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 constitute the principal 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 classed
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 classed 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,
Massachusetts, 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