Chapter II: Part 2

When the bricks come out of the kiln, some of them are good and some are not. Those that were on the outside are not burned enough; those next it are not well baked, but can be used for the middle of thick walls. The next ones are of good quality; but those directly over the fires are so hard and brittle that they are of little use except for pavements.

Paving-bricks, however, are not to be despised. They are not as smooth and well finished as pressed brick, but they are exceedingly useful. They need as much care in making as any others, and they must be burned in a much hotter fire to make them dense and hard. The tests for paving-bricks are quite different from those for ordinary building-brick. If first-class paving-bricks weighing fifty pounds are soaked in water for twenty hours, they take up so little water that they will not weigh more than fifty-one or fifty-one and a half pounds when taken out. To find out how hard they are, the bricks are weighed and shaken about with foundry shot for a number of hours. Then they are weighed again to see how much of their material has been rubbed off. A third test is to put one brick on edge into a crushing machine to see how much pressure it will stand. Paving-brick is cheaper than granite blocks, and if it has a good foundation of concrete covered with sand, it will last about three fourths as long. Brick is less noisy than stone and is easier to clean.

Not so very long ago, when particularly handsome bricks were needed for the outside of walls and other places where they would be conspicuous, they were "re-pressed"; that is, they were made by hand or in a "soft-mud" machine, and then, after drying for a while, were put into a re-pressing machine to give them a smooth finish. These machines are still used, but they are hardly necessary, for the "dry-clay" brick machine will turn out a smooth brick in one operation.

Another substance which is made of almost the same materials as brick is terra cotta. To make this, fire brick, bits of pottery, partly burned clay, and fine white sand are ground to a powder and mixed very thoroughly. This mixture is moulded, dried, and burned. Until recently, all terra cotta was of the color that is called by that name, but now it is made in gray, white, and bronze as well.

Bricks are laid in mortar, and this makes a wall one solid mass and stronger than it could be without any cement. But mortar does more than this. It is more elastic than brick, and therefore, when a wall settles, the mortar yields a little, and this often prevents the bricks from cracking. Bricks are always thirsty, and if one is laid in mortar, it will suck the moisture out of it almost as a sponge will suck up water. The mortar thus has no chance to set, and so is not strong as it should be. That is why the bricklayer wets his bricks, especially in summer, before he puts them in place. Lime or cement mortar will not set in freezing weather, and a brick building put up in the winter is in danger of tumbling down when the warm days of spring arrive.

This thirstiness of bricks is their greatest fault. Three or four days of driving rain will sometimes wet through a brick wall two feet thick, crumbling the plaster and spoiling the wallpaper. That is why it is a poor plan to plaster directly on the brick wall of a house. "Furring" strips, as they are called, or narrow strips of wood, should be fastened on first and the laths nailed to these, or the wall can be painted or oiled on the outside. The best way, however, though more expensive, is to build the wall double. Then there is air between the two thicknesses of brick. Air is a poor conductor of heat; so in summer it keeps the heat out, and in winter it keeps it in.

But brick will suck up water from the ground as well as from a storm; and therefore, when a brick house is to be built in a wet place, there ought to be a three-eighths-inch layer of something waterproof, like asphalt and coal tar, put on top of one of the layers of brickwork to prevent the moisture from creeping up.

Bricks have their faults, but they will not burn, and when properly used, they make a most comfortable and enduring house.

V

AT THE GOLD DIGGINGS

When gold was first discovered in California, in 1848, people from all over the world made a frantic rush to get there, every one of them hoping that he would be lucky enough to make his fortune, and fearing lest the precious metal should be gone before he could even begin to dig. The gold that these men gathered came from what were called "placers"; that is, masses of gravel and sand along the beds of mountain streams. Each miner had a pan of tin or iron, which he filled half-full of the gravel, or "pay dirt," as the miners called it. Then, holding it under water, he shook off the stones and mud over the side of the pan, leaving grains of gold mixed with black sand at the bottom. This black sand was iron, and after a while the miners removed it with a magnet, dried what remained, and blew away the dust, leaving only the grains of gold.

Another contrivance which soon came into use was the "cradle." This was a long box, sometimes only a hollowed-out log. At the top was a sieve which sifted out the stones. Nailed to the bottom of the cradle were small cleats of wood, or "riffles," which kept the water from running so fast as to sweep the gold out of the cradle with it. The cradle was placed on rockers and was also tilted slightly. The miner shoveled the gravel into the top of the cradle and his partner rocked it. The sieve kept back the stones, the water broke up the lumps of earth and gravel and washed them down the cradle, and the grains of gold were stopped by the riffles, and sank to the bottom. Sometimes the "pay dirt" continued under a stream. To get at it, the miners often built a little canal and turned the water into a new channel; then they could work on the former bed of the river.

Before many years had passed, the gold that was near the surface had been gathered. The miners then followed the streams up into the mountains, and found that much of the gold had come from beds where in ancient times rivers had flowed. There was gold still remaining in these beds, but it was poorly distributed, the miners thought. Sometimes there would be quite an amount in one place, and then the miner would dig for days without finding any more. Even worse than this was the fact that these gravel beds were not on the top of the ground, but were covered up with soil and trees. Evidently the slow work with pans and cradles would not pay here; but it occurred to some one that if a powerful stream of water could be directed against the great banks of earth, as water is directed against a burning building, they would crumble, the dirt could be washed down sluices, and the gold be saved. This was done. Great reservoirs were built high up in the mountains, and water was brought by means of ditches or pipes to a convenient place. Then it was allowed to rush furiously through a hose and nozzle, and the great stream coming with tremendous force was played upon the banks of gravel. The banks crumbled, the gravel was washed into a string of sluices, or long boxes with riffles to catch the gold. Soon the miners found that if quicksilver was put into these sluices, it would unite with the gold and make a sort of paste called "amalgam." Then if this amalgam was heated, the quicksilver would be driven off in the form of gas, and the gold would remain in a beautiful yellow mass.

A placer mine at Gold Point, California, where tremendous streams of water under high pressure are busy washing away the side of a gold-bearing hill.]

The ancient rivers had also carried gold to the valleys, and to collect this a dredge, which the miners called a "gold ship," came into use. The "ship" part of this machine is an immense flat scow. Stretching out from one end is something which looks like a moving ladder. This is the support of an endless chain of buckets, each of which can bite into the gravel and take a mouthful of five or six hundred pounds. They drop this gravel into a big drum which is continually revolving. Water flows through the drum, and washes out the sand and bits of gold over large tables, where by means of riffles and quicksilver the gold is captured. This scow was usually on dry land at first; but its digging soon made a lake, and then it floated. It must be more fascinating to hold a pan in your own hands and pick out little grains of gold or perhaps even a big piece of it with your own fingers, but if the gravel is good the dredge makes more money.

In Alaska the great difficulty in mining is that, except at the surface, the ground is frozen all the year round. At first, the miners used to thaw the place where they wished to dig by building wood fires; but this was a slow method, and now the thawing is done by steam. They carry the steam in a pipe to the place where the digging is to be done, and send it through a hose. At the end of the hose is a pointed steel tube. They hammer this tube into the ground and let some steam pass through the nozzle. This softens the ground so that picks and shovels may be used. There is generally cold enough in Alaska, but once at least the miners had to manufacture it. The gold-bearing gravel was deep, the ground was flat, and it was often overflowed. They set up a freezing plant, and shut in their land with a bulkhead of ice several feet thick. Then they pumped out what water was already in and did their work with no more trouble.

When gold began to grow less in the California gravel, the miners looked for it in the rocks on the mountain-side. The placer miners laughed at them and called their shafts "coyote holes"; but in time the placers failed, while nearly all of our gold to-day comes from veins of white quartz in the rocks. A vein of gold is the most capricious thing in the world. It may be so tiny that it can hardly be seen, then widen and grow rich in gold, then suddenly come to an end. This is why a new mine is so uncertain an enterprise. The gold may hold out and bring fortunes to the investors, or it may fail, and then all they will have to show for their money is the memory that they put it into a hole in the ground. The managers of a few of the well-established mines, however, have explored so far as to make sure that there is gold enough for many years of digging.

The mining engineer must be a very wide-awake man. It is not enough for him simply to remember what was taught him in the schools of mining; he must be bright enough to invent new ways of meeting difficulties. No two mines are alike, and he must be ready for all sorts of emergencies. A gold mine now consists of a shaft or pit dug several hundred feet down into the rock, with levels or galleries running off from it and with big openings like rooms made where the rock was dug out. The roofs of the rooms are supported by great timbers. To break away the rock, the miner makes a hole with a rock drill worked by electricity or compressed air, puts powder or dynamite into the hole and explodes it. The broken rock is then raised to the surface and crushed in a "stamping mill." Here the ore is fed into a great steel box called a "mortar." Five immense hammers, often weighing a thousand pounds apiece, drop down upon the ore, one after another, until it is fine enough to go through a wire screen in the front of the box. When two hundred or more of these hammers are pounding away with all their might, a stamping mill is a pretty noisy place. The ore, crushed to a fine mud, now runs over sloping tables covered with copper. Sticking to the top of the copper is a film of quicksilver. This holds fast whatever gold there may be and makes an amalgam, which is scraped off from time to time, and the quicksilver is driven from the gold by heat.

Gold that is not united with other metals is called "free milling gold." Much of it, however, is found in combination with one metal or another, and is known as "rebellious" or "refractory" gold. Such gold may sometimes be set free by heat, and sometimes by chemicals. One way is by the use of chlorine gas, and the story of it sounds almost like "The house that Jack built." It might run somewhat like this: This is the salt that furnishes the chlorine. This is the chlorine gas that unites with the gold. This is the chloride that is formed when the chlorine gas unites with the gold. This is the water that washes from the tank the chloride that is formed when the chlorine gas unites with the gold. This is the sulphate of iron that unites with the chlorine gas of the chloride that the water washes from the tank that is formed when the chlorine gas unites with the gold--and leaves the gold free.

Another method is by the use of cyanide. More than a century ago a chemist discovered that if gold was put into water containing a little cyanide, the gold would dissolve, while quartz and any metals that might be united with the gold would settle in the tank. The water in which the gold is dissolved is now run into boxes full of shavings of zinc and is "precipitated" upon them; that is, the tiny particles of gold in the water fall upon the zinc and cling to it. Zinc melts more easily than gold, so if this gilded zinc is put into a furnace, the zinc melts and the gold is set free.

Very often gold is found combined with lead or copper. It must then be melted or smelted in great furnaces. The metal is heavier than the rock and settles to the bottom of the furnace. It is then drawn off and the gold is separated from the other metals, usually by electricity.

Sometimes large pieces of gold called "nuggets" are found by miners. The largest one known was found in Australia. It weighed 190 pounds and was worth $42,000. Sometimes spongy lumps of gold are found; but as a general thing gold comes from the little specks scattered through veins in rock, and much work has to be done before it can be made into coins or jewelry. It is too soft for such uses unless some alloy, usually copper or silver, is mixed with it to make it harder. Sometimes it is desirable to know how much alloy has been added. The jeweler then makes a line with the article on a peculiar kind of black stone called a "touchstone," and by the color of the golden mark he can tell fairly well how nearly pure the article is. To be more accurate, he pours nitric acid upon the mark. This eats away the alloy and leaves only the gold.

Gold is a wonderful metal. It is of beautiful color; it can be hammered so thin that the light will shine through it; few acids affect it, and the oxygen which eats away iron does not harm it. Pure gold is spoken of as being "twenty-four carats fine," from _carat_, an old weight equal to one twenty-fourth of an ounce troy. Watchcases are from eight to eighteen carats fine; chains are seldom more than fourteen; and the gold coins of the United States are about eleven parts of gold and one of copper. Coins wear in passing from one person to another, and that is why the edges are milled, so that it may be more easily seen when they have become too light to be used as coins. When such pieces come into the hands of the Government, they must be recoined.

VI

THE STORY OF A SILVER MINE

A man who goes out in search of a mine is called a "prospector." The best prospector is a man who has learned to keep his eyes open and to recognize the signs of gold and silver and other metals. A faithful friend goes with him, a donkey or mule which carries his bacon and beans, blankets, saucepan, and a few tools, such as a pan, pick, shovel, hammer, and axe. Sometimes the prospector also takes with him a magnifying glass and a little acid to test specimens, but usually he trusts to his eyes alone.

When these few things have been brought together, the prospector and the donkey set out. They wander over the hills and down into the canyons. If a rock is stained red, the prospector examines it to see whether it contains iron; if it is green, he looks for copper. In the canyons and along the creeks he often tests the gravel for traces of some valuable metal. If he finds any of these traces along the stream, he follows them on the bank until they stop; then he carefully examines the bank of the stream or the nearest hillside. If he continues to find bits of metal, they will lead him to a vein of ore, from which they have been broken by the wind, rain, and frost.

Generally a prospector is looking for some one special metal, and in his search he often overlooks some other metal; for instance, thousands of the gold-seekers who rushed to California in 1849 hurried through Nevada on their way. If they had only known what was under their feet, they would have taken their picks and shovels and begun to dig, instead of trying to get out of the region as soon as might be. Ten years later, the California placers were becoming exhausted, and miners began to go elsewhere in their search for gold.

Among those who were working in what is now the State of Nevada were two Irishmen who had been unlucky in California and had fared no better in Nevada. They wanted to go somewhere else, but they had not money enough for the journey; so they kept on with their work at the foot of Mount Davidson, washing the gravel and saving the little gold that they found. They were annoyed by some heavy black stuff that united with the quicksilver in their cradles, interfered with the saving of the gold, and put them in a very bad temper. At length a man named Henry Comstock came along, who told them that this black stuff was silver ore. They examined the mountain-side, and discovered the outcrop or edge of a great vein containing gold and also silver. It is no wonder that people rushed from the east and west to the wonderful new mines, for it was plain that these new "diggings" were not mere placers, but rich veins that many years of working might not exhaust. Every newcomer hoped to discover a vein; and within a year or two the district around the Comstock lode was full of deep shafts, many of them abandoned and half-hidden by low brush, but some of them yielding quantities of gold and silver. Before this, there had been only about a thousand people in what is now Nevada, but in two years after the discovery of silver, there were 16,000, and a new Territory was formed.

The miners knew how to get gold out of ore, but silver was another matter, and some of it was difficult to extract. They had so much trouble that they were ready to believe in any treatment of the ore, no matter how absurd, that promised to help them out of their difficulties. Some of them were actually persuaded that the juice of the wild sagebrush would bring the silver out. It is no wonder that they were troubled, for in the Comstock lode were not only gold and silver, but ten or twelve other metals or combinations of silver with something else. At length processes were invented for treating the different kinds of ore. Some kinds were crushed in a stamping mill, then ground to a powder and mixed with quicksilver or mercury. This mercury united with both the gold and the silver, making an amalgam. The amalgam, together with the finely ground ore, was put into a "settler," and here the heavy amalgam sank to the bottom and was then strained. The extra mercury was collected, and the amalgam was put into a retort or kettle and heated. The mercury became a gas and was driven off from the gold and silver, then caught in a vessel cool enough to condense it, just as a cold plate held in steam will collect drops of water. Sometimes the ore was mixed with copper and lead. In that case common salt and copper sulphate were used. Some ore had to be roasted in a furnace in order to drive off the sulphur.

_Courtesy The Gorham Co._

(1) Silver strip blanked. (2) Pinched. (3) Graded. (4) Outlining of Handle. (5) Stamped Handle. (6) Spoon completely trimmed. (7, 8) Finished spoons.]

There were great and unusual dangers to be met in getting the ore. The vein of quartz which bore it was fifty or sixty feet wide. Some was hard, and some so soft and crumbling that pillars would not hold up the roof. The passageways were then lined with heavy logs standing on either side, other logs laid across their tops, and all bolted firmly together. Nevertheless, they twisted and fell, and slowly but certainly the whole mass of earth and rock, two hundred or more feet in thickness, was coming down upon the heads of the miners. The work on the Comstock mines had come to an end unless a man could be found able to invent some system of support not laid down in the books. The man was found. He took short, square timbers five or six feet long, put them together as if they were the sides and ends of square boxes, and piled them one above another, making hollow pillars. He fastened these firmly together and filled the space inside with waste rock, thus making strong, solid pillars that would support almost any weight that could be put upon them.

There were two other dangers, water and heat. The vein was porous and water was constantly trickling out of it. Then, too, there were "water pockets," or natural reservoirs in the rock, and any moment the stroke of a pick might let out a torrent and force the miners to run for their lives. Sometimes minerals were dissolved in this water, and the men with closed eyes and swollen faces had to be hurried to the surface for treatment. Powerful pumps had to be used and the water sent away through long lines of pipes. This water was warm, and in very deep workings in the Comstock vein it was boiling hot. Even with quantities of ice sent down to cool them, the men could work in some places only a short time.

In San Francisco there was a mining engineer named Adolph Sutro who planned to remedy these troubles by driving a big four-mile tunnel through the heart of the mountain, letting out the hot water and the foul air. The owners of some of the mines joined him in raising the money, and the tunnel was dug. Through this the water ran out. The mines were freed of foul air and fresh air was driven in.

The Comstock lode has given up an amazing amount of precious metal. Between 1860 and 1890 it produced $340,000,000. After 1890, however, its product grew less. The vein was not so rich, the price of silver fell, while the cost of mining it at great depths increased. Not nearly so much was mined, and at length water rose in the mines up to the level of the Sutro Tunnel. In 1900 new machinery was put in and new methods were adopted, such as treating the tailings with cyanide and so saving much of the precious metal from them. From the beginning the Comstock mines have been so ready to follow improved methods that they have been called the mining school of the world.

Great quantities of silver are used for making jewelry and for tableware. The one objection to its use is that silver likes to unite with sulphur, and thus the silver easily becomes black. There is sulphur in the yolk of an egg and that is why the spoon with which it has been eaten turns black. Even if silverware is not used, it tarnishes, especially in towns, because there is so much sulphureted hydrogen in the air. In perfectly pure air, it would not tarnish. Silver is harder than gold, but not hard enough to be used without some alloy, usually copper. Tableware is "solid" even if it contains alloy enough to stiffen it. It is "plated" if it is made of some cheaper metal and covered with silver. The old way of doing this was to fasten with bits of solder a thin sheet of silver to the cup or vase or whatever was in hand and heat it. This did fairly well for large, smooth articles; but it was almost impossible to finish the edges of spoons so as not to show the two metals. If you look at a plated spoon to-day, however, you will find that there is no break at the edge, and so far as you can tell by the eye, it is solid silver. If you look on the back of the spoon, you will perhaps see "Rogers Bros. 1846." These men were the first silvermakers in this country to plate tableware by electricity. To make a spoon, they formed one out of iron or copper and made sure that it was perfectly clean. Then across a bath of silver cyanide, potassium cyanide, and water they laid two metal rods, and from these they hung a spoon at one end and a plate of silver at the other. These rods were connected with the two poles of a battery. The electrical current passed through them, released the silver from the silver cyanide, and this was deposited upon the spoon. The cyanide that had lost its silver took enough more from the silver plate to make up. The amount of silver on the spoon depends upon the length of time it remains in the bath. It is weighed before plating and again afterwards, to make sure that the proper amount of silver has been deposited upon it. On the back of many plated articles you will see the words "Triple plate" or "Quadruple plate." If the article has been made by a reliable firm, this means that the triple plate it manufactures contains three times as much silver as "single plate," and that quadruple plate contains four times as much. A piece of silver looks just as well if it has stayed in the bath only a few minutes, but of course it has taken on so little silver that this will soon wear off and show the cheaper metal.

A large amount of silver is used for coins. When the United States needs dollars, half-dollars, quarters, and dimes, notice is given and offers are called for, stating the quantity for sale and its price. When it is delivered, it is first of all "assayed"; that is, tested to find out how nearly pure it is and how much it is worth. Next it is refined, or purified from other metals, mixed with a little copper to harden it, then melted again and poured into moulds to make bars. If dollars are to be made, the bar is made thinner by passing it between heavy rollers, and blanks for dollars are cut out with a die. These blanks are weighed and every one that is too heavy or too light is put back to be melted over again. Thus far these dollars are only round, smooth pieces of metal. They must be milled to give them a rough edge, and they must be stamped. For stamping, the piece of metal is placed between two dies, one above and one below, and these close upon it with a force of one hundred and fifty tons. Every part of the process of manufacturing money is carried on with the utmost care. The places where coins are made are called "mints." The United States has four; the oldest is in Philadelphia, and there are branch mints in San Francisco, New Orleans, and Denver. Coins minted in Philadelphia have no distinguishing mark; but coins minted in San Francisco are marked with a tiny "S"; if minted in New Orleans, with an "O"; and if in Denver, with a "D."

VII

IRON, THE EVERYDAY METAL

Did you ever realize that your food and clothes, your books, and the house in which you live all depend upon iron? Vegetables, grains, and fruits are cultivated with iron tools; fish are caught with iron hooks, and many iron articles are used in the care and sale of meat. Clothes are woven on iron looms, sewed with iron needles, and fastened together with buttons containing iron. Books are printed and bound by iron machines, and sometimes written with iron pens or on iron typewriters. Houses are put together with nails; and indeed, there is hardly an article in use that could be made as well or as easily if iron was not plenty. If you were making a world and wanted to give the people the most useful metal possible, the gift would have to be iron; and the wisest thing you could do would be to put it everywhere, but in such forms that the people would have to use their brains to make it of service.

This is just the way with the iron in our world. Wherever you see a bank of red sand or red clay or a little brook which leaves a red mark on the ground as it flows, there is iron. Iron is in most soils, in red bricks, in garnets, in ripening apples, and even in your own blood. It forms one twentieth part of the crust of the earth. Iron dissolves in water if you give it time enough. If you leave a steel tool out of doors on a wet night, it will rust; that is, some of the iron will unite with the oxygen of the water. This is rather inconvenient, and yet in another way this dissolving is a great benefit. Through the millions of years that are past, the oxygen of the rain has dissolved the iron in the hills and has worked it down, so that now it is in great beds of ore or in rich "pockets" that are often of generous size. One of them, which is now being mined in Minnesota, is more than two miles long, half a mile wide, and of great thickness. The rains are still at work washing down iron from the hills. They carry the tiny particles along as easily as possible until they come upon limestone. Then, almost as if it was frightened, the brook drops its iron and runs away as fast as it can. Sometimes it flows into a pond or bog in which are certain minute plants or animals that act as limestone does, and the particles of iron fall to the bottom of the pond. In colonial days much of the iron worked in America was taken from these deposits. One kind of iron is of special interest because it comes directly from the sky, and falls in the shape of stones called "meteorites," some of which weigh many tons. In some of the old fables about wonderful heroes, the stories sometimes declare that the swords with which they accomplished their deeds of prowess fell straight from the heavens, which probably means that they were made of meteoric iron. Fortunately for the people and their homes, meteorites are not common, but every large museum has specimens of them.

It is not especially difficult to make iron if you have the ore, a charcoal fire in a little oven of stones, and a pair of bellows. Put on layers of charcoal alternating with layers of ore, blow the bellows, and by and by you will have a lump of iron. It is not really melted, but it can be pounded and worked. This is called the "Catalan method," because the people of Catalonia in Spain made iron in this way. It is still used by the natives of the interior of Africa. But if all the iron was made by this method, it would be far more costly than gold. The man who makes iron in these days must have an immense "blast furnace," perhaps one hundred feet high, a real "pillar of fire." Into this furnace are dropped masses of ore, and with it coke to make it hotter and limestone to carry off the silica slag, or worthless part. To increase the heat, blasts of hot air are blown into the bottom of the furnace. This air is heated by passing it through great steel cylinders as high as the furnace. The fuel used is nothing more than the gases which come out at the top of the furnace.

The slag is so much lighter than iron that when the ore is melted the slag floats on top just as oil floats on water, and can be drained out of the furnace through a higher opening than that through which the iron flows. The slag tap is open most of the time, but the iron tap is opened only once in about six hours. It is a magnificent sight when a furnace is "tapped" and the stream of iron drawn off. Imagine a great shed, dark and gloomy, with many workmen hurrying about to make ready for what is to come. The floor is of sand and slopes down from the furnace. Through the center of this floor runs a long ditch straight from the furnace to the end of the shed. Opening from it on both sides are many smaller ditches; and connecting with these are little gravelike depressions two or three feet long and as close together as can be. These are called "pigs." When the time has come, the workmen gather about the furnace, and with a long bar they drill into the hard-baked clay of the tapping hole. Suddenly it breaks, and with a rush and a roar the crimson flood of molten iron gushes out. It flows down the trench into the ditches, then into the pigs, till their whole pattern is marked out in glowing iron. Now the blast begins to drive great beautiful sparks through the tapping hole. This means that the molten iron is exhausted. The blast is turned off, and the "mud-gun" is brought into position and shoots balls of clay into the tapping hole to close it for another melting, or "drive." The crimson pigs become rose-red, darken, and turn gray. The men play streams of water over them and the building is filled with vapor. As soon as the pigs are cool enough, they are carted away and piled up outside the building.

In some iron works moulds of pressed steel carried on an endless chain are used instead of sand floors. The chain carries them past the mouth of a trough full of melted iron. They are filled, borne under water to be cooled, and then dropped upon cars. A first-class machine can make twenty pigs a minute.

It is a dangerous business to visit a steel mill. Tremendous kettles travel overhead on huge cranes, hot metal flows from unexpected places, and there is a constant glow and steam and roar everywhere to confuse the unwary.]

Most of the iron made in blast furnaces is turned into steel. Steel has been made for centuries, but until a few years ago the process was slow and costly. A workman's steel tools were treasures, and a good jackknife was a valuable article. Railroads were using iron rails. They soon wore out, but at the suggestion to use steel, the presidents of the roads would have exclaimed, "Steel, indeed! We might as well use silver!" Trains needed to be longer and heavier, but iron rails and bridges could not stand the strain. Land in cities was becoming more valuable; higher buildings were needed, but stone was too expensive. Everywhere there was a call for a metal that should be strong and cheap. Iron was plentiful, but steel was dear. A cheaper method of making iron into steel was needed; and whenever there is pressing need of an invention, it is almost sure to come. Before long, what is known as the "Bessemer process" was invented. One great difficulty in the manufacture of steel was to leave just the right amount of carbon in the iron. Bessemer simply took it all out, and then put back exactly what was needed. Molten iron, tons and tons of it, is run into an immense pear-shaped vessel called a "converter." Fierce blasts of air are forced in from below. These unite with the carbon and destroy it. There is a roar, a clatter, and a clang. Terrible flames of glowing red shoot up. Suddenly they change from red to yellow, then to white; and this is the signal that the carbon has been burned out. The enormously heavy converter is so perfectly poised that a child can move it. The workmen now tilt it and drop in whatever carbon is needed. The molten steel is poured into square moulds, forming masses called "blooms," and is carried away. More iron is put into the converter, and the work begins again.

The Bessemer process makes enormous masses of steel and makes it very cheaply; but it has one fault--it is too quick. The converter roars away for a few minutes, till the carbon and other impurities are burned out; and the men have no control over the operation. In what is called the "open-hearth" process, pig iron, scrap iron, and ore are melted together with whatever other substances may be needed to make the particular kind of steel desired. This process takes much longer than the Bessemer, but it can be controlled. Open-hearth steel is more homogeneous,--that is, more nearly alike all the way through,--and is better for some purposes, while for others the Bessemer is preferred.

Steel is hard and strong, but it has two faults. A steel bar will stand a very heavy blow and not break, but if it is struck gently many thousand times, it sometimes crystallizes and may snap. A steel rail may carry a train for years and then may crystallize and break and cause a wreck. Inventors are at work discovering alloys to prevent this crystallization. The second fault of steel is that it rusts and loses its strength. That is why an iron bridge or fence must be kept painted to protect it from the moisture in the air.

If all the iron that is in use should suddenly disappear, did you ever think what would happen? Houses, churches, skyscrapers, and bridges would fall to the ground. Railroad trains, automobiles, and carriages would become heaps of rubbish. Ships would fall apart and become only scattered planks floating on the surface of the water. Clocks and watches would become empty cases. There would be no machines for manufacturing or for agriculture, not even a spade to dig a garden. Everybody would be out of work. If you wish to see how it would seem, try for an hour to use nothing that is of iron or has been made by using iron.

VIII

OUR GOOD FRIEND COPPER

Where did rocks come from?

Some were deposited in water, like limestone and like the shale and sandstone that lie over the strata of coal. Others were made by fire, and were thrown up in a melted state from the interior of the earth. Such rocks are the Giant's Causeway in Ireland and the Palisades of the Hudson River. They are called "igneous" rocks, from the Latin word _ignis_ meaning "fire."

When the igneous rocks were thrown up to the surface of the earth, they brought various metals with them. How the metals happened to be there ready to be brought up, no one knows. Some people think they were dissolved in water and then deposited; others think that electricity had something to do with their formation. However that may be, metals were brought up with the igneous rocks, and one of these metals is copper.

Now, to one who did not know how to work iron, copper was indeed a wonderful treasure, for it made very good knives and spoons. The people who lived in this country long before the Indians came understood how to use it, and after a while the Indians themselves found out its value. They did not trouble themselves to dig for it; they simply picked it up from the ground, good pure metal in lumps; and with stones for hammers they beat it into knives.

There was only one place in what is now the United States where they could do this, and that was in northern Michigan. A long point of land stretches out into Lake Superior as if it was trying to see what could be found there. Just beyond its reach is Isle Royal; and in these two places there was plenty of copper, enough for the Indians, enough for the people who have come after them, and enough for a great many more. One piece of copper which the Indians did not pick up, and the United States Government did, is the famous Ontonagon Boulder, so called because it was found near the Ontonagon River. It weighs more than three tons. The Indians would have been glad to make use of it, but it was too hard for their tools, and so they are said to have worshiped it as a god. It is now in the National Museum in Washington.

The lumps of copper, such as those which delighted the hearts of the Indians, are known to-day as "barrel" copper, because they are of a good size to be dropped into barrels and carried away for smelting. The great boulders which the Indians could not use are called "mass" copper. Sometimes they weigh as much as five hundred tons. The copper in them is almost pure, and a big boulder is worth perhaps $200,000. Nevertheless, the mine-owners do not rejoice when they come upon such a mass in their digging, for it cannot be either dug or blasted, and has to be cut away with chisels of chilled steel. Now, a mine may be wonderfully rich in metal, but if working it costs too much, then another mine with less metal but more easily worked will pay better. So it is with these great masses of copper. They are interesting to study and they look well in museums, but they do not pay so well as the "stamp" copper which is found in humble little bits in the gangue, or the rock of the vein, and has to be pounded in a stamp mill. This gangue is dug out and broken up as in mines of other metals. The copper is much heavier than the rock, so it is easy to get rid of the worthless gangue by means of a flow of water. The gangue of the Michigan mines is exceedingly hard, but the stamps are so powerful that one can crush five hundred tons in less than twenty-four hours. Some copper can be taken out of the mortars at once, but the rest of the broken gangue is fed to jigs, or screens, which are kept under jets of water. The water is thrown up from below and the lighter rock is tossed away, while the heavier copper falls through the tiny holes in the screens.

The men are pouring hot copper into moulds for castings.]

After the ore has been through all these experiences, it comes out looking like dark-colored sand or coarse brown sugar. It is not interesting, and no one who saw it for the first time would ever fancy that it was going to turn into something beautiful. It is dumped into freight cars and trundled off to the smelting furnaces. But however uninteresting it looks, it is well worth while to follow these cars to see what happens to it at the smelters. First of all, even before it goes into the smelting furnace, it must be roasted. There is usually sulphur combined with the copper, and roasting will get rid of much of it. In some places this is done by building up a great heap of ore with a little wood. The wood is kindled, and by the time it has burned out, the sulphur in the ore has begun to burn, and in a good-sized heap it will continue to burn for perhaps two months.

Such a heap is a good thing to keep away from, for the fumes of sulphur are very disagreeable. Indeed, they will kill trees and other growing things wherever the wind may carry them, even several miles away. The managers of mines of copper as well as of gold and silver have learned to economize; and it has been found that instead of letting these fumes go into the air, they may be made to pass through acid chambers lined with zinc and full of water. The water holds the fumes, and can be used in making sulphuric acid.

After the ore has been roasted, it is put into the furnace for smelting. If you should make an oven and put into it a mixture of wood and roasted copper, that would be a smelting furnace. Set the wood on fire, pump in air to make the flame hot, and if your furnace could be made hot enough,--that is, 2300 deg. F., or about eleven times as hot as boiling water,--you could smelt copper. Of course the furnace of a real smelting factory will hold tons and tons of copper ore and has all sorts of improvements, but after all it is in principle only an oven with wood and ore and draft. Another sort of furnace, which is better for some kinds of ore, has a grate for the fire and a bed above it for the copper.

Imagine an enormous furnace holding between two and three hundred tons of metal and burning with such a terrific heat that by contrast boiling water would seem cool and comfortable. Suddenly, while you stand looking at it, but a long way off, a door flies open and the most beautiful cascade--only it is not a waterfall, but a _copper_ fall--pours out. It looks like red, red gold, rich and wonderful, with little flames of red and blue dancing over it. It might almost be one of the fire-breathing dragons of the old story-books; and if it should get loose, it would devour whomever it touched far quicker than any dragon. It hardly seems as if any one could manage such a monster; but it looks easy, after you have seen it done. An enormous horizontal wheel revolves slowly. On its edge are moulds shaped like bricks, but much larger. On the hub of the wheel a workman sits to direct the filling of these. A set of them is filled, and moves on, and others take their place. When they are partly cooled, another workman, at the farther side of the wheel, pries them out of the mould and drops them into water. Then by the aid of the fingers of a machine and those of men, they are loaded upon cars.

In copper there is often some gold and silver. The precious metals do not make the copper any better, and if they can be separated from it, they are well worth the trouble. This is done by electricity. It is so successful that the metallurgists are hoping soon to take a long step ahead and by means of electricity to produce refined copper directly from the ore. Indeed, this has been done already in the laboratories, but before the managers of mines can employ the method, a way of making it less expensive must be discovered.

No mine that wastes anything is as well managed as it might be; and superintendents are constantly on the watch for cheaper methods and for ways to make the refuse matter of use. Even the scoria, or slag from the furnaces, has been found to be good for something, and now it is made into a coarse sort of brick that for certain rough uses is of value. By the way, the shaft of a copper mine, the Red Jacket, has shown itself of use in a manner that no one expected, namely, it helps to prove that the earth turns around. This shaft is the deepest mining shaft in the world, and when you get into the cage, you go down a full mile toward the center of the earth. If you drop any article into the shaft, it always strikes the east side before reaching the bottom. The only way to explain this is that the earth turns toward the east.

Copper mixed with zinc forms brass, which is harder than copper alone. It tarnishes, though not so easily as copper; but a coat of varnish will protect it till the varnish wears off. A good way to find out the many uses of brass and to see how valuable they are is to go along the street and through a house and make a list. On the street you will see signs, harness buckles, and buttons, everywhere. Look on the automobiles and fire engines for a fine display of brass, polished and shining. In the house you will find brass bedsteads, curtain rods, faucets, pipes, drawerpulls, candlesticks, gas and electric fixtures, lamps, the works of clocks and watches, and scores of other things. You will not have any idea how many they are till you begin to count.

Copper mixed with tin forms bronze. Go into a hardware store and look at the samples of bronze outside of each drawer, and you will be surprised that there are so many. Bronze does not change even when in the open air for ages. That is one reason why it has always been so much used for statues. There are two strange facts about this mixture. One is that bronze is harder than either copper or tin. The other is that if you mix one pint of melted copper with one pint of tin, the mixture will be less than a quart. Just why these things are so, no one is quite certain. Mathematics declares that the whole is equal to the sum of its parts; but in this one case the whole seems to be less than the sum of its parts.

Another reason why bronze is so much used for statues is that the castings are smooth. I once went to a foundry to have a brass ornament shaped somewhat like a cone made for a clock. The foundryman formed a mould in clay and poured the melted brass into it. When it had cooled, the mould was broken off and the ornament taken out; but it was of no use because it was so full of little hollows that it could not be made smooth without cutting away a great deal of it. The man had to try three times before he succeeded in making one that could be polished. If it had been made of bronze, there would have been no trouble, because bronze, hard as it is after it cools, flows when it is melted almost as easily as molasses and fills every little nook and corner of the mould.

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.