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," fromcarat, an old weight equal to one twenty-fourth of anounce 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.
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 onespecial 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 districtaround 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.
THE STORY OF A SPOONTHE STORY OF A SPOONCourtesy 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 anymoment 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 readyto 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 theylaid 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."
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 thecrust 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, meteoritesare 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.
IN THE STEEL FOUNDRYIN THE STEEL FOUNDRYIt 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; andthis 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 orfence 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.
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 wordignismeaning "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 inlumps; 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.
IN A COPPER SMELTERIN A COPPER SMELTERThe 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° 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 isbetter 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 acopperfall—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 soonto 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 greatdeal 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.
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 IndependenceHall, 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. Electricpower, 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.
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 throughthe 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.
A "MOVIE" OF AN ALUMINUM FUNNELA "MOVIE" OF AN ALUMINUM FUNNELCourtesy The Aluminum Cooking Utensil Company.Seventeen other operations are necessary after the thirteenth stamping operation before the funnel is ready to be sold. And after all this work, we can buy it for 35 cents at any hardware store.
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. Automobilesin 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, andthe 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.
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 ispiped 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 someland 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,—