OUR DRINK
FILLING THE BOILER OF THE BODY-ENGINE
The Need of Water in the Body-Engine. If you have ever taken a long
railway journey, you will remember that, about every two or three hours,
you would stop longer than usual at some station, or switch, for the
engine to take in water. No matter how briskly the fire burns in the
furnace, or how much good coal you may shovel into it, if there be no
water in the boiler above it to expand and make steam, the engine will
do no work. And an abundant supply of water is just as necessary in our
own bodies, although not used in just the same way as in the engine.
The singular thing about water, both in a locomotive and in our own
bodies is that, absolutely necessary as it is, it is neither burned up
nor broken down in any way, in making the machine go; so that it gives
off no energy, as our food does, but simply changes its form slightly.
Exactly the same amount of water, to the ounce, or even the teaspoonful,
that is poured into the boiler of an engine, is given off through its
funnel and escape-pipes in the form of steam; and precisely the same
amount of water which we pour into our stomachs will reappear on the
surface of the body again in the form of the vapor from the lungs, the
perspiration from the skin, and the water from the kidneys. It goes
completely through the engine, or the body, enables the one to work and
the other to live, and yet comes out unchanged.
Just how water works in the engine we know--the heat from the furnace
changes it into steam, which means that heat expands it, or makes it
fill more space. This swelling pushes forward the cylinder that starts
the wheels of the engine. The next puff gives them another whirl, and in
a few minutes the big locomotive is puffing steadily down the track.
Water is Necessary to Life. Just how water works in the body we do not
know, as most of it is not even turned into steam or vapor. But this
much we do know, that life cannot exist in the absence of water. Odd as
it may seem to us at first sight, ninety-five, yes, ninety-nine per cent
of our body cells are water-animals, and can live and grow only when
literally swimming in water.
The scaly cells on the surface of our skin, our hair, and the tips of
our nails are the only parts of us that live in air. In fact, over
five-sixths of the weight and bulk of our bodies is made up of water.
Some one has quaintly, but truthfully, described the human body as
composed of a few pounds of charcoal, a bushel of air, half a peck of
lime, and a couple of handfuls of salt dissolved in four buckets of
water. The reason why nearly all our foods, as we have seen, contain
such large amounts of water is that they, also, are the results of
life--the tissues and products of plants or animals.
Water Frees the Body from Waste Substances. Water in the body, then,
is necessary to life itself. But another most important use is to wash
out all the waste substances from the different organs and tissues and
carry them to the liver, the kidneys, the lungs, and the skin, where
they can be burned up and got rid of. We must keep our bodies well
flushed with water, just as we should keep a free current of water
flowing through our drain-pipes and sewers.
It Keeps the Body from Getting Over-heated. In summer time, or in hot
climates the year round, an abundant supply of water is of great
importance in keeping the body from becoming overheated, by pouring
itself out on the skin in the form of perspiration, and cooling us by
evaporation, as we shall see in the chapter on the skin.
The Meaning of Thirst. None of us who has ever been a mile or more
away from a well, or brook, on a hot summer's day needs to be told how
necessary water is, for comfort as well as for health. The appetite
which we have developed for it--_thirst_, as we call it--is the most
tremendous and powerful craving that we can feel, and the results of
water starvation are as serious and as quick in coming as is the
keenness of our thirst. Men in fairly good condition, if they are at
rest, and not exposed to hardship, and have plenty of water to drink,
can survive without food for from two to four weeks; but if deprived of
water, they will perish in agony in from two to three days.
[Illustration: THE CHAINED CUP
An "Exchange" for disease germs.]
We should Drink Three Pints of Water a Day. Although all our foods,
either as we find them in the state of nature, or as they come on the
table cooked and prepared for eating, contain large quantities of water,
this is not enough for the needs of the body; to keep in good health we
must also drink in some form about three pints, or six glassfuls, of
water in the course of the day. Part of this goes, as you will remember
(p. 16), to dissolve the food so that it can be readily absorbed by our
body cells in the process of digestion.
WHERE OUR DRINKING WATER COMES FROM
Water Contained in our Food is Pure. Seeing that five-sixths of our
food is water, it is clearly of the greatest importance that that water
should be pure. That part of our water supply which we get in and with
our foods is fortunately, for the most part, almost perfectly pure,
having been specially filtered by the plants or animals which originally
drank it, or having been boiled in the process of cooking.
[Illustration: THE SPOUTING FOUNTAIN
Where no lips need touch the cup.]
Water is Always in Motion. The part of our water supply which we take
directly, in the form of drinking water, is, however, unfortunately
anything but free from danger of impurities. The greatest difficulty
with water is that it will not "stay put"--it is continually on the
move. The same perpetual circulation, with change of form, but without
loss of substance, which is taking place in the engine and in our
bodies, is taking place in the world around us. The water from the
ocean, the lakes, and the rivers is continually evaporating under the
heat of the sun and rising in the form of vapor, or invisible steam,
into the air. There it becomes cooler, and forms the clouds; and when
these are cooled a little more, the vapor changes into drops of water
and pours down as rain, or, if the droplets freeze, as snow or hail. The
rain falls upon the leaves of the trees and the spears of the grass, or
the thirsty plowed ground, soaks down into the soil and "seeps" or
drains gradually into the streams and rivers, and down these into the
lakes and oceans, to be again pumped up by the sun. All we can do is to
catch what we need of it, "on the run," somewhere in the earthy part of
its circuit.
Why our Drinking Water is Likely to be Impure. Every drop of water
that we drink or use, fell somewhere on the surface of the earth, in the
form of rain or snow; and if we wish to find out whether it is pure and
safe, we must trace its course through the soil, or the streams, from
the point where it fell. Our drinking water has literally washed "all
outdoors" before it reaches us, and what it may have picked up in that
washing makes the possibilities of its danger.
As it falls from the skies, it is perfectly pure--except in large cities
or manufacturing centres, where rain water contains small amounts of
soot, smoke-acids, and dust, but even these are in such small amounts as
to be practically harmless. But the moment it reaches the ground, it
begins to soak up something out of everything that it touches; and here
our dangers begin.
Risks from Leaf Mould. Practically the whole surface of the earth is
covered with some form of vegetation--grass, trees, or other green
plants. These dying down and decaying year after year, form a layer of
vegetable mould such as you can readily scratch up on the surface of the
ground in a forest or old meadow; this is known as leaf mould, or
_humus_. As the water soaks through this mould, it becomes loaded with
decaying vegetable matter, which it carries with it down into the soil.
Most of this, fortunately, is comparatively harmless to the human
digestion. But some of this vegetable matter, such as we find in the
water from bogs or swamps, or even heavy forests, will sometimes upset
the digestion; hence, the natural dislike that we have for water with a
marshy, or "weedy," taste.
[Illustration: NATURE'S FILTER-BED
The spring water is pure; the brook may gather infection as it goes.]
Nature's Filter-Bed. When, however, this peaty water soaks on down
through the grass, roots, and leaf mold, into the soil, it comes in
contact with Nature's great filter-bed--the second place in the circuit
where the water is again made perfectly pure. This filter-bed consists
of a layer of more or less spongy, porous soil, or earth, swarming with
millions of tiny vegetable germs known as bacteria. These eagerly pick
out all the decaying vegetable substances of the water and feed upon
them, changing them into harmless carbon dioxid water, and small amounts
of _ammonia_. Not only will this filter-bed, or spongy mat of bacteria,
burn up and remove all traces of vegetable decay, but if the rain
happens to have soaked through the decaying body of a bird or animal or
insect, the bacteria will just as eagerly feed upon these animal
substances and change them into harmless gases and salts.[13]
By the time the rain water has reached the deeper layers of the soil,
it is again perfectly pure and has also, in seeping through the soil,
picked up certain mineral salts (such as _calcium_, _sodium_, and
_magnesium_) which are of use in the body; so that in an open or thinly
settled country, the water in streams, rivers, and lakes is usually
fairly pure and quite wholesome. That is why, in ancient times, the
great majority of villages and towns and camps were situated on the bank
of some stream, where a supply of water could easily be obtained.
CAUSES AND DANGERS OF POLLUTED WATER
Wells--the Oldest Method of Supplying Water. It was long ago
discovered that, by digging pits or holes in the ground, the rain water,
in its steady flow toward the streams and lakes, could be caught or
trapped, and that if the pit were made deep enough, a sufficient amount
would accumulate during the winter or spring to last well on into the
summer, unless the season were unusually dry. These pits, or water
traps, are our familiar _wells_, from which most of our water supply,
except in the large cities, is still taken. These wells were naturally
dug, or sunk, as near as might be to the house, so as to shorten the
distance that the water had to be carried; and from this arose their
chief and greatest source of danger.
The Danger to Wells from Household Waste. Every house has, like our
bodies, a certain amount of waste, which must be got rid of. Some of
this material can, of course, be fed to pigs and chickens, and in that
way disposed of. But the simplest and easiest thing to do with the
watery parts of the household waste is to take them to the back door and
throw them out on the ground, while table-scraps and other garbage are
thrown into the long grass, or bushes--a method which is still,
unfortunately, pursued in a great many houses in the country and the
suburbs of towns. If the area over which they are thrown is large
enough, and particularly if the soil is porous and well covered with
vegetation, nature's filter-bed--the soil, the bacteria, and the roots
of the grass and other plants combined--will purify a surprising amount
of waste; but there is always the danger, particularly in the wet
weather of spring and of late fall, that the soil will become charged
with more of these waste matters than the bacteria can destroy, and that
these waste poisons will be washed down in the rain water right into the
pit, or trap, which has been dug for it--the well.
[Illustration: AN EXAMPLE OF GOOD FARM DRAINAGE
Here the farmhouse is set above the barn, pens, and cattle yard, and at
some distance from them. The drainage from these is into the lower
fields, so that a well driven into the high ground not far from the
house is presumably safe.]
The Danger from Outbuildings. This danger is further increased by the
fact that for the same reason--the vital need of plenty of water for all
living creatures--the hen coop, the pig pen, the cow stable, and the
horse barn are all likely to be built clustering around this same well.
If the fertilizer from these places is, as it should be in all
intelligent farming, protected from the rain so as not to have all its
strength washed out of it, and removed and spread on the soil at
frequent intervals, the well may even yet escape contamination; but the
chances are very strongly against it. If you will figure out that a well
drains the surface soil in every direction for a distance from ten to
thirty times its own depth, and that the average well is about
twenty-five feet deep, you can readily see what a risk of contaminating
the well is caused by every barn, outhouse, or pen within from sixty to
a hundred and fifty yards from its mouth.
Every well from which drinking water is taken should be at least fifty,
and better, a hundred and fifty, yards away from any stable, outhouse,
or barn; or set well up-hill from it, so that all drainage runs away
from its basin. This, of course, is possible only in the country, or in
villages or small towns, where houses have plenty of ground about them.
Consequently, the health laws of most cities and states forbid the use
of shallow wells for drinking purposes in cities of over 10,000
population.
Causes which Produce Pure Well Water. Occasionally a well will be
driven through a layer of rock or hard water-proof clay, before the
water-bearing layer of soil, or sand, is struck, so that its water will
be drawn, not from the rain that falls on the surface of the ground
immediately about it, but from that which has fallen somewhere at a
considerable distance and filtered down through the soil. This water, on
account of the many, many layers of soil through which it has filtered,
and the long distance it has come, is usually fairly pure, so far as
animal or vegetable impurities are concerned, though it is apt to have
become too strong in certain salty and mineral substances, which give it
a taste of salt, or iron, or sulphur. If, however, it is free from these
salty substances, it makes a very pure and wholesome drinking water; and
if the upper part of the well shaft be lined with bricks and cement, so
that the surface water cannot leak into it, it may be used with safety
for drinking purposes even in the heart of a city.
[Illustration: THE DANGER SPOT ON THE FARM
The milk inspector on visiting this dairy farm found that the well was
receiving the drainage of both house and privy. The well water was used
for drinking and for washing the milk pails (seen behind the fence).]
The Greatest Single Danger to Well Water. The greatest single danger
to the purity of well water is the privy vault. This is doubly
dangerous, first, because it is dug below the level at which the
bacteria in the soil are most abundant and active, so that they cannot
attack and break up its contents; and the impurities, therefore, are
gradually washed down by the rain water into the soil, unchanged, and
seep directly into the well. The other reason is that its contents may
contain the germs of serious diseases, particularly typhoid fever and
other bowel troubles. These germs and their poisons would usually be
destroyed by the bacteria of the soil, if not poured out in too large
quantities; but in the privy vault they escape their attack, and so are
carried on with the slow leakage of water into the well; then those who
use that water are very liable to have typhoid fever and other serious
diseases.
Early Methods of Prevention. On account of these filth-dangers, it
began, a century or so ago, to be the custom in cleanly and thoughtful
households to provide, first, ditches, and then, lines of pipes, made
out of hollow wood or baked clay, and later of iron, called drains,
through which all the watery parts of household wastes could be carried
away and poured out at some distance from the house. Then toilets, or
flush-closets, were built, and this kind of waste was carried completely
away from the house, and beyond danger of contaminating the wells.
How Streams were Contaminated. For a time this seemed to end the
danger, as the waste was soaked up by the soil, and eaten by its hungry
bacteria and drunk up again by the roots of plants. But when ten or a
dozen houses began to combine and run their drain-pipes together into a
large drain called a sewer, then this could not open upon the surface of
the ground, but had to be run into some stream, or brook, in order to be
carried away. As cities and towns, which had been obliged to give up
their wells, were beginning to collect the water from these same brooks
and streams in reservoirs and deliver it in pipes to all their houses,
it can be easily seen that we had simply exchanged one danger for
another.
The Loss of Life from Typhoid Fever. For a time, indeed, it looked as
if the new danger were the greater of the two, because, when the typhoid
germs were washed into a well, they poisoned or infected only one, or at
most two or three, families who used the water from that well. But when
they were carried into a stream which was dammed to form a reservoir to
supply a town with water, then the whole population of the town might
become infected. A great many epidemics of typhoid fever occurred in
just this way, before people realized how great this danger was. Simply
from the pouring of the wastes from one or two typhoid fever cases into
the streams leading into the water reservoir used by a town, five
hundred, a thousand, or even three or four thousand cases of typhoid
have developed within a few weeks, with from one hundred to five hundred
deaths.
[Illustration: TYPHOID EPIDEMIC IN THE MOHAWK-HUDSON VALLEY, 1891-92
In 1891-92 typhoid fever broke out in Schenectady on the Mohawk River.
Following this, Cohoes and West Troy, which drew their water supply from
the Mohawk below Schenectady, and Albany, which drew its supply from the
Hudson below the mouth of the Mohawk, suffered from typhoid epidemics;
while Waterford and Troy, which drew their supplies from the Hudson
_above_ the mouth of the Mohawk, and the river towns that, like
Lansingburgh, drew from other sources, entirely escaped the infection.]
In fact, even to-day, when these dangers are better understood, and
while most of our big cities are getting fairly clear of typhoid, so
ignorant and careless are the smaller towns, villages, and private
houses all over the United States, that over 35,000 deaths[14] from
typhoid fever occur every year in a country which prides itself upon its
cleanliness and its intelligence. This means, too, that there are at
least half a million people sick of the disease, and in bed or utterly
prevented from working, for from five to fifteen weeks each. All of
which frightful loss of human life and human labor, to say nothing of
the grief, bereavement, and anxiety of the two million or more families
and relatives of these typhoid victims, is due to eating dirt and
drinking filth. Dirt is surely the most expensive thing there is,
instead of the cheapest.
METHODS OF OBTAINING PURE WATER
Wise Planning and Spending of Money is Necessary. If our city wells
are defiled by manure heaps and vault-privies, and our streams by
sewage, where are we to turn for pure water? All that is required is
foresight and a little intelligent planning and wise spending of money.
Of course the community must take hold of the problem, through a Board
of Health, or Health Officer, appointed for the purpose; and this is why
questions of health are coming to play such an important part in
legislation, and even in politics. No matter how fast a city is growing
or how much money its inhabitants are making, if it has an impure water
supply or a bad sewage system, there will be disease and death,
suffering and unhappiness among its people, which no amount of money can
make up for. Cleanliness is not only next to godliness, but one of the
most useful forms of it; and a city can afford to spend money liberally
to secure it--in fact, it is the best investment a city can make.
Artesian and Deep Wells. The earliest, and still the most eagerly
sought-for, source of pure water supply is springs or deep wells, such
as we have referred to. Both of these are fed by rain water which has
fallen somewhere upon the surface of the earth. As the layers of earth
or rock, of which the crust of the earth is made up, do not run level,
or horizontal, but are tilted and tipped in all directions, this rain
water soaks down until it reaches one of these sloping layers that is so
hard, or tough, as to be waterproof, and then runs along over its
surface in a sort of underground stream. If anywhere in the course of
this stream a very deep well shaft is driven right down through the soil
until it strikes the surface of this sloping layer of rock, then the
water will rise in this shaft to the level of the highest point from
which it is running.
[Illustration: ARTESIAN WELL BORINGS
The sketch shows a wide section from northern Illinois to central
Wisconsin, in which the cities have rejected the water supplies afforded
by the rivers, choosing instead to bore down almost to hard rock to
insure the purity of the supply.]
If this highest point of the waterproof layer be many miles away, up in
the hills above the surface of the ground where the well is dug, then
the water will rise to the surface and sometimes even spout twenty,
thirty, or fifty feet above it. This forms what is known as a _gushing_,
or _artesian_, well (from Artois, a province in France, in which such
wells were first commonly used) and furnishes a very pure and valuable
source of water supply. If it rises only twenty, thirty, or fifty feet
in the well-shaft, but keeps flowing in at a sufficient rate, then we
get what is known as a "living," or _permanent_ well, and this also is a
very valuable and pure source of water supply.
Springs. Springs are formed on the same plan as the deep well, but
with the difference that the waterproof layer on top of which the water
is running either crops out on the surface again, lower down the
mountain, or folds upon itself and comes up again to the surface some
distance away from the mountain chain, out on the level. This is why
springs are usually found in or near mountainous or hilly regions. If
the water of a spring has gone deep enough into, or far enough through,
the layers of the earth, it may, like water of some of the artesian
wells, contain certain salts and minerals, particularly soda, sulphur,
and iron. Such springs are often highly valued as mineral water, healing
springs, or baths, partly because of these salts, partly on account of
their peculiar taste. Most of the virtues ascribed to mineral waters or
springs are due, however, to their _pure water_, and its cleansing
effects internally and externally when freely used.
Springs are among the most highly prized sources of water supply,
because they have gone underground sufficiently deep to become well
filtered and cooled to a low temperature, and usually not far enough to
become too heavily loaded with salts or minerals like the waters of the
deep wells. It must, however, be remembered that they also come from
rain-water, and that in hilly or broken regions the source of that rain
water may be the surface of the ground only a few hundred yards up the
hill or mountain, and impurities there may affect it. Much of the
delightful sparkle of spring water is due, as in the case of the popular
soda water, to the presence of carbon dioxid, only in spring water it is
produced by the decomposition of vegetable matter in it. As springs
usually break out in a hollow or at the foot of a hill, unless
carefully closed in they are quite liable to contamination from rain
water from the surrounding surface of the ground. Where springs of a
sufficient size can be reached, or a sufficiently "live" series of deep
wells can be bored, these furnish a safe source of water supply for
cities. But of course not more than one city in five or ten is so
favored.
Mountain Reservoirs. Two other methods of securing a water supply are
now generally adopted. One is to pick out some stream up in the hills or
mountains, within fifteen miles or so of the city, and put in a dam,
thus making a reservoir, or to enlarge some lake which already exists
there. At the same time, the entire valley, or slope of the mountain,
which this stream or lake drains of its surface water, is bought up by
the Government, or turned into a forest reserve, so that no houses can
be built or settlement of any kind permitted upon it. It can still be
used for lumber supply, for pastures, and, within reasonable limits, for
a great public hunting and fishing reserve and camping resort.
[Illustration: A CITY WATER SUPPLY BROUGHT FROM THE FAR HILLS]
Almost every intelligent and farsighted town, which has not springs or
deep wells, is looking toward the acquirement of some such area as this
for its source of pure water. Many great cities go from thirty to fifty
miles, and some even a hundred and fifty miles, in order to reach such a
source, carrying the water into the city in a huge water-pipe, or
_aqueduct_. These cities find that the millions of dollars saved by the
prevention of death and disease amount to many times the cost of such a
system, while the water rents gladly paid by both private houses and
manufacturing establishments give good interest on the investment. Any
town can afford to go a mile for every thousand of its population for
such a source of water supply as this; and secure, _gratis_, a valuable
forest preserve, public park, and beauty spot.[15]
Filtration. The other method, which has to be adopted by cities
situated on level plains, or at the mouths of great rivers, is to take
the water of some lake, or river, as far out in the former, or as high
up the latter, as possible, and purify it by filtration. This can be
done at a moderate expense by preparing great settling-basins and
filter-beds. The first are great pools or small lakes, into which the
water is run and held until most of the mud and coarser dirt has settled
or sunk. Then this clear water above the sediment is run on to great
beds, first of gravel, then of coarse sand, then of fine sand; and if
these beds are large enough, and frequently changed and cleaned, so that
they do not become clogged, and the process is carried out slowly, the
water, when it comes through the last bed, is pure enough to drink
safely.[16]
[Illustration: A RESERVOIR AND COSTLY DAM]
One of these sources of a safe and wholesome water-supply--the deep
flowing well, or spring; the water shut up in the mountains in its lake
or reservoir; or the slow filter-bed--should be used by every
intelligent and progressive town of more than a thousand inhabitants.
Sewage and its Disposal. At the same time, while seeking a source of
water-supply far removed from any possibility of contagion, we must not
neglect the other end of the problem, the protecting of our rivers and
lakes from pollution so far as possible; for the water from these must
necessarily be used by thousands of people along their banks, either
directly, or in the form of shallow wells, sunk not far from the water's
edge. Moreover, so foul are many of our rivers and streams becoming in
thickly settled regions that fish can no longer live in them, and it is
hardly safe to bathe in them.[17] Fortunately, however, a great deal of
the worst contamination can be prevented by using modern methods of
disposing of sewage, such as filter-beds and sewage farms. All of these
methods use the bacteria of the soil, or crops growing in it, to eat up
the waste and thus purify the sewage.
[Illustration: SCRAPING THE SEDIMENT FROM THE BOTTOM OF A RESERVOIR]
HOME METHODS OF PURIFYING WATER
Boiling. Where the water that you are obliged to drink is not known to
be pure, then it can be made quite safe for drinking purposes by the
simple process of boiling it for about ten or fifteen minutes. But this,
except in travelling or in emergencies, is a lazy, slipshod substitute
for pure water, and extremely unsatisfactory as well; for the boiling
drives off all its air and other gases, and throws down most of the
salts, so that boiled water has a flat, insipid taste. These salts,
although sometimes regarded as impurities, are not such in any true
sense; for the lime and soda especially are of considerable value in the
body, so that boiled or sterilized water is neither a pleasant nor a
wholesome permanent drink. Instead of boiling the water, get to work to
protect your own well from filth of all sorts, if you drink well water;
or, if not, to help the Board of Health to agitate, and keep on
agitating, until something is done to compel your selectmen or City
Council to secure a pure supply.
[Illustration: THE DOMESTIC FILTER IN USE
Unless the sand and charcoal in the glass bulb is very frequently
cleaned, it serves merely as a "catch-all" for impurities, through which
the water must flow.]
Domestic Filters. Much the same must be said of _private_ or _domestic
filters_. These are, at best, temporary substitutes, and should not be
depended upon for permanent use. Many of them are made to sell rather
than to purify, and will remove only the larger or mechanical impurities
from the water. Others, while they work well at first, are exceedingly
likely to become clogged, when the tendency is to punch at them to make
them work faster, thus either poking a hole through them or cracking the
filter-shell, so that a stream of water flows steadily through, just as
impure as when it entered. Private filters, like boiling water, are only
temporary ways of meeting conditions _which ought not to be allowed to
exist at all_ in civilized communities, or in your own homes.
A score of court decisions in all parts of the world have now held that
the water company is legally responsible for all avoidable pollution of
public water-supplies, and nine tenths of pollutions _are_ avoidable.
FOOTNOTES:
[13] These gases and salts are eagerly sucked up by the roots of plants,
so that the soil bacteria are our best friends, changing poisonous
decaying things into harmless plant-foods. They are the chief secret of
the fertility of a soil; and the more there are of them the richer a
soil is.
[14] This makes fourteen times as many deaths from typhoid in proportion
to the population as occur in Germany.
[15] New York City, for instance, goes forty miles up into the hills to
the great Croton reservoir for its water supply; and as this is proving
insufficient, is preparing to go ninety-five miles up into the Ramapo
Hills to secure control of a whole country-side for a permanent source
of supply. Portland, Oregon, nearly twenty years ago, with then a
population of some 75,000, built an aqueduct sixty miles up into the
mountains to a lake on the side of Mt. Hood, and has reaped the
advantages of its foresight ever since, in a low death rate and a rapid
growth (200,000 in 1910), as well as a financial profit on its
investment. Los Angeles, California, is preparing to build an aqueduct a
hundred and thirty miles, and tunnel two mountain ranges in order to
reach an inexhaustible supply of water.
[16] Of late, currents of electricity are passed through the water
(setting free _oxygen_ or _ozone_) which make the purifying of it much
more rapid and complete.
It is, however, often considered safer to pass the water through still
another filter bed, consisting of layers of charcoal, which has the
power of gathering oxygen in its pores, to attack and _oxidize_, or burn
up, the remaining impurities in the water. A sort of scum forms over the
surface of the last and finest bed of sand or charcoal, and if this scum
is not too frequently removed, though it makes the filtering slower, the
water comes out purer. On examining this scum, we find it to consist of
a thick mat of our old friends, the purifying bacteria of the soil. So
that the last step of our artificial filtration is simply an imitation
of nature's great filter-bed.
[17] Several streams emptying into the Ohio River from a thickly settled
region are said to be actually pumped out into waterworks systems, used
for drinking, washing, and manufacturing, and run back into the river
again through sewers by the different cities along its banks, at such
frequent intervals that every drop of water in them passes through
waterworks systems and sewers _three times_ before it reaches the mouth
of the stream.