Victoria and Niagara
Falls.--Artesian Wells.--The Norton Tube, &c., in Abyssinia.--The
Water-ram and Spout-hole.
IT has often been remarked that man can live a comparatively long time
without solid food, providing that he can only obtain water, of which
the chief bulk of the human body is made. Dying by thirst is a horribly
painful death, but, according to Mr. Mills, the ill-fated Australian
traveller, “starvation on nardoo (an innutritious plant) is by no means
unpleasant, but from the weakness one feels, and the utter inability to
move one’s self.”
Those who have been shipwrecked, and unable to obtain fresh water, have
always found that the tortures of thirst were infinitely harder to
endure than those of hunger; and the reader will probably remember that
those who perished in the Black Hole of Calcutta owed their deaths
chiefly to thirst, their bodies being exhausted of moisture by the heat
of the room, and no fresh supply attainable.
Civilisation especially shows itself in the way in which water is
brought within the reach of every one, even in the most crowded of
cities. The reader may probably call to mind the wonderful aqueducts of
ancient Rome, the gigantic remains of which still exist. Then, as to
our own country, we are all practically acquainted with some water
company, by which the water, more or less purified, is brought into our
houses, and can be obtained by the mere turning of a tap.
Yet all this ingenuity is but a following of natural prototypes, as will
presently be seen; and even the familiar Water-tank, as shown at the
right hand of the illustration, has been anticipated by Nature.
* * * * *
ON the left hand of the illustration there are three examples of natural
water-tanks, two belonging to the vegetable, and one to the animal
kingdom.
[Illustration:
TRAVELLER’S TREE.
STOMACH OF CAMEL.
PITCHER-PLANT.
CISTERN.]
That on the extreme left, with a number of radiations, represents a
portion of a Madagascar palm, popularly called the Traveller’s Tree.
Having very large leaves, arranged in the manner there shown, the
Traveller’s Tree condenses the nightly dews, and allows them to trickle
down into the hollows of the leaf-stems.
There the water remains, out of the reach of sunbeams or wind, and if a
traveller happens to be thirsty, all he has to do is to pierce the base
of one of these gigantic leaves, and out rushes a stream of the purest
water, as is shown in the illustration.
* * * * *
NEXT to the Traveller’s Tree is shown one of those extraordinary
vegetables called Pitcher-plants, from the strange conformation of the
leaves. They inhabit Borneo, Siam, and other hot countries. In these
remarkable plants some of the leaves are developed into suitable
pitchers, with hinged lids, exactly like our hot-water jugs. They serve,
however, a different office, and contain cold water which the plant has
distilled from the dew.
As the monkeys are in the habit of resorting to these plants when
thirsty, they are sometimes called Monkey-pots. There is an admirable
account of the Pitcher-plants and their development in the _Transactions
of the Linnæan Society_, vol. xxii. part iv. The scientific name of
those plants is Nepenthes.
* * * * *
BELOW the vegetable comes a rather celebrated animal cistern, namely, a
portion of one of the stomachs of a Camel.
It exactly corresponds with that part of an ox which butchers call
“honey-comb tripe,” and consists of a multitude of cells, which can be
closed or opened at will. When the camel takes in its provision of
water, it can treat this portion of the stomach much as the hive bee
treats the honey-bag, and fill its cells with water.
By degrees, when it finds the necessity for moisture, it can squeeze the
water out of these receptacles into the digestive portion of the
interior, and so can sustain life for a wonderfully long time under
conditions which would kill any other animal. I may remark, by the way,
that the amount which a camel can drink, and the length of time through
which it can endure its desert life, have been much exaggerated. There
is another point to be considered, namely, the curious resemblance
between these cells and the honey-comb of the hive bee. Every one knows
that honey, no matter how tightly closed, will crystallize and lose its
best qualities if kept in jars, whereas if it be allowed to remain in
the waxen comb, where it is divided into very small portions, it will
remain good for years.
It is just the same with the cells of the camel’s stomach, they being
able to preserve water in a pure state by distributing it among a number
of small cells, which can be opened or closed at will.
Then we come to the various means of obtaining water.
Reference has already been made to the Filter, by which foul water can
be made pure for human consumption, and we will therefore pass to
another mode of obtaining pure water, namely, the Still.
In former days, if there were a failure of the supply of fresh water on
board ship, the whole of the occupants must necessarily perish. Now,
however, no such danger exists, as every well-furnished ship carries at
least one Still, by means of which the sea-water can be made to abandon
its salt, and to give out nothing but pure water fit for drinking.
Even in cases where no regular Still has been on board, an extemporised
Still has been made from a kettle, a gun barrel, or piece of lead
piping, or anything of a similar nature.
[Illustration: DEWDROPS.]
[Illustration: STILL.]
The principle of the Still is simple enough, and is shown by the
diagram, rather than drawing, on the right hand of the illustration.
There is a vessel in which liquid is boiled. From the upper part of it
rises a tube through which the steam must pass as it is generated. The
tube in question is generally of considerable length, and is coiled
inside a vessel filled with cold water, rendered colder by ice, if
possible.
As the steam passes through the cold tube condensation takes place, and
it becomes liquid again, but deprived of its heavier particles, so that
if sea-water be placed in the still, the salt is left in the vessel, and
nothing but pure water passes through the tube. In dissecting-rooms a
small still is almost invariably kept. Many preparations are of such a
nature that the spirit in which they are placed becomes discoloured, and
has to be repeatedly changed. Now, even methylated spirit is an
expensive article, and therefore, instead of being thrown away, the
discoloured spirit is placed in the still, and reproduced in a clean and
transparent state.
Nature affords innumerable examples of distillation, the chief of which
are the Dewdrops which have already been mentioned. During the daytime
the air is full of moisture drawn by the sunbeams from ocean. We cannot
see it, but it is there, and when the chill of night cools the various
trees, herbage, and other such objects, the aërial moisture is condensed
upon them, which is then known by the name of Dew.
On the left hand of the illustration are shown the tiny Dewdrops as
hanging on the slight threads of a spider’s web, and collected in larger
drops upon a leaf.
* * * * *
THERE are many other familiar examples of the principle of condensation,
the commonest of which is the so-called steam as it pours from the spout
of a kettle. In point of fact, it is not steam at all, but only water
condensed into very small drops. At the orifice of the kettle it is
quite invisible, but when it passes into the air, and is condensed, the
tiny globules become visible. The same fact may be noticed in the
Napier’s Coffee Machine, which has already been mentioned. When the
water is boiling in the glass globe no steam is visible, though the
upper portion of the globe is entirely filled by it. But, no sooner is
the cork removed, and the steam allowed to escape, than it at once
becomes visible as a white cloud, being, indeed, a miniature copy of the
rain-clouds that float above us.
* * * * *
THEN there is that mostly invisible passage of liquid through the
multitudinous pores of the body, which is generally known as
perspiration. It is invisible in warm weather, but on a cold day is as
visible as a rain cloud.
The Turkish Bath affords a good example of this fact. Sometimes the
hottest room attains a temperature of 250° or more, water boiling at
212°. When a bather goes into that room, he appears to have a perfectly
dry skin, the moisture being in the form of invisible steam, and swept
off as soon as it is generated.
But, if he passes at once into the cold room, he is so enveloped in
vapour that for a few moments he is wrapped in it as in a cloud, and
can scarcely be seen, the vapour having been condensed by the cold air.
[Illustration:
HEATED HORSE.
PERFUME SPRAY.
FREEZING BY EVAPORATION.
WET-BULB
THERMOMETER.]
A very familiar instance of this sudden condensation may be seen in the
streets of London on any winter day. There may be a couple of omnibus
horses, nearly at the end of their day’s work, and quite tired out.
Suddenly they are pulled up by the driver, and as suddenly disappear for
a moment or two, being concealed in a cloud of moisture proceeding from
their bodies. Of course in a hot day there is more of the moisture, but
the warmth of the atmosphere prevents it from condensation, and so it is
not visible.
One valuable property of the system of evaporation and condensation is
its cooling power. Thus it is that a person who is ill with fever tosses
about with a burning skin until the pores of the body act, and allow the
normal moisture to pass through them. Then the body cools by
evaporation, and the patient begins to amend.
So it is that the bather can endure in the Turkish bath a heat so great
that a glass of water, if held in the hand, would speedily boil, and a
piece of meat be cooked in about the same period. But, if the air were
not dry enough to carry off the perspiration, the bather would be
scalded to death.
A most valuable adaptation of the principle is shown in the little
glass machine for dispersing perfumes in the form of spray. In cases of
headache it is almost invaluable, the spray cooling the heated forehead,
like magic, and at the same time filling the room with the grateful
perfume.
It has even a greater claim to human gratitude, as I can personally
testify. I have the strongest objection to a surgeon’s knife, especially
when I know, from sad experience, that he is going to make very free use
of it. But, on the last occasion, I cared nothing for it, owing to the
happy invention called Ether Spray.
The effects were remarkable. First, a delicious cooling of a spot raging
with internal fires. Then it was rather colder than I liked. Then it was
much colder than I liked. Then it became almost too cold to bear,
reminding me of my childhood’s feet on the outside of the Birmingham
coach in the depth of winter.
Suddenly all sensation ceased, and the skin became white as parchment.
Out came the surgeon’s bistoury, and I looked at him with as calm
composure as if he had been whittling a deal plank. There was absolutely
no feeling whatever, the local nerves having been temporarily frozen, so
great is the power of evaporation. If it ever be my lot again to endure
cold steel, I shall have the ether spray.
* * * * *
ON the extreme right of the illustration is seen the “Wet-bulb”
Thermometer, which carries out the same principle, the thermometer being
double, and one bulb being covered with a wet envelope, while the other
is dry.
Below is one of the many inventions for making artificial ice, all of
them depending on the cooling power of evaporation. Perhaps some of my
readers may have seen molten iron poured over the human hand without
doing the least harm, or mercury frozen in a red, or rather a white, hot
vessel. Both these phenomena are due to the cooling power of
evaporation, which is made to act with extreme rapidity, and so absorbs
the heat until even mercury is rendered solid, and can be cast in a
mould like a leaden bullet.
* * * * *
IN the accompanying illustration we have an example of the Condensating
principle as applied to the steam-engine, and popularly known as the
“Low-pressure Engine.” In this case force is reconverted, so to speak,
and, if a cubic inch of water has been converted by heat into a cubic
foot of steam, creating a pressure in one direction, it can be
reconverted by cold, and so produce a pressure in another direction.
* * * * *
IT is owing to this fact that some parts of the world are always hot and
always wet, Guiana being a striking example.
[Illustration: RAIN-CLOUD.]
[Illustration: CONDENSER.]
The wind blows over the ocean, absorbing moisture as a sponge does
water. As it passes from the sea over the land, it is met by secondary
mountain ranges, too low to arrest its progress altogether, and high
enough to have their summits clothed in eternal snows. As soon,
therefore, as the warm, water-laden winds pass over these mountains, the
moisture is condensed by their frozen tips, and down rushes the rain in
torrents.
Even in our own temperate land we can often trace the cause of a heavy
rain to the presence of a lofty hill, or even an exceptionally tall
spire. The moist climate of Oxford has been attributed by scientific men
quite as much to its spires and towers as to its low-lying situation.
* * * * *
NOW we come to the various modes of extracting the water which is laid
up within the earth, and which only slowly ascends to the surface when
drawn up by the heat of the sun.
Water is everywhere, but the depths at which it is found are vastly
different. For example, at one house in which I lived it was not
possible to dig for three feet without coming to water. In another, no
water was found within some two hundred feet, and, as I several times
relieved the old gardener of the task of drawing the water for the day’s
consumption, I have reason to remember the depth.
[Illustration: SPRING.]
[Illustration: FOUNTAIN.]
The pail, rope, and winch which were in use at that time--and may be
still, to the sorrow of the gardener--are but a sort of semi-savage way
of procuring water from the depths of the earth. It is a well-known fact
that under certain conditions water always finds its own level, _minus_
the friction of the channel through which it passes. On this principle
all fountains are made. Those, for example, at the Crystal Palace, which
fling their waters to such a height, are fed from tanks on the summit of
the two great water towers. And, were it not for the friction of the
water in the tubes, and that of the air, the fountains would rise as
high as the tanks from which they are fed.
Such is the case with springs, especially with those of an intermittent
character, in which latter instance the rushing of the water is exactly
coincident with the filling of the hidden tank which supplies it.
The modern Hydrant system, which bids fair to supersede the cumbrous
machinery of fire-engines, even when worked by steam, is based on the
same principle. The water-tanks are placed at such a height that, when a
hose is attached, and the tap turned, the water can be thrown over the
roof of the highest building. Such hydrants have been attached to
Canterbury Cathedral since the fire which so nearly consumed that
magnificent and venerable building.
* * * * *
A VERY remarkable use has been made of this power of water in mining
operations. Most of my readers know that in gold mines the metal is
chiefly found scattered among quartz, one of the hardest of the
minerals. The usual plan has been to dig out the quartz, pound it to
powder with specially devised machines called “stamps,” to pass the
powder through mercury, which amalgamated with the gold, and gave it up
again on being heated to a certain temperature.
Now a different mode of mining is brought into operation, the pickaxe,
spade, and stamps, with all their expensive machinery, being abandoned,
and water made to do the duty of all three, some ingenious individual
having noticed the effect which water has on the hardest rock.
Such, for example, is the case with those wonderful Victoria Falls of
Africa, where the rushing water has cut its sinuous channel through so
many hundreds of yards of rock. Such, also, is the case with the more
celebrated, but not so wonderful, Falls of Niagara, which have been
gradually working their way backwards, having worn away the rocks over
which they fall, and which are shown to be many miles away from the spot
where the river first discharged itself over the cliff.
[Illustration: HYDRAULIC MINING.]
[Illustration: WATER-FALL.]
In fact, it is well known that the Falls are receding at a definite rate
annually, and that the rate has been calculated with scientific
accuracy. The cliffs of our own coasts-say of Margate or
Ramsgate--crumble away with equally calculable speed.
In the hydraulic mining system large tanks are erected, at least two
hundred feet above the level of the mine. From these tanks proceed
pipes, terminated by hose, just like those of our ordinary fire-engines.
The miners, instead of using pickaxe or crowbar, simply direct the
streams of water against the solid rock. Their effect is tremendous.
They tear it to powder, and carry it down the wooden troughs called
“flumes,” in which the mercury is so arranged that not a single atom of
quartz rock can pass without having its gold extracted.
The following graphic account of Hydraulic Mining at Nevada is taken
from Mr. J. K. Lord’s “Naturalist in British Columbia:”--
“Near Nevada are the famed Hydraulic washings. The gold is disseminated
through terraces of shingle conglomerates, often three hundred feet in
thickness. These terraces are actually washed entirely off the face of
the country by propelling jets of water against them, forced by pressure
through a nozzle.
“To accomplish this, the water is brought in canals, tunnels, and wooden
aqueducts, often forty miles away from the ‘draft.’ This supply of water
the miners rent.
“As we near the washing spot, in every direction immense hose, made of
galvanized iron, and canvas tubes six feet round, coil in all directions
over the ground like gigantic serpents, converging towards a gap, where
they disappear.
“On reaching this gap, I look down into a basin or dry lake, three
hundred feet below me. The hose hangs down this cliff of shingle, and
following its course by a zigzag path, I reach a plateau of rock, from
which the shingle has already been washed.
“A man stands at the end of each hose, that has for its head a brass
nozzle. With the force of cannon-shot, water issues in a large jet from
this tube, and propelled against the shingle, guided by the men, washes
it away as easily as we could sweep a molehill from off the grass.
“The stream of water, bearing with it the materials washed from out the
cliff, runs through wooden troughs called ‘flumes,’ floored with
granite. These ‘flumes’ extend six miles. Men are stationed at regular
distances to fork out the heavy stones.
“Throughout its entire length, transverse strips of wood dam back a tiny
pond of mercury. These are called _ruffles_--gold-traps, in other words,
that seize on the fine dust-gold distributed through the shingle. The
flumes are cleaned about once a month, and the gold extracted from the
mercury.
“I try with a powerful lens to detect gold amidst the material they are
washing, but not a trace is discoverable, and yet it pays an immense
profit to the gold-washers.”
* * * * *
THERE are two more modes of extracting water, which will be but
cursorily mentioned.
The reader will remember that water finds its own level, and that the
terrific power of hydraulic mining is owing to the fact that the water
expends its force against the solid rock instead of ascending into the
air.
[Illustration: ARTESIAN WELL.]
[Illustration: NORTON’S TUBE.]
It is now found that, even without artificial assistance, water has a
habit of finding its own level, and that, if it be allowed its own
course, it will contrive to find its way nearly to the highest point
whence it derived its origin. On this principle are based the Artesian
Wells, which, when they “strike water,” spurt it up in a torrent, as is
the case with the now celebrated Norton Tubes, which are screwed down
into the earth like hollow gimlets, and which always contrive to extract
the water hidden beneath the surface of the earth.
The success of our army in Abyssinia was greatly owing to these Norton
Tubes, which, being of small diameter and of peculiar make, could be
screwed into the ground when the troops made a halt, unscrewed when they
left the spot, and used again for the next halt.
Similarly, the French used the Artesian-well system with wonderful
success in Northern Africa. Water is the chief necessity of life in that
part of the world, and a nation who could cause pure cold water to
spring out of the hot and thirsty sands was naturally looked upon as
something more than human.
Yet the principle was exactly the same in both cases. Water is always
latent somewhere beneath the surface of the earth, and, if a tube can be
driven deep enough, the water will come up it.
The accompanying illustration shows the Artesian Well and Norton’s Tube,
and their similitude in principle, the tube penetrating through various
layers of soil, until it reaches the water which it seeks.
* * * * *
THEN there is another way by which water can be made to force itself to
a considerable height. Not being much of a mathematician, I do not
recollect the exact proportional height to which a stream of water may
raise itself, but if any one can secure a fall of some eight or ten
feet, he can furnish his house with water by means of the “Ram,” a chart
of which is shown in the illustration.
[Illustration: SPOUT-HOLE.]
[Illustration: WATER-RAM.]
The principle of the Ram is, that the water is allowed to flow down a
tube, when it meets with a valve. This valve is suddenly closed by the
pressure, and the water is forced onwards by the shock. Much water
escapes at each blow of the valve, but that does not signify.
The force of water thus suddenly stopped is hardly appreciated. Even in
ordinary houses the sudden turning of a water-tap has been known to
burst the pipe and deluge the house with water.
* * * * *
IN Nature a similar effect is produced, called popularly the
“Spout-hole.”
It is a hole or tunnel on the seashore, passing upwards from the level
of the sea to the summit of the cliff.
When the waves are urged against the tunnel by the wind, the water is
dashed into it. Being partially checked by the friction, which acts
exactly like the water that is checked by the Ram, the wave hurls itself
up the channel, and flies out in showers of spray, high above the level
of the original wave which caused it.
In the illustration are shown the Water-ram with its globular valve, and
the safety or escape valve of the waste water. On the left is shown one
of the natural Spout-holes, with the water dashing through its tunnel
into a mass of spray.
USEFUL ARTS