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 sta