A famous Latin poet named Horace, who lived two thousand years ago, wrote of his poems, "I have reared a monument more lasting than bronze"; and he was right, for few statues have endured from his day to ours, but his poems are still read and admired.

Bells are made of bronze, about three quarters copper and one quarter tin. It is thought that much copper gives a deep, full tone, and that much tin with, sometimes, zinc makes the tone sharp. The age of a bell has something to do with its sound being rich and mellow; but the bellmaker has even more, for he must understand not only how to cast it, but also how to tune it. If you tap a large bell, it will, if properly tuned, sound a clear note. Tap it just on the curve of the top, and it will give a note exactly one octave above the first. If the note of the bell is too low, it can be made higher by cutting away a little from the inner rim. If it is too high, it can be made lower by filing on the inside a little above the rim. Many of the old bells contain the gifts of silver and gold which were thrown in by people who watched their founding. The most famous bell in the United States is the "Liberty Bell" of Independence Hall, in Philadelphia, which rang when Independence was adopted by Congress. This was founded in England long before the Revolution and later was melted and founded again in the United States.

It would not be easy to get on without brass and bronze; but even these alloys are not so necessary as copper by itself. It is so strong that it is used in boiler tubes of locomotives, as roofing for buildings and railroad coaches, in the great pans and vats of the sugar factories and refineries. A copper ore called "malachite," which shows many shades of green, beautifully blended and mingled, is used for the tops of tables. Wooden ships are often "copper-bottomed"; that is, sheets of copper are nailed to that part of the hull which is under water in order to prevent barnacles from making their homes on it, and so lessening the speed of the vessel.

People often say that the latter half of the nineteenth century was the Age of Steel, because so many new uses for steel were found at that time. The twentieth century promises to be the Age of Electricity, and electricity must have copper. Formerly iron was used for telegraph wires; but it needs much more electricity to carry power or light or heat or a telegraphic message over an iron wire than one of copper. Moreover, iron will rust and will not stretch in storms like copper, and so needs renewing much oftener. Electric lighting and the telephone are everywhere, even on the summits of mountains and in mines a mile below the earth's surface. Electric power, if a waterfall furnishes the electricity, is the cheapest power known. The common blue vitriol is one form of copper, and to this we owe many of our electric conveniences. It is used in all wet batteries, and so it rings our doorbells for us. It also sprays our apple and peach trees, and is a very valuable article. Indeed, copper in all its forms, pure and alloyed, is one of our best and most helpful friends.



IX

THE NEW METAL, ALUMINUM

Not many years ago a college boy read about an interesting metal called "aluminum." It was as strong as iron, but weighed only one third as much, and moisture would not make it rust. It was made of a substance called "alumina," and a French chemist had declared that the clay banks were full of it; and yet it cost as much as silver. It had been used in France for jewelry and knicknacks, and a rattle of it had been presented to the baby son of the Emperor of France as a great rarity.

The college boy thought by day and dreamed by night of the metal that was everywhere, but that might as well be nowhere, so far as getting at it was concerned. At the age of twenty-one, the young man graduated, but even his new diploma could not keep his mind away from aluminum. He borrowed the college laboratory and set to work. For seven or eight months he tried mixing the metal with various substances to see if it would not dissolve. At length he tried a stone from Greenland called "cryolite," which had already been used for making a kind of porcelain. The name of this stone comes from two Greek words meaning "ice stone," and it is so called because it melts so easily. The young student melted it and found that it would dissolve alumina. Then he ran an electric current through the melted mass, and there was a deposit of aluminum. This young man, just out of college, had discovered a process that resulted in reducing the cost of aluminum from twelve dollars a pound to eighteen cents. Meanwhile a Frenchman of the same age had been working away by himself, and made the same discovery only two months later.

Aluminum is now made from a mineral called "bauxite," found chiefly in Georgia, Alabama, and Arkansas. Mining it is much more agreeable than coal mining, for the work is done aboveground. The bauxite is in beds or strata which often cover the hills like a blanket. First of all, the mine is "stripped,"—that is, the soil which covers the ore is removed,—and then the mining is done in great steps eight or ten feet high, if a hill is to be worked. There is some variety in mining bauxite, for it occurs in three forms. First, it may be a rock, which has to be blasted in order to loosen it. Second, it may be in the form of gray or red clay. Third, it occurs in round masses, sometimes no larger than peas, and sometimes an inch in diameter. In this form it can easily be loosened with a pickaxe, and shoveled into cars to be carried to the mill. Bauxite is a rather mischievous mineral and sometimes acts as if it delighted in playing tricks upon managers of mines. The ore may not change in the least in its appearance, and yet it may suddenly have become much richer or much poorer. Therefore the superintendent has to give his ore a chemical test every little while to make sure that all things are going on well.

This bauxite is purified, and the result is a fine white powder, which is pure alumina, and consists of the metal aluminum and the gas oxygen. Cryolite is now melted by electricity. The white powder is put into it, and dissolves just as sugar dissolves in water. The electricity keeps on working, and now it separates the alumina into its two parts. The aluminum is a little heavier than the melted cryolite, and therefore it settles and may be drawn off at the bottom of the melting-pot.

There are a good many reasons why aluminum is useful. As has been said it is strong and light and does not rust in moisture. You can beat it into sheets as thin as gold leaf, and you can draw it into the finest wire. It is softer than silver, and it can be punched into almost any form. It is the most accommodating of metals. You can hammer it in the cold until it becomes as hard as soft iron. Then, if you need to have it soft again, it will become so by melting. It takes a fine polish and is not affected, as silver is, by the fumes which are thrown off by burning coal; and so keeps its color when silver would turn black. Salt water does not hurt it in the least, and few of the acids affect it. Another good quality is that it conducts electricity excellently. It is true that copper will do the same work with a smaller wire; but the aluminum is much lighter and so cheap that the larger wire of aluminum costs less than the smaller one of copper, and its use for this purpose is on the increase. It conducts heat as well as silver. If you put one spoon of aluminum, one of silver, and one that is "plated" into a cup of hot water, the handles of the first two will almost burn your fingers before the third is at all uncomfortable to touch.



Aluminum is found not only in clay and indeed in most rocks except sandstone and limestone, but also in several of the precious stones, in the yellow topaz, the blue sapphire and lapis-lazuli, and the red garnet and ruby. It might look down upon some of its metallic relatives, but it is friendly with them all, and perfectly willing to form alloys with most of them. A single ounce of it put into a ton of steel as the latter is being poured out will drive away the gases which often make little holes in castings. Mixed with copper it makes a beautiful bronze which has the yellow gleam of gold, but is hard to work. When a piece of jewelry looks like gold, but is sold at too low a price to be "real," it may be aluminum bronze, very pretty at first, but before long its luster will vanish. Aluminum bronze is not good for jewelry, but it is good for many uses, especially for bearings in machinery. Aluminum mixed with even a very little silver has the color and brightness of silver. The most common alloys with aluminum are zinc, copper, and manganese, but in such small quantities that they do not change its appearance.

With so many good qualities and so few bad ones, it is small wonder that aluminum is employed for more purposes than can be counted. A very few years ago it was only an interesting curiosity, but now it is one of the hardest-worked metals. Automobiles in particular owe a great deal to its help. When they first began to be common, in 1904-05, the engines were less powerful than they are now made, and aluminum was largely employed in order to lessen the weight. Before long it was in use for carburetors, bodies, gear-boxes, fenders, hoods, and many other parts of the machine. Makers of electric apparatus use aluminum instead of brass. The frames of opera glasses and of cameras are made of it. Travelers and soldiers and campers, people to whom every extra ounce of weight counts, are glad enough to have dishes of aluminum. The accommodating metal is even used for "wallpaper," and threads of it are combined with silk to give a specially brilliant effect on the stage. It can be made into a paint which will protect iron from rust; and will make woodwork partially fireproof.

Aluminum has been gladly employed by the manufacturers of all sorts of articles, but nowhere has its welcome been more cordial than in the kitchen. Any one who has ever lifted the heavy iron kettles which were in use not so very many years ago will realize what an improvement it is to have kettles made of aluminum. But aluminum has other advantages besides its lightness. If any food containing a weak acid, like vinegar and water, is put into a copper kettle, some of the copper dissolves and goes into the food; acid does not affect aluminum except to brighten it if it has been discolored by an alkali like soda. "Tin" dishes, so called, are only iron with a coating of tin. The tin soon wears off, and the iron rusts; aluminum does not rust in moisture. A strong alkali will destroy it, but no alkali in common use in the kitchen is strong enough to do more harm than to change the color, and a weak acid will restore that. Enameled ware, especially if it is white, looks dainty and attractive; but the enamel is likely to chip off, and, too, if the dish "boils dry," the food in it and the dish itself are spoiled. Aluminum never chips, and it holds the heat in such a manner as to make all parts of the dish equally hot. Food, then, is not so likely to "burn down," but if it does, only the part that sticks will taste scorched; and no matter how many times a dish "boils dry," it will never break. If you make a dent in it, you can easily pound it back into shape again. It is said that an aluminum teakettle one sixteenth of an inch in diameter can be bent almost double before it will break.

Aluminum dishes are made in two ways. Sometimes they are cast, and sometimes they are drawn on a machine. If one is to be smaller at the top, as in the case of a coffeepot, it is drawn out into a cylinder, then put on a revolving spindle. As it whirls around, a tool is held against it wherever it is to be made smaller, and very soon the coffeepot is in shape. The spout is soldered on, but even the solder is made chiefly of aluminum.

Aluminum dishes may become battered and bruised, but they need never be thrown away. There is an old story of some enchanted slippers which brought misfortune to whoever owned them. The man who possessed them tried his best to get rid of the troublesome articles, but they always returned. So it is with an aluminum dish. Bend it, burn it, put acid into it, do what you will to get rid of it, but like the slippers it remains with you. Unlike them, however, it brings good fortune, because it saves time and trouble and patience and money.

A few years ago the motive power for most manufactures was steam. Electricity is rapidly taking its place; and if aluminum was good for nothing else save to act as a conductor of electricity in its various applications, there would even then be a great future before it.



X

THE OIL IN OUR LAMPS

Probably the first man who went to a spring for a drink and found oil floating on the water was decidedly annoyed. He did not care in the least where the oil came from or what it was good for; he was thirsty, and it had spoiled his drink, and that was enough for him. We know now that oil comes chiefly from strata of coarse sandstone, but we are not quite sure how it happened to be there. The sand which formed these strata was deposited by water ages and ages ago—we are certain of that. Another thing that we are certain of is that where the strata lie flat, there is no oil. Hot substances become smaller as they cool; and as the earth grew cooler, it became smaller. The crust of the earth wrinkled as the skin of an apple does when it dries. In the tops of these great sandstone wrinkles there is often gas; and below the gas is the place where oil is found. There is no use in looking for petroleum where the folds of the strata are very sharp, because in that case the strata crack and let the oil flow away. It is not in pools, but the porous stone holds it just as a sponge holds water. If you drop a little oil upon a stone even much less porous than sandstone, it will not be easy to wipe it off, because some of it will have sunk into the stone.

In many places the gas forces its way out, and is piped to carry to houses for light and heat. Not far above Niagara Falls there was a spring of gas which flowed for years. An iron pipe was put down, and when the gas was lighted, the flame shot up three or four feet. The gas came with such force that a handkerchief put over the end of the pipe would not burn, though the flame would blaze away above it. In the country of the fire worshipers, on the shores of the Caspian Sea, fires of natural gas have been burning for ages, kindled, perhaps, by lightning centuries ago. There is a vast supply of oil in this place; and indeed there is hardly a country that has not more or less of it.

In the United States the colonists soon learned that there was petroleum in what is now the State of New York; but New York was a long way from the Atlantic seaboard in those days, and they went on contentedly burning candles or sperm whale oil, or, a little later, a rather dangerous liquid which was known as "fluid." The Indians believed that the oil which appeared in the springs was a good medicine. They threw their blankets upon the water, and when these had become saturated with the oil, they wrung them out and sold the oil. Those were the times when if a medicine only tasted and smelled bad enough, people never doubted that it would cure all their diseases, and they gladly bought the oil of the Indians.

When at last it became clear to the members of an enterprising company that oil for use in lamps could be made from petroleum, they secured some land in Pennsylvania that seemed promising and set to work to dig a well. But the more they dug, the more the loose dirt fell in upon them. Fortunately for the company, the superintendent had brains, and he thought out a way to get the better of the crumbling soil. He simply drove down an iron pipe to the sandstone which contained the oil, and set his borer at work within the pipe. One morning he found that the oil had gushed in nearly to the top of the well. He had "struck oil."

This was about ten years after the rush to California for gold, and now that this cheaper and quicker method of making a well had been invented, there was almost as much of a rush to Pennsylvania for oil. With every penny that they could beg or borrow, people from the East hurried to the westward to buy or lease a piece of land in the hope of making their fortunes. A song of the day had for its refrain,—

"Stocks par, stocks up, Then on the wane; Everybody's troubled with Oil on the brain."

In the course of a year or two, the first "gusher" was discovered. The workmen had drilled down some four or five hundred feet and were working away peacefully, when a furious stream of oil burst forth which hurled the tools high up into the air. Hundreds of barrels gushed out every day, and soon other gushers were discovered. The most famous one in the world is at Lakeview, California. For months it produced fifty thousand barrels of oil a day, and threw it up three hundred and fifty feet into the air in a black column, spraying the country with oil for a mile around. The oil flowed away in a river, and for a time no one could plan any way to stop it or store it. At last, however, a mammoth tank was built around the well and made firm with stones and bags of earth. This was soon full of oil; and with all this vast weight of oil pressing down upon it, the stream could not rise more than a few feet above the surface. Just why oil should come out with such force, the geologists are not quite certain; but it is thought to result from a pressure of gas upon the sandstone containing it. The flow almost always becomes less and less, and after a time the most generous well has to be pumped.



An "oil field" may extend over thousands of square miles; but within this field there are always "pools"; that is, certain smaller fields, where oil is found. When a man thinks there is oil in a certain spot, sometimes he buys the land if he is able; but oftener he gets permission of the owner to bore a well, agreeing to pay him a royalty; that is, a certain percentage of all the oil that is produced. When this has been arranged, he builds his derrick. This consists of four strong upright beams firmly held together by crossbeams. It stands directly over the place where the well is to be dug. It is from thirty to eighty feet in height, according to the depth at which it is hoped to find oil. There must also be an engine house to provide the power for drilling. An iron pipe eight or ten inches in diameter is driven down through the soil until it comes to rock. Now the regular drilling begins. At the top of the derrick is a pulley. Over the pulley passes a stout rope to which the heavy drilling tools—the "string of tools," as they are called—are fastened. The drilling goes on day and night. The drill makes the hole, and the sand pump sucks out the water and loose bits of stone. When the drill has gone to the bottom of the strata which carry water, the sides of the bore are cased to keep the water out; then the drilling continues, but now the drill makes its way into the oil-bearing sandstone.

There is nothing certain about the search for oil. In some places it is near the surface, in others it is perhaps three or four thousand feet down. The well may prove to be a gusher and pour out hundreds of thousands of gallons a day; or the oil may refuse to rise to the surface and have to be pumped out even at the first. Naturally, no one is prepared for a gusher, and millions of gallons have often flowed away before any arrangements could be made for storing the oil. Sometimes a well that gives only a moderate flow can be made to yield generously by exploding a heavy charge of dynamite at the bottom, to break up the rock and, it is always hoped, to open some new oil-holding crevice that the drill has not reached.

Crude petroleum is a dark, disagreeable, bad-smelling liquid; and before it can be of much use, it must be refined. For several years it was carried in barrels from the oil fields to Pittsburgh by wagon and boat, a slow, expensive process, and generally unsatisfactory to all but the teamsters. Then came the railroads. They provided iron tanks in the shape of a cylinder fastened to freight cars, much like those employed to-day. There was only one difficulty about sending oil by rail, and that was that it still had to be hauled by team to the railroad, sometimes a number of miles. At length, some one said to himself, "Why cannot we simply run a pipe directly from the well to the railroad?" This was done. Pumping engines were put in a few miles apart, and the invention was a success in the eyes of all but the teamsters. In spite of their opposition, however, pipe-lines increased.

Before this it had been necessary to build the refineries as near the oil regions as possible in order to save the expense of carrying the oil; but now they could be built wherever it was most convenient. To-day oil can be brought at a small expense from west of the Mississippi River to the Atlantic seaboard, refined, and distributed throughout that part of the country, or loaded into "tankers,"—that is, steamships containing strong tanks of steel,—and so taken across the ocean. The pipes are made of iron and are six or eight inches or more in diameter. In using them one difficulty was found which has been overcome in an ingenious fashion. Sometimes they become choked by the impurities of the oil and the flow is lessened. Then a "go-devil" is put into them. This is shaped like a cartridge, is about three feet in length, composed of springs and plates of iron and so flexible that it can turn around a corner. It is so made that as it slips down the current of oil, it whirls around and in so doing its nose of sharp blades scrapes the pipes clean.

The pipes go over hills and through swamps. They cross rivers sometimes by means of bridges, and sometimes they are anchored to the bed of the stream. If they have to go through a salt marsh, they are laid in concrete to preserve the iron. If these lines were suddenly destroyed and oil had to be carried in the old way, kerosene would become an expensive luxury.

Getting the oil out of the ground and carried to the refineries is not all of the business by any means. The early oils crusted on the lamp wicks, their smell was unendurable, and they were given to exploding. Evidently, if oil was to be used for lighting, it must be improved, and the first step was to distil it. To distil anything means to boil it and collect the vapor. If you hold a piece of cold earthenware in the steam of a teakettle, water will collect on it. This is distilled water, and is purer than that in the kettle. Petroleum was at first distilled in a rough way; but now it is done with the utmost care and exactness. The crude oil is pumped into boilers holding six hundred barrels or more. The fires are started, and the oil soon begins to turn into vapor. This vapor passes through coils of pipe or long, straight, parallel pipes. Cold water is pumped over these pipes, the vapor turns into a liquid again, and we have kerosene oil.

This is the outline of the process, but it is a small part of the actual work in all its details. Kerosene oil is only one of the many substances found in petroleum. Fortunately, some of these substances are light, like gasoline and benzine; some, like kerosene, are heavier; and paraffin and tar are heaviest of all. There are also gases, which pass off first and are saved to help keep the furnace going. Then come the others, one by one, according to their weight. The stillman keeps close watch, and when the color and appearance of the distillate changes, he turns it off into another tank. This process is called "fractional distillation," and the various products are called "fractions." No two kinds of petroleum and no two oil wells are just alike, and it needs a skillful man to manage either.

Even after all this distillation, the kerosene still chars the wick somewhat—which prevents the wick from drawing up the oil properly—and it still has a disagreeable smell. To fit it for burning in lamps, it must be treated with sulphuric acid, which carries away some of the impurities, and then with caustic soda, which carries away others. Before it can be put on the market, it is examined to see whether it is of the proper color. Then come three important tests. The first is to see that it is of the proper weight. If it is too heavy, it will not burn freely enough; if it is too light, then there is too much of the lighter oils in it for safety. The second test is the "flash test." The object of this is to see how hot the oil must be before it gives off a vapor which will burn. The third, the "burning test," is to discover how hot the oil must be before it will take fire and burn on the surface. Most civilized countries make definite laws forbidding the sale of kerosene oil that is not up to a standard of safety. Oil for use in lamps should have an open flash test of at least 100 deg. F. and a burning point of not less than 125 deg. F.

We say that we burn oil in our lamps, but what we really do is to heat the oil until it gives off gas, and then we burn the gas. To keep the flame regular and help on the burning, we use a chimney on the lamp. The hot air rises in the chimney and the cold air underneath rushes in to take its place and brings oxygen to the flame. In a close, stuffy room no lamp will give a good clear light, because there is not oxygen enough for its flame. Let in fresh air, and the light will be brighter. If you hold a cold plate in the flame before the chimney is put on, soot or carbon will be deposited. A lamp gives light because these particles of carbon become so hot that they glow. In lamps using a "mantle," there is the glow not only of these particles, but also of the mantle. In a wax candle, we light the wick, its heat melts the wax and carries it to the flame. When the wax is made hot enough, it becomes gas, and we burn the gas, not the wax. Wax alone will melt, but not take fire even if a burning match is held to it. The reason is that the match does not give heat enough to turn the wax into gas. But put a bit of wax upon a bed of burning coals, where there is a good supply of heat, and it will turn into gas and burn.

The products made from petroleum are as different in their character 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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FIRST YEAR IN NUMBER

35 cents net. Postpaid

An Introductory Book to Precede any Series of Arithmetics

BY

FRANKLIN S. HOYT

Formerly Assistant Superintendent of Schools, Indianapolis

AND

HARRIET E. PEET

Instructor in Methods of Teaching Arithmetic, State Normal School, Salem, Massachusetts

The work is based upon the familiar experiences and activities of children, and follows as closely as possible the child's own method of acquiring new knowledge and skill.

Thus we have lessons based on playing store, making tickets, mailing letters, fishing, etc. Every step is made interesting, but no time is wasted in mere entertainment.

* * * * *

By the same authors

THE EVERYDAY ARITHMETICS

THREE-BOOK COURSE

Book One, grades II-IV $.40 Book Two, grades V-VI .40 Book Three, grades VII-VIII .45

TWO-BOOK COURSE

Book One, grades II-IV. $.40 Book Two, grades V-VIII. .72

Course of Study (with answers) $.25

Distinctive Features

1. Their socialized point of view—all problems and topics taken from the everyday life of children, home interests, community interests, common business and industries. 2. Their attractiveness to children—spirited illustrations, legible page, interesting subject matter. 3. The omission of all antiquated topics and problems. 4. The grouping of problems about a given life situation. 5. The development of accuracy and skill in essential processes. 6. The vocational studies. 7. The careful attention to method. 8. The exact grading. 9. The systematic reviews. 10. The adaptation to quick and to slow pupils.

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HOUGHTON MIFFLIN COMPANY BOSTON NEW YORK CHICAGO 1901



"A STEP FORWARD IN READING"

THE RIVERSIDE READERS

EDITED BY

JAMES H. VAN SICKLE

Superintendent of Schools, Springfield, Mass.

AND

WILHELMINA SEEGMILLER

Late Director of Art, Indianapolis. Formerly Principal of the Wealthy Avenue Public School, Grand Rapids, Mich.

ASSISTED BY

FRANCES JENKINS

Instructor in Elementary Education, College for Teachers, University of Cincinnati, Formerly Supervisor of Elementary Grades, Decatur, Ill.

ILLUSTRATED BY

RUTH MARY HALLOCK MAGINEL WRIGHT ENRIGHT CLARA E. ATWOOD E. BOYD SMITH HOWARD PYLE, and other notable artists

FRESH MATERIAL

These Readers contain an unusually large amount of fresh copyrighted material taken from the world's best literature for children.

LATEST TEACHING METHODS

They represent the latest developments in the methods of teaching reading, the kind of teaching that will be found in the best schools of to-day.

ARTISTIC MAKE-UP

Artistically the books will set a new standard in text-book making. The colored Illustrations of the primary books are particularly attractive.

MECHANICAL FEATURES

The paper used in the books, the type for each grade, and the dimensions and arrangement of the type page were all determined by careful experimenting, in order to safeguard the eyesight of children.

Send for complete illustrated circular describing the unique plan of this series.

PRICES

Primer 30 cents, net. First Reader 35 cents, net. Second Reader 40 cents, net. Third Reader 50 cents, net. Fourth Reader 55 cents, net. Fifth Reader 55 cents, net. Sixth Reader 55 cents, net. Seventh Reader 55 cents, net. Eighth Reader, 60 cents, net.

* * * * *

HOUGHTON MIFFLIN COMPANY BOSTON NEW YORK CHICAGO 1901



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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.

THE END