Back Aa

Diggers in the Earth

<hr style="width: 65%;" />[Pg 57] <h2>VII</h2> <h3>IRON, THE EVERYDAY METAL</h3> 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[Pg 58] 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[Pg 59] 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.[Pg 60] 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. [Pg 61] <ANTIMG src="images/image062.jpg" width-obs="368" height-obs="580" alt="IN THE STEEL FOUNDRY" title="IN THE STEEL FOUNDRY" /> IN THE STEEL FOUNDRY 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. [Pg 62] 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[Pg 63] 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[Pg 64] 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. <div style="break-after:column;"></div>

1 of 2

2 of 2

Update Required To play the media you will need to either update your browser to a recent version or update your Flash plugin.