Magnetic Ore Milling Work - 3

Magnetic Ore Milling Work - 3

            A cursory glance at these problems will reveal their import. Mountains must be reduced

to dust; all this dust must be handled in detail, so to speak, and from it must be separated

the fine particles of iron constituting only one-fourth or one-fifth of its mass; and then

this iron-ore dust must be put into such shape that it could be commercially shipped and

used. One of the most interesting and striking investigations made by Edison in this

connection is worthy of note, and may be related in his own words: "I felt certain that

there must be large bodies of magnetite in the East, which if crushed and concentrated

would satisfy the wants of the Eastern furnaces for steel-making. Having determined to

investigate the mountain regions of New Jersey, I constructed a very sensitive magnetic

needle, which would dip toward the earth if brought over any considerable body of

magnetic iron ore. One of my laboratory assistants went out with me and we visited many

of the mines of New Jersey, but did not find deposits of any magnitude. One day,

however, as we drove over a mountain range, not known as iron-bearing land, I was

astonished to find that the needle was strongly attracted and remained so; thus indicating

that the whole mountain was underlaid with vast bodies of magnetic ore.

"I knew it was a commercial problem to produce high-grade Bessemer ore from these

deposits, and took steps to acquire a large amount of the property. I also planned a great

magnetic survey of the East, and I believe it remains the most comprehensive of its kind

yet performed. I had a number of men survey a strip reaching from Lower Canada to

North Carolina. The only instrument we used was the special magnetic needle. We

started in Lower Canada and travelled across the line of march twenty-five miles; then

advanced south one thousand feet; then back across the line of march again twenty-five

miles; then south another thousand feet, across again, and so on. Thus we advanced all

the way to North Carolina, varying our cross-country march from two to twenty-five

miles, according to geological formation. Our magnetic needle indicated the presence and

richness of the invisible deposits of magnetic ore. We kept minute records of these

indications, and when the survey was finished we had exact information of the deposits in

every part of each State we had passed through. We also knew the width, length, and

approximate depth of every one of these deposits, which were enormous.

"The amount of ore disclosed by this survey was simply fabulous. How much so may be

judged from the fact that in the three thousand acres immediately surrounding the mills

that I afterward established at Edison there were over 200,000,000 tons of low- grade ore.

I also secured sixteen thousand acres in which the deposit was proportionately as large.

These few acres alone contained sufficient ore to supply the whole United States iron

trade, including exports, for seventy years."

Given a mountain of rock containing only one-fifth to one-fourth magnetic iron, the

broad problem confronting Edison resolved itself into three distinct parts--first, to tear

down the mountain bodily and grind it to powder; second, to extract from this powder the

particles of iron mingled in its mass; and, third, to accomplish these results at a cost

sufficiently low to give the product a commercial value.

Edison realized from the start that the true solution of this problem lay in the continuous

treatment of the material, with the maximum employment of natural forces and the

minimum of manual labor and generated power. Hence, all his conceptions followed this

general principle so faithfully and completely that we find in the plant embodying his

ideas the forces of momentum and gravity steadily in harness and keeping the traces taut;

while there was no touch of the human hand upon the material from the beginning of the

treatment to its finish--the staff being employed mainly to keep watch on the correct

working of the various processes.

It is hardly necessary to devote space to the beginnings of the enterprise, although they

are full of interest. They served, however, to convince Edison that if he ever expected to

carry out his scheme on the extensive scale planned, he could not depend upon the market

to supply suitable machinery for important operations, but would be obliged to devise and

build it himself. Thus, outside the steam- shovel and such staple items as engines, boilers,

dynamos, and motors, all of the diverse and complex machinery of the entire

concentrating plant, as subsequently completed, was devised by him especially for the

purpose. The necessity for this was due to the many radical variations made from

accepted methods.