of the great mills of the central West, even in the Eastern market, and many mills have ceased to operate. The condition is not a trivial one, for many thousands of persons depend upon these mills and furnaces for a living.
Mr. Edison had familiarized himself with these changing conditions and become impressed that here was a problem that ought to be solved, and perhaps could be. It occurred to him to investigate the mountain regions of New Jersey, where the iron mines are situated, with the idea that there might be some extensive deposits of low-grade magnetic ore not suitable for shipping direct to the furnaces, but from which, by crushing, he might obtain pure ore of high grade and suitable for steel-making. He constructed a very sensitive magnetic needle, which would dip towards the earth whenever brought over a large body of magnetic iron ore. What followed is best reported in his own words.
"One of my laboratory men and myself," says Mr. Edison, "visited nearly all the mines in New Jersey, without finding any deposits of magnitude, but the extent of the deposits was clearly indicated by the needle. One day we were driving across a mountain range to visit an isolated mine shown on the maps of the geological survey. I had the magnetic instrument on my lap, and my mind was drifting away from the subject in hand, when I noticed that the needle was strongly attracted to the earth and remained in this condition over a large area. I thought it must be out of order, as no mines were known to be anywhere near us. We were riding over gneiss rock at the time; so we went down in a limestone valley, where magnetic iron seldom occurs, but we found the needle went back to zero; it was correct. As we returned and traveled over an immense area the needle continued to be pulled strongly to the earth; our amazement grew and grew, and I asked, at last, 'Can this whole mountain be underlaid with magnetic iron ore?' If so, then I knew, if the grade was not too low, the Eastern ore problem might be solved.
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mr. edison's diagram (made for this article) showing the principle of the magnetic separator.
"It was evident from the movement of the needle that vast bodies of magnetic ore, or rock impregnated with ore, lay under our feet.
"I thought of the ill-favored Long Island enterprise, and I knew it was a commercial question to solve the problem of the production of high-grade Bessemer ore in unlimited quantities.
"I determined to find out for myself the exact extent of all the deposits. I planned a great magnetic survey of the East, and it remains, I believe, the most comprehensive of its kind yet performed. I set several corps of men at work surveying the whole strip from Lower Canada to the Great Smoky Mountains of North Carolina. We used no theodolite or other instruments generally familiar to the civil engineer. A magnetic needle was our eye—our magnetic eye, so to speak. Starting in Lower Canada, with our final objective point in North Carolina, we traveled across our line of march twenty-rive miles.
Then we advanced south one thousand feet; then back across the line of march again twenty-five miles; then south another thousand feet, and so on, varying the cross-country marching from two miles to twenty-five, depending on the geological features of the country, as we went along. We kept records of the peculiarities of the invisible mass of magnetite indicated by the movements of our needle, until, when we finished, we knew exactly what State, county, or district had the biggest deposit; how wide, how long, and approximately how deep it all was.
"The deposits are enormous. In 3,000 acres immediately surrounding our mills there are over 200,000,000 tons of low-grade ore; and I have 16,000 acres in which the deposit is proportionately as large. The world's annual output of iron ore at the present time does not reach 60,000,000 tons, and the annual output of the United States is about 15,000,000 tons; so that in the paltry two miles square surrounding the village of Edison there is enough iron ore in the rocks to keep the whole world sup-
