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DURING the Hudson-Fulton celebration of October, 1909, Burgomaster Van Leeuwen, of Amsterdam, member of the delegation sent officially from Holland to escort the Half Moon and participate in the functions of the anniversary, paid a visit to the Edison laboratory at Orange to see the inventor, who may be regarded as pre-eminent among those of Dutch descent in this country. Found, as usual, hard at work--this time on his cement house, of which he showed the iron molds--Edison took occasion to remark that if he had achieved anything worth while, it was due to the obstinacy and pertinacity he had inherited from his forefathers. To which it may be added that not less equally have the nature of inheritance and the quality of atavism been exhibited in his extraordinary predilection for the miller's art. While those Batavian ancestors on the low shores of the Zuyder Zee devoted their energies to grinding grain, he has been not less assiduous than they in reducing the rocks of the earth itself to flour.
Although this phase of Mr. Edison's diverse activities is not as generally known to the world as many others of a more popular character, the milling of low-grade auriferous ores and the magnetic separation of iron ores have been subjects of engrossing interest and study to him for many years. Indeed, his comparatively unknown enterprise of separating magnetically and putting into commercial form low- grade iron ore, as carried on at Edison, New Jersey, proved to be the most colossal experiment that he has ever made.
If a person qualified to judge were asked to answer categorically as to whether or not that enterprise was a failure, he could truthfully answer both yes and no. Yes, in that circumstances over which Mr. Edison had no control compelled the shutting down of the plant at the very moment of success; and no, in that the mechanically successful and commercially practical results obtained, after the exercise of stupendous efforts and the expenditure of a fortune, are so conclusive that they must inevitably be the reliance of many future iron-masters. In other words, Mr. Edison was at least a quarter of a century ahead of the times in the work now to be considered.
Before proceeding to a specific description of this remarkable enterprise, however, let us glance at an early experiment in separating magnetic iron sands on the Atlantic sea-shore: "Some years ago I heard one day that down at Quogue, Long Island, there were immense deposits of black magnetic sand. This would be very valuable if the iron could be separated from the sand. So I went down to Quogue with one of my assistants and saw there for miles large beds of black sand on the beach in layers from one to six inches thick--hundreds of thousands of tons. My first thought was that it would be a very easy matter to concentrate this, and I found I could sell the stuff at a good price. I put up a small plant, but just as I got it started a tremendous storm came up, and every bit of that black sand went out to sea. During the twenty-eight years that have intervened it has never come back." This incident was really the prelude to the development set forth in this chapter.
In the early eighties Edison became familiar with the fact that the Eastern steel trade was suffering a disastrous change, and that business was slowly drifting westward, chiefly by reason of the discovery and opening up of enormous deposits of high-grade iron ore in the upper peninsula of Michigan. This ore could be excavated very cheaply by means of improved mining facilities, and transported at low cost to lake ports. Hence the iron and steel mills east of the Alleghanies--compelled to rely on limited local deposits of Bessemer ore, and upon foreign ores which were constantly rising in value--began to sustain a serious competition with Western mills, even in Eastern markets.
Long before this situation arose, it had been recognized by Eastern iron-masters that sooner or later the deposits of high-grade ore would be exhausted, and, in consequence, there would ensue a compelling necessity to fall back on the low-grade magnetic ores. For many years it had been a much-discussed question how to make these ores available for transporta- tion to distant furnaces. To pay railroad charges on ores carrying perhaps 80 to 90 per cent. of useless material would be prohibitive. Hence the elimination of the worthless "gangue" by concentration of the iron particles associated with it, seemed to be the only solution of the problem.
Many attempts had been made in by-gone days to concentrate the iron in such ores by water processes, but with only a partial degree of success. The impossibility of obtaining a uniform concentrate was a most serious objection, had there not indeed been other difficulties which rendered this method commercially impracticable. It is quite natural, therefore, that the idea of magnetic separation should have occurred to many inventors. Thus we find numerous instances throughout the last century of experiments along this line; and particularly in the last forty or fifty years, during which various attempts have been made by others than Edison to perfect magnetic separation and bring it up to something like commercial practice. At the time he took up the matter, however, no one seems to have realized the full meaning of the tremendous problems involved.
From 1880 to 1885, while still very busy in the development of his electric-light system, Edison found opportunity to plan crushing and separating machinery. His first patent on the subject was applied for and issued early in 1880. He decided, after mature deliberation, that the magnetic separation of low-grade ores on a colossal scale at a low cost was the only practical way of supplying the furnaceman with a high quality of iron ore. It was his opinion that it was cheaper to quarry and concentrate lean ore in a big way than to attempt to mine, under adverse circumstances, limited bodies of high-grade ore. He appreciated fully the serious nature of the gigantic questions involved; and his plans were laid with a view to exercising the utmost economy in the design and operation of the plant in which he contemplated the automatic handling of many thousands of tons of material daily. It may be stated as broadly true that Edison engineered to handle immense masses of stuff automatically, while his predecessors aimed chiefly at close separation.
Reduced to its barest, crudest terms, the proposition of magnetic separation is simplicity itself. A piece of the ore (magnetite) may be reduced to powder and the ore particles separated therefrom by the help of a simple hand magnet. To elucidate the basic principle of Edison's method, let the crushed ore fall in a thin stream past such a magnet. The magnetic particles are attracted out of the straight line of the falling stream, and being heavy, gravitate inwardly and fall to one side of a partition placed below. The non-magnetic gangue descends in a straight line to the other side of the partition. Thus a complete separation is effected.
Simple though the principle appears, it was in its application to vast masses of material and in the solving of great engineering problems connected therewith that Edison's originality made itself manifest in the concentrating works that he established in New Jersey, early in the nineties. Not only did he develop thoroughly the refining of the crushed ore, so that after it had passed the four hundred and eighty magnets in the mill, the concentrates came out finally containing 91 to 93 per cent. of iron oxide, but he also devised collateral machinery, methods and processes all fundamental in their nature. These are too numerous to specify in detail, as they extended throughout the various ramifications of the plant, but the principal ones are worthy of mention, such as:
The giant rolls (for crushing). Intermediate rolls. Three-high rolls. Giant cranes (215 feet long span). Vertical dryer. Belt conveyors. Air separation. Mechanical separation of phosphorus. Briquetting.
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Edison, His Life and Inventions -by- F. L. Dyer and T. C. Martin