Report National Conservation Commission.
Reports of Geological Survey.
Conservation of Ores and Related Minerals. (Carnegie.) Report Governor"s Conference.
Conservation of Mineral Resources. (U. S. Government Report.)
Industrial Alcohol and Its Uses. W. H. Wiley. Bulletin, 269.
Production of Peat in the U. S. in 1908. U. S. Government Reports.
Production of Oil in the U. S. in 1908.
Production of Gas in the U. S. in 1908.
Waste of Our Fuel Resources. (White.) Report Governor"s Conference.
CHAPTER VII
IRON
We have already stated the importance of iron in our modern life. It can not be overestimated. All the many articles of iron and steel, our tools, our machinery, our vehicles, our bridges, our steel buildings, and a thousand and one other things are dependent on our iron supply.
Of all the elements that make up the earth"s surface only three are more plentiful than iron, so that we might think that we should always have an abundant supply of it; but when it occurs in small quant.i.ties, as is usually the case, it can not of course be profitably mined. It is only when enough of it is found together to permit it to be mined to advantage that it is called iron ore.
Iron ore is found in only twenty-nine states of the Union, and eighty per cent. of the present production is in two states, Minnesota and Michigan. We can see that iron is very unevenly distributed, and it is on a few regions that we must depend for all the future.
Before we can calculate how much iron we have we must understand that it is not found in pure form, but mixed with various other substances: clay, shale, slate, quartz, sulphur, phosphorus, etc. These must all be removed, some by washing, but most of them by roasting, or "smelting,"
in blast furnaces, after which it is called pig iron. This of course requires large quant.i.ties of fuel.
It is these things and also the position of the ore that must be taken into consideration in estimating the amount of iron in the country. If ore yields a large per cent. of iron in smelting, with a small amount of waste, it is, of course, far more valuable than if the amount of iron in every ton of material taken from the ground is small.
In all minerals, the relation of supply to price is marked. The cost of labor and of power is exactly the same whether ore yields fifty-five tons of pure iron to the hundred, or whether it yields only thirty tons, but the price received is little more than half.
So if the price is low, it may cost more to mine and smelt the one hundred tons of earth than will be paid for the thirty tons of iron that the low-grade ore would yield. So the lands that produce only thirty tons to the hundred will never be mined till the price of iron is so high that it is above the cost of producing--that is, till it can be worked at a profit.
The Lake Superior iron found in Minnesota is usually more than fifty-five per cent. pure iron. That is, if a hundred tons of earth be mined, more than fifty-five tons of pure iron would be obtained from it.
This is the highest grade of ore. Some ore is mined that yields only forty tons or less. There are vast quant.i.ties, billions of tons, of iron ore in the United States, that would yield less than thirty tons of iron to the hundred. These low-grade ores and the ones known to lie so deep in the earth that the cost of mining them is more than the finished products of iron, are cla.s.sed as "not available," that is, they can never be profitably mined under present conditions. But we must remember that as the higher grade ores are exhausted it will become necessary to use the lower grades, and that prices will steadily advance as a result.
Iron is sometimes found almost directly under the ground, at other times deep in the earth. That which is found just below the surface is, of course, mined much more easily, more safely, more cheaply, and with far less loss than that which requires deep mining. Such conditions are found in the Lake Superior region, and there is almost no loss at all, the low-grade ores being piled up at one side where they can be easily reached in case of need.
On the other hand some iron mines now in operation are as much as two thousand feet in depth. In these mines, as in coal mines, pillars are left to support the rock above. A roof of the iron ore is often left also. The low-grade ore is left in the ground and no effort is made to preserve it for future use. These const.i.tute the princ.i.p.al waste in iron mining.
The pure iron of the ore is separated by washing out the clays and soft elements, but the harder substances must be smelted by means of heat. In the beginning this was done by charcoal, which is still used in Sweden.
The latest method is to employ electricity manufactured by water-power, but most of the iron smelting in this country has been done by coal.
Every ton of iron smelted requires its portion of coal for firing. If low-grade fuels in gas-producer engines, or water-power can be used it will be a great aid in conserving coal.
If a limited supply of rather low-grade iron exists near a coal region, it can often be mined profitably, when, if it be far from an abundant fuel supply, it must be shipped to distant blast furnaces. The cost of shipping causes ore containing a small percentage of iron to be cla.s.sed as "not available."
Sometimes a large company with many mines has several varieties of ore of different strength and hardness. If these can be mixed to produce a medium grade by adding a small amount of high-grade ore to a large amount of lower grade, the value of the product will be doubled.
Sometimes, too, the by-products can be made extremely profitable by manufacturing large amounts when the expense of undertaking the work is too great to be attempted with a small amount. So if iron mines are owned by a small company much ore may be cla.s.sed as "not available" that could be used by a large company. All these things must be considered in estimating the iron resources.
The first smelting of iron ore in this country was done at Lynn, Ma.s.sachusetts, in 1645, using the low-grade bog-ores and smelting with charcoal from the surrounding forest.
Now if we look over an iron map of the United States we shall find that there are four hundred and eighty blast furnaces, but that only nine of them are west of the Mississippi River and most of these are in Missouri. The greatest of all the iron regions now lies in upper Michigan and Minnesota. This furnishes eighty tons out of every one hundred mined in the United States, but the smelting is done along the southern sh.o.r.es of Lake Michigan. The reason for this is that the iron region itself is far distant from a cheap fuel supply. Pittsburg, Pennsylvania, has been the great iron city of the United States on account of its nearness to great supplies of both coal and iron.
Birmingham, Alabama, is the heart of the great smelting region of the South.
The iron is divided into districts as follows:
(1) The Northeastern, comprising the states of Vermont, Ma.s.sachusetts, Connecticut, New York, New Jersey, Pennsylvania, Maryland, and Ohio, supplies a little more than five per cent. of the iron mined in the United States.
(2) The Southeastern, containing Virginia, West Virginia, eastern Kentucky, and Tennessee, North and South Carolina, Georgia, and Alabama, gives us twelve per cent. of our iron.
(3) The Lake Superior district, containing the northern parts of Michigan, Minnesota and Wisconsin, supplies more than eighty per cent.
(4) The Mississippi Valley district contains western Kentucky, and Tennessee, Iowa, Missouri, Arkansas and Texas. This region furnishes less than half of one per cent. of the total supply.
(5) The Rocky Mountain district contains Montana, Idaho, Wyoming, Colorado, Utah, Nevada, New Mexico, Arizona, western Texas, Washington, Oregon and California; and all this great region now supplies but a little more than one per cent.
The official report, which is as thorough as can be made but is naturally subject to mistakes, gives the amount of available iron, that is, that which can be mined under present conditions, as nearly five billion tons.
Let us see how long this may be expected to supply the demand.
Before 1810 the amount of iron ore produced was so small as to be scarcely worth considering. From 1810 to 1870 a little less than fifty million tons were mined, from 1870 to 1889 nearly 154,000,000 tons, and from 1889 to 1907, 475,000,000 tons, or altogether nearly 680,000,000 tons. The production has been found to double itself about every nine years. In 1907 alone it was 52,000,000 tons or about one-thirteenth of all that has been mined.
In 1880 we used 200 pounds of pig-iron for every man, woman, and child in the country; in 1890, 320 pounds; in 1900, 390 pounds, and in 1907, 696 pounds. According to the rule of increase, by 1916 we shall be using 104,000,000 tons a year; by 1925, 208,000,000, and by 1934, 416,000,000 tons, and if the same rate of increase should continue, by 1940 we should have required for our use in the meantime, six billion tons. But we have less than five billion tons of what is now cla.s.sed as available ore, which means that before that time (when the school-boys of to-day are business men) we should have exhausted all our good and cheap ore, and be obliged to depend only on the low-grade ores, the cost of which will be very great.
Unlike coal, the forests, and the soil, there is no great and entirely useless waste of iron. But the uses of iron are so many and so varied, and the supply of high-grade ores which can be cheaply mined is so small in proportion to the needs of the future, that we should in all ways lessen the drain on it by subst.i.tuting other cheaper and more plentiful materials when possible.
The chief use of iron is for the carrying of freight. Here are some figures given by Mr. Carnegie. Moving one thousand tons of freight by rail requires an eighty-ton locomotive and twenty-five twenty-ton steel cars, or five hundred and eighty tons of iron and steel to draw it over--say an average of ten miles of double track with switches, frogs, spikes, etc., which will weigh more than four hundred tons. Thus we see that to move a thousand tons of freight requires the use of an equal weight of iron. The same freight may be moved by water by means of from one hundred to two hundred and fifty tons of metal, so that if freight were sent by water instead of by rail the amount of iron needed for this service would be reduced at least three-fourths, the amount of coal would be reduced not less than half, and at the same time the coal used in extra smelting would be saved. No single step open to us to-day would do more to check the drain on both iron and coal than the use of our rivers for carrying heavy freight.
The next great use of iron is for buildings and bridges. The greatly increasing use of cement and concrete is reducing this and will reduce it still further. Cement is made from slag, or the refuse of iron ore--the clays and shales--and the cost of this valuable product is little more than the former cost of piling it away. By making the useless slag into cement the cost of iron production is lowered and at the same time the drain on the iron is lessened.
A large use of steel of the highest quality is for battleships, cannon, and war supplies. If the great nations of the world would agree to reduce their armament, one of the great drains on the world"s iron, coal, and wood supply would cease, and these materials be put to improving the world.
The worst feature of it is that these war supplies are continually changing. They must be of the latest pattern, or they are of small value for fighting purposes. The construction of battleships differs greatly year by year, and the older ships are discarded to make place for newer and larger ones. It is said that our newest battleship alone could with a few shots destroy all of Admiral Dewey"s fleet. The following is from a recent magazine article:
"It is admitted by naval officers that the ships of ten years ago are of obsolete type and would be useless against the new vessels. It is admitted that within ten years or less the new types will in turn become obsolete, and will be useless against the type of vessel certain to be evolved. That is, as soon as a vessel costing millions of dollars leaves the docks, she enters into active compet.i.tion for a place on the junk pile."
The greatest improvement that can be imagined in the iron situation will be in the discovery and use of alloys or mixtures of iron with other materials. Steel, the strongest of all forms of iron, is an alloy of iron and carbon, and for various purposes these are further mixed with nickel and silicas. Many other alloys have been discovered within the last few years, and each makes possible new uses for iron requiring greater strength. One of the best of these is a mixture of iron and silicon, called ferro-silicon. Silica is one of the cheapest and most abundant materials of all the earth"s products, so its combination with iron will greatly lengthen the life of the iron supply; and it is probable that in the future combinations of other materials will yield better and cheaper metals than any thus far produced.
The amount of metal which can be reworked is constantly increasing. Most of the iron factories remelt large quant.i.ties of old iron, to be used with the new, and this will lessen each year the demand on the ores. It is also possible that new deposits of iron ore will be found and these will greatly increase the supply. But from the whole iron situation we may draw the following conclusions: