and uses as paraffin and naphtha. Some of them are used for oiling
machinery; tar is used for dyes; naphtha dissolves resin to use in
varnish; benzine is the great cleanser of clothes, printers' types,
and almost everything else; gasoline runs automobiles, motors, and
many sorts of engines; paraffin makes candles, seals jelly glasses,
covers the heads of matches so that they are no longer spoiled by
being wet, and makes the ever-useful "waxed paper"; printers' ink and
waterproof roofing-paper both owe a debt to petroleum. Even in
medicine, though a little petroleum is no longer looked upon as a
cure-all, vaseline, one of its products, is of great value. It can be
mixed with drugs without changing their character, and it does not
become rancid. For these reasons, salves and other ointments can be
mixed with it and preserved for years.
XI
LITTLE GRAINS OF SALT
The most interesting mine in the world is that of Wieliczka in Poland.
In it there are some thirty miles of streets and alleys; there are
churches with pillars, shrines, and statues; there are stairs,
monuments, and restaurants; there is a ballroom three hundred feet
long and one hundred and ninety feet high, with beautiful chandeliers,
and in it is a carven throne whereon the Emperor Franz Joseph sat when
he visited the mine. There are lakes crossed by ferryboats. There is a
railroad station for the mule trains which bear the precious mineral
salt, for this is a salt mine, and shrines, statues, churches,
chandeliers--everything--are all cut out of salt.
This mine has been worked for at least eight hundred years and still
has salt enough to supply all Europe for ages. The mass of salt is
believed to be five hundred miles long, fifty miles wide, and nearly a
quarter of a mile thick. It is so pure that it is sold just as it
comes from the mine, either in blocks or finely ground. This mine is a
wonderful place to visit, almost like an enchanted palace, for as the
torchlight strikes the crystals of salt, they flash and sparkle as if
the wall was covered with rubies and diamonds.
There is nothing like an enchanted palace in any salt mine of the
United States, no statues or chapels or chandeliers. There is only a
hole in the ground, where mining is carried on in much the same manner
as in other kinds of mines. The shaft is sunk and lined with timbers
to keep the dirt from falling in, just as in other mines. In working
salt mines, however, water is almost as bad as earth, and therefore a
layer of clay is put between the timbers and the earth. There are the
usual galleries and pillars, with roof and floor of salt. The workmen
try to get the salt out in lumps or blocks as far as possible, and so
they bore in drill holes and then blast with dynamite or powder. The
salt is loaded upon little cars, running on tracks, and is carried up
the shaft and to the top of a breaker, usually more than one hundred
feet above the surface of the ground. There it is dumped upon a screen
of iron bars, which lets the fine salt fall through. The large lumps
are sold without crushing or sifting, and are used for cattle and
sheep.
One of the great deposits of salt is in southeastern California. It is
thought that the Gulf of California used to run much farther north
than it now does, and that the earth rose, shutting away part of it
from the ocean. This imprisoned water was full of salt. In time it
dried, and the sand blew over it till it was far underground. A better
way than digging was found to work it, as will be seen later; but
while digging was going on, the workmen built a cottage of blocks of
salt, clear and glassy. The little rain that falls there melted the
blocks only enough to unite them firmly together; and there the house
has stood for many years.
Countries that have no deposits of rock salt can easily get plenty of
salt from the water of the ocean if they only have a seacoast. About
one thirtieth of the ocean water is salt, and if the water is
evaporated, the salt can be collected without difficulty. France makes
a great deal of salt in this way. When a man goes into the
manufacture, or rather, the collecting of salt, he first of all buys
or rents a piece of land,--perhaps several acres of it,--that lies
just above high water, and makes it as level as possible. Unless it is
very firm land, he covers it with clay, so that the water will not
soak through it. Then he divides it into large square basins, making
each a little lower than the one before it. Close beside the highest
basin he makes a reservoir which at high tide receives water from the
ocean. This flows slowly from the reservoir through one basin after
another, becoming more and more salt as the water evaporates. At
length the water is gone, and the salt remains. The workmen take
wooden scrapers and push the salt toward the walls of the basins and
then shovel it up on the dikes and heap it into creamy cones that
sparkle in the sunshine. The dikes are narrow, raised pathways beside
the basins and between them. As you walk along on top of them, you can
smell a faint violet perfume from the salt. Thatch is put over the
cones to protect them from the rain, and there they stand till some of
the impurities drain away. This salt is not perfectly white, because
the workmen cannot help scraping up a little of the gray or reddish
clay with it. Most of it is sold as it is, nevertheless, for many
people have an absurd notion that the darker it is the purer it is.
For those who wish to buy white salt it is sent to a refinery to be
washed with pure water, then boiled down and dried.
So it is that the sun helps to manufacture salt. In some of the colder
countries, frost does the same work, but in a very different manner.
When salt water freezes, the _water_ freezes, but the salt does not,
and a piece of salt water ice is almost as pure as that made of fresh
water. Of course, after part of the water in a basin of salt water has
been frozen out, what is left is more salt than it was at first, and
after the freezing has been repeated several times, only a little
water remains, and evaporation will soon carry this away, leaving only
salt in the basin, waiting to be purified.
Not very many years ago one of the encyclopaedias remarked that "the
deposits of salt in the United States are unimportant." This was true
as far as the working of them was concerned, but in 1913 the United
States produced more than 34,000,000 barrels. Part of this was made by
evaporation of the waters of salt springs, and a small share from
Great Salt Lake in Utah. The early settlers in Utah used to gather
salt from the shallow bays or lagoons where the water evaporated
during the summer; but now dams of earth hold back the water in a
reservoir. In the spring the pumps are put to work and the reservoir
is soon filled with water. This is left to stand and give the
impurities a chance to settle to the bottom. Then it is allowed to
flow into smaller basins, while more water is pumped into the
reservoir. When autumn comes, the crop of salt is ready to be
harvested. It is in the form of a crust three to six inches thick,
some of it in large crystals, and some fine-grained. This crust is
broken by ploughs, and the salt is heaped up into great cones and left
for the rain to wash clean. Then it goes to the mill for purifying.
The water of Great Salt Lake is much more salty than that of the
ocean. It preserves timber remarkably well, and often salt from the
lake is put around telephone poles, seventy-five pounds being dropped
into the hole for each one. It has been suggested to soak timber in
the Lake, and then paint it with creosote to keep the wet out and the
salt in.
Salt is also made from the waters of salt springs, which the Indians
thought were the homes of evil spirits. At Salton, in California, an
area of more than one thousand acres, which lies two hundred and
sixty-four feet below sea level, is flooded with water from salt
springs. When this water has evaporated, all these acres are covered
with salt ten to twenty inches thick, and as dazzlingly white as if it
was snow. This great field is ploughed up with a massive four-wheeled
implement called a "salt-plough." It is run by steam and needs two men
to manage it. The heavy steel ploughshare breaks up the salt crust,
making broad, shallow furrows and throwing the salt in ridges on both
sides. The plough has hardly moved on before the crust begins to form
again. This broken crust is worked in water by men with hoes in order
to remove the bits of earth that stick to it, then piled up into cones
to drain, loaded upon flat trucks, and carried to the breaker. The
salt fields are wonderfully beautiful in the moonlight, but not very
agreeable to work in, for the mercury often reaches 140 deg. F., and the
air is so full of particles of salt that the workers feel an intense
thirst, which the warm, brackish water does not satisfy. The work is
done by Indians and Japanese, for white people cannot endure the heat.
A large portion of the salt used in the United States comes directly
from rock salt strata, hundreds of feet below the surface of the
ground. These were perhaps the bed of the ocean ages and ages ago.
There is a great extent of the beds in New York, Michigan, Ohio,
Kansas, and other States. In Michigan there is a stratum of rock salt
thirty to two hundred and fifty feet thick and some fifteen hundred to
two thousand feet below the surface. To mine this would be a difficult
and expensive undertaking, and a far better way has been discovered.
First, a pipe is forced down through the surface dirt, the limestone,
and the shale to the salt stratum. The drill works inside this pipe
and bores a hole for a six-inch pipe directly into the salt. A
three-inch pipe is let down inside of the six-inch pipe, and water is
forced down through the smaller pipe. It dissolves the salt, becomes
brine, and rises through the space between the two pipes. It is
carried through troughs to some great tanks, and from these it flows
into "grain-settlers," then into the "grainers" proper, where the
grains of salt settle. At the bottom of the grainers are steam pipes,
and these make the brine so hot that before long little crystals of
salt are seen floating on the surface of the water. Crystals form much
better if the water is perfectly smooth, and to bring this about a
very little oil is poured into the grainer. It spreads over the
surface in the thinnest film that can be imagined. The water
evaporates, and the tiny crystals grow, one joining to another as they
do in rock candy. When they become larger, they drop to the bottom of
the grainer. They are now swept along in a trough to a "pocket,"
carried up by an endless chain of buckets, and then wheeled away to
the packinghouse.
The finest salt is made by using vacuum pans. These are great cans out
of which the air is pumped, and into which the brine flows. This
brine, heated by steam pipes, begins to boil, and as the steam from it
rises, it has to pass through a pipe at the top and is thus carried
into a small tank into which cold water is flowing. The cold makes the
steam condense into water, which runs off. The condensed water
occupies less space than the steam and so maintains the vacuum in the
pan. For a perfect vacuum the brine is boiled at less than 100 deg. F.,
while in an open pan or grainer it requires 226 deg. to boil brine. The
brine is soon so rich in salt that tiny crystals begin to form. These
are taken out and dried. If you look at some grains of table salt
through a magnifying glass, you can see that each grain is a tiny
cubical crystal. Sometimes two or three are united, and often the
corners are rounded off and worn, but they show plainly that they are
little cubes.
Most of the salt used on our tables is made by the vacuum process or
by an improved method which produces tiny flakes of salt similar to
snowflakes. The salt brine is heated to a high temperature and
filtered. In the filters the impurities are taken out, and this
process gives us very pure salt. The tiny flakes dissolve more easily
than the cubes of salt, and thus flavor food more readily.
With a few savage tribes salt is regarded as a great luxury, but with
most peoples it is looked upon as a necessity. Some of the early races
thought a salt spring was a special gift of the gods, and in their
sacrifices they always used salt. In later times to sit "above the
salt," between the great ornamental salt cellar and the master of the
house, was a mark of honor. Less distinguished guests were seated
"below the salt." To "eat a man's salt" and then be unfaithful to him
has always been looked upon as a shameful act; and with some of the
savages, so long as a stranger "ate his salt,"--that is, was a guest
in the house of any one of them,--he was safe. To "eat salt together"
is an expression of friendliness. Cakes of salt have been used as
money in various parts of Africa and Asia. "Attic salt" means wit,
because the Athenians, who lived in Attica, were famous for their
keen, delicate wit. To take a story or a statement "with a grain of
salt" means not to accept it entirely, but only to believe it
partially. When Christ told his disciples that they were "the salt of
the earth," he meant that their lives and teaching would influence
others just as salt affects every article of food and changes its
flavor. Our word "salary" comes from the Latin word _sal_, meaning
salt; and _salarium_, or "salt-money," was money given for paying
one's expenses on a journey. Living without salt would be a difficult
matter. Cattle that have been shut away from it for a while are almost
wild to get it. Farmers living among the mountains sometimes drive
their cattle to a mountain pasture to remain there through the summer,
and every little while they go up to salt the animals. The cattle know
the call and know that it means salt; and I have seen them come
rushing down the mountain-side and through the woods, over fallen
trees, through briers, and down slippery rocks, bellowing as they
came, and plunging head first in a wild frenzy to get to the pieces of
rock salt that were waiting for them.
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Transcriber's Notes
The List of Illustrations was added, and some of the illustrations
have been moved from their original positions to avoid breaking up
paragraphs of text.
End of Project Gutenberg's Diggers in the Earth, by Eva March Tappan