Iron

I'urn, a hard, heavy, well known metal. Pure iron is silvery-white in color, but it is seldom seen. Wrought iron is the purest commercial form; yet piano strings, the purest wrought iron in the market, contain three pounds to the thousand of carbon and other elements. When in the presence of a magnet, or when placed within a coil through which an electric current is passing, soft iron becomes magnetic. Iron remains unchanged in dry air, but rusts--unites with oxygen--in moist air.

Iron is the most useful of all metals, and of all metals it is the most widely distributed in nature. It forms a twentieth part of the world's crust. It is essential to life of all sorts. It is found in the green chlorophyll of plants and in the blood of animals. It occurs in meteorites. The color spectrum shows that iron is present in the sun. There is an iron mountain near Durango, Mexico. It is a projecting backbone or dike of solid iron ore,--a huge mass one mile long, a third of a mile wide, and 450 to 650 feet high. Similar hills in Missouri are known as Iron Mountain and Pilot Knob.

Although the world is rich in deposits of iron the supply is by no means inexhaustible. In response to an inquiry instituted in 1905 by the Swedish government as to the world's supply of iron, experts submitted the following report. The figures represent tons of iron ore.

Total 10,000,000,000 100,000,000

In this estimate great possibilities have no doubt been overlooked. Enormous deposits in the Rocky Mountains, in Mexico, in the Andes, in Africa, and doubtless in the Himalayas, are not taken into account, but the fact that the known supply will last only 100 years at the present rate of consumption is enough to make the reader thoughtful.

The American colonists brought articles or iron with them and for a time the smiths imported bar iron. Iron furnaces were set up at an early day, however. Mordecai Lincoln, an ancestor of Abraham Lincoln, established a small furnace at Scituate, Massachusetts. The father of George Washington had a furnace in Virginia. The iron ores of New Jersey have played an important part in the development of the country, but have been neglected of late for ores more easily mined. The region about Pittsburg, Pennsylvania, furnished a large part of the iron consumed in building early American railroads, but iron ore is so abundant and cheap that only the most accessible mines are worked. Of late the material for heavy rails, locomotives, iron bridges, and sky-scrapers has been obtained chiefly from the Alabama and Lake Superior regions.

In the production of iron ore the states of the Union rank as follows: Minnesota, Alabama, Michigan, Pennsylvania, New York, and the Virginias. The sudden advance of Minnesota in iron production is due in part to the remarkable cheapness with which iron in the form of gravel may be obtained in a number of mines northwest of Lake Superior. Much of this gravel lies in hills or open pits accessible by a train of ore cars into which the ore is loaded by steam shovels. Ten shovelfuls load fifty tons into a hopper-bottomed steel car in three minutes. Trains of enormous length descend an easy grade, fifty or 100 miles to Lake Superior, where they run out on elevated ore docks, from the bins of which lake-going boats are loaded for Cleveland and other lake points. The largest ore ship now carries as high as 12,000 tons at a cargo. Ordinarily, iron so far from coal lies undisturbed; but in this case the low cost of mining and transportation proves more than an offset.

Next to the United States comes Great Britain as a producer of iron. An abundance of coal is a factor. The ores of Norway and Sweden are celebrated. Germany ranks third in quantity. Spain has a high record for quality and quantity. Italy and Portugal lack coal with which to develop their large deposits. Newfoundland ships iron ore to Glasgow. Africa, Algeria, and Cuba export iron. Australia and South America have the ore, but as yet depend largely on outside countries for their supply of iron.

Iron ores, however obtained, are first roasted to drive out water and sulphur, and the ore is then reduced in blast furnaces. These are huge fireproof chimneys, twenty-five to ninety feet high. They are filled by dumping in at the top, first a layer of coke, then a layer of iron ore, mixed perhaps with limestone, then coke and iron again, layer after layer, until the furnace is ready to fire. An intense heat melts the iron which sinks in a pool at the bottom of the furnace. When ready, a plug is knocked out and a flood of molten iron pours out into a system of furrows, made ready in a level yard of sand, perhaps an acre in extent. Men wearing wooden shoes work like demons in the heat, seeing first that the iron runs unobstructed and fills the gridiron ditches. As soon as the iron has solidified, and before it hardens, the workmen swing huge sledges and break the still white-hot streams of metal off into pieces not unlike cordwood in length. A supply ditch is called a sow. Many short ditches run out at right angles from the sows and are called pigs, terms suggested doubtless by the appearance of a brood sow suckling a lot of young pigs. The pieces into which the sows and pigs are broken are the pig iron of commerce. Steel, wrought iron, cast iron, malleable iron--iron in whatever form it may enter the endless list of articles made from this metal--are made from pig iron.

In large blast furnaces the process is continuous. The fires never cease to roar. As fast as the mass sinks, ore, limestone, and coke are poured in at the top. The largest have an inside capacity of twenty-five feet. Prehistoric man managed to cobble up a furnace with stones and clay. A modern blast furnace, with blowers to inject air, steam hoists, inclined railroad tracks, and other accessories, is worth half a million dollars, or even twice that sum. A large furnace has a capacity of 600 tons of pig iron a day. Large and small, there are over 400 blast furnaces in the United States. In number of furnaces and the production of pig iron, Pennsylvania, Ohio, Illinois, and Alabama rank in the order named. The United States Steel Trust has recently set up four large blast furnaces at Gary, Indiana, with a capacity of 600,000 tons of pig iron yearly. The ore is obtained in Minnesota.

Pig iron, or cast iron, is too brittle and contains too many other elements to be welded. Wrought iron is obtained from pig iron by smelting in a puddling furnace in which the heat and flame of burning coal remove the foreign ingredients until only six pounds of carbon to the thousand, and slight traces of sulphur, phosphorus, silicon, and manganese are left. Wrought iron may be welded by being heated until it is soft and hammered until the surfaces are brought into actual contact. A sprinkling of borax in the joint helps to clear the surfaces of cinders and to produce perfect adhesion. Wrought iron fuses at 2000 Deg.C.

The chief iron ores are known as hematite and magnetite. Hematite is a compound of iron and oxygen in the proportion of two atoms of iron to three of oxygen. It is of two kinds, red and brown. Red hematite makes a red mark. It gives clay a red color. Bog iron is a form of brown hematite. It makes a brown mark. Magnetite is a harder, blacker, more crystalline ore. It contains more iron. The proportion of atoms is three of iron to four of oxygen. The most noted magnetite ore is the famous Swedish iron. Magnetite makes the finest cutlery. The ores of Alabama and the Superior region are chiefly hematites. Iron pyrites is a compound of iron and sulphur.

The production of iron ore in the United States in long tons was in 1907:

Total 51,720,619

The world's production of pig iron in metric tons in 1908 was:

Total . . . . .47,523,000

In medicine iron is a general tonic. It is acted upon by the gastric juice of the stomach. It gives the blood a healthy red color.

See Steel; Tempering; Razor; Nail