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 encyclopÆdias 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° 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° F., while in an open pan or grainer it requires 226° 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.